Free‐floating intraperitoneal necrotic lipoma in a guinea pig (Cavia porcellus)

An approximately 3‐year‐old, male, neutered, black Dutch guinea pig (Cavia porcellus) was presented for routine health check shortly following adoption. Physical examination revealed an incidental non‐painful, firm, highly mobile, ovoid mass ventrally in the mid‐abdomen. The remaining examination was otherwise normal, and investigation was declined due to lack of clinical signs. The guinea pig was re‐presented 2 months later, as it appeared less interactive. The mass was unchanged, but mild abdominal pain was present on palpation. Ultrasound examination revealed a 60 × 40 mm discoid, hyperechoic mass with multiple hypoechoic, well‐demarcated cavitary areas. Exploratory laparotomy was performed and a free‐floating, dark tan, smooth, firm, biconvex mass was removed without further dissection or ligation. Clinical signs resolved in the first week, and the animal remained clinically normal 3 months postoperatively. A necrotic lipoma was confirmed on histology, and should therefore be a differential for an abdominal mass in this species.