Polydipsia, drinking excessively due to thirst, is psychogenic when it is caused by neurological or behavioral reasons rather than a bodily problem. While the compulsion is sometimes harmless, extreme cases can lead to kidney failure and death. A number of medical conditions may lead to polydipsia, including psychogenic polydipsia; sometimes the problem is simple compulsive behavior that's treatable with medication and behavior modification.
Polydipsia in dogs is defined as drinking more than 80 to 100 milliliters per day, though this figure requires adjustment depending on the size of the individual dog. Symptoms are frequently not present -- a dog must drink much more than 100 milliliters of water per day for symptoms to occur, as the dog kidney can process up to 200 milliliters a day . Polydipsia's excessive drinking often leads to excessive urination or polyuria. Kidney failure may occur from a condition called solute washout, in which the necessary electrolytes are removed from the kidneys, eliminating the ability to concentrate urine.
Possible Physical Causes
A number of physical conditions can cause polydipsia. Hot weather and high-salt diets are both causes of drinking more water. Diabetes, hyperthyroidism, renal disease, renal dysplasia, polycystic kidney disease and renal lymphoma are all issues that can all increase a dog's water intake. They must be treated to eliminate polydipsia. Certain medications, including glucocorticoids, phenobarbital, diuretics and salt supplements, can cause your dog to drink more. Behavior-based polydipsia is often preceded by a head injury, generally to the thalamus or the adenohypophysis.
Diagnosis of Elimination
Once most physical causes have been eliminated, your veterinarian may recommend a water deprivation test, during which the dog's water intake is restricted to less than 90 milliliters per day for two or three days. Then water is not offered at all while the dog is closely monitored. When your dog has lost 3 percent to 5 percent of body weight from the fluid loss -- over the course of several hours or more than a day -- the urine concentration is measured. If specific gravity is higher than 1.025, your vet may administer vasopressin or desmopressin to encourage kidney function. A specific gravity below 1.030 usually indicates the problem is psychogenic. It is either a neurologically or behaviorally motivated problem rather than a purely physical one.
If a dog with psychogenic polydipsia is the only dog in the house, simply restricting the available water to healthy amounts and offering it at structured times throughout the day will solve the problem. If the compulsive behavior is due to anxiety rather than nervous-system injury or age-related cognitive decline, you may be able to modify the behavior. Distracting your dog, as well as rewarding him by offering him a favorite treat when the object of his distress appears, can desensitize him to the stimulus. Provide plenty of exercise, social interaction and mental challenges like training, or puzzle toys with food inside, throughout the day to suppress compulsive behavior.