Bladder scan accuracy in pediatric patients: Does patient position matter?

Abstract

Despite its widespread use in pediatric urology clinics, portable bladder scanning is an insufficiently studied tool that lacks standardized protocols. Workflow at the present clinic can be impeded by scanning in the supine position, due to multiple trips to the restroom and back to the exam room. The current study sought to test accuracy of bladder scanning, and hypothesized that it would be equally accurate in the standing versus traditional supine position in children, given the intra-abdominal location of their bladders. Sixty children from the bladder/bowel clinic were prospectively recruited. Patients had a formal supine renal/bladder ultrasound and pre-void and/or post-void assessment with scans in both the standing and supine positions. The methods were compared using repeated measures one-way ANOVA. Mean age was 9.2 years. The majority (85%) were female. All bladder scan estimates except for post-void supine significantly correlated with ultrasound volume. Pre-void standing had the strongest correlation (r=0.83). There was no difference between ultrasound and standing estimates for pre-void volumes, but supine underestimated volumes by 44.8ml(P<0.01) (Summary Figure). Sub-group analysis of children aged <10 years showed that pre-void scans in both positions significantly underestimated volume (12% of estimated bladder capacity for standing, 24% for supine, P<0.05). For post-void volumes, both standing and supine overestimated measurements by 29.4ml and 18.3ml, respectively (both P<0.001). Sub-group analysis based on age yielded comparable results. It is believed that this is the first study to examine bladder scanning in different positions. Limitations included small sample size, and the study fell short of cost-effectiveness and outcome analysis to assess the real-life impact of the proposed use of standing bladder scanning in the clinic. Standing bladder scanning may be used in place of supine. However, bladder scanning generally appeared to have poor accuracy, especially in younger children, and thus should be used with caution. In practical terms, it may decrease specificity of detecting elevated post-void residuals compared to ultrasound.