THE ACCURACY OF PORTABLE ULTRASOUND SCANNING IN THE MEASUREMENT OF RESIDUAL URINE VOLUME

The accuracy of 2 successive models of a portable (2.5 kg.) ultrasound unit in determining residual urine volumes in 100 patients was assess ed. Ultrasound measurements were compared to post-scan bladder volumes obtained by catheterization and fluoroscopic screening in the same pa tients. The first ultrasound unit (group 1, 50 patients) showed correl ation with residual volumes of 0.86 (R(2) = 0.73) and a mean differenc e from the true residual volume of 41 mi. (95% confidence interval 26 to 55 mi.). The second ultrasound unit (group 2, 50 patients) showed c orrelation with residual volumes of 0.97 (R(2) = 0.94) and a mean diff erence from the true residual volume of 24 mi. (95% confidence interva l 17 to 31 mi.). The differences in volumes were significantly lower w ith scanner 2 (t = 2.02, p = 0.047). The mean difference between cathe ter volume estimate and true bladder volume was 25 mi. (95% confidence interval 16 to 34 mi.). The accuracy of the BladderScan BVI 2500+ sca nner is as good as catheter estimations of true residual volume and i s sufficient to recommend its use as an alternative to catheterization for the determination of residual urine volume.