RESUMO
There are many kinds of unusual presentations or associations and clinical mimics of acute appendicitis, and definitive diagnosis requires knowledge of the imaging findings in some cases. The unusual presentations and associations of acute appendicitis included in this study are perforated appendicitis, acute appendicitis occurring in hernias, acute appendicitis with cystic endosalpingiosis, intussusception of appendix, and acute appendicitis with pregnancy. We also present uncommon gastrointestinal, urinary and gynecologic clinical mimics of acute appendicitis including anomalous congenital band, duplication cysts, giant Meckel's diverticulitis, inflammatory fibroid polyp, renal artery thrombosis, spontaneous urinary extravasation and OHVIRA syndrome. Familiarity with these entities may improve diagnostic accuracy and enable the quickest and most appropriate clinical management.