Real-Time Bladder Volume Monitoring for Pediatric Patients Using a Commercially Available Wearable Ultrasound Device

Introduction: We tested whether a commercially available, wearable bladder ultrasound device (DFree^Ⓡ, Triple W Japan Inc.) could accurately estimate bladder volume in children with urologic conditions by comparing sensor readings to instilled volume during cystometrography (CMG). Materials and Methods: We prospectively enrolled 40 children (6 months to 18 years old). The device was taped to the suprapubic region and volume measurements obtained during CMG. Primary outcome was device accuracy, defined as device indicating ≥ 8 (0−10 scale) when the instilled volume was ≥ 80% of CMG-determined capacity. Mixed effects linear regression modeled the relationship between sensor indication and instilled volume after adjusting for clinical variables. Results: Median age was 7.2 years, 20 (50%) were male, 27 (67.5%) were on clean intermittent catheterization, 30 (75%) had spina bifida. The sensor accurately measured capacity in 46.2% of patients with a sensitivity of 0.70, specificity of 0.13, positive predictive value of 0.53, and negative predictive value of 0.22. Device readings were statistically associated with instilled volume; single-digit (10%) increase in sensor reading was associated with an average increase of 10% (95% CI: 9% to 12%, p < 0.001) in bladder volume. Conclusion: A commercially available, wearable ultrasound bladder sensor accurately measured bladder capacity in 46.2% of children undergoing UDS. Our findings caution clinicians in recommending these types of direct-to-consumer devices. Repeated measures testing is needed to determine if the accurate device indicators observed in a minority of patients herein, are reproducible. Trial Registration: Our study did not need to be registered per the International Committee of Medical Journal Editors Uniform Requirements.