Diabetes insipidus is a disorder in which the kidney is insensitive to a hormone, called anti-diuretic hormone (ADH) or in which there is not sufficient quantity of this hormone available. The result is excessive drinking and urination, or polydipsia and polyuria. This is one cause of changes in urinary habits that leads to problems with urination inside the house in dogs in which "housebreaking" seemed to be satisfactory prior to the disease onset. ADH is secreted by the body when it has a need to conserve water. It makes the kidneys work harder to conserve water, which makes the urine more concentrated.

When the dog can not respond to this hormone or doesn't make enough of it, the dog can not concentrate its urine. This can lead to serious problems, including death, if the dog does not have access to large quantities of water. On the other hand, it may not cause any significant problem if there is always plenty of water available. This problem can occur for a number of reasons and for no reason at all. Examples of predisposing causes are kidney failure, hyperadrenocorticism, liver disease, pyometra and others. These things affect the kidney's ability to respond. Head trauma or brain cancer can affect the body's ability to produce ADH. This condition is treated using desmopressin acetate (DDAVP), which is a replacement for the antidiuretic hormone. It can be administered intra-nasally or on the conjunctiva (the inside lining of the eyes). It is pretty effective. Unfortunately, it is also somewhat expensive. Some dogs benefit from therapy with other medications, including chlorpropamide and chlorothiazide diuretics.

The prognosis for this condition varies with the underlying cause. Dogs that have diabetes insipidus due to trauma often recover in a short time and the same is true after successful treatment of pyometra. The prognosis is good for spontaneous occurrences of diabetes insipidus as well. When it occurs for other reasons the prognosis is usually less favourable.