[A case of SIADH developed during neoadjuvant chemotherapy using nedaplatin and 5-fluorouracil in a patient with esophageal cancer].

A 77-year-old male with thoracic esophageal cancer (cT3N3M0, Stage III) received nedaplatin at 80mg/m2 for 1 day and 5-fluorouracil at 800mg/m2 for 5 days as neoadjuvant treatment. On the fifth day of treatment, he lapsed into a coma (Japan Coma Scale 30), and his serum sodium concentration was found to be decreased to 116mEq/L. We concluded hyponatremia due to SIADH (syndrome of inappropriate secretion of antidiuretic hormone) induced by chemotherapy based on the fact that the patient had no finding of dehydration, particular history of related disorders, serum hypoosmolality accompanied by urine hyperosmolality and persistent urinary sodium excretion. We treated him with fluid restriction, sodium supplement and administration of loop diuretic. Then he regained consciousness and appropriate serum sodium level. Thereafter, hyponatremia was corrected without recurrence, and the patient underwent radical esophagectomy safely. He has been in good condition without recurrence of esophageal cancer after surgery.