Objective. To clarify the frequency

presentation

associated factors

treatment and outcome of hy-ponatremia after transsphenoidal surgery of pituitary adenomas.Methods. Retrospectively reviewed the database of 183 patients who underwent transsphenoidal surgery of pituitary adenomas between January 1999 and June 2000 in our department.Results. 38.8% （71/183） had postoperative hyponatremia. Among them

59.2% （42/71） appeared on the 4th to 7th day postoperatively. 59.2% （42/71） presented with nausea

vomiting

headache

dizziness

confusion and weakness. Hyponatremia was related to age

tumor size and adenoma type

but not related to sex and degree of resection. Treatment consisted of salt replacement and mild fluid restriction in 4 patients and salt and fluid replacement in 67 patients. Hyponatremia resolved within 16 days in all the patients.Conclusions. Hyponatremia often appeared about 7 days after transsphenoidal surgery of pituitary adenomas

especially in elderly and patients with macroadenomas and huge pituitary adenomas. The principle of treatment was salt and fluid replacement.