Quick answer
What Is Duplex Ultrasound?
Duplex ultrasound is a sound wave test that combines images of the blood vessel walls with a recording of blood flow. It is used to assess narrowing of the neck and leg arteries, blood clots in the veins, varicose veins, and widening of the abdominal aorta. It needs no radiation or needles and usually takes 30 minutes.
Sources01 / Understanding the procedure
About Duplex Ultrasound
What Is Duplex Ultrasound
Duplex ultrasound examines the blood vessels using sound waves. It is called duplex because it combines two imaging methods: black-and-white images that show the walls and interior of the vessels, and Doppler, which shows the direction and speed of blood flow in color and on graphs. This test is also known as Doppler ultrasound or vascular ultrasound. There is no radiation, no needle, and no contrast dye.
Blood Vessels That Can Be Examined
- Carotid arteries in the neck: the main vessels to the brain, to assess narrowing that can trigger a stroke.
- Leg veins: to look for blood clots and leaky vein valves in varicose veins.
- Leg and arm arteries: to find narrowing or blockages.
- Abdominal aorta: to measure widening (aneurysm).
- Kidney arteries: when narrowing that causes high blood pressure is suspected.
- Vessels after a procedure: for example stents, bypass grafts, or dialysis access.
How It Works in Brief
A small device called a probe sends out sound waves and picks up their echoes. Echoes from the vessel walls form an image, while echoes from moving blood cells show the direction and speed of flow.
What Is Assessed
- Narrowing: blood flow becomes much faster as it passes through the narrowed section.
- Blockage: no flow is seen in the blocked section of the vessel.
- Clot in a vein: the vein does not collapse when gently pressed with the probe.
- Leaky vein valves: blood flows backward after the calf is squeezed and released.
- Widening: the vessel diameter is measured and compared with the normal size.
Duplex Ultrasound and Other Tests
Duplex ultrasound is often the initial test for blood vessel disease. For the leg arteries, it is often combined with an ankle-brachial index (ABI) test. If a more complete picture is needed before a procedure, your doctor may follow up with CT angiography or catheter angiography.
02 / Understanding the procedure
When Is This Procedure Considered?
A doctor may consider this procedure in the situations below. The decision is always made after a thorough assessment.
- Suspected Blood Clot in a Leg VeinFor example, when one leg suddenly becomes swollen, painful, warm, or red.
- Varicose Veins and Chronic Vein ProblemsTo assess leaky vein valves and map the veins before varicose vein treatment.
- Leg Pain When WalkingTo find the location and severity of narrowing in the leg arteries, especially when the ABI result is low.
- Carotid Artery AssessmentAfter a stroke or minor stroke, or when the doctor hears an abnormal flow sound in the neck.
- Monitoring a Widened Abdominal AortaTo measure the size of an abdominal aortic aneurysm and monitor how it changes over time.
- Monitoring After Blood Vessel ProceduresFor example, after stent placement, bypass surgery, varicose vein ablation, or creation of dialysis access.
Situations to Consider First
- Open Wounds or Bandages in the Examination AreaThe probe cannot be placed over a wound, so that area is skipped or the test is adjusted.
- Severe Pain or SwellingThe test can still be done with gentler pressure. Tell the staff if it hurts.
- Abdominal Scan Without FastingGas in the intestines interferes with images of the aorta and kidney arteries, so the test may be rescheduled.
- Difficulty Lying Down or Standing for LongTell the staff early on so the test position can be adjusted.
- Sudden Shortness of Breath or Chest PainThese symptoms can signal a blood clot in the lungs. Do not wait for your scheduled test; go to the emergency room right away.
03 / Before the procedure
How Should You Prepare?
The majority of duplex ultrasound tests need no special preparation. Preparation depends on which vessels will be examined.
Neck, arms, and legs. No fasting is needed. You can eat, drink, and take your medicines as usual.
Abdominal aorta and kidney arteries. You are usually asked to fast for a few hours, often from the night before, so gas in the intestines does not interfere with the images. Plain water is usually still allowed. Follow the team's instructions.
