TEST PAPER 3 Flashcards

Question

@#1 25. A 2-year-old girl with headache shows a large cyst in the posterior fossa with communicating hydrocephalus; bone windows reveal scalloping of the petrous pyramids. What is the likely diagnosis? A. Dandy-Walker malformation B. Dandy-Walker variant C. Astrocytoma D. Haemangioblastoma E. Chiari malformation

Answer 1

25. A. Dandy-Walker malformation The characteristic triad of the Dandy Walker malformation includes (1) complete or partial agenesis of the vermis, (2) cystic dilatation of the fourth ventricle and (3) an enlarged posterior fossa with upward displacement of the lateral sinuses, tentorium and torcula. The triad is usually associated with hydrocephalus (most common presentation 80%), but this condition should be considered a common complication and not as pan of the malformation itself. Depending on the degree of hydrocephalus, the age at diagnosis varies from the neonatal period to later childhood. The skull is enlarged, with characteristic thinning and bulging of the occiput. Pressure from the massively dilated fourth ventricle, along with cerebrospinal fluid pulsations, causes erosive scalloping of the occiput and petrous temporal bones. The cerebellar hemispheres are typically hypoplastic, and in extreme cases only a small nubbin of compressed cerebellar tissue is identified contiguous laterally with the wall of the posterior fossa cyst. Anomalies of the posterior inferior cerebellar arteries, especially absence of the inferior vermian branches and absence of the inferior vermian vein, help in the angiographic differentiation of a Dandy-Walker cyst from an arachnoid cyst, in which the vessels are displaced but present. The Dandy-Walker variant is used to describe a cystic posterior fossa malformation with varying degrees of agenesis of the vermis associated with expansion (often considerable) of the fourth ventricle, which communicates freely with the perimedullary subarachnoid space.

Answer 2

26. C. Lymphangioleiomyomatosis Lymphangioleiomyomatosis (LAM) is a rare disorder occurring almost exclusively in women of childbearing age. LAM associated with tuberous sclerosis is 5-10 times more common than sporadic LAM. Lymphatic obstruction may result in chylous pleural effusion, chylous ascites or both. Spontaneous or recurrent pneumothorax may be the presenting finding in up to 50% of patients. Characteristic HRCT features of LAM are diffuse thin-walled cysts surrounded by normal lung without regional sparing. Cysts are usually 2-5 mm but can be as large as 25-30 mm. Cysts are typically round or ovoid, but they may become polygonal with severe parenchymal involvement. Small centrilobular nodules and focal ground-glass opacities have been reported. Lymphatic obstruction may cause septal thickening.

Answer 3

27. A. MR enterography has less sensitivity and specificity compared to MR enteroclysis for established disease. The benefits of using enteric contrast material to achieve bowel distension for cross-sectional imaging are not disputed, although the optimal type of contrast material and method of administration remain somewhat controversial. Current data suggest that although bowel distension achieved with the enteric intubation technique generally is superior to that achieved with enterography, the improved distension does not necessarily translate into a clinically significant improvement in diagnostic effectiveness. A recent study confirmed the benefit of enteric intubation for bowel distension but reported equivalent diagnostic performances with the enteric and oral techniques in identifying stenoses and fistulas. However, MR enteroclysis was superior to MR enterography in demonstrating mucosal abnormalities. The importance of detecting mucosal disease in patients without bowel obstruction has diminished in the era of capsule endoscopy. Patient acceptance, which favours MR enterography over MR enteroclysis, also must be considered, because many patients need multiple examinations.

Answer 4

28. D. Rathke cleft cyst Rathke cleft cysts are benign cystic sellar lesions that are generally asymptomatic, but they may be associated with hypopituitarism, visual disturbance and headache. At MR imaging, Rathke cleft cysts have a variable Tl signal, depending on the protein concentration. Cysts with high protein content demonstrate high Tl signal and usually low intracystic water content that leads to T2 signal decrease. Thus, typical Rathke cleft cysts appear as non-enhancing well demarcated intrasellar rounded lesions located exactly at the midline between the anterior and posterior pituitary lobes. The cysts have a homogeneously hyperintense Tl signal and, often, a hypointense T2 signal. Axial images are crucial for identifying the specific location and characteristic kidney shape of a Rathke cleft cyst. The presence of fluid-fluid level or haemorrhagic debris in an intrasellar lesion suggests a pituitary adenoma, because a Rathke deft cyst almost never bleeds. Craniopharyngioma typically appears as intrasellar or suprasellar heterogeneously enhancing lesions with a tripartite structure of solid, calcified and cystic components. They are difficult to distinguish from pituitary adenoma, although the fluid fluid level is more likely to suggest a pituitary adenoma.

Answer 5

29. E. Oncocytoma Oncocytomas are tubular adenomas with a specific histological appearance. They were previously considered benign but have now been recognised to metastasise. They vary from 1 to 20 cm in diameter and tend to be large. They are usually solitary and unilateral. US shows a solid mass with internal echoes, which occasionally have a stellate hypoechoic centre. CECT demonstrates a well-defined solid mass, with a low-attenuation central scar, when large. Large lesions can extend into and engulf perinephric fat. RCC and oncocytoma look similar on MRI.

Answer 6

30. B. Bucket-handle tear of meniscus Bucket-handle tears of the meniscus involve displacement of the free edge of the meniscus into the intercondylar notch. The free edge can be seen adjacent to the PCL on sagittal images giving a double PCL sign. On coronal imaging, the meniscal fragment is displaced medially. A radial mcniscal tear manifests as a linear collection of high signal in the meniscus that extends to the superior or inferior articular surfaces. Rupture of the ACL or PCL results in the ligament losing die normal position and morphology but not a double PCL sign. When assessing the PCL, be aware that the ligaments of Humphrey and Wrisberg can give the impression of a tear to the inexperienced eye. These ligaments are extensions of the meniscofemoral ligament; the ligament of Humphrey passes anterior to the PCL and the ligament of Wrisberg posteriorly.

Answer 7

31. A. Langerhans cell histiocytosis Pulmonary LCH is a smoking-related lung disease. Peribronchiolar nodules are found; they may subsequently cavitate and form thick- and thin-walled cysts. Frequently, both nodules and cysts are seen. Cysts may be round but are often irregular, clover-leaf or bizarre shapes. Irregular cysts, cysts with nodules and upper zone predominance with sparing of the costophrenic angles are features that distinguish LCH from lymphangioleiomyomatosis. Centrilobular emphysema represents the permanent destruction of bronchiolar walls with resultant enlargement of the airspaces distal to the terminal bronchiole. The distinguishing features of centrilobular emphysema include the lack of a perceptible cyst wall and the central location of the vascular structures (central dot sign).

Answer 8

32. A. ‘Jejunisation’ of the ileum In both primary and secondary amyloidosis, the most commonly involved organ system is the gastrointestinal system, with the colon being the most frequently involved organ. Oesophageal and gastric involvement usually manifests as dysmotility, wall thickening and gastroesophageal reflux disease. This results from amyloid infiltration of the muscularis and/or destruction of the Auerbach plexus. When the small intestine is involved, the most common finding is diffuse or nodular wall thickening. Abdominal pain, malabsorption and haemorrhage are rare complications. Colonic biopsy specimens are positive in 80% of patients with systemic amyloidosis. Contrary to the high pathologic specificity, radiologic findings are rare and non-specific. The most common finding is colonic dilatation owing to adynamic ileus and more rarely bowel wall thickening. Even more rarely, intramural bowel haemorrhage or perforation can occur. Splenomegaly is the only finding associated with splenic involvement This causes increased fragility, and spontaneous rupture can ensue with life threatening consequences. The liver is also commonly involved, but radiologic signs are also non-specific. Diffuse infiltration is the rule, which causes decreased attenuation at CT and hepatomegaly. Macroglossia can also result from amyloid infiltration of the intrinsic muscles. Jejunisation of the ileum can be seen with coeliac disease.

Answer 9

33. B. Glomus tumour A glomus tumour is a hamartoma arising from the glomus body within the dermis of the finger. The subungual position is characteristic of the lesion, which results in extrinsic erosion of the adjacent terminal phalanx. The tumour can also occur entirely within bone, although this is less common. It exhibits intense high T2 signal with avid contrast enhancement as it is a highly vascular lesion. Epidermoid inclusion cysts, otherwise known as implantation dermoid cysts, are associated with a history of penetrating trauma. A giant cell tumour of the tendon sheath lies in close relation to the tendon and does not exhibit such intense T2 signal. The description is not compatible with a soft-tissue osteosarcoma.

Answer 10

34. D. T3b T-stage T1a: Limited to kidney, <4 cm T1b: Limited to kidney, >4 cm but <7 cm T2a: Limited to kidney, >7 cm but not more than 10 cm T2b: Limited to kidney, >10 cm T3a: Spread to perinephric fat T3b: Spread to renal vein or IVC below diaphragm T3c: Spread to supra diaphragmatic I VC or invades the wall of the IVC T4: Involves ipsilateral adrenal gland or invades beyond Gerota’s fascia N-stage N0: No nodal involvement N1: Metastasis to one regional lymph node(s) M-stage M0: No distant metastases M1: Distant metastases

Answer 11

35. C. Ruptured dermoid cyst Dermoid cysts are congenital ectodermal inclusion cysts. They tend to occur in the midline sellar, parasellar, or frontonasal regions or in the posterior fossa, where they occur either as vermian lesions or within the fourth ventricle. Imaging findings vary, depending on whether the cyst has ruptured. Unruptured cysts have the same imaging characteristics as fat because they contain liquid cholesterol. All are hyperintense on T1-weighted images and do not enhance. The masses have heterogeneous signal intensity on T2-weighted images and vary from hypo- to hyperintense. The best diagnostic clue of a ruptured dermoid cyst is fatlike droplets in the subarachnoid cisterns, sulci and ventricles. Extensive pial enhancement can be seen from chemical meningitis caused by ruptured cysts. Dermoid cysts may be confused with an epidermoid cyst, craniopharyngioma, teratoma or lipoma. Epidermoid cysts typically resemble CSF (not fat), lack dermal appendages, and are usually located off-midline. Like dermoid cysts, craniopharyngiomas are suprasellar, with a midline location, and demonstrate nodular calcification. However, most craniopharyngiomas are strikingly hyperintense on T2-weighted images and enhance strongly. Teratomas may also have a similar location but usually occur in the pineal region. Lipomas demonstrate homogeneous fat attenuation and/or signal intensity and show a chemical shift artefact, which typically does not occur with dermoid cysts.

Answer 12

36. E. Total anomalous pulmonary venous return (TAPVR) TAPVR occurs when the pulmonary veins fail to drain into the left atrium and instead form an aberrant connection with some other cardiovascular structure. On chest radiographs, this cardiovascular anomaly resembles a snowman (figure of eight appearance). In infants affected by TAPVR, cyanosis and congestive heart failure typically develop in the early neonatal period. TA, TGA typically does not present with heart failure. Vein of Galen aneurysm presents with features of heart failure on a chest X-ray but without any specific pattern.

