Gastro-intestinal System Flashcards

Question

A 70-year-old man with a history of several months of dysphagia undergoes double-contrast barium swallow. This demonstrates a moderately dilated oesophagus with reduced peristalsis and smooth tapering of the distal oesophagus. What is the most likely diagnosis? [B4 Q19] a. primary achalasia b. gastric carcinoma c. scleroderma d. oesophageal carcinoma e. presbyoesophagus

Answer 1

**Gastric carcinoma** Primary achalasia is an abnormality of the myenteric plexus resulting in reduced or absent peristalsis and failure of relaxation of the lower oesophageal sphincter. The oesophagus is typically markedly dilated with absent primary peristalsis and a smooth tapered narrowing at the contracted lower oesophageal sphincter. It usually presents in young adults with long- standing dysphagia. In contrast, **secondary achalasia** due to malignancy usually presents in **older patients** with a short duration of dysphagia. Decreased peristalsis and distal oesophageal tapering in these patients result from **tumour inﬁltration of the myenteric plexus of the distal oesophagus by gastric carcinoma**, lymphoma, or metastatic disease. Distal oesophageal carcinoma tends to give rise to irregular, asymmetrical narrowing. Scleroderma typically appears as a dilated oesophagus with a patulous lower oesophageal sphincter. Presbyoesophagus is a disorder of oesophageal motility, characterized by oesophageal dilatation and repetitive, non-peristaltic, tertiary contractions in the distal oesophagus.

Answer 2

**Intramural haematoma of the oesophagus** Submucosal dissection of the oesophagus may be spontaneous or secondary to direct trauma or coagulopathy. Patients may present with chest pain, dysphagia, and nausea, often followed by haematemesis. The high attenuation in the wall of the oesophagus is the clue to the diagnosis. This feature and lack of enhancement are inconsistent with any alternative diagnosis. Follow- up with endoscopy is usually performed to exclude a predisposing pathological condition. The natural history is complete resolution without surgical intervention.

Answer 3

**Mucosal tears from Mallory-Weiss syndrome** or post endoscopy are typically in the lower 1/3 of the oesophagus.

Answer 4

**Spontanous oesophageal rupture** Iatrogenic injury is the most common cause of oesophageal rupture, but, in 15% of cases, rupture is spontaneous and occurs during vomiting (Boerhaave’s syndrome). Patients present with pain and dysphagia, and rapidly develop sepsis. Characteristic chest radiograph ﬁndings are of extensive pneumomediastinum and subcutaneous emphysema, pleural effusion or hydropneumothorax, and left lower lobe atelectasis. Widening of the mediastinum may accompany the development of mediastinitis. Pleural effusion and atelectasis may be seen in acute pulmonary embolism, acute pancreatitis, and aortic dissection, but pneumomediastinum is not a recognized feature of these conditions. Other common causes of pneumomediastinum include asthma, chest trauma and perforation of a hollow viscus with extension of gas via the retroperitoneum.

Answer 5

**LAO**: Lesser curvature. RAO: Body and Antrum. Supine: Greater curve and Antrum. Left lateral: Fundus.

Answer 6

**Gastrograﬁn can be added to improve transit time** Simethicone is an antifoaming agent. While a uniform particle size helps reduce ﬂocculation, a heterogeneous particle size improves mucosal coating. The barium densities used for different examinations are barium swallow 150%, barium meal 250%, barium follow-through 50%, barium small bowel enteroclysis 18%, double-contrast barium enema 125%, and single- contrast barium enema 70%.

Answer 7

**300 ml of 100% w/v barium sulphate** The recommended contrast is 300ml of 100% w/v barium sulphate. Transit time may be reduced by the addition of 10ml of Gastrograﬁn to the barium. Non-ionic, water-soluble contrast media may be used as an alternative where barium is contraindicated. The recommended concentrations and volumes for the other gastrointestinal contrast examinations are barium swallow (a), barium meal (b), small bowel enema (d) and double-contrast barium enema (e).

Answer 8

**Pyloric muscle wall thickness of 2 mm** Hypertrophic pyloric stenosis presents between four and six weeks of life with non-bilious vomiting, typically in first-born males. A **palpable olive-shaped mass** is a sign with reported sensitivity of up to 80%, but ultrasound is the most frequently used imaging modality. Typical ultrasound features include the target sign (central hyperechoic mucosa with surrounding hypoechoic pyloric muscle), the nipple sign (pyloric mucosa indenting the gastric antrum), pyloric canal length > 16 mm, transverse pyloric diameter >13 mm and pyloric muscle wall thickness > 3 mm. Pyloric stenosis can be difficult to differentiate radiologically from infantile pyloro-spasm. Typically, with pyloro-spasm the appearances change with time, and so if the pyloric muscle thickness is measured at less than 3 mm this makes infantile pyloro-spasm the more likely diagnosis. ## Footnote Hypertrophic Pyloric Stenosis [STATdx] * Idiopathic pyloric muscle thickening in young infants causing progressive gastric outlet obstruction * Near-complete gastric outlet obstruction due to abnormally elongated & thickened pyloric muscle * Pathology * Idiopathic, prostaglandin or erythromycin induced, neural mediated, familial * Tends to run in families. * Clinical Features * 2-12 weeks old, progressive, nonbilious projectile vomiting * Feedings previously tolerated * Male preponderance, common * Gastroesophageal reflux > > HPS * Ultrasound * Hypertrophied circumferential hypoechoic muscle & elongated pyloric canal filled with echogenic mucosa * Pyloric channel length > 15-16 mm * Single wall thickness of pyloric muscle > 3 mm * Failure of thickened pylorus to change during exam in contrast to pylorospasm. * Fluoroscopy * Minimal barium traversing narrowed & elongated pyloric channel * Mass effect on gastric antrum & duodenum by hypertrophied muscle, hyperperistaltic gastric contractions, and * Gastroesophageal reflux/emesis * HPS in 1/5 of infants imaged for vomiting

Answer 9

**Body and antrum of the stomach** The stomach is divided into the fundus, body, antrum, and pylorus. The fundus is that part of the stomach extending superiorly and to the left of the cardiac oriﬁce. The body extends from the cardiac oriﬁce to the incisura angularis, which is a constant notch at the lower end of the lesser curvature marking the border between the body and the antrum of the stomach. The antrum extends from the incisura angularis to the proximal pylorus.

Answer 10

**Left renal vein** Ultrasound scan of the pancreas may be difﬁcult and vascular landmarks are important in its identiﬁcation. In the transverse plane, the splenic vein can be seen coursing from the splenic hilum towards the liver, and the body and tail of the pancreas lie immediately anterior to this. The neck of the pancreas lies immediately anterior to the conﬂuence of the splenic and superior mesenteric veins, and the head and uncinate process of the pancreas lie around this conﬂuence, anterior to the inferior vena cava. At this level, the left renal vein can be seen entering the inferior vena cava, passing between the superior mesenteric artery and aorta

Answer 11

**Menetrier’s disease** Menetrier’s disease is a condition characterised by **gastric mucosal hypertrophy and protein- losing enteropathy.** It is often associated with anaemia. The changes are most marked along the greater curve and the **antrum is spared** in approximately 50% of cases. Gastric lymphoma typically involves the antrum. Gastric adenocarcinoma and linitis plastica, stomach distension is not typically preserved.

Answer 12

**Menetrier’s disease** Meneterier’s disease is characterized by mucosal hypertrophy of the fundus and body of the stomach, with excessive mucus secretion and a protein-losing enteropathy. There may be associated gastric ulceration. Barium meal shows impaired mucosal coating due to hypersecretion and marked gastric fold thickening, though the stomach distends normally. The stomach is the commonest site for gastrointestinal lymphoma, which may be polypoid, ulcerating or inﬁltrative. The inﬁltrative form may cause pronounced thickening of gastric folds, with preserved stomach distensibility, but hypersecretion is not a feature. Inﬁltrating gastric carcinoma may also cause thickened gastric folds, but associated desmoplastic reaction results in a rigid, poorly distensible stomach. Zollinger–Ellison syndrome results in hypersecretion of gastric acid which impairs mucosal coating of barium and is associated with ulceration and enlargement of rugal folds, but hypoproteinaemia is not a feature. Eosinophilic gastroenteritis may cause enlarged gastric folds and be associated with protein-losing enteropathy if the small bowel is involved. However, the antrum is most involved.

Answer 13

**Phytobezoar** Bezoars are masses of accumulated ingested material forming in the stomach or intestines. Phytobezoars are the commonest type, composed of poorly digested ﬁbre and vegetable matter. They are seen particularly in patients with previous gastric surgery, probably due to diminished gastric emptying. Patients may be asymptomatic or present with early satiety or symptoms of gastritis, as phytobezoars are irritant. Occasionally, they may obstruct the stomach with a ball– valve mechanism. They are seen as relatively mobile ﬁlling defects, the interstices of which are ﬁlled with barium. Trichobezoars are composed of hair, and are usually larger, and found in younger patients, particularly those with a psychiatric history. Gastric carcinoma, villous adenoma and suture granuloma are all causes of gastric ﬁlling defects but have a constant relationship to the gastric wall

Answer 14

**GIST** Gastrointestinal stromal tumours are the commonest mesenchymal tumours of the gastrointestinal tract. They are characterized by expression of KIT, a tyrosine kinase growth factor receptor, which distinguishes them from leiomyomas and leiomyosarcomas. They **occur most commonly in the stomach** and have the classic appearance of a submucosal mass on barium meal, forming an obtuse angle with the gastric wall in proﬁle. Focal areas of ulceration are seen in 60%. On CT, the tumours measure up to 30 cm and are often **predominantly extra-gastric**. Typical features are of peripheral enhancement, with **central low attenuation representing necrosis**, haemorrhage, and cyst formation. **NO Lymphadenopathy**. Gastric carcinoma and lymphoma rarely demonstrate exophytic growth and commonly have associated lymphadenopathy. Adenomatous polyps are mucosal lesions. Gastric carcinoid is usually seen in the antrum and characteristically shows associated ulceration.

Answer 15

**Preservation of the fat plane around the stomach**, diffuse and homogenous wall thickening, multifocal disease within the stomach, nodal disease either side of the mesenteric vessels, **nodal disease extending** below the level of the renal veins and a propensity for the distal half of the stomach are all features of gastric lymphoma.

Answer 16

**Central fluid attenuation/ necrosis is common** Stomach GISTs tend to present in patients over 50. CT usually shows a well-defined heterogeneously enhancing, round, exophytic mass, commonly with central necrosis. Mural calcification is recognised but not common. Stomach GISTs tend to be less aggressive histologically than GISTs at other sites.

Answer 17

**Multiple submucosal nodules with central ulceration** GI tract metastases are seen in 4–8% of patients with malignant melanoma. The small intestine is most affected, followed by the colon and stomach. Typical features are of multiple submucosal nodules, with a target appearance due to central ulceration. This appearance is particularly seen with malignant melanoma metastases but may also be seen with gastric metastases from breast, lung, and renal cell carcinoma. Other common appearances of gastric metastases include linitis plastica in 20%, most typically from breast cancer, and a solitary mass in 50%.

Answer 18

**T3 N2 M0** T3 tumours penetrate the subserosa but do not invade adjacent structures. On CT, this may be appreciated as blurring of the tumour margin or wide reticular strands radiating from the tumour edge. Nodal staging depends on the number of regional nodes visible, with nodes larger than 8mm being regarded as pathological. The presence of 1–6 regional nodes results in a stage of N1, with 7–15 nodes and >15 nodes representing nodal stages of N2 and N3 respectively. Non-regional nodes such as para-aortic and retro-pancreatic nodes are considered M1 disease

Answer 19

**Acute gastric volvulus** Acute gastric volvulus is abnormal rotation of one part of the stomach around another part, which may be classiﬁed as organoaxial, mesenteroaxial or combination type, depending on the axis of rotation. Predisposing factors include ligamentous laxity, hiatus hernia and diaphragmatic eventration. The classic presentation is with the Borchardt triad of sudden severe epigastric pain, intractable retching with no vomitus produced, and inability to pass a nasogastric tube into the stomach. Other plain ﬁlm ﬁndings include unexpected location of the gastric bubble and air–ﬂuid levels in the mediastinum or upper abdomen, but deﬁnitive diagnosis is by barium meal. The condition is a surgical emergency, as it may result in gastric ischaemia or perforation. Acute gastric dilatation and pyloric stenosis may result in gastric distension on plain ﬁlm but would not present with intractable retching or difﬁculty with nasogastric tube passage. A ‘cup-and-spill’ stomach is an anatomical variant on barium meal, which may simulate an organoaxial volvulus. A para-duodenal hernia usually presents acutely as small bowel obstruction. ## Footnote Gastric Volvulus [Radiopaedia] Case courtesy of Dr Maxime St-Amant, Radiopaedia.org, rID: 19

Answer 20

**Benign due to the line noted crossing the base of the ulcer - Hampton's line** This line—Hampton’s line—represents undermining of the mucosa by the more vulnerable submucosa. It is not commonly seen but is taken to be virtually diagnostic of a benign ulcer when present. Projection beyond the lumen and a symmetrical mound are features of a benign ulcer along with smooth radiating mucosal folds. Scar retraction can be seen with benign ulcers. Both benign and malignant ulcers are more commonly seen on the lesser curve. ## Footnote Benign Vs Malignant Ulcers [Core Radiology] **Benign** gastric ulcer o Radiating gastric folds are **smooth and symmetric** o Ulcer extends beyond the normal contour of the gastric lumen. o The **Hampton line** represents nonulcerated acid-resistant mucosa surrounding the ulcer crater. o Most benign ulcers occur along the lesser curvature of the stomach, although benign ulcers associated with aspirin ingestion can occur in the greater curvature and antrum, which are dependent locations. **Malignant** o **Asymmetric ulcer crater**, with **surrounding nodular tissue** o Abrupt transition between normal gastric wall and surrounding tissue. o **Ulcer crater does not project beyond** the expected location of gastric **wall**. o The **Carman meniscus** sign is considered pathognomonic for tumour. It describes the **splaying open of a large, flat malignant ulcer when compression is applied**.

Answer 21

**Ulcer crater confined within gastric contour** Many distinguishing features of gastric ulceration have been proposed to classify gastric ulcers as benign or malignant, but there is signiﬁcant overlap between the two categories. One reliable sign of a benign ulcer is the projection of the ulcer outside the gastric contour in proﬁle, due to excavation into the mucosal wall. In contrast, a malignant ulcer occurring within a tumour mass does not usually extend beyond the conﬁnes of the gastric wall. Other features indicative of benignity include a round, centrally located ulcer with a uniform collar of oedematous mucosa, gastric folds extending to the edge of the ulcer crater and associated duodenal ulcer disease.

Answer 22

**Leakage from the duodenal stump.** There is no gastro-duodenal anastomosis in a Billroth II procedure. The amylase is not sufﬁciently elevated for pancreatitis in most cases and there is no described abnormality in the pancreas. It is too early for pseudocyst formation and tumour recurrence. ## Footnote Different Surgeries for Peptic Ulcer Disease 1. Billroth I partial gastrectomy – Seldom performed * Distal gastrectomy * Gastro-duodenal anastomosis (proximal stomach to D1) 2. Billroth II/ Polya partial gastrectomy * Distal gastrectomy * Closure of duodenal stump * Gastro-jejunal anastomosis (retro or antecolic, iso or anti-peristaltic direction) 3. Subtotal gastrectomy with Roux Loop reconstruction * Distal gastrectomy * Closure of duodenal stump * Continuity is restored with a Roux loop reconstruction 4. Total gastrectomy (in Ca stomach) * Total gastrectomy with lymphadenectomy * Duodenal stump is stapled or over sewn * A Roux loop is anastomosed to distal oesophagus (end to side) with blind limb * Jejuno-jujunal anastomosis 50-60 cm distal to oesophago-jejunal anastomosis 5. Truncal vagotomy 6. Wedge Resection 7. Gastro-enterostomy (to overcome the GOO) Side to side gastro-jejunal anastomosis No Roux loop → increased risk of bile gastritis and associated stomach cancer. Post-operative Complications 1. Anastomotic leak * Most serious, highest after total gastrectomy * Extra-luminal contrast leak, duodenal stump is not usually evaluated in Ba study * Disproportionate pneumoperitoneum * Collections in unusual place (left subphrenic space) as anatomy is disrupted 2. Duodenal stump leak * Right subhepatic space fluid collection, can be precipitated by afferent loop obstruction * Disruption of duodenal stump metal staple line 3. Afferent Loop Obstruction/Syndrome * Associated with Billroth II gastrectomy and gastrojejunostomy * Adhesion or twisting of the bowel proximal to gastroenterostomy site * Acute obstruction can lead to duodenal stump blow out * Risks – long afferent limb (>30-40 cm), antecolic gastrojejunostomy. * Ba study is of limited value, as doesn’t normally fill the afferent limb * CT → fluid filled dilated afferent limb with associated biliary dilatation 4. Anastomotic stricture 5. Parastomal jejunal ulcer * Common after Billroth II as gastric acid goes into jejunum. * Very rarely, can lead to gastro-jejuno-colic fistula. 6. Gastric Remnant Complications * Bile reflux gastritis – Billroth I and II * Gastroparesis * B12 deficiency * Gastric remnant malignancy – commonest at the anastomosis 7. Efferent Complications * Obstruction secondary to adhesions, local recurrence, intussusception or internal hernia. * Hiatus hernia * Early dumping syndrome secondary to rapid fluid shift. * Late dumping syndrome secondary to rapid CHO absorption.

Answer 23

**Incidence of SBO secondary to internal lesions 0.2-5.0 %** Hernia more common in laparoscopic approaches occur in the mesocolic, Peterson’s and meso- mesenteric defects. Obstruction commonly occurs in the afferent (biliopancreatic) limb causing distension of the very proximal jejunum, duodenum, and remnant stomach. Remnant stomach should be relatively decompressed.

Answer 24

**Is connected by tubing to a port anterior to the rectus sheath** Band should be perpendicular to GOJ on scout film. Position is best assessed straight AP or slightly RPO. Band slipping leads to eccentric pouch dilation. Perforation typically <0.5%

Answer 25

**Nutritional advice** Laparoscopic gastric banding involves laparoscopic placement of an inﬂatable gastric band across the proximal stomach, forming a small fundal neo-stomach or pouch. The band is connected to a subcutaneous port that can be accessed percutaneously to allow inﬂation or deﬂation of the band and adjustment of stomal width and degree of hold-up. The commonest postoperative complication is dilatation of the pouch. Three main types are described. (1) Acute concentric pouch dilatation is due to band overinﬂation and is seen as a pre-stenotic dilatation proximal to an obstructed stoma. It presents as acute dysphagia and requires prompt decompression of the stoma. (2) Chronic **concentric pouch dilatation** with a widely patent stoma is seen in patients who continue to overﬁll their neo-stomach after surgery. **Nutritional advice** is required. (3) **Eccentric pouch dilatation** occurs due to slippage of the band and requires complete **decompression and surgical replacement** of the band. A plateau in weight loss may also be due to loss of effect of band tightening. At ﬂuoroscopy, ﬂuid may be injected to tighten the band to achieve an optimal stomal width of 3–4mm.

Answer 26

**Small bowel mural hyper-density is a feature and is due to vasodilatation seen in early ischaemia.** Multi-detector CT (MDCT) has been found to correlate with pathological processes in small bowel obstruction. The earliest appearance is increased mural density due to hyperaemia. Wall thickening is due to increasing capillary permeability, which causes submucosal oedema. Dilatation is secondary to oedema that limits peristalsis. Lack of enhancement occurs when the bowel dilates and compresses the capillary bed. Pneumatosis is secondary to mucosal ischaemic change, which allows luminal air to track into the wall. Lack of enhancement is also seen in embolic ischaemia but is not a speciﬁc sign of this process. Whilst oral contrast is preferred in many centres, as it can help deﬁne if complete obstruction is present, it is not mandatory. Some centres prefer the negative contrast provided by the ﬂuid in the bowel lumen. Patients with small bowel obstruction are also often unable to tolerate oral contrast due to vomiting.

Answer 27

**Superior mesenteric artery syndrome** The third part of the duodenum is bounded posteriorly by the aorta, and anteriorly by the root of the mesentery carrying the superior mesenteric artery. In superior mesenteric artery syndrome, the third part of the duodenum is compressed by the superior mesenteric artery, and the angle between it and the aorta narrows to 10–22 (normal 45–65 ). The condition is associated with severe weight loss, prolonged bedrest (particularly in a body cast), lumbar lordosis and pregnancy. Patients report intermittent abdominal pain and vomiting, relieved by lying prone or in the knee–elbow position. Duodenal atresia causes complete obstruction usually distal to the ampulla of Vater and presents in neonates with a ‘double-bubble’ sign on plain abdominal radiograph. Annular pancreas is usually asymptomatic but may present with abdominal pain and vomiting, and barium meal demonstrates narrowing of the second part of the duodenum. Duodenal duplication cysts cause extrinsic compression of the ﬁrst and second portions of the duodenum. Ladd’s bands are congenital peritoneal bands occurring in association with malrotation that may cause obstruction of the second part of the duodenum, but presentation is usually in infants and children.

Answer 28

**Cholecysto-duodenal fistula** The other answers are all causes of portal air, whereas the salient description is for air in the biliary tree.

Answer 29

**Trans-mesenteric hernia** This is when small bowel herniates through a defect in the mesentery and is compressed against the abdominal wall, with little overlying omental fat at most levels of anatomic section through the herniated bowel. There will be some degree of compression, crowding, displacement, and obstruction of both the bowel and blood vessels. They are usually seen in association with previous abdominal surgery and the creation of a Roux-en-Y anastomosis when the hernia occurs in a surgically created defect in the mesentery. A left-sided paraduodenal hernia is via the paraduodenal (lateral to the fourth part) mesenteric fossa of Landzert, close to the ligament of Treitz. The characteristic features include a sac-like mass of dilated bowel lateral to the ligament of Treitz, which displaces and indents the adjacent stomach and transverse colon. A right paraduodenal hernia occurs via the jejunal mesentericoparietal fossa of Waldeyer. A cluster of dilated small bowel loops is seen lateral and inferior to the descending duodenum.

Answer 30

**Presence of haustral markings** Sigmoid and caecal volvulus can sometimes be difficult to differentiate on plain abdominal film. With caecal volvulus the haustral markings are typically present, whereas these are usually absent in sigmoid volvulus. The pelvic overlap, liver overlap and coffee bean signs are typical of sigmoid volvulus. In sigmoid volvulus the apex lies high in the abdomen underneath the left hemi-diaphragm, typically above the level of T10. ## Footnote Signs associated with Sigmoid Volvulus [My note] Coffee Bean Sign Pelvic Overlap Sign Liver Overlap Sign Northern Exposure Sign Loss of Haustration

Answer 31

**Sigmoid volvulus** Sigmoid volvulus usually occurs when the sigmoid loop twists around its mesenteric axis, creating a closed loop obstruction. Typical features are of an inverted U-shaped loop converging on the left side of the pelvis. The bowel loop is usually markedly distended, appears ahaustral, and may overlap the lower border of the liver (liver overlap sign) or the haustrated dilated descending colon (left ﬂank overlap sign). The apex of the volvulus usually lies under the left hemidiaphram with its apex above the level of T10. Caecal volvulus occurs when the caecum is on a mesentery and involves the caecum either twisting and inverting so the caecal pole lies in the left upper quadrant or twisting in an axial plane so that the caecum remains right sided or central. Appearances are of a large, gas-distended viscus, usually with haustral markings, and occasionally the gas-ﬁlled appendix may be identiﬁed.

