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Duplex Ultrasonography

Basic Facts

  • Ultrasound is a painless, non-invasive, radiation-free diagnostic test that uses high-frequency sound waves to create images of body tissues.
  • Duplex ultrasound also allows physicians to measure the velocity of blood flow and to see the structure of the blood vessels through which the blood is flowing.
  • Physicians use duplex ultrasound to diagnose and examine diseases that affect the blood vessels, as well as to plan for and evaluate surgical and interventional therapies.
Duplex ultrasound can measure blood flow and detect arterial narrowing, as in this carotid artery.
Duplex ultrasound can measure blood flow and detect arterial narrowing, as in this carotid artery.
Ultrasound is a tool that a physician uses to gather information about a patient beyond his or her medical history and a physical examination. For example, ultrasound allows a physician to evaluate the veins and arteries in a person's body and to watch blood as it flows through blood vessels. Duplex ultrasonography is a form of ultrasound that produces images that differentiate between the body's soft tissues and its fluid-filled structures. Duplex ultrasound can also detect motion, such as the movement of blood cells.

Duplex ultrasound is used to detect the presence and severity of numerous conditions, including:
  • Thrombosis (blood clots);
  • Blockages from atherosclerosis (hardening of the arteries);
  • Thrombophlebitis (an inflammation of the blood vessels);
  • Trauma to an artery or vein;
  • Raynaud's phenomenon (a spasm of small blood vessels in the fingers); and
  • Increases in the thickness of the blood vessel lining.
Duplex ultrasound can also be used in conjunction with other tests, such as the measurement of blood pressure in the legs to test for reduced blood flow to the extremities (arms or legs).


There is usually no restriction of food or liquid before the duplex ultrasound is performed. The physician will provide any special instructions regarding medications, as appropriate.


There are no known risks associated with this test.


The patient will lie down with his or her head slightly elevated. The technician will request that the person lay quietly during the test to help ensure that the images are clear. The technician will then apply a special gel directly on the skin above the area to be examined. The technician presses a transducer (a hand-held device that emits sound waves) against the person's skin and may move the transducer back and forth to get clear images of the underlying blood vessels and structures.

The procedure typically lasts for 30 minutes, but the duration varies depending on the structure being examined.


Ultrasound carries no identified risks and can be repeated as often as necessary.


Patients can resume normal activities following a duplex ultrasound.

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