Comparison of Transabdominal and Transrectal Ultrasound for Sizing of the Prostate

Abstract

Objective: To compare the accuracy of prostate sizing between pelvic abdominal (PUS) and transrectal (TRUS) ultrasound in a large, diverse cohort of men at our institution. Prostate volume plays a vital role in all types of prostate disease. American Urological Association guidelines (2018) for surgical management of benign prostatic hyperplasia now include consideration of prostate volume measurement prior to surgical intervention. Ultrasound is a quick and radiation-free imaging modality.

Methods: We performed a single-center, retrospective study of 299 patients with prostate sizing between January 1, 2012 and August 31, 2017. Prostate volume was derived from ellipsoid volume calculation using dimensions measured on ultrasound. PUS and TRUS were compared by calculating the Pearson correlation coefficient and intraclass correlation coefficient, and agreement between modalities assessed using the Bland Altman analysis. This analysis was done for the whole sample population as well as for specific groupings according to body mass index, prostate size, and time between exams.

Results: A total of 236 patients had PUS followed by TRUS and met study inclusion criteria. Median age was 63, median prostate specific antigen value prior to PUS was 7.6 ng/mL, and only 20% were white. Mean volume differences between the two modalities for the data (vol_PUS - vol_TRUS) were (-0.3 ± 1.1) cm³. Bland-Altman analysis showed agreement between PUS and TRUS only for prostates ≤ 30 cm³.

Conclusion: For prostates less than 30 cc, we found that PUS is interchangeable with TRUS in estimating prostate volume. However, for larger prostates where size may alter surgical management, we would recommend TRUS or cross-sectional imaging.