Answer 32

**Small bowel enteroclysis** Small bowel enteroclysis is the most appropriate examination. CT is sensitive for high-grade obstruction as it will readily identify the level of obstruction and can demonstrate complications such as ischaemia and perforation. Enteroclysis is the preferred investigation for recurrent low-grade obstruction as it is more likely to demonstrate the presence of a transition point (for example from non-obstructing adhesions) because the bowel is distended. The examination involves passing a nasojejunal tube just distal to the duodenojejunal flexure and distending the small bowel using either dilute barium or a double-contrast examination with high-density barium and methylcellulose.

Answer 33

**Gallstone ileus** Specific signs of gallstone ileus can be seen on the plain abdominal film in up to 40% of patients. Fifty per cent of patients have evidence of small bowel obstruction and up to 30% have gas in the biliary tree. Biliary tree gas is typically more prominent centrally and spares the periphery of the liver, whereas portal venous gas is more easily visualised in the periphery of the liver, which may be associated with small bowel infarction. The gallstone most frequently lodges in the terminal ileum but is often not seen on the plain film. The presence of small bowel obstruction, pneumobilia and a visible stone are called Rigler’s triad.

Answer 34

B-D occur < 12 months, whereas internal hernias and meso-colic constriction of the Roux limb are more chronic complications. Chronic complications with obstruction at the biliopancreatic limb, internal hernias and anastomotic strictures at the common channel are internal hernias and adhesions.

Answer 35

**Femoral hernia** External hernias are the second most common cause of small bowel obstruction after adhesions. A femoral hernia protrudes through the femoral ring, lying medial to the femoral vein, which may be compressed. On CT the hernia is seen inferolateral to the pubic tubercle, in contrast to inguinal hernias, which usually lie superomedial to the tubercle, though differentiation may be difﬁcult in non-incarcerated cases. Femoral hernias are more prone to incarceration due to the inﬂexible margins of the femoral ring. Inguinal hernias may be classiﬁed as indirect (passing down the inguinal canal, seen lateral to the inferior epigastric vessels) or direct (protruding directly through the lower abdominal wall medial to the inferior epigastric vessels). A spigelian hernia protrudes through a defect in the inferolateral anterior abdominal wall. Obturator hernias protrude through the obturator foramen, between the pectineus and external obturator muscles.

Answer 36

**Terminal ileum** Gallstone ileus accounts for up to 5% of intestinal obstruction, increasing in prevalence with age. It involves erosion of a large gallstone from the gallbladder or common bile duct into the bowel, which goes on to cause obstruction. The classic appearance on plain ﬁlm (Rigler’s triad) is only seen in 10% of cases and consists of partial or complete intestinal obstruction (usually small bowel), gas in the biliary tree and an ectopic calciﬁed gallstone. The most common site of ﬁstulous communication is between the gallbladder and the duodenum, seen in 60%, and this may be demonstrated on barium meal as a contrast collection lateral to the ﬁrst part of the duodenum representing barium within the gallbladder. Fistulas occur less commonly between the common bile duct and duodenum, gallbladder and colon. The ectopic gallstone most often causes obstruction at the terminal ileum (60–70%), followed by the proximal ileum, distal ileum, pylorus, sigmoid and duodenum.

Answer 37

**Crohn’s disease** The ﬁndings described are classical for Crohn’s disease and lymphadenopathy is seen in up to 30% of cases. Tuberculosis more typically involves the caecum. Lymphoma usually causes a nodular appearance to the bowel. It is not associated with stricturing of the affected segment and is more classically associated with dilatation of the affected segment due to destruction of the myenteric plexus.

Answer 38

**Mucosal hyperenhancement** The lack of ionizing radiation is a major advantage to MRI for patients with Crohn’s disease given the chronic nature of this condition necessitating frequent investigation. MRI can be performed via enterography or enteroclysis. In enterography, large volumes of ﬂuid (or a ﬂuid inducing laxative) are ingested. Enteroclysis involves administration of enteric contrast material via a naso-enteric tube. Sequence acquisition involves fat suppression and intravenous contrast. Increased mucosal hyperenhancement (compared with that seen in normal surrounding loops) may be the earliest sign of active inﬂammation, even in the absence of wall thickening. Increased vascularity, peri-enteric inﬂammation, and reactive adenopathy are other signs of active Crohn’s disease. In severe Crohn’s disease mucosal hyperenhancement combined with submucosal oedema gives a ‘stratiﬁed’ appearance. Serosal hyperenhancement may also be seen, giving a ‘target’ appearance. Mural thickening is deﬁned as greater than 3 mm, although an under-distended bowel may mimic this ﬁnding.

Answer 39

**Fibro fatty mesenteric proliferation** around involved colon is more likely to indicate Crohn’s disease.

Answer 40

**Pneumatosis intestinalis** The stacked coin appearance is seen secondary to intramural haemorrhage—the appearances of systemic sclerosis are of tightly packed folds of normal thickness in a dilated portion of bowel, which has been given the title ‘accordion’ or ‘hidebound’ bowel. The pseudo-diverticula (10–40%) are seen on the mesenteric side of the bowel, unlike colonic diverticula. The transit time is prolonged, as there is reduced intestinal motility. Another classical feature is of a markedly dilated duodenum, due to the loss of the enteric innervations—mega duodenum. This classically terminates abruptly at the level of the superior mesenteric artery (SMA). Pneumatosis cystoides can occur in systemic sclerosis of the small bowel. Small bowel disease is seen in up to 40% of patients with systemic sclerosis and indicates rapidly progressing disease. ## Footnote Scleroderma [Core Radiology] * Def: a systemic disease characterized by the deposition of collagen into multiple internal organs and the skin. * Replacement of the muscular layers with collagen, resulting in * Slowed transit * Bacterial overgrowth * Progressive dilatation * Radiographically * Sacculation on the antimesenteric border * Hidebound Bowel – thin, straight bowel fold stacked together. Intestinal Scleroderma [STATdx] * Progressive systemic sclerosis * GI tract: Most common internal organ system involvement (80-90%) o Oesophagus > duodenum > anorectal > small bowel > colon * Oesophagus o Atony or aperistalsis (lower 2/3 smooth muscle) o Mild to moderate dilatation o Patulous lower oesophageal sphincter (early) o Ulcers, fusiform peptic stricture (late) o GORD, Barrett’s oesophagus * Small bowel o Marked dilatation of small bowel, especially duodenum and jejunum o Duodenal findings identical to superior mesenteric artery (SMA) syndrome o Hidebound small bowel: Atonic with closely spaced, thin folds, sacculation (pathognomonic of scleroderma) o Prolonged transit time with barium retention in duodenum and small bowel up to 24 hours o Penumatosis intestinalis and pneumoperitoneum o Transient, nonobstructive intussusceptions * Colon o Sacculation on border of transverse and descending colon o Loss of haustrations o Stercoral ulceration (from retained faecal material in rectosigmoid) * Top Differential Diagnoses o SMA syndrome o Celiac-sprue disease o Ileus

Answer 41

**Hypoperistalsis in the upper third of the oesophagus** The oesophagus is the most involved location of the gastro-intestinal tract in patients with scleroderma. Smooth muscle atrophy causes hypoperistalsis and eventually aperistalsis in the lower two-thirds of the oesophagus. The upper third of the oesophageal wall contains skeletal muscle and is therefore unaffected by the disease process.

Answer 42

**GI scleroderma** Deeply penetrating ulcers are seen in Behcet’s disease. Whipple disease is an extremely rare form of intestinal lipodystrophy. Thickening of jejuna folds is seen, but there is little or no small bowel dilatation and small bowel transit time is normal. Pseudodiverticula are not seen in coeliac disease. The valvulae are thickened in lymphoma.

Answer 43

**Oesophagus** is most frequently affected (75-90%) followed by anorectum (50-70%), small bowel (40%) and colon (10-50%). The stomach is the least affected in the GIT

Answer 44

**Scleroderma** Scleroderma, strongyloides, and cystic fibrosis are causes of decreased/absent folds. Crohn’s and amyloidosis can cause decreased or increased folds.

Answer 45

**Coeliac disease complicated by lymphoma** Whipples disease, cavitating mesenteric lymph node syndrome, and abdominal TB more typically have mesenteric lymph node enlargement that has central low attenuation, rather than being of homogeneous soft-tissue density. Whipple disease is a systemic bacterial infection caused by Tropheryma whippelii. Lymph nodes affected by Whipple disease typically have a high fat content, causing the low attenuation, usually between 10 and 20 HU. Cavitating mesenteric lymph node syndrome is associated with coeliac disease. The lymph nodes are truly cavitating and usually regress following a gluten-free diet. The lymph nodes in abdominal tuberculosis typically have caseous necrosis and thus central low density on CT. Castleman disease causes benign masses of lymphoid tissue of unknown aetiology. It can cause mesenteric lymphadenopathy, which is homogeneous, but the disease itself is rare and mesenteric involvement is much less common than mediastinal involvement.

Answer 46

**Coeliac disease** The segmentation and ﬂocculation of barium are ﬁndings on a small bowel series that are typical of malabsorption and therefore the most likely diagnosis is coeliac disease. Other ﬁndings in coeliac disease include dilatation, a granular appearance to the barium secondary to hypersecretion, jejunization of the ileum, and the ‘moulage’ sign. The latter refers to a smooth, tubular appearance to the jejunum in longstanding coeliac disease, secondary to atrophy and effacement of the jejunal mucosal folds. Lymphoma can be a complication of coeliac disease and generally causes shallow, ulcerated masses or the development of thickened, nodular small bowel folds.

Answer 47

**Coeliac disease** Jejunal dilatation and jejunisation of the ileal loops are characteristic features of coeliac disease. This is an immunological intolerance to gluten that causes villous atrophy in the small intestine. In Whipple disease there is thickening of the jejunal and duodenal mucosal folds but typically no luminal dilatation. Dilatation of the small bowel does occur with lymphoma but jejunisation of the ileum is not a feature.

Answer 48

**Coeliac disease** All of these may cause malabsorption. Amyloid can cause dilatation but also causes diffuse thickening of the valvulae conniventes throughout the small bowel. With Whipple disease and eosinophilic gastroenteritis, one would not see dilatation of the bowel, but thickening of the mucosa is again a prominent feature. Giardiasis causes thickening and marked distortion of the mucosal folds in the duodenum and jejunum. One of the hallmark features of untreated coeliac disease is jejunal dilatation. Typically, the mucosal folds are of normal thickness.

Answer 49

**Coeliac disease** Coeliac disease is characterized by malabsorption due to intolerance to the alpha-gliadin component of gluten, which causes small intestinal villous atrophy. Typical ﬁndings are of dilatation of the proximal small bowel, together with dilution of the barium column due to hypersecretion of ﬂuid. Artefacts such as segmentation (breaking up of the barium column) or ﬂocculation (clumping of disintegrated barium) were traditionally classic features of coeliac disease but are less often seen nowadays with improved barium suspensions. In Whipple’s disease the small bowel is typically non-dilated and shows moderate fold thickening. Crohn’s disease usually causes nodular fold thickening, and predominantly involves the distal small bowel. Zollinger–Ellison syndrome results in dilatation of proximal small bowel due to hypersecretion, but typically causes thickened folds. Small bowel lymphoma is usually associated with fold thickening.

Answer 50

**Coeliac disease** Cavitating mesenteric lymph node syndrome is a rare complication of coeliac disease, in which multiple enlarged lymph nodes are seen in the jejunoileal mesentery. The nodes have central low attenuation and may contain fat or ﬂuid, or fat–ﬂuid levels. Splenic atrophy is usually seen, and jejunal or duodenal biopsy conﬁrms villous atrophy of the small bowel mucosa. Low- attenuation lymphadenopathy may also be seen in tuberculosis, Whipple’s disease, lymphoma, and necrotic metastases, but fat–ﬂuid levels have been reported only in coeliac disease

Answer 51

**Amyloidosis**. This patient probably has amyloidosis secondary to prolonged RA. GI involvement is more common in primary (70%) than secondary (13%) amyloidosis. Nevertheless, the small bowel is involved in 74% of cases of GI amyloidosis and secondary amyloidosis is the most common type of amyloid disease. Amyloidosis is secondary to the deposition of insoluble amyloid protein in soft tissues and organs. In primary amyloidosis the heart (90%), followed by the small bowel and the lungs (70%), are the most affected organs. The kidneys are affected in 90% of cases of secondary amyloidosis. Amyloidosis classically causes a diffuse thickening of bowel folds. It may cause dilated bowel folds if the myenteric plexus is involved. The main differential for amyloid is Whipple’s disease and intestinal lymphangiectasia. Whipple’s disease does not cause bowel dilatation or rigidity, as described in the antrum in this patient. Crohn’s disease can also present with thickened folds, but it is more commonly focal with the most pronounced abnormality in the terminal ileum. Ulceration is also commonly seen in Crohn’s, but 68 years old would be a late ﬁrst presentation for Crohn’s. Whilst option A is true, this is not what the question asked. Patients with mastocytosis most commonly present in infancy . ## Footnote GI Amyloidosis [STATdx] Fluoroscopic findings: * Stomach o Diffuse or focal thick folds (nodular or mass-like) with calcification * Small intestine o Symmetrical regular thickening of folds (with or without nodular component) o Impaired motility often with small bowel dilatation, and o Slow transit * Colon o Luminal narrowing o Loss of haustrations, and o Thickened transverse folds CT findings: * Small bowel, large bowel, and stomach o Wall thickening – focal/nodular mass-like or diffuse, calcified, may infiltrate into mesentery o distention (due to hypomotility) o intramural haemorrhage, o luminal narrowing (due to wall thickening), and o intussusceptions * Liver and spleen o Hepatomegaly or splenomegaly may be only manifestation o Focal, geographic, or diffuse hypoattenuation in liver (mimic steatosis) o Frequently in periportal distribution (with parenchymal calcification) * Spleen o Splenomegaly o Focal or diffuse hypoattenuation (with parenchymal calcification) o Increased risk of spontaneous rupture * Gallbladder wall thickening (extremely rare) * Retroperitoneal soft tissue infiltration resembling retroperitoneal fibrosis * Mesenteric infiltration resembling sclerosing mesenteritis * Lymphadenopathy with calcification * Mass-like amyloidomas in soft tissues with calcification MRI findings: Involved site – Low T2, intermediate to high T1 Whipple Disease [Core Radiology] Def: – A rare systemic disease caused by Tropheryma whipplei, multiple systemic manifestations, including chronic diarrhoea and malabsorption Imaging: 1. Fluoroscopic small bowel follow-through or enteroclysis * Common site – Distal duodenum and jejunum * Severe cases – Distal Ileum * Thickened, irregular folds with sand-like micronodules * Normal or mildly dilated lumen * Thickened mesentery and separation of bowel loops. 2. CT * Mesenteric and retroperitoneal lymphadenopathy with near fat density. (Digested bacilli) * Thickened proximal small bowel folds with or without submucosal oedema due to hypoalbuminemia * Ascites, splenomegaly, pneumatosis intestinalis. 3. MR Lymph nodes may show increased T1 signal due to fat Top Differential Diagnoses: * Celiac disease * Intestinal opportunistic infections * Dysgammaglobulinemia * Intestinal metastases and lymphoma Clinical Issues: * Mostly affects middle-aged White men * Prodromal phase: Fevers, fatigue, arthralgias, arthritis * Late phase: Diarrhea, malabsorption, steatorrhea, adenopathy, abdominal pain * GI symptoms generally later manifestation of disease * Can be fatal without therapy (long-term antibiotics) * Clinical symptoms often subside quickly after therapy

Answer 52

**TB**. Cryptosporidiosis is the most common cause of enteritis in AIDS patients. It more commonly causes proximal small bowel thickening in the duodenum and jejunum, and CT may show small lymph nodes. CMV infection of the small bowel can show a terminal ileitis indistinguishable from Crohn’s disease. The typical CT ﬁndings in amoebiasis are thickening of the right colonic wall and a rounded abscess in the right lobe of liver with a peripheral zone of oedema. TB usually shows ileocaecal involvement, low attenuation mesenteric nodes, and ascites with peritoneal thickening. Mycobacterium avium intracellulare may also occur with low attenuation mesenteric nodes and thickening of small bowel folds.

Answer 53

**Ileo-caecal region** Tuberculosis of the gastrointestinal tract may occur through ingestion of infected sputum, or by haematogenous spread to submucosal lymph nodes from a pulmonary tuberculous focus. It most commonly affects the ileo-caecal region due to its abundance of lymphoid tissue and relative stasis of gut contents. Typical features at this site include circumferential thickening of the terminal ileum and caecum, a thickened ileo-caecal valve and ulceration following the orientation of lymphoid follicles (longitudinal in the terminal ileum and transverse in the colon). Marked enlargement of adjacent mesenteric lymph nodes with central areas of low attenuation may be seen

Answer 54

**Giardiasis** All the stems are potential causes for these symptoms in a patient with AIDS, however giardiasis is the most likely cause given these imaging appearances. Cytomegalovirus most typically affects the caecum, and tuberculosis affects the caecum and ileocaecal valve. Mycobacterium avium intracellulare can affect the ileum and jejunum but does not usually cause spasm. Cryptosporidium affects the duodenum, and the jejunum can be affected, but dilatation is more common than spasm.

Answer 55

**Gastrointestinal stromal tumour (GIST)** At contrast-enhanced CT, GISTs appear as large exophytic masses with peripheral enhancement. They usually have an attenuation like that of muscle, but they may have heterogeneous attenuation, depending on their level of aggressiveness. More aggressive GISTs may also contain a central area of necrosis. Adenocarcinoma of the jejunum is rare, more commonly occurring in the duodenum. They also tend to be stricturing lesions, rather than exophytic masses and may present with obstruction. Carcinoid is also rare in the proximal small bowel, the distal ileum being a more usual location. The primary lesion is often quite small, with the nodal metastatic lesion in the small bowel mesentery being more conspicuous on CT. This is often spiculated (surrounding desmoplastic reaction) and may contain calciﬁcation. Lymphoma can have several manifestations in the small bowel, from nodular thickening of the mucosal folds to large masses with aneurysmal dilatation of the small bowel in the affected segment. Associated lymphadenopathy is typical.

Answer 56

**Gastro-intestinal lymphoma ** Hypoattenuating lymph nodes can be attributed to many causes, but lymphoma and tuberculosis are the most common. Lymphoma of the gastro-intestinal tract most commonly affects the ileum, although lymphoma associated with coeliac disease most commonly affects the jejunum. Although 90% of tuberculosis of the gastro-intestinal tract occurs in the ileum, lymphoma is most likely in this scenario. Dilatation of the small bowel with lymphoma is common but obstruction is rare due to the soft pliable nature of the tumour.

Answer 57

**Increased small bowel mucosal enhancement** (HU > psoas) and mural thickening > 3mm are the most common signs. Colon involvement is infrequent, and the small bowel is typically diffusely involved.

Answer 58

**Water intoxication.** All five options are complications of barium enema. Additional potential complications include bowel perforation, barium impaction, and transient bacteraemia. Complications during barium enema are rare. Perforation of the bowel is the most frequent serious complication, occurring in approximately 0.02–0.04% of patients. Venous intravasation may result in a barium pulmonary embolus, which carries an 80% mortality. Water intoxication causes drowsiness and convulsions, as in this case. There is an increased risk in megacolon because of the large area of bowel mucosa available for the absorption of water. Water intoxication has also been attributed to the preparatory laxatives used. Buscopan may cause cardiac arrhythmia and should be used with caution in those with cardiac disease; other relative contraindications include angle-closure glaucoma, myasthenia gravis, paralytic ileus, pyloric stenosis, and prostatic enlargement.

Answer 59

**Insulinoma is a contraindication to the use of glucagon** Glucagon is a potent hypotonic agent. If 1mg of glucagon is injected intravenously it takes approximately 1 minute to work and lasts about 10–20 minutes. Intravenously administered glucagon decreases discomfort during barium enema examinations. Glucagon administration is generally safe but is contraindicated in patients with insulinoma and phaeochromocytoma. Diabetes is not a recognized contraindication.

Answer 60

**Unstable cardiac disease** Buscopan is commonly used in radiological practice as a smooth muscle relaxant. As a non- selective muscarinic antagonist, it produces other autonomic responses including pupillary dilatation and tachycardia and may potentially precipitate an attack of acute angle-closure glaucoma that requires prompt treatment to prevent permanent visual loss. However, most glaucoma is of the open-angle form, which is unaffected by Buscopan, and it is therefore advised that routine enquiry about a history of glaucoma is unnecessary. Instead, patient information leaﬂets should advise all patients to attend hospital immediately should they develop painful, blurred vision. Routine enquiry about prostatism, porphyria and myasthenia gravis are also not recommended. However, in patients with unstable cardiac disease, the tachycardia and slight increase in diastolic blood pressure caused by Buscopan carry the potential risk of arrhythmia. The presence of unstable cardiac disease is therefore deemed to be the only potential reason to withhold Buscopan.

Answer 61

**Rectosigmoid**. On a prone scan during a CT colonography examination, the rectosigmoid is generally better distended than on the supine scan because it is a more posteriorly placed structure and air gets displaced to the non-dependent position. The other segments named are usually better distended on the supine scan, particularly the caecum and transverse colon, as these are more anteriorly placed within the abdomen

Answer 62

**Haustral folds** Most common source of FP in CAD in cathartically prepared CT colonography. Untagged/poorly tagged stool is the second most common FP in cathartically prepared and most common source of FP in non-cathartically prepared CT colonography

Answer 63

**Conventional fistulography has a higher spatial resolution** CTF helps to delineate fistulous tracks in critically ill patients where prolonged contrast studies are not feasible. Iodinated contrast (300mg iodine/ml) should be diluted 1 in 10, with a volume based on an estimate of the length of bowel or volume of cavity being investigated. Oral contrast can confuse the origin of intraluminal contrast and is best avoided, whereas IV contrast is helpful. Conventional fistulography has a higher spatial and temporal resolution.

Answer 64

Conventional defecography is used in the imaging evaluation of obstructed defecation. Barium paste is instilled into the rectum with a Foley catheter, with the patient in the **left lateral position** Prior opaciﬁcation of the small bowel, bladder, vagina or peritoneum may also be performed to aid diagnosis. With the patient sitting on a commode placed on the footrest of a standard ﬂuoroscopic table, static images are ﬁrst obtained at rest and with contraction of the pelvic ﬂoor muscles. A cine-loop of evacuation is then obtained until the rectum is empty or three 30- second attempts at evacuation have been made. A variety of conditions may be demonstrated, including rectocele, enterocele, rectal intussusception and anismus.

Answer 65

**Sigmoid colon** The prone-angled, over-couch view performed as described separates overlying loops of sigmoid colon

Answer 66

**Normal appearance** In angiodysplasia, there is degenerative dilatation of the normal vessels in the submucosa of the bowel wall. It is associated with increasing age, and in about 20% of cases with aortic stenosis. It occurs most commonly in the right colon and presents with intermittent, low-grade bleeding. Barium enema shows no abnormality, as the lesion is submucosal, but increased tracer accumulation may be seen at the site of haemorrhage on 99m Tc-labelled red cell scanning. Angiography, if performed, may demonstrate a cluster of vessels along the antimesenteric border during the arterial phase and early opaciﬁcation of the draining ileocolic vein.

Answer 67

**T2W** MR is a highly accurate method of local staging of rectal cancer, with better assessment of locoregional nodal involvement than CT and clear depiction of the mesorectal fascia, allowing accurate prediction of whether the circumferential resection margin will be tumour free. T2W images provide optimal visualization of the tumour, which appears as an intermediate signal- intensity mass. Contrast-enhanced T1W images result in enhancement of the normal bowel wall as well as the tumour, which may lead to upstaging. FLAIR sequences are not routinely used for rectal cancer staging.

