Abstract
A 7-year-old spayed female Shih Tzu dog was presented for evaluation of recurrent hypoglycemia. Serum insulin levels during hypoglycemia were 35.3 μIU/mL. Ultrasonography and computed tomography showed a mesenteric nodule between the kidney and the portal vein, but no pancreatic mass was observed. During surgery, the nodule had neither anatomical adhesions nor vascular connections to the pancreas. Pancreatic inspection and palpation revealed no abnormalities. Hypoglycemia improved after resection of the nodule. Histopathological examination confirmed the nodule to be an islet cell carcinoma. Although extremely rare, ectopic insulinoma should be considered as a possible cause of insulin-induced hypoglycemia in dogs.