Physiological mechanisms underlying fecal continence

Abstract The machinery maintaining fecal continence prevents involuntary loss of stool and is based on synchronized interplay of multiple voluntary and involuntary mechanisms, dependent on cooperation between motor responses of the musculature of the colon, pelvic floor and anorectum, and on sensory and motor neural pathways. Knowledge of the physiology of fecal continence is key towards understanding the pathophysiology of fecal incontinence. The idea that involuntary contraction of the internal anal sphincter is the primary mechanism of continence and that external anal sphincter supports continence only by voluntary contraction is outdated. Other mechanisms have come to the forefront and they have significantelly changed viewpoints on the mechanisms of continence and incontinence. And so for instance, involuntary contractions of the external anal sphincter, the puborectal muscle and the sphincter of O'Beirne have been proven to play a role in fecal continence. Also, retrograde propagating cyclic motor patterns in the sigmoid and rectum promote retrograde transit to prevent continuous flow of content into the anal canal. With this review we aim to give an overview of primary and secondary mechanisms controlling fecal continence and evaluate the strenght of evidence.