Hemodialysis access recirculation occurs when dialyzed blood returning through the venous needle reenters the extracorporeal circuit through the arterial needle rather than returning to the systemic circulation. It is important to meausre hemodialysis access recirculation for two reasons: The reentry of dialyzed blood into the extracorporeal circuite reduces solute
   concentration gradients across the dialysis membrane by mixing already dialyzed with undialyzed blood.

As a result, the efficiency of dialysis is reduced. High degrees of recirculation can lead to a significant discrepancy between the amount of hemodialysis prescribed (prescribed Kt/V urea) and the amount of hemodialysis delivdred (delivered Kt/V urea).

        High degrees of access recirculation indicate the presence of access stenoses, the most common cause of access thrombosis. Prospective identification and treamtnet of access stenoses improves long-term access patency rate.