Insulinoma in dogs - From Diagnosis to Life Expectancy

Dog insulinoma is a rare disease that causes life-threatening hormonal imbalances.

The source of the ailment can be found in your dog’s pancreas. His pancreas is composed of beta cells that release just the right amount of insulin when the cells are functioning properly.

Corrupted neoplastic beta cells form tumors that produce excess pancreatic insulin. Excessive amounts of insulin in the body causes hypoglycemia or low blood sugar.

Pets are a source of so much joy. When they become ill, the quality of life of the entire household suffers.

It’s in those moments that you’ll want the expert advice of a veterinarian.

These doctors specialize in preventing, diagnosing, and treating many common animal ailments and ones that aren’t so common such as canine insulinoma, also known as pancreatic cancer.

What Is Canine Insulinoma?

Dog insulinoma is classified as a type of endocrine carcinoma.

This type of carcinoma impacts hormone production. When hormonal processes are disrupted, they confuse the voluntary and involuntary functions throughout the body.

Voluntary Processes

A dog’s voluntary nervous system controls everything they are consciously aware of. For example, moving their legs.

Involuntary Process

The involuntary processes (involuntary nervous system) control the things a dog doesn’t have to think about in order for it to work. This includes things like breathing, heartbeat, and metabolism.

Insulinoma in Dogs Can Spread

Like other endocrine carcinomas, insulinomas are cancerous and can easily spread to other parts of your dog’s body.

While dog insulinoma isn’t a very common disease, it tends to be devastating when it strikes.

According to statistics that the National Library of Medicine recently published, the rate of metastasis for dogs that have insulinoma is as high as 95%.

Insulinoma in Dogs: Breeds at Risk

Medical researchers continue to study dog insulinoma in hopes of finding definitive causes for the disease.

Some experts say that the ailment is caused by a lack of adequate exercise, but others point to genetic anomalies.

Published research highlights certain dogs that are at the greatest risk for insulinoma. For example, large breed dogs are at the highest risk for developing dog insulinoma according to multi-year studies.

The types of dogs that are particularly susceptible to the disease are:

Golden retrievers
Irish setters
German shepherds.

These dogs tend to develop insulinoma when they reach their middle age or senior years.

For instance, studies indicate that older dogs usually develop the disease in their 10th year of life. In perspective, the average lifespan of a German shepherd is 10 to 12 years.

Stages of Insulinoma in Dogs

Dog insulinoma has three classification stages:

Stage I insulinoma

At this stage, insulinoma is found only in the pancreas and has a 785-day median survival time (MST). In other words, 2.15 years.

Stage II insulinoma

Stage II insulinoma occurs when the disease migrates to the lymph nodes. Dogs that have Stage II insulinoma have a 547-day median survival time (MST). In other words, approximately 1.5 years.

Stage III Insulinoma

Stage III insulinoma is characterized by widespread metastasis. Dogs that have reached this insulinoma stage have a 217-day median survival time (MST). Sadly, that is only 7 months.

Common Symptoms of Insulinoma in Dogs

Symptoms are usually inconsistent, popping at at different times. Since insulin is only released periodically, the symptoms only show up periodically.

The top symptoms to look for include:

physical collapse
loss of consciousness (syncope)
seizures
extreme weakness

A Deeper Dive into the Symptoms of Insulinoma in Dogs

Dog insulinoma occurs when excessive insulin is secreted into the body, which drives down your dog’s blood sugar levels.

Your dog needs glucose, and the brain is the primary user of it. When your dog runs low on glucose, he can experience a lack of alertness.

If your dog has insulinoma, he likely has a mix of good and bad days.

The tumor that secretes excessive insulin doesn’t have a regular release schedule. You may believe that your dog is fine after he eats a meal, and he may not exhibit any strange behavior for a while.

The next week he may collapse from extreme muscle weakness because of the surplus insulin in his system.

The sooner that you get your dog tested for insulinoma, the better his chance of survival.

Neurological Issues

The sudden onset of neurological issues is a common sign that your dog has insulinoma.

Your dog loves going out for long walks in the morning. He normally finds his leash and paws at your bedroom door to make sure that you’re ready to go. A dog that has insulinoma may not be able to locate his leash or favorite toys due to vision impairment.

You’ll particularly notice those vision disturbances in dogs that need to navigate stairs.

The neurological problems that result from insulinoma are serious. Besides showing a general state of confusion, a dog that has insulinoma can start having seizures.

The lack of glucose to the brain can also put your dog into a coma or result in death.

Low Blood Sugar

Your dog’s muscles run off of stored glycogen, which is a form of sugar. When your dog’s blood sugar levels are low as a result of insulinoma, he will likely exhibit a lack of enthusiasm for once-loved exercise and a lack of physical coordination.

