Ultrasonographic features and blood biochemistry findings of cholangiocarcinoma in a captive polar bear (<i>Ursus maritimus</i>)

ABSTRACT A 29‐year‐old male captive polar bear ( Ursus maritimus ) with a year‐long history of elevated gamma‐glutamyl transpeptidase (GGT) presented with a 2‐week history of anorexia and abdominal distention. Blood biochemistry revealed a severely elevated GGT (&gt;1500 IU/L). Abdominal ultrasound revealed multiple cystic hepatic masses and marked ascites. Fourteen days after initial presentation, the patient was found dead. Postmortem examination revealed hepatomegaly with diffuse, multifocal, coalescing cysts containing a red‒tan to dark‐red serous fluid. Histopathologically, the cyst walls were lined by flattened or cuboidal neoplastic cells, some exhibiting tubulopapillary projections into the lumen. Metastatic lesions were identified in the anterior mediastinal lymph nodes, lungs and kidneys. This case was diagnosed as cholangiocarcinoma. While there are numerous reports of cholangiocarcinoma in polar bears, published data on blood biochemistry and abdominal ultrasonographic findings are limited. This case report illustrates the benefit of blood biochemistry and abdominal ultrasound in investigating cholangiocarcinoma in polar bears.