The fascial involvement score retains diagnostic value for complicated appendicitis on CT when specific signs are absent.

OBJECTIVE: To evaluate the diagnostic performance of the fascial involvement score in predicting complicated appendicitis among patients without extraluminal air, extraluminal appendicolith, or abscess on CT. METHODS: This single-center retrospective study initially included 307 patients with surgically and/or pathologically confirmed appendicitis who underwent unenhanced CT and lacked the three specific CT signs of complicated appendicitis. Of these, 287 patients had assessable fascial structures and formed the primary analytic sample for the fascial involvement score. The fascial involvement score, appendiceal diameter, and laboratory markers were assessed. Multivariate logistic regression and ROC analyses were performed to identify independent predictors of complicated appendicitis. RESULTS: Of the 307 patients, 120 (39.1%) had complicated appendicitis. The fascial involvement score (OR: 1.673; 95% CI 1.285-2.178), appendiceal diameter (OR: 1.163; 95% CI 1.033-1.309), and C-reactive protein (CRP) level (OR: 1.011; 95% CI 1.005-1.016) were independent predictors of complicated appendicitis. The optimal cutoff for the fascial involvement score was 1.5 (AUC: 0.699). Combining the fascial involvement score with CRP (≥ 24.1 mg/L) achieved a numerically higher AUC (0.702) compared with other combinations, with a specificity of 81.3% and a sensitivity of 59.2%. CONCLUSION: The fascial involvement score is a useful adjunctive CT marker for identifying complicated appendicitis even in the absence of overt imaging signs. Combining it with CRP enhances diagnostic specificity and may guide timely surgical intervention.