Yersinia enterocolitica is a Gram-negative organism responsible of acute infective ulcerative enterocolitis. Symptoms are fever, diarrhea, and right lower quadrant pain. Infective diseases affect the terminal ileum and colon showing thickened folds plus ulceration, with lymphoid nodular hyperplasia. A differential diagnosis with acute appendicitis is not always possible based on clinical findings. However CT is useful to detect the normal appearance of the appendix identifying inflammatory changes of terminal ileum and cecum. A differential diagnosis based on imaging findings with Crohn’s disease is not easy to perform. Some CT findings may indicate the lack of chronic inflammation of perivisceral fat (lack of fatty proliferation) and suggest an acute origin (marked perivisceral fat stranding) and thickening of cecal folds.