Chapter 48

High-Yield Facts

• Intussusception is the commonest cause of intestinal obstruction in children less than 3 years of age.

• Pneumatic or hydrostatic contrast medium enema is the diagnostic imaging procedure of choice for its reduction.

• Although the diagnosis is typically made with ultrasound, the emergency physician can proceed directly to the enema in clinically obvious cases.

• The child can be discharged home from the emergency department following the reduction of the intussusception after a short period of observation.

Etiology and Pathogenesis

Intussusception is the invagination of a segment of intestine into the adjacent distal bowel. The invaginating segment is referred to as the intussusceptum and the distal bowel is the intussuscipiens. It is the most common cause of intestinal obstruction in infants and young children 6 to 36 months of age and the most common abdominal emergency in early childhood. More than 50% of affected children present before 1 year of age, and 80% of cases occur before 2 years. Intussusception is rare before 9 weeks of age, but the incidence increases until about 6 to 7 months of age, where it occurs in about 60 per 100,000 infants. By 1 year of age, the rate is about half of this. Rates are higher among African American and Hispanic infants than among Caucasians. There is a 3:2 male predominance.

Ninety percent of cases are idiopathic, and the remaining 10% are associated with an underlying cause that produces a lead point.1 Cases associated with pathologic causes producing a lead point include Meckel's diverticulum, intestinal polyps, intestinal lymphoma, duplication cysts, Henoch–Schönlein purpura, cystic fibrosis, and benign hamartomas and are much more common in children older than 5 years of age. Intussusception in children younger than 3 months is uncommon but is also highly associated with a pathologic lead point.2 After the age of 3 years, the incidence of a pathologic lead point increases with Meckel's diverticulum, lymphoma, and polyps as the three most commonly found.1 Patients with Burkett's lymphoma as a lead point usually present at an older age (median 10 years) and are almost always ileocolic in location.3 Patients with intussusception caused by pathologic lead points generally fail radiographic reduction and require surgical reduction with resection of the underlying pathology.

In idiopathic cases, the presumed pathogenesis is a preceding viral infection that produces lymphoid hyperplasia in Peyer's patches in the terminal ileum. A strong association with preceding adenovirus infection has been reported.46 The lymphoid hyperplasia is thought to act as the lead point. Ileocolic intussusception is most common, but ileoileocolic, jejunoileal, or colocolic intussusception may also occur.

When the intussusceptum enters the intussuscipiens, its attached mesentery, blood supply, and lymphatic drainage are compromised. The invaginated portion of the intestine develops edema and venous congestion resulting in tissue ischemia. Luminal obstruction also occurs as a result of the intestinal invagination, which increases wall ...

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