Purpose:
The purpose of this study was to determine the frequency of diaphragmatic invasion and to identify topographic, clinical, and morphological factors associated with it using contrast-enhanced computed tomography (CT).

Material and methods:
In this retrospective study, 201 patients with confirmed hepatic alveolar echinococcosis (AE) examined at national referral centres between 2018 and 2025 were included. All patients underwent multiphase contrast-enhanced multidetector CT of the liver. Demographic data, lesion number and localisation, Alveolar Echinococcosis Ulm Classification type, maximum lesion diameter, vascular invasion, and extrahepatic extension were recorded. Diaphragmatic invasion was defined by the presence of at least two predefined CT criteria. Associations were assessed using Cramer’s V, and predictors of diaphragmatic invasion were analysed using multivariable logistic regression.

Results:
Extrahepatic spread was identified in 108 patients (53.7%). The association between diaphragmatic invasion and involved liver segments did not reach statistical significance (Cramer’s V = 0.619; p = 0.090). This result should be interpreted cautiously. Diaphragmatic involvement was more frequently observed in patients with lesions affecting the superior liver segments S2, S7, and S8. No significant positive associations were found between diaphragmatic invasion and vascular involvement (Cramer’s V ≤ 0.484; all p > 0.65). In multivariable ana­lysis, portal vein trunk invasion was inversely associated with diaphragmatic involvement (OR = 0.234; 95% CI: 0.062-0.883; p = 0.032).

Conclusions:
Diaphragmatic invasion is a relatively frequent feature of hepatic AE. Associations with liver segment involvement and vascular invasion require cautious interpretation. Recognition of characteristic CT findings remains important for pre-operative assessment and surgical planning.