Coiled-spring sign of appendiceal intussusception.

Appendiceal intussusception has been considered a rare entity that is difficult to diagnose radiographically. However, a characteristic coiled-spring appearance in the cecum with nonfilling of the appendix has been observed on double-contrast barium enema (DCE) examinations in 11 cases of apparent or proved appendiceal intussusception. In two surgically proved cases, the intussusception was precipitated by an appendiceal mucocele and by endometriosis implants in the appendix. In four other cases, the intussusception was transient and the coiled-spring defect in the cecum disappeared with filling of the appendix on the DCE examination (three cases) or on a subsequent barium enema study (one case). The remaining five cases were unproved, although two patients had undergone prior appendectomy and the coiled-spring finding presumably resulted from an intussuscepted appendiceal stump. Only one patient was found to have appendiceal-related symptoms. It appears that appendiceal intussusception often occurs as a transient phenomenon in asymptomatic patients, and that it can be diagnosed on the routine DCE examination by a characteristic coiled-spring defect in the cecum.