Answer 68

**Ischaemic colitis** Crohn’s colitis is relatively unlikely due to lack of prior history or small bowel involvement and age of the patient. **Ulcerative colitis and pseudomembranous colitis are both unlikely as the rectum is usually involved in these two conditions**. Infectious colitis does not normally affect the left-sided colon only, regardless of the underlying pathogen. Ischaemic colitis is the most likely diagnosis of those listed. It typically affects a segment of bowel, with most cases having left-sided colonic involvement.

Answer 69

**Pseudomembranous colitis** The CT sign of oral contrast becoming trapped between thickened oedematous haustral folds is the ‘accordion’ sign, which is highly suggestive of pseudomembranous colitis. Bowel wall thickening, peri-colonic stranding of fat, and ascites may be seen in all forms of colitis. Pseudomembranous colitis can be segmental but is more commonly a pancolitis.

Answer 70

**Pseudomembranous colitis** Pseudomembranous colitis results from overgrowth of Clostridium difficile most commonly due to broad spectrum antibiotic use in the hospital population. Ascites is often present in severe cases and wall thickening >10 mm is highly suggestive of this diagnosis. A layered pattern of enhancement is often present in severe cases with oedema in the submucosa producing low attenuation in the wall, deep to the enhancing mucosa. The accordion sign is caused by marked submucosal oedema producing thickening of the colonic haustra. The rectum is involved in most cases but any location within the large bowel may be involved.

Answer 71

Although all the above are recognised findings in PMC, **colonic wall thickening** from minor to gross thickening is the most common feature. The relatively **minimal pericolonic stranding with marked colonic wall thickening** may help to distinguish PMC from other colonic pathologies.

Answer 72

**Pseudomembranous colitis** Pseudomembranous colitis is an acute infectious colitis caused by Clostridium difﬁcile and its toxins A and B; this pathogen has become increasingly common largely due to widespread use of broad-spectrum antibiotics. The commonest CT ﬁnding is of colonic wall thickening (due to mural oedema and the presence of pseudomembranes), which is typically greater than in other causes of colitis apart from Crohn’s disease. Pericolonic inﬂammatory changes are disproportionately mild relative to the marked wall thickening. Ascites is common, and this, together with the lack of small bowel involvement, can help to distinguish pseudomembranous colitis from Crohn’s colitis. Ischaemic colitis demonstrates less wall thickening, and is usually segmental, tending to affect the watershed areas of the colon.

Answer 73

**Plain abdominal film** Toxic megacolon is a complication of ulcerative colitis, Crohn’s and other forms of acute colitis. It has a poor prognosis with up to 20% mortality. Plain abdominal radiography should be the first line investigation for suspected toxic megacolon and can be repeated 24 or 48 hourly if necessary. It can often confirm the diagnosis without the need for CT, which is especially useful when considering radiation dose issues in this group of young patients. Typical features on plain film include transverse colon dilatation >5.5 cm, loss of normal haustral folds, thumbprinting of the colon and the presence of mucosal islands (pseudopolyps). CT better demonstrates potential complications of toxic megacolon such as perforation of the bowel.

Answer 74

**Crohn’s disease** These features are highly suggestive of Crohn’s disease. Signs on double contrast barium enema that favour a diagnosis of Crohn’s disease over ulcerative colitis include **apthoid ulcers, deep ulcers, discontinuous ulceration, rectal sparing, pseudodiverticulae, fistulae and abscess formation.** Ulcerative colitis can be suggested by rectal involvement, continuous pathology with no skip lesions and the presence of mucosal granularity. However, these features may also be present in Crohn’s and are not specific for ulcerative colitis. Although tuberculosis is a mimic, colonic involvement in this pattern is uncommon compared with Crohn’s disease.

Answer 75

**Circumferential wall involvement** Ulcerative colitis and Crohn’s disease are idiopathic inﬂammatory diseases of the bowel. Ulcerative colitis predominantly involves the mucosa and submucosa, and characteristically produces continuous, circumferential involvement of the colon. Crohn’s disease produces transmural inﬂammation, may affect the entire gastrointestinal tract, and is characterized by eccentric and discontinuous involvement. Typical features of ulcerative colitis include predominantly left-sided colonic involvement with rectosigmoid involvement in 95% of cases, a patulous ileo-caecal valve and shallow ulceration. Typical features of Crohn’s disease include skip lesions (discontinuous disease), terminal ileal involvement with a thickened ileocaecal valve and ﬁstula formation.

Answer 76

**Typhlitis** Typhlitis, or neutropaenic enterocolitis, is acute inflammation of the caecum, ascending colon, terminal ileum, or appendix. It is typically described in children with neutropaenia secondary to lymphoma, leukaemia, and immunosuppression. Concentric, often marked, bowel wall thickening with pericolic inflammatory changes is typical, and such changes in a young, immunosuppressed child should raise suspicion of typhlitis as a cause. Perforation is a risk factor and therefore contrast examinations are usually avoided.

Answer 77

**Radiation injury of the rectum** Gastrointestinal complications following external radiotherapy are becoming more frequent as survival rates of patients with abdominal cancer improve, and they may present up to 15 years following irradiation. The colon and rectum are commonly affected following irradiation for pelvic and genitourinary tract malignancies. Chronic radiation colitis usually presents with strictures, whereas rectal injury manifests as a narrowed, thickened, poorly distensible rectum, with proliferation of the perirectal fat and thickening of the perirectal fascia. There is an increased incidence of colorectal carcinoma following pelvic irradiation, but a short irregular segment of narrowing would be more likely. Inﬂammatory bowel disease may result in circumferential rectal wall thickening with widening of the presacral space but is less likely given this history. Hirschsprung’s disease usually presents in early childhood. The rectum is an uncommon site for gastrointestinal lymphoma

Answer 78

**Turcot syndrome** FAP is a rare autosomal dominant condition resulting in the growth of hundreds of adenomatous polyps in the large bowel. Clinical symptoms commence from the third decade and include abdominal pain and PR bleeding. Colorectal cancer develops in almost all before the age of 40 years. Turcot syndrome is characterized by the association of colonic polyps like FAP and central nervous system tumours, typically medulloblastoma and glioblastoma multiforme. The combination of intestinal polyposis (identical to FAP) and numerous osteomas and epidermal cysts is typical of Gardner syndrome. Lynch syndrome is hereditary non- polyposis colorectal cancer. Colorectal carcinoma occurs earlier than in the average population. There is also an association with ovarian and endometrial malignancy. Chronic inﬂammatory bowel disease is not associated with CNS malignancy.

Answer 79

**Peutz–Jeghers** Peutz–Jeghers syndrome is most consistent with these findings. It is an autosomal dominant syndrome but often arises as a spontaneous mutation. Hamartomas are found throughout the gastro-intestinal tract, except for the oesophagus. The polyps have almost no malignant potential, but life expectancy is decreased due to associated cancers arising in the stomach, duodenum, colon, and ovary. Gardner’s syndrome and familial polyposis are both associated with small bowel adenomas in approximately 5% of cases. Cowden’s syndrome does involve hamartomatous polyps, but these are typically rectosigmoid, and small bowel involvement is not a feature. Small bowel polyps are not a feature of Turcot’s syndrome.

Answer 80

**Multiple filling defects in the small bowel** Peutz–Jegher syndrome is characterized by multiple benign hamartomatous intestinal polyps and mucocutaneous pigmentation. It is familial in 50% of cases, with an autosomal dominant inheritance, and sporadic in 50%. It is the most common polyposis syndrome to involve the small intestine, and frequently presents with intussusception. Typical ﬁndings are of multiple hamartomatous polyps in the small bowel, and less commonly the colon and stomach. Patients are at increased risk of gastrointestinal malignancy, but also of tumours of the pancreas, breast, ovary, endometrium and testis.

Answer 81

**Gardner’s syndrome ** Gardner’s syndrome is an autosomal dominant condition with colonic polyps present in all patients. Small bowel, duodenal and stomach polyps are also a feature. Extra-intestinal features include osteomas of membranous bone (typically the mandible as described in the question), other soft-tissue tumours and periampullary carcinomas. Osteomas are not a feature of the other conditions. Cronkhite–Canada syndrome and Peutz–Jegher syndrome are associated with multiple hamartomatous polyps of the colon and stomach. Cronkhite-Canada syndrome is a sporadic non-familial disorder. Lynch syndrome, or hereditary nonpolyposis colorectal carcinoma (HNPCC), is associated with increased risk of colorectal adenomas and other malignancies such as endometrial and other gastro-intestinal tract malignancies.

Answer 82

**Adjacent abscess formation.** Abscess formation has been found to be the most speciﬁc ﬁnding in appendiceal perforation, along with extraluminal gas and small bowel ileus. Abscess formation is also one of the least sensitive ﬁndings. Regional mesenteric lymph nodes are the most sensitive but are reasonably non-speciﬁc. A focal wall defect, if seen, is reasonably sensitive and speciﬁc. Appendicolith is only found in 50% on CT and has a speciﬁcity of 70%.

Answer 83

**Loss of visualisation of hyperechoic submucosa** The use of ultrasound for the diagnosis of acute appendicitis is particularly useful in children and women of child-bearing age. Findings indicating acute appendicitis include a tubular non- compressible blind-ending structure with diameter >6 mm and wall thickness >2 mm, although these signs do not necessarily indicate perforation. Features suggesting perforation include a fluid collection adjacent to the appendix, gas bubbles near the appendix and loss of visualisation of the submucosal layer.

Answer 84

**90%** A laminated calciﬁed appendicolith is seen in only 7–15% of patients with acute appendicitis. However, the presence of acute abdominal pain with an appendicolith on abdominal plain ﬁlm indicates a 90% probability of acute appendicitis, and also indicates a high probability of gangrene/ perforation. Other plain ﬁlm signs of acute appendicitis include caecal wall thickening, small bowel obstruction and focal extraluminal gas collections

Answer 85

**Sigmoid diverticulitis** The inferior mesenteric vein provides venous drainage for the rectum, sigmoid and descending colon, and is a potential route of spread of neoplastic and inﬂammatory conditions. Inferior mesenteric vein thrombosis may occur secondary to an inﬂammatory process, most commonly diverticulitis, or malignancy. Other potential causes include hypercoagulable states, surgery, trauma and bowel obstruction. Appearances are of an enlarged vein with rim enhancement surrounding central low-density thrombus. Superior mesenteric vein thrombosis is much more common (95% of mesenteric venous thrombosis) and may follow an inﬂammatory or neoplastic process affecting the small intestine, caecum, and ascending and transverse colon.

Answer 86

**Epiploic appendagitis** Epiploic appendagitis is inflammation of one of the epiploic appendages of the colon, with the sigmoid being the commonest site. It typically presents with acute abdominal pain and is an important radiological diagnosis as it can often mimic appendicitis, and management is conservative. The diagnosis is usually made on CT with the features described in the question. Ultrasound is rarely used for diagnosis, and features include a non-compressible hyperechoic mass with hypoechoic margins.

Answer 87

Self-limiting condition with fat density mass 1-4cm between colon and abdominal wall. The absence of blood flow on Doppler due to torsion helps distinguish from acute diverticulitis. Omental infarcts are usually large, right-sided and cake-like in appearance.

Answer 88

**Epiploic appendagitis** Acute epiploic appendagitis is thought to result from torsion of one of the fatty epiploic appendages arising from the serosal surface of the colon. It usually occurs in young men, presenting as acute lower quadrant pain, and is associated with obesity and unaccustomed exercise. Typical CT ﬁndings are of an oval peri-colonic fat density lesion of ,5cm, with surrounding inﬂammatory changes, most commonly in the sigmoid, descending or right hemi- colon. Right-sided epiploic appendagitis may be mistaken clinically for appendicitis. Omental infarction typically appears as a larger, heterogeneous lesion, usually affecting the caecum or ascending colon. Acute diverticulitis usually occurs in older patients and is associated with colonic diverticula and wall thickening. Liposarcoma is rare but is included in the differential of a fat-containing intra-abdominal mass.

Answer 89

**Benign tumour** The patient has presented with a colo-colic intussusception secondary to a lipoma of the colonic wall. The intussusception has been complicated by large bowel obstruction. Intussusception is caused by prolapse of a portion of the bowel into the lumen of the adjoining bowel lumen segment. Intussusception is most commonly a disease of young children and most commonly occurs in an ileocolic location. In children, over 90% of intussusceptions are idiopathic and no lead point is identiﬁed. In adult patients approximately 80% of intussusceptions are caused by lead point lesions. The CT appearances described are typical of an intussusception. The low attenuation distal lead point represents the lipoma. Ultrasound is often used to diagnose intussusception in children and will show a mass with echogenic rings representing the fat in the invaginated mesentery.

Answer 90

**Lipoma** The colon is the commonest site for gastrointestinal lipomas. They typically appear as a broad- based mass but may develop a short pedicle because of repeated peristaltic activity. They are soft lesions, and a change in shape or size may be noted on compression. At CT colonography, endoluminal features are non-speciﬁc, but the demonstration of fat attenuation on 2 D images is diagnostic. Primary pneumatosis coli usually appears as a cluster of air-ﬁlled cysts in the left colon. These may mimic polyps at endoscopy or on endoluminal CT colonography, but the demonstration of air attenuation on 2D images is again diagnostic. Endometriosis and enteric duplication cyst are causes of submucosal lesions but are of soft-tissue and ﬂuid density respectively. Adenomatous polyps are mucosal lesions of soft-tissue density.

Answer 91

**Villous adenoma** Villous adenomas are a histological subtype of adenomatous polyps with predominantly villous elements, representing 10% of adenomatous polyps. Typical appearances are of a broad-based lesion often over 2cm in diameter, with **frond-like** surface projections. They have a higher malignant potential than the other subtypes of adenomatous polyp (tubular and tubule-villous adenomas), which increases further with the size of the adenoma. Lesions under 5cm have a 9% risk of malignant transformation to adenocarcinoma, whereas **lesions over 10cm have a 100% risk of malignant transformation**. Villous adenomas are associated with excretion of **large amounts of thick mucus**, which may result in diarrhoea and electrolyte depletion, as well as poor mucosal coating at barium enema. Lipomas are typically seen as smooth, rounded, submucosal masses. Tubular adenomas are usually ,10mm and, like lipomas, are not associated with electrolyte depletion. Solitary rectal ulcer syndrome may appear as polypoid lesions in the rectum and be associated with mucus secretion; however, it is normally associated with ulceration and is usually seen in young women.

Answer 92

**Mucosal ulceration** The differentiation between complicated diverticular disease and a perforating colorectal carcinoma may be difﬁcult. Both may appear as a focal area of eccentric luminal narrowing on contrast enema. A longer segment of involvement favours diverticulitis, as well as other inﬂammatory causes of colitis. In addition, stricture margins in diverticulitis tend to be smoothly tapered rather than the abrupt narrowing of carcinoma. Mucosal ulceration occurs in most cases of colorectal carcinoma and is not a particular feature of diverticulitis. Fistula formation may occur in both conditions, most commonly between the colon and the bladder, though this is more commonly seen in diverticulitis. The presence of diverticula does not exclude the possibility of colorectal carcinoma, and the two conditions may coexist, as both are common in elderly people.

Answer 93

**CT of the thorax, abdomen, and pelvis** Patients with colon cancer diagnosed endoscopically or suspected following barium enema should be imaged for staging purposes. Objectives of staging include determination of size and local extent of tumour, assessment of the extension of tumour into adjacent structures, and detection of local and distant nodal involvement and presence of metastatic disease. Abdominal ultrasound scan alone is not considered sufﬁcient, and CTof the chest, abdomen and pelvis with oral and intravenous iodinated contrast medium is the primary imaging investigation. The liver is the commonest site of distant metastases, but pulmonary metastases occur in 5–50% of patients. 18 FDG PET/CT is not used in initial staging but is particularly useful for detecting recurrent disease

Answer 94

**T3, N1, M0**. T3 implies invasion beyond the muscularis propria into the pericolic fat. CT is quoted as 80% accurate in detecting extramural spread and nodal stage. T1 and T2 tumours are well-deﬁned with no extension beyond the bowel contour. CT features of a T4 tumour include nodular penetration of the tumour through the peritonealized areas of the muscle coat or an advancing edge of the tumour penetrating adjacent organs. Nodal positivity is based on any node >1 cm or a group of three or more nodes.

Answer 95

**T2** The layers of the rectum are well demonstrated at transrectal ultrasound. The innermost hyperechoic layer represents the balloon-mucosa interface, the middle hyperechoic layer represents the submucosa, and the outermost hyperechoic layer represents the serosa. The tumour described in the question extends through the submucosa into the muscularis propria (outer hypoechoic layer) but does not involve the serosa. T1 disease is limited to the submucosa, T2 is limited to the muscularis propria, T3 extends through the serosa and T4 represents invasion of adjacent organs. The correct staging for the tumour described in the question is therefore T2.

Answer 96

Increased blood volume, increased blood flow, decreased mean transit time and increased permeability are parameters on CT perfusion which have been shown to favour a diagnosis of cancer rather than diverticulitis. C and D have high positive predictive values in diagnosing diverticulitis and A and B occur in both.

Answer 97

**There is a prognostic difference between different types of T3 tumours depending on tumour size** The MERCURY Trial showed patients with T3 disease with more than 5mm of extramural spread have a markedly worse prognosis than those with less than 5mm spread beyond the outer muscle layer. A distance less than 2mm from mesorectal fascia indicated CRM involvement. Tumour signal is usually in between SI of muscle and fat. Mucinous tumour is higher signal than non-mucinous which is higher than fat on T2.

Answer 98

**Small bowel obstruction, as can occur in up to 30% of these patients** Total colonic resection with J pouch anastomosis is carried out in patients with ulcerative colitis or familial adenomatous polyposis (FAP) to resect the entire colon but retain anal defaecation. One of the main contraindications to total colectomy and J pouch formation is Crohn’s disease and such a procedure is uncommonly carried out in this situation due to the high recurrence rate. Pouchitis and small bowel obstruction both occur in up to 30% of patients who undergo this procedure. The radiological features of pouchitis are non-speciﬁc but include wall thickening and increased enhancement of the bowel wall, with peri-pouch fat-stranding. Fat- stranding on its own is common because of both the surgery and possible inﬂammatory change due to previous proctitis. Small bowel obstruction most commonly occurs in the region of the ileostomy. Free ﬂuid is often seen in small bowel obstruction. The absence of ﬂuid cavities or air pockets is against a leak from the pouch anastomosis and the clinical features are not consistent with ﬁstula. The blind ending lumen described is the normal appearance seen on a pouchogram.

Answer 99

**Axial T1W fat suppressed FSE before and after gadolinium** May help differentiate tumour from fibrosis and improves destruction of tumour spread to adjacent structures/vessels. Axial and coronal balanced gradient echo are rapidly acquired breath hold sequences providing anatomical overviews. Granulation tissue, haematoma and radiation-induced inflammatory change can all display SI like tumour. Peripheral enhancement with central necrosis is commonly seen in recurrent disease.

Answer 100

**Bladder wall thickened** The urinary bladder and rectum are thickened and oedematous and can show increased T2 and SI. Post-radiotherapy, the ovaries tend to atrophy and therefore decrease in SI but bone marrow, fibrous, glandular tissue can also show increased SI.

Answer 101

**Falciform ligament ** The right subphrenic space is in communication around the liver with the anterior subhepatic and posterior subhepatic (Morison’s pouch) spaces. The right subphrenic and subhepatic spaces communicate freely with the right paracolic gutter and via this with the pelvic peritoneal cavity. The left subphrenic space communicates with the left subhepatic space but is separated from the right subphrenic space by the falciform ligament and from the left paracolic gutter by the phrenico-colic ligament. The falciform ligament is a sickle-shaped fold of peritoneum that attaches the ventral surface of the liver to the anterior abdominal wall. It extends in a parasagittal plane from the umbilicus to the diaphragm and carries the ligamentum teres in its free infero-posterior margin. The lesser sac is an isolated peritoneal compartment between the stomach and pancreas, which communicates with the rest of the peritoneal cavity (greater sac) only through the foramen of Winslow (epiploic foramen). The lesser omentum is composed of the gastro-hepatic and hepatico-duodenal ligaments and suspends the stomach and duodenal bulb from the inferior liver surface.

Answer 102

**Segment 5**

Answer 103

**Middle hepatic vein** The functional segmental anatomy of the liver is based on the distribution of the three major hepatic veins. The middle hepatic vein divides the liver into left and right lobes. The left hepatic vein divides the left lobe into medial and lateral segments. The right hepatic vein divides the right lobe into anterior and posterior segments. In addition, the four sections are further subdivided in a transverse plane by an imaginary line drawn between the right and left portal veins. Segments run in a clockwise fashion, with segments III, IV(b), V and VI lying below the portal veins and segments VII, VIII, IV(a) and II lying above. The caudate lobe (segment I) lies posterior and to the right of the inferior vena cava.

Answer 104

**Hepatic Vein** A trans-jugular intrahepatic portosystemic shunt (TIPSS) is an endovascular procedure performed to create a portosystemic shunt between the portal venous and hepatic venous systems, for decompression of portal hypertension, particularly in patients with variceal bleeding uncontrollable by endoscopic management. The shunt is normally formed between the right hepatic vein and right portal vein. The right internal jugular vein is accessed, and via this the right hepatic vein. Curved needle passes are made in an anterior direction to access the right portal vein. The portosystemic pressure gradient is measured, and portal venography is performed to enable planning of stent placement. A stent is deployed following balloon dilatation of the stent tract. The goal is to decrease the portosystemic gradient to below 12mmHg and to see no signiﬁcant ﬁlling of varices. Portosystemic shunts require close follow- up, as there is a high incidence of shunt stenosis and occlusion.

Answer 105

**Common hepatic artery** In 75% of cases, the gastroduodenal artery arises from the common hepatic artery before its division into right and left branches. Less common origins include the left hepatic artery (4– 11%), the right hepatic artery (7%) and the superior mesenteric artery via a replaced hepatic trunk (4–11%). The artery descends behind the ﬁrst part of the duodenum, lying anterior to the pancreas and to the left of the common bile duct. At this site, erosion of the posterior duodenal wall by an ulcer may produce life-threatening haemorrhage if the gastroduodenal artery is involved. Its main branches are the posterior and anterior superior pancreaticoduodenal arteries, and the right gastroepiploic artery.

Answer 106

**Splenic artery** The main arterial supply to the pancreas is from the splenic artery, which provides numerous small branches into the pancreatic substance as it runs along the superior pancreatic border, as well as several larger arteries including the dorsal pancreatic artery from its proximal end (which may alternatively arise from the coeliac artery) and the arteria pancreatica magna halfway along its length. The pancreatic head has a dual blood supply, from the superior pancreaticoduodenal artery (derived from the gastroduodenal artery) and the inferior pancreaticoduodenal artery (derived from the superior mesenteric artery). The transverse pancreatic artery also runs along the length of the pancreas beside the main duct, and there are multiple anastomoses between the various vessels, allowing multidirectional ﬂow.

Answer 107

**Dual GE T1WI in phase and out of phase.** Three basic MRI techniques are available for fat detection, which work based on the difference in precession frequency between water and fat protons. These are chemical shift imaging, frequency-selective imaging, and MR spectroscopy. Dual GE T1WI is the most useful sequence in clinical practice. It is based on the phase interference effect or chemical shift imaging of the second kind. When the fat and water protons are in phase there is constructive interference and when they are out of phase there is destructive interference. By comparing the signal intensities on the in-phase and out-of-phase images, fat detection is possible. Chemical shift imaging of the ﬁrst kind, or chemical shift spatial misregistration, occurs at fat– water interfaces in the frequency-encoding direction, manifesting as alternating bands of high and low signal. It is present in all standard non-fat-saturated sequences, but it can be subtle and may be missed or mistaken for image noise. Frequency-selective imaging with selective excitation or saturation depends on the homogeneity of the magnetic ﬁeld and the size of the lesion. MR spectroscopy is too time-consuming for routine clinical use.

