Three-dimensional ultrasonographic bladder volume measurement: reliability of the Virtual Organ Computer-Aided...

The purpose of this study was to investigate the reliability of Virtual Organ Computer-Aided Analysis (VOCAL; GE Healthcare, Kretztechnik, Zipf, Austria) using the 4 standard rotation steps to measure the bladder volume with 3-dimensional (3D) ultrasonography.

Using the 4 standard rotation steps of VOCAL, 2 independent observers made 3D volume measurement data sets from the urinary bladder (n = 180). Sets of 30, 20, 12, and 6 planes were obtained from the sequential rotations of 6 degrees, 9 degrees, 15 degrees, and 30 degrees, respectively. The internal contours of the bladders were determined manually. Reliability was evaluated with the intraclass correlation coefficient (ICC), and Bland-Altman plots were generated to examine bias and agreement. One-way analysis of variance was used to compare bladder volume measurements between the angles. P < .05 was considered statistically significant.

A high degree of reliability was observed between pairs of different rotation angles (ICC, 0.994-0.999). There was good agreement between all pairs of different rotation angles, with percentages of the mean difference ranging from -0.9% to 1.8%. No significant difference was found for bladder volume measurements by the VOCAL technique with varying rotation steps. Intraobserver and interobserver reliabilities were high (ICC, 0.994-0.998).

Urinary bladder volume measurement by the VOCAL technique using different rotation steps is highly reliable. A plane rotation of 30 degrees produces the fastest result.