Paed Flashcards

Question

A 7-year-old girl with repeated chest infections and chronic cough presents with another episode of acute exacerbation. She is known to have raised sodium and chloride in her sweat. Which of the following features is least likely on an HRCT of her chest? [B2 Q41] a. Cylindrical bronchiectasis b. Centrilobular emphysema c. Segmental/subsegmental atelectasis d. Branching intrabronchial soft tissue e. Hilar lymphadenopathy

Answer 1

**Centrilobular emphysema** This is a feature of cystic fibrosis. Centrilobular emphysema is uncommon; para-septal emphysema is more typical.

Answer 2

**Reticulonodular changes in mid-zones** Langerhans’ cell histiocytosis typically shows **reticulonodular changes in the mid and upper zones**, often **progressing to cysts and honeycombing** **Sparing the costophrenic angles**

Answer 3

**Cavitation** Bacterial pneumonia can cause lobar consolidation or broncho-pneumonia, which may cavitate, while viral pneumonia typically affects airways and peri-bronchial tissues. Cavitation is uncommon in viral pneumonia.

Answer 4

No further investigation The mass is a normal thymus, commonly visible in children up to 2 years. It often has a characteristic triangular "sail sign" appearance with a rippled "wave sign" border.

Answer 5

**Foreign body aspiration** This scenario is characteristic of foreign body aspiration, which often affects the lower lobes, with the right being most common. Lucency and air trapping are typical findings.

Answer 6

**Mucus plugging** **Mucus plugging is a hallmark of cystic fibrosis** and is not seen in Williams–Campbell syndrome, which is characterized by cystic bronchiectasis and bullous changes.

Answer 7

**Round pneumonia** Round pneumonia is common in children and presents as a well-defined round opacity on the chest radiograph, often resolving rapidly with treatment.

Answer 8

**Pulmonary valve function**. As a rule, pre-operative imaging of paediatric cardiac malformations focuses on the morphology, to allow accurate characterization of the abnormality pre-operatively. Post-operative imaging focuses more on function, to assess the success of the treatment given and need for further intervention. With regard to a corrected tetralogy of Fallot, the situs will be known, and the ventricular septum assessed and usually repaired at surgery. A graft between the systemic venous system and pulmonary artery is a feature of a Fontan/Glenn procedure and these are most carried out for tricuspid atresia, not tetralogy of Fallot. Assessment of the pulmonary valve, along with right ventricular function, is essential in this post-operative patient, as re-stenosis of the pulmonary valve or progressive right ventricular impairment are associated with increased morbidity.

Answer 9

**Situs inversus**. The primitive truncus is a midline structure that persists to a degree in truncus arteriosus abnormality. During normal development, the truncus divides into the aortic and pulmonary trunks, which then undergo 150° anticlockwise rotation. In situs inversus, there is 150° clockwise rotation. Transposition of the great arteries (TGA) is characterized by 30° rotation, anticlockwise in D-TGA and clockwise in L-TGA. Double-outlet right ventricle displays 90° anticlockwise rotation.

Answer 10

**Pulmonary valve hypoplasia with a VSD and overriding aorta.** These are the features of **Tetralogy of Fallot**. Even in the absence of radiology, this represents the **most common** form of congenital **cyanotic** heart disease. To help characterize congenital heart disease there are several features to note on the radiograph as well as clinically. The presence of cyanosis excludes coarctation, which does not cause cyanosis. **Truncus arteriosus (and total anomalous pulmonary venous return (TAPVR))** are associated with **increased pulmonary flow, not reduced**, as present in this case. Pulmonary valve atresia with an intact ventricular septum does have reduced pulmonary flow but would present earlier than four days and the heart is typically grossly enlarged, as in this anomaly there is no forward flow of blood out of the right ventricle. **D-transposition of the great arteries** is classically described as giving an **egg-on-a-string appearance** due to the narrowed superior mediastinum caused by the abnormal rotation of the great vessels. This appearance is seldom seen as D-transposition presents early with cyanosis and is surgically corrected. The most common CXR appearance in an infant is a normal CXR. The pulmonary vascularity on the radiograph is either normal or increased, not decreased.

Answer 11

**Total anomalous pulmonary venous return (TAPVC)** VSD and PDA will both result in pulmonary plethora and distress but are left-to-right shunts and acyanotic. Pulmonary stenosis results in pulmonary oligaemia and may or may not be cyanotic depending on the presence of an intracardiac defect with shunt reversal. Tetralogy of Fallot is a congenital cyanotic heart disease with pulmonary oligaemia unless associated with the development of aorto-pulmonary collaterals. Apart from TAPVC, the admixture lesions such as truncus arteriosus, tricuspid atresia, transposition of great vessels, single ventricle and common atrium are some other causes of cyanosis with pulmonary plethora. **Cyanotic + pulmonary plethora:** TAPVR, Truncus, Transposition, Tricuspid Atresia. **Cyanotic + Pulmonary oligaemia:** TOF **Acyanotic + Pulmonary plethora:** VSD, PDA

Answer 12

**Aberrant left pulmonary artery**. Pulmonary sling Double aortic arch compresses the trachea anteriorly and the oesophagus posteriorly. Aberrant right subclavian (with a left-sided aortic arch) causes posterior indentation of the oesophagus, but no indentation of the trachea. An identical appearance is seen on the lateral view with a right-sided aortic arch and an aberrant left subclavian. Aberrant left pulmonary artery commonly presents any time up to early childhood, with stridor, wheezing, recurrent infections, and feeding problems being amongst the most common symptoms. It can be associated with a PDA or ASD.

Answer 13

**Partial anomalous pulmonary venous return (PAPVR)**. This most commonly involves the right superior pulmonary vein, but in this case involves the inferior vein. This condition may remain asymptomatic for several years, depending on the amount of blood that returns anomalously. PAPVR can drain into the superior vena cava (SVC), right atrium, or IVC on the right and into the brachiocephalic vein or coronary sinus on the left. Scimitar syndrome is a subtype of PAPVR that is associated with ipsilateral lung hypoplasia (hence alternative name hypogenetic lung syndrome) and occasionally dextrocardia. As noted in the history, the lungs were normal. Extralobar sequestrations have aberrant pulmonary arterial supply, not present in this case. Total anomalous pulmonary venous return presents in childhood.

Answer 14

**Pulmonary valve function**. Post-operative imaging focuses more on function to assess the success of treatment and the need for further intervention. For corrected tetralogy of Fallot, assessment of the pulmonary valve is critical as re-stenosis of the valve or progressive right ventricular impairment are linked to increased morbidity.

Answer 15

**Situs inversus**. The primitive truncus normally undergoes 150° anticlockwise rotation. In situs inversus, this rotation occurs clockwise, distinguishing it from the 30° rotation seen in transposition of the great arteries (TGA).

Answer 16

**Pulmonary valve hypoplasia with a VSD and overriding aorta**. These are features of tetralogy of Fallot (TOF), the most common cause of congenital cyanotic heart disease. The radiograph helps exclude other conditions such as truncus arteriosus, which presents with increased pulmonary flow, or coarctation, which does not cause cyanosis.

Answer 17

**Total anomalous pulmonary venous return (TAPVC)**. TAPVC, an admixture lesion, results in pulmonary plethora and cyanosis. VSD and PDA are left-to-right shunts and acyanotic. Tetralogy of Fallot shows pulmonary oligaemia, not plethora.

Answer 18

**Aberrant left pulmonary artery.** This condition, presenting with stridor and feeding problems, causes anterior oesophageal and posterior tracheal compression, unlike a double aortic arch which compresses the oesophagus posteriorly and trachea anteriorly.

Answer 19

**Figure-of-three sign**: Coarctation of the aorta. **boot-shaped**: Tetralogy of Fallot **box shaped**: Ebstein anomaly. **Snowman sign**: Supra-cardiac TAPVD.

Answer 20

**Presence of three lobes on the left**. This neonate has heterotaxy with right atrial isomerism, leading to bilateral trilobed lungs and associated with bilateral SVCs and eparterial bronchus.

Answer 21

**Type B**. Tracheoesophageal fistulae are classed depending on the communications present between the trachea and the oesophagus. In types A–D the mid-portion of the oesophagus is absent. Type A are not truly fistulae but consist of an absence of the mid-portion of the oesophagus. In type B the proximal oesophageal bud communicates with the trachea and in type C it is the distal bud that has a tracheal fistula. Type C is the most common subtype. Both proximal and distal buds have fistulous connections with the trachea in type D. Type E (or H type) tracheoesophageal fistulae have complete trachea and oesophagus with a fistulous connection between them resembling the letter H.

Answer 22

**Oesophageal atresia and proximal atretic portion and location of fistulas** 82% are of this type.

Answer 23

**Oesophageal atresia and distal trachea-oesophageal fistula** Oesophageal atresia is suspected when a new-born baby presents with drooling, and is confirmed on a chest radiograph by the presence of a gas-distended, proximal oesophageal pouch, or a coiled feeding tube within the pouch. Absence of gas in the abdomen on an abdominal radiograph implies oesophageal atresia either alone or with a proximal fistula. However, gas within the abdomen implies the presence of a distal tracheo-oesophageal fistula. Occasionally, there may be both proximal and distal tracheo-oesophageal fistulae, but this situation is rare, accounting for only 1% of patients, as opposed to around 80% with distal fistula alone. Oesophageal atresia and tracheo-oesophageal fistula may be part of the VACTERL association, which includes vertebral, anorectal, cardiovascular, tracheo-oesophageal fistula, renal and limb anomalies.

Answer 24

**Abdominal radiograph (and chest radiograph if abdominal radiograph negative)** Generally, in the case of ingested foreign bodies, a chest radiograph (including neck) at initial presentation is indicated. An abdominal radiograph is usually considered after 6 days only if there is doubt whether the foreign body has passed. However, if a sharp or potentially poisonous foreign body has been ingested, an abdominal radiograph is indicated at the time of presentation; a chest radiograph is indicated if the abdominal film is negative. Ingestion of disc batteries (small, coin-shaped batteries found in hearing aids, watches and calculators) may be associated with serious sequelae, particularly if the battery becomes lodged in the oesophagus, as is more likely with younger children and larger batteries. In this situation, leakage of alkaline material, and sodium hydroxide generated by electrolysis at the anode, can cause ulceration and perforation within a relatively short time. Radiography is indicated to locate the battery. If it lies within the oesophagus, emergency endoscopic removal is indicated. Batteries located beyond the oesophagus rarely require endoscopic removal unless subsequent radiographs indicate delay in transit of the battery.

Answer 25

**Duodenal-jejunal corkscrew appearance on an upper GI contrast study.** In individuals with malrotation, the mesenteric attachment of the midgut, particularly the portion from the duodenal-jejunal junction to the caecum, is abnormally short. The gut is therefore prone to twist counterclockwise around the superior mesenteric artery and vein—midgut volvulus. Options A to C are all imaging findings in malrotation, but not specifically that midgut volvulus has occurred. Regarding option E, duodenal obstruction can, of course, be seen with midgut volvulus, but obstruction may also occur due to obstructive bands and there is also an increased risk of congenital duodenal anomalies in malrotation, such as duodenal atresia, stenosis, and webs. It is the finding of an abnormally located duodenal-jejunal flexure and a corkscrew appearance to the duodenum and proximal jejunum that is the most specific for malrotation complicated by midgut volvulus.

Answer 26

**Malrotation with volvulus** Bilious vomiting in newborn infants is most likely to represent malrotation with midgut volvulus. The duodenojejunal flexure is on the right and CT or ultrasound demonstrates a ‘whirl sign’ of superior mesenteric vein and mesenteric vessels around the superior mesenteric artery.

Answer 27

**Duodenal web**. A duodenal web is classically associated with the ‘windsock sign’ seen on an upper GI contrast study. Over time, the web or diaphragm passively elongates because of continual peristalsis, to form the windsock conﬁguration of an intraluminal duodenal diverticulum. Duodenal atresia is commonly associated with the ‘double bubble’ appearance on AXR. The atresia is most commonly just distal to the ampulla of Vater. Associated anomalies are common, such as congenital heart disease, Down’s syndrome, and malrotation. Midgut volvulus is usually a complication of malrotation. The AXR may be normal, gasless, or show signs of duodenal/high small bowel obstruction. The upper GI contrast study shows an abnormal position of the duodenal-jejunal ﬂexure (to the right of midline) or duodenal obstruction in severe cases. More often the volvulus is intermittent, when the ‘corkscrew’ appearance is classical, due to clockwise twisting of the jejunum around the superior mesenteric artery. Annular pancreas and preduodenal portal vein are exceedingly rare. In preduodenal portal vein (persistent left vitelline vein), the portal vein lies in an abnormal position anterior to the duodenum and may cause compression. However, in this entity, the primary obstruction is more usually due to an associated obstructing duodenal lesion, such as an intraluminal membrane or web, and not to the abnormal position of the vein.

Answer 28

**Duodenal atresia** The ‘double bubble’ sign can be seen in duodenal atresia, midgut volvulus, or annular pancreas, but the absence of gas in the rest of the abdomen suggests underlying duodenal atresia. Duodenal atresia is also associated with Down’s syndrome and maternal hydramnios. Annular pancreas usually presents at a later age (if symptomatic). Midgut volvulus is seen in young infants. Some gas is seen distal to the duodenum. Choledochal cyst is seen in children and young adults with biliary symptoms.

Answer 29

**Meconium ileus** Meconium ileus is **almost diagnostic of cystic fibrosis** and presents in neonates. Family history of CF may be present. The abnormally thick meconium obstructs the ileum and a water-soluble enema may relieve the impaction. This disorder **leads to microcolon because the obstructing meconium leaves the colon unused**. **Meconium plug syndrome** is also known as **functional immaturity** of the colon. It is a temporary functional obstruction which often **occurs at the splenic flexure** and is a common cause of neonatal obstruction.

Answer 30

**Meconium peritonitis** This is a sterile chemical peritonitis, secondary to perforation of bowel resulting in prenatal leak of meconium into the peritoneal cavity. This is usually secondary to bowel obstruction and perforation in utero. Meconium peritonitis usually results in intraperitoneal calcifications, which may be focal, cystic, or generalised. On plain films, the primary finding is calcifications. On ultrasound, there may be cysts with echogenic walls (calcifications) containing meconium. Calcifications usually disappear over months or years.

Answer 31

**Hypertrophic pyloric stenosis** Ultrasound is diagnostic of this condition, including an elongated pyloric canal (> 15 mm) and thick pyloric muscle (> 3 mm).

Answer 32

**Duplication cyst** The most common location for duplication cysts is in the terminal ileum. This is followed by oesophagus, duodenum, and stomach. Duplication cysts contain both mucosal and muscle layers. On ultrasound, the mucosa is represented by an inner echogenic line and the muscle as an outer hypoechoic layer. The cyst is usually anechoic unless complicated by haemorrhage or infection. Lymphangiomas, mesenteric, and omental cysts are rare. On ultrasound, they are usually anechoic unless complicated by debris, haemorrhage, or infection. The wall is usually thin and does not have the double layer associated with duplication cysts. Ovarian cysts arise from the pelvis and will not have the layered wall appearance of a duplication cyst.

Answer 33

**Layered echogenic debris within cyst** Often an incidental finding on antenatal/postnatal US, most present in childhood. May become symptomatic due to compression effect on adjacent structures. Complications include ulceration, bleeding, volvulus, and small bowel obstruction.

Answer 34

**Duplication cyst** Gastrointestinal duplication cysts account for 15% of paediatric abdominal masses. They most commonly arise from the small bowel and colon, and although usually asymptomatic, those that contain ectopic gastric or pancreatic tissue may present with ulceration or haemorrhage. Contrast studies are not useful for diagnosis, as most cysts **do not communicate with the bowel lumen.** Ultrasound scan is the most appropriate technique and demonstrates a simple anechoic cyst with a characteristic **two-layered wall**, representing the **inner echogenic mucosa** and the **outer hypoechoic muscle.** These appearances are characteristic of bowel wall and help to distinguish a duplication cyst from other cystic lesions such as ovarian cyst, which are typically thin walled. Pancreatic pseudocyst is unlikely in the absence of previous episodes of pancreatitis.

Answer 35

**Duodenal web**. A duodenal web is classically associated with the ‘windsock sign’ seen on an upper GI contrast study. Over time, the web or diaphragm passively elongates because of continual peristalsis, to form the windsock conﬁguration of an intraluminal duodenal diverticulum. Duodenal atresia is commonly associated with the ‘double bubble’ appearance on AXR. The atresia is most commonly just distal to the ampulla of Vater. Associated anomalies are common, such as congenital heart disease, Down’s syndrome, and malrotation. Midgut volvulus is usually a complication of malrotation. The AXR may be normal, gasless, or show signs of duodenal/high small bowel obstruction. The upper GI contrast study shows an abnormal position of the duodenal-jejunal flexure (to the right of midline) or duodenal obstruction in severe cases. More often the volvulus is intermittent, when the ‘corkscrew’ appearance is classical, due to clockwise twisting of the jejunum around the superior mesenteric artery. Annular pancreas and preduodenal portal vein are exceedingly rare. In preduodenal portal vein (persistent left vitelline vein), the portal vein lies in an abnormal position anterior to the duodenum and may cause compression. However, in this entity, the primary obstruction is more usually due to an associated obstructing duodenal lesion, such as an intraluminal membrane or web, and not to the abnormal position of the vein.

Answer 36

**Patent urachus** Embryologically, the cloaca is divided by the uro-rectal septum into a dorsal part that develops into the rectum and a ventral part that gives rise to the allantois, bladder and urogenital sinus. The wolfian and Mullerian ducts drain into the ventral cloaca. The allantois becomes the urachus, which is the umbilical attachment of the bladder. Ordinarily, this atrophies to become the umbilical ligament. If it remains patent throughout its entire length, urine can drain via the umbilicus. A urachal sinus and a vesico-urachal diverticulum describe patent portions of the urachus at the umbilical and bladder ends respectively.

Answer 37

**The umbilical cord inserting at the apex of the hernia.** Omphalocele is the total failure of the midgut to return to the peritoneal cavity during the tenth week of gestation. The contents may vary from a single loop of small bowel to the entire GI tract, including the liver. An omphalocele can be differentiated from a gastroschisis (rupture of the abdominal wall) because in an omphalocele, the herniated structures are covered by peritoneum and amnion, and the umbilical cord inserts at its apex. In gastroschisis, there is a normally positioned umbilicus and the hernia is through a para-umbilical defect. Because this (probably ischaemic) rupture of the abdominal wall occurs after the bowel has returned to the peritoneal cavity, the protruding viscera are not covered in peritoneum. The contents of the hernia in gastroschisis include stomach, midgut, and occasionally portions of the urinary tract. In omphalocele, there may be associated congenital cardiac anomalies and there is also an association with Beckwith Wiedeman syndrome. There is a low incidence of additional anomalies in gastroschisis.

Answer 38

**Right-sided hernia is frequently fatal** Whilst congenital diaphragmatic hernias are commoner on the left, right-sided ones are frequently fatal. Anterior (Morgagni) hernia is usually smaller and presents in childhood, whilst posterior (Bochdalek) hernia is larger and presents early. Small bowel is the commonest viscera to herniate. Intrauterine diagnosis before 25 weeks is an indicator of poor outcome.

Answer 39

**Prune belly syndrome** Prune belly syndrome is a non-hereditary disorder occurring in males with a triad of abdominal wall muscular hypoplasia, bilateral cryptorchidism and distended non-obstructed ureters. Other associations include malrotation of the gastro-intestinal tract, intestinal atresia, cystic renal dysplasia, vesico–ureteric reflux, pulmonary hypoplasia and cardiac anomalies (including PDA, tetralogy of Fallot and VSD).

Answer 40

**Defect situated to the right of the midline** Gastroschisis tends to be a small defect (often less than 2.5 cm in length) which occurs to the right of the midline. The herniated bowel does not have a peritoneal lining and floats freely within the amniotic fluid. Features suggesting exomphalos include the presence of other congenital anomalies, midline defect, foetal ascites, herniation of the liver, amnio-peritoneal membrane covering the bowel and the defect covering a large extent of the anterior abdominal wall.

Answer 41

**Are associated with pulmonary hypoplasia** Most congenital diaphragmatic hernias are diagnosed by antenatal ultrasound and are left-sided. Bochdalek hernias are posterior and common. Morgagni hernias are anterior and rare.

Answer 42

**Prune-belly syndrome** This is a triad of incomplete abdominal wall musculature, bladder dysfunction due to urinary tract anomalies and cryptorchidism. Features of prune-belly syndrome may include bladder distension and dilated ureters due to posterior urethral valves, undescended testes, and widely separated rectus abdominal muscles.

Answer 43

**Infantile polycystic kidney disease** The infantile form of this condition can present in early infancy with poor growth, abdominal masses and renal failure, due to the presence of cystic kidneys which cause compression of renal parenchyma, causing obstructive symptoms. In some cases, there can also be associated pulmonary hypoplasia.

Answer 44

**Intussusception** This is the most common cause of bowel obstruction in infants, usually affecting those aged between 6 months and 2 years. Bilious vomiting, abdominal pain and a palpable abdominal mass are classic features, which would lead to surgical intervention. Appendicitis is rare in this age group and would not typically present with a palpable mass in the right iliac fossa. Congenital intestinal malrotation typically presents earlier in life, whereas meconium ileus usually presents in newborns with cystic fibrosis.

Answer 45

**Congenital diaphragmatic hernia** This is a common surgical cause of respiratory distress. Herniation of abdominal contents occurs through a posterolateral diaphragmatic defect or persistent pleuroperitoneal canal. The abdomen is gasless secondary to migration of bowel into chest. Intestinal malrotation and pulmonary hypoplasia is seen in almost all cases. In neonates with congenital cystic adenomatoid malformation, the chest radiograph may show a soft tissue mass in the chest, which becomes filled with air as fluid is reabsorbed over a few hours.

Answer 46

**Non-hereditary multisystem disorder** Prune belly syndrome is a congenital non-hereditary multisystem disorder, almost exclusive to men (M = 19:1). A triad of abdominal wall deficiency, non-obstructed dilated redundant ureters and bilateral undescended testes is seen.

