Doppler ultrasound

An ultrasound uses reflected sound waves to produce a picture of organs and blood vessels. The sound waves create a picture on a video screen.

Doppler ultrasound is a special kind of ultrasound. It can detect movement of blood through arteries and veins.

Some ultrasound tests are called "duplex." Duplex means "two parts." A duplex ultrasound combines the Doppler ultrasound with the more common ultrasound. The combination can help the doctor see more clearly what's going on.

There are no risks linked to an ultrasound test, and it is safe during pregnancy. It won't harm the baby (fetus).

You might have a Doppler ultrasound to:

• Look for reduced blood flow in major neck arteries. Low blood flow in these arteries can cause a stroke.
• Find a blood clot in leg veins, which could be a deep vein thrombosis.
• Check blood flow in a fetus to check the health of the fetus.
• Find a blockage or a narrowing in the arteries that go to the kidneys.

The doctor or ultrasound technologist will have you lie on your back, side, or stomach, depending on which part of your body is being examined.

• A gel will be applied to your skin. This helps the passage of sound waves.
• A hand-held device called a transducer will be moved along your skin.
• You'll need to stay still during the test.

Depending on what the test is for, you may be asked not to eat or drink after midnight before the test. Or you may be asked to drink water right before the test so that your bladder is full.

The scans from the test will be read within a short time.

Normal:

• The test does not show significant narrowing or other problems in any of the arteries.
• There is no sign of a clot in any of the veins examined. The size and position of veins are normal.
• Normal blood flow is found in the blood vessels that supply oxygen and nutrients to a fetus.

Abnormal:

• For continuous wave Doppler or duplex Doppler, differences in blood flow between the right and left sides of the body may be heard. At the exact spot where an artery is blocked or narrowed, the sound may be high-pitched or turbulent. Blockage (such as from a blood clot), an aneurysm, or narrowing of a blood vessel may be found. The speed of blood flow may be compared to standard values to find out how blocked or narrow the blood vessel is.
• A duplex Doppler ultrasound graph may show blood flow that isn't normal. This is a sign of a blocked or narrowed blood vessel.
• A color Doppler image may show a blocked or narrowed blood vessel or an aneurysm.
• In the veins, a blood clot may be present if blood flow does not change in response to breathing or does not increase after either a compression maneuver or Valsalva maneuver. Incomplete blockage of a vein by a blood clot may be seen on color Doppler or during a compression maneuver.
• Abnormal veins, such as varicose veins, are seen.
• There is an abnormal increase or decrease in blood flow through the vessels that supply oxygen and nutrients to a fetus.