Foreign body perforation of the gastrointestinal (GI) tract has diverse clinical manifestations, and the correct preoperative diagnosis is seldom made. We report the case of a 69-year-old woman who experienced severe pain in the right iliac fossa. The presumptive diagnosis was acute purulent appendicitis or diverticulitis. Multidetector computed tomography (MDCT) imaging showed the fish bone perforation of the terminal ileum. A high index of suspicion should always be maintained in order for the correct diagnosis to be made.