Answer 47

**Water-soluble contrast enema.** This is rarely, if ever, indicated in the acute phase of necrotizing enterocolitis (NEC). It may be used for the evaluation of the presence of strictures, usually approximately 6–12 months after the acute phase of NEC. **Supine AXR** is the primary method used to evaluate NEC. A **‘jumbled’ pattern** may be seen secondary to **bowel wall oedema,** which either compresses the lumen in some areas or causes an ileus appearance in other areas. Pneumatosis may be seen, which is either ‘bubbly’ or linear. This can lead to air in the portal venous system, which does not appear to alter the morbidity or mortality. **Perforation**: **Supine AXR**: Rigler’s sign (air on both sides of the bowel wall) or the ‘football sign’ (air outlining the falciform ligament). **Left lateral decubitus** and **supine cross-table AXRs**: detect small quantities of free air. Abdominal ultrasound may be helpful in the acute setting of NEC, as it can depict intraabdominal fluid, bowel wall thickening, assess bowel wall perfusion, and may also detect small quantities of free air and portal venous gas.

Answer 48

**Meconium peritonitis** These features are typical of meconium peritonitis. This is a chemical peritonitis secondary to bowel perforation in utero. The intraperitoneal meconium characteristically calcifies within 24 hours of perforation. Other features seen on ultrasound include fetal ascites, poly-hydramnios and bowel dilatation.

Answer 49

**Meconium peritonitis** Meconium peritonitis is a chemical peritonitis that occurs in utero following perforation of bowel as a result of bowel obstruction or ischaemia. Most commonly, the perforation seals off in utero, but the extruded meconium may be palpable as an abdominal mass, or may become calciﬁed and therefore visible on plain ﬁlm as a dense calciﬁed mass or as calciﬁc plaques throughout the peritoneal cavity. It may also be identiﬁed on ultrasound scan as echogenic material between bowel loops with a ‘snowstorm’ appearance. In other cases, active perforation is still present at birth, and the baby presents with clinical peritonitis. Meconium ileus may result in abdominal calciﬁcations in the neonate, but these are intramural in location. Hirschsprung’s disease and other causes of intestinal obstruction may be associated with intraluminal calciﬁcations in the neonate. Neuroblastoma is frequently associated with calciﬁcation but is suprarenal in location and usually symptomatic. Duplication cysts are not usually associated with calciﬁcation.

Answer 50

**Necrotising enterocolitis** Ischaemic bowel disease secondary to hypoxia, perinatal stress and infections. The terminal ileum is commonly involved and the bowel loops show wall thickening and intramural air. Gas may be seen in the porto-venous system in the liver.

Answer 51

**Presence of blood flow within the intussusceptum** The following criteria are associated with a lower rate of successful enema reduction: age less than three months or greater than five years, long duration of symptoms, passage of blood per rectum, significant dehydration, obstruction of the small intestine and visualisation of the dissection sign during enema therapy.

Answer 52

**Mesenteric lymphadenitis** Mesenteric lymphadenitis is an inflammatory process affecting the mesenteric lymph nodes; it is most frequently caused by viral infection but also by Yersinia enterocolitica and other pathogens. It affects children and young adults, and clinically mimics acute appendicitis. Imaging findings are of enlarged mesenteric lymph nodes, and ileal and colonic wall thickening. The normal appendix must be visualized to differentiate it from acute appendicitis. Features of acute appendicitis on ultrasound scan are of a blind-ending, non-compressible, tubular, aperistaltic, fluid-filled structure measuring over 6 mm in diameter. Mesenteric lymph nodes may also be seen anterior to the right psoas muscle but tend to be smaller and fewer than in mesenteric lymphadenitis. Thickened bowel wall may be seen on ultrasound scan in Crohn’s disease, but this would be less likely in this age group. Symptomatic Meckel’s diverticulum usually presents in younger children with gastrointestinal bleeding. Small bowel duplication cyst usually presents under 2 years of age, and lymphadenopathy is not a feature.

Answer 53

**Viral gastroenteritis** Most intussusceptions occur in childhood, usually between 6 months and 2 years of age. The vast majority are idiopathic or related to mucosal oedema and lymphoid hyperplasia following viral gastroenteritis. In the 5% of patients with a pathological lead point, causes include those listed above. Patients classically present with cramping abdominal pain, screaming episodes, red currant jelly stools and a palpable abdominal mass. Most childhood intussusceptions are ileocolic. In contrast, a specific cause is identified in 80% of adult cases, and ileo-ileal intussceptions are more common than ileocolic.

Answer 54

**Typhlitis** Typhlitis is acute inflammation of the caecum, appendix and occasionally terminal ileum, initially described in neutropenic children with leukaemia, but also seen with lymphoma, following immunosuppressive therapy and with clinical AIDS. Patients present with abdominal pain and diarrhoea, and may have a palpable, right lower quadrant mass. Characteristic findings are of circumferential caecal wall thickening, with oedematous bowel wall and inflammatory changes. Pericolonic fluid and intramural pneumatosis may be seen. Leukaemic deposits would be expected to cause more eccentric bowel wall thickening. Appendicitis may result in apical caecal wall thickening but would be accompanied by abnormal appendix. Crohn’s disease may produce a similar picture, but, in this clinical setting, typhlitis is the most likely diagnosis. Diverticulitis would be very unlikely in this age group.

Answer 55

**Necrotizing enterocolitis** Necrotizing enterocolitis is an acute inflammatory bowel condition seen predominantly in preterm infants. It usually presents 2–3 days after birth, with abdominal distension, vomiting and blood-stained stools. Plain film signs include distended small and large bowel, and bowel wall thickening, but the hallmark of the condition is pneumatosis intestinalis, seen in 80% of cases. This may be curvilinear (subserosal) or bubbly (submucosal) and may also be associated with portal venous gas. Hirschsprung’s disease is characterized by an aganglionic segment of distal colon, resulting in abnormal peristalsis and impaired evacuation of the colon. In this age group, it presents with failure to pass meconium, but is extremely rare in preterm infants. Meconium ileus and imperforate anus also present with failure to pass meconium. Pneumatosis intestinalis may be seen in association with mechanical obstruction resulting from these three conditions, but it is rare. It is not a feature of viral gastroenteritis.

Answer 56

**Intussusception** This is a common surgical emergency in children less than 1 year of age. Ultrasound can accurately diagnose and assess bowel viability. Hypertrophic pyloric stenosis occurs at a much younger age and does not present with bleeding per rectum. Other options are also unlikely, with the given ultrasound appearances.

Answer 57

**Presence of blood flow within the intussusceptum** The following criteria are associated with a lower rate of successful enema reduction: age less than three months or greater than five years, long duration of symptoms, passage of blood per rectum, significant dehydration, obstruction of the small intestine and visualisation of the dissection sign during enema therapy.

Answer 58

**Mesenteric lymphadenitis** Mesenteric lymphadenitis is an inflammatory process affecting the mesenteric lymph nodes; it is most frequently caused by viral infection but also by Yersinia enterocolitica and other pathogens. It affects children and young adults, and clinically mimics acute appendicitis. Imaging findings are of enlarged mesenteric lymph nodes, and ileal and colonic wall thickening. The normal appendix must be visualized to differentiate it from acute appendicitis. Features of acute appendicitis on ultrasound scan are of a blind-ending, non-compressible, tubular, aperistaltic, fluid-filled structure measuring over 6 mm in diameter. Mesenteric lymph nodes may also be seen anterior to the right psoas muscle but tend to be smaller and fewer than in mesenteric lymphadenitis. Thickened bowel wall may be seen on ultrasound scan in Crohn’s disease, but this would be less likely in this age group. Symptomatic Meckel’s diverticulum usually presents in younger children with gastrointestinal bleeding. Small bowel duplication cyst usually presents under 2 years of age, and lymphadenopathy is not a feature.

Answer 59

**Viral gastroenteritis** Most intussusceptions occur in childhood, usually between 6 months and 2 years of age. The vast majority are idiopathic or related to mucosal oedema and lymphoid hyperplasia following viral gastroenteritis. In the 5% of patients with a pathological lead point, causes include those listed above. Patients classically present with cramping abdominal pain, screaming episodes, red currant jelly stools and a palpable abdominal mass. Most childhood intussusceptions are ileocolic. In contrast, a specific cause is identified in 80% of adult cases, and ileo-ileal intussceptions are more common than ileocolic.

Answer 60

**Typhlitis** Typhlitis is acute inflammation of the caecum, appendix and occasionally terminal ileum, initially described in neutropenic children with leukaemia, but also seen with lymphoma, following immunosuppressive therapy and with clinical AIDS. Patients present with abdominal pain and diarrhoea, and may have a palpable, right lower quadrant mass. Characteristic findings are of circumferential caecal wall thickening, with oedematous bowel wall and inflammatory changes. Pericolonic fluid and intramural pneumatosis may be seen. Leukaemic deposits would be expected to cause more eccentric bowel wall thickening. Appendicitis may result in apical caecal wall thickening but would be accompanied by abnormal appendix. Crohn’s disease may produce a similar picture, but, in this clinical setting, typhlitis is the most likely diagnosis. Diverticulitis would be very unlikely in this age group.

Answer 61

**Necrotizing enterocolitis** Necrotizing enterocolitis is an acute inflammatory bowel condition seen predominantly in preterm infants. It usually presents 2–3 days after birth, with abdominal distension, vomiting and blood-stained stools. Plain film signs include distended small and large bowel, and bowel wall thickening, but the hallmark of the condition is pneumatosis intestinalis, seen in 80% of cases. This may be curvilinear (subserosal) or bubbly (submucosal) and may also be associated with portal venous gas. Hirschsprung’s disease is characterized by an aganglionic segment of distal colon, resulting in abnormal peristalsis and impaired evacuation of the colon. In this age group, it presents with failure to pass meconium, but is extremely rare in preterm infants. Meconium ileus and imperforate anus also present with failure to pass meconium. Pneumatosis intestinalis may be seen in association with mechanical obstruction resulting from these three conditions, but it is rare. It is not a feature of viral gastroenteritis.

Answer 62

**Intussusception** This is a common surgical emergency in children less than 1 year of age. Ultrasound can accurately diagnose and assess bowel viability. Hypertrophic pyloric stenosis occurs at a much younger age and does not present with bleeding per rectum. Other options are also unlikely, with the given ultrasound appearances.

Answer 63

**Ultrasound** This is the most useful investigation as it can not only accurately diagnose intussusception but also assess bowel viability and reducibility.

Answer 64

**Gastric mucosa.** The most sensitive and specific evaluation for a Meckel’s diverticulum is a 99m Tc pertechnetate scan. This is positive only if gastric mucosa is present (in approximately 20% of patients). However, ectopic gastric mucosa is present in nearly all cases of Meckel’s diverticulum that bleed, as it is the ulcerated ectopic gastric mucosa that is the source of the haemorrhage. Ectopic pancreatic and colonic mucosa can occur in a Meckel’s diverticulum but are not typically associated with haemorrhage. Ectopic thyroid tissue is not usually found in a Meckel’s diverticulum. Other complications of a Meckel’s diverticulum include obstruction (either volvulus or intussusception) and diverticulitis.

Answer 65

**Recent barium investigation** Prior to adolescence, a Tc-99m pertechnetate scan has a high pick-up rate for a Meckel’s diverticulum. This declines with increasing age as the test relies on the presence of ectopic gastric mucosa, which is less likely to be present in someone asymptomatic throughout childhood. A false negative result is most commonly due to insufficient mass of ectopic gastric mucosa within the Meckel’s diverticulum but may also be seen with barium from recent investigation attenuating the gamma radiation and dilution of intraluminal activity due to rapid bowel transit.

Answer 66

**Meckel’s diverticulum** Meckel’s diverticulum is a true diverticulum arising from the small bowel, usually 80–90 cm from the ileocecal valve, representing failure of closure of the omphalomesenteric duct. Heterotopic gastric mucosa is present in 10–30% of diverticula but is seen in 98% of those that present with bleeding. A [99m Tc]-pertechnetate study demonstrates uptake in gastric mucosa within Meckel’s diverticulum, seen as a focal area of uptake, usually in the right lower quadrant with activity paralleling that of the stomach. Duodenal duplication cysts may contain heterotopic gastric mucosa, which may be a cause of a false-positive scan, but they often appear as larger areas of increased activity and would be expected to be in the upper abdomen. Tracer uptake may be seen in inflammatory, obstructive, and neoplastic conditions, including intussusception, peptic ulcer disease, and appendicitis, but activity does not parallel that of the stomach.

Answer 67

**Multifocal bowel wall thickening** Henoch–Schönlein purpura is an acute systemic vasculitis that affects the skin, gastrointestinal tract, joints, and kidneys. Children aged 3–10 years are predominantly affected and may present with a purpuric rash on the extensor surfaces of the limbs, arthralgia, and crampy abdominal pain with intestinal bleeding. Imaging demonstrates multifocal areas of bowel wall thickening due to intramural hemorrhage and edema. Gastrointestinal complications include bowel infarction and perforation, as well as intussusception.

Answer 68

**Meckel’s diverticulum** The 99m Tc pertechnetate scan demonstrates ectopic gastric mucosa which bleeds, giving rise to symptoms.

Answer 69

**Meconium plug syndrome**. **Meconium plug syndrome** is a transient disorder of the neonatal colon characterized by **delayed passage of meconium** and proximal dilatation of the bowel. The obstruction is due to a colonic **dysmotility and associated with a large meconium plug in the left colon**. The colon may appear normal or distended proximal to the plug and small caliber distally. A water-soluble contrast enema is both diagnostic and therapeutic. If there is persistence of abdominal distension and/or failure to evacuate, then rectal biopsy may be needed to exclude Hirschsprung’s disease. **Hirschsprung’s disease** is a disorder of the bowel resulting from absence of normal ganglionic cells in the Auerbach’s and Meissner’s plexuses. Aganglionosis always affects the rectum and extends proximally for a variable distance. Short segment disease occurs in most cases, with the **transition zone** (the junction between the normal-sized distal aganglionic segment and the proximal dilated bowel) occurring in the region of the **rectosigmoid**. Contrast enema is used to delineate the level of the transition zone and care must be taken not to overﬁll the recto-sigmoid and thus mask the transition zone. Irregular, uncoordinated contractions in the aganglionic segment would more commonly be seen in the distal colon in Hirschsprung’s disease than in a meconium plug syndrome. **Meconium ileus syndrome** is a distal small bowel obstruction secondary to **thick inspissated meconium in the ileum**, usually associated with **CF**. Water-soluble contrast enema may be both diagnostic and therapeutic. A **small left colon syndrome** is a **subtype** of meconium plug syndrome. Contrast enema shows an apparent **transition zone at the splenic ﬂexure**. There is a normal-sized sigmoid colon, but a small descending colon, mimicking a microcolon, which becomes normal sized again around the splenic ﬂexure. The caliber abnormality is therefore limited to the descending colon, which was not described in this case. Colonic atresia is secondary to a vascular insult in utero and is extremely uncommon. A microcolon exists distal to the atretic segment.

Answer 70

**Peutz–Jehger’s syndrome**. Peutz-Jehger’s syndrome is an autosomal dominant disease with incomplete penetrance characterized by intestinal polyposis and mucocutaneous pigmentation. It is the most frequent of the polyposis syndromes to involve the small intestine. When symptomatic, the most common presentation is abdominal pain (due to small bowel intussusception in up to 50%). There may also be GI haemorrhage. There is an increased risk of malignancy of the GI tract, pancreas, and breast, even though the polyps are hamartomas. Cronkhite–Canada syndrome is non-neoplastic, non-hereditary inflammatory polyposis associated with ectodermal abnormalities. It usually occurs in the middle-aged to elderly and the polyps are more common in the stomach and colon than in the small bowel. Intussusception is not a typical presentation. Gardner syndrome is an autosomal dominant disease characterized by a triad of colonic polyposis, osteomas, and soft-tissue tumours (including desmoid tumours). Age at presentation is 15–30 years. The location of the polyps is colon (100%), duodenum (90%), stomach (5–58%), and the remainder of the small bowel (<5%). Small bowel intussusception is therefore a very rare presentation. There is a very high risk of malignant transformation of the colonic polyps if left untreated. Treatment is prophylactic total colectomy. Familial adenomatous polyposis syndrome is an autosomal dominant disease. The polyps start to appear around puberty and have a similar distribution/location to those in Gardner syndrome. Again there is a high risk of malignant transformation of these adenomatous polyps. Cowden disease is multiple hamartoma syndrome. It causes hamartomatous neoplasms of the skin and mucosa, GI tract, bones, CNS, eyes, and genitourinary tract. There may be associated malignant tumours of the breast and thyroid.

Answer 71

**Hirschsprung’s disease** These features are typical of Hirschsprung’s disease. This is caused by absence of parasympathetic ganglion cells in the bowel wall. Meconium ileus typically shows an empty microcolon on water-soluble enema and colonic atresia shows a distal microcolon with obstruction at the point of atresia. Functional immaturity of the colon typically shows microcolon distal to the splenic flexure with an abrupt transition to mildly dilated proximal colon.

Answer 72

**Presacral mass** This may be teratoma, anterior meningocele or enteric cyst.

Answer 73

**Short segment** Short segment accounts for 70-80%. Long segment accounts for 15-25%.

Answer 74

**E. Infantile haemangioendothelioma**. Also known as infantile hepatic haemangioma, infantile haemangioendothelioma is a vascular neoplasm and the most common benign hepatic tumour of infancy. It may be a solitary mass or multifocal, and most are diagnosed before the age of 1 year. The lesion itself runs a benign course, but life-threatening clinical complications may occur. These include **high-output cardiac failure** secondary to large arterio-venous shunts and **Kasabach–Merritt syndrome** of coagulopathy secondary to intra-tumoral platelet sequestration. On ultrasound the lesions are well-demarcated and are generally **hypoechoic** or of mixed echogenicity. On CT and MRI the enhancement pattern of the lesion is similar to adult haemangioma. There is **intense early peripheral nodular enhancement, with centripetal progression on the later images.** **Hepatoblastoma** rarely occurs in the newborn but can be seen in young infants. This tumour is distinguished by a **heterogeneous** rather than intense centripetal **enhancement** pattern and **markedly elevated levels of alpha-fetoprotein (AFP)** in 90% of patients. AFP level is rarely elevated in infantile haemangioendothelioma. **Mesenchymal hamartoma** of the liver, like infantile haemangioendothelioma, may also be found in the perinatal period. This **benign** tumour differs in imaging appearance from infantile haemangioendothelioma in that it usually appears as a **multicystic, multilocular mass with enhancement of only the septa and solid portions.** Less commonly, mesenchymal hamartoma may be predominantly solid, but it differs from infantile haemangioendothelioma in that it is **hypovascular at dynamic contrast-enhanced imaging.** Whilst metastases could occur in an infant (e.g. neuroblastoma), they would tend to be hypodense to normal liver on contrast-enhanced CT. Hepatoma is exceedingly rare in an infant and the imaging characteristics described would not be typical.

Answer 75

**D. Hepatoblastoma**. Hepatoblastoma is the most common primary malignant hepatic tumour in children (approximately 80%). Most cases occur below the age of 3 years. Serum alpha-fetoprotein is elevated in 70–90%. The imaging features are as described = well-defined hyperechoic to surrounding parenchyma and hypodense in both arterial and porto-venous phases. Calcification is seen in approximately 50%. HCC is the next most common malignant liver tumour and has two peaks in childhood, at 2–4 years and 12–14 years. Serum alpha-fetoprotein is also elevated in approximately 80%. Imaging features are similar to those seen in an adult population, i.e. larger tumours are of heterogeneous echogenicity on ultrasound and on biphasic CT they show arterial enhancement with rapid washout on the portal venous phase. Undifferentiated embryonal sarcoma (UES) is the third most common liver malignancy and is most common between the ages of 6 and 10 years. Serum alpha-fetoprotein levels are normal. The imaging hallmark of this tumour is the discrepancy between its appearance on ultrasound and that on CT. Ultrasound is used to confirm the solid nature of this tumour, which typically is isoechoic or hyperechoic. On CT, UES is seen as a well-circumscribed, multiseptate, fluid-attenuating lesion. Enhancement of solid-appearing septa and a pseudocapsule may be seen. Mesenchymal hamartoma is the second most common benign hepatic lesion (to haemangioendothelioma). It is usually seen under the age of 2 years. Serum alpha-fetoprotein is not elevated. The typical ultrasound appearance is a multi-septate, cystic mass. Less commonly, the solid component of the lesion can be more predominant, with multiple smaller cysts giving the lesion a Swiss-cheese appearance. The usual CT finding is of a multilocular cystic mass with enhancing septa of varying thickness. Angiosarcoma is not usually seen in children, but is a rare, highly vascular, and highly malignant hepatic tumour of adults.

Answer 76

**B. Hepatoblastoma** Haemangioendotheliomas have normal Alpha fetoprotein (AFP). Mesenchymal hamartomas are usually more cystic.

Answer 77

**b. hepatoblastoma** Hepatoblastoma is the commonest malignant liver tumour of early childhood, typically presenting before 3 years with pain, palpable mass, jaundice, and weight loss, as well as precocious puberty due to hormone production. Tumours are typically large (average 10–12 cm) and appear to be heterogeneous with areas of calcification and necrosis. Metastases to the lung are common. Hepatocellular carcinoma is the second most common malignant liver tumour of children, but usually affects children over 5 years of age. Although it also commonly appears of heterogeneous echogenicity, calcifications are rare. Haemangiomas commonly appear hyperechoic on ultrasound scan and may contain calcifications, but are usually ,4 cm and are rarely seen in young children. Pyogenic abscess and choledochal cyst are typically hypoechoic lesions.

