Severe hyponatremia occurring after surgical stress in a patient with mitochondrial disease.

A 53-year-old man with mitochondrial disease underwent gastrectomy because of gastric cancer. Three days after the surgery, he developed severe hyponatremia (Na, 106 mmol l(-1)) together with hypovolemic shock and lactic acidosis. Despite the hyponatremia, his urine sodium concentration was high, suggesting renal salt wasting. Although mitochondrial diseases are not common and hyponatremia in patients with these diseases is not well known, clinicians should pay close attention to serum sodium levels and maintain them properly.