Water intoxication in a psychotic patient with normal renal water excretion.

A psychotic patient with hyponatremia and obtundation following short-term ingestion of large amounts of water was found to have maximally dilute urine, and underwent brisk diuresis until the serum osmolality returned to normal. This is the first report of normal renal diluting capacity as documented by measurement of urine osmolality in a water-intoxicated, schizophrenic patient, and demonstrates that normal renal diluting mechanisms may on occasion be overwhelmed by massive water ingestion.