Clothing. Wear loose clothing that is easy to remove from the area being examined. Remove any necklace if your neck will be examined.
Medicines. Keep taking your regular medicines, including blood thinners, unless your doctor gives other instructions. Bring a list of your medicines.
Previous results. Bring previous ultrasound or CT results, or records of previous blood vessel procedures such as stent placement or varicose vein ablation, for comparison.
Unsure about the preparation instructions? Ask our team before the procedure.
04 / During the procedure
How Is the Procedure Done?
Examining one area usually takes about 30 minutes. It takes longer if both legs or several areas are examined at once.
Test Position
You lie on the examination bed. To assess the leg vein valves, you may be asked to stand or sit with your legs hanging down, because valve leaks are easier to see in that position.
Applying the Gel
A clear gel is applied to your skin so the sound waves can travel well. The gel may feel cold.
Taking the Images
The doctor or technician moves the probe along the blood vessel while watching the screen. You may hear a pulsing or whooshing sound from the machine. This is the sound of the blood flow being recorded.
Additional Checks
For veins, the probe is pressed gently to see whether the vein collapses, and your calf may be squeezed to assess backward flow. For the leg arteries, the blood pressure at your ankles may be measured at the same time.
Finishing and Results
The gel is wiped off and you can resume your activities right away. Preliminary results may be explained after the test, while the full report is given later and discussed with your referring doctor.
05 / Benefits and risks
Benefits and Risks Should Be Discussed Together.
Every medical procedure has benefits and risks. Your doctor will explain both for your situation before the procedure.
Benefits You Can Expect
- No Radiation and No NeedlesSafe to repeat for monitoring and can be done during pregnancy.
- Results Visible Right AwayImages and blood flow are assessed in real time, so blood clots in the veins can be recognized quickly.
- Assesses the Severity of NarrowingFlow speed helps determine how severe a narrowing in the carotid or leg arteries is.
- Vein Map Before Varicose Vein TreatmentShows which veins and valves are leaking, as a basis for planning treatment.
- Long-Term MonitoringSuitable for regularly monitoring aneurysm size and the condition of stents or bypass grafts.
The benefits of a procedure are not a promise of a cure. Ask how the results will affect your care plan.
Risks You Should Know
- Discomfort from Probe PressureEspecially on a painful or swollen leg, or when the abdomen is pressed. Tell the staff if it hurts.
- Gel Feels ColdThis lasts only a moment and is harmless.
- Less Clear Images in Certain SituationsExcess body weight, intestinal gas, calcified vessels, or severe swelling can reduce image sharpness.
- Further Tests May Be NeededIf the results are not yet clear, or if more detail is needed before a procedure, your doctor may request CT angiography or catheter angiography.
- Skin Reaction to the GelVery rare. Tell the staff if you have had skin irritation before.
Risks can differ from person to person. A full explanation and consent are given after an individual assessment.
06 / After the procedure
What Is Recovery Like?
There is no recovery period. You can return to your activities, eat, and drink as usual right away.
Skin. Leftover gel is easily wiped off with a tissue or water and leaves no marks.
Discussing the results. Discuss the results with your doctor, including whether you need treatment, a procedure, or a repeat test for monitoring.
Medicines. If a blood clot is found, your doctor may start blood thinners right away. Take your medicine as prescribed and do not stop it on your own.
Warning signs. Go to the emergency room right away or contact the medical team if you have:
- Sudden shortness of breath or chest pain
- A leg that becomes more swollen, painful, or discolored
- A leg or arm that feels cold, pale, and numb
- A drooping face, arm weakness, or slurred speech
Know the Signs That Need Prompt Care.
Follow the team's guidance on warning signs. If severe or sudden symptoms appear after the procedure, go to the nearest emergency department right away or call Heart Attack Center 1500 258.
