Continence mechanism of the isolated female urethra: An anatomical study of the intrapelvic somatic nerves

Purpose: A neuroanatomical study was initiated to gain better insight into the continence mechanism of the isolated urethra in women. Materials and Methods: We performed a detailed gross and histological neuroanatomical study to identify the intrapelvic somatic pathway from the sacral spinal cord to the female urethral sphincter. Gross anatomical dissection was performed in 5 formalin fixed female adult pelvises by tracing the autonomic nerves from the pelvic plexus and the spinal somatic nerves from S2-S4 to the urethral sphincter. Immunohistochemical staining of urethral step sections with a neuropeptide specific antibody was performed to demonstrate the course of the periurethral somatic nerves in relation to the vaginal wall. Results: Our study demonstrated an intrapelvic somatic pathway derived from the S2, S3 and S4 sacral roots, distinct from the peripheral pudendal nerve, supplying the levator ani and the urethra. The somatic nerves travel beneath the endopelvic fascia in close relation to the inferior vascular pedicle of the bladder and are susceptible to injury during radical pelvic surgery. Mixed autonomic fibers from the pelvic plexus travel along the course of the ureter and are also intimately associated with the vascular pedicle of the bladder. Immunohistochemical staining of urethral step sections demonstrated that the periurethral nerves travel in close relation to the lateral and anterior vaginal wall. Conclusions: We believe that the identification of intrapelvic somatic pathways to the urethra provides a basis for developing surgical techniques to presence urethral somatic innervation during radical pelvic surgery in women.