Colour Doppler is an ultrasound test that shows blood vessels and the direction and speed of blood flow, with no pain, radiation or contrast. It detects clots, venous reflux and varicose veins, and narrowing or blockage of arteries. It is usually the first test a vascular surgeon requests before any treatment decision.
If you see a vascular surgeon, the first test you will likely be asked for is a Doppler. What is it, and why does it matter so much?
What is colour Doppler?
An ultrasound test that combines an image of the vessel with measurement of blood movement inside it. Blood appears in colours showing flow direction, and the machine measures speed, revealing narrowing, blockage or reflux.
Types of Doppler
- Venous Doppler: to diagnose clots and assess varicose veins, venous insufficiency and the site of reflux. Read about deep vein thrombosis and varicose veins.
- Peripheral arterial Doppler: to locate and grade leg artery narrowing.
- Carotid Doppler: to assess neck artery narrowing. See carotid artery disease.
- Dialysis access Doppler: to plan an access and assess its function.
- Aortic ultrasound: to detect and monitor aortic aneurysm.
How to prepare
- Leg and neck Doppler usually need no fasting.
- Abdominal aortic ultrasound may need a few hours of fasting to reduce gas.
- Wear clothes that make the leg or neck easy to expose.
- Bring previous scans or reports for comparison.
How is it done?
Gel is applied to the skin and the probe is moved along the vessels. For venous Doppler you may be asked to stand, hold your breath, or the examiner may squeeze the leg to measure reflux. It usually takes 15 minutes to an hour depending on the area.
Key words in the report
- Reflux: weak vein valves, with its location and duration.
- DVT / thrombosis: a clot, with its location.
- Stenosis: narrowing, given as a percentage or grade.
- Occlusion: complete blockage of an arterial segment.
Don't judge your condition from the report alone. It is read together with symptoms and examination, and the treatment decision is made by the doctor with the full picture.
Is Doppler safe?
Completely. No radiation, no contrast, no pain, and it can be repeated safely, which is why it is also used for follow-up after treatment.
Frequently asked questions
Is a Doppler test painful?
No. It is an ultrasound with no radiation or contrast; at most there is mild discomfort from probe pressure.
Do I need to fast before a Doppler?
Leg and neck Doppler usually don't; abdominal aortic ultrasound may need a few hours of fasting.
How long does it take?
From 15 minutes to an hour depending on the area examined.
Content on this website is for awareness only and does not replace a specialist medical examination.