Stages of renal artery stenosis: a hypothesis based on ultrasound findings: A narrative review

Current ultrasound (US) scanners can directly detect renal artery stenosis (RAS) in which the degree is the same irrespective of heart beat. Frequently, however, blood pressure or renal function is not improved because the stage of RAS is too late. Therefore, RAS should be early detected and thus the radiologists are familiar with US features of early, intermediate, and late RAS. Atherosclerosis is the most common etiology to RAS and begins inflammation from the intima of renal artery. Accordingly, we can hypothesize that there are multi-stages going to the final RAS. At early stage, RAS can be detected on diastolic phase alone. However, at intermediate stage, it begins to be seen on systolic phase and is more severe on diagnostic phase than that at early stage. Finally, at late stage, RAS is seen at the same degree regardless of heart beats because the stenosis is fixed due to fibrosis. The purpose of this review is to introduce a hypothesis on the stages of RAS, to show the renal artery US features of each stage, and to compare US and angiography in terms of RAS detection.