A Doppler ultrasound test uses reflected sound waves to evaluate blood as it flows through a blood vessel. It helps doctors evaluate blood flow through the major arteries and veins of the arms, legs, and neck
During duplex Doppler ultrasound, a handheld instrument (transducer) is passed lightly over the skin above a blood vessel. The transducer sends and receives sound waves that are amplified through a microphone. The sound waves bounce off solid objects, including blood cells. The movement of blood cells causes a change in pitch of the reflected sound waves (called the Doppler effect). If there is no blood flow, the pitch does not change. Information from the reflected sound waves can be processed by a computer to provide graphs or pictures that represent the flow of blood through the blood vessels. These graphs or pictures can be saved for future review or evaluation.
How It Is Done
You will need to remove any jewelry that might interfere with the Doppler ultrasound scan. You will need to take off all or most of your clothes, depending on which area is being examined (you may be allowed to keep on your underwear if it does not interfere with the test). You will be given a cloth or paper covering to use during the test.
- For abdominal scans, you will lie on your back.
- For chest scans, you will lie on your back with your neck slightly extended.
- For head and neck scans, your head may be turned to one side.
- For an arm or leg scan, your head is slightly raised and the exposed arm or leg is turned slightly outward.
Gel is applied to the skin to promote the passage of the sound waves. The transducer is placed in the gel and moved along the skin. You need to lie very still during the procedure. You may hear sounds that represent the flow of blood through the blood vessels.
Arteries in the arms and legs
This test is often performed on both arms or both legs. Even if the suspected blood flow problem is in only one limb, both may be tested for comparison. If your arms are being tested, they will be tested first while you are lying down and then again while you are sitting.
Depending on which blood vessels are being tested, a blood pressure cuff may be wrapped around one or both limbs so the blood pressure can be taken at several different places. When testing the legs, a blood pressure cuff may be wrapped first around the calf and then around the thigh. The test may be done at several locations on your leg. When testing the arms, the pressure cuff may be wrapped first around the forearm and then around the upper arm.
Veins in the arms and legs
For this test, you will be asked to lie down and breathe normally. You must lie very still. Any changes in blood flow that occur as a response to your breathing patterns are noted.
The test may be repeated while the examiner presses on the veins close to the surface of your skin to help detect a clot in the vein (called a compression maneuver). The examiner may do this with your legs or arms in different positions to ensure that the blood supply is not blocked in these positions. The examiner may also squeeze your calf or forearm to help blood move more quickly through the veins (called an augmentation maneuver). This is done to evaluate blood flow toward your heart.
Arteries in the neck
You will be asked to lie down with a pillow underneath your head for support. The test is performed on both sides of your neck, and then the results are compared to standard values to determine the amount of blockage or narrowing of the arteries.
How It Feels
There is normally no discomfort involved with having a Doppler ultrasound test. The gel may feel cold when it is applied to your skin unless it is first warmed to body temperature. If your blood pressure is taken during the test, you will feel pressure when the blood pressure cuffs are inflated.
There are no known risks associated with a Doppler ultrasound test.