Anorectal and pelvic floor physiology

Abstract

Normal continence and defecation is achieved through a complex interaction between peroral intake, the upper gastrointestinal tract (digestion, secretion and propulsion), and colorectoanal function. Accordingly, continence and defecation can be severely disturbed secondary to abnormal eating patterns or disturbed digestion and propulsion in the small bowel. This is, however, outside the scope of the present chapter. In clinical practice anorectal function cannot be interpreted without considering colonic function, which is therefore included in the following discussion. The main functions of the colorectum are absorption (water, electrolytes, and short-chain fatty acids), transport, and storage. Absorption occurs mainly in the right colon. The main function of the left colon is storage of stools and, together with the rectum, the pelvic floor, and the anal canal, it is responsible for continence and defecation. The mechanisms underlying continence and defecation are interdependent, and in the majority of patients with functional problems both are affected to a varying degree. © 2010 Springer-Verlag Berlin Heidelberg.