Differentiation of perforated from nonperforated appendicitis at CT.

Objective: To evaluate the sensitivity and specificity of five computed tomographic (CT) criteria in the differentiation of perforated from nonperforated appendicitis.

Methods: CT scans of 94 patients with surgically proven appendicitis were classified on review as showing perforation if one of five CT findings was present. The authors calculated the sensitivity and specificity for each finding by comparing the predicted outcome to the surgical and pathologic outcome.

Results: The perforated group comprised 39 patients and the nonperforated group comprised 55 patients. Sensitivity for abscess, phlegmon, extraluminal air, extraluminal appendicolith, and focal defect in enhancing appendiceal wall individually were 36%, 46%, 36%, 21%, and 64%, respectively. Sensitivity for any one of the five findings was 94.9%. Specificities were 100% for all findings except for phlegmon (95%). Groups differed with respect to age: 47 years +/- 19 (mean +/- SD) for perforated appendicitis and 30 years +/- 13 for nonperforated appendicitis (P <.001). Groups also differed with respect to appendiceal diameter: 15 mm +/- 4.9 for perforated appendicitis and 12 mm +/- 3.3 for nonperforated appendicitis (P =.049).

Conclusions: A dedicated search for five specific CT findings allowed an overall sensitivity of 94.9% for perforated appendicitis. Among findings with 100% specificity, a focal defect in the enhancing appendiceal wall achieved the highest sensitivity.