To better understand intussusception, it helps to understand the anatomy of the gastrointestinal tract.
The esophagus is a muscular tube that propels food down to the stomach. The stomach is the most dilated portion of the digestive tube, situated between the esophagus and the beginning of the small intestine (duodenum). It lies in the upper central portion of the abdomen (above the umbilicus) and to the left of the midline. The stomach produces gastric juice (acidic), which serves to breakdown proteins.
The intestine is a long, continuous, tube inside the body. It lets the body absorb nutrients from food and liquids. The intestine is about 22 feet long. It includes the large intestine (colon) and the small intestine.
The small intestine has three parts:
- Connects to the stomach
- Middle portion of the small intestine
- Lower portion of the small intestine that connects to the cecum (first part of the large intestine)
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
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- Daneman A, Navarro O. Intussusception. Part 1: a review of diagnostic approaches. Pediatr Radiol. 2003 Feb;33(2):79-85. 
- Yalamarthi S, Smith RC. Adult intussusception: case reports and review of literature. Postgrad Med J. 2005 Mar;81(953):174-7.