Answer 13

37. A. Thymoma Thymomas are classified as encapsulated, infiltrative and metastasising, with pulmonary and pleural deposits and thymic carcinoma. Half the thymomas are asymptomatic and 30% are associated with myasthenia gravis. At CT a benign thymoma appears round, oval or lobulated. Focal calcification is seen in 25%, which may be dense, irregular or coarse. Benign thymomas show mild homogenous enhancement; cystic changes are also described. Invasive thymoma are heterogeneous in appearance; pericardial and pleural nodules suggest malignancy. Egg-shell calcification is described in invasive thymoma. Absent fat planes between thymoma and mediastinum does not necessarily reflect invasion.

Answer 14

38. E. Focal appendiceal wall enhancement defect Defect in enhancing appendiceal wall has the highest specificity (100%) and sensitivity (64.3%) for indicating perforated appendicitis.

Answer 15

39. C. Diffuse axonal injury Diffuse axonal injury (DAI) is a type of brain damage that is secondary' to rotational acceleration/deceleration. MR can identify DAI lesions, whereas CT scan often fails to do so. T2-weighted images show high signal with blooming artefact. SWI (or GRE) sequences, exquisitely sensitive to blood products, may demonstrate small regions of susceptibility artefact at the grey-white matter junction, in the corpus callosum or the brain stem. DAI is classified into three stages: the involvement of the grey-white matter junction indicates Stage I; corpus callosum involvement, particularly the splenium, indicates Stage II; and brainstem involvement indicates Stage III. Clinical studies demonstrate that the prognosis becomes poorer as deeper structures are involved.

Answer 16

40. B. TCC of the renal pelvis Hereditary non-polyposis colon cancer syndrome (HNPCC) is an autosomal dominant condition that is associated with a high incidence of tumours of the renal pelvis, colorectal cancer, and tumours of the ovaries and small bowel. Squamous cell carcinoma of the renal pelvis is rare and is a highly aggressive tumour with a poor prognosis. Chronic infection and calculi play an important aetiological role in this malignancy, and stones are present in 57% of patients. Renal lymphomas typically demonstrate sheet-like diffuse infiltration of the perirenal tissues or multiple low-attenuation focal lesions. Renal metastases are usually small (<3 cm), multiple and confined to the cortex. They are associated with metastases elsewhere, are of low attenuation, do not calcify, and do not invade the renal vein; they are also more infiltrative than exophytic compared to renal cell carcinoma.

Answer 17

41. E. Erlenmeyer flask deformity Erlenmeyer flask deformity is associated with thalassaemia. Non specific findings of haemophilic arthropathy include joint effusion and periarticular osteopaenia from hyperaemia. Classical features include epiphyseal enlargement with associated gracile diaphysis (differentials are juvenile rheumatoid arthritis). Secondary degenerative disease with symmetrical loss of joint cartilage involving all compartments equally with periarticular erosions, subchondral cysts, osteophytes and sclerosis is seen in end-stage arthropathy. Specific findings at the knee include widened intercondylar notch, squared margins of the patella, expanded femoral condyles and flattened surface of femoral condyles. Specific findings at the elbow include enlargement of the radial head and widening of the trochlear notch.

Answer 18

42. D. Scrotal wall oedema Differential diagnosis of acute scrotum includes testicular torsion (the most important differential) along with torsion of the testicular appendix, epididymitis and epididymo-orchitis. US (including the use of Doppler imaging) plays a vital role in distinguishing between these diagnoses. All of the above features can be seen in testicular torsion, along with such findings as epididymal enlargement and hydrocoele. However, scrotal wall oedema is the only one of these findings that is more commonly seen with alternative causes of acute scrotum than it is with acute testicular torsion. Decreased or absent blood flow is considered the most important finding, although torsion is not excluded if there is normal or increased blood flow, which may occur after spontaneous detorsion.

Answer 19

43. E. DWI shows low signal in the affected area. In the immunocompetent adult patient, the pattern is quite typical and manifests as a bilateral asymmetrical involvement of the limbic system, medial temporal lobes, insular cortices and inferolateral frontal lobes. **The basal ganglia are typically spared.** Extralimbic involvement is more prevalent in children than in adults, seen most commonly in the parietal lobe, with sparing of the basal ganglia. Eventually, it results in marked cystic encephalomalacia and volume loss in affected areas. In immunocompromised patients, involvement can be more diffuse and is more likely to involve the brainstem. Early diagnosis is difficult and a ‘normal' CT is often seen. Affected areas appear low on T1-weighted MRI due to oedema. High T1 signal suggests areas of haemorrhage. Post-contrast enhancement is usually late and can be gyral, leptomeningeal, ring or diffuse enhancement. Affected white matter and cortex appears high signal on T2-weighted and FLAIR images. Areas of haemorrhage show low T2 signal and blooming artefact. DWI is more sensitive than T2-weighted images. Cytotoxic oedema is seen as high signal on DWI with corresponding low signal on ADC map. Vasogenic oedema is bright on both (T2 shine-through).

Answer 20

44. D. Nerve sheath tumour Anatomical and radiological division of the mediastinum into anterior, middle and posterior varies. Anatomically, structures in the pericardial space including great vessels constitute the middle mediastinum; structures anterior to the pericardial sac constitute the anterior mediastinum, and structures behind the sac constitute the posterior mediastinum. The Felson method of radiological division is based on lateral chest radiography. A line extending from the diaphragm to the thoracic inlet along the back of the heart and anterior to the trachea separates the anterior and middle mediastinum, whereas a line that connects points 1 cm behind the anterior margins of the vertebral bodies separates the middle and posterior mediastinal compartments. The hilum overlay sign is present when the normal hilar structures project through a mass, meaning that the mass is either anterior or posterior to the hilum. Loss of anterior junction line and cardiac contours would suggest anterior location; preservation of these lines and the loss or widening of the posterior junction lines, paraspinal lines, would suggest posterior location. Lymphoma, teratoma and goitre are anterior mediastinal masses. Nerve sheath tumours arc the only true posterior mediastinal structures amongst the examples.

Answer 21

45. C. It is usually associated with change in bowel habits The condition most commonly manifests in the fourth to fifth decades of life, predominantly in men. With diagnosis based on clinical manifestations alone, acute epiploic appendagitis is misdiagnosed in the majority of patients. Clinically, acute epiploic appendagitis manifests with acute onset of pain, most often in the left lower quadrant, and this symptom often leads to its being mistaken for acute diverticulitis. Unlike acute epiploic appendagitis, acute diverticulitis is more likely to manifest with evenly distributed lower abdominal pain and to be associated with nausea, fever and leucocytosis. Although most patients with acute epiploic appendagitis do not report any change in their bowel habits, a minority experience constipation or diarrhoea. Most patients with acute epiploic appendagitis have a normal white blood cell count and body temperature. CT images from less than 8% of patients evaluated for exclusion of sigmoid diverticulitis or appendicitis show features of primary acute epiploic appendagitis. When acute epiploic appendagitis involves the cecum or ascending colon, it may be mistaken clinically for acute appendicitis. The most common sites of acute epiploic appendagitis, in order of decreasing frequency, are areas adjacent to the sigmoid colon, the descending colon and the right hemicolon.

Answer 22

46. B. Urology referral and check of serum parathyroid hormone levels. The most common clinical manifestations of hyperparathyroidism include renal stones and nephrocalcinosis, high blood pressure, acute arthropathy (CPPD), osteoporosis, peptic ulcer, acute pancreatitis, proximal muscle weakness, depression and confusional state (often described in medical text books as ‘stones, groans and moans’). It is diagnosed by raised serum parathormone levels. Serum TSH levels are related to hyper- and hypothyroidism. Calcitonin is typically raised in medullary carcinoma of the thyroid. Serum alkaline phosphatase is a nonspecific enzyme marker, which is raised, in several inflammatory, metabolic and malignant conditions. LDH is also a non-specific enzyme marker, raised in heart disease and myositis.

Answer 23

47. E. Monostotic fibrous dysplasia Fibrous dysplasia is an uncommon, benign disorder characterised by a tumour-like proliferation of fibro-osseous tissue. It may either present as monostotic (affecting one bone) or polyostotic (affecting many bones). Fibrous dysplasia is usually found in the proximal femur. tibia, humerus, ribs and craniofacial bones in decreasing order of incidence. Polyostotic cases can affect multiple adjacent bones or multiple extremities. Men and women are equally affected by the disorder. Fibrous dysplasia is usually asymptomatic, although pain and swelling may accompany the lesion. Radiographically, fibrous dysplasia appears as a well-circumscribed lesion in a long bone with a ground-glass or hazy appearance of the matrix. There is a narrow zone of transition and no periosteal reaction or soft-tissue mass. The lesions are normally located in the metaphysis or diaphysis. There is sometimes focal thinning of the overlying cortex, called ‘scalloping from within'. The radiological appearance can also be cystic, pagetoid, or dense and sclerotic. Repeated fractures through lesions in the proximal femur can result in the formation of a so-called shepherd’s crook deformity. The Tc-99m bone scan uptake may be normal or increased. Bone scans are not helpful in diagnosing these lesions but can be useful in identifying asymptomatic lesions. MR! or CT scans can be helpful in delineating the extent of the lesion and identifying possible pathological fractures. Sarcomatous change within the lesion can be identified by MRI or CT.

Answer 24

48. B. Blount disease All of the answers can lead to leg bowing in paediatric groups. However, the description is that of Blount disease, otherwise known as tibia vara. This is a common condition that is unilateral or asymmetrical and is thought to arise as a result of abnormal stress (such as obesity and walking at an early age) on the posteromedial proximal tibial physis. There are three types: infantile (the most common), juvenile and adolescent. Anteroposterior radiography of both legs is necessary. Neurofibromatosis may cause anterolateral tibial bowing, possibly with fibular hypoplasia, and one or both bones may fracture to give a pseudarthrosis. Developmental or physiological bowing is where there is exaggeration of varus angulation between the ages of 12 and 24 months, which again may be caused by obesity or early walking. There is metaphyseal beaking but no fragmentation, and it is usually symmetrical and bilateral. Congenital bowing is usually convex posteromedially (unlike neurofibromatosis). Marked dorsiflexion of the foot is evident at birth, as this condition is thought to arise from an abnormal intrauterine position. Radiography shows thickening of the cortex of the concavity of the curvature. Osteogenesis imperfecta causes bowing of multiple long bones as a result of osteoporotic softening and fractures; hence bone density reduction and bilateral bowing would be more likely.

Answer 25

49. D. Aberrant left pulmonary artery Vascular anomalies of the aortic arch and the pulmonary artery can cause vascular impression on the barium-filled oesophagus. The most common is a right-sided aortic arch, which results in an indentation on the right and absence of normal aortic impression on the left. Bilateral indentation is caused by a double aortic arch; the right arch is normally higher and larger than the left. Aberrant right subclavian artery from a normal arch or an aberrant left subclavian artery from a right-sided arch traverses behind the oesophagus as it crosses the mediastinum and results in a posterior impression on the oesophagus seen on a lateral view. An aberrant left pulmonary artery traverses between the trachea and oesophagus above the carina, resulting in a posterior indentation on the trachea and an anterior indentation on the oesophagus on lateral view. Coarctation of the aorta results in a reverse-3 impression on the left of the oesophagus on an AP image. Type-3 anomalous pulmonary veins traverse the diaphragm with the oesophagus and drain into a systemic vein, causing an impression on the anterior wall of the oesophagus, low down close to the diaphragm.