Answer 78

**a. infantile haemangioendothelioma** Infantile haemangioendothelioma is the commonest benign hepatic tumour occurring in the first 6 months of life, consisting of multiple sinusoidal vascular channels with surrounding connective tissue stroma. Patients typically present with an abdominal mass, or high-output cardiac failure secondary to arteriovenous shunting. Kasabach–Merritt syndrome (consumptive coagulopathy) is seen in 11% of patients. Typical CT features are of early peripheral enhancement and variable delayed central enhancement. Hepatoblastomas tend to occur in slightly older infants (peak 18–24 months) and congestive cardiac failure is not usually a feature. Mesenchymal hamartoma is a rare developmental liver tumour, which appears typically as a multiloculated cystic mass, but may appear solid and echogenic in infants due to innumerable microcysts. However, these are generally hypo-vascular at Doppler assessment.

Answer 79

**A. Hepatocellular carcinoma** Hepatocellular carcinoma is the most common primary malignant liver tumor in adolescents and adults. It is less common in children. In children, it tends to occur in children over 5 years and is often associated with underlying liver disease. The imaging appearance can vary from well-defined lesions to infiltrative masses. It typically presents with an acute abdomen, abdominal pain, and a palpable mass, and can have necrotic areas. Hepatoblastoma is the most common malignant liver tumor in children under 3 years of age. Hemangiosarcoma is rare and typically occurs in adults. Metastatic neuroblastoma or Wilms' tumor typically appear as a solid mass with the possibility of calcifications but less common than hepatocellular carcinoma.

Answer 80

**Hepatoblastoma** This is the most common primary malignant hepatic tumour in children occurring before 3 years of age. There is an association with Beckwith–Wiedemann syndrome. On CT there is a heterogeneous contrast enhancement whilst on MRI, the tumour is usually heterogeneously hyperintense on T2. Hepatocellular carcinoma, metastases and hemangioendothelioma are very rare in this age group.

Answer 81

**Neonatal hepatitis**. Physiological jaundice of the newborn usually resolves within 2 weeks and thus is unlikely to be the cause in this case. It is also unconjugated, as is jaundice secondary to hypothyroidism. Caroli’s disease (type V of the Todani choledochal cyst classification) would typically have an abnormal ultrasound, demonstrating cystic dilatation of the intrahepatic bile ducts. The key distinction in this question is between biliary atresia and neonatal hepatitis. The question stated that the ultrasound was normal, and visualization of a normal-sized gallbladder has been said to favour neonatal hepatitis. However, 20% of patients with biliary atresia may have a normal sized gallbladder, which also empties after a feed. Despite this, in the presence of a suggestive clinical picture, an absent or small gallbladder in the fasting state, a gallbladder with irregular and echogenic walls, or a large gallbladder that does not empty post feed are highly suggestive of biliary atresia. Distinction can be clarified with a HIDA scan. In early biliary atresia prior to cirrhosis, there is rapid extraction of radionuclide from the bloodstream, which persists and accumulates in the hepatic parenchyma with failure of excretion into the gut. Thus, visualization of isotope activity within the gut excludes the diagnosis of biliary atresia. In severe or late biliary atresia, hepatocyte function eventually deteriorates, resulting in sluggish tracer uptake by the hepatocytes. Patients with neonatal hepatitis often have decreased parenchymal extraction and clearance of radioisotope from the bloodstream but tracer does reach the intestines.

Answer 82

**Congenital biliary atresia** Congenital biliary atresia is the most likely diagnosis. It has a slight female preponderance and typically presents in the neonatal period. Ultrasound features include a large coarse liver with increased periportal reflectivity. Biliary dilatation is not typical. In severe neonatal hepatitis, the features on Tc-99m DISIDA scan can appear like biliary atresia with reduced extraction and excretion. However, the more common picture is one of reduced hepatic uptake.

Answer 83

**An echogenic triangular cord sign represents a fibrotic remnant of the common duct** E is highly suggestive but not diagnostic. The gallbladder is present in 25% of cases. The liver may be enlarged but is usually of normal echogenicity.

Answer 84

**Congenital biliary atresia** Congenital biliary atresia is a destructive inflammatory process resulting in atresia of the bile ducts, which presents in neonates with persistent jaundice. Diagnosis is usually made with a combination of liver biopsy and hepatobiliary scintigraphy with a 99m Tc-labelled iminodiacetic acid (IDA) analogue. Phenobarbital is given for 5 days prior to imaging to stimulate biliary secretion. Normal findings are of activity within the small bowel due to biliary excretion by 60 minutes, but in biliary atresia no biliary clearance is seen by 24 hours. Patients with non-obstructive causes of neonatal jaundice usually demonstrate biliary clearance into the bowel during the first 24 hours. Choledochal cyst usually presents in children, and cholescintigraphy may be used to confirm that the cystic structure is connected to the biliary system. The 99m Tc-labelled IDA analogue will fill the cyst and may show prolonged retention depending on the degree of obstruction. Cystic fibrosis may be associated with steatosis and biliary cirrhosis. Physiological jaundice resolves spontaneously within 2 weeks.

Answer 85

**Biliary atresia** Jaundice persisting beyond 1 month is usually due to biliary atresia of neonatal hepatitis. A choledochal cyst is seen in 5% of cases. These conditions have similar clinical and biochemical presentations. Ultrasound will be normal in hepatitis and biliary atresia, but no bowel activity is seen with HIDA scan on delayed images in biliary atresia.

Answer 86

**B. Hepatic fibrosis** Hepatosplenomegaly and portal hypertension are consequences. There is an increased risk of cholangiocarcinoma and renal cystic abnormalities.

Answer 87

**b. choledochal cyst** Choledochal cyst is a congenital condition characterized by aneurysmal dilatation of the common bile duct, which in most cases is associated with an anomalous junction of the common bile duct and pancreatic duct, allowing reflux of pancreatic enzymes into the common bile duct and resulting in weakening of the wall.

Answer 88

**B. Longer dorsal duct draining via minor papilla/shorter ventral duct draining via major papilla**. Pancreas divisum is the most common congenital anomaly of the pancreatic duct and has a prevalence of 4–10% of the general population. Although it is usually asymptomatic and an incidental finding, it can lead to recurrent episodes of pancreatitis in children and adults. By definition, the dorsal and ventral ducts fail to fuse during embryological development, which results in the following features seen at MRCP: (a) a prominent dorsal pancreatic duct, which drains directly into the minor papilla, and (b) a ventral duct, which does not communicate with the dorsal duct, but joins with the distal bile duct to enter the major papilla (ampulla of Vater). Typically, the ventral duct is short and narrow, while the dorsal duct normally has a larger caliber. **Normal anatomy:** Main pancreatic duct (Dorsal duct - Wirsung) should drain into the major papilla Minor pancreatic duct (Ventral duct- Santoriti) should drain into the minor papilla

Answer 89

**B. Diffuse fatty infiltration and fibrosis.** Pancreatic insufficiency is almost invariable in patients who have the delta F508 mutation for CF. The most described imaging abnormality in patients with CF is diffuse fatty infiltration and fibrosis. While pancreatic cysts are described, their size does not usually exceed a few millimetres. Larger pancreatic cysts have only been described in a few patients and complete replacement of the pancreas by macro-cysts is very unusual.

Answer 90

**C. Pancreatic duct dilatation**. In cases of acute pancreatitis in children, the echogenicity of the pancreas on ultrasound is not a helpful diagnostic feature and pancreatic enlargement is absent in 50% of the patients. The most useful diagnostic feature is dilatation of the pancreatic duct (>1.5 mm at 1–6 years of age, >1.9 mm at 7–12 years, and >2.2 mm at 13–18 years). Pancreatic ductal dilatation may also be seen in chronic pancreatitis. Pancreatic atrophy and parenchymal calcifications are more typically associated with chronic disease.

Answer 91

**Enlarged, calciﬁed adrenals that maintain their normal triangular conﬁguration** Wolman disease is a rare, autosomal recessive, primary familial xanthomatosis with involvement and calciﬁcation of the adrenal glands. Deﬁciency of acid esterase or acid lipase results in lipid deposition in multiple organs, including the liver, spleen, lymph nodes, adrenal cortex, and small bowel. It has a poor prognosis. Most patients die within 6 months of life due to malabsorption. All the above-mentioned features are noted in Wolman disease but the most speciﬁc ﬁnding is enlarged, calciﬁed adrenal glands that maintain their normal conﬁguration.

Answer 92

**123 I-metaiodobenzylguanidine (MIBG) scan** Owing to the high speciﬁcity and sensitivity in neuroblastoma, MIBG imaging has superseded the use of 99m Tc bone scans for the detection of skeletal metastases in the majority of children with neuroblastoma, which take up the tracer in >90% of cases and has been recommended by the last international consensus conference as a standard element of staging and response evaluation. False-negative scans may be observed in approximately 10% of neuroblastomas that do not concentrate MIBG. In addition, very small amounts of bone marrow tumour will often not be detected and therefore the MIBG scan must be supplemented with bilateral bone marrow biopsy. For those patients whose tumours are negative for MIBG uptake at diagnosis, the 99m Tc MDP bone scan is the standard test recommended to evaluate skeletal metastases. However, the low speciﬁcity of this test and the difﬁculty in interpreting uptake in young children with actively growing bones make investigation of alternative methods preferable. Whole-body MRI is also a sensitive test for neuroblastoma tumours, including bone and bone marrow metastases, although the speciﬁcity is much lower than for MIBG. MRI and CT are appropriate in the staging of neuroblastoma, but for the assessment of local invasion rather than bony involvement in particular. There currently is no consensus about the optimal imaging modality for assessing local disease. Both MRI and CT are routinely used, depending on local availability and the radiologist’s preference. 18-FDG PET-CT imaging is not as sensitive as MIBG imaging for bony metastases, although it may be more sensitive for small soft tissue tumours and nodal metastases. The use of PET-CT is not at present well deﬁned and delivers a high radiation dose.

Answer 93

**Stage IVs** The tumour should be staged as stage IVs. This stage refers specifically to patients less than one year of age with no crossing of the midline and disease confined to the liver, skin and bone marrow without radiographically evident skeletal metastases. It confers a good prognosis. Stage I is tumour confined to the organ of origin, stage II includes regional spread not crossing the midline, stage III is extension across the midline and stage IV includes metastatic disease.

Answer 94

**Esthesioneuroblastoma is a very malignant tumour arising from olfactory mucosa** Neuroblastomas produce catecholamines in 95% of cases. The peak age of diagnosis is < 3 and there is a better prognosis in older children. The most common site is adrenals, followed by chest, followed by neck.

Answer 95

**Stage 4S** Stage 4S applies to infants who demonstrate a tumor on one side of the body, as seen in Stages 1 and 2, but also have affected liver, skin, and/or bone marrow. Stage 4 involves distant lymph nodes and bone with or without bone marrow/ liver/other organs.

Answer 96

**Large hypoechoic mass arising the suprarenal region** Low attenuation metastatic liver lesion are echogenic on US. May have lytic/sclerotic or mixed bone metastases, increased vascularity and vascular encasement.

Answer 97

Adrenal haemorrhage is not only the commonest cause of neonatal adrenal mass but is also more likely to be seen in neonates in a high-dependency unit because it is associated with perinatal stress, hypoxia, septicaemia and hypotension. It can be unilateral or bilateral, but, even when bilateral, it does not usually cause adrenal insufﬁciency. Initially, the haematoma appears as an avascular heterogeneous mass on ultrasound scan that becomes cystic and smaller over a period of weeks. A hyperechoic rim can form, representing peripheral calciﬁcation. Haematomas can become infected, resulting in an abscess. Neuroblastoma is the main differential diagnosis; on ultrasound scan, it appears as a hyperechoic mass that can have internal ﬂecks of calciﬁcation. Repeat ultrasound scan at 1 week will not show the changes that haematoma undergoes.

Answer 98

**IV** The clinical and radiological findings are of adrenal cortical carcinoma, which is a disease with two age peaks, the first in early childhood (two-thirds of affected children being younger than 5 years) and the second in the fourth and fifth decades. Preliminary staging is performed with CT, though MR may be useful in evaluation of vascular or local invasion. T1 and T2 tumours are 5 cm and >5 cm, respectively, with no evidence of invasion. T3 tumours extend outside the adrenal into fat, and T4 tumours invade adjacent organs. Stage IV disease includes any ‘T’ or ‘N’ staging with metastases, T3 N1 and T4 disease. There is no stage V.

Answer 99

**Neuroblastoma** A childhood suprarenal mass with calcification, crossing the midline to encase the inferior vena cava and aorta is almost certainly a neuroblastoma.

Answer 100

**Medially oriented renal long axis** Ninety per cent of horseshoe kidneys are joined at the lower poles by a parenchymal or fibrous isthmus. The isthmus lies at the L4–5 level, where renal ascent is arrested by the inferior mesenteric artery. The pelves and ureters are anterior, and pelvi-ureteric junction obstruction is more common. Incidence is 1–4/1000 births, making it the commonest renal fusion abnormality. Cardiovascular, skeletal, central nervous system, anorectal and genitourinary malformations are associated. There are associations with trisomy 18 and Turner’s syndrome. Associated genitourinary anomalies include hypospadias, undescended testes, bicornuate uterus and ureteral duplication. The incidence of infection and stones increases in a horseshoe kidney.

Answer 101

**Large hyperechoic medullary pyramids** The average length of the normal neonatal kidney is 4.5 cm. Ultrasound appearances of the kidney in the neonate and infant show several differences from those of the older child and adult. Cortical echogenicity is increased, as the glomeruli form 20% of the cortex in the neonate but only 9% in the adult and may be comparable to that of the liver or the spleen. The medullary pyramids are larger and more hypoechoic than in older children and adults, and there may be little or no fat in the renal sinus. Persistent fetal lobulation may give the kidneys a lobulated contour. In addition, echogenic septa may be normally seen at the anterosuperior or posteroinferior margins of the kidney, representing the sites of fusion of metanephric elements. Most kidneys attain an adult pattern by 6 months of age.

Answer 102

**Severe renal compromise is the immediate cause of death in the perinatal group**. The incidence of autosomal recessive polycystic kidney disease (ARPKD) is approximately 1:20,000 births. It is a disease of tubular ectasia and fibrosis that results in bilateral enlarged kidneys, with loss of cortico-medullary differentiation and multiple small radially arranged cysts. ARPKD is associated with congenital hepatic fibrosis, the severity of which is inversely proportional to the renal abnormality. Four distinct groups of ARPKD are recognized based on age at presentation: perinatal, neonatal, infantile, and juvenile. The most severe renal involvement is seen in the perinatal group. In this group, severe renal impairment results in reduced urine output, oligohydramnios, and pulmonary hypoplasia. Severe respiratory compromise is the immediate cause of death in these patients. Oligohydramnios is also associated with Potter facies (low set and flattened ears, short and snubbed nose, deep eye creases, and micrognathia) and clubfoot deformity.

Answer 103

**C. Meckel Gruber syndrome**. All of the mentioned conditions are associated with multiple renal cysts, but the triad of bilateral enlarged cystic kidneys, occipital encephalocele, and polydactyly is diagnostic of Meckel Gruber syndrome. Bardet–Biedl syndrome is associated with enlarged cystic dysplasia of the kidneys with polydactyly.

Answer 104

**d. Multi-cystic dysplastic kidney** These features are highly suggestive of multi-cystic dysplastic kidney. The condition is invariably fatal if bilateral, but often asymptomatic if unilateral. It is the **second commonest** cause of a palpable abdominal mass in the neonate, **second only to hydronephrosis**. The key features are that **NO normal renal tissue** is present, the **cysts do not communicate with each other**, and they are separated by septae.

Answer 105

**c. Lung metastases** Lung metastases are rare in neuroblastoma and are seen in only 10% of cases, whereas they are seen in 85% of metastatic Wilms tumours. Wilms tumours tend to displace rather than encase the vessels, and intrinsic mass effect, rather than displacement of the kidney, is seen. Calcification is seen in 90% of neuroblastomas but only 10% of Wilms tumours. Wilms tumours are the most common abdominal neoplasm in children between one and eight years of age. It typically presents with an asymptomatic abdominal mass but pain, haematuria and fever may be found.

Answer 106

**b. Mesoblastic nephroma** Mesoblastic nephroma is the most likely diagnosis. This is the most common solid renal neoplasm in the neonate. Although definitive diagnosis with CT or ultrasound is difficult, certain features make the diagnosis more likely; it displays infiltrative growth without involvement of the vascular structures or collecting system (differentiating it from Wilms tumour) and only very rarely calcifies (differentiating it from neuroblastoma).

Answer 107

**A. ARPKD** ADPKD have normal renal echogenicity. Small cyst may not be immediately identified on ultrasound.

Answer 108

**E. Polyhydramnios in pregnancy** Cystic areas of necrosis, areas of haemorrhage and calcification are uncommon.

Answer 109

**D. Wilms’ tumour** These are all known associations of Wilm’s tumor.

Answer 110

**C. Beckwith-Wiedemann** A, B and C are all associations of Wilm’s tumour. 10-20% of patients with Beckwith-Wiedemann develop Wilm’s tumour.

Answer 111

**d. Wilms’ tumour** Wilms’ tumour is the commonest renal tumour of childhood. Seventy five per cent occur in children under 5 years, 5–10% are bilateral and 10% are multifocal. Calciﬁcation is seen in less than 15%. Nephroblastomatosis is a precursor, and the disease is associated with the WT1 and WT2 genes of chromosome 11. The WT1 abnormal gene is found in the WAGR syndrome of Wilms’ tumour, aniridia, genitourinary abnormalities and learning disability. It is also found in the DRASH syndrome of male pseudohermaphroditism and progressive glomerulonephritis. The abnormal WT2 gene is found with the Beckwith–Wiedemann syndrome and hemihypertrophy.

Answer 112

**Renal lymphangiectasia** Renal lymphangiectasia is a very rare developmental malformation probably caused by a failure of the developing kidney lymphatics to establish communication with the extrarenal lymphatic system. Abnormal lymphatic channels dilate, resulting in cystic lesions in the parapelvic, perinephric and, less commonly, retroperitoneal regions. The lesions are of water attenuation on CT and may cause contour deformities of the renal outlines.

Answer 113

**1 in 4** Infantile polycystic kidney disease is autosomal recessive. Both parents and half the children will be carriers. The sonographic hallmark is enlarged echogenic kidneys. The individual cysts are small, measuring 1–2 mm, and can be defined only with a high-resolution probe. Autosomal kidney disease affects the liver also. The less severe the renal disease, the more severe the hepatic periportal fibrosis.

Answer 114

**Multi-cystic dysplastic kidney** The sonographic appearances of this condition are typical, showing noncommunicating cysts of varying sizes separated by hyperechoic renal parenchyma (differentiating it from hydronephrosis). Autosomal dominant polycystic kidney disease is seen in adults. Autosomal recessive polycystic kidney disease shows bilateral gross renal enlargement with hyperechoic kidney involvement and usually no cysts are seen on ultrasound.

Answer 115

**The upper moiety ureter is associated with ureterocele whereas the lower moiety ureter is associated with vesicoureteric reflux.** Ectopic ureter results when the ureteral bud fails to separate from the Wolffian duct and as a consequence is carried more caudally than normal. In females, the ectopic ureter can insert distal to the external sphincter, resulting in incontinence. Approximately 70% of ectopic insertion is associated with complete ureteral duplication. According to the Weigert–Meyer rule of complete ureteral duplication, the ureteric orifice of the upper moiety inserts into the bladder medial and inferior to the lower moiety. The ureter draining the Upper moiety is associated with Ureterocele and Obstruction (note the vowels), whereas the lower pole moiety is associated with vesico-ureteric reflux. The obstructed upper moiety may not be visualized on IVU. The absence of upper pole calyx and displaced (‘drooping lily’) lower moiety calyces help in making the diagnosis.

Answer 116

**Congenital megacalyces** This is a rare developmental abnormality of the renal medulla. Imaging demonstrates dilated, multifaceted, or polygonal calyces as opposed to spherical calyces of obstructive hydronephrosis. In addition, the infundibula, renal pelvis, and ureter are normal in calibre in congenital hydronephrosis. The affected kidneys may demonstrate cortical thinning, but the renal function is preserved.

Answer 117

**Pelvic–ureteric junction obstruction** Hydronephrosis is a common cause of a palpable abdominal mass in children. The most common cause of hydronephrosis is pelvic–ureteric junction obstruction, followed by posterior urethral valves and ectopic ureterocoele. Pelvic–ureteric junction obstruction is usually due to a functional abnormality of the ureteric musculature and is found more commonly on the left than the right.

Answer 118

**Posterior urethral valve** Posterior urethral valve is a congenital disorder characterised by a thick mucosal fold located in the posterior urethra. It is the most common cause of bilateral urinary tract obstruction in boys. It is most discovered in the neonatal period, but very occasionally may present into adulthood. Diagnosis is usually made with ultrasound and surgical treatment is indicated.

Answer 119

**Are associated with vesico-ureteric reflux** Occurs in boys. Associated with oligohydramnios, an abrupt change in calibre of the posterior urethra and a trabeculated urinary bladder wall.

Answer 120

**Tc-99m DMSA scintigraphy** DMSA scan is static renal scintigraphy. There is uptake in the proximal convoluted tubules with 50% uptake within two hours and no significant excretion in this time. Excellent images of the cortex can therefore be gained, making it a good investigation for detection of renal scarring. DMSA and MAG-3 provide more functional information.

Answer 121

**Duplex kidneys may have more than 1 renal artery and vein** **MCUG shows reflux into the lower pole.** **Duplicated kidneys tend to be larger** US shows **dilatation of the upper pole calyx** and a **normal lower pole**. **A band of cortex can be seen to cross the medulla.**

Answer 122

**II** The international grading system for vesicoureteric reflux divides reflux into five classes. Grade-I describes reflux into the ureter only, with grade-II referring to reflux into the pelvicalyceal system without calyceal dilatation or blunting. Grade-III reflux is associated with mild pelvicalyceal and ureteric dilatation, though forniceal angles remain distinct. Grade-IV is associated with a tortuous ureter and moderate dilatation of the pelvicalyceal system, with blunting of the forniceal angles. Grade-V reflux describes grossly dilated tortuous ureters with marked pelvicalyceal dilatation and obliteration of the forniceal angles. **Vesicoureteric reflux grading:** Grade 1 reﬂux demonstrates reﬂux into the **ureter**. Grade 2 reﬂux into the **renal pelvis** Grade 3 **Mild pelvi-ureteric dilatation**. Grade 4 **Moderate** pelvi-ureteric dilatation and calyceal blunting, but **preserved** papillary impressions. Grade 5 **Markedly** dilated pelvis and tortuous ureter with **obliteration** of the forniceal angles and papillary impressions.

