Insulinoma in Dogs

Canine insulinoma is a rare disease, yet it is the most common tumor of the endocrine pancreas. Insulinomas receive this name because they affect the endocrine functions of the pancreas, which handle hormone control—including insulin. Most regularly, insulinomas put an excess of insulin into the body. Insulinoma occurs most often in middle-aged and older dogs, averaging nine years in age. They affect both sexes and are more likely in larger breeds. The most commonly afflicted breeds are German Shepherds, Irish Setters, Boxers, Golden Retrievers and Terriers.

Canine insulinoma affects the endocrine function in a way that an excess of insulin is put out into the body. This excess of insulin induces hypoglycemia (low blood sugar) in the body. This decrease in blood sugar can result in the following symptoms:

• Lack of coordination
• Confusion
• Lack of alertness
• Changes in behavior
• Weakness
• Disturbance of vision
• Muscle degeneration
• Decrease in reflex of appendages
• Seizures
• Collapse
• Coma
• Death

Types

There are two distinct kinds of pancreatic cancer, both of which have separate symptoms, diagnoses, and treatments.

• Exocrine carcinomas are cancerous tumors that impact the exocrine functions of the pancreas. An exocrine carcinoma impacts the digestive enzymes produced by the pancreas. Exocrine carcinomas spread quickly to the lining of the stomach, liver, and other organs.
• Endocrine carcinomas are cancerous tumors that impact the endocrine functions of the pancreas. An endocrine carcinoma impacts the hormone production of the pancreas. These tumors can affect other parts of the body through their influence on hormone production. Additionally, they may spread quickly to the liver and lymph nodes.
• Insulinoma is an endocrine carcinoma that primarily affects the production of insulin by the pancreas, causing a decrease in blood sugar known as hypoglycemia.

As with many forms of cancer, there is no definitive cause for pancreatic cancer. It is believed that there is a genetic component to the likelihood of this cancer occurring, supported by the prevalence of the disease in certain breeds and body types. Ultimately, any definitive causation of pancreatic cancers, including insulinoma, is unknown.

Because of an insulinoma’s effect, a persistent case of hypoglycemia is very suggestive of the presence of an insulinoma. To diagnose an insulinoma, multiple tests may be conducted, including:

• Multiple blood tests
• Analysis of insulin and glucose levels
• Abdominal ultrasound/x-rays
• Abdominal surgery

In most cases, abdominal surgery is required to definitely diagnose insulinoma. The process involves opening the abdomen so that the surgeon can feel the pancreas for any tumors. In addition, a blue stain is used to mark any insulinoma cells in the pancreas.

There are a few initial steps in treatment that can aid in regulating the dog’s blood sugar:

• Feeding the dog small meals through the day
• Medication to help raise blood sugar
• Diazoxide can be used to supplement insulin secretion

It is important to address the hypoglycemia and get it under control before continuing treatment for the insulinoma. Once the hypoglycemia has been addressed, surgery is usually the only successful treatment for insulinoma, and even then the prognosis is poor. During surgery, the dog will be monitored for pancreatitis, which can be fatal.

There are several medications that can aid in suppressing insulinoma and keeping it from spreading, but be aware; they can have toxic side effects.

After surgery, the dog will have a recovery period and will need to be monitored closely for reoccurrence of hypoglycemia. It’s possible that the veterinarian will suggest dietary restrictions and multiple feedings through the day to maintain blood sugar. In the event that hypoglycemia is still present after surgery, this means that part of the tumor is still present in the body. At this point chemotherapy may be required, but the prognosis for survival is not good. On average, survival rates of insulinoma range from 6 to 24 months after diagnosis.