Insulinoma is a term used to describe an insulin-secreting mass. Insulinomas are functional tumors of the beta cells of the pancreas. A functional tumor is one that produces a hormone, in this case insulin. It can occur in both dogs and cats.
Unregulated production of insulin leads to low blood glucose (sugar). Low blood can glucose cause neurologic signs:
- seizures
- collapse
- generalized weakness
- dull mentation
Diagnosing and managing pets with low blood sugar can be an intensive task requiring 24-hour care. Your primary care veterinarian may consider referral to a specialty hospital with an ACVS board-certified veterinary surgeon as well as a veterinary internist where advanced diagnostics, intensive care, and advanced surgery can all occur.
Insulinoma is ultimately only definitively diagnosed with a biopsy taken at surgery. Tests that would support performing surgery in your pet are:
- paired low blood glucose with simultaneously high blood insulin
- decreased blood fructosamine
- ultrasound or CT (cat scan) finding of a pancreatic mass
Treatment of pets with insulinoma involves a combination of both medical and surgical approaches.
Medical
Medical therapy involves raising or stabilizing blood glucose through diet and drugs.
- Diet: Nutritional therapy is instrumental and your veterinarian will probably prescribe a high fiber diet that will allow sugars to be slowly absorbed. Feeding small meals frequently also helps stabilize blood glucose to avoid spikes and troughs.
- Steroids: These potent drugs have many effects, which include stimulating the liver to produce more sugar.
- Streptozocin: This antibiotic selectively destroys β-cells of the pancreas and/or at metastatic sites.
- Diazoxide: This medication decreases the secretion of insulin, stimulates liver sugar production, and decreases cell use of sugar.
- Octreotide: This medication inhibits insulin synthesis and secretion.
- Glucagon infusion: A polypeptide hormone given to help increase blood glucose levels by maintaining glucose production via glycogenolysis and gluconeogenesis. It can be used in hospitals to help elevated blood glucose level until more definitive therapy can be performed.
Surgical
Surgery is essential to definitively diagnose, stage, and treat pets with insulinoma.
- The goal of surgery is to remove as much disease as possible by removing insulin-secreting masses. Typically, this involves removal of part of the pancreas. In many pets, this will cause the glucose to be normal for some period of time.
- Your veterinary surgeon will also assess every abdominal structure for evidence of spread (metastasis). If other masses are observed, they will also be removed or biopsied depending on their size, number, and location.
Expect your pet to be hospitalized after surgery for 1 to 3 days. The most important part of post-surgical care is allowing them to rest. There will also be medications to administer for pain relief and some veterinary surgeons prescribe antibiotics. Making sure that your pet is eating and comfortable will be your primary post-operative responsibilities.
Sometimes when an insulin secreting mass is removed, the blood glucose becomes very high because the body has down-regulated insulin production, and re-starting production takes time. Additionally, when the pancreas is manipulated, it can become inflamed, causing pancreatitis. Pancreatitis can cause pets to vomit, not want to eat, and have abdominal pain. In some cases, the blood glucose remains low, indicating that there is residual microscopic disease. If your pet has had low blood glucose for a long-time, permanent nerve damage may have occurred leaving them with an uncoordinated gait or weakness.
Metastasis, tumor regrowth, and return of clinical signs of low blood glucose are some of the concerns following surgery and medical management. Dogs with a single mass that is removed surgically have the best prognosis, surviving 1½ to a little over two years. Up to 80% of patients have a single mass. Dogs with a normal blood glucose or elevated blood glucose have a better prognosis than those that have persistent low blood glucose following surgery. Pets with metastatic disease at the time of diagnosis do not do as well, surviving 7 to 9 months with a combination of surgery and medical therapy.
Premier Sponsors
