Endocrine Abstracts

Background and aims: Diabetes insipidus (DI) is a common complication after transsphenoidal surgery (TSS), but resolves in the majority of patients. We determined the osmolalities and timing of DI most that best predicted long-term outcome.

Methods: Case series study randomly including 54 patients out of total 99 patients who underwent transsphenoidal surgery over 18 months. Follow up information was ascertained from clinic review or by telephone interview. Patients who became polyuric with urine output of 200 ml/h for two consecutive hours with plasma osmolality ≥285 mosmol/kg and urine osmolality ≤500 mosmol/kg were considered as having early (potentially transient) DI and candidates for subcutaneous DDAVP.

Episodes of DI were divided into three categories: 1. Early DI: up to 36 h post operatively.

2. Intermediate- after 36 h but resolved before hospital discharge.

3. Chronic- patients had DI on discharge and/or at 3 month follow up.

Results: About 7/54 (13%) of patients developed chronic DI. 29/54 (54%) of patients developed early polyuria in whom 18 met criteria for DI, 2 had appropriate diuresis or natriuresis and 9 resolved before initial testing. In total, 7/29 of these patients progressed to chronic DI. In contrast, none of 14 patients who became polyuric for the first time after 36 h had persistent DI. About 6/7 patients with chronic DI had plasma osmolal >295 and urine osmolal <200 when initially tested.

Conclusions: Patients who do not develop DI within 36 h after TSS are unlikely to develop chronic DI. Plasma osmolal >295 and urine osmolal <200 within 36 h have a high sensitivity and specificity for predicting long term DI, although patients may still require short term treatment. Recognising low risk patients may help shorten inpatient duration.