Differential diagnosis and pathophysiology of diabetes insipidus

Differential diagnosis of diabetes insipidus has been discussed in this paper in terms of pathophysiological aspects. Three points are emphasized: (1) we should include dipsogenic D.I. as one form of diabetes insipidus; (2) the water deprivation test is inconclusive in approximately 25% of patients, where the main difficulty is to distinguish between partial neurogenic D.I. and dipsogenic D.I.; and (3) this difficulty cannot be solved by a single determination of plasma vasopressin. Pathophysiology of inherited neurogenic D.I. and nephrogenic D.I. are also discussed.