Sonographic measurements of transition zone of prostate in men with and without benign prostatic hyperplasia.

Modern transrectal ultrasonography is a reliable means of visualizing the transition zone within the prostate gland. We measured the transverse, longitudinal, and anterior diameters and calculated the volume of the prostate and the transition zone in 400 patients. Ninety-seven patients with neither clinical nor sonographic evidence of benign prostatic hyperplasia (BPH) were compared with 108 patients with sonographically apparent BPH. The mean size of the transition zone was 6.14 +/- 3.2 g in the normal group and 24.81 +/- 14.4 g in the BPH group. The size of the transition zone increased significantly in relation to increased age of the patient. Ultrasonography allows accurate measurement of the transition zone and would be useful for documenting changes in the extent of BPH in response to therapy.