Anatomy Modules

Intussusception occurs when one segment of the intestine telescopes into another, usually the ileum into the colon. Constriction of the mesentery results in engorgement of the intussusceptum and bowel ischemia, causing the presenting symptoms. Intussusception occurs most commonly before the age of 2 years and is rare before 2 months. It often develops due to a lead point, which drags one portion of the bowel into another. In infants, it typically occurs due to lymphoid hyperplasia from a viral illness and in older children due to Meckel diverticulum, intestinal polyps, lymphoma, and immunoglobulin A vasculitis (formerly Henoch-Schӧnlein purpura). Intussusception is difficult to diagnose due to the variation in the common presentations of intermittent pain and lethargy. Classically, patients will present with a sudden onset of severe abdominal pain with the legs drawn to the chest and then will appear well until the next episode of pain. Another common presentation is an infant with unexplained lethargy. Although the classic teaching is to look for currant jelly stools, these are rarely present, with occult bleeding occurring in the majority of cases and gross bleeding present in half of the cases. Ultrasound is the initial image modality of choice. When there is a high suspicion of intussusception, patients should undergo an immediate air-contrast enema, which is both diagnostic and therapeutic.

CT of the abdomen and pelvis (A) is an imaging modality that can be helpful in diagnosing intussusception, but it is rarely needed and typically would not be the first diagnostic test in the evaluation. Upper GI series (C) can be helpful in diagnosing volvulus in infants and newborns. Midgut volvulus presents in infants with bilious vomiting and abdominal distension. An X-ray of the abdomen (D) is generally nondiagnostic for intussusception. In severe cases, when bowel perforation complicates intussusception, it may identify abdominal free air.