Answer 108

**Transient hepatic intensity difference (THID)** THID on MRI or transient hepatic attenuation difference (THAD) on CT is a pseudo lesion caused by focal alteration in the haemodynamic of the liver due to either non-tumorous arterio- portal shunt or obstruction of distal portal venous flow. THID or THAD is seen as a focal area of enhancement in the arterial phase only, with no abnormality seen in the portal venous phase. Features suggestive of THID or THAD include peripheral location, wedge shape, straight margins, and normal vessels coursing through the area.

Answer 109

**Axial T2 steady-state GE** Axial imaging is generally going to be better than coronal imaging when trying to distinguish between pneumobilia and calculi within the CBD. The biliary air causes an air/ﬂuid level of air lying on top of ﬂuid in a non-dependent position in the CBD and this is more easily appreciated on an axial image. Calculi tend to lie dependently within the CBD. As ﬂuid is hyperintense on T2WI and hypointense on T1WI, and both air and calculi are hypointense on both these sequences, then both will stand out as being more conspicuous on T2WI.

Answer 110

**Yes, SPIO** Gadolinium chelates are extracellular agents. Gadolinium shortens the T1 relaxation time of adjacent water protons, resulting in signal enhancement on T1WI. It can be used for lesion detection, characterization, and liver vasculature assessment. Gadopentate dimeglumine (Magnevist®) is a commonly used extracellular agent. SPIO particles are reticulo-endothelial agents that are phagocytosed by Kupffer cells. SPIO causes local magnetic ﬁeld inhomogeneity and T2 and T2* shortening, resulting in signal loss on T2WI and T2*WI. Most liver tumours, including HCC, are deﬁcient in Kupffer cells (cf. focal nodular hyperplasia) therefore after administration of SPIO the tumour appears hyperintense relative to the background liver. Mangafodipir trisodium (Teslascan®) is a manganese-based hepatocyte speciﬁc agent that increases the signal intensity of the liver, bile ducts, and some hepatocyte-containing lesions (e.g. FNH) at T1WI. Similarly, gadobenate dimeglumine (Multihance®) is a gadolinium-based hepatocyte speciﬁc agent, which also works best with T1WI due to the T1 shortening effects of gadolinium.

Answer 111

**Microbubble contrast enhanced ultrasound (CEUS)** CEUS can be used to characterise focal liver lesions with 96.6% accuracy. Small HCC (1-2cm) can be diagnosed due to arterial phase hypervascularity and washout characteristics.

Answer 112

**A black boundary effect** These sequences have become the main MR technique for imaging small and large bowel in Crohns disease in recent years. Uniform luminal opacification is obtained with high contrast between bowel wall, lumen, and mesentery. The sequences are relatively insensitive to motion artefact. Black boundary artefact can obscure small lesions on the bowel wall, although fat- suppression can reduce the artefact.

Answer 113

**Gas in the portal venous system** Portal venous gas is identiﬁed on CT as linear branching structures of air density extending to the periphery of the liver, presumably due to the direction of portal venous ﬂow. The commonest cause in adults is mesenteric infarction when it is a poor prognostic sign. In infants the commonest cause is necrotizing enterocolitis when it does not necessarily imply a poor outcome. In contrast, gas within the biliary tree is central and does not extend into the peripheral 2 cm of the liver. In portal venous thrombosis, a focal hypodensity is seen within the portal vein on contrast-enhanced CT. Intrahepatic biliary dilatation appears as dilated branching ductal structures of ﬂuid density. In fatty inﬁltration of the liver, vessels may appear hyperattenuating on unenhanced CT in contrast to the hypodense liver.

Answer 114

**Superior mesenteric and splenic veins** The splenic and superior mesenteric veins join to form the main portal vein slightly to the right of the midline behind the neck of the pancreas at L1–2 level. The extrahepatic portal vein is about 8cm long, and divides into the right and left portal veins at the porta hepatis. The inferior mesenteric vein most commonly drains into the splenic vein, but may drain into the splenic/superior mesenteric vein conﬂuence in 30% of cases or the superior mesenteric vein in 30%.

Answer 115

**Back pain** The most common complication of administration of superparamagnetic iron oxide particles is acute severe back pain, which is seen in approximately 4% of patients. This is thought to be a side effect of particulate agents in general and lasts for the duration of the infusion and slightly beyond. The risk is higher in patients with liver dysfunction, and when the infusion is administered more rapidly than over the recommended 30 minutes. Slowing of the infusion rate or termination of the infusion with recommencement after resolution of the back pain is usually sufﬁcient to alleviate the symptoms

Answer 116

**Hydatid cyst** The most likely diagnosis is hydatid cyst disease. This condition is caused by infection of the liver with the parasite Echinococcus granulosus. Blood eosinophilia is present in up to 50% of patients. It is more common in the right lobe of the liver and is multiple in 20% of cases. Daughter cysts are typical. Percutaneous aspiration of the cyst is positive for hydatid disease in 70%.

Answer 117

The cyst within cyst appearance represents daughter cyst. Other features include wall calcification.

Answer 118

**Schistosomiasis** Schistosomiasis is the most likely cause. Periportal fibrosis with signs of portal hypertension, splenomegaly and siderotic nodules are typical features of hepatosplenic schistosomiasis.

Answer 119

**Amoebic abscess** Pyogenic abscesses are the commonest type of liver abscess in developed countries and are most frequently due to ascending cholangitis from benign or malignant obstructive biliary disease. They are often poorly deﬁned with irregular walls on ultrasound scan and may contain debris or demonstrate intense hyper-echogenicity when containing gas. Amoebic abscesses tend to occur in younger, more acutely unwell patients from high prevalence areas or with a history of recent travel. They are treated medically whereas pyogenic abscesses usually require percutaneous or surgical drainage. Fungal abscesses are usually multiple and occur in immunosuppressed individuals. Hydatid disease tends to be asymptomatic or present with biliary colic. Characteristic ultrasound scan features include daughter cysts and detachment of the endocyst, giving rise to ‘ﬂoating membranes’ within the cyst cavity.

Answer 120

**Hepatic haemangioma** Haemangiomas are the most common benign liver tumour. They are often asymptomatic but may present with hepatomegaly or rarely spontaneous haemorrhage. Typical CT features of a hepatic haemangioma are of a well-deﬁned hypodense mass on unenhanced CT, with early peripheral enhancement after intravenous contrast followed by complete ﬁll-in on delayed images. Hepatocellular carcinoma is seen as a hypodense mass and usually demonstrates contrast enhancement during the arterial phase, but enhancement decreases on delayed images. Focal fatty inﬁltration usually has a geographic distribution, and, like simple hepatic cysts, does not demonstrate contrast enhancement. Focal nodular hyperplasia is usually isodense on unenhanced CT and, although it tends to show intense transient arterial phase enhancement, is often isodense during the portal phase. A central scar, if present, may demonstrate enhancement on delayed images

Answer 121

**Haemangioma** The ultrasound ﬁndings describe a target lesion or bull’s eye lesion. Cavernous haemangiomas can have unusual appearances, but a small lesion such as described will normally have a uniform hyperechoic appearance. Of all the other lesions described, metastasis would be top of the differential, although this appearance is not the most classical for a colonic metastasis. ## Footnote Target lesions in liver ultrasound [STATdx] Target sign: Echogenic centre surrounded by hypoechoic rim (bull's-eye lesions) Malignancy far outnumbers other causes Reverse target: Hypoechoic core with hyperechoic rim Helpful Clues for Common Diagnoses 1. Hepatic Metastases * Solid central tumour with hypoechoic halo * Halo most likely related to compressed hepatic tissue along with zone of cancer cell proliferation * Alternating layers of hyper- and hypoechoic tissue * Usually from aggressive primary tumours – Classic example: Bronchogenic carcinoma 2. Hepatocellular Carcinoma * Background of cirrhosis, portal hypertension, ascites * Rare for cirrhotic livers to develop metastases from non-hepatic primary * Any mass in cirrhotic liver is more likely hepatocellular carcinoma than metastasis 3. Hepatic Lymphoma * Vast majorities are uniformly hypoechoic * Splenomegaly or splenic lesions, lymphadenopathy, thickened bowel wall provide clues toward diagnosis 4. Hepatic Adenoma * Usually iso-echoic or slightly hypo-echoic * Complications such as haemorrhage, central necrosis make centre echogenic * Occasional hypoechoic rim forms target-like appearance 5. Fungal Hepatic Abscess * Often multiple lesions * Typically in immunocompromised patient 6. Amebic Hepatic Abscess * Iso- to mildly hyperechoic center with hypoechoic halo * Abuts liver capsule 7. Pyogenic Hepatic Abscess * Central hyperechoic inflammatory nodule surrounded by hypoechoic halo of fibrosis * Cluster sign: Cluster of small pyogenic abscesses that coalesce into single large cavity * Lobulated or irregular contour Helpful Clues for Less Common Diagnoses 8. Hepatic Atypical Haemangioma * Hypoechoic centre with thick or thin hyperechoic rim - "Typical atypical" appearance * Hypo echogenicity seem to be related to predominant fibrous stroma * Colour Doppler: Typically, undetectable colour flow in lesion – flow is too slow. 9. Hepatic Hematoma * May have laceration tract leading to hepatic surface * Multiple organs involved if traumatic cause

Answer 122

**Focal nodular hyperplasia (FNH)** This is the second most common benign liver tumour. It is thought to represent a hyperplastic response of hepatocytes to an underlying vascular malformation. It is most common in young adult females and is usually an asymptomatic solitary lesion. On histology, FNH consists of hyperplastic hepatocytes and small bile ductules around a central scar. The bile ductules of FNH do not communicate with the adjacent biliary tree. At ultrasound, FNH is isoechoic or hypoechoic. Colour Doppler may show prominent central vascularity. At CT, FNH is typically slightly hyperattenuating or iso-attenuating to surrounding liver on pre-contrast images. On post contrast images, FNH is hyperattenuating in the arterial phase and iso-attenuating in the portal venous phase with hypoattenuating central scar. The scar shows delayed enhancement. At MRI, FNH is iso- to hypointense on T1WI and slightly hyper- to isointense on T2WI. The central scar is hypointense on T1WI and hyperintense on T2WI. The enhancement pattern is like that on CT. If the appearances are atypical, MRI with hepatocyte-speciﬁc contrast agent (gadobenate dimeglumine) may be useful in conﬁrming the hepatocellular origin of the mass. With gadobenate dimeglumine, FNH is iso- to hyperintense on the 1–3 hour delayed images in over 96% of cases. ## Footnote Different MR Appearances of other lesions Hepatic Adenoma [STATdx] * Far less common than FNH * Women on OC pills, pregnancy, Men on anabolic steroid etc. * Key imaging features for all modalities – Hypervascularity, Heterogeneity, Fat content, Haemorrhage, Encapsulation. [FNH is homogenous] * Ultrasound o Complex, hyper-/hypoechoic, heterogeneous mass with anechoic areas (fat, haemorrhage, necrosis, and calcification) o Capsule may be seen o Hyper-vascular (large peripheral arteries and veins) o *Intra-tumoral vein [Absent in FNH] * Angiogram o Centripetal flow o Peripheral enlarged hepatic artery as feeders o Hypo/avascular region (haemorrhage and necrosis) * CT o Encapsulation, o Haemorrhage (best seen in pre-contrast) o Intra-tumoral fat o Hypervascularity o Calcification * MR o Heterogenous T1 and T2 signals depending on content o Rim (pseudo-capsule) is both T1 and T2 dark o Gd-enhanced ▪ Arterial phase – Heterogeneously hyper-vascular in arterial phase ▪ Delayed phase – Pseudo-capsule is hyperintense to liver and adenoma o Primovist-enhanced ▪ No substantial uptake or retention in the delayed phase.

Answer 123

**Regenerative nodules** Regenerative nodules are formed in response to necrosis and altered circulation. They remain enhanced in the portal venous phase as opposed to HCC, which typically demonstrates contrast washout in the portal venous phase. Regenerative nodules have normal hepatocellular function and Kupffer cell density and therefore demonstrate uptake of both hepatocellular agents and SPIO particles. As dedifferentiation proceeds, the hepatocellular function and Kupffer cell density reduce.

Answer 124

**Adenoma** The lesion is most likely to be a hepatic adenoma. None of the other diagnoses typically share these imaging characteristics. Adenomas are benign growths of hepatocytes and are most seen in young women, particularly associated with oral contraceptive use. Eighty per cent are solitary and found in the right lobe of the liver. The high signal on T1-weighted sequences is due to the presence of fat and/or haemorrhage and can distinguish between this and many other lesions in the liver which tend to be of low T1 signal on MR (e.g. metastases, HCC, haemangiomas and FNH). Occasionally, imaging features can overlap with FNH and the two lesions can be difficult to distinguish. However, the majority of FNH lesions are less than 5 cm in size, whereas adenomas tend to be larger.

Answer 125

**Focal nodular hyperplasia** These imaging features are typical of focal nodular hyperplasia. This is the second most common benign liver tumour and typically occurs in women more often than in men. Adenomas are usually larger, enhance less brightly and do not typically have a central fibrous scar. Cavernous haemangiomas are usually high signal on T2-weighted images, and of blood pool intensity on contrast-enhanced T1-weighted images. Fibrolamellar carcinoma also has a central scar, but this is typically of low signal intensity on T2-weighted imaging. Regenerative nodules show high signal intensity on unenhanced T1-weighted imaging and do not have a scar. (Ref: Marin D et al. Focal nodular hyperplasia: typical and atypical MRI findings with emphasis on the use of contrast media.

Answer 126

**Cavernous haemangioma ** Metastases may show peripheral enhancement with complete fill-in on delayed images, but they typically show complete rather than nodular peripheral enhancement and washout on delayed phase imaging. Only haemangiomas typically show peripheral nodular enhancement. Cavernous haemangiomas are the most common benign liver tumours and are usually less than 4 cm in size. Seventy per cent are hyperechoic on ultrasound and they may show acoustic enhancement.

Answer 127

**Accompanying acute subcapsular haematoma** Focal nodular hyperplasia (FNH) is a benign hamartomatous malformation commonest in young women. Lesions are usually smaller than 5cm and contain a central stellate scar in up to one-third of cases. Hepatic adenomas are benign tumours averaging 8–10 cm in size, seen predominantly in young women and related to oral contraceptive use. Lesions have a propensity for spontaneous haemorrhage, presenting as subcapsular haematoma or haemoperitoneum. FNH, though highly vascular, rarely undergoes spontaneous haemorrhage. FNH usually contains sufﬁcient functioning Kupffer cells to demonstrate normal or increased uptake on 99m Tc-labelled sulphur colloid scan, whereas hepatic adenoma, composed of hepatocytes and non-functioning Kupffer cells, appears as a focal photopenic lesion. Both lesions demonstrate transient arterial enhancement following intravenous contrast.

Answer 128

**Adenoma – recommend endovascular embolization** Adenomas are vascular lesions comprising hepatocytes. They may occasionally present with massive haemorrhage and are the most common liver lesion to do so in young people. In this scenario there is active extravasation of contrast implying active bleeding and haemo- peritoneum. Urgent embolisation is the most appropriate treatment to halt bleeding. Conservative or surgical management is unlikely to provide rapid haemostasis. As a proportion of adenomas become malignant, they are usually removed surgically.

Answer 129

**Cavernous haemangioma** Peripheral nodular enhancement with central fill-in is characteristic.

Answer 130

**Fibronodular Hyperplasia** Typically, iso on non-contrast, hyperdense on arterial phase and iso-dense on porto-venous phase. Presence of a central low attenuation scar can be seen in 50% but can also present in adeno and hepatocellular carcinoma.

Answer 131

**FNH** FLC is usually a solidly lobulated well-defined turn, usually low attenuation on unenhanced CT and an even lower attenuation central scar, often with punctate calcification. Delayed enhancement of the scar can occur in both FNH and FLC. However, the scar does not calcify in FNH.

Answer 132

**Mural nodule in cyst’ pattern** RFA produces thermally induced coagulation necrosis, which manifests usually as an oval or round defect on contrast-enhanced CT. The ablation zone is slightly larger than the actual lesion to achieve curative treatment and prevent local recurrence, which is usually seen at the margins of the ablation zone. The following ﬁndings are common in the immediate post ablation period: transient peri-ablational hyperaemia, tiny air bubbles, and arterio-portal shunting. A ‘mural nodule in cyst’ indicates the development of a biloma as a complication of RFA. This is usually seen several months after treatment. It is associated with interval enlargement of the RFA zone.

Answer 133

**Fibrolamellar carcinoma** Fibrolamellar carcinoma occurs in young adults in the absence of normal risk factors for hepatocellular carcinoma. On ultrasound, fibrolamellar carcinoma is of mixed or increased echogenicity, and the hyperechoic central scar is often evident. On unenhanced CT the lesion is of low attenuation, displaying heterogenous enhancement with intravenous contrast administration. The central scar is typically of low signal on both T1- and T2-weighted imaging, which can help differentiate it from FNH (whose scar typically is of low signal on T1 but high signal on T2-weighted imaging). The central scar is present in up to 60% of patients. Calcifications are present in up to 55% and are more common than in hepatocellular carcinoma.

Answer 134

**Peripheral washout on delayed imaging** Peripheral washout of contrast on delayed imaging is virtually diagnostic of malignancy. On post-gadolinium-enhanced T1-weighted images most metastases are hypovascular compared with the surrounding liver and are most conspicuous at the portal phase of enhancement. However, virtually all **metastases exhibit a complete ring of peripheral enhancement**, which is best seen in the early arterial phase.

Answer 135

**Hepatocellular carcinoma** Nodules are a common ﬁnding in cirrhosis, and differentiation of benign nodules from hepatocellular carcinoma (occurring in 7–12% of patients) is vital. Most nodules are regenerative nodules, representing reparative attempts by hepatocytes in response to liver injury. These are typically under 10mm in size and appear isodense to liver parenchyma on CT, unless they contain iron deposits (siderotic nodules), in which case they may be slightly hyperdense. Dysplastic nodules are proliferative premalignant lesions found in 15–25% of cirrhotic livers. They resemble regenerative nodules on CT but are usually larger than 10mm. Hepatocellular carcinomas usually appear as encapsulated hypodense masses that demonstrate rapid arterial enhancement and early washout of contrast on delayed images. Hepatic haemangioma usually appears as a low-density mass, but has different enhancement characteristics, demonstrating peripheral enhancement with complete ﬁll-in on delayed images. Focal fatty sparing appears as an area of normal density in a generally hypodense liver and does not demonstrate contrast enhancement

Answer 136

**Lesion signal intensity unchanged; rest of liver decreased signal intensity** Superparamagnetic iron oxide (SPIO) particles are iron-based particles of 30–150nm, which, when administered as an infusion 1–4 hours prior to imaging, act as a negative MR contrast agent. They target the reticuloendothelial system, being taken up by macrophages throughout the body, but are preferentially accumulated by the Kupffer cells of the liver. Their superparamagnetic properties result in T2 and T2* shortening of the tissues that accumulate the particles, which show reduced signal intensity on T2W, T2* and, to a lesser extent, T1W images. Most liver tumours do not exhibit uptake, as they are deﬁcient in Kupffer cells. However, as the rest of the liver accumulates SPIO and darkens preferentially, the tumour appears of increased conspicuity. SPIO particles are particularly used, in combination with gadolinium, to improve detection of hepatocellular carcinoma in cirrhotic patients, in whom the parenchymal changes of ﬁbrosis and regenerative nodules make detection with gadolinium alone difﬁcult

Answer 137

**0.5 % risk of tumour seeding down needle track** Uncommon and late complication of RFA. In patients with HCC, tumour seeding occurred in 8/1610 cases in a multicentre study and 1/187 in a single series lesion with subcapsular location. Invasive tumour pattern/poorly differentiated are at higher risk. Mortality rates are typically 0.1-0.5%, major complications 2.2-3.1%, and minor complications 5-8.9%.

Answer 138

**Haemochromatosis.GET2WI** A dual GE T1 in- and out-of-phase sequence is routinely used in identifying lipid content within an adrenal lesion. It is based on the phase interference effect. When the fat and water signals are in-phase, there is constructive interference and when they are out-of-phase there is destructive interference. This results in signal drop-off on the out-of-phase sequence. The reverse effect of decreased signal intensity on in-phase images compared to out-of-phase ones is seen in iron deposition diseases. This is because the echo time for the in-phase sequence is longer than for the out-of-phase sequence, therefore the in-phase sequence is more susceptible to the paramagnetic (dephasing) effects of iron. Haemochromatosis is an autosomal recessive genetic disorder. There is abnormal deposition of iron in parenchymal organs such as the liver, pancreas, heart, etc. In hemosiderosis or secondary haemochromatosis, iron deposition is seen in the reticuloendothelial system of the liver, spleen, and bone marrow. This type of deposition is not associated with tissue damage. A GE T2 sequence demonstrates signal loss due to the magnetic field inhomogeneity produced by the paramagnetic effects of iron. GE sequences are more susceptible to the paramagnetic effects than SE sequences, as there is no 180° rephasing pulse in gradient sequences.

Answer 139

**Decreased signal intensity on T1W and T2W images** In primary haemochromatosis, there is increased duodenal absorption and parenchymal retention of dietary iron, which is accumulated within the liver, pancreas, heart, and pituitary gland. Intracellular iron deposits within hepatocytes result in a paramagnetic susceptibility effect, leading to marked shortening of T1 and T2 relaxation times of adjacent protons. This manifests as a marked reduction in liver signal intensity on T2W and T2 Ã W images, and a moderate loss of signal intensity on T1W images.

Answer 140

**Amiodarone use** The normal liver is between 30 and 70 HU on unenhanced CT and should be 10–15 HU lower than spleen density. On portal venous phase the liver will be approximately 25 HU less than the spleen. Amiodarone contains iodine and can cause the liver to appear of increased density on CT. Other causes include cisplatin use, haemochromatosis, Wilson disease and glycogen storage diseases. The more common finding on CT is a liver of decreased density due to a fatty liver. This has many causes including alcohol use, steroids, chemotherapy, diabetes and nutritional causes.

Answer 141

**Focal fatty infiltration** Focal fatty infiltration occurs typically in the periportal and centrilobar regions of the liver and is commonest adjacent to the falciform ligament. Ultrasound features include a hyperechoic area with geographic margins. CT shows an area of decreased attenuation which does not alter the course of blood vessels or liver contour. The lesions are of high signal on T1-weighted MR imaging, and isointense or low signal on T2-weighted imaging. Haemangiomas would also typically be of increased echogenicity on ultrasound, but would be expected to show increased peripheral enhancement with intravenous contrast on CT.

Answer 142

**Fatty liver related to chemotherapy** Chemotherapeutic agents are commonly associated with fatty liver. Diffuse fat deposition (the commonest pattern) causes a generalized decrease in the attenuation value of the liver on CT, and may be diagnosed with an absolute liver attenuation value of less than 40 HU on contrast- enhanced CT. It may also be diagnosed at unenhanced CT if the liver attenuation value is at least 10 HU less than that of the spleen. Liver metastases usually present as focal, low- attenuation lesions on portal phase imaging. Hepatic venous congestion causes a diffuse decrease in attenuation but is associated with enlargement of the inferior vena cava and hepatic veins due to elevated central venous pressure. Amyloidosis can cause a generalized decrease in liver attenuation, but more commonly appears as discrete areas of low attenuation with reduced contrast enhancement. Budd–Chiari syndrome may also result in a diffuse decrease in liver attenuation, but there is usually patchy liver enhancement and poor visualization of the hepatic veins.