Answer 26

50. C. Contracted gallbladder Features of acute cholecystitis include thickened GB wall >4-5 mm, echogenic bile/sludge, gallbladder distention, pericholecystic fluid in the absence of ascites and subserosal oedema. Contracted GB is generally a feature of chronic cholecystitis.

Answer 27

51. E. Involved seminal vesicles show a high signal on T2W images. MR tumour staging criteria follow the TNM system. A papillary tumour is best seen on T1-weighted images, where it is seen as higher signal than the urine. It appears similar in signal intensity on T2-weighted sequences. Tumour demonstration (especially a small one) is facilitated by use of contrast. To evaluate infiltration, T2-weighted or post-contrast T1-weighted sequences are required. Use of surface coils (endorectal coils) improves visualisation of layers of the bladder wall, improving staging of T2-T3b tumours. Visualisation of low intensity bladder wall on T2-weighted sequence between the tumour and perivesical fat helps in differentiating a T2b tumour from a T3 tumour. Disruption of low-signal bladder wall, perivesical fat stranding and irregularity of the outer bladder wall suggests T3b disease. Dynamic contrast induced MRI improves bladder cancer staging accuracy by helping differentiation of tumour (enhances earlier) from inflammatory post-biopsy changes in the bladder wall or perivesical fat (slower rate of enhancement). It is also useful in staging nodes, because abnormal nodes (normal or abnormal by size) enhance earlier than non-metastatic lymph nodes. Involvement of the seminal vesicle is evident as an increase in size of the vesicle, reduced T2 signal, and obliteration of the angle between the seminal vesicle and posterior bladder wall. In contrast, invasion of the prostate and rectum is seen as direct tumour extension and an increase in signal intensity on T2-weighted images. T staging of bladder tumours Ta: Non-invasive papillary tumour Tis: In situ (non-invasive flat) T1: Through lamina propria into subepithelial connective tissues T2a: Only invades the inner half of the muscle T2b: Invades into the outer half of the muscle T3a: Microscopic extravesical invasion T3b: Macroscopic extravesical invasion T4: Direct invasion into adjacent structures (prostate, uterus, vaginal vault) T4b: Direct involvement of pelvic side wall and/or abdominal wall

Answer 28

52. D. Osteosclerosis is more common in the primary form. Osteosclerosis, as seen in the rugger jersey spine, is associated with the secondary form of hyperparathyroidism from chronic renal failure. The rest of the statements are true. In summary, the radiological findings, which are more associated with the primary form, include Brown tumours, subperiosteal bone resorption, soft-tissue calcification (although less common than in the secondary forms), and chondrocalcinosis. The findings for secondary hyperparathyroidism include subperiosteal bone resorption, osteosclerosis and soft-tissue calcification.

Answer 29

53. D. Epidermoid Causes of white matter hyperintensities are protean; however certain categories are recognised. These include the following: Hypoxic/ischaemic aetiology secondary to hereditary conditions (Fabry’s disease, PKU, MELAS, amyloid deposition, CADASII., moyamoya, Rendu-Weber-Osler syndrome, etc.) or acquired conditions (hypertension, hypotension, atherosclerosis, NPH, embolic events, Wallerian degeneration, etc.). Inflammatory conditions like MS and its variants, ADEM, SSPE, vasculitis (Behcet’s disease, GCA, PAN, etc.), sarcoid, bacterial, protozoal, viral (HSV, HIV, PML), spirochetal (Lyme disease) and fungal. Toxic or metabolic causes like CPM, CO intoxication, methotrexate treatment, Marchiafava- Bignami syndrome and B12 deficiency. Other conditions include radiation, contusion, hystiocytosis and Erdheim-Chester disease. Epidermoid cysts are extraparenchymal, mimic CSF, do not enhance and show restricted diffusion.

Answer 30

54. C. Occipital bone Thalassaemia major, as with other causes of chronic anaemia, causes widening of the diploic space in the skull as a result of marrow hyperplasia, with thinning of the outer table and thickening of the inner table. A 'hair on end' appearance is seen, with periosteal bony spicules extending beyond the outer table. The occipital bone normally has a lower bone marrow content and is therefore not affected to the same extent by these changes. Occasionally, solitary or multiple lytic lesions may be seen in the skull. Paranasal sinuses and mastoids are often absent or underpneumatised owing to frontal, temporal and facial bone marrow hyperplasia. The ethmoid sinuses are the exception because there is minimal marrow content in the surrounding bones.

Answer 31

55. B. Cytomegalovirus pneumonitis Early complications include interstitial pneumonitis (infective and non-infective types), infection, oedema, haemorrhage, thromboembolism and calcification. COP is a rare complication that may occur early or late. Cytomegalovirus (CMV) is the most important viral pathogen that causes pneumonia in transplant recipients. RSV, HHV6, pneumocystis jiroveci and adenovirus are less common. Idiopathic interstitial pneumonia has various causes including acute graft-versus- host disease. Unfortunately, CT appearances of both infectious and non-infectious interstitial pneumonitis are non-specific. Notable features include increased interstitial markings, multilobar infiltrates, areas of ground-glass opacity and nodules. Biopsy is frequently undertaken to identify the cause.

Answer 32

56. D. Contrast-enhanced CT Contrast-enhanced CT is the imaging modality of choice for the diagnosis and staging of acute pancreatitis. The pancreas enhances uniformly in mild acute pancreatitis and may be normal or enlarged with a variable amount of increased attenuation in the adjacent fat, termed ‘stranding’. Local oedema is a common finding and may extend along the mesentery, mesocolon and hepatoduodenal ligament and into the peritoneal spaces. Extension of oedematous fluid into the anterior perirenal space may create a mass effect and a halo sign with sparing of the perinephric fat. Abnormal ultrasound findings are seen in 33%-90% of patients with acute pancreatitis. Interstitial oedema in acute pancreatitis is depicted on ultrasound as an enlarged hypoechoic gland. Although ultrasound may be used to identify peripancreatic acute fluid collections, it is not useful for the detection of necrosis. Thus its main role in the imaging of acute pancreatitis is limited to the detection of cholelithiasis and choledocholithiasis and identification of fluid collections in the peritoneum, retroperitoneum and pleural spaces.

Answer 33

57. B. The central and transition zones show similar low signal. On T1-weighted images, the prostate shows homogenous intermediate signal intensity, and the zones cannot be differentiated. The zonal anatomy is best seen on T2- weighted images with the peripheral zone showing a high signal compared to both the central and the transitional zones. The central and transitional zones have similar low signal. At a young age, the transitional zone is homogenous low signal; it gets increasingly heterogeneous with age and BPH changes. On T2-weighted images, the shape of the peripheral zone changes from the base to apex. At the base, the peripheral zone surrounds the posterolateral aspect of the central zone, while at the apex it concentrically surrounds the central zone. The prostatic capsule separates the peripheral zone from the periprostatic tissue, whereas the surgical pseudocapsule separates the peripheral zone from the transitional zone in the older population. MRI is recognised to be more accurate than US and CT in assessment of prostate volume.

Answer 34

58. C. Developmental dysplasia of the hip The patient has developmental dysplasia of the hip, which has resulted in subluxation of the femoral head. The centre edge angle is useful in older toddlers up to adulthood to estimate the degree of acetabular over or under coverage. It is the angle between a vertical line drawn up from the centre of the femoral head and the outer edge of the acetabular roof. In an adult, an angle less than 20 degrees indicates underlying dysplasia. Perthes disease is a paediatric condition characterised by avascular necrosis of the femoral head. Ollier’s disease is the condition of multiple enchondromas (enchondromatosis). Isolated traumatic subluxation requires significant trauma in the absence of an underlying dysplasia.

Answer 35

59. B. Diffusion-weighted MR imaging Epidermoid cysts are characteristically well demarcated and have a homogeneous low density, similar to CSF on CT scan, showing no contrast enhancement. On MRI, epidermoid cysts are hypointense on T1-weighted images and hyperintense on T2-weighted images. On FLAIR, epidermoid cysts become hyperintense or appear more heterogeneous compared to an arachnoid cyst. There are occasions when an epidermoid may appear as a low-intensity lesion on FLAIR. However, on diffusion-weighted imaging, epidermoid cysts show restriction and remain bright (due to a combination of true restricted diffusion and T2 shine-through). The latter helps with definitive differentiation of an epidermoid cyst from an arachnoid cyst.

Answer 36

60. B. Haemorrhagic ovarian cyst All of the above may present as a right hemipelvic mass. Haemorrhage into an ovarian follicular cyst is the most common of these, and it usually resolves after one or two menstrual cycles. Several patterns of ultrasound findings have been described, including an echogenic mass, a ground glass pattern (diffuse low-level echoes), a whirled pattern of mixed echogenicity and a ‘fishnet weave' pattern (fine septations or reticular echoes). Appendix abscess would be thick-walled. Ovarian dermoid may present as an echogenic mass, although acoustic shadowing would be more typical owing to internal calcifications and would not resolve in this fashion. Ectopic pregnancy may present as an echogenic ‘tubal mass’, although elevated β-hCG would be a feature. Ovarian torsion may appear as an enlarged echogenic ovary (owing to oedema) and, like haemorrhagic cyst, often lacks internal colour Doppler flow, although it is less common than haemorrhagic cyst. It would also necessitate urgent surgery rather than follow up imaging.

Answer 37

61. B. Pulmonary contusion Lung contusion is the most common type of lung injury in blunt chest trauma. It occurs at the time of injury, but it may be undetectable on chest radiography for the first 6 hours after trauma; however, CT may show it immediately. The pooling of haemorrhage and oedema will blossom at 24 hours, rendering the contusion more evident. The appearance of consolidation on CXR after the first 24 hours should raise the suspicion of other pathological conditions such as aspiration, pneumonia and fat embolism. Clearance of an uncomplicated contusion begins at 24 48 hours with complete resolution after 3-14 days. Lack of resolution within the expected time frame should raise the suspicion of complications such as pneumonia, abscess or ARDS. Lung laceration results in ground-glass change or consolidation with pneumatocoele, haematocele or pneumothorax. Rib fractures may be associated with peripheral lacerations.

Answer 38

62. E. Low luminal signal intensity on Tl- and T2-weighted images MR imaging features of a normal appendix include a diameter less than 6 mm, an appendiceal wall thickness less than 2 mm, low luminal signal intensity on Tl - and T2-weighted images and no periappendiceal fat stranding or fluid. MRI features of appendicitis include an appendiceal diameter greater than 7 mm, an appendiceal wall thickness greater than 2 mm, high-signal- intensity luminal contents on T2-weighted images due to fluid or oedema and hyperintense periappendiceal fat stranding and fluid. An appendix with high-signal-intensity luminal contents on T2-weighted images and a diameter between 6 and 7 mm without associated wall thickening or periappendiceal fat stranding or fluid is considered indeterminate for appendicitis and warrants close clinical follow-up. MRI has been described as an effective modality for the diagnosis of appendicitis during pregnancy, with 100% sensitivity and 94% specificity reported.

