An insulinoma, also called an insulin secreting beta-cell tumor, is a tumor of the pancreas that will cause hypoglycemia (low blood sugar).  It is this abnormally low blood sugar level, not the tumor itself, that typically causes the clinical signs and problems associated with insulinomas.  Clinical signs can range in severity and include increased appetite and weight gain, weakness, fainting, seizures, vomiting and diarrhea, or any combination of these.

In our experience, virtually all beta-cell neoplasms in dogs are malignant.  Sometimes these metastasis can be detected at the time of diagnosis, sometimes they are not “found” for months after apparent successful treatment.

Treatment options for this problem focuses on two main paths: surgical removal of the tumor, and medical therapy to minimize the hypoglycemic events.  Specific chemotherapy that is effective against neoplastic insulinomas is not currently reported.

Surgery remains a relatively aggressive mode of therapy because of the high incidence of metastatic disease, the older age of many of the affected animals, and the variable response to surgery.  Surgery does afford the possibility of a “cure” if excision is complete and there are no metastatic lesions present.  Unfortunately, even during surgery, many metastatic lesions may not be seen because they are microscopic in size. For this reason, even dogs that seem “cured” with surgery will have a recurrence of the disease several months to a year or longer down the road.  Additionally, some tumors may be in such a location in the pancreas as to make complete removal impossible.  Even in these cases, surgical debulking may improve the response to medical management.

Medical management revolves around nonspecific treatments to keep the blood sugar up in a normal range, and thereby reduce the incidence and severity of clinical signs.  Most commonly  frequent feedings and glucocorticoids (steroids) are employed initially.  Other medications options are available, consultation is recommended to determine the best plan for each individual.  Frequent feedings of diets that are high in proteins, fats, and complex carbohydrates are recommended, and in some animals this alone will alleviate clinical signs for months.  Simple sugars (including semi-moist dog foods) should be avoided because they may directly stimulate even higher insulin secretion.  As long as the pet can eat, honey, maple syrup, and other simple sugars should be avoided.  Glucocorticoids directly antagonize the effects of insulin at the cellular level and are, therefore, used as a first line therapy for medical management of insulinomas.

The mean survival time for dogs treated medically is about 12 months.  The ability of surgery to alter the long term prognosis depends in large part on the presence or absence of metastatic disease.  In a recent report from The University of California at Davis, about 2/3 of the patients did not live beyond 6 months after surgery for various reasons, and 1/3 lived beyond 6 months, some of these lived well beyond a year after surgery.