Answer 143

**Loss of liver signal intensity on out-of-phase gradient echo MR images** Fatty liver describes a spectrum of conditions characterized by triglyceride accumulation within hepatocytes. It is common, affecting around 15% of the general population, but is more prevalent among those with obesity, hyperlipidaemia, and high alcohol consumption. Fatty liver may be diagnosed on ultrasound scan if liver echogenicity exceeds that of renal cortex, with attenuation of the ultrasound beam, loss of deﬁnition of the diaphragm and poor visualization of the intrahepatic architecture. CT features include absolute attenuation of less than 40 HU on contrast-enhanced CT and, on unenhanced CT, liver attenuation at least 10 HU less than that of spleen, and relatively hyperattenuating liver vasculature. Chemical shift gradient echo imaging is the most widely used MR technique for assessment of fatty liver, demonstrating Fatty liver describes a spectrum of conditions characterized by triglyceride accumulation within hepatocytes. It is common, affecting around 15% of the general population, but is more prevalent among those with obesity, hyperlipidaemia and high alcohol consumption. Fatty liver may be diagnosed on ultrasound scan if liver echogenicity exceeds that of renal cortex, with attenuation of the ultrasound beam, loss of deﬁnition of the diaphragm and poor visualization of the intrahepatic architecture. CT features include absolute attenuation of less than 40 HU on contrast-enhanced CTand, on unenhanced CT, liver attenuation at least 10 HU less than that of spleen, and relatively hyperattenuating liver vasculature. Chemical shift gradient echo imaging is the most widely used MR technique for assessment of fatty liver, demonstrating

Answer 144

**Enlarged pre-portal space is a recognised finding** Although AIH has a wide variability in imaging appearances, from normal to end-stage chronic liver disease, the most common feature on CT and MR in one series is surface nodularity.

Answer 145

**Hyperdense nodules on non-enhanced CT is the most common finding** Most cases demonstrate hyperdense nodules on the non-contrast study, some of which became iso-dense with contrast. A honeycomb appearance is seen in portal and parenchymal phases and on T2 sequences on MR.

Answer 146

**Amiodarone treatment** Fatty infiltration, malignant infiltration, Budd-Chiari and amyloidosis all demonstrate generalized low density on pre-contrast CT.

Answer 147

**Acute viral hepatitis** Acute hepatitis results in a **diffuse decrease in liver echogenicity** on ultrasound scan, with increased **brightness of the portal triads** resulting in a **‘starry sky’** appearance. Other imaging features include **oedema of the gallbladder fossa and gallbladder wall thickening**. Gallbladder wall thickening (anterior wall thickness .3mm in a non-contracted gallbladder) may be seen in a wide range of intrinsic and extrinsic conditions. The commonest intrinsic cause is cholecystitis (acute and chronic), whereas common extrinsic causes include hepatitis, hypoalbuminaemia, heart failure and renal failure

Answer 148

**Thorotrastosis** Thorotrast (thorium dioxide), an alpha-emitting radioactive isotope of atomic number 90 and long half-life, was used as a contrast agent until the mid-1950s, predominantly for cerebral angiography and reticuloendothelial imaging. It is retained indeﬁnitely by the reticuloendothelial system, and results in increased density of the liver, spleen, and lymph nodes with a characteristic stippled appearance. It is associated with delayed malignancies, including angiosarcoma, cholangiocarcinoma and hepatocellular carcinoma. Haemochromatosis may result in diffusely increased density of the liver and spleen, but usually presents earlier in life. Amiodarone may result in increased liver attenuation of 95–145 HU (normal 30–70 HU), but splenic involvement is not usually a feature. Sickle cell anaemia can result in a shrunken calciﬁed spleen, but again is unlikely in this age group. Glycogen storage disease can result in a generalized increase or decrease in hepatic density on CT, but increased splenic density is not a feature. ## Footnote Case courtesy of Dr Rohit Sharma, Radiopaedia.org, rID: 73597

Answer 149

**Selective superior mesenteric angiogram** Variations in hepatic arterial anatomy are common. According to Michel classification, the classic hepatic arterial anatomy with the hepatic artery proper dividing into the right and left hepatic arteries is seen in only 55% of the population. A replaced right hepatic artery from the SMA is seen in 11% and an accessory right hepatic artery from the SMA is seen in 7% of the population. A selective SMA angiogram should therefore be performed in this case. A selective left gastric angiogram is not required as it is a branch of the coeliac axis. The inferior mesenteric artery does not supply the liver. The coeliac axis divides into the common hepatic, left gastric, and splenic arteries. Embolization of the coeliac axis is therefore not an option.

Answer 150

**Dilated hepatic veins and IVC** Elevated right atrial/central venous pressure due to cardiac decompensation results in impaired venous drainage from the liver, producing passive hepatic congestion. If prolonged, passive hepatic congestion can result in cardiac cirrhosis. On CT imaging, retrograde enhancement of dilated IVC and hepatic veins is seen in the arterial phase. In the portal venous phase, there is delayed/reduced enhancement of the hepatic veins due to impaired venous drainage. There is heterogenous enhancement of the liver parenchyma due to venous stasis. Other features of cardiac failure may be evident. Acute Budd–Chiari syndrome is characterized by narrowed hepatic veins and intrahepatic IVC (secondary to compression by the enlarged liver) and by flip-flop pattern of enhancement between the arterial and the portal venous phases. ## Footnote Budd-Chiari Syndrome [STATdx] Greyscale Ultrasound Findings: * Hypertrophied caudate lobe (which is spared) * Narrowed hepatic veins, hard to visualised * Thrombus in hepatic vein Colour Doppler Ultrasound Findings: * Hepatic veins and IVC o Absent or flat flow in hepatic veins o Reversed flow in hepatic vein or IVC o Bicoloured hepatic veins due to intrahepatic collateral pathways * Portal vein o Slow hepato-fugal flow * Hepatic artery o RI>0.75 NECT Findings: * Acute Phase o Enlarged, diffusely hypodense liver with ascites o Narrowed IVC and hepatic veins o Hyperdense IVC and hepatic vein (thrombus) * Chronic Phase o Heterogeneous hypodensity and atrophy of peripheral liver o Hypertrophy of the spared caudate lobe (often bigger than the right lobe) o Non-visualization of IVC and hepatic veins CECT Findings: * Acute Phase o Classic flip-flop pattern ▪ Early → caudate and peri-IVC portion enhance more than peripheral liver ▪ Late → peripheral liver enhances more than central. o Narrowed hypodense hepatic veins and IVC with hyperdense walls. * Chronic Phase o Total obliteration of hepatic veins and IVC o Large multiple regenerative nodules

Answer 151

**Acute Budd Chiari Syndrome** Budd–Chiari syndrome is caused by obstruction of hepatic venous outﬂow, which may, in turn, be caused by membranous obstruction of the suprahepatic IVC by a congenital web, or hepatic venous thrombosis due to hypercoagulable state, tumour or trauma. Patients develop hepatosplenomegaly and intractable ascites. Doppler ultrasound scan demonstrates non- visualization of, or thrombus within, one or more hepatic veins. CT ﬁndings reﬂect severely impaired blood ﬂow to the liver, with a ‘ﬂip-ﬂop’ enhancement pattern after contrast administration. Early images show prominent central liver enhancement with poor peripheral enhancement, whereas delayed images show central washout with peripheral enhancement. The caudate lobe is typically spared because of its separate venous drainage directly into the IVC, and enhances normally. Passive hepatic congestion complicates heart failure, and results in distended hepatic veins and IVC. Hepatic veno-occlusive disease refers to occlusion of small centrilobular hepatic veins following radio- and chemotherapy in bone-marrow transplant recipients, or related to alkaloid consumption. The main hepatic veins and IVC are normal. Hepatic venous involvement is not a feature of viral hepatitis or primary biliary cirrhosis.

Answer 152

**Osler–Weber–Rendu syndrome** Osler–Weber–Rendu syndrome or hereditary haemorrhagic telangiectasia (HHT) is a rare autosomal dominant multisystem vascular disorder characterized by angio-dysplastic lesions in which there is communication between arteries and veins of varying sizes. It commonly affects the skin, lungs, and mucous membranes but any organ system may be involved. The liver is the most common site of abdominal HHT. Lesions range from tiny telangiectasis to transient perfusion abnormalities and large confluent vascular masses. Coronal maximum intensity projection (MIP) images are useful in appreciating telangiectasis. Liver involvement is associated with arterio-venous shunting, porto-venous shunting, or both, resulting in hyperdynamic circulation, which may lead to high-output cardiac failure. Budd–Chiari syndrome is hepatic vein thrombosis and Von Meyerburg complex is multiple biliary hamartomas. ## Footnote Osler–Weber–Rendu syndrome [STATdx] * Hereditary Haemorrhagic Telangiectasia * Autosomal dominant * Multi-system angio-dysplastic lesions * Mucocutaneous telangiectasias – scalp, nasopharynx, orbit * Visceral organs AVMs – lungs, brain, liver Hepatic Imaging Ultrasound – screening for hepatic involvement in HHT Grey scale ultrasound – Dilated hepatic arteries, abnormal echoes Pulsed doppler – High hepatic artery velocity with low resistive index * Hepatic artery – Portal vein shunt → Pulsatile portal flow * Hepatic artery – Hepatic vein shunt (Severe disease) → abnormal waveform Colour doppler * Tangled masses of enlarged tortuous arteries or * Multiple aneurysms of hepatic arteriole branches within liver CT * Large tortuous extra and/or intra-heaptic arteries * Early filing of hepatic and portal veins * Enlargement of hepatic and portal veins * Heterogeneous enhancement of hepatic parenchyma – THAD – wedge shaped peripheral region of hyperenhancement in arterial phase * Telangiectasias – small vascular spots * Large confluent vascular masses – early and persistent enhancement in subsequent phases → high output heart failure MRI * T1WI: Telangiectasia – hypo- or isointense; Regenerative nodules – bright * T2WI: Telangiectasia – network of flow voids; Regenerative nodules – dark * T1 C+

Answer 153

**Resistive index of 0.9 distal to the stenosis** Knowledge of the vessel ‘waveform signature’ and stenosis ﬂow dynamics is essential in interpreting the Doppler ﬁndings. The hepatic artery is a low resistance vessel with continuous antegrade ﬂow during systole and diastole. Generally, low-resistance arteries have a resistive index (RI) of 0.55–0.7. RIs higher or lower than this range are abnormal. RI is calculated by using the formula RI = (peak systolic velocity – end diastolic velocity)/peak systolic velocity. Most modern ultrasound machines calculate this automatically. A stenosis results in increased arterial resistance to the blood ﬂow proximal to the stenosis. This causes a reduction in the end diastolic velocity disproportionately more than the peak systolic velocity, producing a high-resistance waveform and high RI (due to a greater difference between the peak systolic and end diastolic velocities). This ﬁnding is not speciﬁc to stenosis and may be seen in the postprandial state, and in patients of advanced age and diffuse peripheral microvascular disease or compression (cirrhosis, hepatic venous congestion, cold ischaemia, and any stage of transplant rejection). At and immediately distal to the stenosis there is turbulent ﬂow and a jet phenomenon resulting in an increase in the peak systolic and end diastolic velocity and spectral broadening. Depending on the severity of the stenosis, the artery distal to the stenosis demonstrates the following ﬁndings: tardus-parvus waveform that refers to the late and low systolic peak (i.e., increased acceleration time and reduced peak systolic velocity). Low RI due to a greater reduction in peak systolic velocity compared to the end diastolic velocity. Low RI may also be seen with distal vascular shunts (trauma, iatrogenic, cirrhosis, Osler– Weber-Rendu syndrome).

Answer 154

**Budd–Chiari syndrome** Budd–Chiari syndrome is outflow obstruction of the hepatic veins due to a wide variety of causes, but two-thirds are idiopathic. CT features include ‘flip-flop’ enhancement pattern as described in the question, ascites, hepatosplenomegaly, gallbladder wall thickening and increased portal vein diameter. An enlarged caudate lobe is seen in up to 88%, which enhances normally due its venous drainage passing directly into the IVC.

Answer 155

**HELLP syndrome** Hepatic infarction is rare because of the dual blood supply to the liver via the hepatic arterial system and the portal venous system. Isolated pathology in either of these vascular supplies is unlikely to cause hepatic necrosis as the other supply will usually compensate. HELLP is characterised by haemolysis, elevated liver enzymes and low platelets and is one of the causes of liver infarction

Answer 156

**Portal hypertension** The normal portal vein measures up to 13mm in diameter when measured in the AP direction where the portal vein crosses the inferior vena cava during quiet respiration in a supine patient. Portal venous ﬂow is normally 12–30cm/s and demonstrates respiratory variation but little or no pulsatility, though this may be seen in thin patients. Normal ﬂow is hepato-petal (anterograde ﬂow into the liver). Portal hypertension is deﬁned as an increase in portal venous pressure above 10mmHg and is most caused by cirrhosis in the western world. As portal pressure increases, portal vein diameter increases, and portal ﬂow loses its respiratory ﬂuctuation and becomes slow and turbulent. Reversed (hepato-fugal) ﬂow may occur in 8% of patients and is generally associated with a reduced portal vein diameter. Other ﬁndings include portosystemic collaterals, splenomegaly, and ascites. In portal vein thrombosis, portal vein diameter increases, but no ﬂow is seen on Doppler ultrasound scan. Echogenic thrombus may be seen within the lumen. Cavernous transformation of the portal vein may occur with chronic portal vein thrombosis, representing a conglomerate of collateral veins. Budd–Chiari syndrome affects the hepatic veins.

Answer 157

A Hepatic artery thrombosis occurs in 2-12% of cases, usually between 15-132 days post- operatively. The donor celiac axis is anastmosed to the recipient hepatic artery in orthoptic liver transplants. This can be either at the bifurcation of the hepatic into the right and left hepatic arteries, or at the take-off of the gastroduodenal artery. **As the hepatic artery is the only vascular supply to the bile ducts, hepatic artery thrombosis and stenosis can lead to biliary ischemia**

Answer 158

**Normal post-transplantation findings** Orthotopic liver transplantation is the treatment of choice for patients with end-stage liver disease for which no other therapy is available. Surgery involves one arterial anastomosis (hepatic artery), at least two venous anastomoses (portal vein and IVC) and a biliary anastomosis, and complications may occur at any of these sites. Vascular complications are the most frequent cause of graft loss, and most commonly involve the hepatic artery, with portal venous and IVC complications being relatively infrequent. Biliary complications occur in up to 34% of cases and are the second most common cause of liver dysfunction after graft rejection. They include leak, stricture, and obstruction. Other complications include ﬂuid collections, infection, and malignancy. Normal ﬁndings following liver transplantation include a small amount of free intraperitoneal ﬂuid in the perihepatic region, especially at the hilum, or in the ﬁssure for the ligamentum teres, which usually resolves within a few weeks. Other normal ﬁndings are a right ﬂuid pleural effusion, and periportal oedema, attributed to lymphatic channel dilatation due to lack of normal lymphatic drainage.

Answer 159

**Islet cell tumour with liver metastases** Whilst this tumour is rare, the CT ﬁndings indicate a focal mass lesion in the head of the pancreas. Hyperechoic metastases in the liver are suggestive of islet cell tumour, rather than pancreatic carcinoma metastases, even though pancreatic carcinoma is more common. The islet cell tumour could be a gastrinoma, which is most found in the head of the pancreas and is malignant in 60%. It is also associated with peptic ulcer disease and the ﬁnding of air and ﬂuid in the subhepatic space suggests a perforated duodenal ulcer. ## Footnote Causes of hyper-echoic liver lesion Benign * Hepatic haemangioma * FNH * Hepatic adenoma with high fat content * Focal fatty change * Hepatic AML * Inflammatory pseudotumor of the liver * Lipoma Malignant * Hepatic mets o Colorectal o Treated breast o PNET o RCC o Thyroid o Melanoma o Choriocarcinoma * HCC especially in cirrhotic liver * Cholangiocarcinoma

Answer 160

**Adenocarcinoma of the colon** The most common primary tumours that cause brightly echogenic liver metastases are colonic adenocarcinoma, treated breast cancer and hepatoma. The differential here therefore lies between breast cancer and colon cancer. Colon cancer makes up at least 50% of highly echogenic metastases. In addition, the question states that the patient has no significant past medical history, and therefore treated breast cancer is unlikely.

Answer 161

**Mucinous adenocarcinoma of the gastrointestinal tract** Calciﬁed liver metastases represent up to 3% of liver metastases and are most commonly seen with mucinous carcinomas of the gastrointestinal tract. They are also seen in osteosarcoma, breast cancer, lung cancer and carcinoid, but these are less common

Answer 162

**Peritoneal metastases** **Contraindications to liver resection:** Uncontrollable extrahepatic disease such as: non-treatable primary tumour. Widespread pulmonary disease. Locoregional recurrence Peritoneal disease Extensive nodal disease, such as retroperitoneal, mediastinal, or portal nodes. Bone or CNS metastases. Patients with extrahepatic disease that should be considered for liver resection include resectable/ablatable pulmonary metastases; resectable/ablatable isolated extrahepatic sites – for example, spleen, adrenal or resectable local recurrence; and local direct extension of liver metastases to, for example, the diaphragm or adrenal glands, which can be resected.

Answer 163

**Treated breast cancer metastases to the liver** Post-chemotherapy changes to hepatic metastases from breast cancer can cause fine diffuse nodularity resembling cirrhosis known as ‘pseudocirrhosis.’ B-D cause coarse nodularity rather than fine and diffuse nodules in cirrhosis. Mets is unlikely to mimic cirrhosis.

Answer 164

**Rapid washout and residual hypoechoic lesions are features of metastatic deposit.**

Answer 165

**Kaposi’s sarcoma** Kaposi’s sarcoma is a low-grade tumour of the blood and lymphatic vessels that primarily affects the skin but may cause disseminated disease in other organs. It is an AIDS-deﬁning illness and is the most common AIDS-related neoplasm. The commonest manifestation is of multiple raised purplish skin lesions, but lymphadenopathy is the second commonest feature in AIDS-related Kaposi’s sarcoma. Typical appearances are of abdominopelvic lymph nodes that enhance after intravenous contrast due to high vascularity, appearing to be of higher attenuation than skeletal muscle. Liver involvement occurs in 34% of cases at autopsy, and typically causes multiple 5–12mm nodules that are hyperechoic on ultrasound scan and of low attenuation on CT. Skin lesions are present in most cases and help to distinguish Kaposi’s sarcoma from other conditions such as fungal micro-abscesses and multiple haemangiomas, which may have similar appearances on CT. Mycobacterial disease is characteristically associated with low attenuation lymphadenopathy. Non-Hodgkin’s lymphoma is the second commonest AIDS-related neoplasm, and may cause multiple low-attenuation liver lesions, but it is not associated with skin lesions or high-attenuation lymphadenopathy

Answer 166

**Non-visualization of the gallbladder at 1 and 4 hours** Hepatobiliary scintigraphy is most used to evaluate suspected acute cholecystitis. A minimum of 2 hours fasting is required. Following prompt uptake by the liver, the radiotracer is excreted into the biliary system and drains into the small bowel. Activity should be demonstrated within the gallbladder by 1 hour. Morphine can be used during the scan to relax the sphincter of Oddi, thus pushing radiolabelled bile into the gallbladder. Acute cholecystitis is characterized by non-visualization of the gallbladder at both 1 and 4 hours or at 30 minutes following morphine administration. Non-visualization of the gallbladder at 1 hour, but seen at 4 hours, is indicative of chronic cholecystitis. A false-positive diagnosis of acute cholecystitis can occur with previous cholecystectomy, gallbladder agenesis, and tumour obstructing the cystic duct.

Answer 167

**Opiate usage** Opiates, severe hepatitis and CBD obstruction are causes of non-visualisation and no bowel activity. B-D cause bowel activity.

Answer 168

**Secretin** Secretin is a hormone normally secreted by the duodenal mucosa in response to acid within the lumen. It has many physiological effects on the gastrointestinal tract, including stimulation of pancreatic secretions and a transient increase in tone of the sphincter of Oddi. When given intravenously immediately prior to imaging, it results in distension of the pancreatic ductal system and can signiﬁcantly improve visualization of the pancreatic main and branch ducts on MRCP, as well as provide information about the secretory reserve capacity of the pancreas. Effects on the biliary tree are less pronounced and not usually appreciable on imaging. Side effects include abdominal pain, bloating and diarrhoea. Glucagon increases bile ﬂow and has been suggested to improve visualization of the biliary tree at MRCP. Cholecystokinin stimulates gallbladder contraction and is sometimes used in hepatobiliary scintigraphy. Buscopan is widely used in imaging for its inhibition of intestinal motility.

Answer 169

**Choledochal cyst** The only one of the listed diagnoses that would have both these features on HIDA scan is a choledochal cyst. This is a congenital condition characterised by dilatation of the common bile duct and common hepatic duct. Patients typically present in childhood with right upper quadrant pain, a mass and/or obstructive jaundice. Although the diagnosis is usually made with MRCP, HIDA scan can show typical features that include a photopaenic area in the liver representing the dilated CBD/CHD. Although a hepatic cyst would also show a photopaenic area within the liver, small bowel visualisation would be expected. Congenital biliary atresia would cause lack of small bowel visualisation, but the whole liver would take up HIDA and photopaenia would not be present.

Answer 170

**MRCP** Intrahepatic bile ducts are considered dilated when they exceed 40% of the diameter of the adjacent portal veins. The upper limit of normal for the extrahepatic common bile duct is 5mm in adults (increasing after age 60 by approximately 1mm/decade). Appearances here are indicative of biliary obstruction at the level of the hilum, and MRCP is the investigation of choice after ultrasound scan in these circumstances. MRCP reliably demonstrates the extent of ductal involvement, allowing planning of surgery or treatment; with malignant causes, it may provide further staging information. CT is the investigation of choice when ultrasound scan indicates obstruction below the hilum. If ultrasound scan demonstrates ductal stones, ERCP is the investigation of choice for conﬁrmation and therapeutic intervention. Endoscopic ultrasound scan is particularly useful for detecting small ductal stones and periampullary tumours. Percutaneous transhepatic cholangiography is reserved for cases when ERCP is not possible.

Answer 171

**Caroli’s disease** Caroli’s disease is a rare congenital disorder characterized by multifocal segmental saccular dilatation of the intrahepatic bile ducts. It presents in childhood and early adulthood with upper abdominal pain, fever and transient jaundice. Up to 80% of patients have associated medullary sponge kidney. Typical CT ﬁndings are of multiple cystic structures with a central enhancing ‘dot’, representing the portal vein radicles surrounded by dilated ducts. Cholangiography is diagnostic and demonstrates saccular dilatation of the intrahepatic ducts of up to 5cm in diameter, with frequent associated ectasia of the extrahepatic ducts. Choledochal cysts primarily cause cystic dilatation of the common bile duct, but there may be associated intrahepatic biliary dilatation. A choledochocele is a cystic dilatation of the intraduodenal portion of the common bile duct. Primary sclerosing cholangitis classically causes multifocal strictures of the intrahepatic and extrahepatic ducts, alternating with segments of dilatation. In polycystic liver disease, there is no communication of the cysts with the biliary tree.

