PET PROBLEMS ASSOCIATED WITH POLYURIA AND POLYDIPSIA (PU/PD)

01/05/19

 

Written by: Dr. Chip Coombs

Noticing that your pet is drinking more (polydipsia) is not generally a good clinical sign. In a household with more than one pet, it may not be easy to determine who is the one responsible for draining the water bowl, particularly in the earlier stages of the excess drinking. Naturally, when more fluid is consumed, there will be the consequence of having to urinate more often (polyuria) and in some cases, it may be the increased urination that catches an owner’s attention. In advanced cases, this excessive urination may even be manifested in the form of accidents inside the house by a pet that is normally a ‘camel’ and would rarely have such an accident.

When an owner first appreciates that their pet is drinking more, either a cat or dog, they might think it is merely due to the house being dry in the winter, or the days being hot during the summer. Indeed, these environmental conditions will tend to push a pet towards dehydration, and they will drink more to compensate. A rough guideline to use to determine how much a pet would normally drink in a day is less than 40 cc/lb. for a dog, and 20 cc/lb. of body weight for a cat. If you have just one pet, this will be an easy determination. Fill the water bowl in the morning with a measured amount of water, and 24 hours later measure what is left. If the water level is getting low, keep adding measured amounts to make sure your pet has access to all the water they want. In the case of having more than one pet, an owner is best to keep the pets separated for the 24-hour measuring period. This way, each pet has their own water bowl and is isolated from any other water bowl. And, if you have a large dog, make sure the toilet lid is closed!

Presuming that your pet is consuming more than they should, is it a reason for alarm? Perhaps not alarm, but excessive drinking is usually an early sign of something amiss and you should discuss it with your veterinarian. Before doing any diagnostic tests, there will be a number of potential issues being considered by your veterinarian and which ones could come into play will depend upon other signs that your pet may have, as well as species and age. Pets who are elderly, losing weight, eating poorly or having a ravenous appetite would be exhibiting some of the other many clinical signs that could accompany the excessive drinking.

What type of problems might your pet have?

Diabetes mellitus (DM), aka sugar/ insulin diabetes, would be one consideration, especially if your pet is an overweight feline. However, dogs get diabetes mellitus as well, and can also get another type called diabetes insipidus (DI). DI is a complex problem involving the brain and kidneys, completely unrelated to DM, and is fortunately very uncommon.

Kidney problems are another common consideration and can affect any pet, of any age. In younger pets, one would have to consider if they were born with kidney issues or if they were exposed to a kidney toxin. For example, antifreeze is toxic to all pets, and lilies are especially so to cats. In older pets, it is common for the kidneys to slowly begin to fail simply because of their age. With cats specifically, 75% of them will eventually die with some form of kidney failure.

Thyroid problems, either a thyroid gland being overactive (hyperthyroid) in cats or underactive in dogs (hypothyroid) are also commonly found. Again, there are usually other clinical signs such as weight loss and increased appetite in cats, or hair loss, poor hair coat and weight gain in dogs.

In dogs, a problem, that was once relatively uncommon, called Cushing’s disease, has become far more common in recent decades. It usually originates from a benign tumor, either in the brain or an adrenal gland (small hormonal gland next to the kidney), which produces excessive amounts of a hormone called glucocorticoid and resultant polydipsia. Fortunately, newer drugs make this a very treatable disease with a near-normal life expectancy, if caught early. In some cases, Cushing’s disease is complicated by having diabetes mellitus at the same time. However, in spite of this complication, the prognosis is still quite good.

Although these are the more common causes of polydipsia, there are other, less common issues such as liver problems in both dogs and cats. There are also behavioural problems in dogs, such as boredom (psychogenic polydipsia), some forms of cancer, as well as certain drugs (such as steroids, like prednisone). Although your veterinarian may have a suspicion of what might be causing the excessive drinking, diagnostic blood and urine tests are absolutely essential to narrow the problem down to help determine a successful treatment. Finding sugar in a urine sample alone would likely indicate diabetes. However, without the bloodwork to rule out a complication of Cushing’s or an underlying infection, your dog would likely never be successfully treated, or have their diabetes controlled.

As mentioned, what goes in, must come out and excessive water consumption naturally produces excessive urination. Although excessive drinking can be, and often is, the primary problem / clinical sign, it may actually be the result of excessive urination. In other words, what goes out, must be replaced. If your dog or cat has a urinary tract problem (bladder infection) that causes them to urinate frequently, then there will be a consequential increase in water consumption to compensate. In most cases of true polydipsia, the water consumption will be above (or well above) the 30 cc/lb. body weight, whereas with a lower urinary tract problem, the water consumption might be elevated, but not nearly as much.

If you think your pet is drinking excessively, have the issue checked out by your veterinarian. The sooner an existing problem is recognized and treated, the more likely there will be a successful treatment outcome.

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