If examined, your dog will probably show signs of muscle deterioration if insulinoma has been left unaddressed for a long time.

Diagnosis of Insulinoma

One of the first things that a DVM will do to diagnose your pet is laboratory testing.

He or she will take a blood sample and determine your dog’s serum insulin concentration level.

If your dog’s lab work shows that he has high insulin levels and is hypoglycemic, the doctor will often determine that the dog has insulinoma.

The doctor may monitor your dog’s blood glucose levels for a period of time when he or she suspects insulinoma.

Testing and Lab Work

If your DVM suspects that your dog has insulinoma, he or she will conduct laboratory tests to find out your dog’s true physiological condition.

Insulinoma is a complex ailment to identify since many of its symptoms are indicators of other diseases. After ruling out the presence of these other diseases, your DVM can make a more accurate prediction of how your dog will respond to treatment.

A whole-body scan gives a more detailed picture of your dog’s physical condition and helps doctors find the source of the insulinoma.

Common sites that show signs of insulinoma include the:

pancreas
liver
regional lymph nodes.

Surgical Biopsy

However, DVMs want to know that tumors on these areas are actually malignant before doing surgery to remove them. They do a surgical biopsy to make a sure diagnosis and determine the stage of the disease.

Defeating insulinoma often requires doctors to remove part of the pancreas to get rid of a tumor.

Pre-Surgery Testing

Before surgery, your DVM will perform a series of imaging tests such as chest x-rays and abdominal ultrasound to find out if the disease has spread to other parts of your dog’s body.

A CT scan is one of the most effective tools for pre-surgical insulinoma screening.

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Prognosis of Insulinoma in Dogs

After finding out as much as possible about your dog’s fight with insulinoma, your DVM will attempt to predict how your dog will react to different treatment options.

For instance, your dog’s insulinoma may be confined to one tumor on his pancreas and has not spread to his liver.

In that case, the DVM may opt to conduct a partial pancreatectomy to remove the tumor and the surrounding diseased tissue.

He or she may forgo medical therapy for normalizing a low glucose level by predicting that your dog’s pancreatic beta cells will resume normal function after the diseased tissue has been surgically removed.

A poor prognosis often brings more medical treatments and lower survival rates.

Treatment Options

If your dog has been diagnosed with insulinoma, your DVM will prescribe the best treatment options for his specific make up and disease progression.

There are three main treatments, and your doctor can prescribe them singly or in combination to extend the life of your pet.

Diet Management

Your DVM will evaluate your dog’s diet and suggest modifications that lower spikes in insulin secretion.

One change may include removing foods from your dog’s diet that represent simple carbohydrates that convert to sugar quickly.

These foods should be replaced with those that are higher in complex carbohydrates, protein, and healthy fats.

Balancing your dog’s blood glucose concentration is key to insulinoma treatment success. Blood sugar levels are properly maintained by giving your dog small meals throughout the day.

DVMs often pair this dietary approach with the other two treatment options for the best results. It is very rare that a DVM will only prescribe dietary management to treat dog insulinoma.

Surgical Management

When it comes to treating dog hypoglycemia that stems from insulinoma, surgical resection is the most widely used option.

During this procedure, a doctor removes the tumor that secretes excessive amounts of insulin.

After a clear diagnosis of insulinoma, doctors often do a partial pancreatectomy that not only removes the malignant tumor but that also takes away surrounding diseased tissue.

The affected tissue contains cells that could spread to other body parts. If this happens, it can result in liver disease or lymph node inflammation.

After surgical procedures, doctors often administer a dextrose solution intravenously to stabilize the insulin level of the hypoglycemic patient.

Your DVM will monitor your dog for ongoing complications such as:

dog diabetes mellitus
pancreatitis
neurological problems

Medical Treatment

Medical therapies are the industry’s least preferred method for treating dog insulinoma.

In most cases, medicines are prescribed for dog insulinoma when the disease has gone unaddressed for too long.

When this happens, simply removing a common pancreatic neuroendocrine tumor isn’t enough.

These dogs aren’t good candidates for surgery and are treated with medicines instead. Medical therapies are also used to treat dog insulinoma when the pet has persistent post-surgical hypoglycemia.

Pet owners and DVMs are wary of administering medical therapies because there are always drug side effects to consider.

The lowest survival rates for dog insulinoma are found with dogs that rely only on medical therapies.

Glossary of Common Terminology

When your dog is sick with insulinoma, you’ll likely hear a barrage of medical terminology of which you’re not familiar.

This quick cheat sheet of terms that are associated with dog insulinoma can help you to better understand the disease, its symptoms, and treatment options.

