CT and MRI features of acute appendicitis
The most specific imaging finding is an abnormal appendix that is typically dilated to ≥ 6 mm and fluid-filled. Visualization of a calcified appendicolith (best seen on CT) with associated periappendiceal inflammatory fat stranding or edema is also highly specific. Other imaging findings may include:
- • Hyperenhancement of the appendiceal wall.
- • Thickening of the appendiceal wall ( ≥ 3 mm), sometimes with low attenuation/high T2-weighted signal intensity submucosal edema in the wall (leading to mural stratification or a “target” sign).
- • Reactive thickening of adjacent cecum or small bowel.
- • Arrowhead-shaped funneling of the cecal apex toward the occluded appendiceal lumen (“arrowhead” sign).
- • A curved soft tissue structure between the cecal lumen and an appendicolith, which is representative of an inflamed cecal or appendiceal wall (“cecal bar” sign).
- • Periappendiceal fluid.
- • Thickening and enhancement of the adjacent parietal peritoneum representing focal peritonitis.
Complications include appendiceal perforation with abscess formation, small bowel obstruction, and mesenteric venous thrombosis.