Anal Bleeding Anatomy
To better understand rectal bleeding, it helps to understand the anatomy of the colon, rectum and anus.
The large intestine is also known as the colon. It is the last portion of the intestine.
The colon has several parts, including:
- The portion of the colon that connects to the ileum (small intestine). The appendix is a finger-like pouch that comes off of the cecum.
- Ascending colon:
- The first section after the small intestine, located on the right side
- Transverse colon:
- Sits horizontally across the upper abdomen
- Descending colon:
- Located on the left side of the abdomen
- A short, S-shaped section above the rectum
- The lowest internal part of the colon
- Farrell JJ, Friedman LS. Review article: the management of lower gastrointestinal bleeding. Aliment Pharmacol Ther. 2005 Jun 1;21(11):1281-98. 
- Hoedema RE, Luchtefeld MA. The management of lower gastrointestinal hemorrhage. Dis Colon Rectum. 2005 Nov;48(11):2010-24. 
- Olds GD, Cooper GS, Chak A, Sivak MV Jr, Chitale AA, Wong RC. The yield of bleeding scans in acute lower gastrointestinal hemorrhage. J Clin Gastroenterol. 2005 Apr;39(4):273-7.