How does a renal artery ultrasound work exactly?

See below. Renal artery ultrasound is using a special probe with the ultrasound machine to detect blood flow, and blockage if any in the artery. Ultrasound employ high frequency sound waves which bounce of structures within the abdomen in this case and are converted into a picture for analysis.It is my opinion that this is not a very sensitive test for native kidneys and I do not use it.
Doppler. Doppler ultrasound measures the velocity in the renal arteries and compares this with the velocity in the aorta. Accelerated velocity in the renal artery indicates a narrowing or stenosis. Renal artery stenosis can cause hypertension. Dilating the stenosis can potentially cure the hypertension.