Canine Diabetes Mellitus

The disease is a result of insufficient insulin production from the pancreas. Beta islet cells in the pancreas which are responsible for the production of insulin are destroyed over time. There are probably many reasons for beta islet cell destruction and subsequent hypoinsulinemia (low blood insulin). Known causes include diseases stressing the pancreas: pancreatitis, Cushingís, acromegaly and progesterone drugs. Clearly some individuals are genetically predisposed to the disease but there is no breed predilection. It is also believed that infection and chronic small bowel inflammation may induce DM.

The disease is a result of an increase in blood glucose that would normally be distributed to the various tissues for energy in cell metabolism. Insulin is not available to force glucose from the blood into the tissues. As glucose levels increase, blood starved cells turn to other chemicals for energy.

Additionally, because glucose remains high in the blood the appetite center in the brain remains unsatisfied and continues to drive the hunger response and the incorrectly perceived need for more glucose. Fat and muscle are broken down in an attempt to satisfy this false need for more glucose.

These metabolic events lead to a history of a very hungry animal that eventually starts to lose weight. Increased blood glucose will also result in overwhelming the kidneysí ability to conserve glucose, allowing glucose to spill into the urine. As glucose exceeds the kidney threshold (glucosuria) increased urination follows. Many dogs are presented with a history of increased eating (polyphagia), urinating (polyuria) and drinking (polydypsia).

A common sequelae to DM in the dog is the sudden development of cataracts and blindness. DM allowed to proceed unchecked will result in dangerous changes in blood pH and chemistries (diabetic ketoacidosis). The final outcome leads to vomiting, weakness, depression, coma and death. Most dogs are brought to their veterinarians long before these changes occur because owners are disturbed by the tremendous increase in urinating and drinking.

DM is a relatively easy diagnosis. However, it is very important to insure there are no other abnormalities that may be causing the diabetes or may make control difficult. A standard data base that includes a physical exam, an evaluation of blood cell demographics, blood chemistries and an urinalysis is usually sufficient to rule in DM and rule out other problems. A fasting blood glucose greater than 250 mg% (hyperglycemia), with a history of polyphagia, polyuria, and polydypsia, and the absence of other findings is usually diagnostic.

Therapy for the complicated advanced diabetic ketoacidotic patient cannot be discussed in the confines of this article. Therapy for the non ketoacidotic patient includes strict diet change and glucose lowering agents. Diet management revolves around minimizing large changes in blood glucose levels. This is best done by controlling weight and controlling the quality of the diet.

Diets containing complex carbohydrates are best at controlling changes in blood glucose. In addition, diets high in fiber decrease the rate of glucose absorption from the intestine and therefore minimizes major fluctuations of blood glucose after meals. Dividing meals into two feedings can also help control these changes. Common diets employed by veterinarians include HillísÆ prescription diet W/D and HillísÆ Science Diet, Maintenance Light. Other diets include PurinaÆ Fit and Trim and GainesÆ Cycle 3 Light.

Glucose lowering agents include insulin and oral glucose lowering agents (hypoglycemics). Oral hypoglycemics are dependent on the patient having some viable beta islets cells. These drugs act to stimulate the insulin production from the pancreas' beta islet cells and have been somewhat effective in the cat, but have not been very rewarding in the dog.

Insulin therapy is the drug of choice for the diabetic dog. Most owners are initially concerned about administering injections at home. However, most veterinarians experience relatively easy owner acceptance after the initial trial at home. Learning about diabetic paraphernalia is uncomplicated. Also, dogs are readily conditioned to injections that are reinforced with rewards of a meal.

There are different types of insulin that are derived from beef, pork and recombinant DNA human sources. The types of insulin are determined by duration of effect. They consist of regular (short acting), NPH and Lente (intermediate acting) and PZI and Ultralente (long acting). The choice of insulin will depend on the patient's individual response to the different types. Mixing different acting insulins is not common. However, in some challenging patients it can be valuable. In the dog it is common to start with NPH at an initial dose of 1/4 unit per pound of body weight administered once or twice a day. It is also common to hospitalize the patient during the initial trial and perform serial blood glucoses to establish the maintenance dose.

Some owners are capable of beginning immediately at home and returning during the first few days for blood glucose checks. This latter method can work but it is often more cost effective to initiate insulin therapy in the hospital and monitor the glucose over the first few days.

Managing a diabetic dog over the long term includes occasional trips back to the veterinarian for blood glucose checks, annual physical exams and blood work to insure no complications. At home, owners should routinely monitor appetite, water intake and urination daily. If the owner is observing these criteria, a change in blood glucose will be apparent.

