The appendix sign: A radiographic marker for irreducible intussusception

Purpose: Radiographic reduction (hydrostatic or pneumatic) of intussusception has become the standard of care in the pediatric population with success rates of more than 80%. Identification of those patients who are likely to fail nonoperative management could lead to earlier operation, a reduction in radiation exposure, and a decreased risk for complications after repeated attempts at enema reduction. During successful radiographic reduction, the small bowel is almost always visualized before the appendix. Visualization of the appendix before visualization of the small bowel during a successful reduction of an intussusception is a rare event. We report a new radiographic sign that we have termed the appendix sign (radiographic visualization of the appendix without reflux of air or contrast into the small intestine), which we hypothesize may have association with failure of nonoperative management. Method: We performed a retrospective review of the last 12 years of irreducible intussusception. The associated studies were then reviewed to examine the incidence, sensitivity, and specificity of this radiographic finding. Results: Ninety-one cases of intussusception were identified and had films available for review. Seventy-seven (76%) of the studies included the appropriate image. The appendix sign was visualized in 14 studies for an incidence of 18%. Of 14 patients, 10 failed enema reduction (positive predictive value, 71%). The sensitivity of the appendix sign is 43%. The specificity of the sign is 93%. Conclusions: Our experience suggests that the presence of an appendix sign is associated with failing enema reduction of an intussusception and may be useful as a marker for determining the end point for further attempts at radiographic reduction.