Severe hyponatremia due to surreptitious water intoxication in a hospitalized patient.

Hyponatremia is a common electrolyte abnormality among hospitalized patients and often present as first sign of other underlying medical conditions. Severe hyponatremia can be life threatening and requires prompt diagnosis and treatment. We present a case of refractory hyponatremia that was a diagnostic challenge requiring a prolonged hospitalization. Diagnosis of primary polydipsia was ultimately suspected due to improbable 24-h urine studies and confirmed through complete removal of free water access in the form of disconnecting the bathroom faucet in the patient's hospital room. Diagnosis and management of primary polydipsia is further discussed.