Patient education: Duplex ultrasound (The Basics)

What is a duplex ultrasound? — A duplex ultrasound is a test that doctors use to check how blood is flowing through blood vessels. It is a type of ultrasound test, which uses sound waves to create pictures of the inside of the body.

Why might my doctor order a duplex ultrasound? — Your doctor might order a duplex ultrasound to check for:

●Atherosclerosis – In this condition, fatty clumps called "plaques" build up in the arteries and make them narrow or blocked (figure 1). Atherosclerosis can happen in different parts of the body. This includes the carotid arteries (figure 2), the arteries of the legs (figure 3) or arms, or the arteries going to the kidney or other organs in the belly like the liver and intestines.

●Aneurysm – In people with an abdominal aortic aneurysm, or "AAA," a part of the abdominal aorta balloons out or bulges. (The aorta is the main blood vessel that comes out of the heart. The abdominal aorta is the part of it that is in the belly.) Aneurysms can also happen in blood vessels in the legs or arms, or in the vessels of the organs in the belly.

●Decreases in blood flow that might be caused by:

•A clot that has traveled from the heart or other blood vessel

•An injury to an artery

•A problem where a blood vessel is compressed or trapped by something, like a muscle or bone

●A deep vein thrombosis (also called a "DVT") – This is when a blood clot forms in a deep vein in the leg (figure 4).

●Problems with how the leg veins are working – If the veins in the legs don't work well, blood can collect in the legs.

A duplex ultrasound can also be done to:

●See if veins in the leg can be used to re-route blood during a "bypass" procedure

●Make a plan for using a vein to give medicine or do dialysis

●Follow up after having a procedure involving the blood vessels

How do I prepare for a duplex ultrasound? — Your doctor will tell you if you need to do anything to prepare. If you are having the test to check blood flow in your abdominal (belly) area, you might be asked to avoid eating for some time before the test.

In many cases, you do not need to do anything special before the test.

What happens during a duplex ultrasound? — The doctor, nurse, or technician will put a small amount of gel on the part of your body being checked. Then they will press a thick wand, called a "transducer," against your skin. They will move the transducer around on your skin. Color images will appear on a computer screen so the doctor can see where and how fast blood is flowing.

This test does not usually hurt, but people can feel pressure when the transducer presses against their skin.

In some cases, the doctor might put an "IV" (needle) into a vein so they can inject something called "contrast." This can improve the ultrasound images.

What are the downsides of a duplex ultrasound? — A duplex ultrasound does not usually have any downsides.

The contrast that is sometimes used has no downside for most people. But in rare cases, it can cause a serious reaction. People with an allergy to contrast, or to something called polyethylene glycol (PEG), should not get this type of ultrasound.

More on this topic

Patient education: Deep vein thrombosis (blood clot in the legs) (The Basics)
Patient education: Atherosclerosis (The Basics)
Patient education: Peripheral artery disease and claudication (The Basics)
Patient education: Carotid artery disease (The Basics)
Patient education: Echocardiogram (The Basics)

Patient education: Deep vein thrombosis (DVT) (Beyond the Basics)
Patient education: Peripheral artery disease and claudication (Beyond the Basics)
Patient education: Lower extremity chronic venous disease (Beyond the Basics)