One type of duplex appendix: horseshoe appendix.

A horseshoe appendix is a subtype of duplex appendix, in which the appendix is shaped like a circle that may lead to an internal hernia and result in intestinal necrosis. This subtype is extremely rare, with only 13 cases reported worldwide to date, and easily triggers a series of medico-legal consequences due to the neglect of another infection base of the appendix. We describe a 22-year-old man who presented with a 3-day history of fever and was diagnosed with pneumonia. After receiving antibiotics for 3 days in the Department of Pneumology, he was found to have a periappendiceal abscess. He underwent appendectomy after 3 days of conservative treatment failure in the Department of General Surgery. During the operation, we found that he had a horseshoe appendix with the two bases forming a circle, each communicating with the cecum. We provide a review of 13 cases presented in the literature, with a discussion of the clinical features, diagnosis, and surgical approach of the horseshoe appendix to make the general surgeon get a clear concept of this type of appendicitis.