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Model Answers

Case 1

Case 1 Model Answer:

Findings and interpretation:

First CT:

  • There is a round, calcified structure in the right iliac fossa on the non-contrast sequence, most likely representing an appendicolith.
  • There is dilatation of the small bowel loops.
  • The appendix is dilated, filled with fluid, and shows a thickened, enhancing wall; this represents appendicitis.
  • There is mild free pelvic fluid.


Second CT:

  • The liver demonstrates heterogeneous, mottled enhancement and a patchy hepatogram. The peripheral zones of the liver are enhancing less than the centre.
  • There is hepato-splenomegaly.
  • There is no contrast enhancement in the hepatic veins.
  • There is periportal oedema.
  • While the appendix was removed, the appendicolith is still present within a fluid collection with an enhancing wall.
  • There are a few encapsulated fluid collections in the pelvis with enhancing walls, representing abscesses.
  • There are focal areas of abdominal wall soft tissue thickening (at umbilicus and left lower anterior abdominal wall), representing the port sites from laparoscopic surgery.


The first CT shows acute appendicitis.

In the second CT which was obtained post appendectomy, there is occlusion of hepatic venous outflow caused by complete hepatic vein thrombosis, with characteristic features of acute Budd Chiari syndrome in the liver. There are also post-operative abscesses, one of which contains the appendicolith that was retained during the surgery.


Principal diagnosis:

Acute appendicitis, followed by acute Budd Chiari syndrome post appendectomy and post operative abscesses.


Differential diagnosis:

None in this case.



Immediately alert referring physician of findings to initiate urgent treatment (these cases are usually managed by anticoagulation).

Case 1 Your Answer:

No Answer Submitted

Case 2

Case 2 Model Answer:

Pneumonia with haemorrhagic encephalitis

Findings and interpretation:


  • There is widespread, patchy airspace opacification in both lungs, most pronounced over the mid-zones, with relative sparing of the apices and bases.
  • There is a central line in situ, with the tip in adequate position at the SVC / right atrial junction.


  • There are multiple intra-axial, space occupying T2 and FLAIR hyperintense lesions located in both cerebral hemispheres, mostly centred on the left basal ganglia, and periventricular, deep and subcortical white matter in a bilateral, asymmetrical distribution. There is also a lesion in the left cerebellar hemisphere. Some of the lesions extend to the cortex and cause sulcal effacement.
  • The largest lesion at the left basal ganglia is causing significant mass effect with midline shift to the right, with effacement of the ipsilateral lateral ventricle and dilatation of the contralateral one. The third ventricle is also effaced.
  • The lesions show restricted diffusion, appearing bright on DWI with corresponding low ADC values.
  • The lesions show punctate areas of the blooming artefact on the gradient echo sequence, denoting haemorrhagic areas within.
  • There is T2 hyperintensity in the mastoid air cells bilaterally, as well as almost all of the paranasal sinuses.

Negative findings:

  • There is less vasogenic oedema than expected for the size of the lesions.
  • The cortex is mostly spared by the lesions.


The chest findings represent widespread consolidation in the lungs.

The brain findings represent a likely inflammatory / demyelinating process which mostly involves the white matter, which underwent haemorrhagic transformation.


Principal diagnosis:

Pneumonia complicated by the development of acute haemorrhagic leuko-encephalitis (AHEM)


Differential diagnosis:

Chest: the differential diagnosis of widespread consolidation is wide and includes infectious pneumonia, pulmonary haemorrhage, pulmonary oedema and aspiration pneumonia among others.


  • Infectious encephalitis
  • Lymphoma or toxoplasmosis in patient with AIDS
  • Fulminant multiple sclerosis
  • Vasculitis



Urgently contact referring physician and inform of findings. These cases are usually managed by high dose corticosteroid administration.

Perform contrast enhanced MRI brain for further evaluation.

Case 2 Your Answer:

No Answer Submitted

Case 3

Case 3 Model Answer:

Telangiectatic osteosarcoma

Findings and interpretation:


  • There is a lytic, slightly expansile lesion in the proximal metaphysis of the tibia, showing indistinct borders and wide zone of transition. The lesion extends past and erodes the adjacent cortex.
  • There is a modest amount of reactive sclerosis in the surrounding bone.


  • There is a T2/PD hyperintense and T1 hypointense mass lesion arising eccentrically from the medulla and invading into the cortex with extension into the adjacent soft tissues and anterior muscle compartment of the lower leg.
  • The lesion contains components that are hyperintense on T1, and other components that contain fluid-fluid levels on the T2 sequences with material of varying signal intensity within. This represents blood products of varying ages and layering of these products.
  • There is a modest amount of T2/PD signal intensity surrounding the lesion, indicating mild surrounding oedema and minimal periosteal reaction.
  • The lesion is moderately enhancing on the post-contrast sequences, with greater enhancement of the septae surrounding the blood filled spaces.

Pertinent negative findings:

  • The surrounding bone marrow does not show significant oedema.
  • The lesion does not cross the physeal plate.
  • There is no associated pathological fracture.


The findings indicate an aggressive bony lesion, which is partly made up of blood filled spaces. This most likely represents a malignant primary bone tumour.


Principal diagnosis:

Telangiectatic osteosarcoma.


Differential diagnosis:

  • Osteosarcoma with haemorrhagic component.
  • Aneurysmal bone cyst: this is extremely unlikely as these lesions have a narrow zone of transition and do not invade into the surrounding soft tissue.



Alert referring physician of findings.

Recommend staging CT thorax abdomen pelvis.

Recommend bone scan to search for multiple bone involvement.

