Detection of access strictures and outlet stenoses in vascular accesses. Which test is best?

The location of stenoses within an access may influence the diagnostic value of access monitoring tests. Whereas decreasing access flow (QACC) should occur with both venous outlet stenoses and strictures within the body of the access, normalized intra-access venous pressure (vPIA/MAP) depends on location of the venous needle relative to the lesion. The authors determined the value of vPIA/MAP and direct measurement of percent access recirculation (AR) and QACC in detecting venous outlet stenoses and strictures. Abnormal access studies were evaluated by Doppler ultrasound and fistulography. Well functioning grafts and arteriovenous fistulas (AVFs) have no AR; QACC averages 1,101 +/- 26 and 1,073 +/- 35 mL/min, and vPIA/MAP ratios are 0.34 and 0.16, respectively. Venous outlet stenoses (n = 36) or strictures (n = 32) were detected before thrombosis or intervention in 172 vascular accesses at risk. QACC in accesses with stricture was significantly lower than in those with venous outlet stenosis (361 +/- 11 vs 526 +/- 43 ml/min), as was less than prescribed blood flow (423 +/- 7 ml/min). AR was not detected in any access with stricture and in only 4 of 36 accesses with outlet stenosis. vPIA/MAP was elevated with venous outlet stenosis but not with strictures. The findings of QACC being less than blood pump flow without AR by dilution methods differentiated strictures from venous outlet stenoses.