Answer 123

**Ultrasound scan within 24 hours of birth** Pyelectasis can be regarded as a renal pelvis diameter greater than 45 mm at 20 weeks’ gestation or 7 mm at 33 weeks, or above 10 mm at birth. Local protocol varies as to which fetuses to follow up and how. Some centres perform an ultrasound scan on all neonates who have had a renal pelvis diameter of above 5 mm at any point; others may only investigate if there is a renal pelvis above 10 mm persisting to birth. Ultrasound scan soon after birth, however, is the best way of detecting severe obstructive pathology, such as posterior urethral valves, that may warrant rapid surgical intervention. On this scan, if there is persisting dilatation above 10 mm, antibiotic prophylaxis and micturating cystourethrogram (MCUG) are appropriate. If reflux is seen on the MCUG, DMSA and repeat ultrasound scan at 6 weeks are appropriate. DMSA is used to assess parenchyma for scarring. If no reflux is seen MAG3 scan within 6 weeks is suggested to look for obstruction. If the renal pelvis diameter is less than 10 mm within 24 hours of birth, follow-up ultrasound scan 6 weeks later is suggested.

Answer 124

**Congenital pelvic–ureteric junction obstruction** Findings of the MAG-3 scan along with typical imaging demonstrating obstruction at the pelvi-ureteric junction.

Answer 125

**Posterior urethral valves** There are congenital folds of mucous membrane located in the posterior urethra. The findings on micturating cystourethrogram are characteristic with fusiform distension and elongation of posterior urethra, vesicoureteral reflux (usually to the left), diminution of urethral calibre and hypertrophy of bladder neck with trabeculations.

Answer 126

**Inguinal canal.** The testes form in the retroperitoneum and descend through the inguinal canal into the scrotum. Failure to descend is known as cryptorchidism. A cryptorchid testis may be located at any point along the descent route. The most common location is the inguinal canal (70% of cases) followed by the prescrotal region, just beyond the superficial inguinal ring. On ultrasound, it is usually smaller and hypo or isoechoic compared to the normally located testis. Cryptorchidism is associated with an increased risk of malignancy even after correction.

Answer 127

**Inter-cornual distance of more than 4 cm**. Incomplete fusion of the Mullerian ducts results in bicornuate uterus. MRI demonstrates divergent uterine horns with an external **fundal cleft that is more than 1 cm deep** and an **inter-cornual distance of more than 4 cm.** In **bicornuate bicollis uterus**, two separate cervical canals are seen. This is distinguished from uterus didelphys by a greater degree of fusion between the horns in the lower uterine segment. **Septate uterus** results from incomplete septal resorption following Mullerian duct fusion. It is the most common uterine anomaly (55%). At MRI, the external **fundal contour may be convex (Normal)**, flat, or minimally concave **(less than 1 cm deep)**. MRI is also useful in characterizing the type (fibrous/muscular) and extent of the septum. Differentiation between bicornuate and septate uterus is important, as septate uterus is amenable to surgical management.

Answer 128

**Juvenile granulosa cell tumour.** This is a sex cord stromal tumour arising from the granulose-thecal cells. They typically affect prepubescent girls and are unilateral. They are usually hormonally active (secrete oestrogen), resulting in precocious puberty. Granulosa cell tumours have a varied appearance on imaging. They may be completely solid with or without haemorrhagic or fibrotic changes, multilocular solid/cystic, or a completely cystic neoplasm. On T2WI they have a characteristic sponge-like appearance with innumerable cystic areas in a solid lesion of intermediate signal. Inhibin is the tumour marker used to monitor these lesions. Sertoli–Leydig cell tumour is also hormonally active, but it results in virilization and hirsutism. Malignant epithelial neoplasms of the ovaries are extremely rare in prepubertal girls. Mature cystic teratoma is the most common type of ovarian neoplasm in the paediatric age group, containing derivatives of at least two of the three germ cell layers: ectoderm, mesoderm, or endoderm. Fibroma is rare in children.

Answer 129

**Bell clapper deformity predisposes to testicular torsion**. Testicular torsion is an emergency. If it is not corrected within 6 hours, testicular salvage is less likely. Torsion results initially in venous obstruction followed by arterial obstruction. The severity of testicular ischemia depends on the duration and the degree of torsion (180–720°). Clinical differentiation between testicular torsion and epididymo-orchitis can be challenging. Two types are described: intravaginal and extravaginal. ‘Bell clapper’ deformity is the term used to describe high attachment of the tunica vaginalis to the spermatic cord that leaves the testis free to rotate. On ultrasound, the affected testis may have normal echogenicity in the early phase. In the later phase, the testis enlarges and demonstrates increased or heterogenous echogenicity. An enlarged and torted spermatic cord may be visualized. Absence of blood flow in the affected testis, with normal flow on the asymptomatic side, is most specific for torsion. Some arterial flow may persist in incomplete torsion (less than 360°). Decreased or reversed diastolic flow on pulsed wave Doppler assessment assists in the diagnosis in such cases.

Answer 130

**CF**. Bilateral seminal vesicle agenesis is frequently associated with bilateral agenesis of the vas deferens and mutations in the CF transmembrane conductance regulator gene (64–73%). It is thought to be related to luminal obstruction by thick secretions. Bilateral agenesis of the vas deferens is seen in 99% of CF in males. The affected patients usually have normal kidneys. Unilateral seminal vesicle agenesis and seminal vesicle cyst are commonly associated with ipsilateral renal agenesis. Bilateral calcified vas deferens is commonly seen in diabetics.

Answer 131

**Testicular hyperaemia does not exclude torsion** An enlarged, diffusely hypoechoic avascular testis with an associated twisted cord is diagnostic of testicular torsion. The testicular echogenicity can be normal in the very early phase of torsion. A detorted testis often demonstrates hyperaemia. Scrotal skin oedema and hydrocele can also be features of torsion.

Answer 132

**Torsion of testis** Torsion of the testicle is the commonest acute problem in the prepubertal age group. Including all ages below 20 years, epididymitis occurs in a ratio of 3:2 with torsion. This ratio is 9:1 above 20 years. Torsion of the testicular appendages accounts for around 5% of scrotal pathology overall, with the appendix testis being affected far more commonly than the appendix epididymis.

Answer 133

**Inter-cornual distance of more than 4 cm**. Incomplete fusion of the Mullerian ducts results in bicornuate uterus. MRI demonstrates divergent uterine horns with an external fundal cleft that is more than 1 cm deep and an inter-cornual distance of more than 4 cm. In bicornuate bicollis uterus, two separate cervical canals are seen. This is distinguished from uterus didelphys by a greater degree of fusion between the horns in the lower uterine segment. Septate uterus results from incomplete septal resorption following Mullerian duct fusion. It is the most common uterine anomaly (55%). At MRI, the external fundal contour may be convex, flat, or minimally concave (less than 1 cm deep). MRI is also useful in characterizing the type (fibrous/muscular) and extent of the septum. Differentiation between bicornuate and septate uterus is important, as septate uterus is amenable to surgical management.

Answer 134

**Juvenile granulosa cell tumour**. This is a sex cord stromal tumour arising from the granulose-thecal cells. They typically affect prepubescent girls and are unilateral. They are usually hormonally active (secrete oestrogen), resulting in precocious puberty. Granulosa cell tumours have a varied appearance on imaging. They may be completely solid with or without haemorrhagic or fibrotic changes, multilocular solid/cystic, or a completely cystic neoplasm. On T2WI they have a characteristic sponge-like appearance with innumerable cystic areas in a solid lesion of intermediate signal. Inhibin is the tumour marker used to monitor these lesions. Sertoli–Leydig cell tumour is also hormonally active, but it results in virilization and hirsutism. Malignant epithelial neoplasms of the ovaries are extremely rare in prepubertal girls. Mature cystic teratoma is the most common type of ovarian neoplasm in the paediatric age group, containing derivatives of at least two of the three germ cell layers: ectoderm, mesoderm, or endoderm. Fibroma is rare in children.

Answer 135

**Enlarged ovary**. Ovarian torsion can occur in all age groups, with the highest prevalence in the reproductive age group. Large heavy cysts and cystic neoplasms commonly predispose to ovarian torsion. Torsion of normal ovaries is unusual but more common in adolescents. Clinical symptoms are often nonspecific and therefore imaging is routinely requested. **On ultrasound, an enlarged ovary is the most constant finding**. The enlarged ovary may be heterogeneous due to haemorrhage and oedema. Other findings include multiple small cysts aligned in the periphery of the enlarged ovary (string of pearls sign), coexistent mass, pelvic free fluid, and twisted ovarian pedicle. Benign cystic teratoma is the most common tumour predisposed to ovarian torsion. Absent arterial flow is described as the classic colour Doppler finding. However, the **most frequent Doppler finding is decreased or absent venous flow with or without reduced arterial flow.** A **twisted ovarian pedicle** with a **‘whirlpool’** sign is a useful finding on colour Doppler.

Answer 136

**Ovarian cysts** Ovarian cysts in the newborn are more common than enteric duplication cysts, giant meconium pseudocysts, cystic lymphatic malformations or choledochal cysts. Other rarer causes of intraabdominal cystic structures in the newborn include cystic teratomas, gastric teratomas, cystic granulosa cell tumour of the ovary, ovarian teratomas and cystadenomas. Ovarian cysts may become echogenic due to the haemorrhage that can occur if they tort (twist). These cysts also have associated normal ovarian tissue, and the daughter cyst represents a follicle along the wall. Wilms’ tumours are solid and occur later in life. A giant meconium pseudocyst has a thick echogenic wall, and viscous echogenic contents. It is formed by meconium leak following fetal bowel perforation due to intestinal obstruction in meconium ileus, ileal atresia or volvulus. Twenty-five per cent show peritoneal or cyst calciﬁcation, which is pathognomonic for meconium pseudocyst. Bowel obstruction may be present also. Cystic lymphatic malformations appear as large, well-circumscribed, cystic, thin-walled structures with multiple thin septa. Internally, the fluid can be echo free or echoic because of haemorrhage, debris, chyle or infection. Mesenteric, omental or retroperitoneal cysts are seen. Choledochal cysts are subhepatic or in the porta hepatis. They are seen separate from the gallbladder and are round, tubular or teardrop shaped, and connected to the biliary tree.

Answer 137

**Amputated ovary** An amputated ovary occurs as the result of ovarian torsion and infarction. Both an ovarian teratoma and leiomyoma will enlarge the affected ovary rather than appear atrophic. A follicular cyst will usually be a simple cyst, although it may have internal echoes produced by haemorrhage.

Answer 138

**Gartner duct cyst**. Anatomical location is useful in the differential diagnosis of periurethral cysts. **A Gartner duct cyst** is a retention cyst arising from Wolfian (mesonephric duct remnant). It is typically located in the **antero-lateral aspect of the vagina above the level of the pubic symphysis.** It is usually solitary and less than 2 cm in size. At MRI, the lesion may appear hypo- or hyperintense on T1WI depending on whether the contents are simple fluid or haemorrhagic/proteinaceous. They do not displace or deform the urethra. **A Bartholin cyst** is located in the **posterolateral aspect of the lower vagina, at or below the level of the pubic symphysis.** **Skene cysts** are located **lateral to the external urethral meatus**, below the level of pubic symphysis. It may be difficult to differentiate Bartholin and Skene cysts. **Urethral diverticula communicate with the urethra** whereas periurethral cysts do not. A urethral caruncle manifests as T2 hyperintense soft tissue surrounding the external urethral meatus.

Answer 139

**Ultrasound of adrenal glands**. **Congenital adrenal hyperplasia (CAH) is the most common cause of ambiguous genitalia.** It causes virilization in females and precocious puberty in males. Most cases are caused by **21-hydroxylase deficiency** resulting in elevated 17-hydroxy-progesterone level. **Enlarged adrenal glands**, limbs over **20 mm in length and 4 mm width**, with nodular contour and normal cortico-medullary differentiation are suggestive of CAH. Stippled echogenicity producing **‘cerebriform’ appearance** is considered specific for CAH. Normal adrenal glands do not, however, exclude the diagnosis.

Answer 140

**Hydrometocolpos**. MR shows mixed SI on T1 and T2 due to blood products and may be associated with uterine and cervical anomalies.

Answer 141

**Transverse vaginal septum**. Haematometrocolpos is described, which at this age can be due to a transverse vaginal septum or imperforate hymen. There is an association with imperforate anus, hydronephrosis, renal agenesis and dysplasia, polycystic kidneys, duplication of the vagina and uterus, sacral hypoplasia and oesophageal atresia. Cervical dysgenesis and obstructed uterine horn would produce haematometra.

Answer 142

**Hamstrings**. Avulsion fractures in the pelvis are generally uncommon injuries and are seen almost exclusively in adolescent athletes. They occur at the apophyses, which while growing are more prone to injury than the adjacent tendons. The hamstrings attach at the ischial tuberosity. Sartorius attaches at the anterior superior iliac spine, rectus femoris at the anterior inferior iliac spine, the adductors at the symphysis pubis, and iliopsoas at the lesser trochanter. Care should be taken not to mistake an old avulsion, which can produce irregularity, marked periostitis, and adjacent soft-tissue mineralization, for a more sinister lesion.

Answer 143

**C. The pudendal nerve and internal pudendal vessels pass through the lesser sciatic foramen**. There are several potential pathways of extra-pelvic spread of pelvic disease. Lateral extension into the gluteal region occurs through the sciatic foramina. It is important to identify extrapelvic spread, as combined trans-abdominal and trans-gluteal surgery may be required. Knowledge of gluteal anatomy is also essential for trans-gluteal biopsy and drainages. The greater and lesser sciatic notches are noted in the posterior border of the innominate bone separated by the ischial spine. The greater sciatic foramen (GSF) is bounded antero-superiorly by the greater sciatic notch, postero-superiorly by the sacrum, and inferiorly by the sacrospinous ligament. The piriformis muscle arises from the ventral aspect of the sacrum and passes through the GSF to insert into the greater trochanter. It divides the GSF into two compartments. The supra-piriformis foramen transmits the superior gluteal vessels and nerves. The infra-piriformis foramen transmits the inferior gluteal vessels and nerves, pudendal and sciatic nerves. The lesser sciatic foramen (LSF) is bounded anteriorly by the lesser sciatic notch, superiorly by the sacrospinous ligament, and postero-inferiorly by the sacro-tuberous ligament. The obturator internus tendon, the pudendal nerve, and the internal pudendal vessels pass through the LSF.

Answer 144

**d. Lateral epicondyle** The lateral epicondyle is the last of the above structures around the elbow to ossify. The mean age for ossification of the lateral epicondyle is ten years. The sequential order of ossification starting with the earliest is capitellum, radial head, medial epicondyle, trochlear, olecranon and finally lateral epicondyle. The relevant ages are (in years) two, five, five, nine, nine and ten years respectively.

Answer 145

**B. Achondroplasia**. This question tests knowledge of the severe skeletal dysplasias. Achondroplasia is the most common cause of dwarfism and is hereditary. The humeri and femora are more profoundly affected than the other long bones, although the entire skeleton is abnormal. Narrowing of the interpedicular distance as one progresses caudally down the spine is unique to this condition. Other features include a large skull with a small skull base, square iliac wings with a ‘champagne glass’ pelvic cavity and widened metaphyses. Thanatophoric dysplasia results in early death. Features include severe platyspondyly and ‘telephone receiver’ femora. Chondrodysplasia punctata results in stippled epiphysis and rhizomelic dwarfism. Jeune syndrome (asphyxiating thoracic dystrophy) results in respiratory distress, very short ribs, metaphyseal irregularity/beaking, and trident acetabulum. Cleidocranial dysplasia is characterized by lack of development of the pubic bones bilaterally. There is also absence or hypoplasia of the clavicles and the presence of wormian bones in the skull.

Answer 146

**Down’s syndrome** **Anterior vertebral body scalloping** is seen in Down’s syndrome. There is also squaring of the vertebral bodies, and atlanto-axial subluxation occurs in approximately 25% of cases. **Posterior scalloping:** syringomyelia Marfan’s Osteogenesis imperfecta Hurler’s and Morquio’s.

Answer 147

**e. Achondroplasia** Achondroplasia does not cause a bone-within-bone appearance. This phenomenon can, however, be seen as a normal variant within the neonatal thoracic and lumbar spine. As well as the above conditions, a bone-within-bone appearance is also seen in thalassemia, acromegaly, Paget’s disease, rickets, scurvy, hypothyroidism, hypoparathyroidism, Gaucher’s disease and post-radiation, amongst others.

Answer 148

**b. Cleidocranial dysostosis** Cleidocranial dysostosis is an autosomal dominant condition. Features include multiple **Wormian bones**, delayed ossification of midline structures, **hypoplasia or absence of the lateral portion of the clavicle** (10%), **elongated metacarpals and short distal phalanges of the hands**. Pyknodysostosis is an autosomal recessive condition which also causes clavicular dysplasia.

Answer 149

**Rickets** The most common cause of metaphyseal cupping is Rickets. Other features include rachitic rosary seen on chest radiograph, widening, and fraying of the metaphyses, coarse trabeculation and bowing of the long bones. The most common sites to be affected are the metaphyses of the long bones which are under stress – ankles, knees, and wrists. Cupping of the distal ulnar may be a normal variant but none of the other signs will be present. Scurvy shows a radiolucent band; hypervitaminosis D and hypothyroidism cause a radio-dense band.

Answer 150

**Cleidocranial dysostosis** **Causes of wide cranial sutures:** Cleidocranial dysostosis. Osteogenesis imperfecta. Pyknodysostosis Hypoparathyroidism Raised intracranial pressure.

Answer 151

**Osteogenesis imperfecta** Other causes include ‘PORK CHOPS’: pyknodysostosis, rickets, kinky hair syndrome, cleidocranial dysostosis, hypothyroidism/hypophosphatasia, otopalatodigital syndrome, pachydermoperiostosis, syndrome of Down’s.

Answer 152

**Neuroblastoma** Other causes include hereditary spherocytosis, iron deficiency anaemia, neuroblastoma, G6PD deficiency, sickle cell anaemia and thalassemia major.

Answer 153

**Osteopetrosis** **Alternating lucent and dense metaphyseal bands:** Osteopetrosis Growth arrest lines Chemotherapy Rickets Chronic anaemias Treated leukaemia **Solitary dense metaphyseal band:** Heavy metal poisoning Congenital hypothyroidism Hypervitaminosis D Normal infants

Answer 154

**Achondroplasia** Other features include small skull bone with narrow foramen magnus, instability of cervical spine, horizontal acetabulum and small sacral notch.

Answer 155

Others have anterior beaking of inferior body. Other spinal features include vertebra pleura, hypoplastic dens dorso-lumbar gibbus and posterior scalloping.

Answer 156

**Foci of low signal on all sequences** Calcification which may be punctate or sheet-like can appear as low SI. Usually bilaterally symmetrical thighs > upper limbs anterior and lateral compartments > medial compartments. Atrophy and increased fatty infiltrates are secondary to steroids and disease.

Answer 157

**Lucent extensions into the metaphyses** Rickets is osteomalacia occurring in an immature skeleton, resulting in poorly mineralized osteoid and bone softening. The fundamental deficiency is of the active form of vitamin D (1,25dihydroxycholecalciferol), which is required for normal osteoid mineralization. Dietary vitamin D (7-dehydrocholesterol) is converted in the skin to cholecalciferol (vitamin D3 ) by sunlight. In the liver, cholecalciferol is hydroxylated to 25-hydroxycholecalciferol by the enzyme 25-hydroxylase; this is then further converted into the active form of vitamin D in the kidney. Abnormality anywhere in this pathway can lead to rickets, and its causes include dietary deficiency (most common), lack of sunlight, and renal or liver disease. Phosphate has a significant influence in the regulation of vitamin D metabolism, and hypophosphataemia is noted in many cases of vitamin D-refractory rickets. Hypophosphatasia is a rare inherited metabolic disorder of decreased tissue non-specific alkaline phosphatase causing defective bone mineralization, which is refractory to vitamin D treatment. It resembles rickets radiologically, with irregular, poorly mineralized epiphyses with a sclerotic rim and metaphyseal fraying. However, **in hypophosphatasia**, associated **irregular lucent extensions into the metaphyses** representing uncalcified bone matrix **are characteristic**, allowing differentiation from rickets.

Answer 158

**Trevor’s disease** Trevor’s disease (also called **dysplasia epiphysealis hemimelica**) is a rare developmental bone dysplasia. It primarily occurs in children aged 2–4 years and affects boys more commonly than girls. It shows a preponderance for the lower limbs, most commonly affecting the knee and ankle, and demonstrates single or multiple **osteocartilaginous tumours arising from epiphyses**. The lesion is characteristically hemi-melic, involving either the medial (two-thirds of cases) or lateral aspect of the ossification centres. Cases can be classified as localized, classic or generalized.

Answer 159

**Multiple Wormian bones** Causes of a generalized increase in bone density in childhood include osteopetrosis, pyknodysostosis and craniodiaphyseal dysplasia (in order of increasing rarity). Features of pyknodysostosis that allow differentiation from the other conditions are thick calvaria (spared in osteopetrosis), multiple Wormian bones, and widened lambdoid sutures and fontanelles. Other manifestations include short limbs, mandibular hypoplasia, poor pneumatization of the paranasal sinuses, non-segmentation of C1–2 and L5–S1, and clavicular dysplasia. This final feature has led to speculation that it is a variant of cleidocranial dysostosis. Insufficiency fractures may be seen in both conditions. Cortical expansion resulting in narrowing of the medulla is a feature of fluorosis.