Answer 39

63. D. T3b T staging of prostate cancer T1: Not palpable via DRE or seen using TRUS. T1a: Cancer found incidentally during TURP, less than 5% of the gland. T1b: Cancer found incidentally but over 5% of the gland is involved. T1c: Found by needle biopsy for a raised PSA. T2: Palpable on DRE, but confined to the prostate. T2a: Less than half of one lobe. T2b: More than half of one lobe. T2c: Cancer in both lobes of the prostate. T3: Spread outside the prostate. T3a: Extracapsular extension (one or both sides). T3b: Tumour invades the seminal vesicles. T4: Spread into the adjacent tissues (other than seminal vesicles).

Answer 40

64. D. Placement of a pelvic wrap device All of these steps may be required, but the most important is to place a pelvic wrap device. The purpose of this device is to stabilise the pelvis. If the patient is hypotensive as a result of venous bleeding, a pelvic wrap should stabilise the pelvis sufficiently to cause significant reduction or cessation in the venous haemorrhage and thus avoid unnecessary endovascular intervention. If this fails to achieve sufficiently prompt haemodynamic stability, there is a significant chance that there is arterial haemorrhage; hence endovascular intervention is likely to be necessary. Many centres use angiographic sequences as part of the trauma CT scan to identify such a bleeding point as part of planning stage of endovascular management. CT would be the next step once die pelvic binder is in situ.

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65. C. Smaller nodule Pilocytic astrocytoma is the most common paediatric cerebellar neoplasm and the most common paediatric glioma. They can be differentiated from haemangioblastoma on the following basis: astrocytomas are more likely to be larger than 5 cm, contain calcification, have a larger mural nodule, are thick walled lesions, do not show angiographic contrast blush to the mural nodule and are not associated with erythrocythaemia.

Answer 42

66. B. It most commonly occurs on the left. Ovarian torsion is most common in prepubertal girls and may be caused by ovarian enlargement (for example owing to neoplastic causes, of which benign cystic teratoma is the most common) or abnormally increased adnexal mobility. It is more common on the right than the left, which is postulated to occur because of a protective effect of the sigmoid colon on the left side. On ultrasound, the most reliable positive finding is asymmetry between the volumes of the right and left ovaries. Arterial Doppler waveform is usually but not always absent, as there is blood supply from both the ovarian and uterine arteries. A whirlpool sign may be seen because of twisting of the ovarian pedicle. Treatment is with emergency surgery; hence immediate referral to gynaecology is required.

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67. A. Pulmonary artery aneurysm One of the most common findings of Behcet's disease at chest radiography is a lung mass attributed to a pulmonary artery aneurysm. The pulmonary artery is the second most common site of arterial involvement, with the aorta being the most common, and aneurysms are more common than thromboembolism. Behcet’s disease is the most common cause of pulmonary artery aneurysms. Hughes-Stovin syndrome is a rare disorder of unknown aetiology that is characterised by the combination of multiple pulmonary artery aneurysms with mural thrombi and deep venous thrombosis. Another well-known finding is the mediastinal widening caused by thrombosis of the SVC and accompanying mediastinal oedema. Thrombosis of the brachiocephalic, subclavian and axillary veins may also accompany SVC occlusion. Arterial involvement may occur in the ascending thoracic aorta and the aortic arch, as well as in the coronary artery and subclavian artery in the thorax. Aneurysm formation occurs more frequently than arterial occlusion.

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68. B. Stomal stenosis is a rare complication. The most common complication after gastric banding is stomal stenosis. This complication occurs when the band is too tight, causing excessive luminal narrowing and obstruction. Affected individuals usually present with nausea and vomiting, regurgitation, dysphagia or upper abdominal pain. When stomal stenosis is found on barium studies in patients with obstructive symptoms, the band should be deflated to increase luminal calibre and relieve the patient's symptoms. Acute pouch dilation usually results from marked stomal narrowing secondary to overfilling of the band or from distal band slippage and obstruction. In this setting, the band should be deflated to prevent further complications, including irreversible pouch dilation and progressive band slippage. Distal band slippage is thought to result from recurrent vomiting, overinflation of the band or faulty surgical technique. Malpositioning of the band is an unusual complication that occurs at the time of surgical placement, most often when this procedure is performed by an inexperienced surgeon. Band erosion into the gastric lumen is a rare but late complication of laparoscopic adjustable gastric banding and results from high pressures generated by the inflated band, with pressure necrosis of the adjacent gastric wall and subsequent erosion of the band into the lumen.

Answer 45

69. E. Complete tear Grade III at the level of the urogenital diaphragm Urethral injuries associated with a pelvic fracture were classified into five types by Goldman and Sandler and into three types by Colapinto and McCallum, with Types IV and V being exclusive to Goldman and Sandler: Type I, posterior urethra stretched but intact (no extravasation of contrast); Type II, urethra disrupted at the membrano-prostatic junction above the urogenital diaphragm (contrast in pelvis); Type III, membranous urethra disrupted, with extension to the proximal bulbous urethra and/or disruption of the urogenital diaphragm (most common - contrast in pelvis and perineum); Type IV, bladder neck injury with extension into the urethra; and Type V, partial or complete pure anterior urethral injury. Grades II and III are subdivided into complete and incomplete tear depending on the absence or presence of bladder filling.

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70. A. Large osteophytes Milwaukee shoulder consists of the association of complete tear of the rotator cuff, osteoarthritic changes, non-inflammatory joint effusion containing calcium hydroxyapatite and calcium pyrophosphate dihydrate crystals, hyperplasia of the synovium, destruction of cartilage and subchondral bone, and multiple osteochondral loose bodies. This entity most frequently affects older women and manifests clinically as a rapidly progressive and destructive arthritis of the shoulder. It manifests as joint space narrowing, subchondral sclerosis with cyst formation, destruction of subchondral bone, soft-tissue swelling, capsular calcifications and intra-articular loose bodies. MR imaging demonstrates a large effusion, a complete rotator cuff tear, narrowing of the glenohumeral joint, thinning of cartilage and destruction of subchondral bone.

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71. D. Late subacute

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72. C. Wolman disease Wolman disease is an uncommon autosomal recessive disorder characterised by accumulation of fat within such tissues as the liver, spleen, lymph nodes and adrenal glands. Accordingly, these tissues will increase in size. The adrenal findings are diagnostic of the condition, with glands that are of normal shape but increased size, with diffuse punctate calcification throughout both glands. It is usually fatal by the age of 6 months. Neuroblastomas may be seen in both adrenal glands simultaneously and are often calcified, although they will usually be large irregular masses. Non-traumatic haemorrhage of both adrenals may be seen, often caused by perinatal stressors, although this also takes the form of a mass and calcification is usually peripheral (initially) or dense (chronic stage). Adrenal glands may be thickened in adrenocortical hyperplasia but calcification is not a typical feature. Adrenocortical carcinoma is typically unilateral and is not usually seen until after the age of 6 months.

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73. D. Stage IV disease refers to bilateral renal involvement at diagnosis. Wilms tumour has multiple associations. One-third of patients with sporadic aniridia develop Wilms tumour; it also occurs in up to 20% of Beckwith-Wiedemann syndrome sufferers (otherwise known as EMG syndrome - exomphalos, macroglossia, gigantism with hepatomegaly also a feature). Other associations include hemihypertrophy and a variety of genitourinary disorders including Drash syndrome, renal anomalies (including horseshoe kidney) and genital anomalies. Nephroblastomatosis is a recognised precursor and is seen in 99% of cases of bilateral Wilms tumour. Presentation of Wilms tumour is most commonly as an asymptomatic palpable abdominal mass, although other presentations include hypertension, pain and fever. Stage IV disease refers to the presence of haematogenous or extra-abdominopelvic lymph nodes.

Answer 50

74. C. Pleural fibroma Chest radiographs of patients with pleural fibroma typically demonstrate a well-defined, lobular, solitary nodule or mass, which may appear to be in the lung periphery and typically abuts a pleural surface or is located within a fissure. Pedunculated tumours may show mobility within the pleural space or changes in shape and orientation on fluoroscopy or with changes in the patient’s position. Hypertrophic osteoarthropathy is characterised by periosteal reaction without an underlying bone lesion; causes include bronchogenic carcinoma (squamous cell cancer being the most common), pulmonary lymphoma, lung abscess, bronchiectasis, pulmonary metastases, pleural fibroma and mesothelioma.

Answer 51

75. D. Anastomotic strictures usually appear on upper GI studies as irregular long segment narrowing at the gastrojejunal anastomosis. Extraluminal leak is the most serious early complication of Roux-en-Y gastric bypass, occurring in up to 5% of patients. Between 69% and 77% of leaks involve the gastrojejunal anastomosis, but other less common sites of perforation include the gastric pouch, blind-ending jejunal stump and jejunojejunostomy. Leaks usually occur within 10 days of surgery; early detection is critical because of the risk of abscess formation, peritonitis and sepsis, with a mortality rate of more than 5%. Affected individuals may present with leucocytosis, fever, abdominal pain and tachycardia. Transient anastomotic narrowing and obstruction may occur during the early post-operative period secondary to residual oedema and spasm in this region. Upper GI examinations may reveal focal narrowing of the gastrojejunal anastomosis and thickened, irregular folds in the Roux limb abutting the anastomosis. These findings usually resolve within several days. Strictures at the gastrojejunal anastomosis have been reported in 3%-9% of patients. These strictures typically develop 4 weeks or more after surgery; they may be caused by post-surgical scarring at the anastomosis or by chronic ischaemia resulting from tension on the gastrojejunostomy. Anastomotic strictures usually appear on upper GI studies as short segments of smooth narrowing at the gastrojejunal anastomosis. Though adhesions arc the most common cause of SBO after open Roux-en-Y gastric bypass, internal hernias are the most common cause after the laparoscopic form of surgery.

Answer 52

76. A. Seminoma Seminoma is the most common pure germ cell tumour. The imaging characteristics of seminomas reflect their uniform cellular nature. On US images, these tumours arc generally uniformly hypoechoic. Embryonal carcinoma is the second most common histologic type of testicular tumour after seminoma. The tunica albuginea may be invaded, and the borders of the tumour are less distinct, as expected; they are more heterogeneous and ill-defined than seminomas on US image. Yolk sac tumours account for 80% of childhood testicular tumours, with most cases occurring before the age of 2 years. Imaging findings are non-specific, especially in children, in whom the only finding may be testicular enlargement without a defined mass. After yolk sac tumour, teratoma is the second most common testicular tumour in children. The complex nature of teratoma is reflected in its sonographic appearance. Teratomas generally form well circumscribed complex masses. Cysts are a common feature and may be anechoic or complex, depending on the cyst contents (i.e., serous, mucoid or keratinous fluid). Cartilage, calcification, fibrosis and scar formation result in echogenic foci that may or may not produce posterior acoustic shadow. Testicular tumours from the sex cords (Sertoli cells) and interstitial stroma (Leydig ceils) constitute 4% of tumours. Their sonographic appearance is variable and is indistinguishable from that of germ cell tumours. Sertoli cell tumours are typically well-circumscribed, unilateral, round to lobulated masses. The sonographic appearance of testicular lymphoma is variable and indistinguishable from that of germ cell tumours. Testicular lymphoma generally appears as discrete hypoechoic lesions, which may completely infiltrate the testicle.

