Measurement of the residual diameter of a stenotic lesion using B-mode US has also been proposed as a method for identifying a stenosis within an AVF or AVG [26]. The measurement of AVF or AVG blood flow by US is not considered as accurate when compared to other methods of measuring blood flow through the dialysis vascular access. Data on duplex Doppler US flow volume assessments suggests that an optimally functioning AVF demonstrates a flow rate of 700 to 1,300 mL/min [27]. Values of <500 mL/min [4] and <300 mL/min [27] serve as predictors of access dysfunction and pending thrombosis, respectively. In addition to such absolute measurements, it has been demonstrated that a vascular access with prior stability of flow volumes >1,000 mL/min followed by a reduction of >25% over a relatively short time interval of 1 to 4 months may predict access dysfunction [28]. Some issues with obtaining diagnostic images with US include limitations related to patient anatomy. Given that systematic assessment of an AVF by duplex US may be challenging, its use is encouraged when monitoring or surveillance has suggested abnormalities or when limitations to performance of routine dialysis arise. Such abnormalities or limitations may be reflected by reports of difficulty cannulating the access for hemodialysis, inadequate blood flows, high venous pressures, or prolonged bleeding after removal of dialysis access needles. While a few studies have shown the feasibility of US-guided angioplasty for the treatment of stenosis, the majority of endovascular treatment is still performed using fluoroscopically-guided fistulography in an angiography suite [29,30]. The use of physical examination findings and other indicators of a dysfunctional dialysis access can be used to identify patients with a probable hemodynamically significant stenosis. These patients can in turn be referred directly for diagnostic fistulography and the needed endovascular intervention [31].
Dialysis Fistula Malfunction. Measurement of the residual diameter of a stenotic lesion using B-mode US has also been proposed as a method for identifying a stenosis within an AVF or AVG [26]. The measurement of AVF or AVG blood flow by US is not considered as accurate when compared to other methods of measuring blood flow through the dialysis vascular access. Data on duplex Doppler US flow volume assessments suggests that an optimally functioning AVF demonstrates a flow rate of 700 to 1,300 mL/min [27]. Values of <500 mL/min [4] and <300 mL/min [27] serve as predictors of access dysfunction and pending thrombosis, respectively. In addition to such absolute measurements, it has been demonstrated that a vascular access with prior stability of flow volumes >1,000 mL/min followed by a reduction of >25% over a relatively short time interval of 1 to 4 months may predict access dysfunction [28]. Some issues with obtaining diagnostic images with US include limitations related to patient anatomy. Given that systematic assessment of an AVF by duplex US may be challenging, its use is encouraged when monitoring or surveillance has suggested abnormalities or when limitations to performance of routine dialysis arise. Such abnormalities or limitations may be reflected by reports of difficulty cannulating the access for hemodialysis, inadequate blood flows, high venous pressures, or prolonged bleeding after removal of dialysis access needles. While a few studies have shown the feasibility of US-guided angioplasty for the treatment of stenosis, the majority of endovascular treatment is still performed using fluoroscopically-guided fistulography in an angiography suite [29,30]. The use of physical examination findings and other indicators of a dysfunctional dialysis access can be used to identify patients with a probable hemodynamically significant stenosis. These patients can in turn be referred directly for diagnostic fistulography and the needed endovascular intervention [31].