A case of water intoxication with prolonged hyponatremia caused by excessive water drinking and secondary SIADH.

Water intoxication is a life-threatening disorder accompanied by brain function impairment due to severe dilutional hyponatremia. We treated a 22-year-old man without psychotic illness who had been put in a detention facility. He drank 6 liters of water over a 3-hour period at the facility as a game's penalty, and he showed progressive psychiatric and neurological signs including restlessness, peculiar behavior and convulsions. On his admission, 15 h after the discontinuation of the water drinking, he was in a coma, showing intermittent convulsions and remarkable hyponatremia (120 mmol/l). Because his laboratory tests showed hypertonic urine and normal sodium excretion, the diagnosis of secondary development of syndrome of inappropriate secretion of antidiuretic hormone (SIADH) was strongly suggested and later confirmed by the suppression of the renin-aldosterone system and the inappropriately elevated secretion of ADH. Saline infusion and an initial administration of furosemide in addition to dexamethasone as treatments for the patient's brain edema successfully improved his laboratory data and clinical signs by the 3rd hospital day, and he was returned to the facility without physical or psychiatric abnormalities on the 6th day. The secondary SIADH might have been due to the prolonged emesis, recurrent convulsions and rapid elevation of intracranial pressure.