As mentioned before, diet should be controlled closely. A few owners will be able to learn to do blood glucose strips at home and make adjustments to insulin with a teleconference from the veterinarian. Some owners will find urine glucose monitoring easy. Urine glucose, however, is not sufficient to make blood glucose adjustments, but can help if the owner is concerned about adequate control. Fundamental to control is careful observation of eating, drinking and urination.

Complications to managing a diabetic dog include: hypoglycemia, insulin resistance, and rapid metabolism of insulin. The latter two require careful laboratory testing to confirm. Hypoglycemia is always a possibility and should be considered if behavior is changing. Common behavioral changes from hypoglycemia include hunger, confusion, lethargy and weakness. Owners should always have a jar of Karo syrup on hand to rub on to the gums of the dog if hypoglycemia is suspected. A call to the veterinarian is in order to reset the insulin level.

Diabetes mellitus is a life long disease that requires a commitment from the owner beyond normal pet care. This essential commitment is an ongoing process of monitoring several parameters, controlling diet, administering daily insulin, and a long term relationship with a veterinarian.

1/3/97

Veterinary Information Services

DISCLAIMER:

THIS ARTICLE IN NO WAY ESTABLISHES A CLIENT-VETERINARIAN RELATIONSHIP. THE INTENT OF THE ARTICLE IS TO COMPLEMENT THE USERíS CURRENT VETERINARY EDUCATION. NO CLAIMS ARE MADE AS TO CONTENT. THIS ARTICLE IN NO WAY REPLACES THE CLIENT-VETERINARIAN RELATIONSHIP.

Additional Points from:

Diabetes Mellitus, by Peter A. Graham BVMS, PhD, CertVR, MRCVS, May 1995, found on Canine Diabetes web pages at:

http://www.original1.com/diabetes/cdm.html

• Insulin is the treatment of choice for diabetes mellitus in animals. Insulin must be given by injection because it is a protein and would be digested in the intestine if it was given as a tablet.

• Unfortunately, there is no standard dose for insulin which can be applied to all animals. Each diabetic animal has to have its dose tailored to its individual needs which is done over a stabilization period. In order to achieve stable control of a diabetic animalís blood glucose by insulin, all the other factors which affect blood glucose concentration must be kept constant from day to day. These factors include the composition, volume and timing of meals and the amount of exercise the animal gets.

• Dogs which are off their food or need to be fasted as part of the management of vomiting or diarrhea need to continue to receive insulin, since withholding both food and insulin is likely to start the production of ketones and this will make the dog more unwell. Usually half of the dogís normal requirement will prevent ketoacidosis and will be safe.

• Ketoacidotic animals are usually collapsed, dehydrated and smell of ketones (like nail varnish remover). These dogs require more intensive therapy than normal diabetic dogs and this should include intravenous fluid and special soluble insulin therapy. Often the treatment of diabetic ketoacidosis is an intensive care situation.

Additional Points from:

Diabetes Mellitus in Dogs & Cats, by Richard W. Nelson DVM, and Edward C. Feldman, DVM, Diabetes Spectrum, Volume 5 Number 5 1992, found at:

http://www.diabetes.org/aÖbetes/cats&dogs.html

• Most of the catastrophic long-term human complications of diabetes are not observed in diabetic dogs and cats. The life span of these animals is probably not long enough for the complications to develop. Renal failure from glomerulosclerosis, blindness from diabetic retinopathy, and weakness from peripheral neuropathy have been documented, but are rare. Complications in dogs and cats usually result from inappropriate insulin therapy and include hypoglycemia from overdosage or persistent urination and thirst, weight loss, bacterial infections, and ketoacidosis from chronic underdosage.

• As can be appreciated by any health-care professional working with people who have diabetes, diabetic pets are a significant responsibility. Such dogs and cats transcend the common concept of "pet" and become true dependents. Owners rarely abandon diabetic pets. Rather, these people become vigilant caretakers who take tremendous pride in the management of their charge. They keep careful records of insulin dose, time of insulin administration, diet, urine glucose measurements, and general observations. The difficulty encountered managing a diabetic pet compares to human care ñ some individuals are easily treated while others prove quite difficult.

Note also: the DIABETES MONITOR: DIABETES on the WEB: Pets with Diabetes, which provides a master list of web sites. Find it at: http://www.mdcc.com/pets.htm

AND

Muffin ñ Diabetes Mail List, open for anyone who has a diabetic pet, and others with an interest in the topic.

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Disclaimer: Your veterinarian is the most qualified person to answer all of the questions you have about your pet's health. Nothing in this article should be construed as medical advice regarding any individual animalís condition.