Duplex ultrasound of the extremities looks at the arms or legs.
Renal duplex ultrasound examines the kidneys and their blood vessels.
You may need to wear a medical gown. You will lie down on a table, and the ultrasound technician will spread a gel over the area being tested. The gel helps the sound waves get into your tissues.
A wand, called a transducer, is moved over the area being tested. This wand sends out the sound waves.A computer measures how the sound waves reflect back, and changes the sound waves into pictures. The Doppler creates a "swishing" sound, which is the sound of your blood moving through the arteries and veins.
You need to stay still during the exam. You may be asked to lie in different body positions, or to take a deep breath and hold it.
Sometimes during a duplex ultrasound of the legs, the health care provider may calculate an ankle-brachial (ABI) index. You will need to wear blood pressure cuffs on your arms and legs for this test.
The ABI number is obtained by dividing the blood pressure in the ankle by the blood pressure in the arm. A value of 0.9 or greater is normal.
How to prepare for the test
Usually, there is no preparation for a duplex ultrasound.
If you are having an ultrasound of your stomach area, you may be asked not to eat or drink after midnight. Tell the person doing the ultrasound exam if you are taking any medicines, such as blood thinners, that might affect the results of the test.
How the test will feel
You may feel some pressure as the wand is moved over the body, but there is usually no discomfort.
Why the test is performed
Duplex ultrasound is a less invasive option to arteriography and venography. A duplex ultrasound can show how blood flows to many parts of the body. It can also tell the width of a blood vessel and reveal any blockages.
A duplex ultrasound can help diagnose the following conditions:
A renal duplex ultrasound can also be used after transplant surgery to see how well a new kidney is working.
A normal result is normal blood flow through the veins and arteries. There is normal blood pressure and no sign of a narrowing or blockage of a blood vessel.
What abnormal results mean
An abnormal result depends on the specific area being examined. An abnormal result may be due to a blood clot or plaque buildup in a blood vessel.
What the risks are
There are no risks.
Cigarette smoking may change the results of an ultrasound of the arms and legs, because nicotine can cause the arteries to shrink (constrict).
Cosgrove DO, Meire HB, Lim A. Ultrasound: general principles. In: Adam A, Dixon AK, Grainger RC, Allison D. Grainger and Allison’s Diagnostic Radiology: A Textbook of Medical Imaging. 5th ed. Orlando, Fl: Churchill Livingstone; 2008:chap 3.
David C. Dugdale, III, MD, Professor of Medicine, Division of General Medicine, Department of Medicine, University of Washington School of Medicine. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M. Health Solutions, Ebix, Inc.