07 / Team and support
Doctors and Procedure Support
The doctors below are listed for this procedure. Listed by name, not by ranking.
dr. Emanoel Oepangat, Sp.JP(K)
Interventional Cardiology
Vascular Diagnostic and Therapeutic Center +1 center
Clinical focusCoronary Intervention · Peripheral Vascular Intervention
View Profile
dr. Indah A. Putri, Sp.N, Subsp, NIOO(K), MSc
Neurovascular, Interventional, Otology, Imaging, and Ophthalmology
Clinical focusStroke and Cerebrovascular Disease · Neurosonology
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dr. Suko Adiarto, Sp.JP(K), Ph.D.
Interventional Cardiology
Vascular Diagnostic and Therapeutic Center +1 center
Clinical focusCoronary Intervention · Peripheral Vascular Intervention
View ProfileDoppler Vascular Ultrasound
An ultrasound test of the blood vessels that shows the vessel wall and the blood flow at the same time. Doctors use it to look…
The availability of technology and test support is confirmed with the team. Technology is chosen according to clinical need.
08 / Common questions
Before You Plan the Procedure.
Frequently asked questions about duplex ultrasound. The team will give you specific instructions for your own test.
What is the difference between duplex ultrasound and Doppler ultrasound?
Both terms are often used for the same test. Doppler is a way of measuring blood flow with sound waves. Duplex ultrasound combines Doppler with black-and-white images of the vessel walls, so the doctor can see the shape of the vessel and its flow at the same time. In many hospitals, this test is also called vascular ultrasound.
Does duplex ultrasound hurt?
Usually not. You only feel the cold gel and light pressure from the probe. On a swollen or painful leg, the probe pressure used to check the veins may feel briefly uncomfortable. Tell the staff if it hurts, so the pressure can be adjusted without reducing the quality of the test.
Do I need to fast before duplex ultrasound?
It depends on the area being examined. For the neck, arms, and legs, no fasting is needed. For the abdominal aorta and kidney arteries, you are usually asked to fast for a few hours so gas in the intestines does not interfere with the images. Plain water is usually still allowed. Follow the instructions the team gives you when scheduling.
Is duplex ultrasound safe during pregnancy?
Yes. Duplex ultrasound uses sound waves, not radiation, so it is safe during pregnancy. In fact, this test is often used to look for blood clots in the leg veins during pregnancy, because the risk of clots increases at that time. Tell the team that you are pregnant so the test position can be adjusted.
Can duplex ultrasound replace angiography?
For many purposes, duplex ultrasound is enough to make a diagnosis and monitor the disease. However, before a procedure such as stent placement or surgery, the doctor sometimes needs a more complete picture from CT angiography or catheter angiography. Your doctor will explain which test is right for you.
How long does the test take?
Examining one area, such as the neck arteries or the veins of one leg, usually takes about 30 minutes. If both legs or several areas are examined, it can take an hour or longer. The team will give you an estimated time when scheduling, so set aside enough time.
Sources and Medical Review
Translated from the Indonesian edition medically reviewed by dr. Emanoel Oepangat, Sp.JP(K).
Sources as cited in the Indonesian edition.
- Mazzolai L, Teixido-Tura G, Lanzi S, et al. 2024 ESC Guidelines for the management of peripheral arterial and aortic diseases. Eur Heart J. 2024;45(36):3538-3700.
- Mazzolai L, Aboyans V, Ageno W, et al. Diagnosis and management of acute deep vein thrombosis: a joint consensus document from the European Society of Cardiology working groups of aorta and peripheral vascular diseases and pulmonary circulation and right ventricular function. Eur Heart J. 2018;39(47):4208-4218.
- De Maeseneer MG, Kakkos SK, Aherne T, et al. European Society for Vascular Surgery (ESVS) 2022 Clinical Practice Guidelines on the Management of Chronic Venous Disease of the Lower Limbs. Eur J Vasc Endovasc Surg. 2022;63(2):184-267.
- Naylor R, Rantner B, Ancetti S, et al. European Society for Vascular Surgery (ESVS) 2023 Clinical Practice Guidelines on the Management of Atherosclerotic Carotid and Vertebral Artery Disease. Eur J Vasc Endovasc Surg. 2023;65(1):7-111.