Amended Insulin Glucose Ratio

Amended Insulin Glucose Ratio (AIGR) is a calculation that’s performed to determine if your dog may have insulinoma.

The equation is calculated by multiplying serum insulin levels in micro U/mL by 100 and subtracting blood sugar levels in mg/dL from 30. Divide the serum insulin by the blood glucose number. If the AIGR is greater than 30, your dog likely has insulinoma.

Ataxia

Ataxia is a loss of coordination of muscle control.

Beta Cells

Beta cells are pancreatic cells that make, hold, and release insulin.

Blood Fructosamine Levels

Your dog’s blood fructosamine level is its average blood sugar level during a two to three-week timeframe.

Euglycemic

Euglycemic describes a normal amount of glucose in your dog’s blood.

Hypoglycemia

If your dog’s plasma glucose level is less than 60 mg/dL, then your veterinarian may diagnose it as having hypoglycemia.

Islet Cell Carcinoma

Islet cell carcinoma is a grouping of abnormal pancreatic cells that can be either benign or cancerous.

Islets of Langerhans

Islets of Langerhans are clusters of endocrine cells in the pancreas.

Metastatic

Metastatic means that malignant cells have spread from one location in the body to another.

Neoplasm

Neoplasm is another name for a tumor, which can be benign or malignant.

Pancreatectomy

Pancreatectomy is the removal of all or a portion of your dog’s pancreas.

Plasma Glucose Concentration

Plasma Glucose Concentration is the level of glucose in the blood measured in milligrams of glucose per 100 mL of blood.

Scintigraphy

Scintigraphy is a diagnostic scan that produces a picture based on detected radioactive substances.

Somatostatin

Somatostatin is a hormone that stops growth hormone activity.

Syncope

Syncope means to pass out or faint.

Surgical Resection

Surgery resection is the practice of removing a part of an organ or body part that contains diseased tissue.

Whipple’s Triad

Whipple’s Triad is a set of three indicators that your dog’s hypoglycemic symptoms stem from insulinoma.

Here are the three criteria.

Hypoglycemic symptoms
Low plasma glucose level
Symptoms subside when plasma glucose level increases

Life Expectancy of a Dog with Insulinoma

As a pet parent, you want to give your dog every chance to live a happy, healthy, and extended life even if he’s been diagnosed with insulinoma. However, the life expectancy of dogs that have insulinoma varies due to a number of factors.

Early Detection

Medical experts believe that the average survival time for dogs that have insulinoma can increase with early disease detection. Insulinoma symptoms can be either subtle or blatant.

When you suspect that your middle-aged dog is ill, be prepared to take him to a DVM for a physical examination and tell the doctor about his behaviors and symptoms.

When found early, insulinoma is characterized by a solid tumor that produces excess insulin. The tumor can be removed, and the dog treated to balance his blood sugars. Dog insulinoma is a metastatic disease, however.

If the condition isn’t properly addressed quickly, the tumor’s malignant cells can spread to your dog’s liver and lymph nodes, which significantly lowers his life expectancy.

When the disease is detected and treated early by a DVM oncologist, your dog can live for years after an insulinoma diagnosis.

Median Survival Time Based on Chosen Treatment

The median survival time for dogs that have insulinoma is greatly influenced by the chosen treatment option.

Early studies that were conducted during the 1990s show that dogs that underwent surgery for insulinoma lived a year after the procedure.

Those dogs that were subjected to medical management lived only 2.5 months after taking medications.

Davies, a London-based veterinary clinic, has been conducting its own research over the years. It found that dogs that undergo surgery in its clinics live 3.5 years or longer after the procedure.

Dogs that receive medical therapy live about 15 months after the therapy commences.

It’s unclear whether the dogs that undergo surgery are in better condition than those that take medicines. If this is the case, a dog’s initial condition is a significant factor in its longer life expectancy.

Post-Treatment Care

Post-procedure complications can lower your dog’s life expectancy if he has insulinoma.

That’s why it’s important to strictly follow your DVM’s instructions for post-treatment care. Many doctors stress getting the dog’s hypoglycemia under control before and after a surgical procedure.

He or she may recommend specific dietary restrictions and will more than likely prescribe multiple meals of small portions of food to keep your dog’s blood glucose levels stable during its recovery period.

Summary

Insulinoma is a somewhat rare disease, but when it strikes, it can deal a devastating blow to your dog in his twilight years. With the help of a skilled and caring DVM, you can take steps to find out if your dog is at risk for insulinoma and how to lower his chances of developing the ailment with proper long-term care.

References

https://www.yalemedicine.org/conditions/neoplasm

https://www.vin.com/apputil/content/defaultadv1.aspx?id=4252830&pid=11290&print=1