Determinants of Hemodynamic Risk in Type II Endoleak: A CFD Study on Inferior Mesenteric and Lumbar Arteries

Background Type II endoleak (T2EL), the most common complication after endovascular aortic aneurysm repair (EVAR), remains a leading cause of reintervention due to persistent retrograde flow from patent inferior mesenteric artery (IMA) and lumbar arteries (LAs). The influence of specific anatomical features of these vessels on the hemodynamic environment remains poorly understood. Methods This study evaluated two key anatomical characteristics: branch vessel count and luminal diameter. Thirteen patient-specific post-EVAR models were constructed. Computational fluid dynamics (CFD) simulations were performed to quantify key hemodynamic parameters, including flow velocity, pressure, wall shear stress (WSS), oscillatory shear index (OSI), and relative residence time (RRT). Results A patent IMA has the greatest impact on intrasac pressure. Increased LA numbers predominantly alter flow field patterns and shear stress distribution, while larger vessel diameters significantly affect flow rate, WSS directionality, and intra-sac blood residence time. Enlarged IMA diameter combined with multiple patent LAs expanded retrograde flow regions and created high-shear-stress environments that inhibited thrombus formation, promoting T2EL persistence and sac expansion. A risk-stratified embolization strategy was proposed: high-risk patients (IMA ≥ 2.5 mm with ≥ 2 patent LAs) should undergo embolization of IMA and LAs ≥ 2 mm; intermediate-risk (IMA 2.0–2.5 mm or ≤ 1 LA) receive IMA embolization; low-risk patients (IMA < 2.0 mm with ≤ 1 LA) require regular follow-up. Conclusion This study provides the first quantitative analysis of the hemodynamic effects of IMA/LA patency, vessel number, and diameter, establishing a biomechanical framework for individualized T2EL risk stratification and management.