Transperineal ultrasound for measurement of prostate volume: validation against transrectal ultrasound

We evaluated the transperineal ultrasound method to measure total and central prostate volume compared with the standard transrectal ultrasound.

Healthy men without prostate disease underwent transperineal and transrectal ultrasound at a single session to calculate total and central prostate volume by the ellipsoidal formula from maximal measured dimensions. Reproducibility within and between methods was evaluated by ICC, CV and Bland-Altman plots.

In 13 men measured on 3 occasions within 2 weeks transperineal and transrectal ultrasound had high within method (ICC 0.92 and 0.97, and CV 7.2% and 5.1%, respectively) and between method (ICC 0.98 and CV 5.4%) agreement. Agreement for central prostate volume was good but it was lower within method (ICC 0.74 and 0.73, and CV 20.5% and 20.3%, respectively) and between method (ICC 0.85 and CV 19.7%). Transperineal ultrasound bias was -2.7% for total and -8.9% for central prostate volume. Of 287 healthy men the methods highly correlated for total prostate volume in 245 (ICC 0.92, 95% CI 0.90 to 0.94) and for central prostate volume in 217 (ICC 0.87, 95% CI 0.83 to 0.90). Transperineal ultrasound had minimal bias for total prostate volume (-3.7%, mean -1.0 ml, 95% CI -1.7 to -0.2 ml) and no bias for central prostate volume (-3.0%, mean bias 0.10 ml, 95% CI -0.3 to 0.5 ml). Transperineal ultrasound was more acceptable but it had a higher technical failure rate for total and central prostate volume (13.6% vs 1.4% and 23.7% vs 3.5%, respectively).

Transperineal ultrasound provides an accurate, less invasive and more acceptable alternative but with a higher technical failure rate than transrectal ultrasound, especially for central prostate volume. By trading off acceptability for the failure rate transperineal ultrasound may enhance the feasibility of valid studies requiring repeat prostate volume measurement in asymptomatic men.