Endocrine Abstracts

Introduction: The incidence of hyponatremia as a delayed complication of transsphenoidal surgery varies widely from study to study and much of the debate has focused on the symptomatic hypotonic hyponatremia (SHH) occurring usually after discharge.

Aim/Design: We studied the incidence, risk factors, course and management of postoperative SHH in two large series of endoscopic transsphenoidal surgery (ETS) for pituitary tumors.

Results: The first series included 1199 consecutive surgical procedures carried out during the last 13 years by a single surgeon in Italy (87% adenomas, 10% craniopharyngiomas/Rathke’s cleft cysts, 3% miscellaneous lesions). 103 patients were excluded on the basis of exclusion criteria (postoperative triphasic diabetes insipidus, diuretics, drug-induced SIADH, scant lab data). A total of 1096 eligible patients were identified. Of these, 50 (4.5%) developed SHH, which occurred after discharge in any patients but three. Nadir of medians of SHH (126 mmol/l) occurred on postoperative day 8. Clinical data and laboratory tests were consistent with SIADH in all the patients. Age, tumor size and tumor type did not correlate with the development of SHH. Conversely females were more likely to develop SHH than males (F/M: 2.8/1). Treatment consisted of fluid restriction in 42% and hypertonic saline in the remaining 52%. No case of osmotic demyelination syndromes occurred. The second series included 316 consecutive surgical procedures done during a 34-month period ending March 2011 by a single surgeon in USA (72.8% adenomas, 15% craniopharyngiomas/Rathke’s cleft cysts, 2.8% arachnoid cysts, 9.2% miscellaneous lesions). SHH developed in 16 patients (5%). Again, clinical and laboratory data were consistent with SIADH in all the patients. Nadir of medians of SHH (123 mmol/l) occurred on postoperative day 7. The major risk factor was the presence of a macroadenoma.

Conclusion: The incidence of SHH in patients undergoing ETS was about 5% in both series, but different risk factors were identified (i.e. gender in the first series, macroadenoma in the second series). Interestingly, the incidence of SHH in this study was identical to that found in a previous study designed by one of us for the standard microscope transsphenoidal approach some years ago.

Declaration of interest: The authors declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project.

Funding: This research did not receive any specific grant from any funding agency in the public, commercial or not-for-profit sector.