A carotid ultrasound looks for narrowed or blocked carotid arteries, which can increase the risk of stroke. These arteries are on each side of the neck.

Blood vessels narrow when plaque builds up inside them. This leads to reduced blood flow. Plaques are made up of fat, cholesterol, calcium and other substances that circulate in the blood. Early diagnosis and treatment of a narrowed carotid artery can lower the risk of stroke.

Your healthcare professional orders a carotid ultrasound if you have a transient ischemic attack (TIA), also called a ministroke. You also may need this test if you have other types of strokes or a condition that increases the risk of a stroke.

You may need a carotid ultrasound if you have:

• High blood pressure.
• Diabetes.
• High cholesterol.
• Family history of stroke or heart disease.
• A recent transient ischemic attack (TIA) or stroke.
• A sound in the carotid arteries known as a bruit. This can be heard using a stethoscope.
• Coronary artery disease.
• Hardening of the arteries, known as arteriosclerosis.

Other uses of carotid ultrasound

Your healthcare professional also may order a carotid ultrasound to:

• Check blood flow in the carotid artery after surgery to remove plaques. The procedure to remove plaques is called carotid endarterectomy.
• Check the placement of a mesh tube called a stent that was inserted into an artery during surgery to improve blood flow. The test also can check how well the stent is working.
• Look for a collection of clotted blood, known as a hematoma, that may prevent blood flow.
• Look for other changes to the carotid artery that may affect blood flow.
• Predict coronary artery disease by measuring the thickness of the carotid artery. The carotid ultrasound also looks at the characteristics of a plaque.
• Monitor carotid artery blood flow during aortic heart valve surgery. This helps your healthcare professional understand your risk of a stroke.
• Create a 3D model of the carotid artery to improve the accuracy of a diagnosis.

There are no risks associated with having a carotid ultrasound. You might feel a pressure during the test, but the test is painless. A carotid ultrasound has no harmful effects.

To prepare for a carotid ultrasound:

• Plan to wear a comfortable shirt with an open collar.
• Don't wear a necklace or dangling earrings.

Follow any other instructions you receive from your healthcare professional or the radiology lab.

How it works

A technician called a sonographer conducts a carotid ultrasound with a small, handheld device called a transducer. The transducer emits sound waves and records the echo as the waves bounce off tissues, organs and blood cells.

A computer translates the echoed sound waves into images on a monitor. The ultrasound technician may use a Doppler ultrasound, which shows blood flowing through the arteries. In a Doppler ultrasound, the rate of blood flow is translated into a graph.

There have been many advances in carotid ultrasounds to improve the quality and resolution of the images.

A carotid ultrasound usually takes about 30 minutes.

During the procedure

You'll likely lie on your back during the ultrasound. The ultrasound technician may position your head to better access the side of your neck.

The ultrasound technician applies a warm gel to your skin above the site of each carotid artery. The gel helps transmit the ultrasound waves. The technician then gently presses the transducer against the side of your neck.

There is no discomfort during the procedure. If you have discomfort, tell the ultrasound technician.

A doctor who specializes in imaging tests, called a radiologist, reviews the results of the carotid ultrasound. The radiologist may go over the results with you right after the procedure.

The radiologist sends a report to the healthcare professional who ordered the carotid ultrasound. This may be a doctor trained in heart and blood vessel conditions, called a cardiologist. Or it might be a doctor trained in brain and nervous system conditions, called a neurologist.

The healthcare professional who ordered the test explains to you what the carotid ultrasound revealed and what that means for you.

If the test shows that you're at risk of a stroke, your healthcare professional may recommend the following, depending on how serious the blockage is:

• Eat a healthy diet, including fruits, vegetables, and whole-grain breads and cereals. Limit saturated fat in your diet.
• Exercise regularly.
• Keep a healthy weight.
• Eat a heart-healthy diet such as the Mediterranean diet.
• Don't smoke. Avoid secondhand smoke.
• Take medicines to lower blood cholesterol and blood pressure.
• Take medicines to prevent blood clots.
• Have a surgical procedure to remove carotid artery plaques. This procedure is called carotid endarterectomy.
• Have a surgical procedure to open and support your carotid arteries. This procedure is called carotid angioplasty and stenting.

If your healthcare professional ordered a carotid ultrasound as a follow-up to surgery, the test can show whether the treatment is working. It also can let your healthcare professional know if you need other treatment or follow-up exams.

Other tests

If your results are not clear, you may have other imaging tests, such as:

• A computerized tomography angiogram, known as CTA, scan. A CTA scan uses a series of X-rays to produce detailed images of the blood vessels in the body. A dye may be injected into a vein to make the carotid arteries easier to see.
• Magnetic resonance imaging, known as MRI. An MRI uses a magnetic field and radio waves to produce detailed images of soft tissues in the body. An MRI can find plaques and bleeding. A magnetic resonance angiography, known as MRA, scan also may be performed to get a better look at blood vessels.
• Contrast-enhanced ultrasound. A contrast agent inserted into your vein helps find early hardening of the arteries. It also can check for future blood vessel disease.
• 3D ultrasound. This test improves how well blood vessels can be seen during the test. It also helps evaluate a plaque. But 3D ultrasound may underestimate narrowing of the carotid artery.