Non-linear resistance associated to complex geometry at high flow rates in vascular access for hemodialysis

Successful maturation and long-term function of a vascular access for hemodialysis relies on the creation and maintenance a low-resistance route between the arterial and the venous system. In this work, we demonstrate how vascular segments characterized by complex geometry can be associated with non-linear resistance behavior at the sustained flow rates required for hemodialysis treatment. Using an image-based computational hemodynamics approach, we determine the relationship between flow rate and pressure drop in two kink geometries obtained from CE-MRA of a native arterio-venous fistula and a synthetic loop graft, respectively. Experimental validation of the predicted pressure drops across the loop graft kink is shows excellent agreement with the computational findings. The increase in pressure drop obtained at the high flow rates required for hemodialysis may lead to the inability for the vascular access to mature or maintain a sufficient flow rate for renal replacement therapy. For this reason, a patient-specific analysis of the relationships between geometry and resistance in realistic vascular access configurations may help at ameliorating the outcomes of vascular access creation and function.