This condition results in an obstruction of the intestine caused by part of the gut being pulled inward (like a telescope). Strangulation of the segment of intestine which has been pulled inside the lower intestinal segment can occur.

The pressure created by the two walls of the intestine pressing together causes inflammation, swelling and decreased blood flow. Death of bowel tissue can occur with significant bleeding, perforation, and infection. Shock and dehydration can occur very rapidly.

The cause of intussusception is not known although viral infections may be a possible cause. Sometimes a mass like a lymph node, a polyp, or a tumor can serve as a lead point triggering the telescoping of the gut.

Recently, it has been suggested that a new vaccine for Rotavirus is associated with an increased incidence of intussusception. The vaccine was subsequently pulled from the market. Intussusception affects boys 3 times more often than girls. Most cases occur in children between 5 months and 1 year of age.

Intussusception often begins with sudden loud and pained crying caused by abdominal pain. The pain is colicky and intermittent (not continuous), but recurs frequently increasing in both intensity and duration.

As the condition progresses the infant may become weak and then shocky. Vomiting and fever are common and about half of the infants will pass bloody, mucus-like stool sometimes referred to as a "currant jelly" stool.

Early diagnosis is important in order to salvage both the bowel and the infant.

• Intermittent abdominal pain manifested in an infant by drawing knees to chest with crying with some pain-free periods
• Vomiting
• Stool mixed with blood and mucus ("currant jelly" stool)
• Shock (pale color, lethargy, sweating)
• Fever

• An abdominal X-ray may suggest obstruction.
• A barium enema may show telescoping bowel.

Perforation with infection is a complication.