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77. C. Syringomyelia Neuropathic osteoarthropathy can be categorised as originating from a congenital or acquired cause. The acquired causes include a central origin (e.g., syringomyelia, spinal cord tumours and multiple sclerosis) or a peripheral origin (e.g., poliomyelitis, leprosy, diabetes mellitus and peripheral nerve injury).

Answer 54

78. A. Alobar holoprosencephaly Holoprosencephaly (HPE) is considered the most common malformation of the brain and face in humans. In alobar HPE, prosencephalic cleavage fails, resulting in a single midline forebrain with a primitive monoventricle often associated with a large dorsal cyst. The olfactory bulbs and tracts, the corpus callosum and anterior commissure, the cavum septum pellucidum and the interhemispheric fissure are absent, whereas the optic nerves may be normal, fused or absent. The basal ganglia, hypothalamic and thalamic nuclei are typically fused in the midline, resulting in absence of the third ventricle. In lobar HPE, the interhemispheric fissure is present along nearly the entire midline, and the thalami are completely or almost completely separated. The corpus callosum may be normal or incomplete, but the cavum septum pellucidum is always absent. Hydranencephaly is the result of a vascular insult (anterior circulation) with the cerebral hemispheres variably replaced by fluid covered with leptomeninges and dura Falx cerebri is present The cerebellum, midbrain, thalami, basal ganglia, choroid plexus and portions of the occipital lobes, all fed by the posterior circulation, arc typically preserved. It is differentiated from hydrocephalus by absence of an intact rim of cortex (seen with even the most severe hydrocephalus).

Answer 55

79. E. Chronic pulmonary embolism The tree-in-bud pattern on HRCT is characterised by small centrilobular nodules of soft-tissue attenuation connected to multiple branching linear structures of similar calibre originating from a single stalk. Initially described in cases of endobronchial Mycobacterium tuberculosis, it has subsequently been reported in peripheral airways diseases such as infection (bacterial, fungal, viral or parasitic), congenital disorders (like cystic fibrosis and Kartagener’s syndrome), idiopathic disorders (obliterative bronchiolitis, panbronchiolitis), aspiration, inhalation, immunologic disorders (like ABPA), connective tissue disorders and peripheral pulmonary vascular diseases such as neoplastic pulmonary emboli.

Answer 56

80. A. Pseudomeningocele The prognosis is better in postganglionic injuries, where surgical repair in the form of nerve grafting is possible. In preganglionic injuries, usually nerve root avulsions, direct surgical repair cannot be performed. A MRI scan of postganglionic injuries can show thickened nerves with a low signal intensity on T1-weighted images and an increased signal intensity on T2-weighted images. Nerve may be in contiguity, or there can be discontinuity with distal nerve contraction. Direct brachial plexus compression by a haematoma, fracture fragment or callus formation can also cause brachial plexopathy. A MRI scan of preganglionic injuries can show nerve root avulsions with or without pseudomeningocele. Pseudomeningoceles are cerebrospinal fluid collections resulting from a dural tear. The presence of a pseudomeningocele is a valuable sign. Spinal cord abnormalities occur in 20% of those with preganglionic injuries, such as oedema, haemorrhage and myelomalacia. An uncommon but useful finding is the enhancement of intradural nerve roots or root.

Answer 57

81. C. Hamartoma of tuber cinereum Hypothalamic hamartomas are developmental malformations consisting of tumour-like masses located in the tuber cinereum of the hypothalamus. Most patients present in the first or second decade of life, with boys being more commonly affected than girls. These lesions have been divided into parahypothalamic hamartomas and intrahypothalamic hamartomas. Parahypothalamic hamartomas are pedunculated masses attached to the floor of the hypothalamus. These lesions seem more likely to be associated with precocious puberty than with gelastic seizures. Intrahypothalamic hamartomas are sessile masses with a broad attachment to the hypothalamus. They lie within the hypothalamus and may distort the contour of the third ventricle. In addition, they seem to be associated more often with gelastic seizures than with precocious puberty. At MR imaging, they are seen as well-defined pedunculated or sessile lesions at the tuber cinereum and are isointense or mildly hypointense on T1-weighted images and iso to hyperintense on T2-weighted images, with no contrast enhancement or calcification. The absence of any long-term change in the size, shape or signal intensity of the lesion strongly supports the diagnosis of hypothalamic hamartoma.

Answer 58

82. B. Pleomorphic undifferentiated sarcoma Pleomorphic undifferentiated sarcoma was previously known as malignant fibrous histiocytoma. Malignant fibrous histiocytoma is the most common soft-tissue sarcoma of late adult life. It typically presents as a painless, soft-tissue mass, which is often located in the thigh and measures 5-10 cm. X-ray demonstrates a non-specific soft-tissue mass with calcification/ossification detected in 5%-20% of patients. Secondary osseous involvement is uncommon. It can be identified as periosteal reaction, cortical erosion and pathological fracture. CT findings include a non-specific, large, lobulated, soft-tissue mass of predominantly muscle density with nodular and peripheral enhancement of solid portions. There are often central areas of low attenuation, which represent myxoid change, old haemorrhage or necrosis. The lesion does not contain fat MRI typically reveals an intramuscular mass with heterogeneous signal intensity on all pulse sequences. As with other soft-tissue neoplasms, the signal intensity pattern is non-specific, usually low to intermediate on T1-weighted images and intermediate to high on T2 weighted images. Regions of prominent fibrous tissue (high collagen content) may demonstrate low signal intensity on both T1-weighted and T2-weighted images and calcification may present as foci of low signal on both T1-weighted and T2-weighted sequences.

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83. B. Metastatic disease to the liver is always calcified. The small bowel is the most common site of the gastrointestinal tract involved by melanoma. Appearance can be indistinguishable from that of primary or metastatic adenocarcinoma, lymphoma or other metastasis. Tumour masses may occur as infiltrating lesions with or without ulceration. Mesenteric involvement by melanoma can mimic lymphoma. Involvement of the large bowel is uncommon but can occur as large ulcerating lesions. Lesions in the liver can be single or multiple and may be partly calcified. Larger lesions are often necrotic.

Answer 60

84. D. Primary extragonadal germ cell tumours commonly affect the testes. Lymphoma can occur in the testis in one of three ways: as the primary site, as the initial manifestation of occult disease or as the site of recurrence. It is the most common bilateral tumour and epididymis and spermatic cord are commonly involved. Primary Leukaemia of the testis is rare. However, the testis is a common site of leukaemia recurrence in children. Testicular microlithiasis is an uncommon condition but several associations are known, including cryptorchidism, infertility, Klinefelter syndrome. Downs syndrome, atrophy, alveolar microlithiasis and testicular carcinoma. There is a calcifying subgroup of Sertoli cell tumours that can be multiple and bilateral with large areas of calcification and is known to be associated with Peutz-Jeghers syndrome and Carney syndrome. Primary germ cell tumours can occur outside the gonads and should be differentiated from regressed germ cell tumours with metastasis. Primary extragonadal germ cell tumours occur in extratesticular locations like the retroperitoneum, mediastinum, sacrococcygeal area and pineal gland. Regressed germ cell tumour may present with widespread metastases even though the primary tumour has involuted. US plays a vital role in the search for the primary regressed tumour. They have a variable appearance, are generally small, and can be hypoechoic, hyperechoic or merely an area of focal calcification.

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85. D. MRI of head with T2* GE and DWI When a child is admitted acutely with suspected NAHI, the primary neuroimaging performed on Day 1 is non-contrast CT of the brain. This has the advantage over MRI in the acute setting of being fast to acquire in a potentially unstable patient and is highly sensitive to hyperacute blood. The main aim at this stage is to diagnose/exclude any acute haemorrhage amenable to neurosurgical treatment. If the child has ongoing neurological signs/symptoms or an abnormal initial CT brain, then an MRI should be performed. This is normally done at 3-5 days. Contrast is not necessary but DWI - for ischaemia and T2* GE or similar sequence (for the detection of blood products) - should be considered. If there is abnormal imaging during the patient’s acute admission or persistent neurological signs or symptoms, then a repeat MRI brain at 3-6 months should be considered. If the first presentation is non-acute, then MRI is the appropriate initial imaging modality.

Answer 62

86. E. Comet tail sign is specific for distal ureteric calculus. Most textbooks of anatomy describe the ureter as having three anatomical narrowest points. These are the pelvi-ureteric junction (PUJ), the point where the ureter crosses anterior to the iliac vessels, and the uretero-vesical junction (UVJ); however, contrary to previous teaching there is debate whether these are the most common places for stones to be lodged. Indinavir stones have soft-tissue attenuation (15-30 HU) and are likely to be missed at unenhanced CT. However, renal colic in a patient receiving indinavir therapy for HIV infection, along with the presence of obstructive features at CT, usually helps clinch the diagnosis. The most reliable signs of ureteric obstruction include hydroureter, hydronephrosis, perinephric stranding, periureteral oedema, and unilateral renal enlargement. Stones less than 5 mm have a 68% chance of passing spontaneously, and stones between 5 and 10 mm have a 47% chance. The soft-tissue rim sign consists of a halo of soft-tissue attenuation around a calcific focus and is very specific for ureteric calculi. The comet tail sign is created by an eccentric tapering soft-tissue area adjacent to a phlebolith. These two signs are used to differentiate ureteric and pelvic calcification.

Answer 63

87. D. A fatigue fracture is due to abnormal stress on a normal bone. A fatigue fracture occurs from excessive and repeated stress on normal bone. An insufficiency fracture occurs from normal physiological stresses on abnormal bone. Both entities arc part of the larger group of fractures known as stress fractures, which is the term used to describe fractures occurring from a mismatch of bone strength and chronic mechanical stress.

Answer 64

88. E. Self-limiting disease of good prognosis Creutzfeldt-Jakob disease (CJD), a fatal neurodegenerative disorder, is diagnosed by the detection of an accumulation of an abnormal form of the human prion protein PrPSc in the brain. It is characterised by rapidly progressive dementia, cerebral atrophy, myoclonus and death. The T2-weighted MRI of sCJD (sporadic CJD) patients often shows high signal in the head of the caudate nucleus and in the putamen as compared with the thalamus and the cerebral cortex. Hyperintense signal changes can also occur in the thalamus, but in sCJD they are usually less prominent than those in the putamen or the caudate nucleus. In addition, there is high signal in the cerebral cortex in some cases. With the introduction of the new sequences FLAIR and DWI, these signal changes are more easily identified. Patients with the new variant of CJD (vCJD) show bilateral increased signal on MRI in the pulvinar thalami (relative to the grey matter of other basal ganglia and the cerebral cortex). There is currently no curative treatment and the disease is invariably fatal.

