Physiology and function of the colon

Colon plays a vital role in fluid and electrolyte homeostasis, digestion of food, absorption of nutrients, propulsion of intestinal contents and ultimately expulsion of waste products. A keen understanding of colonic function is therefore required for the successful management of gastrointestinal disease. This chapter describes an anatomy of the colon. The colon has evolved to perform four major functions: propulsion of colonic contents towards the rectum and anus for eventual expulsion, absorption of water and electrolytes from intraluminal contents, absorption of short-chain fatty acids produced by resident symbiotic bacteria and defaecation. Two radiological methods for the assessment of transit are routinely employed to look indirectly at colonic motor function: radiopaque marker studies and colonic scintigraphy. Colonic manometry can be employed to look directly at colonic contractile activity.