Answer 172

**Adenomyomatosis is associated with cholesterolosis in up to a third of patients** Option A describes the cause of cholesterolosis. Option B describes the features of xanthogranulomatous cholecystitis (XGC). Option C describes the features of adenomyomatosis. Option D is true, but the ultrasound features described are not those of XGC, so this is not true regarding the condition described in the clinical scenario. Adenomyomatosis and cholesterolosis are both classed as types of hyperplastic cholecystosis. Adenomyomatosis has two pathognomonic descriptions. Firstly, the ‘pearl necklace’ appearance on oral cholecystogram (OCG) (the same appearance can be seen on MRCP). Secondly, comet tail artefact seen on ultrasound, caused by reverberation artefact between cholesterol crystals in Rokitansky–Ashcoff sinuses. ## Footnote Gall bladder adenomyomatosis [Radiopaedia] * Hyperplastic cholecystoses * Hyperplasia of the wall with the formation of Rokitansky-Ashoff sinuses (intramural diverticula lined by mucosal epithelium) penetrating into the muscular wall * Cholesterol crystal precipitate in the bile trapped in Rokitansky-Ashoff sinuses. Radiology * Ultrasound o Mural thickening – diffuse, focal, annular [Annular form mimics gallbladder carcinoma] o Comet-tail artifact * CT o Non-specific wall thickening and enhancement. o Rosary sign – enhancing epithelium within intramural diverticula, surrounded by the relatively unenhanced hypertrophied gall bladder muscularis. * MRI/ MRCP (Oral Cholecystogram) o Mural thickening o Focal sessile mass o Hourglass configuration in annular type o Pearl Necklace Sign – Curvilinear arrangement of multiple rounded T2 bright intramural cavities.

Answer 173

**Adenomyomatosis of the gallbladder** The correct diagnosis is adenomyomatosis. This is an uncommon condition, more common in females, and is associated with gallstones in most cases. It is characterised by generalised or focal mural thickening with intramural diverticula (Rokitansky–Aschoff sinuses). The ultrasound artefact from cholesterol crystals in the sinuses produces bright ‘comet-tail’ reverberation artefacts.

Answer 174

**Cholestrol polyps** Cholesterolosis is a form of hyperplastic cholecystosis in which triglycerides, cholesterol precursors and cholesterol esters accumulate within the lamina propria of the gallbladder wall. Most cases are of the planar type, termed ‘strawberry gallbladder’ after the resemblance of the gallbladder mucosa to the surface of a strawberry, and produce no detectable ultrasound changes. In a minority of cases, cholesterol polyps are formed, which are the commonest type of gallbladder polyp. They are generally small, multiple echogenic lesions adjacent to the gallbladder wall. Non-mobility and a lack of posterior acoustic shadowing helps to distinguish polyps from gallstones. Small size and multiplicity distinguish them from gallbladder malignancy, though, rarely, metastatic disease may produce multiple polypoid lesions, particularly malignant melanoma. Adenomyomatosis, the other form of hyperplastic cholecystosis, results in mucosal hyperplasia and thickening of the muscular layer of the gallbladder. It is characterized by bright reﬂections and comet-tail artefacts from the gallbladder wall on ultrasound scan.

Answer 175

**Dilated common hepatic duct with normal common bile duct** Mirizzi syndrome is a functional hepatic syndrome caused by extrinsic compression of the CHD by a calculus impacted in the gallbladder neck or cystic duct. Low insertion of the cystic duct into the CHD is a predisposing factor. Typical features at imaging include extrinsic compression of the CHD, a gallstone in the gallbladder neck or cystic duct, dilatation of the intrahepatic ducts and CHD proximally, and a normal CBD. Rarely, inﬂammation around an impacted calculus leads to a stricture formation mimicking a periductal inﬁltrating cholangiocarcinoma.

Answer 176

**Emphysematous cholecystitis** This is a rare form of acute cholecystitis. Most patients are between 50 and 70 years of age. It is more common in men (male to female ratio of 2:1) and in those with diabetes and peripheral vascular disease. Emphysematous cholecystitis is a surgical emergency because there is an increased risk of gallbladder perforation and increased mortality rate. The definitive treatment is cholecystectomy, although in critically ill patients percutaneous cholecystostomy may be used as a temporary measure.

Answer 177

**Intramural hypoattenuating nodules throughout the gallbladder** Xanthogranulomatous cholecystitis (XGC) is an uncommon inﬂammatory disease of the gallbladder, which is characterized by multiple intramural nodules and proliferative ﬁbrosis. It is thought to result from rupture and extravasation of bile and mucus following the occlusion of Rokitansky–Aschoff sinuses. There is considerable overlap between the clinical and radiological features of XGC and gallbladder carcinoma. Pericholecystic inﬁltration, biliary obstruction, regional lymphadenopathy and hepatic involvement may be seen in both conditions, and the difference in incidence between the two conditions is not statistically signiﬁcant. Only the presence of multiple intramural hypoattenuating nodules (representing xanthogranulomas) occupying a large area of the thickened gallbladder wall allows a diagnosis of XGC to be made with any degree of certainty. Similar hypoattenuating intramural nodules (representing haemorrhage and necrosis) may be seen less commonly in gallbladder carcinoma, but these tend to occupy a much smaller proportion of the thickened gallbladder wall

Answer 178

**Mirizzi syndrome** Mirizzi syndrome is narrowing of the common hepatic duct caused by a gallstone impacted in the neck of the gallbladder or the cystic duct. The stricture is smooth and often concave to the right as seen on ERCP. Fistulae can develop between the gallbladder and the common duct, and the stone may pass into the common duct. It is associated with acute cholecystitis. Fascioliasis is caused by liver fluke infestation which may cause bile duct wall thickening and multiple hepatic abscesses. Caroli’s disease is a congenital disorder characterised by cystic dilatation of the intrahepatic bile ducts.

Answer 179

**E** In Mirrizzi’s sign, the CBD below the level of the impacted gallstone is not dilated.

Answer 180

**Porcelain gallbladder** It can sometimes be difﬁcult to see a cause for this appearance, and several of the given options could result in it. However, peristalsis should be seen in a healthy patient if the abnormality is due to bowel. With gallstones, the appearance should change on positioning. There is no mention of an ERCP in the history, and whilst air in the biliary tree is common after sphincterotomy, it is often only seen in the gallbladder immediately after the procedure. Patients with emphysematous cholecystitis are usually clinically unwell and are unlikely to be asymptomatic. Porcelain gallbladder is associated with gallstones in 90% of cases. It is a relevant ﬁnding to make as 10–20% of patients develop carcinoma of the gallbladder.

Answer 181

**ERCP with plastic stent insertion** PTC is an appropriate approach, but biliary sepsis can cause bacteraemia during PTC and thus ERCP is preferable in this case, if possible. Contraindications to PTC include prothrombin time greater than 2 seconds higher than control, platelet count less than 100,000, ascites, hydatid disease, and lack of access to surgical facilities. If an ERCP were to fail, the other options would be viable alternatives. Metal stent insertion at the ﬁrst instance is inappropriate unless it is known that the biliary dilatation is due to inoperable malignancy. This is because metal stents cannot be removed, whereas the plastic variety can be removed, if necessary ## Footnote Bild Duct Infection [Core Radiology] Ascending Cholangitis: Symptoms: Pain, Fever, Jaundice (Charcot’s Triad) Imaging: hyperenhancement and thickening of the walls of bild ducts Treatment: Endoscopic biliary intervention if not respond to conservative treatment. Ascending Cholangitis [STATdx] * Def: – Pyogenic infection of biliary tree as result of biliary obstruction * Causes o Stones o Biliary strictures (Benign or malignant) o Recent intervention or hepato-biliary surgery * Symptoms – Pain, Fever, Jaundice (Charcot’s triad) * Treatment – broad spectrum antibiotics and drainage (usually ERCP) * CT and MR findings: o Biliary Trees ▪ Dilatation of intra and/or extrahepatic ducts with abrupt transition ▪ Biliary dilatation may be central, diffuse, or segmental o Bile duct wall – thickening with hyperenhancement o Purulent Bile or Pus – high density of CT, intermediate to low on T1, T2. o Liver ▪ Heterogeneous liver enhancement (wedge-shaped, peribiliary, patchy, or diffuse) ▪ Associated liver abscesses (1/4 of cases) ▪ Portal vein thrombosis * Ultrasound findings o Dilatation, stenosis, and thickening of bile duct walls with intraluminal echogenic debris * Top Differential Diagnoses o Primary sclerosing cholangitis o Recurrent pyogenic, AIDS-related, or chemotherapy-related cholangitis

Answer 182

**Primary sclerosing cholangitis** Primary sclerosing cholangitis is an idiopathic, progressive, ﬁbrosing, inﬂammatory disorder of the biliary tree, causing multifocal strictures, cholestasis, and biliary cirrhosis. There is an association with inﬂammatory bowel disease and autoimmune conditions. In most cases, both intra- and extrahepatic ducts are involved, and classic appearances on cholangiography are of a ‘string-of-beads’ appearance with alternating segments of dilatation and stenosis. Biliary cirrhosis develops in up to 49% of cases, and there is an increased risk of cholangiocarcinoma. In primary biliary cirrhosis, disease is limited to the intrahepatic bile ducts. In ascending cholangitis, there may be biliary dilatation and pneumobilia, but multifocal strictures are not a feature. CT features of choledocholithiasis include biliary dilatation and visualization of a stone in the bile duct, but again strictures are not a feature. Chronic pancreatitis may result in a smooth inﬂammatory stricture of the intrapancreatic portion of the common bile duct.

Answer 183

**Primary sclerosing cholangitis** These ultrasounds and ERCP features are typical of primary sclerosing cholangitis, which is an idiopathic condition characterised by progressive fibrosis of the biliary tree. It primarily affects young men with inflammatory bowel disease (more common in ulcerative colitis than Crohn’s) although pancreatitis, liver cirrhosis and chronic active hepatitis are other associated conditions. Primary biliary cirrhosis may also cause scattered areas of focal intrahepatic duct dilatation, but this condition is much more common in females and the extrahepatic ducts are not involved. ## Footnote Primary Sclerosing Cholangitis [STATDx] Def: - Immune-mediated disease-causing progressive inflammation, fibrosis, and stricturing of intrahepatic and extrahepatic ducts Imaging: * Multifocal "beaded" strictures of intra- and extrahepatic ducts with intervening sites of dilated and normal ducts * Pruned appearance of biliary tree develops over time * Active inflammation → Thickening and hyperenhancement of bile duct wall suggests active inflammation * Peripheral intrahepatic ductal strictures → Visualization of greater than expected number of peripheral ducts on MRCP * Pseudo-tumour of Caudate → Chronic involvement results in atrophy of peripheral liver, massive hypertrophy of central liver/caudate and lobulated, rounded liver contour * Frequent periductal and perivascular fibrosis and confluent fibrosis in central liver → Low density on CT and T2 hypointense on MR * Oedema and inflammation → Periphery patchy T2 hyperintensity on MR * Hepatolithiasis, cholelithiasis, and choledocholithiasis are common → signal voids on MR * Extensive lymphadenopathy common

Answer 184

**Cholangiocarcinoma**. Speciﬁcally a Klatskin tumour, as it occurs at the porta hepatis. Cholangiocarcinoma can be iso- to hyperechoic on ultrasound. On CT and MRI, it shows delayed enhancement in 74%. Many conditions predispose to cholangiocarcinoma and gallstones are identiﬁed in 20–50% of patients with cholangiocarcinoma. Hepatocellular carcinoma would be the next most likely diagnosis. It can have a variable ultrasonographic appearance. Hepatocellular carcinoma usually demonstrates arterial phase enhancement (80%). Prostate does not commonly metastasize to the liver and would again demonstrate arterial phase enhancement classically. Whilst haemangiomas are classically hyperechoic on ultrasound, larger lesions can appear heterogeneously hypoechoic (40%) ## Footnote Cholangiocarcinoma [Core Radiology] * Def: a highly malignant tumour of the biliary ductal epithelium. * Site: o Klastin tumour: A hilar tumour (at the confluence of the right and left intrahepatic biliary ducts) is the most common tumour o Peripheral cholangiocarcinoma is rare. * Imaging o Intrahepatic ductal dilation and lobar atrophy, capsular retraction, tumour extend into the bile ducts. * Risk factors o Choledochal cyst(s). o Primary sclerosing cholangitis. o Familial adenomatous polyposis syndrome. o Clonorchis sinensis infection. o Thorium dioxide (alpha-emitter contrast agent), not used since the 1950s. Thorium dioxide is also associated with angiosarcoma and HCC. Cholangiocarcinoma [STATdx] Ultrasonographic Findings: depend on anatomic site and local tumour extension * Intrahepatic o Mass with ill-defined margin, mixed and heterogeneous echotexture o Isolated thickening of IHBD or intraductal mass with upstream ductal dilatation o Capsular retraction * Hilar CCA (Klatskin tumour) o Dilatation of intrahepatic ducts without extrahepatic ductal dilatation o Apparent non-union of dilated right and left IHBDs o Primary tumour may not be discernible or appears as small, infiltrative iso- /hyperechoic mass in hilar region o Nodular or polypoid mass in bile ducts o Mass effect, invasion of portal vein and hepatic artery * Extrahepatic o Dilatation of intrahepatic and proximal extrahepatic bile duct o Primary tumour often undetectable due to its deep location o Ill-defined, solid, heterogeneous mass within or surrounding duct at point of obstruction o Exophytic or intraluminal o May infiltrate into or cause mass effect on adjacent stomach and duodenum * Other signs of malignancy o Infiltration of liver parenchyma o Lymphatic spread; porta hepatis, para-celiac and peripancreatic lymph nodes o Liver metastases * Important negative findings o Absence of obstructing biliary stones o No obstructing pancreatic head mass or pancreatic ductal dilatation * Contrast-enhanced ultrasound o ICC has variable arterial-phase enhancement (hyper/iso/hypo/rim) o Rim enhancement is most specific type of arterial-phase enhancement o ICC shows rapid (< 1 minute) and marked washout in portal venous/late phase o Can differentiate enhancing tumour from avascular sludge/debris in bile ducts

Answer 185

**Periampullary tumour** The ‘double-duct’ sign is dilatation of the main pancreatic duct and the common bile duct as seen at ERCP and MRCP, and less commonly with CT and ultrasound. It occurs due to an obstructing lesion at the ampulla, most commonly a carcinoma of the head of the pancreas (in up to 77% of cases) or a carcinoma of the ampulla of Vater (in up to 52% of cases). The sign may be absent if there is an accessory pancreatic duct or when the main pancreatic duct drains into the minor papilla.

Answer 186

**Klatskin tumour** Klatskin tumours are the most common form of cholangiocarcinoma, representing tumour at the confluence of the hepatic ducts. The finding of a hyperechoic central porta hepatis mass at ultrasound is typical. Risk factors include inflammatory bowel disease, primary sclerosing cholangitis, Caroli’s disease and cholecystolithiasis. Cholangiocarcinomas have a very poor prognosis with a five-year survival of less than 2%. They are FDG-avid and PET-CT is typically performed in the pre-operative evaluation of these tumours.

Answer 187

**C** Irresectable tumours include those with main PV or main HA invasion, those with both right and left PV or both right and left HA involvement, or involvement of a PV branch to one lobe and a HA branch to other lobe.

Answer 188

**Higher long-term patency rates** Percutaneous or endoscopic biliary stenting is usually performed to relieve jaundice in patients with malignant biliary obstruction. Metallic or plastic stents may be used. Metallic stents have a larger internal diameter and have higher long-term patency rates than plastic stents, as well as a low surface area that reduces bacterial colonization and subsequent ﬁbrous deposition. However, metallic stents become incorporated into the bile duct mucosa and are not easily removed, which may present problems if the stent becomes infected. They are also prone to shortening following deployment, and a long-segment obstruction may therefore require multiple stents. In addition, the cost of metallic stents is approximately 10 times that of plastic stents.

Answer 189

**Enlarged peripancreatic lymph nodes (>15mm)** Enlarged regional nodes are a sign of unresectability, but nodes adjacent to the pancreas are resected as part of Whipple’s procedure. The other factors all indicate that a pancreatic lesion is unresectable. Other features of unresectable pancreatic carcinoma are liver metastases. Only 10–15% of pancreatic neoplasms are resectable at presentation. ## Footnote Solid Pancreatic Epithelial Neoplasm [Core Radiology] 1. Ductal Adenocarcinoma – majority 80-90% a. Commonest in head b. CT protocol (pre, late arterial PV) c. Hypodense, T1 dark mass d. Ductal obstruction is almost always – *consider alternative diagnosis if normal duct e. Distal pancreatic atrophy f. Mass can be occult i.e., iso-attenuating – *suspect if duct is dilated. g. Features of unresectable tumours – encasement of SMA (>180*), extensive venous invasion, metastasis. 2. Acinar cell Carcinoma a. Rare, aggressive, almost exclusively in elderly b. Produces large amount of lipase – Triad of lipase hypersecretion syndrome c. Subcutaneous fat necrosis, bone infarcts (arthralgia), eosinophilia. Pancreatic Adenocarcinoma [STATdx] * Imaging: o Endoscopic USG – best for head of pancreas tumour, also for regional lymph nodes. o CT – local resectability o MRI – for subtle liver metastasis o PET – for distance disease and response to therapy * Syndromes associated with o Peutz-Jeghers syndrome o Familial malignant malenoma o Lynch syndrome o Breast ovarian cancer syndrome o Le-Fraumeni syndrome * Staging o T1 – <2cm; T2 – 2-4 cm; T3 – >4cm or extend beyond pancreas; T4 vascular invasion o N1 – 1-3 regional lymph nodes; N2 – > 3 regional lymph nodes o M1 – distant metastasis * Treatment o Whipple for resectable tumour (can be done without prior histology) o Neo-adjuvant radio/chemo for downstaging before surgery o Possible SMV reconstruction Standard Whipple Procedure * Removal of o Pancreatic head, neck and uncinate process o Duodenum, pylorus, and gastric antrum o Gall bladder and distal CBD o Regional lymph nodes * Anastomoses of o Pancreatico-jejunostomy (end to end) [hand sewn – hard to see on CT] o Hepatico/choledocho-jejunostomy (end to side) [hand sewn] o Gastro-jejunostomy (end to side, with or without Roux loop) [stappled]

Answer 190

**Hepatic artery invasion** The only widely recognised absolute contraindication to curative surgical resection of the options listed is invasion of the hepatic artery. Invasion of the splenic and portal veins are relative contraindications if the veins are not completely occluded. Invasion of the second part of the duodenum is not a contraindication as it is resected at surgery. Other features that make the tumour unsuitable for curative resection are distant metastases, ascites, distant organ invasion, SMA/coeliac/aortic invasion and involved lymph nodes outside the boundaries of the resection.

Answer 191

**Hypo-intensity during arterial phase enhancement** Pancreatic adenocarcinoma is generally a hypo-vascular tumour at CT as well as MRI. Dynamic contrast-enhanced CT has been the gold standard for the diagnosis of pancreatic adenocarcinoma, but MRI is of value in those with renal failure or sensitivity to iodine-based contrast media. Care should be taken in patients with a very low GFR (typically less than 30ml/ min) because of the risk of nephrogenic systemic fibrosis. Contrast-enhanced MRI may have a lower false negative rate than CT, as approximately 10% of pancreatic adenocarcinomas have been shown to be iso- rather than hypoattenuating, on both the pancreatic and portal venous phases. Chandarana et al. have reported that 25 of 25 neoplasms showed hypo-intensity during arterial phase enhancement (and 20 remained hypointense in venous phase), whereas only 12 of 25 were hypointense on unenhanced T1WI, and only 11 of 25 were hyperintense on STIR/T2WI. ## Footnote Imaging for pancreatic adenocarcinoma * Gold standard – CECT o Hypodense, however 10% of them is iso-dense on both pancreatic and PV phase. * Contrast-enhanced MRI – lower false negative than CT (order of decreasing sensitivity) o Arterial phase hypo-intense o Hypo-intense on T1 o Hyper-intense on T2.

Answer 192

**T3N1M0** T1 tumour is disease confined to the pancreas and less than 2 cm in diameter. T2 tumour is also confined to the pancreas but greater than 2 cm in diameter. As the tumour extends beyond the boundary of the pancreas, it is at least T3. Invasion of the coeliac or superior mesenteric arteries would make this a T4 tumour, but as these features are not present it is T3. The presence of regional nodes makes it N1 rather than N0 (no nodes involved), and there is no metastatic disease, so it is M0. Therefore, the correct radiological stage is T3N1M0.

Answer 193

**Ductal adenocarcinoma** Insulinoma tends to be hyperintense on contrast-enhanced images. Gastrinoma is usually hyperintense on STIR imaging and on contrast-enhanced sequences. In a series of 25 patients, an article by Chandarana et al. showed that pancreatic adenocarcinomas were either iso- or hypointense on T1-weighted imaging and iso- or hyperintense on T2 or STIR. All adenocarcinomas were hypointense to pancreatic parenchyma during the arterial phase of gadolinium enhancement on MR, 80% remained hypointense in the venous phase of enhancement and 68% remained hypointense in the delayed phase.

Answer 194

**Gas-containing fluid collection in the pancreatic bed** The two main indications for Whipple’s procedure (radical pancreaticoduodenectomy) are tumour in the periampullary region, and chronic pancreatitis involving the head and uncinate process of the pancreas. Surgery is complex and involves gastrojejunostomy, pancreatico- enterostomy and choledocho-jejunostomy. Common postoperative ﬁndings include retroperitoneal fat stranding and transient, thin-walled ﬂuid collections, which may be in the pancreatic bed, perianastomotic or in Morison’s pouch. Free gas is common and aero-bilia is seen in around 70% of cases, more commonly in the left intrahepatic ducts. Filling of the afferent jejunal loop with contrast is normal and occurs in up to 44% of patients. The commonest complications are delayed gastric emptying, pancreatico-jejunal leak and sepsis. Anastomotic failure can occur at any of the sites, but the pancreatico-enterostomy is most important because of the risk of leakage of pancreatic secretions. Anastomotic leak is associated with increased free gas, perianastomotic ﬂuid and ascites. Focal septic collections can occur anywhere, and complex or gas-containing areas are considered suspicious. Other early complications include vascular injury and thrombosis, Clostridium difﬁcile colitis and pancreatitis of the pancreatic remnant

Answer 195

**Mucinous cystic neoplasm** Mucin is detected in FNA ﬂuid in these lesions. Pseudocysts are uncommon without a history of pancreatitis and the aspirated ﬂuid is high in amylase. The cysts in microcystic lesions are usually smaller than 1cm, except in the oligo-cystic variant. They are also known as serous cystadenomas. Intraductal papillary mucinous tumours cause dilatation of the main pancreatic duct, side branch ducts or both. FNA, either percutaneous or via endoscopic ultrasound, has been described as a low-risk procedure for differentiating pancreatic cystic lesions.

Answer 196

**Serous cystadenoma** Serous cystadenomas are benign neoplasia of the pancreas most seen in older women and are frequently asymptomatic. Typical appearances are of a cystic lesion measuring up to 20 cm in size, containing innumerable small cysts, though these may be difﬁcult to discriminate, giving the appearance of a solid mass. They may occur in any part of the pancreas but are slightly more common in the pancreatic head and neck. Characteristic features include a central stellate scar containing dystrophic calciﬁcation. Mucinous cystadenomas usually occur in the pancreatic tail (90%) and, when multilocular, contain larger cysts of >2 cm in diameter. Pancreatic pseudocysts are usually unilocular and occur following a history of pancreatitis. Intraductal papillary mucinous tumours of the main duct are typically associated with dilatation of the main pancreatic duct. Insulinomas are usually small (,2 cm) solid tumours that produce symptoms early due to recurrent hypoglycaemia. ## Footnote Cystic Pancreatic Epithelial Neoplasm [Core Radiology] 1. Serous Cystadenoma: * Grandma tumour (demographic) * Multiple, small cysts (<2cm) * Could appear solid on CT, needs MR to confirm cystic nature * *Hyper-vascular (unique) * *No duct dilatation or tail atrophy [in contrast to adenocarcinoma] * *Central stellate calcification 2. Mucinous Cystic Neoplasm: * Mother tumour (demographic) * Usually benign but have malignant potential so usually resected * Has capsule 3. Solid and Papillary Epithelial Neoplasm (SPEN) * Daughter tumour (demographic) * Low malignant potential but typically resected. * Large mass with heterogenous solid and cystic areas with haemorrhage. * Has capsule 4. Intra-ductal Papillary Mucinous Neoplasm (IPMN) * Grandfather tumour (but a lot varied) * Wide spectrum of benign, malignant * Main duct or side branch IPMN (main duct type has higher malignant potential) * A cystic intrapancreatic lesion in contiguity with the duct or side branch. * Any nodular or enhancing component should raise concern for malignancy.

