Clinicopathologic aspects of diabetes insipidus in the dog

The clinicopathologic findings associated with diabetes insipidus were evaluated in 2 dogs. In both patients, the clinical diagnosis was confirmed by urinary response to administration of exogenous vasopressin. Microscopic examination of the pituitary glands revealed the presence of lymphosarcoma in one dog, and an adenoma of the pars intermedia in the other. The clinical syndrome of diabetes insipidus in the dog must be differentiated from other diseases associated with polyuria and polydipsia including renal diabetes insipidus, primary renal failure, hyperadrenocorticism, diabetes mellitus, pyometra, liver failure, and psychogenic water consumption. In addition to differences in the spectrum of clinical signs, carefully performed water deprivation and exogenous vasopressin concentration test must be properly performed, however, or misleading results and misdiagnosis may result. Because various components of the technical aspects of these tests have been incompletely described or erroneously reported in veterinary literature, they are described in detail.