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Color Doppler

Click to EnlargeA 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. It can show blocked or reduced blood flow through narrowing in the major arteries of the neck that could cause a stroke. It also can reveal blood clots in leg veins (deep vein thrombosis, or DVT) that could break loose and block blood flow to the lungs (pulmonary embolism). See pictures of a stroke and an embolus . During pregnancy, Doppler ultrasound may be used to look at blood flow in an unborn baby (fetus) to check the health of the fetus.

Color Doppler uses standard ultrasound methods to produce a picture of a blood vessel. Also, a computer converts the Doppler sounds into colors that are overlaid on the image of the blood vessel and that represent the speed and direction of blood flow through the vessel.


Why It Is Done

  • Detect blood clots and blocked or narrowed blood vessels in almost any part of the body, especially in the neck, arms, and legs. Blocked or narrowed arteries of the neck can cause dizziness, loss of vision, paralysis, weakness, numbness, or other symptoms of a stroke.
  • Evaluate blood flow after a stroke or other condition that might be caused by a problem with blood flow. Evaluation of a stroke can be done through a technique called transcranial Doppler (TCD) ultrasound.
  • Evaluate abnormal veins causing varicose veins or other problems.
  • Find out the amount of blood flow to a transplanted kidney or liver.
  • Monitor the flow of blood following blood vessel surgery.

How To Prepare
You may be asked to not use products that contain nicotine (cigarettes, chewing tobacco) for 30 minutes to 2 hours before the test. Nicotine causes blood vessels to constrict and may give false results.


How It Is Done
This test is done by a doctor who specializes in performing and interpreting imaging tests (radiologist) or by an ultrasound technologist (sonographer) who is supervised by a radiologist. It is done in an ultrasound room in a hospital or doctor's office.

You will need to remove any jewelry that might interfere with the Doppler ultrasound scan. You may 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 will be slightly raised and the exposed arm or leg will be turned slightly outward. Sometimes for a leg scan, you may be asked to lie on your stomach.
  • During pregnancy, you will lie on your back or on your left side with your belly exposed.

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.

The test usually takes 30 to 60 minutes.


How It Feels
There is normally no discomfort involved with having a Doppler ultrasound test. The gel may feel cold when it is put on 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 cuff is inflated.


Risks
There are no known risks associated with a Doppler ultrasound test. This test will not harm a fetus.


Normal Result
There are no findings of significant narrowing or other abnormality in any of the arteries examined.
There is no evidence of a clot in any of the veins examined. The size and position of veins are normal.

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