Answer 197

**Intraductal papillary mucinous tumour of the pancreas** Intraductal papillary mucinous tumour (IPMT) of the pancreas is a rare tumour. It tends to present in the elderly population and can be a cause of recurrent pancreatitis. Two recognised types include main duct IPMT, in which the main pancreatic duct is dilated, and branch duct IPMT, in which the main duct is usually uninvolved. It is a **risk factor for mucinous carcinoma of the pancreas**. Pancreatic atrophy is often present. Imaging characteristics are often like those seen in chronic pancreatitis, although **calcification is not a feature of IPMT**.

Answer 198

**Multiple cysts < 2 cm separated by a fibrous septa coalescing into a central scar** In serous cystadenoma of the pancreas, the polycystic pattern with cysts < 2cm represents 70% of cases. The honeycomb pattern occurs in 20% and macro/oligocytic type in 10%. Giant subcutaneous serous cystic change with intraluminal haemorrhage and solid serous cystadenoma are atypical manifestations.

Answer 199

Can range from hypoplasia to invasive carcinoma **Parietal nodules and focal wall thickening** are useful indicators in detecting malignant branch IPMT but there is a high incidence of false positive errors. IPMT has a slightly higher incidence in males.

Answer 200

**Intraductal papillary mucinous tumour** Intraductal papillary mucinous tumour (IPMT) of the pancreas is characterized by a mucin- producing tumour with dilatation of the main or branch ducts of the pancreas due to copious secretions. They may arise in the main duct or branch duct. Main duct tumours typically cause dilatation of all or part of the duct, which is ﬁlled with mucinous secretions, appearing hyperintense on T2W images. A T2-hypointense intraductal ﬁlling defect may be identiﬁed, which may represent the tumour or concretions of mucin. Chronic pancreatitis may result in parenchymal atrophy and duct dilatation, with intraductal ﬁlling defects due to calculi or debris, but a bulging papilla at ERCP makes IPMT more likely. The branch duct type usually consists of conglomerated communicating cysts or a unilocular cyst in the uncinate process; these appearances may be mimicked by mucinous cystadenoma and pancreatic pseudocyst.

Answer 201

**Islet cell tumour with liver metastases** Whilst this tumour is rare, the CT ﬁndings indicate a focal mass lesion in the head of the pancreas. Hyperechoic metastases in the liver are suggestive of islet cell tumour, rather than pancreatic carcinoma metastases, even though pancreatic carcinoma is more common. The islet cell tumour could be a gastrinoma, which is most found in the head of the pancreas and is malignant in 60%. It is also associated with peptic ulcer disease and the ﬁnding of air and ﬂuid in the subhepatic space suggests a perforated duodenal ulcer. ## Footnote Causes of hyper-echoic liver lesion Benign * Hepatic haemangioma * FNH * Hepatic adenoma with high fat content * Focal fatty change * Hepatic AML * Inflammatory pseudotumor of the liver * Lipoma Malignant * Hepatic mets o Colorectal o Treated breast o PNET o RCC o Thyroid o Melanoma o Choriocarcinoma * HCC especially in cirrhotic liver * Cholangiocarcinoma

Answer 202

**Facial angiofibromas** MEN type 3 is a non-inherited syndrome primarily composing medullary thyroid carcinoma, phaeochromocytomas and mucosal neuromas of the gastro-intestinal tract. Other features include prognathism, marfanoid appearance and cutaneous neuromas. Facial angiofibromas are associated with MEN type 1 and occur in greater than 80% of cases.

Answer 203

**Gastrinoma** Pancreatic adenocarcinoma is a hypovascular lesion. Macrocystic adenoma is also hypovascular and is only rarely found in the head of the pancreas, with a predilection for the tail. The differential therefore lies between insulinoma and gastrinoma. Although both CT and MR imaging characteristics are similar, the majority of insulinomas are less than 1 cm in size, whereas gastrinomas tend to be larger at presentation with an average size of approximately 3 cm. Gastrinoma is associated with peptic ulceration and Zollinger–Ellison syndrome.

Answer 204

**Phaeochromocytoma** Features of MEN2A include parathyroid hyperplasia, medullary T cell carcinoma of the thyroid, and phaeochromocytoma. MEN2A may also be associated with carcinoid and Cushing’s.

Answer 205

**1.5 cm arterially enhancing, solid mass in the head** Insulinomas are rare tumours of the islet cells of the pancreas, which present at an early stage with hypoglycaemic episodes. Diagnosis is made biochemically, by demonstrating fasting hyperinsulinaemia, and the main purpose of imaging is to detect and localize accurately the tumours, which tend to be small (,2cm) at presentation. Tumours may occur anywhere in the pancreas, with 2–5% in an ectopic location. CT is considered the ﬁrst-line investigation, but newer techniques such as MR and functional imaging are being increasingly used. On CT, insulinomas are typically solid and highly vascular, and are best visualized on arterial phase imaging, when they demonstrate marked enhancement.

Answer 206

**Predilection for body/tail of pancreas** Glucagonomas are predominantly in pancreatic body/tail, mean size 6.4cm and hyper-vascular. Somatostatinomas are predominantly in pancreatic head/duodenum of ampulla of Vater.

Answer 207

**VIPOMA** are usually in the pancreatic body/tail (75%). Extra-pancreatic locations include retroperitoneal ganglioblastoma, phaeochromocytoma, lung, neuroblastoma (in children). 50- 80% of VIPOMAs undergo malignant transformation.

Answer 208

**CT of the abdomen** Necrolytic migratory erythema is a rare dermatological condition with a strong association with glucagonoma, an islet-cell tumour of the pancreas derived from alpha cells. Over 70% of patients with glucagonoma demonstrate the condition, and they may also complain of weight loss, diarrhoea, and diabetes. The association is considered strong enough to warrant thorough investigation for pancreatic malignancy. Glucagonomas typically occur in the pancreatic body or tail and are large (2.5–25cm) hyper-vascular tumours with solid and necrotic components. They have a high rate of malignant transformation, and around 50% of patients have liver metastases at the time of diagnosis.

Answer 209

The most likely primary tumour leading to a metastatic deposit to the pancreas is **renal cell carcinoma**. These metastases are usually solitary and heterogeneously enhancing masses with increased attenuation relative to the pancreas.

Answer 210

**CT scan after 3 days showing necrosis and fluid collections** The Balthazar CT staging system grades pancreatitis based on the presence of gland enlargement and/or fluid collections, as well as the presence of necrosis involving <30%, 30– 50% or >50% of the gland. This has been shown to be a more accurate predictor of severity of pancreatitis and morbidity than the Ranson or Acute Physiology and Chronic Health Evaluation II (APACHE II) criteria. This staging system is, however, most accurate when carried out after 48 hours, as the degree of pancreatic necrosis may not be apparent before this.

Answer 211

**Ultrasound scan within 24 hours** CT is only indicated as an investigation in cases of pancreatitis with severe prognostic indicators. This patient’s Ranson score is 1, which indicates a mild episode of pancreatitis and therefore CT is not indicated. ERCP was formerly contraindicated in pancreatitis but is now recognized as a treatment for obstructing stones in the ampulla that are causing the pancreatitis. Ultimately further investigations can be directed based on the ultrasound ﬁndings. ## Footnote Pancreatitis [Core Radiology] Pancreatic parenchymal phase is later arterial (40s) is the most sensitive timing to detect subtle low attenuation of necrosis. CT imaging is not indicated in patients with clinical diagnosis of mild acute pancreatitis, especially if they are improving. CT imaging may be negative or show a mildly oedematous pancreas in these cases. Acute pancreatitis Causes: alcohol, stones, ERCP Balthazar grading system: 14% MT for D, E (fluid collection is poor prognostic indicator) A: Normal-appearing pancreas B: Focal or diffuse pancreatic enlargement C: Mild peripancreatic inflammatory changes D: Single fluid collection E: Two or more fluid collections CT severity index (STSI) o Assigns 0–4 points for Balthazar A–E o Adds 0–6 points for necrosis to create a total score from 0-10. [ 0 points: 0% necrosis, 2 points: <30% necrosis, 4 points: 30–50% necrosis, 6 points: >50% necrosis] Pancreatic and peripancreatic complications: 1. Pancreatic necrosis: a. Focal area of non-enhancing pancreatic parenchyma b. Best seen 48-72 hours, late arterial phase c. Risk for infection and severe morbidity. 2. Fluid collections: Peripancreatic fluid may resolve or may evolve either into peripancreatic abscess or pseudocyst. 3. Pseudocyst: A pancreatic pseudocyst is a collection of pancreatic enzymes and fluid enclosed by a fibrous wall lacking an epithelial lining. The fibrous wall usually takes about 4–6 weeks to mature. 4. Pancreatic abscess: a. Thicker, more irregular wall to pseudocysts b. Gas locules Extra-pancreatic complications: 1. Extra-pancreatic pseudocyst a. nearly anywhere below the diaphragm. b. An intra-splenic pseudocyst → intra-splenic haemorrhage. 2. Perihilar renal inflammation, which may lead to venous compression or thrombosis. 3. Bowel involvement, especially of the transverse colon. 4. Vascular Complications a. Arterial bleeding from erosion into the splenic artery. b. Pseudoaneurysm of splenic artery c. Porto-splenic thrombosis, which may lead to portal hypertension. Chronic pancreatitis Causes: alcohol, pancreatic divisum. Calcification in the distribution of pancreatic duct. Autoimmune pancreatitis Causes: Sjogren, IgG 4 Diffuse sausage shaped enlargement of pancreas. Can be focal – mimics tumour, but no ductal dilatation. Groove pancreatitis Uncommon, young men, heavy drinkers Focal pancreatitis of the groove between the head of the pancreas, duodenum, and common bile duct. Histology: Fibrosis in the pancreaticoduodenal groove. Imaging: Duodenal thickening, stenosis, cystic changes of duodenal wall. Differential: Adenoma head of pancreas.

Answer 212

**Groove pancreatitis** This is a rare form of chronic pancreatitis. It occurs due to inflammation in the pancreatico- duodenal groove, the potential space between the pancreas, duodenum, and common bile duct. The clinical manifestations are primarily due to duodenal and biliary obstruction. The small cystic lesions in the duodenal wall refer to cystic dystrophy of the duodenum, which can be associated with groove pancreatitis. Autoimmune pancreatitis generally shows a diffusely enlarged gland with loss of lobular architecture, a ‘sausage’ shape, and a peripheral ‘rind’ of hypoattenuation. There is usually a non- dilated or diffusely narrowed pancreatic duct and a distal biliary stricture. Hereditary pancreatitis has a young age of onset of typical features of pancreatitis, with at least two acute attacks without an underlying cause. Pancreas divisum associated pancreatitis is seen in young or middle-aged patients with recurrent acute pancreatitis or chronic relapsing pancreatitis. MRCP or ERCP are optimal for the diagnosis of the lack of communication between the ventral and dorsal pancreatic ducts. Although ectopic pancreatic tissue is a proposed cause of groove pancreatitis, the ectopic or heterotopic tissue is most seen in relation to the gastric wall.

Answer 213

**Presence of gas bubbles** The only reliable feature on imaging indicating an infected collection is the presence of gas bubbles. All three types of pancreatic necrosis organised central gland and extra-pancreatic are associated with post-necrotic fluid collection. Necrotic pancreatitis becomes infected in 40- 70%, most often with gram negative enteric bacteria.

Answer 214

**Lipomatous pseudohypertrophy of the pancreas.** The history is one of undiagnosed cystic fibrosis (CF), with respiratory disease and pancreatic exocrine dysfunction. Pancreatic involvement in CF initially produces inhomogeneous attenuation, then low attenuation, and then complete fatty infiltration and replacement. Microcysts may develop and some of these may become small macroscopic cysts demonstrable with CT. There may be scattered calcifications. On ultrasound, there is increased diffuse echogenicity in keeping with fatty infiltration and fibrosis. CF is a major cause of pancreatic exocrine failure in childhood. Pancreatic abnormalities are seen in 85–90% of CF patients. However, the disease progresses to pancreatitis in less than 1% of CF patients. It predisposes to pancreatic cancer. Shwachman–Diamond syndrome is a rare congenital disorder characterized by pancreatic exocrine insufficiency, bone marrow dysfunction, and skeletal abnormalities. Patients usually present in infancy or early childhood with malabsorption and recurrent infections. Imaging reveals pancreatic lipomatosis.

Answer 215

**Fibrosing colonopathy** Fibrosing colonopathy is a condition causing progressive submucosal ﬁbrosis predominantly affecting the proximal colon. It was ﬁrst described in 1994 in children with cystic ﬁbrosis taking high-dose lipase supplementation to relieve the symptoms of exocrine pancreatic insufﬁciency. It causes stricturing and longitudinal shortening of the right colon, and patients present with obstruction. Overall, the gastrointestinal tract is affected in 85–90% of patients with cystic ﬁbrosis, and all the above pathologies may occur, though only ﬁbrosing colonopathy is associated with high-dose lipase supplementation

Answer 216

**Supportive therapy** Injury to the pancreas is relatively uncommon, occurring in less than 2% of blunt abdominal trauma patients. Direct signs of pancreatic injury at CT include laceration, transection, enlargement, and inhomogeneous enhancement. Secondary signs include peripancreatic fat stranding and fluid collections, haemorrhage, and thickening of the anterior pararenal fascia. The management of pancreatic trauma depends on the integrity of the pancreatic duct. If it is intact, the treatment is supportive and expectant. If the duct is disrupted, surgery or stenting at ERCP is required. Although CT may not always directly demonstrate the pancreatic duct, the likelihood of ductal injury may be inferred from secondary signs. Wong et al. have devised a CT grading scheme, which is like the surgical classification of Moore. Grade A injuries comprise pancreatitis or superficial laceration (<50% pancreatic thickness), grade B1 is deep laceration (>50% pancreatic thickness), grade B2 is transection of the pancreatic tail, grade C1 is deep laceration of the pancreatic head, and grade C2 is transection of the pancreatic head. Grade A injuries spare the duct and are usually seen with an intact duct by surgical grading. Grade B and C injuries correlate with duct disruption. MR pancreatography is an alternative to ERCP to assess the integrity of the pancreatic duct. The duct integrity cannot be reliably assessed by ultrasound, particularly in the context of recent trauma.

Answer 217

**Active arterial extravasation** In the evaluation of haemo-peritoneum by CT, attenuation values can help differentiate ascites, unclotted blood, active bleeding, and haematoma. Blood usually has a higher measured attenuation than other body ﬂuids, but its appearance depends on the age, extent, and location of haemorrhage. Unclotted blood has an attenuation value of 30–45 HU, but this may be lower in patients with a lower serum haematocrit and if the haemorrhage is more than 48 hours old. Clotted blood has an attenuation value of 45–70 HU, and identiﬁcation of the area of highestattenuation haematoma (sentinel clot) on CT indicates the site of bleeding. Active arterial extravasation is seen as an area of higher attenuation resembling that in the aorta, ranging from 85 HU to 370 HU. It may be surrounded by lower-attenuation haematoma. This ﬁnding indicates the need for urgent embolization or surgical treatment.

Answer 218

**Splenunculus** Splenunculus is most likely and is often seen incidentally. It is much more common than splenosis and is more likely to occur at the splenic hilum than splenosis. A splenunculus, or accessory spleen, is present in up to 30% of people and is most often located near the splenic hilum but can occur anywhere in the abdomen. Spleno-gonadal fusion is a recognised entity whereby the accessory splenic tissue is attached to the left ovary or testis. Splenosis occurs following trauma, whereby splenic tissue auto transplants elsewhere in the abdomen, and can also implant above the diaphragm if associated with diaphragm rupture. A wandering spleen denotes abnormal mobility of the spleen on long peritoneal ligaments.

Answer 219

**Accessory spleen (splenunculus)** Accessory spleen (splenunculus) is seen in 10–30% of the population and results from developmental failure of fusion of the mesodermal buds that form the spleen. They appear as small (usually ,10 mm), well-deﬁned masses with identical attenuation and enhancement characteristics as the spleen and are most commonly located near the splenic hilum. Following splenectomy for haematological disorders, an accessory spleen may undergo hypertrophy and result in recurrence of the original disorder. Regional lymph nodes from colorectal cancer extend along the course of the main vessels supplying the segment of bowel. Wandering spleen refers to a normal spleen positioned in an abnormal location within the abdomen due to laxity of the splenic ligaments. Splenic artery aneurysms are focal dilatations of the splenic artery, which may be intra- or extra-splenic and are frequently calciﬁed. Poly-splenia is a rare congenital disorder associated with situs ambiguous and characterized by multiple small spleens usually in the right abdomen.

Answer 220

**Normal arterial-phase enhancement** CT pulmonary angiogram is performed during pulmonary arterial phase enhancement. During arterial phase enhancement, variable rates of ﬂow through the splenic parenchyma result in heterogeneous enhancement, which may appear as alternating bands of high and low attenuation, or give the impression of irregular, low-density mass lesions. Enhancement becomes homogeneous in the portal venous phase. Splenic infarction is the most common cause of (true) focal splenic defects, and typically appears as single or multiple, wedge-shaped, peripheral, low-attenuation defects. Clefts in the splenic contour are common normal variants, appearing as smoothly contoured, medially located defects, and should not be mistaken for lacerations. Splenosis is the implantation of splenic tissue in ectopic sites following traumatic rupture or splenectomy, and appears as multiple, small, homogeneous, enhancing masses that may mimic peritoneal deposits. Spontaneous splenic rupture is rare, though it may be delayed following trauma or be associated with splenomegaly. Appearances may include low-density, linear, parenchymal lacerations and areas of mottled parenchymal enhancement representing contusions.

Answer 221

**Previous trauma** Splenic cysts are classiﬁed into two major subtypes: true cysts and false cysts (post-traumatic pseudocysts). This differentiation is based on the presence or absence of an epithelial lining. They cannot be distinguished on imaging. On CT as both usually appear well-deﬁned and of ﬂuid density. True cysts, which constitute approximately 20% of all splenic cysts and show an epithelial lining, are further divided into non-parasitic cysts and parasitic subtypes. Non-parasitic, true cysts, primarily known as epidermoid cysts, are congenitally derived from peritoneal mesothelium and represent only 2.5% of all splenic cysts. Most true cysts are related to parasitic infection, usually hydatid disease. False cysts, also known as post-traumatic pseudocysts, lack an epithelial lining and are considered to represent the end stage of a previous intrasplenic hematoma. They account for up to 80% of all splenic cysts. Patients may report a history of trauma to the left upper quadrant, but up to 30% of patients do not recall any association with such an event. More rarely they may be the result of previous infarction or infection. True cysts are more likely to have slight wall trabeculation and thin peripheral septation (up to 86%), whereas false cysts are more likely to have mural calciﬁcation (up to 50%). Isolated splenic lymphangioma is uncommon in adults, usually being diagnosed in childhood. It usually appears as thin-walled, well-deﬁned masses of low attenuation, without enhancement. They may have curvilinear peripheral mural calciﬁcation.

Answer 222

**Post traumatic (false) cyst** Approximately 80% of all splenic cysts are post-traumatic cysts (also known as false cysts or non-pancreatic pseudocysts), which represent the cystic end stage of trauma, infection, or infarction. They are not true cysts, as they lack an epithelial wall. They often contain internal echoes from debris and cyst wall calciﬁcation. True cysts may be parasitic (echinococcal) or non-parasitic (epithelial). The spleen is involved in 0.9–8% of cases of echinococcal disease. Features include daughter cysts, and multiple internal dependent echogenic foci resulting in a ‘snowstorm’ sign. Epidermoid cysts are congenital cysts with the same appearance as post- traumatic cysts, but they are rarer, and rim calciﬁcation is less commonly seen. Pyogenic abscesses tend to appear as irregular hypoechoic areas on ultrasound scan, and hyperechoic gas bubbles may be visible. Intrasplenic pancreatic pseudocysts are seen in up to 5% of patients with pancreatitis

Answer 223

**Splenomegaly ** Although symptoms directly referable to the spleen are unusual, autopsy studies have demonstrated the spleen to be involved in 38–77% of patients with sarcoidosis. The commonest abnormality demonstrated on imaging is splenomegaly, occurring in up to 60% of patients. Multiple hypoattenuating nodules measuring up to 3cm may be seen distributed diffusely throughout the spleen in around 15% of cases and may occur in the absence of splenomegaly. The lesions appear hypointense on all sequences at MRI and are best seen on T1W or early phase, gadolinium-enhanced, T2W fat-suppressed sequences. Abdominal or systemic symptoms are more frequent in patients with nodular hepatosplenic sarcoidosis. Spontaneous splenic rupture in sarcoidosis has been described but is very rare. Capsular calciﬁcation and multiple cystic lesions are not features of the disease

Answer 224

**Chronic myeloid leukaemia** Splenomegaly is a relatively common finding in many different diseases, but massive splenomegaly always indicates underlying pathology. Although there is no unifying definition, it is often recognised to be enlargement of the spleen into the left lower quadrant of the abdomen or crossing the midline. All the options listed are causes of splenomegaly, however chronic myeloid leukaemia is the only listed cause of massive splenomegaly. Other causes of massive splenomegaly include Gaucher’s disease, malaria, myelofibrosis, schistosomiasis and Leishmaniasis.

Answer 225

**Renal cell carcinoma.** All the other tumours are more likely to be FDG avid than renal cell carcinoma.

Answer 226

**Whilst the appearances are consistent with a laceration and subcapsular haematoma, radiological ﬁndings are not reliable in determining the need for a laparotomy.** Splenic injuries can be graded 1–5 (American Association of Trauma Surgeons). Grade 1 is a subcapsular haematoma that involves <25% of the splenic surface or a laceration <1cm deep. Grade 2 is a haematoma that involves 25–50% of the surface or a laceration up to 3cm deep. Grade 3 is a haematoma involving >50% of splenic surface or 10 cm in length or a laceration greater than 3 cm into the parenchyma. Grade 4 is a laceration extending into the hilum that devascularizes up to 25% of the spleen. Grade 5 is a shattered spleen, with multiple lacerations or a spleen avulsed from its vascular bed. Radiological ﬁndings do not correlate well with requirement for laparotomy in the more minor splenic injuries. Clinical assessment is of more value, with surgery only indicated in unstable patients. The value of radiology is in detecting other injuries and in quantifying the amount of the haematoma due to the risk of delayed splenic rupture in more severe injuries.

Answer 227

**Ipsilateral rib fractures** All are potential associated injuries and should be actively searched for in the context of blunt abdominal trauma. Rib fractures are found in up to 50% of patients with splenic injuries and as such are the most common association. The left kidney is injured in 10% of patients with splenic injury, and diaphragm rupture is even rarer. Diaphragm rupture may be difficult to appreciate on axial slices and may be more evident on coronal reformats.

