Pelvic Floor Muscles

33 Normal bowel continence is a complex process that involves the coordinated interaction between multiple different neuronal pathways and the pelvic and perineal musculature.1 The importance of the anatomic relationships of the pelvic floor in maintaining normal continence has been suggested since the 1950s.2 Yet the complex series of neural and behavioral-mediated interactions, combined with a lack of an ideal study to take all elements into account, makes complete understanding of anorectal anatomy and physiology’s role in preserving continence difficult.3 Complicating this are multiple other factors that have a role in normal regulation such as systemic disease, emotional effects, bowel motility, stool consistency, evacuation efficiency, pelvic floor stability, and sphincter integrity.4 Anorectal physiology testing allows evaluation of the patient with pelvic floor complaints using techniques such as manometry, endoanal ultrasound, electrophysiologic studies, and defecography, all of which help to elucidate anorectal structures and function. A physician with an in-depth knowledge of normal and abnormal anorectal physiology can apply the results in a meaningful way to diagnose and direct therapy. This chapter reviews the current knowledge regarding muscular, neurologic, and mechanical factors.