Blood flow surveillance of hemodialysis grafts: insights from two case reports.

It is widely recommended that all hemodialysis grafts undergo blood flow (Qa) surveillance, and that stenosis be corrected when accompanied by a low Qa or decrease in Qa (deltaQa). This recommendation has, however, become increasingly controversial. Studies have shown that although there is an association between Qa and thrombosis, the accuracy of Qa in predicting thrombosis within individual patients is poor. We describe two cases that demonstrate common causes of poor predictive accuracy. These cases also show that application of Qa surveillance algorithms is often complex and ambiguous. Most studies reporting that surveillance with intervention reduces thrombosis or prolongs graft life have used historical or sequential control groups, or have been retrospective. Accurate assessment of the benefit of graft surveillance must await studies that are fully prospective and randomized with concurrent control groups. Until such studies have demonstrated sufficient benefit, we do not recommend periodic Qa surveillance with intervention of all hemodialysis grafts.