Tending to the Diabetic Cat
Diabetes is a complicated condition caused by either an absolute or significant deficiency of insulin which results in hyperglycemia (elevated blood glucose levels) and glycosuria (glucose in the urine). Diabetes mellitus is most commonly found in older cats. Neutered cats male cats and obese cats are at an increased risk of developing this condition. Genetic predisposition to diabetes is well recognized in people and there has been increased evidence that genetics may play a role in the development of diabetes in cats as well. In fact the Burmese breed has been identified as being predisposed to diabetes and analysis of pedigrees has suggested that this is an inherited trait.
Normal Actions of Insulin
Insulin is produced by the pancreas which is a small organ located in the abdomen close to the stomach and the liver. Insulin is released into the bloodstream where it travels to all the tissues of the body. Its main role is to enable cells to take up glucose (sugar) which is needed as an energy source. Insulin also stimulates uptake of various other substances including amino acids (building blocks for proteins) fatty acids (needed for making cell membranes) potassium and magnesium by tissue cells. In the liver insulin has important roles which include production of glycogen (a carbohydrate energy store) and fat. Insulin also reduces the amount of glucose made and released by the liver.
In diabetic cats there is significant or total deficiency in insulin; resulting in impaired glucose uptake by tissue cells which causes hyperglycemia. As the cells are starved of glucose they switch to using fat and protein as an energy source. This is facilitated by breakdown of body stores of fat and protein resulting in weight loss and the accumulation of toxic waste products which can precipitate a diabetic crisis (ketoacidosis).
An absolute insulin deficiency may arise as a direct failure of the pancreas to produce insulin. However in most diabetic cats there is a combination of insufficient insulin secretion by the pancreas and what is known as peripheral insulin resistance. Peripheral insulin resistance describes the situation whereby cells of the body fail to respond to insulin as effectively as they should. Insulin resistance can be caused by a number of conditions including pregnancy obesity some drugs (e.g. corticosteroids such as prednisolone progestagens such as megoestrolacetate – ‘Ovarid') other hormonal conditions such as hyperadrenocorticism (tumor of the pituitary or adrenal gland resulting in excessive production of corticosteroids by the body) and acromegaly (a tumor producing excessive amounts of growth hormone).
In diabetic cats the hyperglycemia is so severe that glucose is excreted in the urine (glycosuria). Glucose takes water with it so an increased volume of urine is produced (polyuria - increased amount of urination). To compensate for this and so that dehydration is prevented the cat develops an increased thirst(compensatory polydipsia). Weight loss and a voracious appetite (polyphagia)are also frequently seen and these may be the original reasons for presentation to a veterinary surgeon. Therefore the main clinical signs seen in a diabetic cat are:
- Weight loss
- Increased appetite
- Increased drinking and urination
- These signs are not always present or may go unnoticed. For example the increased thirst may not be recognized if the cat is drinking from water sources outdoors while not noted to be drinking more in the home.
Other clinical signs which may be seen in diabetic cats include:
- Straining to pass urine and/or passing bloody urine associated with a bacterial urinary tract infection (bacterial cystitis)
- Enlargement of the liver evident on examination by a veterinary surgeon (hepatomegaly)
- Poor coat
In a small number of diabetics the nerves supplying the legs and in particular the hind legs may be affected resulting in a classic plantigrade stance (sunken hocks). This is caused by a peripheral neuropathy. Very rarely the eyes may be affected by cataracts and retinal abnormalities which develop associated with the diabetes. This can cause problems with vision including blindness in most severely affected cats. Systemic hypertension (high blood pressure) is a recognized potential complication of diabetes in people and has also been reported in a small number of diabetic cats.
Most diabetic cats will remain relatively healthy but ketoacidosis is a potential complication that can be seen in any uncontrolled diabetic. In this situation the cat may become extremely depressed with signs such as vomiting diarrhea complete loss of appetite dehydration collapse and coma. If any of these signs are seen in a diabetic cat it is cause for immediate concern and a veterinarian should be contacted as soon as possible.
Diabetes mellitus is suspected in cats showing the appropriate clinical signs but other diseases may also cause similar signs. For example other important causes of weight loss in an older cat including kidney disease cancer hyperthyroidism (overactive thyroid gland) and inflammatory bowel disease need to be ruled out.
Blood and urine tests are required to confirm a diagnosis of diabetes. Although hyperglycemia and glycosuria are found in diabetic cats cats can also suffer from a stress-associated hyperglycemia which can cause glycosuria and therefore confuse diagnosis. For this reason a single blood or urine sample cannot be considered as diagnostic of diabetes. One solution to this problem is for the cat's owner to collect a urine sample while the cat is in its non-stressful home environment.
Diabetes mellitus is usually a treatable condition and although it requires considerable dedication and commitment from owners it can be a very rewarding problem to manage.
Initial management may involve addressing factors which have precipitated or complicated the diabetes such as treating obesity or withdrawing drug therapy. If no predisposing causes of the diabetes can be identified or if correction of these do not lead to resolution of the diabetes then specific treatment is required.
Underweight diabetic cats may need energy dense diets until their weight normalizes. Obese diabetic cats should be put onto a weight loss regime under the guidance of a veterinary surgeon as obesity interferes with the way insulin works. In some of these cats this may resolve the diabetes.
Low carbohydrate diets have been advocated for diabetic cats and published case studies indicate that these diets can help to reduce the requirements for insulin and improve diabetic management. A variety of commercial pet food manufacturers produce prescription low carbohydrate diets suitable for use in diabetic cats. In non-obese diabetic cats dietary management is usually not sufficient on its own to manage the disease and further treatment (eg insulin oral medication) is needed.
It is recommended as far as possible to keep the diet constant both in terms of what is fed as well as timing of meals and so on. Altering the feeding regime may upset the stabilization of the diabetes.
In a small number of cats it is possible to stabilize their diabetes using oral medications. Experience would suggest that this treatment is most effective in mildly affected cats and obese cats where insulin resistance is present. Other oral agents are also available and may be recommended in some diabetic cats.
In most diabetic cats insulin therapy is the most effective treatment. Insulin is given by an injection under the skin of the scruff and most cats will be stabilized on a regime involving either once or twice daily injection. The exact site of administration should be changed on a daily basis to reduce any scarring or reaction at the injection site which may limit insulin absorption. Special insulin syringes with very fine needles are used so that the cat will hardly feel the injection. Veterinarians often recommend that diabetic cats are offered food just before they receive their insulin so that the cat is distracted by eating and does not notice the injection. It is important that the insulin is given at the same time(s) every day as directed.
The long-term outlook for cats with diabetes mellitus varies according to how old they are how easy it is to stabilize their diabetes whether they have any other diseases and the severity of them. In one study the average survival time for diabetic cats was around 2 years. Many diabetic cats have an excellent quality of life and are extremely rewarding cases to treat.