Hyponatremia Associated with Hepatocellular Carcinoma.

Hyponatremia is the most common electrolyte abnormality in clinical practice, and a differential diagnosis of the etiologic disorders is crucial because hyponatremia is associated with many different disease states including malignancies. Although only a few cases of hyponatremia with hepatocellular carcinoma (HCC) have been previously reported, the abnormal expression of arginine vasopressin (AVP) in tumor cells has not been demonstrated. We herein present a rare case of hyponatremia associated with the aberrant expression of AVP in tumor cells of HCC. This case suggests that an extensive diagnostic work-up is needed in patients with hyponatremia because hyponatremia may provide diagnostic clues for the presence of other underlying disorders.