Abstract:Background and Aims Type Ⅱ endoleak (T2EL) is the most common complication after endovascular abdominal aortic aneurysm repair (EVAR). While many cases remain benign, a subset may progress with aneurysm sac enlargement and require reintervention. Identifying risk factors for progressive T2EL and establishing a reliable risk stratification model may improve perioperative decision-making and postoperative surveillance. This study aimed to investigate the risk factors and threshold values for progressive T2EL after EVAR and to develop a nomogram-based prediction model.Methods Clinical data of patients who developed T2EL after EVAR for abdominal aortic aneurysm between March 2013 and December 2024 were retrospectively reviewed. Patients were classified into a progressive group (n=21) or a stable group (n=62) based on whether intervention criteria (An increase in the maximum aneurysm diameter of ≥10 mm compared with baseline) were met during follow-up. Clinical characteristics, anatomical parameters, and operative variables were compared. Multivariate Logistic regression was performed to identify independent risk factors for progressive T2EL. Receiver operating characteristic (ROC) curves were used to determine optimal cutoff values. A nomogram prediction model was constructed and internally validated using discrimination, calibration, and decision curve analyses.Results The progressive group had a significantly larger maximum aneurysm diameter, greater inferior mesenteric artery (IMA) ostial diameter, and a higher number of patent lumbar arteries (LA) compared with the stable group (all P<0.05). Multivariate analysis identified these three variables as independent risk factors for progressive T2EL after EVAR (all P<0.05). ROC analysis demonstrated increased risk of progressive T2EL in patients with a maximum aneurysm diameter ≥54.30 mm, IMA ostial diameter ≥2.82 mm, and ≥6 patent LA. The nomogram achieved a C-index of 0.858, which remained robust after internal validation (corrected C-index: 0.837), showing good discrimination, calibration, and clinical utility.Conclusion Maximum aneurysm diameter, IMA ostial diameter, and the number of patent LA are key predictors of progressive T2EL after EVAR. The proposed nomogram provides effective individualized risk assessment, although external validation is required before widespread clinical application.