Evaluation and management of diabetes insipidus.

Diabetes insipidus is an uncommon condition characterized by polyuria and polydipsia. The symptoms and biochemical changes of this condition result from either a lack of antidiuretic hormone or renal insensitivity to its effect. Failure to produce or release antidiuretic hormone may result from cranial pathology, including trauma and surgery. The renal insensitivity to antidiuretic hormone that occurs in patients with nephrogenic diabetes insipidus may be caused by genetic factors, drugs (especially lithium) or specific disease processes. Patients may compensate for polyuria and nocturia by excessive water intake but show marked decreases in urine specific gravity and osmolality. Patients with severe and uncompensated symptoms develop marked dehydration, neurologic symptoms and encephalopathy. The water deprivation test is useful in diagnosing diabetes insipidus and in differentiating neurogenic from nephrogenic cases. Neurogenic diabetes insipidus may respond to nasal administration of desmopressin. Nephrogenic diabetes insipidus requires good hydration and monitoring of body chemistry. Thiazides and amiloride may relieve symptoms.