Accuracy of postvoid residual volumes after vaginal delivery: a prospective equivalence study to compare an automatic scanning device with transurethral catheterization

INTRODUCTION AND HYPOTHESIS: Abnormal postvoid residual volumes (PVRV) after delivery are common in daily clinical practice. By using an automatic scanning device, unnecessary catheterizations can be prevented. The aim of this study was to determine the accuracy of PVRV after vaginal delivery measured by an automatic scanning device through a comparison with transurethral catheterization. MATERIALS AND METHODS: This prospective observational equivalence study was performed in patients who delivered vaginally between June 2012 and May 2017 in three teaching hospitals in The Netherlands. After the first spontaneous void after delivery, postvoid residual volume (PVRV) was measured with a portable automatic scanning device (BladderScan® BVI 9400). Directly afterward, it was measured by catheterization. Correlation between measurements was calculated using Spearman’s correlation coefficient and agreement plot. The primary outcome was to validate the correlation between the BladderScan® compared with the gold standard of transurethral catheterization. RESULTS: Data of 407 patients was used for final analysis. Median PVRV as measured by BladderScan® was 380 ml (± 261–0–999 ml) and by catheterization was 375 ml (± 315–1800 ml). Mean difference between measurements was −12.9 ml (± 178 ml). There was a very good correlation between methods (Spearman’s rho = 0.82, p < 0.001). Using a cut-ff value of >500 ml, specificity and sensitivity were 85.4 and 85.6%, respectively. CONCLUSIONS: The BladderScan® (BVI 9400) measures PVRV precisely and reliably after vaginal delivery and should be preferred over catheterization.