Angle-dependent aorto–renal hemodynamics: a CFD-based assessment using a composite disturbance index

Renal artery take-off geometry can alter renal and aortic hemodynamics. Transient CFD simulations were performed for a bilateral aorto–renal model in which the right renal artery angle was varied from \(30^∘ \) to \(150^∘ \) , while the left renal artery was fixed at \(60^∘ \) . Newtonian and Carreau–Yasuda rheology models were assessed using three-element RCR Windkessel outlet conditions. TAWSS, OSI, RRT, and a composite Renal Angle Hemodynamic Disturbance Index (RAHBI) were evaluated. The response was non-monotonic and region dependent. Globally, Newtonian TAWSS increased from 1.02 to \(2.66~Pa\) between \(30^∘ \) and \(60^∘ \) , while OSI decreased from 0.184 to 0.035 and RRT from 1.57 to \(0.41~ {Pa⁻¹}\) . In the varied right renal branch, Newtonian TAWSS increased from 8.50 to \(22.42~Pa\) between \(30^∘ \) and \(150^∘ \) . The highest RAHBI occurred at \(30^∘ \) , reaching 78.954 and 13.972 for the Newtonian and Carreau–Yasuda models, respectively; at \(150^∘ \) , the corresponding values were 0.205 and 6.000. The fixed left renal branch also changed, confirming bilateral coupling. Velocity-profile validation yielded \(R=0.999\) , and two-way fluid–structure interaction reduced global TAWSS by 4.52%. Alternative weighting, arithmetic, and RRT-free formulations consistently identified \(30^∘ \) as the highest-scoring varied-branch configuration; rank agreement with the baseline index was \(ρ _s=0.90\) –1.00. These computational findings indicate that renal angulation, rheology, and bilateral interaction should be interpreted jointly. RAHBI is a configuration-specific comparative measure, not a clinically validated risk metric.