Pressure/cross-sectional area relations in the proximal urethra of healthy males. Part 2: Power generation during voluntary contraction.

The power generation in the proximal urethra during voluntary squeezing was studied in 30 healthy male volunteers aged 23-85 years. Measurements were performed at 5-mm intervals from the bladder neck and beyond the region of high pressure, and the maximum power generation during contraction was calculated at each measurement location. All subjects were further evaluated by means of symptom score, prostatic volume determined by rectal ultrasound, urethral pressure profile, cystometry, and pressure flow. There was a significant variation in power generation along the urethra, with minimum values in the prostatic segments and an approximately 5-fold increase in the high pressure zone. Power generation remained high in the urethral segment distal to the high pressure zone. No correlation between age and power generation could be demonstrated in any part of the urethra. The technique employed does not allow for a differentiation of the individual muscles involved, however, it is suggested that the pelvic floor dominates above the level of the perineal membrane, whereas the striated muscles of the penis may influence the proximal part of the spongious urethra. Physiologically, the contractile capability of the male urethra is probably important for the continence function, as well as it may be of significance for the normal ejaculatory function.