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Duplex/doppler ultrasound test
Duplex/doppler ultrasound test

Blood flow studies
Definition:
These tests measure blood flow and blood pressure. A duplex study is a test which uses Doppler ultrasound to assess and/or monitor blood flow through arteries or veins. Plethysmography measures changes in blood volume in a blood vessel.

Alternative Names:
Duplex/Doppler ultrasound

How the test is performed:

For the Duplex/Doppler ultrasound:
Clothing from the area being monitored is removed, and a probe with a conductive gel (like vasoline) on the tip is placed on various points along the vessel being tested. This enables the technician to evaluate blood flow through the vessels. The information is relayed to the ultrasound monitor to be viewed and recorded.

For a plethysmography:
Blood pressure is first monitored in both arms.

The clothing from the extremity being tested is removed and the patient lies on his or her back. A blood pressure cuff is applied to the extremity being tested and inflated until the pulsatile flow is no longer heard. Then the pressure is released from the cuff until the flow returns. The blood pressure when flow returns is recorded and the information is transmitted to a computer which records and interprets the information.

The blood pressure cuff may be moved to other positions on the same or other extremities during the test. After the readings are taken, the patient may be re-tested while in another position such as sitting or standing.

How to prepare for the test:
Clothing over the extremity being tested will be removed just before the test. Medications being used that can alter blood flow will be recorded before the test. In general, there is no other special preparation necessary for these tests.

Infants and children:
The physical and psychological preparation you can provide for this or any test or procedure depends on your child's age, interests, previous experiences, and level of trust. For specific information regarding how you can prepare your child, see the following topics as they correspond to your child's age:
How the test will feel:
For the plethysmography, the blood pressure cuff will constrict the arm or leg, but there is no pain. The gel used for the duplex ultrasound may feel cold when it is placed on your skin.
Why the test is performed:
These tests are noninvasive (external) tests used to determine if there is significant disease in either arteries or veins, if adequate blood is reaching an extremity, to evaluate trauma to a blood vessel, or to monitor patients with arterial reconstruction or graphs. These tests can also detect blood clots.
Normal Values:
As part of a duplex ultrasound, the doctor may calculate an ABI or ankle-brachial index. This number is obtained by dividing the Doppler or systolic pressure of the ankle by the pressure in the arm. A value of 0.9 or greater is normal. Your doctor will also evaluate the flow of blood in the vessels with the ultrasound.
What abnormal results mean:

An ABI of less than 0.5 is associated with peripheral vascular (arterial) disease.

Other abnormal blood flow patterns can be seen with:

These tests, or tests like them, may also be performed for additional conditions:
What the risks are:
There are no special risks associated with these tests.
Special considerations:
Most Doppler ultrasounds use a duplex/Doppler probe to enable the technician to both view the vessels (regular ultrasound) as well as assess the blood flow through them (Doppler imaging).
Review Date: 12/2/2001
Reviewed By: John A. Daller, MD, PhD., Department of Surgery, University of Texas Medical Branch, Galveston, TX. Review provided by VeriMed Healthcare Network.
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