Preoperative CT detection of appendiceal neoplasms in suspected acute appendicitis using a simple...

Appendiceal neoplasms (ANs) may mimic acute appendicitis (AA), making preoperative recognition difficult in emergency settings. We aimed to derive and externally validate a simple non-contrast CT criterion combining appendiceal diameter and fecalith obstruction status for differentiating AN from AA.

This multicenter retrospective case-control study included adults who underwent appendectomy at four tertiary hospitals from January 2013 to June 2025. Histopathology after centralized re-review served as the reference standard. In the derivation cohort, receiver operating characteristic analysis was used to determine the optimal cutoff for maximum appendiceal diameter. A locked criterion of significantly enlarged appendiceal diameter (SEAD) without fecalith obstruction was then applied unchanged to the validation cohorts and reader-based validation subsets. Its diagnostic performance was also compared with that of the original CT reports.

The final analytic cohort included 292 patients with ANs and 876 controls with AA. A cutoff of 12.48 mm defined SEAD. In the derivation cohort, SEAD without fecalith obstruction yielded an AUC of 0.76 (95% CI, 0.71-0.80), with 64.1% sensitivity and 87.0% specificity. In Center 2, the AUC was 0.82 (95% CI, 0.77-0.87), and in the pooled Centers 3 and 4 cohort it was 0.73 (95% CI, 0.66-0.81), without significant differences versus the derivation cohort (p = 0.051 and p = 0.598). Reader-based AUCs were 0.80, 0.76, and 0.72, without significant between-reader differences (all p > 0.05). Compared with original CT reports, the criterion substantially improved preoperative AN detection across cohorts (all p < 0.001).

A predefined non-contrast CT criterion of SEAD without fecalith obstruction may facilitate preoperative identification of AN in patients with presumed AA.