Intussusception of the Small Intestine

Intussusception is the invagination of a portion of the intestine into the contiguous distal segment of the enteric tube ( Fig. 71.1 ). It usually occurs in infants at 4 to 10 months of age and is associated with acute enteritis, allergic reactions, and conditions that cause hypermotility. In older persons, intussusception is associated with a polyp or malignancy, an enlarged Peyer patch or diverticulum (e.g., Meckel), and a large number of rare entities that cause intrusion into the bowel.

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Intussusception of the Small Intestine.

Intussusceptions are classified according to the part of the digestive tube that telescopes into the intussuscipiens, the receiving part, including ileoileal, jejunoileal, and ileocolic invaginations. The most common is the ileocolic intussusception. A double invagination, or an intussusception within an intussusception, may also occur, called ileoileocolic. How far the intussusceptum, the part that becomes ensheathed by the more distal portion, enters the intussuscipiens depends on the length and motility of the mesentery. The intussuscipiens can be compressed, after which edema, peritoneal exudation, vascular strangulation, and, finally, intestinal gangrene can develop.

In children, the most common causes of intussusception are associated infections, and in adults, the most common causes are neoplasms, although these primary causes affect the other group as well. Approximately 30% to 50% of small bowel intussusceptions and 50% to 65% of colonic intussusceptions are associated with malignant neoplasms.