Answer 228

**The size of tumour at diagnosis is related to the risk of metastatic spread** Carcinoid is the 33% tumour, as * 33% occur in the small bowel, (75% metastatic disease) * 33% are multiple, * 33% are malignant, and * 33% are associated with a second malignancy. Appendiceal carcinoid accounts for * 50% of all carcinoids and * 33% are symptomatic at presentation. * 7% of metastatic disease The size of the tumour at diagnosis is related to the risk of metastatic spread, * 2% if the lesion is <1 cm, * 85% if the lesion is > 2 cm.

Answer 229

**Carcinoid tumour** The commonest cause of small bowel obstruction in adults is adhesions, which are diagnosed on CT when there is an abrupt calibre transition without an associated mass, surrounding inﬂammatory changes or bowel wall thickening. Carcinoid tumours comprise 25% of all tumours of the small bowel. They are commonly asymptomatic but may present with pain or obstruction, or with carcinoid syndrome in 7% of patients. Most occur in the ileum, and typical appearances are of a calciﬁed mass with surrounding desmoplastic reaction, retraction of the mesentery and thickening of surrounding loops of bowel. Small bowel obstruction complicates Crohn’s disease in approximately 15% of patients, due to thickening and submucosal oedema of the bowel wall. Previous irradiation may result in adhesions and ﬁbrotic changes in the mesentery that can cause bowel obstruction. Lymphomatous involvement of the small bowel causes circumferential bowel wall thickening, but this rarely results in obstruction. ## Footnote GI carcinoid [STATdx] Def: Well-differentiated neuroendocrine tumour from GI, can also from lung and GU Site: * Midgut carcinoids (jejunoileal) (45%) o 90% arise in ileum, within 60 cm of ileocecal valve o Account for most cases of carcinoid syndrome * Gastric carcinoids (7%) o Gastrinoma (Zollinger-Ellison or MEN1 syndrome) o Pernicious anaemia or atrophic gastritis * Appendiceal carcinoids (16%) o Most common tumour of appendix o Usually found incidentally at appendectomy * Colorectal (31%) o Usually asymptomatic until large * Carcinoid syndrome = metastatic spread to liver o Spectrum of symptoms (flushing, diarrhea, asthma, pain, right heart failure) o Symptoms require systemic circulation of hormonal factors produced by carcinoid Imaging: * Solitary, enhancing distal ileal mass with mesenteric metastases (More difficult to detect primary than metastatic foci) * Mesenteric mass due to direct invasion or nodal metastasis o Calcification is common o Spiculated with stellate pattern o Tethering, fixation, retraction of small bowel loops o Encasement and narrowing of mesenteric vessels * Liver metastases: Hyper vascular, Hyperechoic o Intense enhancement in arterial phase o Washout on portal venous and delayed phases * In-111 octreotide or somatostatin receptor scintigraphy Less sensitive but specific * Gallium-DOTATATE PET/CT: Localization, targeted therapy Top Differential Diagnoses: * Sclerosing mesenteritis Infiltrated jejunal mesentery (not ileal) and usually larger * Gastrointestinal stromal tumour Hyper-vascular tumour, not associated with desmoplastic effect on mesentery

Answer 230

**Carcinoid tumour** Of the options listed, carcinoid tumour is the only primary tumour that typically causes hyper vascular liver metastases. Other causes of hyper vascular liver metastases are pancreatic islet cell tumours, phaeochromocytoma and renal cell carcinoma. Stomach, breast, lung and colon cancers are associated with hypo vascular liver metastases. Liver metastases from carcinoid tumours are more common with increasing size of the primary tumour. The incidence of metastases depends on the location of the primary tumour, where approximately 30% of carcinoids of the ileum metastasise compared to less than 5% of carcinoids of the appendix.

Answer 231

**Carcinoid tumour** These features are typical of carcinoid tumour. The desmoplastic reaction appears on CT as thickened mesentery in a radiating pattern away from the soft-tissue mass, with beading of the mesenteric vascular bundles.

Answer 232

**The stellate pattern is characteristic for carcinoid tumour**

Answer 233

**Carcinoid** **often appears as a bulbous swelling of the distal third of the appendix**, in contrast to adenocarcinoma which tends to involve the proximal third and causes diffuse thickening of the appendiceal wall.

Answer 234

**Small bowel mesentery** Desmoid tumours are non-malignant ﬁbrous tumours that have a particular association with FAP/Gardner syndrome. They may be locally inﬁltrative. On CT they are usually of homogeneous density but can have well-deﬁned or irregular margins. On MRI, the signal intensity on T1WI is similar to muscle and on T2WI their signal can be variable. Lower signal tumours on T2WI probably have a denser ﬁbrous component. Desmoid tumours in association with FAP/Gardner syndrome are most seen in the small bowel mesentery, followed by the abdominal wall. Intra-abdominal desmoid tumours can also occur in the retroperitoneum and pelvis, but these locations are more common in isolated desmoids.

Answer 235

**Sclerosing mesenteritis** This is a rare condition of unknown cause characterized by chronic mesenteric inflammation. It is most frequently seen in the sixth decade and more commonly in males than females. It is often associated with other inflammatory disorders such as retroperitoneal fibrosis, Riedel thyroiditis, and sclerosing cholangitis. Symptoms include abdominal pain, nausea, fever, intestinal obstruction or ischaemia, a mass, or diarrhoea. The CT findings can range from subtle increased attenuation in the mesentery to a solid soft-tissue mass. The mass may envelop vessels, but there may be preservation of fat around the vessels, the ‘fat halo’ sign. This finding may help distinguish sclerosing mesenteritis from other mesenteric processes such as lymphoma, carcinomatosis, or carcinoid tumour. Calcification may be present, usually in the central necrotic portion. Enlarged mesenteric or retroperitoneal lymph nodes may also be present. Lymphoma will not display calcification unless it has undergone treatment. Carcinoid can produce the appearance described, but the ‘fat halo’ sign favours sclerosing mesenteritis and the soft tissue in carcinoid usually has a surrounding desmoplastic reaction. Metastatic disease will not be confined to the root of the mesentery but will also involve the omentum or the surfaces of the liver, spleen, or bowel. Ascites is also common with carcinomatosis but is not associated with sclerosing mesenteritis. Mesenteric involvement in the case of desmoid tumours is more often seen in cases related to familial adenomatous polyposis syndrome or Gardner syndrome. They are usually large masses, measuring 15 cm or more at diagnosis. They do not typically contain calcification. ## Footnote Sclerosing Mesenteritis [STATdx] * Idiopathic inflammatory and fibrotic disorder of unknown aetiology affecting mesentery. * Symptoms o Acute abdominal pain o Bowel, urinary tract obstruction and bowel wall ischaemia in chronic phase * Histology o Mesenteric panniculitis o Mesenteric lipodystrophy o Retractile mesenteritis * Imaging o Acute ▪ Misty mesentery ▪ Thin pseudo capsule – 3 mm ▪ Cluster of mildly enlarged mesenteric lymph nodes. ▪ Usually left upper quadrant mesentery – root of jejunal mesentery ▪ Mesenteric vessels and nodes have halo of spared fat (fat ring or fat halo) o Chronic ▪ Discrete fibrotic soft tissue with desmoplastic reaction ▪ Stellate appearance with calcification within mass ▪ Encasement of mesenteric vessels (especially porto-mesenteric veins) with resultant collaterals – resultant narrowing and occlusion ▪ Small bowel wall oedema and mucosal hyperaemia as result of lymphatic/venous obstruction and ischemia ▪ Tethering of bowel loops can lead to bowel obstruction

Answer 236

**Mesenteric panniculitis** These CT findings are typical of mesenteric panniculitis. This is an idiopathic, indolent condition characterised by inflammation of the small bowel mesentery adipose tissue. Fibrosis can predominate, in which case the CT appearances are of an infiltrative soft-tissue mass with soft-tissue density strands radiating away from it. In this situation it has similar appearance to lymphoma, carcinoid or desmoid tumours or retroperitoneal fibrosis, and biopsy is required to differentiate. Mesenteric panniculitis often presents with non-specific symptoms such as abdominal pain, weight loss, nausea, vomiting and pyrexia, and is usually indolent and self- limiting.

Answer 237

**Increased density of mesenteric fat to 40-60 HU** An increased attenuation of mesenteric fat (typically 40-60HU) is typical in sclerosing mesenteritis on CT

Answer 238

**The left paracolic gutter communicates with the left subphrenic space.** There is no direct connection between these two spaces due to the phrenico-colic ligament. The rest of the statements are correct.

Answer 239

**Gastric ulceration** The anterior pararenal space extends between the posterior parietal peritoneum and the anterior renal fascia (Gerota’s fascia). It is bounded laterally by the lateral conal fascia.The pancreas, second and third parts of the duodenum, and ascending and descending colon are located within the anterior pararenal space, and disease in this space usually arises in these organs.The stomach is intraperitoneal.

Answer 240

**Pseudomyxoma retroperitonei** The displacement of the psoas muscle indicates that this mass is most likely retroperitoneal. Pseudomyxoma peritonei is a rare condition that is characterized by intraperitoneal accumulation of gelatinous material owing to the rupture of a mucinous lesion of the appendix or ovary, e.g. mucinous cystadenoma/cystadenocarcinoma. It may occur in the retroperitoneum, where it is caused by the rupture of a mucinous lesion in the retrocaecal appendix and fixation of the lesion to the posterior abdominal wall. Clinically, it results in abdominal pain and a palpable mass. At CT, it appears as a multi-cystic mass with thick walls or septa that displace and distort adjacent structures. Curvilinear or punctuate mural calcifications may also occur and are highly suggestive. Pancreatic pseudocysts usually occur in the peripancreatic space, but may occur in the abdomen, pelvis, or mediastinum. They are associated with the clinical findings of pancreatitis and elevation of serum amylase. A urinoma is an encapsulated collection of chronically extravasated urine. There is usually a history of trauma and an associated hydronephrosis. Haematomas are associated with trauma, coagulopathy/anticoagulants, or a ruptured abdominal aortic aneurysm. Chronic haematoma can result in low attenuation contents, but acutely the haematoma will have higher attenuation than pure fluid due to clot formation. Retroperitoneal liposarcoma is most commonly of a density between water and muscle (myxoid type). It may have a solid, mixed, or pseudo-cystic pattern on CT. There may also be macroscopic areas of lipid in well-differentiated liposarcomas. Patients present with abdominal pain, weight loss, a palpable mass, and anaemia.

Answer 241

**Cystadenocarcinoma of the appendix** The CT findings described are consistent with pseudomyxoma peritonei. This describes abdominal distension secondary to the accumulation of large quantities of gelatinous ascites. It is most caused by cystadenocarcinoma of the appendix in males and cystadenocarcinoma of the ovary in females. Surgical debulking and intraperitoneal chemotherapy may be offered as a treatment. Bowel obstruction is a frequent complication that may necessitate surgery.

Answer 242

**Scalloping of the liver edge** Pseudomyxoma peritonei is indicated by ascites and low attenuation masses. The ascites contains septae, which are the margins of mucinous nodules, typically scalloping the liver edge. Solid non-mucin-producing components cause soft tissue thickening of the peritoneal surface.

Answer 243

**Pseudomyxoma peritonei** Pseudomyxoma peritonei results from rupture of a benign or malignant mucin-producing tumour, most commonly of the appendix or ovary, but also of the pancreas, stomach, and colon. Typical ﬁndings are of large volume mucinous ascites, which appears on CT as very low attenuation (mucinous) ﬂuid collections in the omentum, mesentery, and peritoneal cavity, often loculated and containing curvilinear or punctuate calciﬁcations. A characteristic feature is scalloping of the contour of the liver and splenic margins, which distinguishes mucinous from serous ascites. Peritoneal metastases may also demonstrate loculated peritoneal ﬂuid collections, but there are typically nodular peritoneal densities and thickening of the greater omentum (omental cake). Peritoneal mesothelioma usually presents with thickened mesentery, omentum, peritoneum, and bowel wall, with a disproportionately small amount of ascites.

Answer 244

**All the above** All the findings are manifestations of von Hippel–Lindau (VHL) disease, which is a rare, autosomal dominant, multisystem disorder characterized by the development of multiple benign and malignant neoplasms. The clinical manifestations are broad and include central nervous system (CNS) and retinal hemangioblastomas, renal cysts and tumours, pancreatic cysts, and tumours, phaeochromocytomas, endolymphatic sac tumours, and epididymal cystadenomas. The diagnostic criteria for VHL include: (i) >1 CNS hemangioblastoma, (ii) one CNS hemangioblastoma + visceral manifestations of VHL, and (iii) any manifestation + known family history of VHL. The most common causes of death in VHL are renal cell carcinoma and neurologic complications of cerebellar hemangioblastomas. Genetic counselling and screening are important for early detection and treatment of VHL lesions. ## Footnote Von-Hippel-Lindau Syndrome [STATdx] * Autosomal Dominant * Comprises of o Hemangioblastomas – arise from and so abuts the pia surface ▪ Cerebellum (posterior half) ▪ Brainstem (posterior medulla) ▪ Spinal Cord (posterior half) o Ocular angioma – retinal detachment and haemorrhage o Endolymphatic sac tumours (ELSTs) – large temporal bone mass posterior to internal auditory canal near vestibular duct. o Clear cell RCC o Cystadenomas – Pancreas o Pheochromocytomas

Answer 245

**Pneumoperitoneum** Whilst uncommon, the appearances seen on plain film are consistent with massive pneumoperitoneum. The oval radiolucency is called the ‘football sign’ and arises due to free air collecting anterior to the intra-abdominal viscera. This sign is only seen in 2% of adults with pneumoperitoneum due to the large quantities of air required to produce it. It is much more common in infants who may present at a later stage. The opacity in the right upper quadrant is produced by air outlining the falciform ligament, which again is a sign of pneumoperitoneum. Causes of perforation in this age group include trauma, intussusception, and complications of Meckel’s diverticulum.

Answer 246

**Perforation anterior wall duodenal ulcer** The commonest cause of a free intraperitoneal perforation is an anterior wall duodenal ulcer. However, free peritoneal air is only apparent on an erect chest radiograph in 60% of perforated duodenal ulcers. Possible causes include sealing of the perforation, adhesions preventing the gas reaching the subphrenic space or insufﬁcient time being allowed for gas to collect under the diaphragm. Anterior wall gastric ulcers also perforate into the peritoneal cavity but are a less common cause of pneumoperitoneum. Posterior wall duodenal and gastric ulcers perforate into the lesser sac or retroperitoneal region rather than the peritoneal cavity. Perforated appendix and diverticulitis may produce localized collections of extraluminal gas, but pneumoperitoneum is rare.

Answer 247

**Left lateral decubitus** An erect chest radiograph is best for demonstrating a small pneumoperitoneum, enabling the identiﬁcation of as little as 1ml of free intraperitoneal gas. It is superior to an erect abdomen, as the X-ray beam penetrates the diaphragmatic region almost tangentially, whereas, in an erect abdomen, the divergent beam penetrates this area obliquely. However, if the patient is too unwell to sit erect, the most appropriate projection is a left lateral decubitus abdominal radiograph, performed with the patient lying on the left side, using a horizontal X-ray beam. In this position, air will preferentially leave a perforated duodenal or antral ulcer, and any free gas in the lesser sac will enter the main abdominal cavity. The supine abdominal radiograph may demonstrate free gas in about 56% of patients with pneumoperitoneum. Characteristic features include gas outlining both inner and outer walls of a bowel loop (Rigler’s sign), triangular collections of gas between bowel loops, and outlining of the falciform ligament and other peritoneal reﬂections by free gas. The supine chest radiograph is not useful in the detection of free intraperitoneal gas.

Answer 248

**Angiodysplasia** The typical angiographic feature of a Meckel’s diverticulum is presence of the vitelline artery. Meckel’s diverticulum also typically (although not exclusively) presents in younger patients. With diverticulosis, radiation enteritis and polyps, one might expect an abnormal barium enema, and in addition these angiographic features are not typical. Angiodysplasia is the second most common cause of gastro-intestinal bleed in the elderly population after diverticular disease. It is due to dilatation of the submucosal vessels and occurs most commonly on the right side of the colon. Angiographic features include visualisation of a cluster of vessels on the antimesenteric border, early filling of the ileocolic vein in the arterial phase and delayed emptying of the same vein.

Answer 249

**Tailgut cyst** Tailgut cysts or cystic hamartomas are presacral, multilocular, mucous-secreting cysts found distal to the normal embryonic termination of the hindgut. Small cysts may be asymptomatic, but larger cysts may present with rectal pain or bleeding, constipation, anal fistulae or recurrent rectal abscesses. A long and tail-like coccyx is often associated and can help distinguish between many other cystic lesions in this region. Malignant transformation is a complication, most commonly adenocarcinoma. Duplication cysts are most often unilocular unless complicated by haemorrhage or infection, a meningocele is likely to arise from the sacral foramina, piercing the presacral fascia, and dermoid tumour would be expected to contain fat or layering of contents as seen in dermoid tumours in other locations.

Answer 250

**Segmental omental infarction** Segmental omental infarction is the most likely cause and most commonly affects the right half of the greater omentum. It mimics surgical pathology such as appendicitis. High attenuation streaks in the omental fat with apparent ‘mass effect’ in the absence of any other findings is suggestive of the diagnosis. Point tenderness over the specific area of CT abnormality is often discovered. Management is conservative.

Answer 251

**Reported in up to 5% of upper GI fluoroscopic studies** Common acquired outpouchings of the mucosa and submucosa located along the medial wall of the duodenum within 2cm of the ampulla of Vater. 25% arise from D3/4. Reported in 1-5% of upper GI fluoroscopic studies.

Answer 252

**B-D are cases of irregular and thickened distal folds in nondilated small bowel**

Answer 253

**A double layered wall** An inflamed Meckel’s diverticulum can be difficult to distinguish from a duplication cyst in the terminal ileum. However, a characteristic double-layered wall is seen in duplication cysts, whereas the other features are more often found in an inflamed Meckel’s diverticulum.

Answer 254

**CT angiography** Several imaging methods are available for use in those patients in whom endoscopy fails to detect the source of bleeding in gastrointestinal haemorrhage. Radionuclide imaging is non- invasive and very sensitive, detecting bleeding rates as low as 0.1–0.5ml/min. Images are acquired over several hours, enabling detection of intermittent and venous bleeding, but anatomical localization can be insensitive and variable. Conventional angiography is invasive and requires active bleeding at the time of both imaging and contrast injection. Higher bleeding rates of 0.5–1ml/min are required, and motion artefact from bowel peristalsis may be problematic, but it provides superior localization of the bleeding site and options for therapeutic intervention. However, CT angiography is advocated as the most appropriate investigation, due to its wide availability, minimal invasiveness, and high sensitivity, detecting bleeding rates as low as 0.3ml/min in animal models. In addition, it enables assessment of a pathological lesion causing bleeding, which may be helpful in planning further management.

Answer 255

**Prior administration of Cimetidine** Cimetidine, a histamine H2 -receptor antagonist, may be used to increase uptake of [ 99m Tc] pertechnetate by inhibiting its secretion from gastric mucosa. Pentagastrin and glucagon have also been used to improve visualization, by stimulating uptake and decreasing peristalsis respectively. Procedures such as colonoscopy and use of laxatives should be avoided prior to the scan, as they may cause mucosal irritation. Potassium perchlorate should not be used to block thyroid uptake, as it also blocks uptake of pertechnetate by the gastric mucosa. The patient normally fasts for 3–4 hours and voids prior to the study, as a full stomach or bladder may obscure an adjacent Meckel’s diverticulum. Barium studies should be avoided for 3–4 days prior to the study, as attenuation by the barium may hamper interpretation

Answer 256

**Non-ionic, iso-osmolar, dimeric** Modern water-soluble, iodinated, intravenous contrast media are based on the six-carbon ring structure tri-iodobenzoic acid. Earlier contrast agents were ionic and high-osmolar, but the toxicity of these agents prompted further development. To decrease osmolality while maintaining an acceptable iodine concentration, the ratio between the number of iodine atoms and the number of particles in solution has been decreased either by combining two tri- iodinated benzene rings or by producing compounds that do not ionize in solution, or, more recently, by both methods. The most recent agents such as iodixanol (Visipaque) and iotrolan (Isovist) are non-ionic dimers with six iodine atoms per molecule in solution, enabling satisfactory iodine concentrations to be obtained at iso-osmolality.

Answer 257

**Uptake in large bowel** Radiolabelled white cell imaging is used for detection of infection and inﬂammation. Images reﬂect the distribution of white blood cells within the body and localize areas of infection or inﬂammation. Imaging is usually performed at 18–24 hours, by which time blood pool activity is normally no longer present, and the most intense uptake is seen in the spleen, followed by the liver and then the bone marrow. Imaging is also usually performed at 2–6 hours for investigation of suspected inﬂammatory bowel disease, as sloughed inﬂamed cells may move distally and provide misleading information as to the affected site if only imaged at 24 hours. Physiological diffuse lung uptake may be seen in the ﬁrst 4 hours due to cellular activation from in vitro cell manipulation, but normally decreases after this. Thymus activity may be seen normally in children. Bowel and genitourinary activity are not normally seen, and gastrointestinal activity is always abnormal. In general, focal activity outside the normal white cell distribution, which is greater than that of the spleen, suggests the presence of an abscess. Activity equal to that of the liver indicates a signiﬁcant inﬂammatory focus. Activity less than that of the bone marrow suggests a low-level inﬂammatory response.

Answer 258

**Unidimensional (long axis dimension)** The WHO response criteria were devised in 1981 to standardize the criteria used for measuring therapeutic response in cancer patients. These criteria set out deﬁnitions of complete response, partial response, no change, and progressive disease, based upon bidimensional measurements of tumour lesions in the axial plane. The product of the longest diameter multiplied by the greatest perpendicular diameter is calculated for each measurable lesion, and the sum of these products is used to determine treatment response. The RECIST criteria were introduced in 2000 and were designed to be used in clinical trials. The criteria involve classifying the disease burden into measurable and non-measurable disease, followed by selection of up to 10 representative target lesions. The sum of the long axis dimension of the target lesions in the axial plane is used to determine the ﬁnal response category. Potential concerns about the use of the RECIST criteria include possible confusion arising when lymph node measurements are performed using the short axis dimension and the increased workload involved for the radiologist.

Answer 259

**65-70 seconds** For a standard, single-slice, spiral CT of the abdomen and pelvis in a single breathhold, 100– 150ml of 300mg/ml iodine intravenous contrast medium should be administered at 3–4ml/s. For a portal phase examination, image acquisition should begin 65–70 s after commencement of the injection. ## Footnote Fundoplication Procedure: the fundus of the stomach is wrapped posteriorly (or less commonly anteriorly) around the distal oesophagus and lower oesophageal sphincter. Aim: to augment the lower oesophageal sphincter, providing compression to minimize reflux Types: 1. Nissen (360 posterior wrap) 2. Toupet (270 posterior wrap) 3. Dor (180 anterior wrap) To check on CT: the wrap should be below the diaphragmatic hiatus. Complications: 1. High grade oesophageal hold up – may need endoscopic balloon dilatation. 2. Wrap migration/ Slippage – distally to wrap the stomach, due to failure of sutures holding the wrap to the oesophagus. Sudden post-operative deterioration. Very dilated fundal bubble. Requires corrective surgery. 3. Intra-thoracic wrap herniation – up to 30% at 1 year, not always symptomatic, 70% para-oesophageal type (normal GOJ position) and 30% sliding type (proximal migration of GOJ) 4. Fundoplication dehiscence – no evidence of surgery found Surgery for Hiatus hernia 1. Collis gastroplasty – use stapled cardia to form distal oesophagus, use if there’s oesophageal shortening seen in Ba swallow. 2. Normal hernia repair using mesh. 3. Correction of volvulus if present.

Gastro-intestinal System Flashcards

(283 cards)