Combined electromyography and gas urethral pressure profilometry before and after transurethral resection of the prostate.

Combined electromyographic and gas urethral pressure profilometry was done on 10 consecutive patients before and 3 months after transurethral resection of the prostate. A significant reduction was found postoperatively in the functional urethral length, whereas the maximum urethral closure pressure remained unchanged. Increase in urethral resistance in prostatic obstruction of the posterior urethra was related to the increase in the functional length of the posterior urethra rather than to mechanical occlusion of the urethral lumen. Periurethral striated muscle activity was recorded from the membranous urethra to the urethrovesical junction with the maximal activity located in the membranous urethra. Marked striated muscle activity also was found consistently at the bladder neck.