Accuracy of three-dimensional transvaginal ultrasound in uterus volume measurements; comparison with two-dimensional ultrasound.

The purpose of this study was to document the accuracy of 3-D uterus volume and to compare it with 2-D measurements. Transvaginal ultrasound (US) examinations were performed in 48 consecutive patients before hysterectomy. The examinations were stored digitally on an internal disk drive for subsequent measurements in virtual organ computer-aided analysis (VOCAL) program. Immediately after the hysterectomy, the true volume was measured in a water bath. A total of 5 patients were excluded due to difficulty of identifying the borders of their uterus; 8 patients were excluded because of too large fibroids or diffuse hypertrophic enlargement of uterus (volume > 220 mL). Although the volumes estimated by the 3-D method were not significantly different (p = 0.126 first measurement, p = 0.561 second measurement), the volumes estimated by the 2-D method were significantly different (p = 0.005 first measurement, p = 0.012 second measurement). The mean error rates of the two 3-D volume measurements by the same observer were 7.4% and 7.9%, and they were 22.2% and 21.0% for the 2-D volume measurements. It may be concluded that the volume of the uterus can be measured more accurately by 3-D US than by 2-D US.