Proximal renal artery stenosis greater than 60% is diagnosed when the systolic renal/aortic velocity ratio is:

In the assessment of proximal renal artery stenosis, a systolic renal/aortic velocity ratio greater than 3.5 is indicative of significant stenosis, specifically when the degree of narrowing exceeds 60%. This metric arises from Doppler ultrasonography, where the analysis of blood flow velocities provides insights into the severity of arterial narrowing.

The rationale behind using this ratio is based on hemodynamic principles. A higher velocity in the renal artery compared to the aorta suggests a significant increase in blood flow speed due to the constricted area, which correlates with the degree of stenosis. When this ratio exceeds 3.5, it typically signifies critical stenosis in the renal artery, warranting further diagnostic evaluation and potential intervention.

In contrast, ratios below 2.0 generally indicate no significant stenosis, while values between 2.0 and 3.5 may suggest mild to moderate stenosis but do not meet the threshold for indicating severe involvement. Consequently, understanding these velocity ratios is crucial for appropriate diagnosis and management of renal artery diseases.