*3.2.1 PSV ratio: PSV at the anastomosis / PSV 2 cm proximal/distal to AVF*

PSV ratio is useful to exclude stenosis. Blood flow is measured within the AVF in mid part. Measuring blood flow volume warrants specific technique where it must be measured in continuous nontapering segment of draining vein about 10 cm from anastomosis. It is measured in middle of the lumen with maximum gate and not more than 60 degree insonation angle. Time averaged mean velocity should be counted for 3 cardiac cycles and then internal diameter of the vessel is measured. According to these parameters, scanner calculates the volume flow in ml per minutes.