Answer 160

**Thanatophoric dysplasia** Thanatophoric dysplasia is transmitted by a dominant gene mutation, and is the commonest lethal neonatal skeletal dysplasia after osteogenesis imperfecta type II. Infants with this condition are frequently stillborn or die shortly after birth from respiratory failure. The appearances on the chest radiograph are pathognomonic, with short ribs that characteristically do not extend beyond the anterior axillary line. The vertebral bodies are curved into an H or U shape (best seen on a lateral radiograph), and the humeri are curved and short. Other skeletal abnormalities such as polydactyly may be present. Dysplasias associated with short ribs often present early in life with respiratory distress due to a critically small chest diameter.

Answer 161

**Down’s syndrome** Down’s syndrome is a common genetic abnormality that results from trisomy of chromosome 21. The pelvic features in infantile Down’s syndrome were first described by Caffey. **The iliac index** (sum of the acetabular and iliac angles) is **decreased** in Down’s syndrome and is particularly useful in making an early diagnosis. **Flaring of the iliac wings** due to their rotation into the coronal plane is a typical finding that gives them an increased prominence on frontal radiographs, with the appearance likened to Mickey Mouse or elephant ears. Down’s syndrome is associated with a wide array of skeletal abnormalities, with the skull, spine and appendicular skeleton all potentially involved.

Answer 162

**Increased trabeculae** Osteomalacia is bone softening due to accumulation of excessive amounts of uncalciﬁed osteoid and poor bone mineralization of that osteoid, which in children is called rickets. As there is reduced mineralization, the bones may appear of diffusely reduced density on radiographs, which should be termed ‘osteopenia’ rather than ‘osteoporosis’, as the latter term refers to a reduced quantity of normally mineralized bone. There is also a decrease in the number of trabeculae, which appear fuzzy and coarse. The softening of the bone leads to insufﬁciency fractures and bowing deformities. Fractures may heal with unmineralized osteoid that gives the appearance on radiographs of persistent lucent lines called Looser’s zones. The underlying abnormality is a deﬁciency of vitamin D, which is required for normal bone mineralization. The two commonest causes of this are dietary and secondary to renal pathology (renal osteodystrophy).

Answer 163

**Osteogenesis imperfecta** Osteogenesis imperfecta is one of the more common heritable connective tissue disorders and is characterized by micromelic dwarﬁsm. In all four major types, findings include bowing of the long bones because of softening caused by osteomalacia and multiple fractures once the child is walking. Other findings include cortical thinning, exuberant callus formation and pseudarthroses. Rickets and Blount’s disease both show abnormal metaphyses, with rickets also demonstrating a coarse trabecular pattern. Neurofibromatosis causes bowing most localized to the junction of the middle and distal thirds of the tibia, with associated sclerosis and cystic changes.

Answer 164

**Rickets** This is the characteristic appearance of the growth plates of children with rickets. Features include poorly mineralised epiphyseal centres, irregular and widened epiphyseal plates, cupping and fraying of metaphysis, cortical spurs, deformities and bowing of long bones.

Answer 165

**Sickle cell disease** On a chest radiograph, there may be absence of a splenic shadow secondary to progressive splenic infarction, pulmonary opacities caused by pneumonia or infarction, gallstones from haemolysis and cardiomegaly induced by a high output state secondary to anaemia. Sludging of sickled red blood cells in bones leads to infarction or avascular necrosis. Typical areas of involvement include spine and humeral head. In the spine, the H-shaped vertebra is secondary to central infarction and relative overgrowth of the remaining end-plate and is virtually pathognomonic of this condition.

Answer 166

**Multiple Wormian bones** Causes of a generalized increase in bone density in childhood include osteopetrosis, pyknodysostosis and craniodiaphyseal dysplasia (in order of increasing rarity). Features of pyknodysostosis that allow differentiation from the other conditions are thick calvaria (spared in osteopetrosis), multiple Wormian bones, and widened lambdoid sutures and fontanelles. Other manifestations include short limbs, mandibular hypoplasia, poor pneumatization of the paranasal sinuses, non-segmentation of C1–2 and L5–S1, and clavicular dysplasia. This final feature has led to speculation that it is a variant of cleidocranial dysostosis. Insufficiency fractures may be seen in both conditions. Cortical expansion resulting in narrowing of the medulla is a feature of fluorosis.

Answer 167

**Thanatophoric dysplasia** Thanatophoric dysplasia is transmitted by a dominant gene mutation, and is the commonest lethal neonatal skeletal dysplasia after osteogenesis imperfecta type II. Infants with this condition are frequently stillborn or die shortly after birth from respiratory failure. The appearances on the chest radiograph are pathognomonic, with **short ribs that characteristically do not extend beyond the anterior axillary line**. The **vertebral bodies are curved into an H or U shape** (best seen on a lateral radiograph), and the **humeri are curved and short**. Other skeletal abnormalities such as polydactyly may be present. Dysplasias associated with short ribs often present early in life with respiratory distress due to a critically small chest diameter.

Answer 168

**Down’s syndrome** Down’s syndrome is a common genetic abnormality that results from trisomy of chromosome 21. The pelvic features in infantile Down’s syndrome were first described by Caffey. The iliac index (sum of the acetabular and iliac angles) is decreased in Down’s syndrome and is particularly useful in making an early diagnosis. Flaring of the iliac wings due to their rotation into the coronal plane is a typical finding that gives them an increased prominence on frontal radiographs, with the appearance likened to Mickey Mouse or elephant ears. Down’s syndrome is associated with a wide array of skeletal abnormalities, with the skull, spine and appendicular skeleton all potentially involved.

Answer 169

**Increased trabeculae** Osteomalacia is bone softening due to accumulation of excessive amounts of uncalcified osteoid and poor bone mineralization of that osteoid, which in children is called rickets. As there is reduced mineralization, the bones may appear of diffusely reduced density on radiographs, which should be termed ‘osteopenia’ rather than ‘osteoporosis’, as the latter term refers to a reduced quantity of normally mineralized bone. There is also a decrease in the number of trabeculae, which appear fuzzy and coarse. The softening of the bone leads to insufficiency fractures and bowing deformities. Fractures may heal with unmineralized osteoid that gives the appearance on radiographs of persistent lucent lines called Looser’s zones. The underlying abnormality is a deficiency of vitamin D, which is required for normal bone mineralization. The two commonest causes of this are dietary and secondary to renal pathology (renal osteodystrophy).

Answer 170

**Osteogenesis imperfecta** Osteogenesis imperfecta is one of the more common heritable connective tissue disorders and is characterized by micromelic dwarfism. In all four major types, findings include bowing of the long bones because of softening caused by osteomalacia and multiple fractures once the child is walking. Other findings include cortical thinning, exuberant callus formation and pseudarthroses. Rickets and Blount’s disease both show abnormal metaphyses, with rickets also demonstrating a coarse trabecular pattern. Neurofibromatosis causes bowing most localized to the junction of the middle and distal thirds of the tibia, with associated sclerosis and cystic changes.

Answer 171

**Rickets** This is the characteristic appearance of the growth plates of children with rickets. Features include poorly mineralised epiphyseal centres, irregular and widened epiphyseal plates, cupping and fraying of metaphysis, cortical spurs, deformities and bowing of long bones.

Answer 172

**Sickle cell disease** On a chest radiograph, there may be absence of a splenic shadow secondary to progressive splenic infarction, pulmonary opacities caused by pneumonia or infarction, gallstones from haemolysis and cardiomegaly induced by a high output state secondary to anaemia. Sludging of sickled red blood cells in bones leads to infarction or avascular necrosis. Typical areas of involvement include spine and humeral head. In the spine, the H-shaped vertebra is secondary to central infarction and relative overgrowth of the remaining end-plate and is virtually pathognomonic of this condition.

Answer 173

**E. Widening of the joint space**. This occurs early in Perthes’ disease. There is widening of the physis initially in SUFE (in advanced slip the physis can appear narrowed), but loss of joint space rather than widening may occur late in the disease, secondary to chondrolysis. In question 42, answers A, C, and D are also features of SUFE. The line of Klein is the line along the lateral aspect of the proximal femoral metaphysis, which should normally intersect the proximal femoral epiphysis, but does not in SUFE.

Answer 174

**B. Loss of overlap between the medial femoral metaphysis and acetabulum**. This has been termed the **‘metaphyseal extrusion’ sign** and is a subtle early finding in **SUFE**. Answers A, D, and E are signs of Perthes’ disease, although apparent reduction in size of the femoral epiphysis can occur later in SUFE as the epiphysis slips more posteriorly. Demineralization is not a good discriminating factor. It is more associated with Perthes’ disease; it can occur in SUFE, but sclerosis of the proximal metaphysis occurs later (metaphyseal blanch sign).

Answer 175

**A. Subcortical lucency and fissuring of epiphysis** B-E are seen in SUCFE but some of these features are also seen in Perthes’. However, subcortical lucency and fissuring is not seen in SUFE.

Answer 176

**A. Alpha angle > 60** Alpha angle should measure >60 in a normal hip. Acetabular angle >30 strongly suggests dysplasia. Beta angle should measure less than 77. The alpha angle is the line between the straight edge of the ilium and the bony acetabular margin. The beta angle is the angle between the straight lateral edge of the ilium and the fibrocartilaginous acetabulum. Over 58% coverage of the femoral head is considered normal, 33–58% coverage is indeterminate and less than 33% is abnormal.

Answer 177

**A. Legg–Calve–Perthes disease** These features suggest Legg–Calve–Perthes disease; this is idiopathic avascular necrosis of the femoral head in children. The peak age group is between four and eight years. The earliest visible signs on plain film include small femoral epiphysis, sclerosis of the epiphysis and widening of the joint space due to thickening of the cartilage. A frog-leg lateral view is useful and may be the only view in which some of the findings are seen.

Answer 178

**B. < 6 months** Once femoral epiphyses ossify, DDH becomes more difficult.

Answer 179

**B. Alpha angle of 48**’ In performing hip ultrasound scan, the views should be taken in the coronal plane with the leg in internal rotation. The alpha angle refers to the angle between the iliac bone and the acetabular margin, and 60 or greater represents normal acetabular development. The femoral head should sit so that half of it lies within the acetabulum (equator sign). In poorly developed sockets seen in developmental dysplasia, the shallow acetabulum shows a reduced alpha angle of less than 49’, which is suggestive of potential instability regardless of concentric or eccentric location of the head. The beta angle allows for sub-categorization of the hip sonographically, less than 55’ being normal and over 70’ suggestive of instability. An inverted labrum is seen in severe cases only.

Answer 180

**C. slipped upper femoral epiphysis** Slipped upper femoral epiphysis is the most common hip abnormality in adolescents and is a frequent cause of premature osteoarthritis, pain, and disability. The most affected demographic are **overweight teenage boys**. Radiographs are still the initial investigation of choice, and recognition of early subtle signs allows earlier diagnosis and prompt treatment, improving long-term prognosis. The femoral head often slips posteriorly prior to slipping medially, and early slippage is best seen on lateral or frog lateral views. Early signs on the AP projection include **widening of the physis with local demineralization**. Posterior slippage of the femoral head may then give the **appearance of a small epiphysis due to rotation** and narrowing of the physis, and lateral views may show the displacement. The line of Klein is a line drawn along the lateral femoral neck, which should intersect with a small portion of the lateral femoral head. If it does not, it suggests medial slippage. An **ill-defined area of increased opacification (metaphyseal blanch sign)** may be seen in the proximal metaphysis, which is thought to represent a healing response.

Answer 181

**(c) Slipped upper femoral epiphysis** The appearance on the radiograph of an apparent widening of the proximal femoral epiphysis and metaphyseal irregularity is consistent with SUFE. The line drawn along the lateral edge of the femoral neck not intersecting the proximal femoral epiphysis (line of Klein) confirms the diagnosis. Perthes disease typically shows changes in the femoral head and is associated with a smaller epiphysis. Septic arthritis would likely show joint effusion or osseous changes not seen here.

Answer 182

**(b) Legg–Calve–Perthes disease** This is most common in Caucasian boys. Initial radiographic findings show joint widening with medial and lateral displacement of the femoral head, suggesting oedema. With disease progression there is sclerosis, subchondral lucency, lateral epiphyseal extrusion and calcification lateral to the femoral head.

Answer 183

**Fibrous dysplasia**. The clue here is the café-au-lait spots. **McCune–Albright syndrome:** Unilateral polyostotic fibrous dysplasia Precocious puberty Café-au-lait spots. Osteomyelitis is unlikely because of the normal inflammatory markers, lack of systemic symptoms, and lack of periosteal reaction. Aneurysmal bone cyst and GCTs are possibilities (the former may even complicate fibrous dysplasia). Chondroblastoma is an epiphyseal lesion.

Answer 184

**None of the above**. The correct answer is to do nothing. This is the classical description of a **non-ossifying fibroma (NOF).** These and fibrous cortical defects are common in children and adolescents, and are usually a painless, incidental finding. They are **eccentric, well-defined, cortically based lesions with marginal sclerosis.** They can be expansile. They are most common in the **femur and tibia** **Fibrous cortical defects measure less than 2 cm whereas NOFs are larger.** They routinely heal by sclerosis and disappear. An IBS can show uptake during healing and a CT scan can show apparent cortical breakthrough. Thus, the correct management is to do nothing. If there are atypical features, such as pain or periostitis, then additional investigation is indicated.*

Answer 185

**Langerhans cell histiocytosis (LCH)**. The radiographic description is typical for skull involvement in LCH. The bevelled edge results from uneven destruction of the inner and outer skull tables. They are more likely to present with pain than any other lesion. Marginal sclerosis may be seen with healing lesions. Epidermoids are oval-shaped lytic lesions but tend to have sclerotic margins. Neuroblastoma metastases are also lytic lesions, but with a sunburst periosteal reaction. Sutural diastasis may be seen due to dural involvement. Haemangiomas exhibit a coarse trabecular pattern radiating from an oval defect. Osteomas appear as a dense homogenous focus.

Answer 186

**Diaphyseal aclasia**. The description is classic for multiple hereditary osteochondromas/exostoses, also known as diaphyseal aclasia. Osteochondromas are the result of displaced growth plate cartilage, which causes lateral bone growth from the metaphysis. They typically point away from the epiphysis. There is continuity of the normal marrow, cortex, and periosteum between the exostosis and the host bone. The cartilage cap, which is the source of growth, may have some chondroid matrix, but the appearance is otherwise of a deformed but normal bone. They are normally found in the extremities, with 36% around the knee. Their growth normally ceases at skeletal maturity. Symptoms are related to pressure effects on adjacent neural or vascular structures. Less than 1% of solitary osteochondromas undergo malignant transformation to chondrosarcoma. Findings that should alert to this are destruction of exostosis bone, destruction of matrix in the cartilage cap, irregular or thick (>2 cm in adults, >3 cm in children) cap, or growth of the cap after skeletal maturity. Multiple hereditary osteochondromatosis is an uncommon autosomal dominant condition. Patients present with multiple osteochondromas, which cause short stature. The elbow and wrist joints are often deformed. There is a higher risk of malignant transformation than in solitary osteochondromas, probably 2–5%. Ollier disease is the presence of multiple enchondromas and Mafucci syndrome requires, in addition, multiple soft-tissue haemangiomas. Morquio and Hunter syndromes are mucopolysaccharidoses, with their own musculoskeletal abnormalities, which often make an appearance in exams.

Answer 187

**Centrilobular nodules** The patient had an eosinophilic granuloma and presented with recurrent pneumothoraces due to Langerhans’ cell histiocytosis, which is characterised by centrilobular nodules which cavitate, initially forming thick-walled and then thin-walled cysts. The fibrosis that follows typically involves the upper zones. Cystic lesions along the bronchial tree are a feature of cystic bronchiectasis.

Answer 188

**Enchondroma** The most common location of these benign lesions is the tubular bones of the wrist and hands, and they are usually asymptomatic and therefore diagnosed incidentally. Of the other lesions mentioned, ABC, simple bone cyst and fibrous dysplasia are rare in the hands. An epidermoid inclusion cyst is most likely to occur at the distal phalanx.

Answer 189

**Langerhans’ cell histiocytosis (LCH)** The most common location for LCH is the skull, particularly the diploic space of the parietal bone. Lesions are typically round or ovoid and have a bevelled edge without marginal sclerosis, giving a punched-out appearance. (This is due to greater involvement of the inner table of the skull than the outer.) There may be an associated soft-tissue mass overlying the lytic process which is often palpable. LCH commonly occurs in children, and they present with painful, tender bone lesions. Most bone involvement is monostotic (50–75%) and when occurring in long bones (humerus, femur, tibia), the diaphysis is the primary site. The differential for multiple lytic lesions in a child includes (‘FLEM MC’): Fibrous dysplasia; Langerhans’ cell histiocytosis/Leukaemia; Enchondromatosis; Metastatic Neuroblastoma; Multifocal osteomyelitis; and Cystic angiomatosis (the last two are rare).

Answer 190

**Absence of haemangiomas** Both are associated with juvenile granulosa cell ovarian tumours and other malignancies. The presence of multiple enchondromas with haemangiomas indicates Maffucci syndrome.

Answer 191

**Eosinophilic granuloma** Eosinophilic granuloma is a benign variety of Langerhans’ cell histiocytosis. Fifty per cent of cases involve the skull and 25% affect the axial skeleton. It is the **commonest cause of vertebra plana** (collapsed dense vertebra) in children. The posterior elements are rarely involved. Ewing’s sarcoma may cause destruction of a vertebra, but vertebra plana is not a feature. The other conditions are all causes of vertebra plana but are less common in this age group.

Answer 192

**Dermoid** They are usually an incidental finding. They have a characteristic appearance of a central lucent area with sclerotic margins.

Answer 193

**Non-ossifying fibroma or a fibrous cortical defect** These benign lesions typically present like this. On MRI, they appear as low signal on T1 and T2 images due to hypocellular fibrous tissue within. Chondromyxoid fibromas show a bulging cortex and geographical bone destruction with calcifications and septations. On MRI they are hyperintense on T2. Intraosseous ganglion is hyperintense on T2. Aneurysmal bone cysts show fluid–fluid levels and are heterogenously hyperintense on MRI.

Answer 194

**Langerhans cell histiocytosis** This predominantly affects children and is characterised by clonal proliferation of abnormal Langerhans cells; histiocytes capable of migrating from skin to lymph nodes. This is the most likely diagnosis in a child presenting with vertebra plana with sparing of the disc spaces.

Answer 195

**Chondroblastoma** This is the **most common neoplasm seen in the apophysis/epiphysis of skeletally immature patients.** These are typical imaging features, showing a lytic lesion with sclerotic margins and calcifications in the matrix. There is surrounding marrow and soft tissue oedema. MRI overestimates the extent. The tumour is almost always benign but may become locally aggressive.

Answer 196

**Arrange MRI, CT chest, and IBS**. The lesion described is probably an osteosarcoma. Ewing’s sarcoma is high on the differential diagnosis but is less often found in the metaphysis and usually has a soft-tissue component. Osteosarcomas commonly arise from the metaphysis (only 2–11% arise from the diaphysis). They are most common in the distal femur followed by the proximal tibia. If osteoid matrix is present on plain ﬁlm, osteosarcoma is the diagnosis until proven otherwise. The appropriate action would be to refer to a regional orthopaedic centre for discussion at a multidisciplinary meeting with imaging followed by biopsy or surgery as thought appropriate. An MRI is used to evaluate local extent, the CT chest and IBS to search for pulmonary and bony metastases, respectively. Surgery is often performed after repeat imaging following the administration of neoadjuvant chemotherapy, when the oedema surrounding the tumour is less pronounced. The findings are not particularly suspicious for NAI (option A). It is not safe to assume the appearances are caused by osteomyelitis and in any case more urgent investigation would be required to confirm such a diagnosis. A CT of the area might be useful but involves ionizing radiation, which MRI avoids; the MIBG scan would be appropriate for neuroblastoma, which is unlikely in this age group (90% occur before the age of 5) (option C). A metastasis is very unlikely in this age group.

Answer 197

**Ewing’s sarcoma** Ninety-five per cent present between 4 and 25 years of age. Sixty per cent occur in the long bones, mainly in the meta-diaphysis and have a typical moth-eaten destructive appearance on plain film. Metastases to the lung, bone and regional lymph nodes are present in 11–30% of cases at the time of diagnosis.

Answer 198

**High SI on Short TI Inversion Recovery (STIR)** Other features include local oedema, extension, and destruction. Usually isointense to muscle on T1, similar or **hyperintense to muscle on T2** and with **poorly defined margins and heterogeneous contrast enhancement.**

Answer 199

**Ewing’s sarcoma** Ewing’s sarcoma is the commonest malignant bone tumour in children, and the ribs are involved in 30% of cases in children under 10. It is the commonest malignant chest wall tumour. Neuroblastoma presents in children under 5 as a well-deﬁned, soft-tissue mass that may calcify and erodes/splays the ribs. Hodgkin’s disease presents in young adults, and usually involves bones by secondary involvement with direct invasion of sternum or ribs. Osteomyelitis presents at any age with a shorter history (usually less than 2 weeks), and imaging shows rib destruction with a relatively small mass and loss of tissue planes. Hamartoma of the chest wall presents in the ﬁrst year of life as an extra-pleural mass, causing partial/complete destruction of adjacent ribs. Signiﬁcant calciﬁcation and compression of the adjacent lung occur.

Answer 200

**Ewing’s sarcoma** More than 50% of cases are seen in long bones. They are common in the meta-diaphyseal region and most common in the 5- to 10-year age group. often presenting similarly to osteomyelitis. MRI is extremely useful in determining the extent of the tumour, which is low on T1, high on T2 and STIR and enhances with contrast.

