64 - Handheld 3D Ultrasound for Bladder Volume Assessment: Accuracy, Reproducibility, and Clinical Feasibility Compared to Conventional 2D Imaging

Purpose: To compare the accuracy, reproducibility, and feasibility of a handheld three-dimensional (3D) ultrasound device with conventional two-dimensional (2D) ultrasound for urinary bladder volume measurement, using voided urine volume as the reference standard.

Materials and Methods: Fifty-three healthy male volunteers (mean age 19.6 ± 2.0 years) underwent bladder volume assessment by two novice operators using both methods: 2D ultrasound (manual caliper-based) and handheld 3D ultrasound (Butterfly iQ, automated sweep). Each operator performed two repeated measurements per method. True voided volume was recorded immediately after scanning. Accuracy was assessed by mean differences, percentage error, and Bland–Altman analysis. Intra- and inter-operator reproducibility were evaluated with intraclass correlation coefficients (ICC).

Results: Both methods underestimated bladder volume compared to voided volumes (p < 0.001). The 3D method demonstrated higher accuracy, with median percentage error −11.2% to −12.0%, versus −27.6% to −36.7% for 2D. Mean bias ranged from −64.9 mL to −72.3 mL for 3D, compared to −137.4 mL to −191.6 mL for 2D. Intra-operator reproducibility was excellent across all methods (ICC > 0.96). Inter-operator agreement was higher for 3D (ICC = 0.977; bias 7.3 mL) than for 2D (ICC = 0.927; bias −54.2 mL). All scans were successfully completed; however, the 3D device occasionally faced technical errors in very large bladders ( >700 mL).

Conclusion: Handheld 3D ultrasound yielded greater accuracy and inter-operator consistency than conventional 2D ultrasound, with faster acquisition and minimal operator input. Despite systematic underestimation, its performance supports broader clinical adoption in point-of-care settings, particularly where operator variability is a concern.