Intussusception is the most common cause of bowel obstruction in children after the newborn period. The incidence peaks in late infancy but may be seen at any age. Intussusception occurs when a part of the bowel collapses into the segment immediately distal to it, much in the way that a telescope collapses upon itself. The immediate consequence is restriction of venous flow, resulting in engorgement of the involved section and subsequent bowel obstruction. Arterial flow may eventually be compromised, leading to necrotic bowel and perforation. Untreated intussusception may lead to peritonitis, sepsis, and death. However, an early diagnosis minimizes the occurrences of these complications.

In children younger than 5 years, approximately 75% of classic ileocolic intussusceptions are idiopathic. After that age, the presence of a lead point is more common. The lead point may be a Meckel diverticulum, lymphoma, duplication, hypertrophied lymphoid tissue, or associated with a bowel wall lesion from Henoch-Schönlein purpura.

The initial history may be suggestive of gastroenteritis, with vomiting and abdominal pain as the presenting symptoms. However, in cases of intussusception, the vomiting may be clear initially, but it often becomes bilious with time. Bilious emesis in any child implies the presence of a bowel obstruction until proven otherwise. Also, in intussusception, the pain is more severe and classically occurs in waves every 10 to 20 minutes. The stool may be normal, have the appearance of currant jelly, or be grossly bloody. A history of lethargy is common, especially between bouts of pain. A viral syndrome frequently precedes intussusception.