Bladder volume determination: Portable 3-D versus stationary 2-D ultrasound device

Objective: To investigate how accurately a portable three-dimensional (3-D) scanner and a multipurpose two-dimensional (2-D) real-time scanner determined bladder volumes. Study Design: Prospective, controlled clinical trial, single-blind, crossover design. Setting and Participants: Twenty-three inpatients with permanent bladder catheters participated voluntarily in this study. Methods: The bladders of 20 patients were filled through an indwelling catheter with 60, 110, 160, 210, and 260mL sterile normal saline. Volumes were measured twice with each device. Measurements were compared with the actual bladder volumes. Results: The 2-D device showed better reproducibility, particularly at lower bladder volumes. The 3-D scanner showed a significant difference between. the two measurements at 160mL (p <.05) and had poor reproducibility at 110, 210, and 260mL. Both devices overestimated actual bladder volume at fillings of < 160mL and underestimated it at fillings of greater than or equal to 160mL. The range between the 25th and 75th percentiles was always larger for the 3-D scanner, except for the 210mL reading. Conclusion: Both devices showed sufficient accuracy for clinical practice. Ultrasound measurements of >110mL should be followed by catheterization to detect potentially harmful bladder volumes.