Transrectal ultrasonic volumetry of the prostate: in vivo comparison of different methods

In order to assess the accuracy of various volumetric methods for screening and follow-up of prostatic disease, total prostate volume and inner zone volume were measured by transrectal ultrasonography in a screening population of 716 men. Semiplanimetric and caliper formula methods were compared with step section planimetry as the gold standard. Planimetric volumetry of the prostate is regarded as the most reproducible method for individual follow-up of total gland and inner zone volume. The prolate spheroid formula is the most reproducible of caliper formula methods for both volumes. In this study the elliptical volume was, however, more accurate than the prolate spheroid volume of the total gland, as the correlation coefficient between total elliptical volume and planimetry was higher compared to the prolate spheroid volume (0.89 vs. 0.83), and the standard deviation of the mean volumetric difference smaller. The mean total prolate spheroid volume resembled the mean total planimetric volume better than the elliptical volume did, as the mean volumetric difference was smaller. For measurement of the inner zone volume the prolate spheroid volume was more accurate that the elliptical volume. The correlation coefficient between length and planimetric volume was similar to that of width and height, which accounted for more accuracy of the elliptical volume that of the prolate spheroid volume in larger prostates. The elliptical volume might be used for incidental volumetric measurements of the total gland, and for comparison of different individuals, e.g., in preoperative evaluation or screening studies.