Ultrasound Doppler diagnostic criteria for peripheral arterial stenosis, mild stenosis with 0-19% diameter reduction and unchanged peak systolic flow velocity compared to normal proximal artery; moderate stenosis with 20%-49% diameter reduction and 30%-100% increase in peak systolic flow velocity; severe stenosis with 50-74% diameter reduction and 100-300% increase in peak systolic flow velocity; very severe stenosis with 75-99% diameter reduction and greater than 300% increase in peak systolic flow velocity and no flow signal in the completely occluded vessel.