An ultrasound test uses sound waves to allow your doctor to see blockages or narrowing in your blood vessels and to determine the size of your kidneys. When performed in the heart, ultrasound is called echocardiography. Duplex ultrasound can generate images of the walls of a blood vessel as well as measure the rate at which blood is flowing through a vessel.
Duplex ultrasound allows your doctor to gather information not just about structures in your body but also about how blood moves through blood vessels by combining regular ultrasound with a Doppler ultrasound, which is capable of analyzing sound waves that are emitted and then bounced back from moving red blood cells. This information is interpreted by a computer to show the speed at which blood cells are moving through a blood vessel.