Background:Acceptance has grown for single-needle dialysis when a vascular access is not suited for the insertion of two needles. Its impact on flow patterns was unknown. Methods:We produced transparent life-size models of arteriovenous(AV)fistulas and AV grafts that we placed into a pulsatile flow system to examine flow characteristics during simulated dialysis cycles. For this purpose we injected dye, and recorded and analyzed the resulting flow patterns using suitable software tools. Results:There is a definite flow reversal during the arterial phases in both AV fistulas and -less pronounced-in AV grafts leading to flow oscillations. Conclusion:Flow oscillations initiate subintimal hyperplasia possibly leading to stenoses in vivo. Reversal of the flow direction may also cause steal phenomena in the poorly perfused distal extremity. Single-needle dialysis should therefore be avoided if possible
