2010 Radiology Exam - Abdomen Case 2

History: Six year old spayed female domestic short hair cat with a clinical history of progressive distention of the abdomen.

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Radiographic Findings: A severely enlarged left kidney is noted. The enlargement is displacing the intestines ventrally and to the right of the abdomen. In addition, the right kidney is small and irregular with foci of mineralization. Two additional mineralized structures, likely representing ureteroliths, are noted in the area of the right ureter on the VD projection. The differential diagnoses should include a perinephric pseudocyst, severe hydronephrosis from a possible ureteral obstruction, and less likely a neoplastic process such as lymphoma. Changes associated with the right kidney were considered the result of chronic renal disease.

Candidate Performance: No candidate failed to recognize the presence of the mass. Many candidates correctly considered hydronephrosis as a possibility due to the presence of ureteroliths noted on the VD projection. However, the list of differential diagnoses was often incomplete. Some candidates included adenocarcinoma, transitional cell carcinoma and renal abscess high in the list, but these abnormalities usually exhibit an enlarged, irregular non-kidney shape. A small number of candidates who failed the case were unable to recognize the retroperitoneal origin of the mass and included a peritoneal mass of splenic origin in the differential diagnosis.

Histological Diagnosis: Perinephric pseudocyst.