Answer 201

**An atlanto-dens interval (ADI) of 6 mm**. There are appearances that are normal for a paediatric cervical spine, which would be considered pathological in an adult and of which it is important to be aware. Pseudo-subluxation at C2/3 and C3/4 is common (it was observed in 46% of patients less than 8 years old at C2/3 in one study and has been seen up to 14 years). The anterior aspects of the spinous processes of C1, C2, and C3 should line up within 1 mm of each other on flexion and extension (assessed by drawing the posterior cervical line, a line from the anterior aspect of the spinous process of C1 to the equivalent point at C3). The anterior aspect of the spinous process of C2 is allowed to pass through, touch, or lie up to 1 mm behind the posterior cervical line in physiological subluxation. The normal ADI (the distance between the anterior aspect of the dens and the posterior aspect of the ring of the atlas) in adults is 3 mm but is normal up to 5 mm in children. ‘Pseudo-Jefferson’ fractures (pseudospread of the lateral masses of C1 on C2) can be seen on the peg view, and up to 6 mm of displacement is common up to 4 years old and may be seen in patients up to 7 years old. Anterior wedging of up to 3 mm of the vertebral bodies should not be confused with compression fracture. This finding can be profound at C3. Prevertebral swelling of 6 mm or less is considered normal at C3. Widening of prevertebral soft tissues in children can be due to expiration, and if suspected, a repeat lateral film in inspiration and mild extension should be performed.

Answer 202

**Predental space of 6 mm in flexion** The maximum predental space is 2.5–3 mm in an adult and 5 mm in a child. Any widening suggests injury to the alar ligamentous complex in the context of trauma. Other causes of widening are Down’s syndrome, rheumatoid arthritis, neurofibromatosis and osteogenesis imperfecta. Anterior wedging of C3 and pseudo-subluxation at C2–3 and C3–4 are within normal limits in children. Additionally, prevertebral soft tissues can be greater than in the adult, certainly up to 100% of the anteroposterior dimension of the vertebral body at the C6 level.

Answer 203

**Trochlea is present before internal epicondyle**. The appearance of the ossification centres can be remembered by using the mnemonic CRITOE (Capitellum, Radial head, Internal epicondyle, Trochlea, Olecranon, and External epicondyle). These appear at years 1, 5, 5, 7, 10, and 11, respectively. This sequence is very important in the recognition of elbow fractures in children. The apparent appearance of the trochlea or olecranon before the internal (also called medial) epicondyle infers avulsion of the internal epicondyle into the joint space to pose as the not yet formed trochlea or olecranon.

Answer 204

**Salter–Harris type 2 injury**. The Salter–Harris classification is used to describe fractures involving the physis when it is not yet fused. Involvement of the growth plate may cause arrest in growth, with the higher Salter Harris numbers having a greater rate of complications. Type 2 is the most common (75% of physeal injuries). A useful mnemonic is SALTR: Type 1 Slip: only the physis Type 2 Above: a metaphyseal fracture extending to the physis, but not involving the epiphysis Type 3 Low: a fracture involving the epiphysis and physis but not the metaphysis Type 4 Through: a fracture extending from the metaphysis, through the physis to involve the epiphysis Type 5 Rammed: CRUSH injury to all or part of the physis

Answer 205

**Posterior dislocation and medial epicondyle fracture.** The elbow is the most dislocated joint in children (in adults the shoulder and interphalangeal joints are more common). A supracondylar fracture of the elbow is more common in children (65% of elbow fractures) than in adults, who generally suffer a radial head injury (50%). However, in both groups of patients, if dislocation occurs it tends to be posterior dislocation of the radial head and ulna with respect to the distal humerus (85–90%). The most common fracture seen in association with elbow dislocation in children is a fracture of the medial epicondyle or separation of the medial epicondyle. The second most common fracture involves the radial head and neck. In terms of total paediatric elbow fractures, those involving the lateral epicondyle (15%) are next most common after the supracondylar fracture; medial epicondyle fractures comprise approximately 10%.

Answer 206

**Osteochondritis dissecans**. Osteochondritis dissecans is thought to represent **a fracture secondary to avascular necrosis of an area of subchondral bone and cartilage**, and peak incidence is at 12–13 years of age. Repetitive trauma, ischaemia, and familial tendency are common predisposing factors. In the knee, 75% of cases involve the **postero-lateral aspect of the medial femoral condyle**, hence the mnemonic LAME. The disease is bilateral in one-third of patients. A purely cartilaginous fragment will go unrecognized on plain film; a bony fragment and its donor site will not. Instability on MRI is suggested by fragments >1 cm, cysts larger than 5 mm within the donor site, high T2WI signal between the donor site and fragment (even if the cartilage is intact), and loose bodies within the joint.

Answer 207

**Salter Harris II** This is the most common type of Salter Harris fracture. The Salter Harris classification is a widely accepted and useful classification system for describing epiphyseal plate injuries; these represent between 6 and 30% of all paediatric fractures. The most common site is the distal radius, followed by the phalanges of the hands and feet and the distal tibia.

Answer 208

**More than one episode of vomiting** NICE head injury guidelines for children (under 16) advocate CT head imaging if there are three or more discrete episodes of vomiting. All of the other criteria listed are requisites for acute CT head scanning. CSF otorrhoea implies basal skull fracture. Other criteria include: * When the head injury occurs as a result of a dangerous mechanism (high-speed road traffic accident either as a pedestrian, cyclist or vehicle occupant, fall from over three metres, high speed injury from a projectile or an object). * Age > one year; GCS <14 on assessment in the emergency department. * Age > one year: GCS (paediatric) <15 on assessment in the emergency department.

Answer 209

**Osteochondrosis of the capitellum (Panner’s disease)** The most likely cause is osteochondritis of the capitellum. The blood supply to the capitellum is relatively fragile and osteochondritis usually occurs following a minor injury. The condition usually resolves spontaneously with no long-term complications. Osteochondritis dessicans tends to occur in adolescents and often produces a loose body within the joint causing symptoms of locking.

Answer 210

**MRI C spine** MRI should be the next investigation in a child of this age group. A ligamentous injury is more likely and therefore CT of the C spine may be falsely reassuring. However, in some centres the availability of MRI may be limited and a CT will often be performed in the first instance. Flexion/extension views should not be done in the acute setting. A trauma oblique view is performed in some institutions instead of a swimmer’s view and may be used to clear the cervicothoracic junction.

Answer 211

**D** * I: Slipped through growth plate * II: Above (metaphysis and growth plate) * III: Lower (growth plate and epiphysis) * V: Compression and damage

Answer 212

**Spondylolisthesis** Back pain in adults is common and most frequently non-specific. In contrast, back pain in children is less common and often caused by a serious underlying condition. **Spondylolysis** is a **defect in the pars interarticularis**, the weakest part of the vertebra, and is an acquired condition even in childhood, where it is usually due to repetitive microtrauma in athletically active children. In isolation, it does not cause neurological symptoms, but **bilateral defects can allow slippage of one vertebra over another, creating an abnormality of alignment, a spondylolisthesis.** Disc herniation in children is rare and occurs as a result of a traumatic event rather than degeneration. It is usually lateral. **Scheuermann’s** disease is associated with a **kyphotic deformity.**

Answer 213

**Avulsed medial epicondyle** There are six ossification centres around the elbow. The absolute age at which they appear varies slightly, but the order of appearance does not. The order in which they appear is capitellum, radial head, internal (medial) epicondyle, trochlea, olecranon and external (lateral) epicondyle. This can be remembered as ‘CRITOE’, with typical ages in boys of 1, 5, 7, 10, 10 and 11 years, being up to 2 years earlier in girls. The importance of the order is in recognizing medial epicondyle avulsion injuries, which are relatively common due to the powerful forearm flexors. The medial epicondyle epiphyseal fragment is pulled medially into the joint to lie in the region of the trochlea. This gives the appearance of the ‘C’, ‘R’ and ‘T’ but no ‘I’, and therefore can be identified as pathological.

Answer 214

**Thick periosteum** Paediatric fractures are commonly classified into five types: plastic deformation, buckle fracture, greenstick fracture, complete fracture and physeal injuries. The most important anatomical characteristics in the paediatric skeleton that result in these fracture patterns are the presence of growth plates and the thick periosteum, which in children contributes immensely to rapid fracture healing and helps in the reduction and the maintenance of reduction. It also decreases the likelihood that fractures will involve the entire circumference of the bone, creating torus and greenstick patterns, with the intact periosteum on one cortex preventing displacement of that cortex and acting as a hinge (particularly in greenstick patterns). This allows for accurate reduction with manipulation and retention with a cast, avoiding open reduction and internal fixation.

Answer 215

**Mesenteric rupture** The most common mechanism for traumatic mesenteric rupture is a road traffic collision, although such an injury can occur in children following any blunt abdominal trauma, with handlebar injuries and child abuse being well-recognized causes. Use of a lap belt makes children more prone to the injury. Bowel perforation, infarction and active haemorrhage are indications for immediate surgery and can be identified on CT. Most of the remaining cases are treated conservatively. Free intraperitoneal air, extraluminal contrast or visible bowel wall defect is specific for perforation. Free fluid, haemorrhage and stranding are seen in perforation or mesenteric injury, with fluid at the root more likely to indicate the latter. **Hyperattenuation of the pancreas, kidneys and bowel wall is a feature of hypoperfusion, along with small-calibre aorta and vena cava**, and should not be mistaken for visceral injury.

Answer 216

**Radial head** Avulsion fractures occur in both adults and children due to a tensile force being applied through a tendon or ligament where the skeleton is the weakest link. The mechanism can be either a powerful normal contraction (as seen in sportspersons) or an abnormal force, as in anterior teardrop fractures of the cervical spine seen in road traffic collisions. They may be acute or chronic from repetitive minor trauma. In the paediatric skeleton, the spectrum of avulsion injuries is larger, as many of the growing apophyses are weaker than the soft-tissue structures that attach to them. For example, avulsion of the tibial spine in the knee is the paediatric equivalent of a ruptured anterior cruciate ligament, and it follows therefore that the ligament rupture is rarely seen in children. Fractures of the radial head in both adults and children are usually due to compressive forces, although one can see avulsion of the radial tuberosity by the biceps brachii tendon.

Answer 217

**Supracondylar fracture** Elevation of the anterior humeral fat pad into a triangular shape (the sail sign) occurs secondary to elbow effusion. In the context of trauma, the probable cause is haemarthrosis. The posterior fat pad lies in the olecranon fossa and should not be visible on normal lateral radiographs in 90 of flexion, although it may normally be seen in extension, when it is displaced by the olecranon process. In trauma the posterior fat pad may be elevated out of the fossa by effusion, and is particularly valuable in predicting an intra-articular disease process when no bony abnormality is apparent radiographically. Rarely the fat pad sign may not be apparent, due to capsular rupture or surrounding soft-tissue swelling. **In children, supracondylar fractures represent around 60% of elbow fractures; other causes include medial and lateral epicondyle injuries.** The commonest **adult** elbow fracture is a fracture of the **radial head or neck.**

Answer 218

**Tillaux fracture** Tillaux fracture is a **Salter–Harris type III** fracture of the **anterolateral distal tibial epiphysis** resulting from an abduction and external rotation injury. This is **seen in adolescents since the distal tibial epiphysis fuses in a medial to lateral direction and is not seen in adults where the growth plate has fused.** **Pilon** fractures are **comminuted fractures of the plafond.** **Maisonneuve** fracture involves **tearing of syndesmosis, posterior malleolus,** capsular injury, and **fracture of the proximal fibula**. Le Fort fracture involves the distal fibula and the anterior tibiofibular ligament.

Answer 219

**Galeazzi fracture dislocation** Galeazzi fracture dislocation Characterised by fracture of the distal shaft radius and dislocation at the distal radioulnar joint.

Answer 220

**To arrange a CT brain that night, followed by a skeletal survey the following morning**. **A metaphyseal fracture in a non-ambulant child is due to NAI until proven otherwise**. Of all the injuries described in NAI, none is more speciﬁc than the metaphyseal fracture. Royal College guidelines state that skeletal surveys should be performed by two radiographers and the ﬁlms reviewed by a consultant radiologist before the child leaves the x-ray department in cases of suspected NAI. Thus, it is more appropriate that such a skeletal survey should be performed within normal hours, although usually within 24 hours of admission. Also, the guidelines state that **any child under the age of 1 year who has evidence of physical abuse should undergo neuroimaging** (as well as any child with evidence of physical abuse and encephalopathic features/focal neurology/haemorrhagic retinopathy). Thus, a CT brain is indicated. The guidelines infer this CT brain should be performed as soon as the child is stabilized following admission. IBSs and follow-up imaging may be relevant depending on the circumstances. A ‘babygram’ (a ﬁlm which includes the whole of the infant) is not appropriate. At radiology trainee level it is important to remember that due to the severe consequences for child and family of correctly/incorrectly making or missing the diagnosis of NAI, consultant involvement is necessary, both of the clinical and radiological teams.

Answer 221

**Inter-hemispheric subdural haematoma**. NAI is a difﬁcult and controversial subject with no absolute pathognomonic features. It is, however, the leading cause of morbidity and mortality in abused children. Inter-hemispheric subdural haematoma has the highest speciﬁcity of abuse for any intracranial injury. Subarachnoid haemorrhage is also a much more common injury in NAI. Skull fractures are relatively common in both accidental and non-accidental injury. In addition, there are no fracture patterns that are speciﬁc for abuse, although fractures that cross sutures and bilateral fractures are more common in the setting of NAI. Skull radiography is preferred over CT for fracture assessment. Extradural haematoma is much more often accidental than inﬂicted and may result from relatively short distance falls. Bilateral frontal enlargement of the subarachnoid space is a feature of benign external hydrocephalus.

Answer 222

**Scapula fracture** A scapula fracture implies a high-energy injury and would be concerning for non-accidental injury. Posterior rib fractures, particularly if of differing ages, are also specific for nonaccidental injury. Toddlers who are just beginning to mobilise independently may sustain a spiral fracture of the tibia, sometimes known as a ‘toddler’s fracture’. Salter Harris fractures are common in children and are most seen at the distal radius and the phalanges of the hands and feet. **Suspicious** Lower limb fracture in a non walker. Metaphyseal fractures Posterior ribs Scapula Sternum Skull - Non-parietal - crossing sutures Multiple fractures of different ages Discrepancy between history and injuries Delay in seeking medical attention.

Answer 223

**Scapular fracture** High specificity fractures are: **Scapula, posterior ribs, metaphyseal and sternal fractures** B-E are moderately specific.

Answer 224

**Subdural haematoma** The child has features of non-accidental injury. **Subdural haematoma is the commonest** CT ﬁnding and is frequently **interhemispheric**, although shallow posterior fossa subdural haematomas are also seen. If there is more than one subdural haematoma, varying densities can be seen, indicating differing ages. Non-accidental injury is the commonest cause of serious intracranial injury in children less than 1 year old.

Answer 225

**Non-accidental** **Injury** Duodenal intramural haematoma is usually traumatic, particularly following bicycle-handlebar accidents and lap-belt injuries. However, it is also commonly seen in non-accidental injury, where the mechanism of injury is thought to be a blunt blow to the abdomen that compresses the duodenum against the vertebral column. Trauma to the duodenum may result in duodenal rupture, intramural tear or, most commonly, intramural haematoma. Ultrasound appearances are of an echogenic intramural mass that becomes progressively hypoechoic with maturation of the haematoma. There may be associated deformity or obstruction of the duodenum. CT may demonstrate free intraperitoneal ﬂuid, though free air and frank perforation are uncommon. Spontaneous intramural haematoma may occur in Henoch–Scho¨nlein purpura, but other features of the condition would be expected to be present. It may occur with anticoagulant therapy and blood dyscrasias.

Answer 226

**Diffuse cerebral swelling** After a drowning incident, a CT scan of the brain would typically show diffuse cerebral swelling due to hypoxia. The presence of midline shift indicates herniation, which may occur later in the course.

Answer 227

**Diaphyseal transverse** Non-accidental injury (NAI) is the third leading cause of death in children after sudden infant death and true accidents, and represents about 1% of all childhood trauma. The hallmark of NAI is multiple fractures at different sites and of different ages, suggesting repeated episodes of abuse. Often, as these fractures are not treated, they show exuberant callus formation. Several locations and patterns of injury have been described as relatively speciﬁc for NAI. However, a study of over 400 fractures showed that the most common presentation was a single, simple, transverse fracture of the middle third of a long bone, which is indistinguishable from a fracture sustained in a true accident. Whole-body imaging with isotope bone scan is sensitive for identifying all sites of injury in equivocal cases.

Answer 228

**Spiral tibial fracture** In ambulant children, spiral fractures of the tibia (toddler’s fractures) are seen reasonably commonly, often with no history of signiﬁcant trauma, and are not by themselves suggestive of abuse. However, a spiral fracture in a non-ambulant child is quite suggestive of non-accidental injury (NAI). The metaphyseal corner fracture is the most speciﬁc of all the ﬁndings observed in NAI and is considered virtually pathognomonic of abuse. The injury consists of a series of microfractures orientated parallel to the physis, due to a shearing injury across the bone end. This mechanism of injury is not seen in blunt trauma or falls, although similar lesions may be seen in some metabolic diseases (particularly scurvy). Older children and adults may suffer rib fractures after trauma such as falls and road trafﬁc accidents. However, they are unusual in infants and are strongly correlated with inﬂicted injury caused by chest wall compression.

Answer 229

**Battered child syndrome** The classical metaphyseal fracture is considered virtually pathognomic of battered child syndrome from indirectly applied forces during shaking.

Answer 230

**Decreased marrow intensity on 2 consecutive vertebrae on T1 MR is characteristic** Diskitis is the most common paediatric spine pathology. Staphylococcus aureus is the most common causative organism. The peak ages are 6 months-4 years and 10-14 years. L3-4 and L 4-5 are most affected sites.

Answer 231

**MRI** Discitis is the commonest paediatric spinal disease. It is secondary to bacterial invasion of the disc through the endplate. Plain ﬁlms typically show reduced disc-space height and loss of clarity of the endplates in the acute phase. MRI is the best investigation, as it is the most sensitive. Reduced T1 signal is seen in the adjacent marrow due to oedema, with initially variable, then increased, T2 signal. Complications such as epidural abscess are well demonstrated. CT will show the endplate changes and any paravertebral inﬂammatory mass. Bone scans and white cell scans have much poorer sensitivity than MRI, though this is improved with the use of SPECT.

Answer 232

**Idiopathic** The Scoliosis Research Society has defined scoliosis as a lateral curvature of the spine of greater than 10. It is idiopathic in 70% of cases. Most children who present with idiopathic scoliosis do so in adolescence. There is a strong hereditary component to the idiopathic form. Congenital scoliosis is usually associated with vertebral anomalies such as block vertebrae or butterfly vertebrae. The magnitude of the curve is measured using the ‘Cobb’ angle, which can be determined on an AP plain film of the spine.

Answer 233

**Anechoic cystic mass anterior to sternocleidomastoid near the angle of the mandible**. The other options are typical locations for cystic hygroma, infantile haemangioma, thyroglossal cyst, and first branchial cleft cyst, respectively. The majority (75%) of branchial cleft cysts are remnants of the second branchial cleft. Cystic hygromas are lymphatic malformations (lymphangiomas) that result from blockage of lymphatic channels. Most present before 2 years of age. Most are slow growing but can suddenly enlarge following infection or haemorrhage into the lesion. Infantile haemangiomas usually grow rapidly until 9–10 months of age, followed by spontaneous resolution, which can take up to 10 years. Thyroglossal cysts are remnants of the thyroglossal duct, which extends from the foramen caecum at the base of the tongue to the pyramidal lobe of the thyroid. The majority (65%) are infrahyoid.

Answer 234

**Calcification** **Calcification is the most specific feature of retinoblastoma** and is apparent in 95% of cases. Other features of retinoblastoma include **hyperattenuating mass extending into the vitreous** and secondary **retinal detachment**. Contrast enhancement is seen in <30% of cases. The globe is normal sized. The **non-neoplastic causes of leucocoria**, the so-called pseudoretinoblastomas, include persistent hyperplastic primary vitreous **(PHPV)**, **Coat’s disease**, and toxocara endophthalmitis. CT findings in **PHPV** include **micro-opthalmia and an enhancing retrolental mass**. Coat’s disease is a vascular malformation of the retina and presents with a hyperattenuating globe and an enhancing subretinal exudate on CT. CT features of toxocara are non-specific and similar to Coat’s disease. Secondary retinal detachment may be seen. None of the pseudoretinoblastomas exhibit calciﬁcation.

Answer 235

**Microphthalmia** Primary vitreous normally involutes by the sixth foetal month, but occasionally persists and undergoes hyperplasia. It is the second most common cause of unilateral leukokoria behind retinoblastoma. It may be bilateral as a part of congenital syndromes such as Norrie disease. Key imaging findings are microopthalmia (small hypoplastic globe) with an enhancing central soft-tissue band extending from the lens (retrolental) through the vitreous body to the back of the orbit (i.e. following Cloquet’s canal). Calcifications are not a feature (cf retinoblastoma – the most common cause of orbital calcifications). Both may show a hyperechoic focus on ultrasound and a dense vitreous on CT. PHPV is associated with a small optic nerve whereas retinoblastoma may show optic nerve enlargement due to tumour extension and may also demonstrate macro-opthalmia. (Refs: Dahnert p. 350; Grainger & Allison p. 1394)

Answer 236

**Retinoblastoma** Retinoblastoma is a highly malignant primary ocular tumour of childhood occurring in sporadic and heritable form and arising from primitive photoreceptor cells of the retina (in the group of primitive neuroectodermal tumours). It is the most serious intraocular process in a child, and calciﬁcation in a paediatric orbit must be considered to represent retinoblastoma until proved otherwise. Once tumour extends beyond the orbit, mortality rate is virtually 100%. Heritable forms are often multifocal in a single orbit or bilateral. Trilateral retinoblastoma is bilateral orbital tumours and associated pineoblastoma.

Answer 237

**Epidermoid cyst** Both epidermoid and dermoid cysts appear as unenhanced, well-circumscribed, low-density masses. Both can cause scalloping and sclerosis and even destruction of the adjacent bone. Epidermoids do not calcify and do not contain fat (negative Hounsfield units). The presence of calcification and/or fat is characteristic of dermoid cysts. Dermoids and epidermoids have low signal on T1 (unless the former contains fat) and high signal on T2, FLAIR and diffusion-weighted imaging. Both may be found in several locations in the orbit, but most frequently superiorly and temporal. They are congenital cysts but many become evident in the second and third decades. Teratomas are evident at birth as grossly visible cystic orbital masses. They tend to affect girls, are unilateral and grow rapidly. Conjunctival choristomas (dermolipomas) are less dense than solid dermoid and contain more adipose tissue.

