Severe hypernatremia complicating urinary tract obstruction.

Severe hypernatremia and hyperosmolar dehydration developed in a patient with partial urinary tract obstruction. The urine was initially hypotonic, and there was no response to exogenous vasopressin. These abnormalities resolved with relief of the urinary tract obstruction and replacement of the water deficit. This case documents lower urinary tract obstruction as a cause of nephrogenic diabetes insipidus and severe hypernatremia and illustrates its reversible nature.