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 or greater: A ratio of 3.5 or greater is indicative of significant renal artery stenosis.

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.