Diabetes mellitus is a serious disorder caused by an insulin deficiency. Insulin is a hormone produced by the pancreas that is secreted into the blood after eating. Its roles are twofold: to promote the storage of glucose, as ready to use glycogen and for later use as fat, and to stop glucose formation from stored body fats; and to promote the uptake of amino acids and the manufacture of these into proteins.
There are two types of diabetes mellitus. Type I, also called insulin dependent diabetes, is caused by very low or absent insulin secretion. Patients with Type I diabetes will die if not treated with insulin. Type II, or non insulin dependent diabetes, is caused by inadequate or delayed insulin secretion relative to the needs of the patient. Many of these patients live without insulin treatment. Type II diabetes is by far the more common.
Diabetes mellitus affects both cats and dogs. The disease can be caused by infection or inflammation of the pancreas, by genetic causes, immune system attack of the pancreas, as a by-product of other diseases, and, rarely, as a side effect of some drugs. Obesity vastly increases the risk of your pet contracting diabetes.
In Australia, vets are seeing more and more cases of Type II diabetes. This is mirroring the experience of our colleagues in human medicine, and probably for much the same reasons — just like us, our pets are becoming fatter and more sedentary than ever before.
Diabetes mellitus is usually first seen in middle age (4-14 years) in cats and dogs. Diabetic pets usually eat a lot but lose weight, drink a lot and urinate a lot. Cataracts develop quite rapidly in dogs with poorly controlled diabetes, leading to blindness.
As the untreated disease progresses, pets develop ketoacidosis and become very sick, developing anorexia, vomiting, weakness and lethargy. At this stage the diabetes has become a serious life threatening illness.
How is diabetes diagnosed?
Diagnosis of diabetes mellitus involves measuring glucose levels in urine and blood. A full urinalysis and blood screen is performed to diagnose the diabetes, assess the severity of the disease, look for underlying causes of diabetes and to examine for secondary problems associated with the diabetes, for example, urinary tract infections.
Treatment of pets with uncomplicated diabetes involves dietary changes, the use of injected insulin, and regular monitoring of blood glucose levels in the hospital. Where required, insulin therapy is lifelong for most patients, and can involve once or twice daily injections (administered by the owner — we teach you how to do this). Some cats can be managed with oral medication rather than insulin.
Soft, moist foods are avoided. Pets that are not overweight are fed a diet they will reliably eat that has a constant calorie content. Overweight pets are fed on special weight reducing diets.
The ideal diet is high in fibre as this helps stabilise blood glucose levels, and will be low in fat and high in complex carbohydrates. Set feeding times and amounts are determined for your pet and are fixed in relation to insulin injection times. Exercise levels for your pet need to be kept consistent or will interfere with the stability of your pet’s blood glucose levels.
Initial stabilisation on insulin therapy requires day hospitalisation and the taking of blood glucose levels throughout the day. This may need to be repeated every few weeks until things are stabilised, then every few months or whenever a problem arises.
At home monitoring involves assessing levels of drinking and urinating, eating and body weight.
Hypoglycaemia, or low blood glucose, can occur if too much insulin is given or if your pet doesn’t eat normally or uses more glucose than usual, for example, through excessive exercise. The most obvious sign of this is weakness or lethargy, which will improve rapidly if a readily absorbed glucose source such as honey is given. Left untreated hypoglycaemia can result in coma or death.
Ketoacidotic patients — the really sick ones — need hospitalisation and intensive treatment with intravenous fluids and medication to get them past this life threatening stage. These patients are harder to initially stabilise on insulin, but once past this are treated in the same way as uncomplicated diabetic patients.
Entire females should be speyed when stable, as cycling makes management of their diabetes difficult, and pregnancy is strongly recommended against, it is difficult to maintain and can cause many problems for the mum.