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89. C. Alcohol abuse In approximately 75% of patients, a haematologic abnormality or a cause of thrombotic diathesis can be identified that predisposes the patient to the occurrence of Budd-Chiari syndrome. The presence of multiple causes in the same patient has been reported. Haematologic diseases, especially myeloproliferative disorders, are the most common cause, and it has been suggested that patients with idiopathic Budd-Chiari syndrome may have an underlying myeloproliferative disorder. Causes of thrombotic diathesis that have been associated with Budd-Chiari syndrome include paroxysmal nocturnal haemoglobinuria, antiphospholipid syndrome, inherited deficiencies of proteins C and S and antithrombin III, factor V Leiden mutation, prothrombin gene mutation, methylene tetrahydrofolate reductase mutation, use of oral contraceptives, pregnancy and immediate post-partum status. Metastatic invasion of the hepatic vein, I VC or right atrium and primary tumour occurrence in the kidney, liver, adrenal gland, I VC or heart are less frequent causes of Budd-Chiari syndrome. Membranous web like obstruction of the hepatic vein or JVC is a more prevalent cause of hepatic venous outflow obstruction in the Asian population. Membranous webs of the hepatic vein or IVC may be congenital or represent sequelae of thrombosis.

Answer 66

90. B. Ostium primum ASD Ostium primum defects are often seen in Down’s syndrome and are part of endocardial cushion defects, which also include atrioventricular canal defects (ASD + VSD + abnormal AV valves). Most children with small defects are asymptomatic. Those with larger defects are predisposed to recurrent chest infection and heart failure. Ostium secundum type ASD are well tolerated, and symptoms and complications usually only present in the third decade or later. VSD can be asymptomatic or present at various age with recurrent chest infection or heart failure and cyanosis at a later stage subject to progressive pulmonary' hypertension. HOCM shows cardiomegaly without plethoric lungs. HOCM presents with tiredness, fatigability and is a recognised cause of sudden death.

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91. D. 0.3 ml of 1:1000 1M adrenaline Adrenaline IM dose - adults 0.5 mg IM (= 500 micrograms = 0.5 mL of 1:1000) adrenaline Adrenaline IM dose - children >12 years: 500 micrograms IM (0.5 mL) - i.e., same as adult dose; (300 micrograms (0.3 mL) if child is small or prepubertal) >6-12 years: 300 micrograms IM (0.3 mL) >6 months-6 years: 150 micrograms IM (0.15 mL) <6 months: 150 micrograms IM (0.15 ml.)

Answer 68

92. A. Osteosarcoma The most common radiation-induced sarcoma is pleomorphic undifferentiated sarcoma, previously described as malignant fibrous histiocytoma (which is a soft tissue sarcoma), followed by osteosarcoma and lastly by fibrosarcoma. In this case, the pathology is centred on the bone, making osteosarcoma the most probable diagnosis.

Answer 69

93. A. Brodel bloodless zone lies just anterior to the lateral convex border of the kidney. Percutaneous access to the urinary tract is used to relive urinary tract obstruction and also allows the urologists to perform endourological procedures (e.g., stone removal), which is less invasive and associated with fewer complications than open surgery. The renal artery divides into the ventral and dorsal branches, which creates a zone of relative avascularity between the divisions known as the Brodel bloodless line of incision, which lies just posterior lo the lateral convex border of the kidney. A lower pole posterior calix access via a subcostal approach is usually best for simple urinary drainage. A posterior calix of the upper or middle collecting system offers the easiest access to the pelviureteric junction for potential ureteral negotiation. Tubes with self-retaining properties should always be used to lessen the risk of inadvertent dislodgment. Tubes of 8-10 F are usually sufficient for drainage of non-infected urine. Larger tubes (12-14 F) may be necessary for drainage of infected urine or to ensure appropriate urine flow in procedures complicated by gross haematuria. Formal nephrostography should be delayed for 24-48 hours following tube placement in case of infected urine to reduce the chance of bacteraemia. Transient haematuria occurs in all patients post-nephrostomy. Hydrothorax and pneumothorax can also occur particularly with supracostal entries. Renal arteriovenous fistula, pseudoaneurysm or vessel laceration are recognised vascular complications during nephrostomy.

Answer 70

94. A. Primary CNS lymphoma Toxoplasmosis typically manifests on CT scans and MRIs as nodular (small encephalitis) and/or ring-enhancing (large abscess) lesions within the brain parenchyma. The enhancing ring, when present, may be somewhat thicker and more ill-defined than that seen in association with a typical bacterial abscess. The lesions are associated with surrounding oedema and tend to be multiple at presentation. However, a significant percentage of patients present with solitary lesions. Toxoplasmic lesions are most often seen in the basal ganglia and cerebral hemispheres. On non enhanced T1 -weighted MR images, the lesions are of low signal intensity. On T2-weighted MR images, the lesions are mildly to moderately hyperintense in relation to the brain parenchyma and can be difficult to separate from the surrounding oedema. The presence of small haemorrhages may be a sign of toxoplasmosis, and calcifications can occasionally be seen in treated lesions. On CT scans and MR images, lymphoma most commonly manifests as an enhancing, space occupying mass with surrounding oedema. However, much of the time the lesions undergo central necrosis and present as ring-enhancing masses; on non-contrast enhanced T1-weighted images, typical lesions are isointense in relation to brain parenchyma, whereas on T2-weighted images the lesions are isointense to hyperintense. On non enhanced CT, a small percentage of the lesions are of increased attenuation with respect to the brain parenchyma (as is commonly observed in cases of primary CNS lymphoma in patients who do not have AIDS). The imaging characteristics of lymphoma and toxoplasmosis overlap to such a significant degree that it is nearly impossible to differentiate the lesions on the basis of their appearance on CT scans or MR images alone. Patients with a few solid lesions or ring enhancing subependymal or periventricular lesions (particularly those with subependymal extension) tend to have lymphomas, whereas patients with multiple ring-enhancing lesions (particularly those that are haemorrhagic) in the basal ganglia and cerebral hemispheres are more likely to have toxoplasmosis.

Answer 71

95. B. Multilocular cystic nephroma Multilocular cystic nephroma is a benign renal tumour that occurs in children and, less commonly, adult women. There is no known association with Wilms tumour. It is usually a unilateral abnormality that replaces an entire renal pole and presents as a large mass, often around 8 10 cm in diameter. Radiological appearances, while not entirely specific, can help to differentiate this lesion from other renal mass lesions. A sharply well-circumscribed, multiseptated cystic mass is typical with a thick surrounding capsule. The cysts appear to herniate into the renal pelvis - an appearance that is relatively specific for mesoblastic nephroma. Unsurprisingly, these lesions are excised, as definitive radiological differentiation from malignancy is often not possible. Multilocular cystic nephroma can be differentiated from multicystic dysplastic kidney by the presence of normal functioning renal parenchyma and symmetrical renal excretion. Polycystic kidney disease involves the entire kidney, unlike multilocular cystic nephroma, which tends to be localised around a renal pole. Multicystic dysplastic kidney is the most common cystic renal disease affecting infants and is twice as common in boys. It is a common cause for abdominal masses in this age group and typically involves one kidney. There are strong associations with a range of genitourinary abnormalities, including vesico-ureteric reflux, horseshoe kidney and ureteric anomalies. The classical ultrasound features are as described above, with near total replacement of the normal renal parenchyma by cysts of varying size and shape. The presence of thin septations can help to differentiate this condition from multilocular cystic nephroma, in which thick septations are typical. Wilms tumour typically presents in children of 3-4 years of age.

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96. A. T3 N2 M1a Primary tumour (T) Tx: No tumour found on bronchoscopy or imaging. Tis: Carcinoma in situ. T1: Tumour size equal to or less than 3 cm not involving the main bronchus Tla: Smaller than 2 cm in longest dimension. Tib: Larger than 2 cm but smaller than or equal to 3 cm. T2: Tumour size more than 3 cm but less than/equal to 7 cm or involving the main bronchus but >2 cm from carina or visceral pleural involvement or lobar atelectasis extending to the hilum but not collapse of the entire lung. T2a: Larger than 3 cm but smaller than 5 cm. T2b: Larger than 5 cm but smaller than 7 cm. T3: Tumour size larger than 7 cm or tumour <2 cm from carina but not involving trachea or carina or involvement of the chest wall, including Pancoast tumour, diaphragm, phrenic nerve, mediastinal pleura or parietal pericardium, or separate tumour nodule(s) in the same lobe or atelectasis or post-obstructive pneumonitis of entire lung. T4: Any size tumour with involvement of the trachea, oesophagus, recurrent laryngeal nerve vertebra, great vessels or heart or separate tumour nodules in the same lung but not in the same lobe. Nodal status (N) Nx: Regional nodes cannot be assessed. N0: No regional nodal metastases. N1: Ipsilateral peribronchial, hilar or intrapulmonary nodes, including direct invasion N2: Ipsilateral mediastinal or subcarinal nodes. N3: Contralateral nodal involvement; ipsilateral or contralateral scalene or supraclavicular nodal involvement. Distant metastasis (M) Mx: Distant metastases cannot be assessed. M0: No distant metastases. Ml: Distant metastases present. M1a: Presence of a malignant pleural or pericardial effusion, pleural dissemination, or pericardial disease, and metastasis in opposite lung. M1b: Extrathoracic metastases.

Answer 73

97. A. Late enhancement of the IVC and central hepatic veins. Passive congestion occurs with the stasis of blood within liver parenchyma as a result of impaired hepatic venous drainage secondary to cardiac disease. Elevated central venous pressure is directly' transmitted from the right atrium to the hepatic veins. Passive hepatic congestion may occur with congestive heart failure, constrictive pericarditis, pericardial effusion, cardiomyopathy or right-sided valvular disease involving the tricuspid or pulmonary valve. Symptoms of congestive heart failure mask gastrointestinal symptoms. Patients may present with asymptomatic elevation of liver enzymes, jaundice, right upper-quadrant pain, hepatomegaly and increased abdominal girth. In the arterial phase, there is early enhancement of a dilated IVC and central hepatic veins because of the reflux of contrast material from the right atrium into the IVC. Parenchymal phase images show a heterogeneous, mottled mosaic pattern of enhancement, with linear and curvilinear areas of poor enhancement due to delayed enhancement of small and medium-sized hepatic veins. There may be peripheral large patchy areas of poor delayed enhancement due to stagnant flow within the periphery of the liver. Perivascular lymphedema may be seen as linear low-attenuation regions encircling the intrahepatic IVC or portal veins and should not be confused with venous thrombosis. Hepatomegaly and ascites may be present. Chest images may show cardiomegaly, congestive heart failure and pericardial and pleural effusion.

Answer 74

98. E. Lymphoma Lymphoma can occur in the testis in one of three ways: as the primary site, as the initial manifestation of occult disease or as the site of recurrence. It is the most common bilateral tumour, and the epididymis and spermatic cord are commonly involved. The sonographic appearance of testicular lymphoma is variable and indistinguishable from that of germ cell tumours. Testicular lymphoma generally appears as discrete hypoechoic lesions, which may completely infiltrate the testicle. Primary leukaemia of the testis is rare. However, the testis is a common site of leukaemia recurrence in children. Seminoma is the most common pure germ cell tumour but affects unilateral testis. Metastases are rare but are reported most commonly in cases of primary prostate and lung cancer. Testicular fracture usually appears as a linear hypoechoic band extending across the testicular parenchyma.

