What is the correct aortic renal artery ratio for a stenosis in ultrasound?

3.5. Nobody judges by just one number. Having said that, most labs consider abnormal (60-99% stenosis of renal artery) renal to aortic systolic velocity ration of greater then 3.5 this is not, however, validated after stenting, the velocities tend to be higher.
3.5. Typically, renal artery stenosis is suggested by ultrasound criteria when the rar (renal artery to aortic ratio) is >3.5. There are other parameters that are evaluated. Remember, too, that ultrasound is merely a screening study. Further testing is typically needed to confirm stenosis. See: http://www.Siumb.It/files/journal/2009/12/1_granata.Pdf.
3.5 or greater. A ratio of 3.5 or greater is indicative of significant renal artery stenosis.