Appendiceal abscess: pathologic definitions and a diagnostic framework—SIRC/SICUT consensus

BACKGROUND: Appendiceal abscesses are a heterogeneous manifestation of acute appendicitis, with diverse pathological substrates and imaging phenotypes. The lack of standardized definitions hampers cross-study comparability and consistent diagnostic pathways. METHODS: The Italian Society of Surgical Research (SIRC) and the Italian Society of Emergency Surgery and Trauma (SICUT) conducted a four-round modified Delphi, culminating in an in-person consensus conference (Rome, November 6, 2025). A multidisciplinary panel refined the statements on pathological definitions, classifications, and imaging correlates. RESULTS: Consensus was reached on 22 statements. Part 1 reports seven statements that delineate the spectrum from uncomplicated to complicated appendicitis (phlegmonous, gangrenous, and perforated) and distinguishes appendiceal abscesses from appendiceal masses. An imaging framework centered on CT descriptors was used to support consistent radiology-pathology correlations. CONCLUSIONS: These statements provide a unified taxonomy and diagnostic framework for appendiceal abscesses and related entities, improving interdisciplinary communication, and enabling cross-study comparability.