Utility of Colonoscopy

The gastrointestinal (GI), or digestive, tract extends from mouth to anus. The division of the GI tract into upper and lower is a matter of some confusion and debate. On embryologic grounds, the GI tract should be divided into upper (mouth to major papilla in the duodenum), middle (papilla to mid-transverse colon), and lower (mid-transverse colon to anus) according to the derivation of these 3 areas from the foregut, midgut, and hindgut, respectively. Nevertheless, the GI tract is conventionally divided into upper (mouth to ileum) and lower (cecum to anus). From the point of view of GI bleeding, however, the demarcation between the upper and lower GI tract is the duodenojejunal (DJ) junction; bleeding above the DJ junction is called upper GI bleeding, and that below the DJ junction is called lower GI bleeding. For the purposes of endoscopy, the upper GI tract includes the esophagus, stomach and duodenum (esophagogastroduodenoscopy [EGD] or upper GI endoscopy), and the lower GI tract includes the anus, rectum, colon, and cecum (anoproctocolonoscopy or lower GI endoscopy).