Canine insulinoma is a tumor that affects the endocrine pancreas. Specifically, it is a neoplasm that involves pancreatic beta cells, which produce an excessive and sustained release of insulin, which in turn causes a decrease in blood glucose levels. Although both benign and malignant proliferations can be found, unfortunately in the canine species malignant forms (carcinomas) are more frequent.
If you want to know more about insulinoma in dogs, don't miss the following article on our site in which we detail thesymptoms, causes and treatment of this tumor disease.
What is an insulinoma in dogs?
Before defining what an insulinoma is, it is important that we explain the structure and function of the organ that is affected by this pathology: the pancreas. The pancreas is a gland that is made up of two parts, each of which has a specific function:
- The exocrine pancreas: is related to the digestive system, since it secretes pancreatic juice, necessary for the digestion of food.
- The endocrine pancreas: contains the so-called islets of Langerhans, which in turn are made up of alpha cells (glucagon-secreting), beta cells (insulin-secreting) and delta cells (somatostatin-secreting). In other words, it is related to the endocrine system, specifically, to the hormonal system that regulates blood glucose levels.
Once the structure and function of the pancreas are known, we can proceed to explain what this pathology consists of. Canine insulinoma is a tumor of the pancreatic beta cells, that is, of the cells responsible for the production of insulin. Insulin is a hormone that is released in response to the presence of glucose in the blood and allows glucose to enter cells to be used as an energy source. In insulinoma, the tumor cells produce a excessive and permanent secretion of insulin, which leads the animals to remain continuously in a state ofhypoglycemia (low blood glucose levels).
Within the insulinoma, we can find benign (adenoma) and malignant (carcinoma) proliferationsPancreatic carcinomas have a high mortality rate and often metastasize to the mesentery, liver, spleen and regional lymph nodes, although fortunately they are rare tumors in the canine species.
Canine insulinoma usually appears in dogs between the ages of 3 and 14, although they are more frequent in older ages (from 9 years). There is no sexual predisposition, but there is a racial predisposition, with a higher incidence in the German shepherd, the golden retriever, the poodle, the Irish setter, the fox terrier and the boxer.
Symptoms of insulinoma in dogs
The clinical signs associated with canine insulinoma occur as a result of sustained hypoglycemia and stimulation of the sympathetic adrenal system. Specifically, in dogs with insulinoma it can be observed:
- Weakness and lethargy: due to glucose deficit in the central nervous system.
- Abnormal behaviors, nervousness.
- Posterior third weakness, muscle cramps and fasciculations.
- Collapse.
- Ataxia (incoordination).
- Convulsive crisis.
Other less frequent clinical signs that can be detected in these patients are: polyuria and/or polydipsia, polyphagia, anorexia, weight gain, diarrhoea, syncope, head tilt, urinary incontinence and blindness.
Causes of insulinoma in dogs
The exact etiology of insulinoma in dogs is unknown Like all neoplasms, insulinoma is caused by a genetic alteration that gives rise to disorganized cell proliferation. However, the specific cause that triggers this genetic alteration is unknown.
Diagnosis of insulinoma in dogs
The diagnosis of canine insulinoma should be based on the following points:
- Medical history and physical examination: As we have already pointed out, dogs with this pathology present clinical signs fundamentally associated with sustained hypoglycaemia.
- Blood analysis (complete blood count and biochemistry): the most indicative parameter of canine insulinoma is the detection of a state offasting hypoglycaemia (values less than 60 mg/dl), which is due to excessive production of insulin by tumor cells. However, to confirm hypoglycemia, an isolated determination is not enough, but it is necessary to make a curve with measurements every hour, throughout an 8-hour fasting period.
- Histopathological analysis: is performed once the tumor has been removed and confirms the diagnosis. Microscopically, pancreatic cell neoplasms are made up of well-differentiated cells, with few mitoses but great facility for metastasizing.
Treatment of insulinoma in dogs
Is insulinoma in dogs curable? In some cases it is possible to remove it completely, however in others the result is not the desired one. There are two possible treatments for insulinoma in dogs, which are established according to the age and general condition of the patient.
Surgical treatment
The goal of the surgery is to remove the pancreatic tumor (totally or, when this is not possible, partially)and remove possible metastases present in the mesentery, liver or lymph nodes.
Surgical treatment is recommended, since although it is only possible to perform a partial removal, the symptoms will subside for a variable period of time (from months to a little over a year) and will help the success of the medical therapy. However, surgery is not recommended in critically ill patients, due to anesthetic risks.
Although surgery is the treatment of choice in all stable patients, it should be taken into account that a series of postoperative complications may appear:
- Pancreatitis: due to handling of the pancreas during surgery. To prevent its appearance, gentle management of the pancreas must be performed during surgery, establishing adequate fluid therapy before, during and after the operation, and administering adequate postoperative nutrition.
- Diabetes mellitus: When the tumor is removed, the pancreas may not be able to synthesize enough insulin because the rest of the beta cells are atrophied. In these cases, exogenous insulin should be administered until the pancreas regains its functional ability to produce insulin.
- Sustained hypoglycemia: occurs when there are metastases that continue to produce insulin. In these cases, additional medical treatment is required.
Medical treatment
Medical treatment will be necessary both in dogs in which surgery is contraindicated, and in dogs in which incomplete removal of the tumor has been performed. In turn, within medical treatment we distinguish two situations:
- Treatment of acute hypoglycemic crisis: it is an emergency situation in which the animals suffer a convulsive crisis. In these cases, caregivers must be aware and act quickly, rubbing a sugary solution (such as jam or honey) into the oral cavity The oral mucosa has the ability to to rapidly absorb the glucose contained in these foods, thus resolving the convulsive crisis in about 30-120 seconds.
- Treatment of chronic or sustained hypoglycaemia: the objective of this part of the treatment is to palliate the symptoms derived from hypoglycaemia and prevent occurrence of acute crises. Chemotherapy protocols should not be used, since they all cause serious side effects. Therefore, medical treatment should only be aimed at increasing glucose absorption in the intestine and decreasing insulin secretion. Specifically, a dietary treatment should be carried out with frequent meals, avoiding periods of prolonged fasting. A combination of dry and wet food is recommended, along with very light exercise. Pharmacological treatment should be added to dietary treatment, with glucocorticoids or diazoxide.
Prognosis of Insulinoma in Dogs
Unfortunately the prognosis for canine insulinoma is guarded to poor, since most of these tumors are malignant.
The life expectancy of dogs with insulinoma depends on the treatment that is instituted:
- In dogs receiving medical treatment only: life expectancy is 12 months.
- In dogs undergoing surgical treatment: one third die from intra- or postoperative complications, another third live less than 6 months, and the remaining third may have a life expectancy of 12 to 14 months.
