Defining a significant stenosis in an autologous radio-cephalic arteriovenous fistula for hemodialysis.

The current definition of a significant stenosis in an autologous arteriovenous fistula (aAVF), the percentage narrowing compared with the adjacent "normal" vessel, is inaccurate. We believe a significant stenosis in the aAVF is an absolute minimal luminal diameter determined by the requirements of the hemodialysis pump. To determine what absolute diameter constitutes a hemodynamically significant stenosis in a radio-cephalic autologous arteriovenous fistula (RC aAVF), the minimal luminal diameter of dysfunctional RC aAVF was compared to that of functional RC aAVF using grayscale and color ultrasound. There were 93 fistulas in study group and 77 in control group. The mean minimum luminal diameter in study group was significantly lower than in control group (2.19 vs. 4.71 mm, p 0.001). With a cutoff value of 2.7 mm, there was 90% sensitivity and 80% specificity in distinguishing functional fistula from dysfunctional fistula. The area under the receiver-operator curve was 90% (CI 84-94%), indicating that a 2.7 mm diameter is accurate in discriminating functional from dysfunctional fistulas. An absolute minimal luminal diameter of 2.7 mm, as determined with grayscale and color ultrasound, is a useful cutoff for defining significant stenosis in a RC aAVF.