ABSTRACT
Absorption and digestion of nutrients primarily take place in the small intestine. However, the colon still plays a major role in the absorption of some nutrients and in the regulation of water and electrolyte balance. The proximal colon processes some complex carbohydrates and proteins resistant to digestion and absorption in the small intestine. Nutrients are salvaged from the products by fermentation by over 400 species of bacteria, predominately obligate anaerobes. The colon relies on contractions to propel luminal content distally from the caecum to the rectum, promoting absorption and the mixing of colonic content. Colonic dysmotility can be evaluated by colonic transit time. Progression time traditionally has been assessed with radio-opaque markers and whole-gut transit with colonic scintigraphy. Colonic scintigraphy can be used as an alternative to radio-opaque markers. Gut microbiota are essential for the development of gut mucosal immunity.
