Diabetes Mellitus in Dogs and Cats

What Is Diabetes Mellitus?

Diabetes mellitus is an illness caused by the body’s inability to either make or use insulin, which is a hormone produced and released by specialized cells in the pancreas. Insulin permits the body’s cells to take sugar (glucose) from the blood and use it for their metabolism and other functions. Diabetes mellitus develops when the pancreas doesn't make enough insulin or when the body’s cells are unable to use available insulin to take glucose from the blood. It is generally common in dogs and cats that are over 6 years old. It is rare in young dogs. The condition is commonly divided into two types, depending on the origin of the condition: Type 1 diabetes, sometimes called "juvenile diabetes", caused by destruction of the beta cells of the pancreas. This condition is also referred to as Insulin-Dependent diabetes, meaning exogenous insulin injections must replace the insulin the pancreas is no longer capable of producing for the body's needs. Insulin-Dependent Diabetes mellitus, or Type 1 diabetes is more common in dogs than in cats and usually there is no possibility the permanently damaged pancreatic beta cells could re-activate. 

The primary type of diabetes in cats is Type 2 Diabetes Mellitus. There is another less common form of diabetes, Diabetes insipidus, which is a condition of insufficient antidiuretic hormone or resistance to it. 

This most common form of diabetes strikes 1 in 500 dogs. The condition is treatable, and need not shorten the animal's life span or interfere with quality of life. If left untreated, the condition can lead to cataracts, increasing weakness in the legs (neuropathy), malnutrition, ketoacidosis, dehydration, and death. Diabetes mainly affects middle-aged and older dogs, but there are also juvenile cases. The typical canine diabetes patient is middle-aged, female, and overweight at diagnosis. The number of dogs diagnosed with diabetes mellitus has increased three-fold in the last thirty years 

                                                       

Illustration of a dog's pancreas. Cell-islet in the illustration refers to a pancreatic cell in the Islets of Langerhans, which contain insulin-producing beta cells and other endocrine related cells. Permanent damage to these beta cells results in Type 1, or insulin-dependent diabetes, for which exogenousinsulin replacement therapy is the only answer 

Clinical signs 

Hepatomegaly, muscle wasting.
Bacterial infections (urinary tract, respiratory tract).
Cataract , retinopathy (rare).
Peripheral neuropathy.
Glomerulosclerosis (rare).
Cutaneous xanthomata, ulcerative dermatosis.
Ketoacidosis 

• Depression. 
• Tachypnea. 
• Acute onset vomiting. 
• Abdominal pain (due to pancreatitis). 
• Abdominal distension. 
• Slow deep breathing (Kussmaul respiration). 
• Profound dehydration. 
• Smell of acetone on breath. 
• Hypothermia. 
• Slow capillary refill time. 
• Coma. 

Hyperosmolar coma 

• Weakness. 
• Lethargy. 
• Coma. 

Differential diagnosis 

Other causes of polydipsia 

• Hyperadenocorticism . 
• Renal disease . 
• Hyperosmolar diabetes mellitus . 
• Hepatic disease . 
• Neoplasia. 
• Hypercalcaemia . 
• Diabetes insipidus . 
• Psychogenic polydipsia . 

How Is Diabetes Diagnosed?

A dog is suspected to have diabetes if any suspicious clinical signs, such as increased drinking and/or urinating, have been observed. After a thorough physical examination, some tests are recommend to help confirm a diagnosis. These include:- 

CBC (complete blood count) and chemistry profile: These tests are commonly performed together during initial blood testing to provide information about the pet’s organ systems. The CBC and chemistry profile may show dehydration, an elevated blood sugar level, or other changes that can occur with diabetes. 

Urinalysis: Evaluation of a urine sample may show the presence of sugar (glucose) in the urine if a dog has diabetes. 

Fructosamine: Fructosamine is a protein in the blood that binds very securely to glucose. The fructosamine level is therefore a close estimation of the blood glucose level, but it is less likely to change due to stress and other factors that affect the blood glucose level. Additionally, the fructosamine level indicates where the blood sugar levels have been during the previous 2 to 3 weeks. In a dog with diabetes, the blood sugar levels are usually high for long periods of time, which would be reflected by an increased fructosamine level. 

How Is Diabetes Treated?

Dogs tend to have type 1 diabetes mellitus, therefore insulin injections are generally started at diagnosis and continued for the rest of the pet’s life. It is also recommended that dietary changes are made to help control the dog’s diabetes. A medication schedule for the pet should be maintained on the calendar, including the date and time that the medication needs to be administered, and to maintain accurate records. This will avoid forgetting to give insulin to the pet and allows tracking the pet’s treatment.

Dietary Control

Insulin therapy provides the mainstay of treatment for most diabetic patients but management of other factors such as diet and exercise can influence glycaemic control.

Since almost all diabetic dogs have insulin-dependent diabetes mellitus (IDDM) dietary management will not remove the requirement for insulin. The aim of dietary change is to improve glycaemic regulation. A diet must provide all the nutritional needs of patients and should minimize post-prandial fluctuation in glucose concentrations. 

The essential features of dietary management of a diabetic are that the diet should be:

• Consistent from day to day (to prevent unnecessary alterations in insulin requirement). 
• High in complex carbohydrates so that glucose is released in a steady fashion from the gut. 
• Given so that glucose absorption from the gut coincides with peak action of administered insulin. 
• Of the correct calorific value to take diabetics weight to optimal weight. 
• Fat restricted. 

There are a number of prescription diets which have been specially formulated for the management of diabetic patients. These can be particularly useful for achieving weight loss in obese patients. However most diabetic dogs can be stabilized on a carefully controlled program using their normal diet.

After treatment begins, periodic blood and urine tests are generally recommended. This helps ensure that the insulin dosage is right for the dog. The pet's weight, appetite, drinking and urination, and attitude at home can all provide useful information that helps determine if his or her diabetes is being well managed. All of these factors are considered when making recommendations for continued management.

Many dogs live active, happy lives once their diabetes is well regulated. However, insulin therapy and regular monitoring at home and by the veterinarian are necessary for the rest of the pet's life.