Diabetes mellitus occurs when the pancreas doesn't produce enough insulin. Insulin is required for the body to efficiently use sugars, fats and proteins.
Diabetes most commonly occurs in middle age to older dogs and cats, but occasionally occurs in young animals. When diabetes occurs in young animals, it is often genetic and may occur in related animals. Diabetes mellitus occurs more commonly in female dogs and in male cats.
Certain conditions predispose a dog or cat to developing diabetes. Animals that are overweight or those with inflammation of the pancreas are predisposed to developing diabetes. Some drugs can interfere with insulin, leading to diabetes. Glucocorticoids, which are cortisone-type drugs, and hormones used for heat control are drugs that are most likely to cause diabetes. These are commonly used drugs and only a small percentage of animals receiving these drugs develop diabetes after long term use.
The body needs insulin to use sugar, fat and protein from the diet for energy. Without insulin, sugar accumulates in the blood and spills into the urine. Sugar in the urine causes the pet to pass large amounts of urine and to drink lots of water. Levels of sugar in the brain control appetite. Without insulin, the brain becomes sugar deprived and the animal is constantly hungry, yet they may lose weight due to improper use of nutrients from the diet. Untreated diabetic pets are more likely to develop infections and commonly get bladder, kidney, or skin infections. Diabetic dogs, and rarely cats, can develop cataracts in the eyes. Cataracts are caused by the accumulation of water in the lens and can lead to blindness. Fat accumulates in the liver of animals with diabetes. Less common signs of diabetes are weakness or abnormal gait due to nerve or muscle dysfunction. There are two major forms of diabetes in the dog and cat: 1) uncomplicated diabetes and 2) diabetes with ketoacidosis. Pets with uncomplicated diabetes may have the signs just described but are not extremely ill. Diabetic pets with ketoacidosis are very ill and may be vomiting and depressed.
The diagnosis of diabetes is made by finding a large increase in blood sugar and a large amount of sugar in the urine. Animals, especially cats, stressed by having a blood sample drawn, can have a temporary increase in blood sugar, but there is no sugar in the urine. A blood screen of other organs is obtained to look for changes in the liver, kidney and pancreas. A urine sample may be cultured to look for infection of the kidneys or bladder. Diabetic patients with ketoacidosis may have an elevation of waste products that are normally removed by the kidneys.
The treatment is different for patients with uncomplicated diabetes and those with ketoacidosis. Ketoacidotic diabetics are treated with intravenous fluids and rapid acting insulin. This treatment is continued until the pet is no longer vomiting and is eating, then the treatment is the same as for uncomplicated diabetes.