REASONS FOR THE WEAK CORRELATION BETWEEN PROSTATE VOLUME AND URETHRALRESISTANCE PARAMETERS IN PATIENTS WITH PROSTATISM

In an attempt to increase our understanding of the clinical syndrome o f benign prostatic hyperplasia (BPH) an analysis was made of the assoc iation between prostate volume as measured by transrectal ultrasound a nd several reported urodynamically determined urethral resistance para meters. Two types of obstruction can be recognized on the basis of uro dynamic data: a compressive type characterized by a high urethral open ing pressure and a prolonged isovolumetric contraction phase before ur ine flow can start, and a constrictive type characterized by a normal opening pressure and an increased slope of the urethral resistance rel ation. A combination of both types is often seen in BPH. In our study, parameters that selectively quantify compression correlate weakly to moderately with prostate volume, whereas parameters that mainly quanti fy constriction do not correlate at all with prostate volume. Paramete rs that combine a measure for compression and constriction correlate l ess well with prostate volume than parameters that mainly quantify com pression. The variation in prostate volume was found to determine the variation in urethral resistance by 15% or less depending on the param eter used, which implies that the different pathophysiological mechani sms that can increase urethral resistance in the complex process of cl inical BPH are mainly determined by factors other than the volume of t he prostate. Thus, despite the lack. of correlation between prostate v olume and urethral resistance, pressure-flow studies and the determina tion of urethral resistance parameters provide a valuable contribution to the understanding of the pathophysiology of voiding dysfunction in men with symptoms of prostatism.