Comparison of Diagnostic Accuracies of Commonly Used Trial of Void Parameters

Importance: Understanding the diagnostic accuracy of postoperative trial of void (TOV) parameters is important for decision making related to postoperative catheterization.

Objective: The aim of the study was to compare the diagnostic accuracies of common postoperative TOV parameters.

Design: The study population comprised a prospective cohort undergoing outpatient urogynecologic procedures at a tertiary referral center from September 2018 to June 2021. Participants recorded their postvoid residual volume (PVR), voided volume, and subjective force of stream (sFOS) for all postoperative voids until meeting criteria to stop. The primary outcome was the sensitivity of TOV parameters in predicting postoperative urinary retention, defined as PVR ≥1/2 voided volume on the first 2 postoperative voids. Sample size was set at 183 to detect a 20% difference (α = 0.05, β = 0.2, up to 20% with missing data) in sensitivity between TOV parameters. Diagnostic accuracies were compared with McNemar's test for paired proportions, with Youden's index calculated to determine optimal thresholds.

Results: The 160 participants had a mean age of 52.1 ± 11.4 years and a mean body mass index of 28.9 ± 5.8 kg/m2 (calculated as weight in kilograms divided by height in meters squared). Mean preoperative PVR was 25.8 ± 29.9 mL. Most participants had surgery that included a midurethral sling (137/160, 85.6%). Thirty-four (34/160, 21.3%) participants met criteria for postoperative urinary retention. The optimal recovery room TOV thresholds to predict postoperative urinary retention were PVR ≥87 mL (sensitivity 96.8%, specificity 60.0%), voided volume ≤ 150 mL (sensitivity 83.9%, specificity 72.3%), and sFOS ≤60% (sensitivity 100%, specificity 50.8%). Voided volume ≤ 150 mL had greater diagnostic accuracy than PVR ≥100 mL (156.2 vs 151.8).

Conclusions: In this cohort, PVR ≥87 mL, voided volume ≤ 150 mL, and sFOS ≤60% had optimal diagnostic accuracy for postoperative urinary retention.