Colon

The colon consists of four sections: the ascending colon, the transverse colon, the descending colon, and the sigmoid colon (the proximal colon usually refers to the ascending colon and transverse colon). The cecum, colon, rectum and anal canal make up the large intestine.

Locations along the colon are:

• Ascending colon 

• The right (hepatic) colic flexure

• The transverse colon 

• The transverse mesocolon

• The left (splenic) colic flexure

• The descending colon

• The sigmoid colon 

The parts of the colon are either in the abdominal cavity (intraperitoneal) or behind it in the retroperitoneum. Retroperitoneal organs in general do not have a complete covering of peritoneum, so they are fixed in location. Intraperitoneal organs are completely surrounded by peritoneum and are therefore mobile. Of the colon, the ascending colon, descending colon and rectum are retroperitoneal, while the caecum, appendix, transverse colon and sigmoid colon are intraperitoneal. This is important as it affects which organs can be easily accessed during surgery, such as a laparotomy.