Relation between urethral elasticity and bladder outlet obstruction and histologic composition of the prostate in patients with benign prostatic hyperplasia

Objectives. In benign prostatic hyperplasia (BPH), bladder outlet obstructi on is caused by mechanical blockage resulting from an enlarged prostate, an d by the increased tone of prostatic smooth muscle. In patients with obstru ctive BPH, the prostatic urethra urodynamically corresponds to the flow-con trolling zone (FCZ). We sought to investigate the relation between the obst ruction and elastic properties of the FCZ and the histologic composition of the prostate in symptomatic patients with BPH. Methods. The grade of infravesical obstruction was classified according to preoperative pressure-flow data from 30 men with symptomatic BPH, and the e lastic properties of the FCZ were evaluated as the mean elastance, which wa s calculated using the three-parameter model. The area densities of smooth muscle, fibrous tissue, epithelium, and lumen were determined by quantitati ve morphometry, using BPH tissue obtained by transurethral resection. Results. The area density of smooth muscle had a negative correlation with mean elastance (rho = -0.50, P <0.01), the linear passive urethral resistan ce relation (rho = -0.45, P <0.05), and the group-specific urethral resista nce factor (rho = -0.39, P <0.05). No other histologic element was correlat ed with these variables. Conclusions. Our results suggest that urethral elasticity and bladder outle t obstruction grade are influenced by the relative content of smooth muscle within the prostate in patients with BPH. UROLOGY 53: 1149-1153, 1999. (C) 1999, Elsevier Science Inc. All rights reserved.