The technique of inversion-ligation appendectomy is used by some surgeons to eliminate the risk of peritoneal contamination as the result of incidental appendectomy during an otherwise clean surgical procedure. In most cases, the intussuscepted appendix necroses and sloughs into the cecum after several days. We present the first report of the ultrasonographic appearance of a retained, inflamed appendix, which occurred in a neutropenic pediatric patient 15 months after inversion appendectomy. Our case illustrates the importance of a complete surgical history for the interpretation of abnormal sonographic findings of the cecum.