Sonographic diagnosis of intussusception of the appendix vermiformis.

We present 2 cases of intussusception of the appendix vermiformis (IAV) in children. Sonographic examination demonstrated a lead point within a characteristic multiconcentric ring sign, and longitudinal sonograms showed the inverted appendix protruding into the cecal lumen. A contrast-enema study, using a water-soluble contrast medium, was performed in each case, and a "coiled-spring" sign or "spiral shell" appearance confirmed the diagnosis. A surgical reduction of the appendix and an appendectomy were performed in each case.