Determination of prostatic volume with transrectal ultrasound: A study of intra-observer and interobserver variation

Purpose: We assessed the intra-observer and interobserver variation in measurements of prostatic volume using transrectal ultrasound. Materials and Methods: Two volume estimations were performed by 1 observer in 40 patients and by 2 observers in 75. Results: Mean prostatic volumes measured ranged from 18.9 to 87.0 ml. (median 39.8) for 1 observer and from 15.5 to 95.4 ml. (median 42.4) for 2 observers. The mean difference plus or minus standard deviation and limits of agreement between the paired volume estimations were 0.1 +/- 3.3 ml. and -6.5 to 6.7 ml., respectively, for 1 observer, and -0.3 +/- 5.3 ml. and -10.9 to 10.3 ml., respectively, for 2 observers. The mean difference was 9.8% for 2 observers compared to 4.6% for 1. Conclusions: The results show that there is considerable variation in repeated measurements of prostatic volume and the variation is greatest for 2 observers compared to 1 observer.