Insulinoma is a rare tumor originating from the beta cells of a dog’s pancreas. These functional tumors produce and release hormones. An insulinoma secretes excessive insulin into the bloodstream, regardless of blood sugar levels. This unregulated production leads to hypoglycemia, or abnormally low blood glucose.
Identifying Insulinoma Symptoms
Symptoms of insulinoma in dogs stem from persistent low blood sugar (hypoglycemia). Owners might observe generalized weakness or a wobbly, uncoordinated gait. These symptoms can be episodic, appearing and disappearing, and sometimes worsen after exercise or prolonged periods without food.
Dogs may also exhibit neurological signs due to the brain’s reliance on glucose for energy. Disorientation, confusion, or a lack of alertness are common. Muscle twitching, trembling, or even full-blown seizures and collapse can occur as blood sugar levels drop significantly.
Changes in appetite, such as increased hunger (polyphagia), might be noticed as the body attempts to counteract the low blood sugar. In severe cases, profound hypoglycemia can lead to a comatose state.
Diagnosing Insulinoma
Diagnosing insulinoma begins with a comprehensive physical examination and a detailed history of the dog’s symptoms. Veterinarians perform blood tests to measure blood glucose levels, which are often low. If blood glucose is below 60 mg/dL, further insulin level testing is pursued.
The presence of high insulin levels concurrently with low blood glucose is highly suggestive of an insulinoma. Routine blood counts and urinalysis are usually normal, helping rule out other causes of hypoglycemia.
Advanced imaging techniques are then employed to locate the tumor and check for spread. Abdominal ultrasound is a common initial imaging test, though it may only detect about half of insulinomas. Computed tomography (CT) scans offer higher sensitivity, around 71%, in identifying pancreatic masses and assessing for metastasis to regional lymph nodes, liver, or lungs. In some instances where imaging is inconclusive but suspicion remains high, exploratory surgery may be recommended for definitive diagnosis through biopsy.
Treatment Options
Treatment for canine insulinoma involves surgical and medical approaches, depending on the tumor and the dog’s health. Surgical removal (partial pancreatectomy) is the primary method for clinical sign relief and improved survival. During surgery, the veterinary surgeon will also examine the abdomen for any evidence of tumor spread, such as to the lymph nodes or liver, and remove or biopsy these if present.
Medical management becomes important when surgery is not feasible, if the tumor has widely metastasized, or if hypoglycemia recurs after surgery. This involves medications aimed at raising blood glucose or reducing insulin secretion.
Prednisone, a corticosteroid, is often used to increase blood glucose by stimulating the liver to produce more sugar and decreasing the body’s sensitivity to insulin. Diazoxide is another medication that directly inhibits insulin release from the pancreatic beta cells and promotes glucose production. It is often introduced if dietary management and prednisone alone do not adequately control blood sugar levels. Other therapies, such as octreotide, a synthetic hormone that can inhibit insulin synthesis, may also be considered.
Long-Term Management and Prognosis
Long-term management focuses on maintaining stable blood glucose and improving quality of life. Dietary modifications are key, involving frequent small meals throughout the day (every 4-8 hours). These meals should be high in protein and complex carbohydrates, with low amounts of simple sugars, to prevent sharp spikes in blood glucose that can trigger excessive insulin release.
Owners should also be prepared for potential hypoglycemic crises, having a rapidly absorbed sugar source like honey or corn syrup readily available to administer orally if signs of low blood sugar appear. Regular monitoring of blood glucose levels is also necessary to adjust medication dosages and dietary plans as needed.
While insulinoma is frequently malignant, with metastasis often present at diagnosis in about 50% of cases, proper management can significantly extend a dog’s life. Prognosis varies, but dogs with both surgical and medical management often have longer survival, potentially up to two years. However, clinical signs of low blood sugar may eventually return due to tumor regrowth or spread.