Diabetes insipidus (DI) is a metaboic condition in dogs that causes a dog’s urine to be very dilute. The term “insipidus” means “tasetless” in Latin, and diabetes insipidus is different than diabetes mellitus (DM), in that is is caused by a decrease in vasopressin, the hormone that regulates the volume of water in the body. In contrast, diabetes mellitus is caused by a disruption of pancreatic function and the abnormal regulation of blood sugar. Althought DI is rare in dogs, it is important to know the signs and symptoms, and how it can be treated by your veterinarian.
What is Diabetes Insipidus?
As mentioned above, diabetes insipidus gets its name from the fact that the urine of these dogs is so dilute it is’tasteless.’ Diabetes insipidus is relatively rare in dogs, and is characterized by excessive thirst and drinking, as well as the production of extreme volumes of dilute urine. Some DI dogs produce so much urine that they eventually cannot control their bladders or urine output, and will have frequent accidents around the house.
Diabetes insipidus is a metabolic disorder caused by a reduction in the production of arginine vasopressin (AVP). AVP is a naturally-occuring, antidiuretic hormone in the body that regulates how water flows through the body and the kidneys. It also functions to maintain osmolatility, which is the concentration of salts, electrolytes, and glucose in a cell, and are responsible for maintaining the volume of water in the cell. What happens in DI is that the the cells cannot hold onto water because the hormone AVP is not working correctly, so these dogs essentially are losing water constantly. One of the strange things about this disease is that even if a dog drinks large amounts of water, excessive urination can cause dehydration and water loss.
What Causes Diabetes Insipidus?
There are three basic causes for DI, which include: 1) A defect in ADH, 2) a defect in the kidney’s response to ADH, or 3) or excessive water intake due to psychogenic or compulsive behavior. One of the main jobs of the kidneys is to filter blood that passes through them, and to regulate the balance of the body’s water by excreting or reabsorbing fluid as required. Re-absorption of water by the kidneys requires an adequate level ADH, which is produced by the pituitary gland in the brain. If ADH is not produced, or if the kidneys are not responding to it, the result will be DI. Diagnostic testing by a veterinarian can rule out one or more of the above causes.
What is the Difference Between Diabetes Mellitus and Diabetes Insipidus?
Diabetes mellitus (DM), also known as “sugar diabetes” is a result of an abnormal function of the pancreas, the organ that regulates the body’s gluciose levels by producing insulin. In dogs with DM, the pancreas is not producing insulin, so that blood sugar levels become elevated. results from a disruption of pancreas function and abnormal regulation of blood sugar. The urine or diabetic dogs is typically “sweet” due to high amounts of sugar excreted from the body. DM in dogs can be treated with insulin therapy and diet.
Unlike DM, diabetes insipidus is a result of an inadequate production of the hormone vasopressin, or ADH. In dogs with DI, the pancreas functions normally to regulate blood sugar levels. The first symptoms owners notice is increased urination (polyuria) and thirst (polydipsia), or “pu/pd” as veterianrians call it.
What are the Symptoms of Diabetes Insipidus?
There are several symptoms of diabetes insipidus in dogs, and some may mimic other conditions such as renal insufficiency or diabetes, so it’s always best to consult your veterinarian before jumping to conclusions. Signs and symptoms inlcude:
- Increased thirst (polydipsia).
- Increased uriune production (polyuria). This is also a symptoms of Cushing’s disease and diabetes in dogs, so proper diagnostics are needed for an accurate diagnosis.
- Increased production of very dilute urine in dogs.
- Weight loss and inappetance.
- Incontinence as a result of increased urine production.
How Is Diabetes Insipidus Diagnosed?
The first step in making a diagnosis is to conduct diagnostic testing, collecting a thorough medical history, and performing a physical examination on your dog. Diabetes insipidus lab tests include a blood chemistry panel to evaluate organ function and electrolytes, a complete blood cell count (CBC) to evaluate red blood cells, white blood cells and platelets, and a urinalysis. These tests are done to rule out other diesase processes such as DM, kidney disease, kidney infection and other medical conditions.
If your veterianrian suspects DI, additional testing will be recommended, including additional blood tests to measure ADH blood levels. Your veterinarian may also conduct a a urine-protein creatinine test to measure if protein is being lost through the kidneys. In some cases a veterinarians may recommend a desmopressin (a synthetic form of ADH) stimulation test to evaluate how the dog responds to an ADH replacement,as well as a water deprivation test to determine if the signs are caused by excessive water intake, a defect in ADH, or a defect in the kidney’s response to ADH. Measuring pituitary hormone blood levels and an MRI (Magnetic Resonance Imaging) scan may also be recommended.
How is Diabetes Insipidus Treated?
Although there is no cure for diabetes insipidus, there are diabetes insipidus drugs which are synthetic ADH substitutes. Some of these substitutes come in the form of injectibles or pills, and others can be administered as drops into the nose or eyes. Veterinarians also suggest a low-sodium diet as well. As with diabetic dog life expectancy, diabetes insipidus life expectancy can be normal with treatment.
With treatment, dogs with DI can live a normal life, and enjoy relatively normal routines. If left untreated, the prognosis is poor. DI can eventually lead to severe dehydration, coma and even death. For those owners who choose not to treat, and offer supportive care, unrestricted access to water should be provided at all times, and owners should be prepared for frequent urination and the possibility of accidents.
- Can Diabetes Insipidus be cured?
As mentioned above, there is no cure for DI in dogs, but the disease can be managed with synthetic ADH medication. As with diabetes mellitus, diabetes insipidus can be successfully controlled with the daily administration of medication. You and your veterinarian can decide which forms of synthetic ADH would work best for you and your dog.