Portable ultrasonography and bladder volume accuracy--a comparative study using three-dimensional ultrasonography.

OBJECTIVES: To compare the ultrasound bladder volume accuracy and level of agreement between two portable bladder scanners (Bladderscan and Bardscan) and a three-dimensional ultrasound (3D-US) system.

METHODS: A total of 50 healthy volunteers were scanned using the Bladderscan BVI 3000, Bardscan, and 3D-US system (HDI 4000), in random sequence. The BVI3000 is a dedicated bladder volume calculator, and the Bardscan combines real-time ultrasonography with bladder volume calculation. The ultrasound bladder volumes were compared with the voided volume measurements. The volunteers underwent repeat scanning after voiding, and those with a measurable residual volume were excluded from the final analysis.

RESULTS: A residual volume was detected in 16 subjects (32%). In the remaining 34 subjects, the mean voided volume +/- standard deviation was 252.9 +/- 167.4 mL (range 33 to 709). A significant correlation (P <0.001) was found between the voided and ultrasound volumes with all three methods (Bardscan, r = 0.97; Bladderscan, r = 0.98; and 3D-US system, r = 0.99). No significant differences were found between the voided volumes and the Bladderscan or 3D-US volumes; however, the Bardscan significantly underestimated the voided volume by a mean of 21.4 mL (t = 2.84, P = 0.0076). The Bland-Altman 95% limit of agreement between the voided and calculated volumes was -64.5 to 107.2 mL, -73.7 to 88.4 mL, and -28.9 to 40.0 mL for the Bardscan, Bladderscan, and 3D-US systems, respectively.

CONCLUSIONS: The results of our study have shown that although the Bardscan has the advantages of real-time scanning with portability and instantaneous volume calculation, it is not as accurate as the Bladderscan. The accuracy and level of clinical agreement was greatest when using the 3D-US system to calculate the bladder volume.