Answer 75

99. D. NF1 - Optic glioma NF1 is also called peripheral neurofibromatosis or von Recklinghausen disease. The classic triad includes cutaneous lesions, skeletal abnormalities and mental deficiency. CNS lesions include optic pathway glioma (thickened enhancing optic nerve), cerebral gliomas, hydrocephalus due to aqueduct stenosis, vascular dysplasia including Moyamoya disease, cranial nerve neurofibromas or craniofacial plexiform neurofibromatosis, CNS hamartomas (unidentified bright objects on T2-weighted MRI) and vacuolar/spongiotic myelinopathy. Spinal lesions include cord neurofibroma or neurofibroma of peripheral nerves. Optic nerve meningioma, seen as ring enhancement in cross section, would be suggestive of NF2 or central neurofibromatosis, classically associated with bilateral vestibular/acoustic schwannomas and ependymomas. Optic neuritis would also show nerve swelling, high signal on T2 and enhancement post-contrast on T1-weighted FS images; however, enlargement of the nerve on imaging may not be as pronounced as in glioma, and MS is not associated with skin lesions. Note that tuberous sclerosis can cause skin lesions but is associated with optic nerve hamartoma rather than glioma or optic neuritis.

Answer 76

100. A. They can cause painful scoliosis. When osteoid osteomas occur in the spine, they typically involve the posterior elements of lumbar vertebrae and are less than 2 cm in diameter. A painful scoliosis is a common presentation. The ‘nidus’ within the lesion is osteolytic. Both the nidus and soft-tissue components enhance on MRI after intravenous administration of contrast material.

Answer 77

101. A. Histoplasmosis Histoplasmosis is only seen frequently in North .America. Radiograph may reveal multiple poorly defined nodules in the acute phase. Segmental or lobar pneumonia is less common. Chronic histoplasmosis resembles post-primary TB, with upper lobe cavitation, calcification and fibrosis. Hilar and mediastinal nodes show' calcification. Occasionally a solitary well defined nodule may form, a so-called histoplasma. When the centre of this lesion calcifies, it forms a target lesion, which is very specific. In some cases, fibrosing mediastinitis can develop and lead to constriction of mediastinal structures, including airways, SVC, and pulmonary' arteries and veins.

Answer 78

102. B. Scurvy Scurvy is a dietary deficiency of vitamin C. It typically affects babies from 6 to 9 months and is characterised by non-specific symptoms of irritability, lower limb tenderness and reluctance to move legs normally. Bleeding gums can also occur. The condition usually manifests at the distal femur and proximal and distal ends of the tibia and fibula, and it can also affect the upper limb bones and the ribs. There are several key radiographic findings: **bony spurs arising from the metaphysis of long bones are eponymously termed Pelkan spurs.** Wimberger line refers to the appearance of a sclerotic line running around the perimeter of the epiphyses, which reflects osteopaenic change. Ground-glass osteoporosis and cortical thinning are also recognised findings. In contrast, rickets manifests as cupping and fraying of the metaphyses, periosteal reaction, bowing of the long bones and widening of the growth plates. Hypophosphatasia is often indistinguishable from rickets on imaging. Hypothyroidism in infancy also results in osteopaenia, with fragmentation of the epiphyses.

Answer 79

103. B. Irregular outline to liver with caudate lobe hypertrophy'. In acute viral hepatitis, the major histologic findings are necrosis of random isolated liver cells or small cell clusters, diffuse liver cell injury', reactive changes in Kupffer cells and sinusoidal lining cells and an inflammatory infiltrate in portal tracts, and evidence of hepatocytic regeneration during the recovery phase. Confluent necrosis may lead to bridging necrosis connecting portal, central or portal- to-central regions of adjacent lobules, signifying a more severe form of acute hepatitis. The imaging features of acute hepatitis are non specific and the diagnosis is usually based on serologic, virologic and clinical findings. Probably the most important role of radiology in patients with suspected hepatitis is to help rule out other diseases that produce similar clinical and biochemical abnormalities, such as extrahepatic cholestasis, diffuse metastatic disease and cirrhosis. At US, in acute hepatitis, the liver is often enlarged and may demonstrate a diffuse decrease in parenchymal echogenicity, which causes a relative increase in the echogenicity' of the portal vein walls (‘starry night' pattern). A normal liver echotexture does not exclude the diagnosis of acute hepatitis. At CT and MR imaging, findings in acute viral hepatitis are non-specific and include hepatomegaly and periportal oedema. At CT, heterogeneous enhancement and well-defined regions of low attenuation may be present. At MR imaging, periportal oedema appears as high signal-intensity areas on T2-weighted images. Involved areas may be normal or demonstrate decreased signal intensity on T1 weighted images and increased signal intensity on T2 weighted images. Extrahepatic findings in patients with severe acute hepatitis include gallbladder wall thickening due to oedema and, infrequently, ascites.

Answer 80

104. D. Testicular fracture requires urgent surgical exploration. Testicular fracture usually appears as a linear hypoechoic band extending across the testicular parenchyma. The contour remains smooth and the shape of the testicle is maintained. The tunica albuginea is intact. An associated haematocele or testicular haematoma may be seen. The fracture line may not be visible if filled with isoechoic haematoma. Testicular fractures are treated conservatively if normal flow is identified in the surrounding testicular parenchyma. In testicular rupture there is discontinuity of the echogenic tunica albuginea with haemorrhage and extrusion of testicular contents into the scrotal sac. This is an indication for emergency scrotal exploration to salvage the testis. US shows poorly defined testicular margins and heterogeneous echotexture, with areas of haemorrhage or infarction. Intratesticular haematomas are usually focal and fairly well defined and may be multiple. They are usually hyperechoic in the acute phase or hypoechoic (as the haemorrhage evolves) and lack vascularity. Isolated epididymal injuries are not very common, and these are usually associated with testicular injuries. Contusion or traumatic epididymitis appears as an enlarged and heterogeneous epididymis on US with increased vascularity, sometimes associated with haematocele. The appearance is indistinguishable from infective epididymitis. Hydrocele or scrotal haematoma can occur in isolation or be associated with other injuries.

Answer 81

105. C. Chronic ulnar collateral ligament injury Injury to the ulnar collateral ligament (UCL), also known as the medial collateral ligament or medial ulnar collateral ligament, is a common cause of medial elbow pain and valgus instability in athletes. The UCL is made of anterior, transverse and posterior bundles, and is most often injured following acute or recurrent valgus stress of the elbow. MRI may demonstrate increased T2 weighted signal within the ligament (commonly within the anterior band) or hyperintensity within the sublime tubercle. Intra-articular contrast may result in a ‘T sign’ when contrast extends in the interval between the sublime tubercle and stripped ligamentous attachment; complete rupture will show extravasation of contrast through the ligamentous defect. Chronic valgus stress, often secondary to throwing or pitching sports, can result in chronic damage to the UCL, with appearances similar to those described and the UCL often appearing lax, irregular and with poor definition. Plain radiograph findings may include heterotopic new bone formation around the medial epicondyle and local subchondral cysts, sclerosis and osteophyte formation. The differential diagnosis includes medial epicondylitis and a sublime tubercle fracture. Lateral ulnar collateral ligament forms part of the lateral ligament complex and presents with symptoms of lateral or postero-lateral elbow pain/instability.

Answer 82

106. C. The severity of the skin rash correlates with the degree of articular abnormalities. If there is joint space narrowing, signs of inflammation, multiple joint involvement and distal involvement in the hands and feet with added features of bone proliferation, a seronegative spondyloarthropathy is suggested. Approximately 10%—15% of patients with skin manifestations of psoriasis will develop psoriatic arthritis. Usually such manifestations will precede the development of arthritis. The hallmarks of psoriatic arthritis, similar to those of the other seronegative spondyloarthropathies, are signs of inflammatory arthritis combined with bone proliferation, periostitis, enthesitis and a distal joint distribution in the extremities. Involvement of several joints in a single digit, with soft-tissue swelling, produces what appears clinically as a ‘sausage digit’. The bone proliferation produces an irregular and indistinct appearance to the marginal bone about the involved joint, characterised as a ‘fuzzy' appearance or ‘whiskering’. Periostitis may take several forms. It may appear as a thin periosteal layer of new bone adjacent to the cortex, a thick irregular layer or irregular thickening of the cortex itself. Because of the degree of bone destruction, an involved joint may take the appearance of a pencil and cup’, with one end of the joint forming a cup and the other a pencil that projects into this cup. One characteristic feature of psoriatic arthritis in the foot is the ‘ivory phalanx’, which classically involves the distal phalanges (especially in the first digit). Sacroiliac joint involvement in psoriatic arthritis is usually bilateral, either symmetric or asymmetric in distribution. The thoracolumbar spine may show large comma-shaped paravertebral ossifications. There is no association between the dermatological extent of psoriasis and the musculoskeletal manifestations.

Answer 83

107. C. Skeletal dysplasia NF2 or central neurofibromatosis is associated with bilateral acoustic neuromas (sine qua non), schwannoma of other cranial nerves, multiple meningiomas, meningiomatosis, paraspinal neurofibromas and spinal cord ependymomas. Unlike NF1, NF2 is not associated with Lisch nodules, skeletal dysplasia, optic pathway glioma, vascular dysplasia or mental deficiency.

Answer 84

108. C. US abdomen Be aware of a child who is presumed to have throat or upper respiratory infection, on treatment by GP, who presents with atypical abdominal pain. Younger children cannot describe their symptoms, and up to one third have atypical clinical findings for appendicitis. Lower abdominal pain and flexed leg should raise strong suspicion of a serious pathology'. Urine test is abnormal in 30% of acute appendicitis; hence it doesn’t help to confirm or refute the diagnosis. CT involves ionisation radiation, and MRI is not the primary modality of investigation. US is the primary' modality for assessment of the abdomen in children. The most accurate US finding for acute appendicitis is an outer wall diameter greater than 6 mm under compression. Less sensitive and specific US findings for appendicitis include hyperaemia within the appendiceal wall on colour Doppler images, echogenic inflamed periappendiceal fat and the presence of an appendicolith. Enlarged, reactive mesenteric lymph nodes may be seen with or without appendicitis. Mesenteric adenitis is a controversial differential of acute appendicitis and is generally considered as a diagnosis of exclusion.

Answer 85

109. C. Metastasis The causes of multiple macronodules (>5 mm) include metastasis (the first thing that needs to be excluded unless there is a pre-existent explanation), granuloma, eosinophilic lung disease (eosinophilia, asthma or typical reverse batwing pattern radiograph), abscesses, AVM (history of Osler-Rendu-Weber disease), Wegner's disease (associated sinus disease, renal dysfunction), rheumatoid lungs (symptoms of connective tissue disease or arthropathy), amyloidosis (chronic disease), parasites and sarcoidosis (uveitis, parotitis or features of Lofgren syndrome).

