Stage-Oriented CT Classification and Intermodal Evolution Model in Hepatic Alveolar Echinococcosis

BACKGROUND: Alveolar echinococcosis (AE) is one of the most dangerous human parasitoses. The main site of disease manifestation is the liver (about 98 %). The Echinococcus Multilocularis Ulm Classification for Computed Tomography (EMUC-CT), presented in 2016, was the first compilation of CT morphological criteria of hepatic AE. Studies based on EMUC-CT made it possible to draw conclusions about the development of the lesions in the course of disease beyond purely diagnostic typing. Among the most important findings of these precursor studies was that EMUC-CT type IV presented as an initial lesion, whereas EMUC-CT type III lesions were mostly associated with an advanced disease constellation. An intermodal view of image morphological criteria provides further multi-layered indications for lesion evolution. METHOD: With the “Alveolar Echinococcosis Ulm Classification” (AEUC), a revision of the previous EMUC-CT was carried out with stage-oriented reorganization of the primary morphologies. Furthermore, an intermodal classification scheme for the evolution of hepatic AE lesions based on AEUC, MRI Kodama classification, and aspects of ultrasound could be outlined. RESULTS: The first stage-oriented CT classification of hepatic AE “AEUC” is based with respect to its lesion characterization on the separate consideration of two classification pillars, the five “primary morphologies”, AEUC I–V (AEUC II–IV with subcriteria) and the five “patterns of calcification”. In addition, an intermodal classification scheme presents five stages of lesion evolution: “initial stage”, “progressive stage”, “advanced stage”, “transitional stage” and “regressive stage”. CONCLUSION: The imaging modalities differ with respect to their visualization of lesion criteria. This underlines the need for unimodal classification systems. Staging of an AE lesion can be done more accurately by evaluating different modalities. KEY POINTS: The AEUC provides a stage-oriented CT classification for hepatic AE. Aspects of different modalities allow a more multi-layered view of lesion evolution. More accurate staging can be achieved by combining different modalities. CITATION FORMAT: Graeter T, Schmidberger J. Stage-Oriented CT Classification and Intermodal Evolution Model in Hepatic Alveolar Echinococcosis. Fortschr Röntgenstr 2022; 194: 532 – 544.