THE PRESACRAL NERVE: ITS ANATOMY, PHYSIOLOGY, PATHOLOGY, AND SURGERY

Anatomic relationships of the pelvic autonomic nervous system in female cadavers: clinical applications to pelvic surgery

BACKGROUND

The integrity of the pelvic autonomic nervous system is essential for proper bowel, bladder, and sexual function.

OBJECTIVE

The purpose of this study was to characterize the anatomic path of the pelvic autonomic system and to examine relationships to clinically useful landmarks.

STUDY DESIGN

Detailed dissections were performed in 17 female cadavers. Relationships of the superior hypogastric plexus to aortic bifurcation and midpoint of sacral promontory were examined; the length and width of plexus was documented. Path and width of right and left hypogastric nerves were recorded. The origin and course of the pelvic splanchnic nerves were documented. Individual nerve tissue that contributed to the inferior hypogastric plexus was noted. Relative position of nerves to arteries, viscera, and ligaments was documented. In a subset of specimens, biopsy specimens were obtained to confirm gross findings by histologic analysis. Descriptive statistics were used for data analyses and reporting.

RESULTS

In all specimens, the superior hypogastric plexus was embedded in a connective tissue sheet within the presacral space, just below the peritoneum. In 14 of 17 specimens (82.4%), the plexus formed a median distance of 21.3 mm (range, 9-40 mm) below aortic bifurcation; in the remaining specimens, it formed a median distance of 25.3 mm (range, 20.5-30 mm) above bifurcation. In 58.8% of specimens, the superior hypogastric plexus was positioned to the left of midline. The median length and width of the plexus was 39.5 (range, 11.5-68) mm and 9 (range, 2.5-15) mm, respectively. A right and left hypogastric nerve was identified in all specimens and formed a median distance of 23 mm (range, 5-32 mm) below the promontory. The median width of the hypogastric nerve was 3.5 mm (range, 3-4.5 mm) on the right and 3.5 mm (range, 2-6.5 mm) on the left. The median distance from midportion of uterosacral ligament to the closest nerve branch was 0.5 mm (range, 0-4.5 mm) on right and 0 mm (range, 0-27.5 mm) on left. In all specimens, the inferior hypogastric plexus was formed by contributions from the hypogastric nerves and branches from S3 and S4. In 47.1% of hemipelvises, S2 branches contributed to the plexus. The sacral sympathetic trunk contributed to the plexus in 16 of 34 hemipelvises where this structure was identified. The inferior hypogastric plexus formed 1-3 cm lateral to the rectum and upper third of the vagina. From this plexus, 1-3 discrete branches coursed deep to the ureter toward the bladder. A uterine branch that coursed superficial to the ureter followed the ascending branch of the uterine artery. An S4 branch was found directly attaching to lateral walls of the rectum in 53% of specimens. Pelvic splanchnic nerves merged into the inferior hypogastric plexus on the lower and medial surface of the coccygeus muscle. Histologic analysis confirmed neural tissue in all tissues that were sampled.

CONCLUSION

Anatomic variability and inability to visualize the small caliber fibers that comprise the inferior hypogastric plexus grossly likely underlines the reasons that some postoperative visceral and sexual dysfunction occur in spite of careful dissection and adequate surgical technique. These findings highlight the importance of a discussion with patients about the risks that are associated with interrupting autonomic fibers during the preoperative consent.

Slow transit constipation: a disorder of pelvic autonomic nerves?

Slow transit constipation (STC) is a severe motility disorder, which in the majority of cases is of unknown etiology. In some, symptoms arise de novo in childhood, but a proportion of patients present in later life, including after pelvic surgery or childbirth. Our aims were: (1) to describe our current knowledge of the anatomy and function of the pelvic autonomic nerves with respect to colonic motility (experimental and observational studies); (2) to discuss evidence for pelvic nerve injury in STC arising after pelvic surgery or childbirth; and (3), on the basis that such patients are clinically indistinguishable from patients with chronic idiopathic STC, to evaluate whether there is evidence that pelvic autonomic neuropathy has an etiologic role in patients with chronic idiopathic STC. The outcome was as follows: (1) The clear importance of the pelvic autonomic nerves in colonic motor function is documented. (2) While there is an association between pelvic surgery and childbirth, and the onset of STC, there is little direct anatomical evidence that pelvic denervation occurs in these patients. However the phenotype of these patients is similar to results of experimental and observational studies. (3) Clinical, physiological, and histological similarities exist between patients whose symptoms arose following pelvic intervention and those whose symptoms arise de novo (idiopathic). We further present evidence for possible pathogenetic mechanisms underlying pelvic autonomic neuropathy in chronic idiopathic STC.

The colon, anorectum, and spinal cord patient. A review of the functional alterations of the denervated hindgut

As humans have become more mechanized, the number of persons sustaining spinal cord injuries resulting in quadriplegia or paraplegia has increased. Because colorectal function is modulated by a combination of neural, hormonal, and luminal influences, many of the normal regulatory mechanisms remain intact in patients with spinal cord injuries. Management of these patients, however, requires an understanding of altered function in the denervated hindgut. The foregut and midgut are innervated by parasympathetic fibers in the vagus and sympathetic fibers from the lower six thoracic vertebra. In contrast, the hindgut is innervated by parasympathetic fibers arising from the sacral plexus and sympathetic fibers from the lumbar spinal column. Consequently, in most spinal cord injuries, the foregut and midgut remain normally innervated whereas the hindgut looses input from cerebral and spinal cord sources. In high cord lesions this results in decreased colonic motility. In low cord injuries there is loss of inhibitory influences that normally down-regulate left colonic and rectosigmoid sphincter activity. This increased motility causes a loss of left colonic compliance and increases left colonic transit, thus leading to chronic constipation. At the same time in both high and low cord injuries, reflex activity of the anorectum is left unregulated by cerebral input. Once stimulated by distention, the rectum spontaneously evacuates its contents. Thus, fecal impaction and incontinence in these patients principally results from loss of inhibitory influences on rectosigmoid sphincter activity and on rectal reflex activity.