Answer 238

**Pleomorphic adenoma**. This is the most common benign salivary gland tumour in children and usually appears in later childhood or adolescence. The tumour originates in the parotid gland in up to 90% of cases. Haemangiomas are the next most common benign lesion. They are usually seen in the first 6 months of life and have a female predilection. They are hypoechoic and display a variable degree of abnormal vasculature. Parotitis is usually due to mumps and results in a tender gland, which is diffusely enlarged with a heterogenous echotexture on ultrasound. Warthin tumour is a well-circumscribed cystic solid lesion, usually towards the tail of the parotid gland. It is the most common lesion to manifest as multifocal or bilateral masses. Primary lymphoma of the salivary glands is rare, but most often involves the parotid. Ultrasound features of lymphoma include a well-defined, homogenous, hypoechoic mass without calcification.

Answer 239

**A highly vascular nasal mass causing widening of the pterygopalatine fissure** Juvenile angiofibromas are the most common benign nasopharyngeal tumour. They occur almost **exclusively in teenage males**. In most cases CT allows accurate diagnosis, although MRI may be used pre-operatively to assess soft-tissue involvement. The tumours typically start in the pterygopalatine fossa and cause local bone erosion. On CT, the presence of a **nasal mass and a widened pterygopalatine fissure is pathognomonic of the condition**. The tumour may invade the sphenoid sinus, the middle cranial fossa (via the superior orbital fissure), the orbit (via the inferior orbital fissure), the infratemporal fossa, or extend through the sphenopalatine foramen. The tumour may be very fibrous but tends to be **highly vascular** such that it only enhances immediately after bolus injection. **Biopsy is therefore contraindicated**. Angiography is not required to obtain the diagnosis but may be utilised for pre-operative planning or during therapeutic embolisation.*

Answer 240

**Widening of the superior orbital fissure** Widening of the pterygopalatine fossa with anterior bowing of the posterior antral wall, invasion of the sphenoid sinus (in 2/3), widening of the superior and inferior orbital fissures, and immediate enhancement after contrast injection are all features. On MR, punctuate hypodensities on T1 are due to the highly vascularised stroma.

Answer 241

**Thyroglossal duct cyst** Thyroglossal duct cyst is the commonest congenital neck mass. It presents as a painless midline neck lump, which moves superiorly on protruding the tongue. Imaging shows a smooth cystic lesion, which may take up pertechnetate on nuclear medicine studies due to the presence of functioning thyroid tissue. Ectopic thyroid is an important differential diagnosis, as this may be the only functioning thyroid tissue present and therefore should not be excised. Laryngoceles and branchial cleft cysts present with masses to the side of the neck rather than in the midline. Lymphadenopathy will usually present as solitary or multiple solid lumps in either side of the neck but may be ‘cystic’ when necrotic.

Answer 242

**Internal maxillary artery** Juvenile angiofibromas are the commonest benign tumour of the nasopharynx and can grow to enormous sizes. They tend to present in teenagers with recurrent and severe epistaxis, as well as nasal obstruction. They are highly vascular, and biopsy is contraindicated. In most cases, they are supplied primarily by the internal maxillary artery.

Answer 243

**Branchial cleft cyst** The described features are typical of a branchial cleft cyst arising from the second branchial cleft. The mass displaces the sternocleidomastoid posteriorly, and the carotid and internal jugular vessels posteromedially. The pointing between the internal and external carotid arteries is pathognomonic. Cystic hygromas present in infancy as a cystic mass in the posterior cervical space. Abscesses present with associated symptoms and a painful red swelling, though imaging findings may be similar. Carotid body tumours are solid, highly vascular masses lying between the internal and external carotid artery origins.

Answer 244

**Fibromatosis colli** This presents as a mass in the sternocleidomastoid muscle 2 or more weeks after birth. A history of birth trauma may be present. This presents with a torticollis with the chin pointed away from the mass. Ultrasound is diagnostic and shows a focal of diffuse enlargement of the muscle with the mass following the course of the muscle.

Answer 245

**Haemangioma** These are benign tumours which can grow to cause progressive proptosis. Haemorrhage may present with acute symptoms and swelling. Flow voids, when present, are highly suggestive of a haemangioma.

Answer 246

**Rhabdomyosarcoma** This is the most common primary orbital tumour in childhood. This usually arises from the mesenchymal tissues and the lesion is usually non-invasive.

Answer 247

**Thyroglossal duct cyst** This is the most common congenital neck mass seen in children less than 10 years of age. The thyroglossal cyst typically moves on tongue protrusion. On MRI, the lesion returns low signal on T1 and high on T2.

Answer 248

**Sagittal suture**. Craniosynostosis refers to premature closing of sutures and is often present at birth. It may be primary or secondary to bone dysplasias or haemoglobinopathy, or as part of a generalized syndrome. Scaphocephaly is the most common craniosynostosis, results from closure of sagittal suture and results in a long skull. Brachycephaly arises from bilateral closure of the coronal suture, resulting in a short, tall skull. Unilateral fusion of the lambdoid suture is seen in plagiocephaly, giving a lopsided skull. Trigonocephaly is a forward-pointing skull from premature closure of the metopic suture. Intrauterine closure of coronal, sagittal and lambdoid sutures give rise to the cloverleaf skull, which may be associated with thanatophoric dysplasia.

Answer 249

**Multiple flow voids within the basal ganglia bilaterally**. The history and ethnic origin of the patient suggest moyamoya syndrome. This is an idiopathic progressive arteriopathy of childhood resulting in **narrowing of the distal internal carotid arteries and lenticulostriate collateralization**. This collateralization causes the **multiple basal ganglia flow voids, likened to a ‘puff of smoke’ (moyamoya in Japanese) on angiography.** Secondary causes of moyamoya collateralization include neurofibromatosis type 1, post-radiation therapy and sickle cell anaemia. Irregular beading of the extracranial internal carotid arteries is seen in fibromuscular dysplasia.

Answer 250

**Caudal to cranial, posterior to anterior, deep to superficial**. Myelination is an important feature of the maturation of the normal central nervous system. It is a dynamic process that begins in utero and continues after birth in a predetermined manner. It is well demonstrated on MRI, where initially white and grey matter show the reverse signal characteristics to those seen in the adult brain, with the white matter appearing of lower signal on T1 and higher signal on T2 than grey matter. As myelination occurs, the white matter gains fat content and so becomes of higher signal on T1 and lower signal on T2 than grey matter, with completion at around 9 months. The process progresses caudal to cranial, posterior to anterior, and deep to superficial, beginning with the brain stem and cerebellum, then the basal ganglia, with the final areas to mature being the peripheral cortical white matter.

Answer 251

**Coronal T2W**. Mesial temporal sclerosis is a pattern of hippocampal neuronal loss that can occur with long-standing temporal lobe epilepsy because of excessive neuronal depolarization leading to cytotoxic oedema. Three patterns of loss are described, with relative sparing of the CA2 subfield often a feature. The typical findings are of asymmetrical atrophy of the hippocampus with abnormally high signal returned on T2W images. Ipsilateral findings in the limbic system include atrophy of the fornix and maxillary body. Cortical abnormalities may exist in the temporal cortex, and this is best evaluated on high-resolution T1 sequences.

Answer 252

**Rectus femoris**. Rectus femoris is attached to the anterior inferior iliac spine.

Answer 253

**Prolonged partial asphyxia**. There are three patterns of hypoxic ischaemic encephalopathy. Periventricular leukomalacia occurs in watershed areas of arterial distribution. It is caused by prolonged partial asphyxia in preterm or term babies. Acute profound asphyxia causes lesions in the deep grey matter, hippocampus and dorsal brain stem. Lastly, there is multicystic encephalomalacia that follows devastating encephalopathy and generalized brain oedema.

Answer 254

**Thyroglossal duct cyst** This is the most common congenital neck mass seen in children less than 10 years of age. The thyroglossal cyst typically moves on tongue protrusion. On MRI, the lesion returns low signal on T1 and high on T2.

Answer 255

**Sagittal suture**. Craniosynostosis refers to premature closing of sutures and is often present at birth. It may be primary or secondary to bone dysplasias or haemoglobinopathy, or as part of a generalized syndrome. Scaphocephaly is the most common craniosynostosis, results from closure of sagittal suture and results in a long skull. Brachycephaly arises from bilateral closure of the coronal suture, resulting in a short, tall skull. Unilateral fusion of the lambdoid suture is seen in plagiocephaly, giving a lopsided skull. Trigonocephaly is a forward-pointing skull from premature closure of the metopic suture. Intrauterine closure of coronal, sagittal and lambdoid sutures give rise to the cloverleaf skull, which may be associated with thanatophoric dysplasia.

Answer 256

**Multiple flow voids within the basal ganglia bilaterally**. The history and ethnic origin of the patient suggest moyamoya syndrome. This is an idiopathic progressive arteriopathy of childhood resulting in narrowing of the distal internal carotid arteries and lenticulostriate collateralization. This collateralization causes the multiple basal ganglia flow voids, likened to a ‘puff of smoke’ (moyamoya in Japanese) on angiography. Secondary causes of moyamoya collateralization include neurofibromatosis type 1, post-radiation therapy and sickle cell anaemia.

Answer 257

**Caudal to cranial, posterior to anterior, deep to superficial** Myelination is an important feature of the maturation of the normal central nervous system. It is a dynamic process that begins in utero and continues after birth in a predetermined manner. It is well demonstrated on MRI, where initially white and grey matter show the reverse signal characteristics to those seen in the adult brain, with the white matter appearing of lower signal on T1 and higher signal on T2 than grey matter. As myelination occurs, the white matter gains fat content and so becomes of higher signal on T1 and lower signal on T2 than grey matter, with completion at around 9 months. The process progresses caudal to cranial, posterior to anterior, and deep to superficial, beginning with the brain stem and cerebellum, then the basal ganglia, with the final areas to mature being the peripheral cortical white matter.

Answer 258

**Coronal T2W** Mesial temporal sclerosis is a pattern of hippocampal neuronal loss that can occur with long-standing temporal lobe epilepsy because of excessive neuronal depolarization leading to cytotoxic oedema. Three patterns of loss are described, with relative sparing of the CA2 subfield often a feature. The typical findings are of asymmetrical atrophy of the hippocampus with abnormally high signal returned on T2W images. Ipsilateral findings in the limbic system include atrophy of the fornix and maxillary body. Cortical abnormalities may exist in the temporal cortex, and this is best evaluated on high-resolution T1 sequences.

Answer 259

**Rectus femoris** Rectus femoris is attached to the anterior inferior iliac spine.

Answer 260

**Prolonged partial asphyxia** There are three patterns of hypoxic ischaemic encephalopathy. Periventricular leukomalacia occurs in watershed areas of arterial distribution. It is caused by prolonged partial asphyxia in preterm or term babies. Acute profound asphyxia causes lesions in the deep grey matter, hippocampus and dorsal brain stem. Lastly, there is multicystic encephalomalacia that follows devastating encephalopathy and generalized brain oedema.

Answer 261

**Tapering toward caudo-thalamic groove** Prematurity and low birth weight are amongst risk factors for GMH. Chord plexus is attached to inferomedial aspect of ventricular floor, tapering toward cardiothalamic groove and never anterior to the foramen of Monro.

Answer 262

**The hyperechoic changes are anterior to the caudothalamic groove** Germinal matrix is highly vascular tissue seen at 24–32 weeks’ gestational age, located anterior to the caudothalamic groove and inferior to the lateral ventricles. It is at risk of hypoxaemia and ischaemia. Haemorrhage here can be promoted by trauma at birth or coagulopathy including rhesus incompatibility. Germinal matrix haemorrhage less than 7 days old is hyperechoic but without shadowing. Within 2–3 weeks, the abnormal area decreases in size and the echogenicity reduces. Periventricular leukomalacia is white matter necrosis following hypoxaemia. It is seen in 5–10% of preterm babies. It occurs in arterial watershed areas and may appear acutely as a broad region of periventricular increased echogenicity. Cystic degeneration may follow 2 weeks or more.

Answer 263

**Intraparenchymal haemorrhage** Subependymal haemorrhage (grade 1) usually has no long-term consequence. Mortality rates for intraventricular haemorrhage, intraventricular haemorrhage with ventricular dilatation and intraparenchymal haemorrhage are 10%, 20% and more than 50%, respectively. These represent grades 2, 3 and 4 haemorrhage. Normal choroid plexus pulsates while haematoma at the same location is not pulsatile.

Answer 264

**Subependymal haemorrhage with ventricular dilatation** The differential diagnosis is from a normal choroid plexus. However, if the blood fills the ventricle then the diagnosis is easy.

Answer 265

**Cytomegalovirus infection** Intracranial calcifications are seen in congenital TORCH infections, tuberous sclerosis, Sturge–Weber syndrome, bacterial meningitis with ventriculitis and teratoma. Cytomegalovirus infection is the most common TORCH infection. Periventricular and subependymal calcifications are common manifestation of cytomegalovirus infection. Calcifications in cytomegalovirus tend to be limited to the subependymal region, while in toxoplasmosis they are seen throughout the parenchyma. Calcifications are much less in herpes simplex and rubella. In tuberous sclerosis, calcifications are likely to be seen in adolescence.

Answer 266

**Delayed sulcation**. Signs of ACC include absence of the cavum septum pellucidum, colpocephaly, high-riding third ventricle, and widening of the inter-hemispheric ﬁssure. ACC is reported to be isolated in <10% on foetal MR imaging. Sulcation delay is present in most foetuses with ACC (particularly those imaged at <30 weeks gestation), including those with good neurodevelopmental outcome, implying a global white matter dysgenesis. Periventricular nodular heterotopia and parenchymal T2WI signal hypointensity are usually seen in association with abnormal sulcal morphology. Associated posterior fossa abnormalities are also common, with cerebellar hemispheric abnormalities seen more than abnormalities of the vermis. Brainstem abnormalities typically occur in association with a cerebellar abnormality.

Answer 267

**Agenesis of corpus callosum** Absence of septum pellucidum, corpus callosum and cavum septum pellucidum, and wide separation of the lateral ventricles, are other features of agenesis of the corpus callosum.

Answer 268

**Scaphocephaly** Craniosynostosis means premature closure of a suture of the skull, and skull growth is arrested in the direction perpendicular to the affected suture. Craniosynostosis of the sagittal suture therefore results in a head shape that is abnormally long and narrow and has the appearance of an upturned boat. This is called scaphocephaly (or dolichocephaly) and accounts for 60% of all craniosynostoses. Closure of the coronal suture accounts for 20% and results in a short, wide head called brachycephaly. Trigonocephaly is caused by craniosynostosis of the metopic suture and results in a forward-pointing head. Oxycephaly is the most extreme form, and all sutures may be affected, resulting in a high head. Plagiocephaly is unilateral craniosynostosis. Early recognition of all types is important to prevent permanent deformity and allow for surgical correction. Causes may be primary or secondary to dysplasia, several genetic syndromes, microcephaly, and metabolic or haematological conditions.

Answer 269

**Intracerebral cleft lined by grey matter connecting the lateral ventricle to the subarachnoid space**. Schizencephaly can be deﬁned as open or closed lip, depending on the presence of separation of the cleft walls. The remaining options describe lissencephaly, polymicrogyria, trans mantle heterotopia, and subcortical band heterotopia, respectively. Trans mantle heterotopia can potentially be confused with closed lip schizencephaly.

Answer 270

**Deep grey matter structure ** The brainstem, cerebellum and deep grey structures are spared in mild-moderate ischemia. Severe hypoxic injury involves the ventral and lateral thalamus, posterior putamen, perirolandic regions and corticospinal tracts.

Answer 271

**Periventricular leucomalacia**. This refers to white matter necrosis, typically involving the centrum semiovale, and is seen in premature infants. This results from hypoxic-ischaemic injury at the watershed areas, which in premature infants are present in a periventricular location. Porencephaly refers to an area of encephalomalacia, which may or may not communicate with the ventricular system and develops postnatally or in the third trimester. This is the result of a destructive process, such as an intraparenchymal haemorrhage. Sylvian ﬁssure cysts are the most common site for supratentorial arachnoid cysts. Vein of Galen malformations occur in the midline and exhibit Doppler ﬂow. Subependymal cysts are detected in the caudothalamic groove.

Answer 272

**Metachromatic leucodystrophy**. Leucodystrophies are dysmyelinating inherited white matter diseases, which are secondary to lysosomal, peroxisomal, or mitochondrial dysfunction. Metachromatic leucodystrophy is caused by deﬁciency of the lysosomal enzyme ayrlsulfatase A. The ‘tigroid’ pattern relates to sparing of perivascular white matter.

Answer 273

**Diffusion-weighted MRI** The history and MRI findings are suggestive of Canavan disease. This is an autosomal recessive disorder due to deficiency of the enzyme aspartoacylase. Accumulation of N-acetylaspartic acid (NAA) in the brain pursues and leads to leukodystrophy. Histology reveals soft and gelatinous white matter. Change is most prominent in the deeper cortex and subcortical white matter, with relative sparing of the deeper white matter and internal capsule. On T2-weighted MRI, the globus pallidus is always of high signal intensity, with frequent involvement of the thalamus but with relative sparing of the caudate and putamen. The main differential diagnosis on imaging is Alexander disease, a rare disorder which shows no pattern of inheritance. Both conditions are leukodystrophies with macrocrania. Brain biopsy can be used to differentiate. Diagnosis of Canavan disease is also possible with proton MR spectroscopy which shows a characteristic increase in the NAA peak. Levels of NAA are also abnormally high in urine and there will be a deficiency of aspartoacyclase in cultured skin fibroblasts. Aspartoacyclase is not present in plasma or blood cells. Diffusion-weighted MRI will add little to the information already obtained with T2-weighted imaging.

Answer 274

**Adrenoleukodystrophy** Features describe adreno-lukodystrophy, an X linked recessive condition. Patients also have adrenal gland insufficiency with increased pigmentation and raised Adrenocorticotropic Hormone (ACTH) levels.

Answer 275

**Enlargement of the posterior** **fossa**. Dandy–Walker variant is more common, accounting for a third of all posterior fossa malformations, but less severe than the malformation. Enlargement of the posterior fossa is not a feature. Cystic dilatation of the fourth ventricle with vermian dysgenesis is characteristic of both. Associated CNS anomalies, usually of the midline, are also seen, as is ventriculomegaly, although both are more common with Dandy–Walker malformation.

Answer 276

**Caudal displacement of the cerebellar tonsils**. Chiari II is seen in all patients with open spinal dysraphisms, such myelomeningocoele. Lacunar skull (luckenshadel) is also associated with Chiari II. Cervicomedullary kinking is common to both, although more so with Chiari II. Caudal displacement of the cerebellar tonsils is a feature of Chiari I, whereas in Chiari II the vermis herniates into the foramen magnum and the tonsils are lateral to the medulla.

Answer 277

**Enlargement of the pituitary fossa** The other features are common to both.

Answer 278

**Chiari I malformation** Chiari I malformation is characterized by tonsillar ectopia. The fourth ventricle is elongated but normal in position. It is associated with syringo-hydromyelia, hydrocephalus and malformations of the skull base. Chiari II (Arnold–Chiari) malformation is characterized by hindbrain abnormalities, with caudal displacement of the fourth ventricle. A lumbar myelomeningocele is seen in over 95% of cases. Chiari III malformation is rare and has a high cervical/low occipital meningomyelo-encephalocele. Survival beyond infancy is unusual. In Dandy–Walker syndrome, there is enlargement of the posterior fossa with cystic dilatation of the fourth ventricle and abnormalities of the cerebellar vermis. Diastematomyelia results in sagittal splitting of the spinal cord into two hemi-cords, and is sometimes associated with a myelomeningocele.

Answer 279

**Chiari type II malformation** There is displacement of the fourth ventricle, brainstem and cerebellum into the cervical spinal canal, and it is almost always associated with myelomeningocele. Other findings may include beaked tectum, fenestration of falx, hydrocephalus, colpocephaly and dysgenesis of corpus callosum. Chiari type I may show benign cerebellar ectopia up to 5 mm below foramen magnum. There is no hydrocephalus or meningomyelocele. Alobar holoprosencephaly shows a large single ventricle without occipital or temporal horns. There is no hemispheric development of the brain. Hydranencephaly represents liquefaction of cerebral hemispheres, which are replaced with cerebrospinal fluid, leptomeninges sac and remnants of cortex. Dandy–Walker malformation is characterised by an enlarged posterior fossa, dysgenesis of cerebellar vermis and dilatation of 3rd ventricle.

Answer 280

**Dandy–Walker malformation** These are the typical features seen in Dandy–Walker malformation.

Answer 281

**Sturge Weber syndrome**. The gyriform low T2WI signal corresponds to cortical calciﬁcation, which in association with unilateral atrophy and leptomeningeal enhancement is characteristic of Sturge Weber syndrome, one of the neurocutaneous phakomatoses. Other ﬁndings include calvarial thickening and choroid plexus angiomas. Associated facial port wine stain in the distribution of the trigeminal nerve is classic.

Answer 282

**Neurofibromatosis type 2** The phakomatoses are neuroectodermal disorders with skin and central nervous system manifestations. Neuroﬁbromatosis type 2 (central neuroﬁbromatosis) accounts for only 10% of cases, type 1 accounting for 90%. Although the hallmark ﬁnding of type 2 is bilateral acoustic schwannomas, multiple meningiomas, particularly in a child, should bring the diagnosis to mind. A mnemonic for remembering the associations is MISME (multiple inherited schwannomas, meningiomas and ependymomas), and tumours may be seen in the brain or spinal cord. In the spine, multiple nerve sheath tumours are often located in the cauda equina. Skin manifestations are seen relatively infrequently, unlike in the more common type 1.

