Management of suspected hemodialysis graft dysfunction: usefulness of diagnostic US. 
To evaluate the role and usefulness of diagnostic ultrasonography (US) in the assessment of hemodialysis access grafts with an intermediate probability of graft malfunction.  One hundred forty-seven complete US examinations were performed in 91 patients.  Average volume of flow, peak systolic velocity, and diameter of residual lumen were recorded.  Patients were referred by the nephrology department when clinical findings were suggestive, but not obviously, of graft malfunction.  Study results were deemed normal if flow volume exceeded 1,300 mL/min without significant visualized stenosis of 50% of the diameter or greater or if flow approached 1,300 mL/min without peak systolic velocity greater than 400 cm/sec.  Of the 147 examinations, 49 (33%) had normal results, seven (5%) showed thrombosis at examination, and 91 (62%) had evidence of at least one significant visualized stenosis or diffuse notable degree of thrombus.  Three patients with normal results required fistulography within 90 days, one for thrombosis.  In the 91 studies with abnormal results, 69 patients underwent fistulography; results in 63 showed agreement, and three showed false-positive results.  More central venous stenoses were found at fistulography than at US.  US is a useful and reliable first step in managing clinically suspected hemodialysis graft stenosis.  One-third of the studies showed no significant stenosis and did not require angiographic evaluation.  US should be the initial study in patients suspected of having hemodialysis access dysfunction without exceptional evidence of stenosis.