Studies on the sphincteric system located distally in the urethra: the external urethral sphincter revisited.

Anatomical, physiological and clinical studies were done on the sphincteric system located distally in the male urethra. Results revealed that urinary continence after radical transurethral prostatectomy is attributed to the true external urethral sphincter, which is defined anatomically as intrinsic striated muscle of the urethra. Urodynamic and electrophysiologic data suggested that this external sphincter is influenced directly and more predominantly by the autonomic alpha-adrenergic system than by the somatic innervation system. Clinical experiences in the management of external sphincter disorder in neurogenic vesical dysfunction by pharmacologic manipulation of the alpha-adrenergic system were presented. A plea is made for consideration of this revised concept of the external sphincter in understanding various pathophysiology of the lower urinary tract.