Is there any clinical correlation between Doppler flow data and the degree of stenosis in arteriovenous (AV) grafts for dialysis access? If so, are Doppler flow data a reliable indicator of decline in urea reduction rates?—DOYLE WINGATE, PA-C, Oneonta, Ala.

The most frequent complication of AV grafts for dialysis access is stenosis, which occurs at some point in up to 50% of patients. Doppler studies measure velocity of blood flow, while elevated venous pressure is an indicator of stenosis. However, not all grafts with high venous pressure will have a low blood flow. Duplex ultrasonography combines Doppler studies with compression ultrasound and is more reliable in predicting stenosis than Doppler studies alone. The addition of compression allows for a two-dimensional view of the lumen. Degree of stenosis is best measured with duplex ultrasound dilution studies. While this practical, noninvasive indicator of access flow is effective in predicting stenosis, the degree of stenosis is not correlated with renal function.—Claire Babcock O’Connell, MPH, PA-C (144-2)