What Is Carotid Ultrasound?

Carotid (ka-ROT-id) ultrasound is a painless and harmless test that uses high-frequency sound waves to create pictures of the insides of the two large arteries in your neck.

These arteries, called carotid arteries, supply your brain with oxygen-rich blood. You have one carotid artery on each side of your neck.

Carotid ultrasound shows whether a substance called plaque (plak) has narrowed your carotid arteries. Plaque is made up of fat, cholesterol, calcium, and other substances found in the blood. Plaque builds up on the insides of your arteries as you age. This condition is called carotid artery disease.

Carotid Arteries

You have two common carotid arteries—one on each side of your neck—that divide into internal and external carotid arteries. Figure A shows the location of the right carotid artery in the head and neck. Figure B is a cross-section of a normal carotid artery that has normal blood flow. Figure C shows a carotid artery that has plaque buildup and reduced blood flow.

Too much plaque in a carotid artery can cause a stroke. The plaque can slow down or block the flow of blood through the artery, allowing a blood clot to form. A piece of the blood clot can break off and get stuck in the artery, blocking blood flow to the brain. This is what causes a stroke.

A standard carotid ultrasound shows the structure of your carotid arteries. Your carotid ultrasound test may include a Doppler ultrasound. Doppler ultrasound is a special test that shows the movement of blood through your blood vessels.

Your doctor often will need results from both types of ultrasound to fully assess whether there's a problem with blood flow through your carotid arteries.

Other Names for Carotid Ultrasound

• Doppler ultrasound
• Carotid duplex ultrasound

Who Needs Carotid Ultrasound?

Carotid ultrasound checks for plaque buildup in the carotid arteries. Plaque can narrow or block your carotid arteries, preventing oxygen-rich blood from reaching your brain.

Your doctor may recommend a carotid ultrasound if you:

• Had a stroke or mini-stroke recently. During a mini-stroke, you may have some or all of the symptoms of a stroke. However, the symptoms usually go away on their own within 24 hours.
• Have an abnormal sound in your carotid artery called a carotid bruit (broo-E). Your doctor can hear a carotid bruit with the help of a stethoscope put on your neck over the carotid artery. A bruit may suggest a partial blockage in your carotid artery that could lead to a stroke.

Your doctor also may recommend a carotid ultrasound if he or she suspects you may have:

• Blood clots that can slow blood flow in your carotid artery
• A split between the layers of your carotid artery wall that weakens the wall or reduces blood flow to your brain

A carotid ultrasound also may be done to see whether carotid artery surgery, also called carotid endarterectomy (END-ar-ter-EK-to-me), has restored normal blood flow through your carotid artery.

If you had a procedure called carotid stenting, you may have carotid ultrasound afterward to check the position of the stent put in your carotid artery. (The stent, a small mesh tube, helps prevent the artery from becoming narrowed or blocked again.)

Sometimes carotid ultrasound is used as a preventive screening test in people who have medical conditions that increase their risk of stroke, including high blood pressure and diabetes.

People who have these conditions may benefit from having their carotid arteries checked regularly, even if they show no signs of plaque buildup.

What To Expect Before Carotid Ultrasound

Carotid ultrasound is a painless test, and typically there is little to do in advance. Your doctor will tell you how to prepare for your carotid ultrasound.

What To Expect During Carotid Ultrasound

Carotid ultrasound usually is done in a doctor's office or hospital. The test is painless and often doesn't take more than 30 minutes.

The ultrasound machine includes a computer, a video screen, and a transducer. A transducer is a hand-held device that sends and receives ultrasound waves into and from the body.

You will lie on your back on an exam table for the test. Your technician or doctor will put a gel on your neck where your carotid arteries are located. This gel helps the ultrasound waves reach the arteries better.

Your technician or doctor will put the transducer against different spots on your neck and move it back and forth. The transducer gives off ultrasound waves and detects their echoes after they bounce off the artery walls and blood cells. Ultrasound waves can't be heard by the human ear.

A computer uses the echoes to create and record pictures of the insides of the arteries (usually in black and white) and your blood flowing through them (usually in color; this is the Doppler ultrasound). A video screen displays these live images for your doctor to review.

Carotid Ultrasound

Figure A shows how the ultrasound probe (transducer) is placed over the carotid artery. Figure B is a color ultrasound image showing blood flow (the red color in the image) in the carotid artery. Figure C is a waveform image showing the sound of flowing blood in the carotid artery.

What To Expect After Carotid Ultrasound

You usually don't have to take any special steps after a carotid ultrasound. You should be able to return to normal activities right away.

Often, your doctor will be able to tell you the results of the carotid ultrasound when it occurs or soon afterward.

What Does a Carotid Ultrasound Show?

A carotid ultrasound can show whether plaque buildup has narrowed one or both of your carotid arteries and reduced blood flow to your brain.

If plaque has narrowed your carotid arteries, you may be at risk of having a stroke. That risk depends on how much of your artery is blocked and how much blood flow is restricted.

To reduce your risk for stroke, your doctor may recommend medical or surgical treatments to reduce or remove the plaque buildup in your carotid arteries.

What Are the Risks of Carotid Ultrasound?

There are no risks linked to having a carotid ultrasound, because the test uses harmless sound waves. These are the same type of sound waves that doctors use to record pictures of fetuses in pregnant women.

Key Points

• Carotid ultrasound is a test that uses high-frequency sound waves to create pictures of the insides of the two large arteries in your neck. These arteries, called carotid arteries, supply your brain with oxygen-rich blood.
• A carotid ultrasound can show whether a fatty substance called plaque has narrowed one or both of your carotid arteries and reduced blood flow to your brain.
• If plaque is narrowing your carotid arteries, you may be at risk for having a stroke, depending on how much of your artery is blocked and how much blood flow is restricted.
• A standard carotid ultrasound shows the structure of your carotid arteries. A Doppler ultrasound is a special test that shows the movement of blood through your blood vessels.
• Your doctor often will need the results from both types of ultrasound to fully assess whether there's a problem with blood flow through your carotid arteries.
• Your doctor may recommend a carotid ultrasound if you had a stroke or mini-stroke recently or are at high risk of having a stroke. During a mini-stroke, you may have some or all of the symptoms of stroke. However, the symptoms usually go away on their own within 24 hours.
• A carotid ultrasound also may be used to see whether carotid artery surgery (also called carotid endarterecomy) has been successful, whether a stent has been placed correctly, or as a preventive screening test.
• Carotid ultrasound is a painless test done in a doctor's office or hospital. It often doesn't take more than 30 minutes and usually requires no preparation or followup.
• Often, your doctor will be able to tell you the results of the carotid ultrasound when it occurs or soon after.
• There are no risks linked to having a carotid ultrasound because the test uses harmless sound waves.

Links to Other Information About Carotid Ultrasound

NHLBI Resources

• Carotid Artery Disease (Diseases and Conditions Index)
• Carotid Endarterecomy (Diseases and Conditions Index)
• Stents (Diseases and Conditions Index)

Non-NHLBI Resources

• Carotid Duplex (MedlinePlus)
• Carotid Ultrasound (MedlinePlus)
• Stroke (National Institute of Neurological Disorders and Stroke)

Clinical Trials

• Current Research (ClinicalTrials.gov)