Intussusception

Intussusception is the telescoping of bowel to form an inner loop (intussusceptum) and an outer loop (intussuscipiens). In children 95% of intussusceptions are idiopathic, with lymphoid hyperplasia or hypertrophy postulated as possible causes. In adults, intussusception is usually caused by a neoplasm or other mass acting as a lead point.

Intussusception often presents as small bowel obstruction, with cramping abdominal pain, vomiting, and blood in the stool (currant-jelly stool). With prompt reduction, bowel necrosis can be avoided. Prolonged intussusception may result in bowel necrosis and perforation. Surgery is recommended when radiological reduction is unsuccessful.

Radiological

Plain film may be normal. Often there is an absence of gas in right colon (especially in children). Bowel dilatation signifies obstruction, and intraperitoneal free air signifies perforation. Fluoroscopy demonstrates a coil-spring appearance, with barium trapped between intussusceptum and intussuscipiens. CT scan shows a “bull’s-eye,” which represents the intussusceptum and mesentery surrounded by intussuscipiens. Ultrasound is effective at identifying itussusception. Viewed in the transverse plane, intussusception is seen as a swirled pattern of alternating hyperechogenicity and hypoechogenicity. The longitudinal view demonstrates a “sandwich” appearance of the alternating loops of bowel.

Intussusception.  CT demonstrates edematous bowel wall with a target appearance.  The intussusceptum forms the inner part of the bull’s eye, while the intussuscipiens forms the outer layer.