Answer 283

**Tuberous sclerosis** Tuberous sclerosis is a member of the phakomatoses, a group of neuroectodermal disorders characterized by coexistence of skin and central nervous system tumours. The classic clinical triad of seizures, learning disability and adenoma sebaceum (a facial rash) is seen in approximately half of presenting patients. Imaging ﬁndings seen on MRI and sometimes CT are periventricular nodules, which often calcify, and ‘cortical tubers’, which represent brain parenchymal hamartomas. These lesions are low signal on T1 and high signal on T2W images, and typically do not enhance. Enhancement of a lesion suggests associated giant cell astrocytoma, which is most seen at the foramen of Monro, where it may obstruct, causing hydrocephalus. Common associations are renal angiomyolipoma, bone abnormalities and spontaneous pneumothorax.

Answer 284

**Renal artery aneurysm** Renal artery stenosis and aneurysms plus abdominal coarctation are associated with neuroﬁbromatosis type 1 (NF1). Renal cysts are found in von Hippel–Lindau syndrome (VHL) and tuberous sclerosis, while renal cell carcinoma is found in VHL. NF1 and VHL are associated with phaeochromocytoma. Angiomyolipomas, usually multiple and bilateral, are found in 50% of cases of tuberous sclerosis.

Answer 285

**Tuberous sclerosis** This is one of the phacomatoses with the classical triad of seizures, adenoma sebaceum and mental retardation. Other findings include hamartoma of kidney (angiomyolipomas), heart (rhabdomyoma) and brain (tubers). These CNS findings are typical, and tubers are seen in the subependymal region, subcortical white matter and cortex. These commonly calcify. Sturge-Weber syndrome is characterised by multiple angiomatosis in face, eyes and leptomeninges. Sarcoidosis often affects the meninges, peripheral nerves and patients may have multiple sclerosis like symptoms. Klippel–Trenaunay syndrome presents with port-wine naevus, gigantism and varicose veins in affected limb. Neurofibromatosis type 2 is characterised by bilateral schwannomas, meningiomas and ependymomas.

Answer 286

**Medulloblastoma**. This is the most common malignant posterior fossa tumour in children, generally occurring before 10 years of age. The vast majority (85%) arise in the cerebellar vermis. They are hyperdense due to their high cellular content. Calcification is uncommon, occurring in up to 20% of cases. Pilocytic astrocytoma typically present as a cystic mass with an enhancing nodule. The most common location is the cerebellum, but they usually occur in other sites when associated with neurofibromatosis type 1. Haemangioblastomas are rare in children and even in the setting of von Hippel–Lindau syndrome typically manifest in early adulthood. Ependymomas are usually more heterogenous owing to calcification, cystic change, and haemorrhage. The tumour arises from ependymal cells that line the ventricular system and central canal of the spinal cord. Brainstem gliomas are hypodense on CT and may show exophytic growth into the adjacent cisternal spaces.

Answer 287

**Pilocytic astrocytoma** Pilocytic astrocytoma is the most common paediatric glioma and accounts for approximately 85% of all cerebellar astrocytoma in children. Peak age is between birth and nine years old. (Over 80% of haemangioblastomas occur in adulthood.) They are associated with neurofibromatosis type 1 (café-au-lait spots and skeletal abnormalities). The most common appearance is of a cyst with an intensely enhancing mural nodule (arachnoid cyst should be devoid of an enhancing nodule). They occasionally calcify (calcification is rare in haemangioblastomas). They run a relatively benign clinical course and almost never recur following surgical excision. There is no malignant transformation to anaplastic form.

Answer 288

**Choroid plexus papilloma** Eighty-six per cent of choroid plexus papillomas occur below the age of five years and they represent approximately 65% of choroid tumours. Large aggregation of choroid produces CSF at an abnormal rate. This CSF overproduction contributes to hydrocephalus. The most common location in children is the trigone of the lateral ventricle, the third ventricle is unusual, and the fourth ventricle and cerebellopontine angle are more common in adults. The tumour shows a smooth lobulated border and small calcifications are common. There is intense homogeneous enhancement. Approximately 5% undergo malignant transformation to choroid plexus carcinoma. Meningiomas are the most common trigonal intraventricular mass in adulthood. They rarely occur under the age of 20. Cavernous haemangiomas tend to occur in the third to sixth decades and are located in the subcortical cerebrum.

Answer 289

**Hypothalamic hamartoma** Hypothalamic hamartoma is not a true tumour by definition. It presents either with precocious puberty or with gelastic seizures (paroxysms of inappropriate emotional outbursts, usually laughing). The lesion is well defined, arising from the floor of the third ventricle/around the tuber cinereum of the thalamus and extending inferiorly into the suprasellar cistern or interpeduncular cistern. The imaging characteristics described are typical. They do not enhance.

Answer 290

**Lipoma** This is a congenital tumour that results from abnormal differentiation of the meninx primitiva – that which eventually differentiates into pia, arachnoid and internal dura mater. They account for less than 1% of brain tumours but are associated with congenital abnormalities, most commonly dysgenesis of the corpus callosum to some degree. This is particularly likely when the lipoma is located anteriorly rather than posteriorly. On CT they are well-circumscribed masses with negative Hounsfield units and occasional calcification, and they do not enhance. Characteristically, they are T1 hyperintense and slightly less hyperintense on T2. Dermoids and teratomas can show similar characteristics, with fat and calcium content. Teratomas may enhance, although dermoids do not. However, the lesion is much more likely to be a lipoma given its position (dermoids tend to be extra-axial (spinal canal); teratomas are much more commonly found around the pineal region, floor of the third ventricle, posterior fossa and spine) and given the association with corpus callosum abnormalities.

Answer 291

**Dysembryoblastic neuroepithelial tumour (DNET)** DNETs are benign tumours of neuroepithelial origin which arise from the cortical/deep grey matter. They are preferentially located supra-tentorially (temporal 62%, frontal 31%). CT demonstrates a hypoattenuating mass and there may be thinning and remodelling of the underlying inner table reflecting the slow growth of the tumour. On MRI they are hypointense on T1, hyperintense on T2 and small intra-tumoural cysts may be present to cause a characteristic ‘bubbly’ appearance. There is minimal mass effect and no associated vasogenic oedema. A third of lesions show calcification and most tumours do not enhance. They occur typically in children or young adults and commonly present with seizures. DNETs rarely undergo malignant transformation. A glioblastoma multiforme is an aggressive malignant brain tumour which presents with mass effect and surrounding vasogenic oedema and shows heterogeneous enhancement and central necrosis on imaging. PNET usually presents in the first two decades of life as a midline mass. Ependymomas generally show some surrounding oedema on imaging and can occur in the temporal lobe but usually occur in the fourth ventricle.

Answer 292

**Craniopharyngioma** Craniopharyngiomas (CPs) are the most common sellar/suprasellar region mass in children. They are benign lesions that originate from epithelial remnants (Rathke pouch) of the adenohypophysis and show a bimodal age distribution with peaks at the first and second decades (75%) and in the fifth decade (25%). They are more common in males. If the tumour presses on the pituitary gland, the patient may present with features of diabetes insipidus. Similarly, compression on the hypothalamus may lead to growth disturbance, compression on the optic chiasm may cause bitemporal hemianopia, and compression of ventricular outflow may cause raised intracranial pressure from resulting hydrocephalus. Classically, CPs appear as calcified, mixed cystic and solid tumours with enhancement of the solid component. They may be T1-bright due to proteinaceous components. Long-term survival in children is good (>90%). Germinomas are typically non-cystic and non-calcified. PNETs frequently show haemorrhage, necrosis and calcification and may resemble the appearance described for CPs. However, they are rarely found in the suprasellar region and are much more common in the posterior fossa. Chiasmatic gliomas are usually iso/hypointense on T1 and imaging usually defines optic nerve involvement.

Answer 293

**Medulloblastoma** Medulloblastomas are highly malignant lesions that account for 30–40% of all posterior fossa tumours. They typically arise from the roof of the fourth ventricle and 75% of cases occur in the first decade of life. On imaging, they are typically seen as hyperdense midline vermian masses which abut the roof of the fourth ventricle and cause hydrocephalus. There is usually mild to moderate perilesional oedema. Cystic change (high signal on T2), haemorrhage and calcification (low signal on T2) are frequently seen. They are fast-growing tumours and approximately 20% of cases demonstrate CSF dissemination at the time of diagnosis. For this reason, it is important to actively search for evidence of further cranial or spinal disease. Treatment is usually a combination of surgery and radiotherapy. Sub ependymomas typically occur in middle-aged or elderly patients. Pilocytic astrocytomas are typically cystic with an enhancing nodule. Metastases are generally multiple and occur in older patients. Ependymomas are usually hypo/isodense on CT.

Answer 294

**Subarachnoid space** Subarachnoid space is the most common, with drop metastases occurring in 40%.

Answer 295

**Focal low attenuation on CT** Dermoid and epidermoid cysts are ectoderm-lined congenital inclusion cysts. They may not present until early adulthood due to slow growth (particularly epidermoids). Epidermoids contain only squamous epithelium whereas dermoids contain hair, sebaceous and sweat glands, and squamous epithelium. Unlike teratomas, neither is a true neoplasm. Clinical presentation is often with chemical meningitis from rupture of fatty contents. Epidermoids usually have imaging characteristics like water and can be differentiated from arachnoid cysts by restricted diffusion on DWI. Attenuation varies according to the keratin ratio and therefore can be like fat but is usually homogeneous. The cyst wall is very thin and is often not visible in epidermoids, and areas of calcification can infrequently be seen. Dermoids may appear more complex but are still unilocular. The wall may be thicker and calcification is more frequent. The sebaceous lipid material in a dermoid has attenuation and signal intensity characteristics of fat on CT (low attenuation) and MR (high signal on T1). ‘White epidermoids’ with high signal on T1 may be seen rarely; they are due to haemorrhage or a high fat content. However, the latter usually produces a homogeneous fat signal as opposed to dermoids, where the appearances are more heterogeneous due to the increased complexity of contents.

Answer 296

**Craniopharyngioma** This has a bimodal age distribution (5–10 years and 50–60 years) presenting with fits and visual symptoms. High signal on T1 and T2 are due to cholesterol crystals in the cyst and solid portions enhance. Germinomas are solid tumours with homogenous enhancement. They may present with visual impairment. The lesion is hypointense on T1 and slightly hyperintense on T2. Hypothalamic hamartoma is rare and arises from the tuber cinereum. Pituitary microadenoma is low signal on T1. Arachnoid cysts show cerebrospinal fluid features on MRI and do not enhance.

Answer 297

**Diffuse brainstem glioma** Brainstem gliomas form up to 15% of all paediatric CNS tumours. There is an association with neurofibromatosis type 1. They commonly present with symptoms of diplopia, weakness, unsteady gait, headache, dysarthria, nausea and vomiting. These are poorly marginated and involve more than 50% of the brainstem at the level of maximum involvement. Minimal or no contrast enhancement is seen.

Answer 298

**Arachnoid cyst ** Arachnoid cysts are common congenital lesions in children. They are usually asymptomatic unless they cause mass effect, as in this case. They can present as a suprasellar mass with rim calcifications that can be confused for other lesions. They do not enhance and are typically high on T2 and low on T1. The presence of a fluid-fluid level is characteristic and indicates layering of fluid due to prior hemorrhage or protein content.

Answer 299

**Pituitary adenoma** Pituitary adenomas are the most common sellar masses in adults. They can be functional or non-functional and are often diagnosed incidentally. They may present with symptoms of hypersecretion, such as acromegaly, Cushing’s disease, or hyperprolactinemia. Non-functioning tumours may present with headaches and vision changes. They are usually homogeneous, solid lesions that enhance post-contrast, with no calcification. The imaging features described are typical of a pituitary adenoma. Craniopharyngiomas usually show a complex cystic/solid appearance. Germinomas typically present in younger patients and show more necrosis. Meningiomas and Rathke cleft cysts are also less likely given the findings.

Answer 300

**Astrocytoma** Astrocytoma of the spinal cord is the most common intramedullary neoplasm in children. They most commonly occur in the thoracic region (thoracic 67%, cervical 49%, conus medullaris 3%). The most common presentation is with pain and sensory deficit, but they can also present with motor and gait abnormalities. Plain radiographs may demonstrate scoliosis, bone erosion and widened interpedicular distance. On MRI, the lesion is usually seen as an eccentric, homogeneous, extensive, ill-defined cord tumour that is iso- or hypointense to the cord on T1 and hyperintense in T2. There is patchy irregular gadolinium enhancement. Tumour cysts and syrinx are also common. Patients with low-grade astrocytomas have a 95% five-year survival. It is often difficult to differentiate an astrocytoma from ependymoma of the spinal cord on imaging. In this case, the age of the patient, tumour location, tumour irregularity and eccentric position within the medullar favour astrocytoma.

Answer 301

**Astrocytoma** Astrocytomas appear as homogenously ill-defined cord tumours, with poorly defined margins and patchy irregular enhancement with gad. Masses can take the form of eccentric irregular tumour cysts, polar cysts and syrinxes.

Answer 302

**Tethered cord** Tethering of the cord results in the conus lying lower than normal and is associated with scoliosis, thickening of the ﬁlum terminale (>2 mm at the L5–S1 level on axial T1 image) and spinal lipoma. Less frequent associations are Chiari malformations, syrinx, myelomeningocele, diastematomyelia and dermal sinus. Diastematomyelia is a midline sagittal cleft in the cord, often with a bony/ﬁbrous septum. Syringomyelia is dissection of cerebrospinal fluid through the cord, producing high T2 signal within the cord. This is associated with several neurological abnormalities. Developmental scoliosis occurs in adolescent girls, is convex to the right and has no associated neurological symptoms.

Answer 303

**Central line** The tip of the central line is ideally situated superior to the level of the carina to ensure that it is not within the right atrium. Whilst placement inferior to this may be satisfactory, it can result in placement within the right atrium or coronary sinus, which are associated with an increased risk of complications. When assessing the ET tube in neonates, the tip should lie between the carina and the thoracic inlet, as more accurate placement is difﬁcult given the size of the patient. UACs are divided into high and low lines. High lines should have their tip between T8 and T10. Low lines should be sited below L3. Lines should not be sited between T10 and L3 as they can cause thrombosis of the mesenteric or renal vessels. UVCs pass superiorly into the portal vein, along the ductus venosus into the IVC.

Answer 304

**UAC courses down into pelvis before approaching thorax** The UAC passes along the umbilical artery to the internal iliac artery, from which it arises. It then passes up the common iliac artery into the aorta. The UVC passes up the umbilical vein to the left portal vein, through the ductus venosus, into the middle or left hepatic vein and into the inferior vena cava. The tips of the catheters may vary in position, but ideal placement of the UVC is around the T8–9 level, with high placement of the UAC being at the T7–9 level. The tip of the UVC may lie on either side of the UAC depending on whether it reaches the inferior vena cava or remains in the left lobe of the liver. The UAC and UVC are usually of the same diameter. Their length is determined by their course and is not a reliable predictor in identifying whether the catheter is arterial or venous.

Answer 305

**A high umbilical arterial line** The umbilical arterial line passes caudad into the internal and common iliac arteries and then courses cephalad in the aorta. The tip should be above the level of celiac axis (T6–T10), or below the renal arteries (L3–L5). An umbilical vein catheter courses directly cephalad on the right side. The tip should lie above the liver and not passed into a tributary vein.

Answer 306

**Achondroplasia** Achondroplasia is the most common form of skeletal dysplasia, caused by a mutation in the fibroblast growth factor receptor 3 (FGFR3) gene. It results in skeletal growth impairment and a short stature with disproportionately short limbs. Radiographic findings show a narrow, elongated vertebral column and long bones with irregular metaphyses. Epiphyseal dysplasia is also common. Pseudohypoparathyroidism is associated with short stature and resistance to parathyroid hormone. Radiographs show osteosclerosis and no significant epiphyseal changes. Osteogenesis imperfecta shows thin, fragile bones and may have blue sclera. Osteopetrosis shows diffuse cortical thickening with loss of medullary space. Rickets presents with wide, frayed metaphyses due to poor mineralization.

Answer 307

**Pancreatic adenocarcinoma** Pancreatic adenocarcinoma is the most common pancreatic malignancy, and its symptoms include weight loss, abdominal pain, jaundice, and changes in stool or urine. Risk factors include smoking, obesity, diabetes, and family history. The most common location for pancreatic cancer is the head of the pancreas. Imaging often shows a solid mass, and further investigations like CT scan can confirm the diagnosis.

Answer 308

**A well-circumscribed heterogeneous mass in the left kidney which enhances to a lesser degree than the kidney** Neuroblastoma (a) presents earlier and is more likely to metastasise to the liver, whilst this is the right age for Wilms tumour (e) to metastasise to the lung. Haemangioendothelioma (b) presents in early infancy with heart failure. Hepatoblastoma (c) also presents earlier and is less common than Wilms tumour, although it does metastasise to the lung.

Answer 309

**Haemolytic-uraemic syndrome** Haemolytic-uraemic syndrome is the commonest cause of acute renal failure in children needing dialysis.

Answer 310

**Sacrococcygeal teratoma** Fat, soft tissue and calcification cause the heterogeneous SI on T1. This is the most common solid tumour in the newborn, more common in females.

Answer 311

**Acute gallbladder hydrops** Kawasaki’s syndrome is an acute multisystem vasculitis with a predilection for the coronary arteries, generally affecting children under 5 years of age. As well as skin, joint and cardiovascular manifestations, patients may develop acute hydrops of the gallbladder, probably caused by transient obstruction of the cystic duct. Ultrasound scan demonstrates a markedly enlarged and tender gallbladder with a thin wall. Acute acalculous cholecystitis may be seen in children in the high dependency or intensive care setting, especially with septicaemia and trauma, but it usually results in gallbladder wall thickening and less marked gallbladder dilatation. Choledochal cyst (aneurysmal dilatation of the common bile duct) is seen as a fusiform cyst beneath the porta hepatis separate from the gallbladder. Acute calculous cholecystitis is associated with gallstones within a thickened gallbladder wall. Emphysematous cholecystitis usually occurs in adults over 50, and gas is seen as arc-like, high-level echoes outlining the gallbladder wall.

Answer 312

**Ascariasis (roundworm)** Ascariasis is the most common parasitic infection worldwide, predominantly affecting children aged 1–10 years. Worms mature in the small bowel and may be identiﬁed on plain ﬁlms as tubular soft-tissue densities or on barium studies as linear or coiled ﬁlling defects of 15–35 cm in length. Barium ingested by the worms causes opaciﬁcation of their central linear enteric canals. Patients may present with abdominal pain, appendicitis and haematemesis; occasionally, a bolus of worms may cause small bowel obstruction. Tapeworms may also appear as linear filling defects, but are usually much longer, reaching many feet in length. In addition, tapeworms have no alimentary canal and do not ingest barium. Hookworms measure 8–13 mm and cannot be visualized on barium studies. Anisakiasis of the small intestine usually appears radiologically as bowel wall thickening and luminal narrowing. Strongyloides infection may manifest as fold thickening and effacement, with a pipestem appearance of the jejunum in advanced cases.

Answer 313

**Williams’ syndrome** The features of idiopathic hypercalcaemia of infancy (Williams’ syndrome) include elfin-like facies, neonatal hypercalcaemia that can form renal stones, learning disability, physical retardation, colonic and bladder diverticula, aortic and pulmonary valve stenosis, cardiac septal defects, osteosclerosis and metastatic calcification. Marfan’s syndrome is an autosomal dominant, connective tissue disorder that, in addition to skeletal manifestations, may involve the cardiovascular system, particularly the mitral valve and ascending aorta. * Morquio’s syndrome is the commonest of the mucopolysaccharidoses, with multiple skeletal manifestations occurring within the first 18 months of life. * Wilson Mikity syndrome is like bronchopulmonary dysplasia, occurring in normal preterm infants breathing room air, but is seldom seen now due to the use of mechanical ventilation. * Maffucci’s syndrome is a dysplasia characterized by enchondromatosis and multiple soft tissue haemangiomas. Learning disability and urinary tract abnormalities are not features of any of these conditions.

Answer 314

**Cerebral median tubular cystic space with high velocity, colour Doppler flow** The unifying diagnosis is vein of Galen aneurysm. Three anatomical types are recognized, all of which are vascular malformations that dilate the vein of Galen, straight and transverse sinuses, and torcular herophili secondarily. Type 1 is an arteriovenous fistula, type 2 is an angiomatous malformation of the basal ganglia, thalami and midbrain, and type 3 has both features. It can be detected in utero or may present with a neonatal pattern of features (less than 1 month), an infantile pattern or an adult pattern (above 1 year). The in utero and neonatal manifestations are due to high-output cardiac failure and mass effect of the vein of Galen aneurysm, particularly on the aqueduct. It can undergo haemorrhage and cause infarction by a steal mechanism.

Answer 315

**Nerve deafness** Alport’s syndrome or chronic hereditary nephritis is the unifying diagnosis. It is inherited, probably in an autosomal dominant fashion. Ocular abnormalities can also occur, including congenital cataracts, nystagmus, myopia and spherophakia. Hypertension is not a feature. The renal impairment is progressive in affected males but non-progressive in females. Cerebellar and retinal haemangioblastomas occur in von Hippel–Lindau syndrome, along with renal, pancreatic and adrenal cysts.

Answer 316

**Cephal haematoma** Cephal haematoma is seen with birth trauma, particularly following poor instrumentation and skull fracture during delivery. It is seen in 1–2% of deliveries. It can grow after birth and takes weeks or months to resolve. It does not cross sutural lines because the haematoma is beneath the outer layer of periosteum. The haematoma can calcify. Caput succedaneum is localized scalp oedema that does cross sutural lines. A cephalocele is a skull defect through which meninges, brain and cerebrospinal fluid may protrude.

Answer 317

**Sacrococcygeal germ cell tumour** These are relatively rare tumours and can be benign or malignant. Calcification is seen on CT in more than half of cases, more frequently in benign lesions. Direct invasion of surrounding structures suggests malignancy. Ovarian teratoma, neuroblastoma and gastrointestinal duplication cysts are all rare and do not (usually) extend around the sacrum. Meningoceles are cystic structures.

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