الفهرس 
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Abstract
Arterio-venous fistulas (AVF) are the preferred vascular access for patients with end-stage kidney disease. They are cheap and easy to construct, have excellent patency rates and require minimal maintenance by the patient and the health care staff.
They can develop various complications, which have different rates of incidence, morbidity and mortality. Most of them threaten the functionality of the fistula and some of them even pose an immediate vital risk.
Beside the type of vascular access, there are other factors that affect the survival of ESRD patients as inadequate dialysis and one of the causes of inadequate dialysis in HD patients is arterio-venous (A-V) fistula access recirculation (AR).
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.
The most common cause of access recirculation is the presence of high-grade venous stenosis, which obstruct venous outflow and other causes include improper needle placement.
The degree of access recirculation for urea can be calculated from the following formula:
Percent recirculation = ([P - A] ÷ [P - V]) x 100
where P, A, and V refer to the urea concentrations in the peripheral blood, predialyzer arterial line, and postdialyzer venous circuit, respectively.