Reliability of an automatic ultrasound system for detecting postpartum urinary retention after vaginal birth

Abstract

Background. Urinary retention is a common postpartum condition which may lead to short- and long-term complications. Objective. To assess the reliability of a commercially available automatic bladder volume scanner in the puerperium, and to specifically identify women with a post-void residual volume of 400ml or more. Methods. A prospective comparison of ultrasound estimated bladder volume and urine volume measurement after catheterisation in 100 women at risk for postpartum urinary retention (PUR) after vaginal delivery. Results. The mean difference between the ultrasound estimates and the catheter volume measurements was 26ml, with the corresponding 95% confidence interval (2.6, 49.4ml). The sensitivity and specificity for the scanner, using the clinically desired value of a 400-ml threshold, are 0.76 and 0.96, respectively. With a perfect classification for sensitivity at a 300-ml threshold, specificity may drop to about 50%. Even using this cut-off point, the number of women catheterised would be reduced by half compared to a procedure of catheterising all women at risk for postpartum urine retention diagnosed by clinical judgment alone. Conclusion. The ultrasound scanner is a reliable screening instrument for detecting PUR after vaginal birth. © 2007 Taylor & Francis.