A Computational Fluid Dynamics Analysis of Haemodynamics in Renal Arteries Following Endovascular Aneurysm Repair: The Impact of Stent-Induced Partial Coverage and Arterial Orientation

Endovascular Aortic Repair (EVAR) is a minimally invasive procedure for treating Abdominal Aortic Aneurysms (AAAs).A significant long-term complication is stent-graft migration, leading to partial coverage of the renal artery orifices, which is associated with renal dysfunction.This study numerically investigates the combined impact of renal artery orientation and the degree of partial coverage on renal haemodynamics.Idealized 3D models of the aorta with its major visceral branches were created using ANSYS Space Claim.Computational Fluid Dynamics (CFD) analyses were performed using ANSYS Fluent to simulate pulsatile blood flow.Fifteen models were evaluated, combining five levels of partial renal coverage (0%, 10%, 30%, 50%, 70%) with three renal artery take-off angles (60° downward, 90° horizontal, 120° upward).Haemodynamic parameters analysed included Time-Averaged Wall Shear Stress (TAWSS), Oscillatory Shear Index (OSI), Relative Residence Time (RRT), and volumetric flow rate.Results indicate that renal arteries with a horizontal (90°) orientation exhibited the most unfavourable WSS indicators (low TAWSS, high OSI and RRT) across all coverage levels.Downwardoriented (60°) arteries demonstrated favourable haemodynamics with mild coverage (≤30%), but performance deteriorated severely with coverage >50%.Upward oriented (120°) arteries maintained superior blood perfusion and more stable flow patterns even under severe coverage (70%), although localized regions of high RRT were observed.Renal artery orientation significantly influences haemodynamic outcomes post-EVAR.Downward orientations are optimal for mild coverage, while upward orientations provide a haemodynamic advantage under conditions of significant stent migration.Horizontal orientations are consistently the least favourable.These findings suggest that patient-specific anatomical assessment, particularly renal orientation, could be crucial for long-term EVAR planning and monitoring to preserve renal function.