Applicability of Bladder Voiding Efficiency as a Clinical Parameter for Assessing Postpartum Covert Urinary Retention

This study investigated the clinical applicability of bladder voiding efficiency in assessing covert urinary retention, comparing postvoid residual volumes between postpartum days 0-4.This longitudinal observational study included women with vaginal delivery and no lower urinary tract dysfunction or residual urine in late pregnancy.Pre-and postvoid bladder volumes, and voided volumes, were measured using ultrasonography at the first postpartum voiding (within 2-6 hours after delivery) and daily on postpartum days 1-4.Voiding efficiency was calculated as the voided volume to the pre-voiding bladder volume ratio.To assess the applicability of bladder voiding efficiency, the prevalence of covert urinary retention was compared among four parameters: postvoid residual volume ≥ 150 mL or ≥ 100 mL and bladder voiding efficiency < 70% or < 80%.Cumulatively, postvoid residual volume thresholds ≥ 150 mL and ≥100 mL were identified in 24 and 29 women, respectively.Among these 29 women, 26 met the bladder voiding efficiency threshold < 70% or < 80%; additionally, 11 other women met this criterion, totaling 37. The regression slope for postvoid residual volume against pre-voiding bladder volume was 0.35, indicating a positive correlation, while the slope for bladder voiding efficiency was -0.0040, showing a horizontal line.Assessment of bladder voiding efficiency can identify most women with covert urinary retention, determined by postvoid residual bladder volume.Bladder voiding efficiency is independent of the pre-voiding bladder volume, enabling the assessment of covert urinary retention even at low bladder volumes, corroborating its clinical applicability.