History (HX): A 26 years old man , Fever, abdominal pain, vomiting    

Findings: 

-Large cavity with thick enhanced wall in RLQ
-Dilated appendix with thickened wall
-Small appendicolith
-Cecal apex thickening     

Diagnostic (DX): Periappendiceal abscess, appendicolith

Discussion: CT features in typical cases of acute aapendicitis include an abnormal appendix, periappendiceal inflammation and changes in the cecal apex. The abnormal appendix is distended and nonopacified showing a diameter wider than 6 mm, wall thickening and enhancement after contrast infusion, and appendicoliths, periapendiceal inflammatory changes include fat stranding, phlegmon, fluid, free air bubbles, abscess and adenopathy changes into cecal apex include focal cecal apex thickening and arrowhead sign and a cecal bar, the arrowhead sign indicates a collection of contrast material between each side of the cecal apical thickening and the cecal bar is a straight or slightly curved baud of inflamed soft tissue that separated proximal calcified appendicolith from cecal lumen. The presence of appendicolith does not always indicate appendicitis and may be an incidental finding.