Pericardial tamponade-associated hyponatremia.

We describe a 58-year-old patient with adenocarcinoma of the lung who suffered from severe weariness that was attributed to hyponatremia. The cause of hyponatremia was found to be a malignant pericardial effusion that caused pericardial tamponade. The hyponatremia was corrected rapidly after the evacuation of the malignant effusion. The pathogenetic mechanisms of hyponatremia secondary to pericardial effusion are discussed.