Recommend discussion at sarcoma MDT regarding image guided biopsy for histopathological diagnosis (this should be planned with the orthopaedic surgeons in order to avoid biopsy tract seeding in tissue that will not be resected). It may be more appropriate to refer to tertiary sarcoma centre for further management.

Case 3 Your Answer:

No Answer Submitted

Case 4

Case 4 Model Answer:

Pulmonary embolism on background of metastatic breast cancer with bony metastases

Findings and interpretation:

Chest radiograph:

  • There is uniform opacification projected over the right lower and mid lung zones, indicating a pleural effusion.
  • There are multiple sclerotic bony lesions in the ribs at the right hemithorax, as well as multiple thoracic vertebrae.

CT chest and CTPA:

  • A right sided mastectomy has been performed.
  • The right lung is reduced in volume, and demonstrates segmental and basal atelectasis in the lower lobe.
  • There is generalised pleural thickening at the right hemithorax, with an encysted pleural fluid collection within, which is heterogeneously hyperdense and likely contains blood products.
  • There is a saddle shaped filling defect at the bifurcation of the main left pulmonary artery, which extends into the 2nd order arteries supplying the lingula and left lower lobe.
  • There are multiple sclerotic bony lesions in the thoracic vertebrae, ribs and sternum.
  • The right ventricle appears larger than the left ventricle with flattening of the interventricular septum, indicating possible right ventricular strain.

Pertinent negative findings:

  • There are no enlarged mediastinal or axillary lymph nodes.

The findings represent pulmonary embolism on top of a metastatic process, with deposits in the bone and spread to the pleura. The pleural thickening and bloody effusion are causing restriction of lung volume and atelectasis on the affected side. The origin is most likely a resected breast carcinoma.


Principal diagnosis:

Acute pulmonary embolism on a background of resected breast carcinoma with malignant spread to multiple sites.


Differential diagnosis:

  • Pleural thickening and effusion of a different etiology, such as infection or connective tissue disease (however, this is highly unlikely given the finding of mastectomy and sclerotic metastases).



Immediately inform referring physician of pulmonary embolism diagnosis.

These cases are usually managed with immediate anticoagulation.  

Case 4 Your Answer:

No Answer Submitted

Case 5

Case 5 Model Answer:

Multiple organ ischaemia and infarction

Findings and interpretation:

  • There is branching, intrahepatic gas involving the left lobe of the liver and extending to the peripheral margins. This extends to the main portal vein, SMV and peripheral mesenteric veins. The left lobe of the liver is hypo-enhancing.
  • There is gas in the walls of multiple small bowel loops (mostly jejunal), indicating pneumatosis coli. There is also gas in the gastric walls, indicating gastric emphysema.
  • There are multiple, geographic areas of hypo-enhancement in the spleen, representing infarcts. Wedge shaped areas of hypo-enhancement in the left kidney also represent infarcts. The right kidney is atrophic, and is uniformly hypo-enhancing.
  • There is extensive atherosclerotic plaque disease and mural calcification involving the abdominal aorta; the proximal SMA shows an atherosclerotic plaque which is causing stenosis of the lumen. There is thrombosis of the right renal artery.
  • The adrenal glands are hyper-enhancing bilaterally.
  • There is a nasogastric tube in situ, with the tip in satisfactory position.
  • There is minimal free fluid in the peritoneal cavity.

Pertinent negative findings:

  • Both the SMA and coeliac axis are patent.


The findings represent pneumatosis intestinalis as a sign of mesenteric ischaemia involving the jejunum, as well as infarctions in multiple visceral organs. This may be caused by shock / systemic hypoperfusion rather occlusion of the visceral arteries.


Principal diagnosis:

Mesenteric ischaemia.


Differential diagnosis:

  • Other causes of pneumatosis intestinalis such as surgery / patients on a mechanical ventilator / COPD; however, this is extremely unlikely because of the clinical presentation and infarction in other organs.



  • Immediately contact the referring physician and notify them of the findings.
  • Emergency laparotomy is required in these cases.

Case 5 Your Answer:

No Answer Submitted

Case 6

Case 6 Model Answer:

AT/RT and pericallosal lipoma with corpus callosum agenesis

Findings and interpretation:

  • There is a large space occupying lesion in the left parietal lobe, composed of solid and cystic elements. The solid component appears isointense to grey matter on the T2 and FLAIR images.
  • There are multiple septations and CSF filled spaces of varying size within the lesion.
  • The lesion is surrounded by T2 and FLAIR hyperintensity in the white matter, indicating vasogenic oedema.
  • The solid component demonstrates avid enhancement on the post-contrast images, with less enhancement of the septae.
  • There is a large lesion in an extra-axial, midline location. This is well defined and shows markedly high signal on T1 and T2 images. This represents a mass entirely composed of macroscopic fat.
  • The lateral ventricles run lateral to one another, giving a ‘racing car’ appearance on the axial images and a ‘viking helmet’ appearance on the coronal images. The corpus callosum cannot be identified.


The findings indicate an aggressive neoplastic mass in the brain, on top of a congenital malformation  with an associated benign mass.


Principal diagnosis:

AT/RT (atypical teratoid/ rhabdoid tumour) with corpus callosum agenesis and associated pericallosal lipoma.


Differential diagnosis:

The aggressive mass:

  • PNET / embryonal tumour with multi-layered rosettes
  • Teratoma
  • Childhood glioblastoma multiforme



Alert referring physician of findings.

Recommend discussion at neuro-oncology MDT with regards to further management.

Case 6 Your Answer:

No Answer Submitted
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