Everything you need to know about insulinoma in dogs

Canine insulinoma is an insulin-secreting tumor on a dog’s pancreas that leads to increased production of insulin. Dogs with an insulinoma show clinical signs associated with chronic low blood sugar, such as seizures, weakness, difficulty walking, and reduced mental awareness. Even though the condition is rare in dogs, it’s the most common type of canine pancreatic tumor. Read on to discover:

• What is an insulinoma?
• Symptoms of insulinoma in dogs
• How vets make a diagnosis of insulinoma in dogs
• How insulinoma in dogs is treated

Surgery is the foundation of treatment for insulinoma in dogs, though not every pancreatic mass can be removed. Feeding small meals with complex carbohydrates, limiting exercise, and using medication to increase blood sugar levels are also usually part of the treatment plan. Insulinoma can be managed well in some canine patients but is ultimately fatal.

Canine insulinoma is a tumor of insulin-secreting cells, known as beta cells, in the pancreas of a dog. Insulinomas are usually solitary and small but have severe effects on a dog’s health, not only because of the insulin they produce but also because they are almost always cancerous and the cancerous cells have spread to other parts of the body (metastasized) by the time of diagnosis.

The beta cells in the pancreas secrete insulin for blood sugar regulation. When too many beta cells develop and form a small mass, this is an insulinoma. Healthy beta cells are highly regulated and only release insulin when it’s needed to process blood sugar. Beta cell tumors don’t respond to the body’s regulatory efforts and release excessive insulin. If there’s too much insulin, the affected dog will experience low blood sugar, or “hypoglycemia.” Severe or persistent hypoglycemia is life-threatening. Steps can be taken to regulate the blood sugar of a dog with an insulinoma, but the long-term prognosis of insulinoma is poor.

Stages of insulinoma

The vast majority of insulinomas, about 95% of cases, are malignant. Insulinoma can be categorized by stage, depending on how the tumor has spread. The stages of insulinoma are:

• Stage 1: The cancer is confined to the pancreas
• Stage 2: The cancer has spread to local lymph nodes
• Stage 3: The cancer has spread distantly, often to the liver

Around half of canine insulinoma cases have reached stage two and metastasized by the time the insulinoma is diagnosed.

Early clinical signs of insulinoma are vague and nonspecific, making the disease difficult to detect. Symptoms can be episodic and spaced apart, influenced by meals and exercise, and become more frequent and severe over time. Most clinical signs are associated with chronic hypoglycemia, such as:

• Weakness
• Seizures
• Difficulty walking or wobbly gait
• Loss of consciousness
• Reduced mental awareness
• Twitching or trembling

Neurologic signs, such as seizures, are common when blood sugar is extremely low. Other clinical signs may be present if the tumor has spread to somewhere else in the body.

Is low blood sugar in dogs an emergency?

In a healthy dog, multiple mechanisms keep blood sugar, or blood glucose, within a narrow range. Severely low blood glucose levels can be life-threatening, affecting the brain and leading to severe neurological symptoms. If the brain can’t get blood glucose for energy, it essentially starves, affecting the entire body.

If your dog shows any of the signs associated with hypoglycemia, take them to the vet as soon as possible.

Other conditions can cause symptoms similar to those that appear in dogs with low blood sugar, even when their blood glucose levels are normal. These conditions include:

• Mobility disorders
• Neurological conditions
• Toxicosis after ingesting a toxin, such as cannabis

For canine patients presenting with weakness, a wobbly gait, or seizures and who also have low glucose levels during initial blood tests, the underlying cause is usually something other than insulinoma. Other causes that have similar clinical signs include:

• A complication of insulin therapy for diabetes mellitus
• A congenital problem in newborn toy breeds
• Ingestion of an artificial sweetener, such as xylitol
• Portosystemic shunt
• Pancreatitis
• Addison’s disease (hypoadrenocorticism)

Diagnostic tests are used to rule out other, more common causes of low blood sugar. Recommended testing may include:

• Routine blood panels
• Urine tests
• Diagnostic imaging, such as X-rays, ultrasounds, or CT scans
• Neurologic tests

Insulinomas are small but can sometimes be seen on diagnostic imaging. If an insulinoma is suspected, the dog may have its blood sugar levels tested again after being fasted. Fasting causes blood glucose levels to go down. It can be very dangerous for dogs with insulinoma, so this test must be done under veterinary supervision. If a dog has an insulinoma, their insulin levels will remain high even when blood glucose levels are low. A definitive diagnosis of insulinoma is needed for treatment.

Medical treatment of dogs with insulinoma includes:

• Emergency stabilization of hypoglycemia
• Medication to suppress insulin production and/or raise blood sugar levels
• Surgery to remove the tumor
• Palliative care
• Chemo and radiation therapy

Surgery is the treatment of choice for dogs with insulinoma. Removing the tumor gives the best chance for relief from clinical signs and the best survival time. However, not all tumors can be surgically removed. “Insulinomas are small and can be difficult to identify, and pancreatic tissue is very fragile and does not respond well to trauma or handling during surgery,” explains Dr. Jo Myers, a veterinarian on Vetster. “As a result, complications are common and patients must be closely monitored during and after surgery.” Surgery is usually not curative and only provides a partial, temporary solution, with most patients eventually requiring medical management.

Medical management of insulinoma includes:

• Frequent small meals with complex carbohydrates
• Limited exercise
• Medication to help prevent hypoglycemia

Most dogs will require some form of medical management even after tumor removal. Prognosis varies by stage and the individual dog but is generally regarded as poor. If the tumor has metastasized at the time of diagnosis, dogs undergoing surgery and medical therapy tend to survive only seven to nine months.

If surgery isn’t an option, medical management is usually helpful for relief of symptoms and can be provided as a form of palliative care.

Chemotherapy options for insulinoma are currently being studied and may be more widely available in the future.

Can insulinoma in dogs be cured?

Even with successful surgery, most dogs will still require some form of medical management because hypoglycemia is likely to return due to tumor cells that have metastasized or been left behind.

Dogs undergoing treatment for insulinoma may enjoy a good quality of life for several months or even more than a year, but the chances for long-term survival are poor. It’s difficult to keep an affected dog’s blood sugar within the narrow, healthy range, and complications eventually develop. Chronic hypoglycemia can cause permanent brain damage as well as other serious effects throughout the body. The life expectancy of a dog with insulinoma ranges from a few weeks to a few years.

If your dog has been diagnosed with insulinoma and you have questions, or you’re concerned about your dog’s symptoms, veterinary professionals are available for online virtual care appointments to offer support and professional advice.

How long can dogs live with insulinoma?

The life expectancy of a dog with an insulinoma varies from a few weeks to a few years. Survival times vary based on how early the insulinoma was caught, how it’s treated, and how well it responds to treatment.

What are the symptoms of insulinoma in dogs?

Dogs with an insulinoma have chronic low blood sugar levels due to increased insulin levels in the body, leading to clinical signs such as seizures, weakness, difficulty walking, loss of consciousness, and other neurological signs. If the insulinoma has metastasized to another area of the body, it can cause additional symptoms.

What are the stages of insulinoma in dogs?

Insulinomas are usually malignant and can be categorized into one of three stages. Stage 1 insulinoma remains confined to the pancreas. Stage 2 insulinoma has spread to nearby lymph nodes. At stage 3, the insulinoma has metastasized to more distant areas, often to the liver.