With all the hot weather we’ve had recently, you may notice that your pet is drinking more water than normal… this likely is just par for the course, but when should you be concerned? How much is too much?
Polydipsia is the medical term for increased thirst, and polyuria the term for increased urination. It is often very difficult at the onset to know whether the problem lies primarily with increased thirst (increased thirst drives the increased urine volume) or increased urination (increased urine volume drives increased thirst, as urine is not being concentrated effectively); problems that lead to increased urination tend to be more common causes in both dogs and cats. The symptoms of polyuria and polydipsia are frequent causes for veterinary visits; often it is urinary accidents or inappropriate urination that may finally bring the problem to light, as quantifying thirst and/or urination can be quite tricky at home, especially if there are multiple pets in the household.
Some of the more common reasons for increased thirst include behavioral issues (“psychogenic polydipsia” - i.e. drinking for “fun”), fever, pain, or neurological disorders. Increased urination can be caused by something as simple as a urinary tract infection or as complex as: electrolyte abnormalities, diabetes mellitus (insulin-dependent diabetes), kidney insufficiency or failure, liver disease, elevated thyroid level, drugs (such as the common corticosteroid prednisone, or the anti-seizure medication phenobarbital), infection of the uterus, or abnormalities of the body’s resting steroid levels (Cushing’s disease and Addison’s disease).
When a patient initially presents for the complaint of increased thirst and/or urination, the first step is to verify that there is, in fact, increased thirst or urination. The diagnostic work-up is started with a physical exam and thorough history to determine if there are any other factors that may be contributing to the symptoms. We then often have the owner quantify the water intake over a several days period (which is much easier in a single dog or cat household), in addition to running a urinalysis to determine how well the urine is concentrated. One of the most basic tests that can be run is to check the concentration of a first morning urine sample (often the most concentrated sample of the day) – if it is dilute then we know there is an issue and additional work up is warranted. Blood work is often part of the initial work-up as well, as we can assess kidney and liver function, and rule out conditions such as kidney failure or diabetes as well as to give clues about other metabolic disorders that would necessitate further investigation.
As mentioned above, quantifying thirst and especially urination may be difficult; but, since they go hand-in-hand the majority of the time, quantifying thirst is a bit more straight-forward and is a good starting point. Normal water consumption can be very variable, but averages around 50-60 mL/kg/day for both cats and dogs (i.e. 4-¾ to 5-¾ cups per day for a 50 pound dog). Anything over 80-100 mL/kg/day is considered polydipsia (i.e. 7-½ to 9-½ cups per day for that same 50 pound dog).
Though it can be tempting to restrict water intake in a pet that is having urinary accidents in the house or needing to go out with increased frequency, this is very rarely recommended, and in the rare cases where it is indicated it should be done only with supervision from your veterinarian. Restricting water in the face of underlying metabolic or infectious diseases could lead to dehydration (sometimes severe) and decompensation of the underlying problem.
So, if you are concerned that your pet might be hitting the bowl a little too hard be sure to talk to your pet’s veterinarian!