To evaluate the relation between voided volume and void trial “success” to create an algorithm that minimizes the need for postvoid residual volume (PVR) assessment in backfill-assisted void trials.Methods
This article is an ancillary analysis of deidentified data from a randomized trial evaluating prophylactic antibiotics after urogynecologic surgery. Void trials were routinely performed after surgery; voided volumes, PVR, and void trial outcomes were collected. The void trial regimen was as follows: the bladder was backfilled with 300 mL of normal saline or until the patient reported the urgency to void, the catheter was removed, and the participant was prompted to void immediately. PVR volume was measured either by sonographic bladder scan or catheterization. Voided volumes were categorized in 25-mL increments from 50 to 225 mL. For each voided volume range, the PVR and void trial outcome data were incorporated to calculate sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) in terms of ability of voided volume alone to predict a passing void trial result. An algorithm was created using the voided volumes that optimize PPV and NPV.Results
The study population included 255 participants. Voided volumes <100 mL and ≥200 mL were identified as optimal thresholds to predict failure and passage of backfill-assisted void trials, respectively. When patients voided <100 mL, 3% passed their void trial (NPV odds ratio 96.7, 95% confidence interval 88.6–99.5). When patients voided ≥200 mL, 97% passed (PPV odds ratio 97.4, 95% confidence interval 93.5–99.3).Conclusions
We propose an algorithm for void trials after urogynecologic surgery. After backfilling the bladder if voided volume is ≥200 mL, the void trial is successful and no PVR is needed; if voided volume is between 100 and 199 mL, the void trial is indeterminate and PVR is recommended; and if voided volume is <100 mL, the void trial is unsuccessful and catheterization is needed. Applying this algorithm to our study population would have eliminated the need for PVR in 85% of patients. Calculated PPVs and NPVs depend on the prevalence of voiding dysfunction in the population being studied, and therefore may be unique to our institution.