Delayed postoperative hyponatremia followed by acute renal failure in a patient with an ACTH-secreting microadenoma of the pituitary.

The selective transsphenoidal adenomectomy of an ACTH-secreting microadenoma was followed by clinically symptomatic delayed hyponatremia in an otherwise healthy patient. During mild fluid restriction for the treatment of the hyponatremia, acute renal failure occurred. The renal failure was resolved by treatment with furosemide. Fluid restriction is considered a standard therapeutic approach for the treatment of this probably SIADH-induced hyponatremia. Until now, acute renal failure has not been reported under these circumstances. This unique case demonstrates the need of close monitoring of patients with delayed hyponatremia following pituitary surgery.