A renal artery ultrasound shows the arteries that carry blood to the kidneys, according to the Heart Health Foundation. This ultrasound allows a doctor to see any narrowing of the arteries or blockages of blood flow to the kidneys that lead to high blood pressure and kidney failure.
The use of ultrasound waves creates a picture of the arteries, explains the Heart Health Foundation. By measuring the speed of blood flow through the arteries, the doctor determines the amount of narrowing in the arteries. In many cases, a doctor performs this test in the morning due to the difficulty of imaging these arteries.