A duplex ultrasound combines traditional ultrasound with Doppler ultrasound.
- Traditional ultrasound uses sound waves that bounce off blood vessels to create pictures.
- Doppler ultrasound records sound waves reflecting off moving objects, such as blood, to measure their speed and other aspects of how they flow.
There are different types of duplex ultrasound exams. Some include:
Arterial and venous duplex ultrasound of the abdomen examines blood vessels and blood flow in the abdominal area.
- Carotid duplex ultrasound looks at the carotid artery in the neck.
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.