Extrahepatic biliary obstruction due to ampullary carcinoma in a dog.

Neoplasia-related extrahepatic biliary obstruction (EHBO) is rare in dogs. An 11-year-old spayed mixed-breed dog had intermittent jaundice for several months. Imaging showed a lesion extending from the distal common bile duct to the major duodenal papilla. To relieve EHBO, transduodenal ampullectomy was performed, followed by partial duodenectomy including the papillary orifice and cholecystoduodenostomy. Histopathological examination revealed ampullary adenocarcinoma with invasion into the duodenal muscularis propria; margins were tumor-free. At >2 years after surgery, metastasis was not detected, and the dog remained clinically well. To our knowledge, this is the first report of canine ampullary carcinoma, suggesting that transduodenal ampullectomy can be useful for both palliative biliary decompression and the assessment of invasion depth to guide subsequent definitive surgery.