In search of an optimal bedside screening program for arteriovenous fistula stenosis

Guidelines recommend systematically screening for stenosis using various methods, but no studies so far have compared all of the options. A prospective blinded study was performed to compare the performance of several bedside tests performed during dialysis in diagnosing angiographically proven >50% fistula stenosis.

In an unselected population of 119 hemodialysis patients with mature fistulas, physical examination (PE) was conducted; dynamic and derived static venous pressure (VAPR), blood pump flow/arterial pressure (Qb/AP) ratio, recirculation (R), and access blood flow (Qa) were measured; and angiography was performed.

Angiography identified 59 stenotic fistulas: 43 stenoses were located upstream from the venous needle (inflow stenosis), 12 were located downstream (outflow stenosis), and 4 were located at both sites. The optimal tests for identifying an inflow stenosis were Qa < 650 ml/min and the combination of a positive PE "or" Qa < 650 ml/min (accuracy 80% and 81%, respectively), the latter being preferable because it was more sensitive (85% versus 65%, respectively) for a comparable specificity (79% versus 89%, respectively). The best tests for identifying outflow stenosis were PE and VAPR, with no difference between the two (accuracy 91% and 85%, sensitivity 75% and 81%, specificity 93% and 86%, respectively), the former being preferable because it was more reproducible, easier to perform, and applicable to all fistulas.

This study showed that fistula stenosis can be detected and located during dialysis with a moderate-to-excellent accuracy using PE and Qa measurement as screening procedures.