Mucosal enhancement defect of appendix. An axial CT image of a 20-year-old man presenting with a 9-h onset of right lower quadrant pain, elevated white blood cell counts (19,150 cells/mm3) and neutrophilia (85% neutrophils) shows a dilated appendix with focal defect at the anteromedial wall (arrow). Gangrenous appendicitis was confirmed at surgery and histopathology