THE FEMALE URETHRAL SPHINCTER - A MORPHOLOGICAL AND TOPOGRAPHICAL STUDY

We reassess the anatomy and topography of the female urethral sphincte r system and its innervation in regard to urethra sparing anterior exe nteration and other surgical procedures. Materials and Methods: Anatom ical and histological studies were performed on 9 fetal specimens and 4 adult cadavers, Using graphics software the anatomical structures of the true pelvis were reconstructed based on computerized tomography c ross sections and digitized histological sections. On the adult cadave rs anterior exenteration was performed to study the implications of th e isolated urethra and its sphincter mechanism. Results: Strata of con nective tissue were found to divide the smooth muscles of the proximal two-thirds of the female urethra into 3 layers. Computer guided S-dim ensional reconstruction of digitized histological sections showed that thin fibers of the pelvic plexus course to this part of the urethra. The majority of these fibers may be preserved by carefully dissecting the bladder neck and the proximal portion of the urethra, leaving the lateral vaginal walls intact, The striated rhabdosphincter, which is i nnervated by fibers of the pudendal nerve, was in the caudal third of the urethra. Conclusions: A well-defined sphincteric structure or sphi ncter could not be anatomically recognized in the bladder neck region. The majority of rhabdosphincter fibers were found in the middle and c audal thirds of the urethra. Thus, in patients undergoing removal of t he bladder neck and part of the proximal portion of the urethra contin ence can be maintained by the remaining urethral sphincter system, pro vided that innervation remains essentially intact.