The male urethral sphincter complex revisited: an anatomical concept and its physiological correlate

The anatomy of the male urethral sphincter has not been stable since it was first described more than 150 years ago. Although 18th and 19th century historical descriptions of the urethral sphincter are most accurate and comprehensive, modern textbooks lack details and include inaccuracies and misleading illustrations. This is an attempt to achieve a revised concept of the male urethral sphincter complex.

A thorough review of the English literature in the last 100 years, and of pertinent Germinal publications and textbooks of the 19th and 20th centuries was done. Also, we reviewed urodynamic findings in male patients in whom the urethral sphincters had been expectedly damaged in the proximal or distal part by surgery during the last 20 years.

The current concept of urethral sphincter anatomy does not differ much from that described and illustrated in the 19th century. The disagreement between the historical and recent descriptions is primarily concerned with the cranial extension of the skeletal muscle component and the caudal extension of the smooth muscle component in the urethral wall.

The male urethral sphincter complex is composed of an inner lissosphincter of smooth muscle and an outer rhabdosphincter of skeletal muscle. It extends in the form of a cylinder around the urethra from the vesical orifice to the perineal membrane. While the rhabdosphincter is most marked around the membranous urethra and becomes gradually less distinct toward the bladder, the lissosphincter has its main part at the vesical orifice and is thinner in its further course in the urethra. The lissosphincter is primarily concerned with the function of continence at rest. On the other hand, the rhabdosphincter has a dual genitourinary function, namely active continence during stress conditions and antegrade semen propulsion.