Answer 86

110. B. Nodular liver contour Cirrhosis is most commonly caused by chronic hepatitis infection or alcohol abuse, although a number of other diseases causing hepatic injury can lead to cirrhosis. It is pathologically defined by three main characteristics: fibrosis, nodular transformation and distortion of hepatic architecture. Subtle morphologic changes of the liver may be among the earliest detectable with imaging, including enlargement of the hilar periportal space, enlargement of the major interlobar fissure and expansion of pericholecystic space or gallbladder fossa. Typically, the anterior segment of the right lobe and medial segment of the left lobe atrophy, whereas the caudate lobe and left lateral segment hypertrophy. The nodular changes in cirrhosis yield characteristic radiologic findings. The nodularity is best seen affecting the liver margin, especially on the left lateral segment. Micronodular cirrhosis, common in alcoholic liver disease, gives rise to a fine cobblestone appearance resulting from nodules typically smaller than 3 mm. A grossly nodular liver margin with 3-15-mm regenerative nodules is characteristic of macronodular cirrhosis, more commonly associated with viral hepatitis. Other changes in cirrhosis include diffuse heterogeneity of the organ on CT and Tl- and T2-weighted MRI. Fibrosis is the predominant cause for hepatic heterogeneity and appears high in signal intensity on T2-weighted MRI.

Answer 87

111. C. It is typically unilateral. Testicular microlithiasis is a relatively uncommon finding in the general population. It is usually an incidental finding, which was initially thought to be innocuous. However known association include cryptorchidism, infertility, Klinefelter syndrome, Down’s syndrome, atrophy, alveolar microlithiasis and, most importantly, testicular carcinoma. The prevalence of carcinoma in patients with testicular microlithiasis has been reported to be as high as 40%, and follow up US was routine. However, recent articles and guidelines do not recommend regular US follow-up. At histopathologic analysis, the microcalcifications appear as laminated concretions within the seminiferous tubules, secondary to defective Leydig cells. On sonograms, microlithiasis appears as punctate, non-shadowing, hyperechoic foci within the usually homogeneous testicle. Five or more calcifications/image should be present to make the diagnosis. Typically, they are bilateral, symmetric and scattered throughout the testicle; however, they can be asymmetrically distributed or unilateral.

Answer 88

112. B. Pineal teratoma Pineal teratomas reveal a multiloculated, lobulated lesion with foci of fat attenuation, calcification and cystic regions on CT scan. T1-weighted MR images may show foci of T1 shortening due to fat and variable signal intensity related to calcification. On T2-weighted images, the soft-tissue component is iso- to hypointense. The soft-tissue component demonstrates enhancement on post contrast images. Pineocytomas are slow-growing pineal parenchymal neoplasms. At CT they are well demarcated, usually less than 3 cm, and iso- to hyperattenuating. At MR imaging, pineocytomas are well circumscribed lesions that are hypo- to isointense on T1-weighted images and hyperintense on T2-weighted images. On post-contrast images, they typically demonstrate avid, homogeneous enhancement. Cystic or partially cystic changes may occur, occasionally making differentiation from a pineal cyst difficult. However, at immediate post-contrast imaging, cystic-appearing pineocytomas demonstrate internal or nodular wall enhancement. Pineoblastomas arc highly malignant pineal parenchymal neoplasms. CT reveals a large (typically >3 cm), lobulated, typically hyperattenuating mass, an appearance that reflects its highly cellular histologic features. Nearly 100% of patients have obstructive hydrocephalus. At MR imaging, pineoblastomas are heterogeneous in appearance, with the solid portion appearing hypo- to isointense on T1-weighted images and iso to mildly hyperintense to the cortex on T2-weighted images. Pineoblastomas demonstrate heterogeneous enhancement on post-contrast images. Necrotic regions and haemorrhage may be present. CSF dissemination is a common finding and necessitates imaging of the entire craniospinal axis. Ninety percent of patients with pineal germinomas are less than 20 years old. CT demonstrates a sharply circumscribed, hyperattenuating mass that engulfs the pineal calcifications. Hydrocephalus may be present. MR imaging typically reveals a solid mass that may have cystic components. Germinomas are iso- to hyperintense to grey matter on Tl and T2-weighted images and demonstrate avid, homogeneous enhancement on post-contrast images.

Answer 89

113. D. Contrast flowing in an apparently thickened vessel wall Direct signs of chronic PE include complete occlusion with decrease in the diameter of the vessel distal to the complete obstruction; intimal irregularities, as broad-based, smooth, margined abnormalities that create obtuse angles with the vessel wall; and intraluminal bands or webs. Indirect signs of chronic PE include post-stenotic dilatation, tortuous vessels, enlargement of the main pulmonary artery, enlarged bronchial artery and differential perfusion of lung parenchyma (mosaic pattern). The polo mint sign of acute PE refers to the well-defined central thrombus, which is completely surrounded by contrast material.

Answer 90

114. D. Echocardiography and blood culture Children with turbulent blood flow through the heart or where prosthetic material has been inserted following surgery for PDA, VSD, coarctation and so on are at particular risk of acute and subacute forms of infective endocarditis. In the early stage symptoms are mild. Children can present with prolonged fever over months accompanied by non-specific symptoms like malaise, myalgia, arthralgia, headache, weight loss, night sweats or an acute episode of fever. Tender nodules in finger suggest Osler's node. Clubbing, retinal haemorrhage (Roth spots), nail bed haemorrhage and splenomegaly could be other features of infective endocarditis. Blood culture and echocardiography to demonstrate vegetations is the main modality of investigation. Although MRI and CT would show vegetations, they arc not the primary modality for investigation.

Answer 91

115. A. Regenerative nodules are premalignant. Cirrhotic livers are characterised by advanced fibrosis and the formation of hepatocellular nodules, which are classified histologically as either (1) regenerative lesions (e.g., regenerative nodules, lobar or segmental hyperplasia, focal nodular hyperplasia) or (2) dysplastic or neoplastic lesions (e.g., dysplastic foci and nodules, hepatocellular carcinomas). The differentiation of these lesions is important because regenerative nodules are benign, whereas dysplastic and neoplastic nodules are premalignant and malignant, respectively. However, their accurate characterisation may be difficult even at histopathologic analysis. Comparing the clinical and pathologic findings with radiologic imaging features may facilitate differential diagnosis; in particular, nodule size, vascularity, hepatocellular function and Kupffer cell density assessed at MRI are suggestive of the correct diagnosis. MRI is more useful than CT for such assessments because it provides better soft-tissue contrast and a more nuanced depiction of different tissue properties. Moreover, a wider variety of contrast agents is available for use in MR imaging. Familiarity with the MR imaging characteristics of cirrhosis-associated hepatocellular nodules is therefore important for optimal diagnosis and management of cirrhotic disease.

Answer 92

116. E. 720 Testicular torsion causes venous engorgement that results in oedema, haemorrhage and subsequent arterial compromise. The degree of torsion ranges from 180 to 720 degrees. Experimental studies indicate that 720 degree torsion is required to completely occlude the testicular artery. When torsion is 180 degrees or less, diminished blood flow is seen. A nearly 100% salvage rate exists within first 6 hours after onset of symptoms, which drops to 20% within 12-24 hours.

Answer 93

117. D. Large flowing osteophytes Sacroiliac involvement is typically bilateral and symmetric, and it usually precedes spinal involvement in ankylosing spondylitis. Initially, there is indistinctness and discontinuity of the thin white subchondral bone plate about the sacroiliac joints. These changes can progress to gross bone erosions. Early erosions of the subchondral bone are often best seen in the inferior aspect of the joints. Along with the bone erosions, the adjacent bone is often sclerotic and joint space narrowing and bone fusion eventually occur. The differential diagnosis of bilateral sacroiliac joint erosions includes inflammatory bowel disease and hyperparathyroidism; however, in hyperparathyroidism, sacroiliac joint space widening is more dramatic. Early radiographic findings are erosions at the anterior margins of the vertebral body at the discovertebral junction. These focal areas of osteitis become increasingly sclerotic, a finding termed the ‘shiny comer sign’. More extensive discovertebral erosions may also occur (Anderson lesion). Associated bone proliferation leads to a squared appearance of the vertebral body. Thin and slender syndesmophytes are generally evident, representing ossification of the outer layer of the annulus fibrosis. The differential diagnosis for bone production at the vertebral margins includes diffuse idiopathic skeletal hyperostosis, or DISH, although this latter condition more commonly reveals a flowing and undulating appearance. As the syndesmophytes thicken and become continuous, the term bamboo spine is used on anteroposterior lumbar spine radiographs. Facet joint inflammation leads to indistinctness and narrowing of the involved joint, and bone fusion of the joints appears later. Ossification of the posterior interspinous ligaments produces a dense radiopaque line, designated the ‘dagger sign', on anteroposterior radiographs of the lumbar spine. The combination of the fused facets and ossification of the interspinous ligaments produces the ‘trolley-track sign’. Disk calcification may also occur. Other peripheral joints can be involved in ankylosing spondylitis. Hip involvement is usually bilateral in distribution.

Answer 94

118. C. Pituitary apoplexy Pituitary apoplexy is a severe and potentially fatal medical condition characterised by the variable association of headache, vomiting, visual impairment, ophthalmoplegia, altered mental state and panhypopituitarism. The syndrome is often related to haemorrhagic infarction of the pituitary gland, usually in a condition of a pre-existing macroadenoma. CT typically a heterogeneously hyperdense (haemorrhagic components) intrasellar lesion, with significant increase in size in comparison to previous imaging. MRI shows a similar finding, with the appearance of blood varying on T1-weighted and T2-weighted images, based on the interval between haemorrhage and imaging. In the subacute phase (7-21 days), methaemoglobin shortens the T1 relaxation time, and the haemorrhage will appear hyperintense on T1 weighted images as well as on T2-weighted images. In the chronic phase (>21 days), macrophages digest the clot and the presence of haemosiderin and ferritine causes a strong hypointensity on both T1 -weighted and T2-weighted images.

Answer 95

119. B. Traumatic diaphragmatic rupture The presenting features include respiratory distress, tracheal deviation and dullness to percussion on one side. Motor vehicle accidents are the cause of traumatic diaphragm rupture in 90% of cases, with falls from height and a kick to the abdomen or object falling on the abdomen as alternative aetiologies. The initial chest X-ray is abnormal in 40%-90% of cases. It may show irregularity or obscuring of the leaf of the diaphragm, fractured ribs, mediastinal shift, intrapleural fluid or detectable viscera within the thorax. The most important radiological sign is incomplete visualisation of the entire diaphragm.

Answer 96

120. C. The accordion sign is classic in Crohn’s disease. Several patterns of wall attenuation have been described in association with specific diseases. A hyperattenuating wall is seen with haemorrhage as a result of trauma, purpura or vasculitis. A submucosal fatty halo has been described as a result of chronic inflammation, such as in inflammatory bowel disease and GVHD. Submucosal oedema is definitive evidence of a bowel wall injury (typically acute), often producing the target sign. The accordion sign is caused by contrast material trapped between thickened oedematous haustral folds in the colon. Although the accordion sign is most commonly seen in pseudomembranous colitis, it is not pathognomonic. The comb sign represents hypervascular engorged vasa recta aligned like the teeth of a comb on the mesenteric site of the bowel. This finding is classically seen in inflammatory bowel disease, especially Crohn’s disease, and suggests a clinically active disease. The comb sign can also be seen in vasculitis and purpura. The toothpaste or lead pipe sign has been associated with chronic diseases leading to a ‘featureless’ bowel. It is commonly seen with Crohn’s disease or chronic GVHD or as the sequela of radiation therapy.

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