The importance of measuring the prostatic transition zone: an anatomical and radiological study

To assess the accuracy and reliability of measurements of the volume of the transition zone (TZ, representing the hypertrophied benign component) and whole prostate by TRUS in patients with BPH or cancer, by comparing the radiological with pathological findings after surgery.

The study comprised 36 patients with prostate cancer undergoing radical prostatectomy and 34 patients with symptomatic BPH treated using retropubic adenectomy. The weights of the radical prostatectomy specimens and of the enucleated adenomas were correlated with the corresponding volumes of the TZ and of the whole prostate, respectively, measured by TRUS using the prolate ellipsoid method.

The mean (sd) TZ volume measured by TRUS was 36.9 (25.48) mL, whereas the weight of the enucleated specimen was 42.7 (33.58) g (correlation coefficient r=0.95, P<0.001). The TRUS estimate of the volume of the whole prostate was 29.2 (9.24) mL, while the radical prostatectomy specimens weighed 34.5 (10.76) g (r=0.78, P<0.001). The variability in the TZ volume estimate ranged from -17% to +18%, whereas the variability for whole prostate was -21% to +30% (P<0.05).

Measurements of the TZ of the prostate by TRUS are more accurate than those for the whole prostate. An assessment of the TZ volume may be sufficiently reliable to be used in the clinical management of BPH and to detect prostate cancer using the prostate-specific antigen density of the TZ as a marker.