Figure 3. Perforated tip appendicitis. 70-year-old male with right lower quadrant pain. (a) CT demonstrates a round fluid collection mimicking a distended gallbladder (large arrow) with an apparent gall stone within it (small arrow). (b) At a slightly different level the collapsed gallbladder with mucosal enhancement is identified (small arrow) separate but adjacent to the fluid collection (large arrow). (c) The appendix near its origin is normal without inflammatory changes around it (arrow). (d) At a level between the pericholecystic collection and the normal appendicial origin, inflammatory changes begin to be noted surrounding the appendix (arrow). At surgery the retrocaecal appendix extended cephalad with perforated tip appendicitis and abscess formation adjacent to the gallbladder, mimicking complicated cholecystitis.