Symptomatic hyponatremia after voluntary excessive water ingestion in a patient without psychiatric problems

Water intoxication usually happens in patients with a psychiatric problem, who are subject to compulsive water ingestion, and during clinical examinations, such as uroflowmetry, and is seldom observed in ordinary people. Here we report a patient with severe hyponatremia due to voluntary water drinking coexisting with no psychiatric problems. The case presented clinically significant hyponatremia 124 mmol/L without any signs of dehydration after voluntary ingestion of 4000 ml of water over 3 hours. She normally responded to ingestion of 1000 ml of water over 20 min after recovery from hyponatremia, and did not meet the diagnostic criteria of SIADH. She was not a compulsive drinker. The present case suggests that one should consider water intoxication as a cause of hyponatremia in a patient without signs of dehydration, even if he/she does not have a history of compulsive water ingestion.