This week we challenged the residents with cross-sectional imaging cases. The first year residents did an especially good job on their first CT and MR images.
Case 1
The first case was a mature dog that had been treated for lymphoma 2 years previously. He presented with enlarged lymph nodes in the head and neck. On the contrast CT images, the retropharyngeal lymph nodes were enlarged peripherally, with a non-enhancing central area. The mandibular lymph nodes were mildly enlarged. Differential diagnoses included inflammatory disease (abscess) and lymphoma. Most people ranked inflammatory disease first because of the central, probably necrotic, area of the lymph node. The history of prior lymphoma kept neoplasia on the list as well. Diagnosis: Immune mediated lymphadenitis.
Case 2
This older cat was anorexic and lethargic with neurologic signs. There were multiple MR sequences including T1, T2, T1 post-contrast and Flair images. The most striking finding was the increased degree of meningeal enhancement post-contrast. This led to a radiographic diagnosis of meningitis, with differentials including FIP, lymphoma, and other infectious disease. A CSF tap was recommended, and the key was to check the sagittal image to see if there was evidence of cerebellar herniation. There was no herniation in this case. The cat was older for FIP, but one comment was that the age of presentation depends on the age at exposure to the virus. Diagnosis: FIP.
Here’s a link to a case of FIP with slightly different findings on MR.
Case 3
This was an MR of an old Terrier with neurologic signs (there was minimal neuro history on all the cases!). The images showed multifocal lesions in the grey and white matter, with the largest in the left parietal and frontal lobes. The large lesion was hypointense on T1, hyperintense and complex on T2, with edema in the white matter visible on T2 images. All of the lesions had rim enhancement post-contrast. A T2* weighted GRE sequence was requested to determine if the complexity in the larger mass was hemorrhage. All of the lesions looked hypointense on this sequence because hemorrhage produced susceptibility artifact. Diagnosis: Metastatic hemangiosarcoma. Further diagnostics could include abdominal ultrasound, thoracic radiographs, and echocardiography to check for other common sites of hemangiosarcoma. Interesting comments included the fact that hemorrhage often looks complex on T2, and that multifocal aspergillosis can also cause hemorrhage.
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