The effects of transurethral resection on the urodynamics of prostatism

We studied 11 patients urodynamically before and 6 months after transurethral resection of the prostate. Bladder pressures were measured through a fine suprapubic catheter. Urinary stream force and flow rate were measured simultaneously. We calculated values for stream velocity, area of Schäfer's flow control zone, the vena contracta, stream energy loss, total bladder work, total stream power and the passive urethral resistance relationship. After prostatic resection improved voiding was documented in most physiological parameters. However, the total work capacity of the bladder remained constant and appeared to be a fixed property of the healthy bladder. An increase in the volume voided postoperatively was related to an increase in the bladder capacity associated with a decrease in detrusor instability, and was not related to a decrease in residual urine.