Polydipsia

Pet Tales
by Barry B. Burtis D.V.M.


Water for Elephants, by Sara Gruen, is a novel and a soon-to-be released movie about the adventures of a young man who interrupts his studies in veterinary medicine to work in a circus. It's this year's One Book One Burlington selection by the Burlington Public Library as a recommended book for our community to read - but, more about that later. The book title, of course, comes from one of the more onerous tasks associated with caring for circus animals - carrying water to quench the thirst of elephants. I enjoyed the book, but while reading it, I began to wonder how frequently elephants suffer from polydipsia. It's a condition that would make an already tiresome chore even more exhausting. Polydipsia, or increased thirst, affects dogs, cats and other pets. It should always be reported to your veterinarian if you notice it happening with your pet.


If a dog is drinking more than 100 ml. per kilogram of their body weight per day, it is considered to have polydipsia. A cat is demonstrating greater than normal water consumption if it drinks more than 50 ml. per kilogram of its body weight, per day. Veterinarians sometimes ask owners to measure a pet's intake of water over a 24 or 48 hour period, in order to determine if there truly is an abnormal intake of fluid.


Water intake and urine production are controlled by interactions between the kidneys, and the pituitary gland and the hypothalamus in the brain. Thirst and urine production are also influenced by volume receptors in the blood circulatory system. In most cases increased thirst is a compensating mechanism when for some reason polyuria (increased urine production) occurs. Occasionally, however, polydipsia is the primary process and polyuria is the compensating response.


At any rate, in most cases polydipsia and polyuria (PD/PU) occur together in an affected pet. It is a common problem in the cat, but it's even more common in dogs. The three major causes of PD/PU in the cat are kidney disease, diabetes and hyperthyroidism. Hyperthyroidism is much less commonly a problem in dogs, but the other two disorders affect dogs, as well. In addition, there is a long list of other causes of PD/PU that more frequently affect dogs than cats. Primary polydipsia can be caused by behaviour problems, fever, pain or disease that is caused by cancer, trauma or inflammation affecting the thirst center in the hypothalamus of the brain.


Once the problem of PD/PU is confirmed to exist, it becomes necessary to work toward a definitive diagnosis and determine the specific cause in an affected pet. Laboratory testing on blood and urine can provide confirming evidence and will likely be the most helpful tool in making a diagnosis. However, imaging - x-rays or ultrasound studies - are frequently used as a diagnostic aid. Treatment of PD/PU disorders, of course, will depend on properly identifying the cause of the problem. As with many diseases that cause illness for our pets, successful treatment is often greatly influenced by early detection. Careful observation of your pet's daily habits, including how much water they drink, is one of the most important things an owner can do to ensure their pet stays healthy.


Well, back to those elephants for a moment. There's no mention in Water for Elephants of any of those in the book suffering from polydipsia, thank goodness. However, in what they call "an event that salutes animal doctors everywhere",  and as a kickoff for the lineup of programs and special events related to this years One Book One Burlington selection, the Burlington Public Library has asked me to talk a bit about my career as a veterinarian. I never ran away to care for circus animals nor have I carried any water to elephants, but I do have some interesting stories from over the years, as a member of my profession. I feel honoured to have the opportunity to share some of these reminiscences with those in attendance at Centennial Hall, Burlington Central Library, 7-9 p.m. on Wednesday, September 29, 2010. It's a free ticketed event and tickets can be picked up at the Central Library. I hope some of you will be able to attend. Barry Burtis is a local companion animal veterinarian. Past Pet Tales can be found at www.baycitiesanimalhospital.ca