gms | German Medical Science

Objective: Hyponatremia caused by a syndrome of inappropriate antidiuretic hormone secretion (SIADH) represents a possible postoperative complication in pituitary surgery. Complication rates found in the literature diverge between 2.5 % and 38 %. Here we present a retrospective analysis of postoperative occurrence of SIADH in a case series of endoscopic transsphenoidal pituitary surgery.

Methods: Between November 2007 and June 2019 we consecutively performed 206 endoscopic transsphenoidal pituitary operations that were included. Perioperatively we monitored electrolytes in both serum and urine along their osmolality in order to look for SIADH and other hyponatremic episodes. All cases were supervised by our endocrinology department.

Results: Eight of the 206 cases developed postoperatively a SIADH (3.9 %). In average onset of hyponatremia was at the sixth postoperative day (6.0 d ± 1.3 d), endured four days (4.0 d ± 1.4 d) during which medium sodium levels were at 128.2 mmol/l (± 4 mmol/l). Along the hyponatremic episodes not diagnosed as SIADH there were three patients (1.5 %) with a cerebral salt wasting syndrome (CSW) and one case of Addison crisis (0.5 %). In our series neither age nor gender nor revision surgery nor any other factors were identified as risk factors for developing postoperative SIADH.

Conclusion: Our results are generally in line with current results in the literature, however our rate is located at the lower end of reported SIADH complication rates. Hyponatremic episodes are not uncommon and a potentially dangerous complication of transsphenoidal pituitary surgery. It is critical to identify and treat hyponatremia as soon as possible. Moreover it is crucial to distinguish between SIADH and CSW as their respective therapies are oppositional.