IS Case 98: Intussusception with incomplete reduction
Imaging Sciences URMC 2008
Publication Date: 2009-05-20
A single AP view of the abdomen demonstrates multiple dilated loops of small bowel and absence of bowel gas in the right upper quadrant, suggestive of mass effect. Fluoroscopic views of the abdomen during air enema demonstrate a filling defect of the transverse colon with persistent intussusception in a redundant colon/hepatic flexure after attempted reduction. Repeat air enema shows further but incomplete reduction of intussusception.
Intussusception occurs when a portion of the alimentary tract is telescoped into adjacent segment. This is the most common cause of intestinal obstruction between 3 months and 6 years of age. The cause of most intussusceptions is unknown, but is thought that a gastrointestinal infection or the introduction of new food proteins results in swollen Peyer patches in the terminal ileum which may subsequently prolapse into the colon, thus causing an intussusception. In a small fraction of patients, recognizable lead points are found, such as Meckel diverticulum, intestinal polyp, neurofibroma, intestinal duplication, hemangioma, or malignant conditions such as lymphoma.
Intussusceptions are most often ileocolic and ileoileocolic, less commonly cecal colic, and rarely exclusive exclusively ileal. Very rarely, the appendix forms the apex of an intussusception. With intussusception, venous return is compromised resulting in engorgement, edema, and bleeding from the mucosa. If not reduced, it may lead to bowel strangulation, intestinal gangrene, and shock.
Patients may present with paroxysmal colicky pain accompanied by straining efforts and flexion of the knees. Without reduction, the infant may become progressively weakened and lethargic, and fever and a shock-like state may ensue. Vomiting occurs more frequently early in the course, with bilious vomiting occurring later on. There is paucity of flatus and infrequent small stools, with 60% of patients passing red blood and mucous, the so-called current jelly stool. Physical examination may reveal a slightly tender sausage shaped mass of the right upper abdomen.
The classic clinical triad of abdominal pain, current jelly stools, and palpable abdominal mass is present in less than 50% of patients with intussusception. Imaging, including plain film, enema examination, and ultrasound, is therefore required in the majority of cases to establish the diagnosis. Plain film demonstrates a right upper quadrant soft tissue mass effacing the adjacent hepatic contour. Other signs included reduced air in the small intestine gasless abdomen, displaced appendix, and small bowel obstruction. The most specific plain film signs are the target sign, which is a soft tissue mass that contains concentric circular areas of lucency, and the meniscus sign, which is a crescent of gas within the colonic lumen that outlines the apex of the intussusception. The classic signs seen on barium examination include the meniscus sign and coiled spring sign. The meniscus sign is produced by the rounded apex of the intussusceptum protruding into the column of contrast material, and coiled spring sign is produced by edematous mucosal folds that are outlined by contrast material in the lumen of the colon. Ultrasound has a high reported sensitivity for diagnosis (98% to 100%). Reported findings include a donut or pseudokidney appearance composed of hypoechoic outer ring and hyperechoic center.
Treatment is enema therapy or surgical. Enema therapies include barium enema, water soluble contrast enema, air enema, and US-guided saline enema. Each has advantages and disadvantages based on success rate, radiation exposure, and rate of perforation. Surgery is reserved for a very ill child or after failed enema therapy.
Air enema has an excellent success rate (70%-95%) and less x-ray exposure than with barium enema. Delayed, repeated reduction attempts are safe and effective and should be considered when the initial attempt manages to move the inutussusceptum and the patient remains clinically stable. Some authors report increased perforation rate with air enema compared to barium enema.
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