Diagnosis and treatment of an insulinoma in a guinea pig (Cavia porcellus).

METHODS

A 5-year-old male guinea pig (Cavia porcellus) was examined because of lethargy, weight loss, and episodic neurologic signs, including paddling in lateral recumbency, head tilt, and circling. Prior to initial examination, the animal was treated with corn syrup whenever it appeared lethargic, plus an unknown dosage of sulfadimethoxazole.

RESULTS

The animal was thin, with abdominal distention and subtle torticollis. Chemistry panel results documented hypoglycemia (45 mg/dL). Corn syrup was discontinued in favor of a high-fiber formula fed via a syringe. Measurement of blood insulin concentration demonstrated hyperinsulinemia (> 1,440 pmol/L [> 201 μU/L]), with concurrent hypoglycemia (0.6 mmol/L [11 mg/dL]).

RESULTS

Diazoxide treatment for presumptive insulinoma was started at a dosage of 5 mg/kg (2.3 mg/lb), p.o., every 12 hours. A blood glucose curve demonstrated persistent hypoglycemia, and the diazoxide dosage was gradually increased to 25 mg/kg (11.4 mg/lb), p.o., every 12 hours. A second glucose curve measurement 12 days later confirmed adequate euglycemic control. Three weeks after the initial diazoxide dosage increase, the animal was reexamined for constipation and abdominal distension and died the following day. Histologic analysis confirmed a pancreatic beta-cell tumor (insulinoma).

CONCLUSIONS

To the authors' knowledge, this is the first report of premortem diagnosis and treatment of an insulinoma in a guinea pig. This case demonstrates that diazoxide treatment can help achieve euglycemia in hypoglycemic guinea pigs and is a potential treatment option for guinea pigs with insulinoma.