Hemodialysis access recirculation is an important cause of inadequate dialysis delivery to individual patients. It is important to diagnose recirculation in order to optimize dialysis delivery. In addition, screening for recirculation may be used as a surveillance technique for the early detection of fistula stenosis, the correction of which may prevent thrombosis.
This topic reviews hemodialysis access recirculation. Other causes of decreased dialysis delivery are discussed elsewhere. (See "Prescribing and assessing adequate hemodialysis".)
Other methods of surveillance of fistulas and grafts to prevent thrombosis are discussed elsewhere. (See "Monitoring and surveillance of hemodialysis arteriovenous fistulas to prevent thrombosis" and "Monitoring and surveillance of hemodialysis arteriovenous grafts to prevent thrombosis".)
DEFINITION AND MECHANISM
Hemodialysis access recirculation occurs when dialyzed blood returning through the venous needle re-enters the extracorporeal circuit through the arterial needle, rather than returning to the systemic circulation (figure 1).
The re-entry of dialyzed blood into the extracorporeal circuit reduces solute concentration gradients across the dialysis membrane by mixing already dialyzed blood with undialyzed blood. Such mixing reduces the efficiency of dialysis. Significant recirculation can lead to a discrepancy between the amount of hemodialysis prescribed (prescribed Kt/V urea) and the amount of hemodialysis delivered (delivered Kt/V urea). (See "Prescribed versus delivered dialysis: Importance of dialysis time" and "Prescribing and assessing adequate hemodialysis", section on 'Causes of low delivered dialysis'.)