A 13.5 year-old female spayed West Highland White Terrier was presented to the Cornell University Hospital for Animals (CUHA) after a 2-day history of anorexia and vomiting. Initial diagnostics disclosed increased hepatobiliary enzymes (ALT, ALP, GGT), hyperbilirubinemia, and a severely distended gallbladder, adjacent anechoic fluid, and reactive hyperechoic fat suggestive of biliary leakage. Peritoneal cytology was consistent with a suppurative process and an exploratory laparotomy was performed. The suspected site of biliary leakage was identified during surgery and a cholecystectomy was performed. A thyroid panel collected previously was consistent with a diagnosis of primary hypothyroidism and was thought to play a role in the pathogenesis of necrotizing cholecystitis seen in this patient. Four months after the procedure, the patient was doing well both clinically and on laboratory assessment.