Vascular Ultrasound – What Patients Should Expect Before, During, and After the Test

What Is a Vascular Ultrasound and Why Would Your Doctor Order One?

A vascular ultrasound is a painless, non invasive imaging test that uses high frequency sound waves to create detailed pictures of your arteries and veins. Unlike X rays or CT scans, a vascular ultrasound uses no ionizing radiation, making it extremely safe even for repeated use. The test evaluates both the structure of your blood vessels – such as the thickness of the vessel wall or the presence of plaque – and the function, specifically how fast and in what direction blood flows through them.

Your doctor may order a vascular ultrasound for many reasons. If you have experienced a transient ischemic attack or minor stroke, you will likely need an evaluation of carotid artery disease to see if plaque is narrowing the main arteries in your neck. If you have a pulsating feeling in your abdomen or a family history of aortic problems, your physician will want to screen for an abdominal aortic aneurysm. For patients who smoke or have diabetes, leg pain while walking may signal peripheral artery disease, and a vascular ultrasound can confirm that diagnosis. The test is also essential for diagnosing deep vein thrombosis blood clots in the legs and chronic venous insufficiency, a condition where vein valves fail and cause leg swelling, skin changes, and sometimes ulcers.

Many patients feel anxious before any medical test, but a vascular ultrasound is one of the most patient friendly procedures available. You remain fully awake, there are no needles or injections, and you can return to your normal activities immediately afterward. The entire experience is similar to the ultrasound scans that pregnant women receive, just focused on your blood vessels instead of a baby.

How Should You Prepare for a Vascular Ultrasound Based on the Type of Exam?

Preparation requirements vary depending on which blood vessels your doctor needs to examine. Failing to prepare correctly can lead to poor image quality, and the test may need to be rescheduled. The table below summarizes what you need to do for each common type of vascular ultrasound.

For an abdominal aortic aneurysm screening, fasting is mandatory. When you eat, your intestines fill with gas and food particles. Sound waves cannot penetrate gas, so the technologist will not be able to see your aorta clearly. If you have not fasted, the test will likely be rescheduled. You may drink small amounts of water, but avoid coffee, tea, juice, or carbonated beverages.

For leg artery or leg vein ultrasound, you can eat normally. However, you should avoid applying any lotion, cream, or oil to your legs on the day of the test. These products create a barrier that weakens the sound waves. You should also dress in loose, comfortable clothing that is easy to remove or roll up. A two piece outfit is ideal because you can keep your upper body covered while the technologist works on your legs.

Here is a complete checklist for preparing for any vascular ultrasound:

• Confirm with your doctor’s office whether you need to fast. If you are having an abdominal aortic study, do not eat for 6–8 hours before the test.
• Wear loose, two piece clothing. Bring shorts if you have them for a leg ultrasound.
• Do not smoke for at least two hours before the test. Nicotine temporarily constricts your blood vessels and can change your blood flow patterns, leading to inaccurate results.
• Take all your usual medications unless your doctor specifically tells you otherwise. Blood thinners like warfarin, apixaban, or clopidogrel do not interfere with ultrasound images.

What Happens During the Vascular Ultrasound Step by Step?

Walking into an unfamiliar exam room and seeing an ultrasound machine can be intimidating. Knowing exactly what will happen from the moment you arrive until the moment you leave takes away most of that anxiety.

When you check in for your appointment, you will be asked to change into a gown or remove clothing covering the area to be examined. For a leg ultrasound, you will remove your pants and socks but keep your underwear. For a carotid ultrasound, you will unbutton your shirt or wear a gown that opens in the front. You will lie down on an exam table. The room is usually dimly lit – this reduces glare on the ultrasound screen and helps the technologist see fine details.

The technologist will position you comfortably. For most leg artery and vein studies, you lie on your back with your head slightly elevated. A small pillow is placed under your knees to relax your leg muscles. For carotid artery imaging, you lie flat on your back with a small pillow under your shoulders, which extends your neck slightly. For an abdominal aortic ultrasound, you lie on your back, and the technologist may ask you to take deep breaths and hold them briefly to push your diaphragm down, moving the liver and intestines out of the way.

Once you are positioned, the technologist applies a warm, water based gel to your skin over the area of interest. The gel serves two purposes: it lubricates the skin so the probe glides easily, and it eliminates air between the probe and your skin. Air reflects sound waves, so without gel, you would see only a white blur on the screen. Most patients find the gel pleasantly warm, though some clinics use room temperature gel.

The technologist then places the ultrasound probe – a handheld device about the size of a computer mouse – against your skin. They will move the probe gently back and forth, pressing lightly. You may feel mild pressure, but it should never be painful. If an area is tender because of a recent injury or suspected blood clot, tell the technologist immediately. They can reduce pressure and adjust their technique.

As the probe sends out sound waves and listens for returning echoes, a computer converts those echoes into real time images. You will see black and white images of your blood vessels on the screen. When the technologist activates color Doppler, you will see red and blue colors superimposed on the images – red usually indicates blood flowing toward the probe, and blue indicates blood flowing away. You may also hear a swishing or whooshing sound. That sound is your own blood flow, amplified and translated into an audible signal.

During the exam, the technologist will ask you to perform small maneuvers to test how your blood vessels respond:

• For venous studies: squeeze your calf muscles or bear down as if having a bowel movement (Valsalva maneuver). These actions change pressure in your veins and help the technologist see whether your vein valves close properly.
• For carotid artery imaging: turn your head slightly to the left or right, and sometimes hold your breath for a few seconds. This moves the carotid artery into a better position.
• For leg artery exams: the technologist may place blood pressure cuffs at your ankle, calf, thigh, and arm. They will inflate each cuff briefly to measure pressures. This is part of an ankle brachial index and toe pressure measurement, which is almost always performed together with a leg artery ultrasound.

The entire test takes between 30 and 60 minutes. Carotid ultrasounds are often the shortest – around 30 minutes. A full leg artery and leg vein study may take closer to 60 minutes. You are not sedated, so you can drive yourself home afterward. There is no recovery time.

What Does a Vascular Ultrasound Show About Your Blood Vessels?

Once the images are complete, a vascular surgeon or radiologist interprets them. A normal vascular ultrasound shows smooth vessel walls, no plaque, and blood flow that moves in the expected direction at normal speeds. But when disease is present, the ultrasound reveals specific abnormalities.

For arteries, the most common finding is peripheral artery disease, where plaque narrows the lumen. The technologist measures blood flow velocity at multiple points along the artery. A normal artery has a triphasic waveform – three distinct phases of flow with each heartbeat. As the artery narrows, the velocity increases. A 50% stenosis doubles the velocity. A 75% stenosis quadruples it. When the velocity exceeds certain thresholds, the surgeon knows the blockage is significant enough to consider angioplasty, stenting, or bypass.

For the carotid arteries, the ultrasound looks for stenosis that could cause a stroke. A mild stenosis (less than 50%) is usually managed with medications and lifestyle changes. A moderate stenosis (50–69%) requires close follow up. A severe stenosis (70–99%) often leads to a recommendation for carotid endarterectomy or stenting to prevent a future stroke.

For the abdominal aorta, the ultrasound measures the diameter from wall to wall. A normal aorta is about 2 cm wide. An aneurysm is diagnosed when the diameter reaches 3 cm or more. Once the aneurysm grows to 5 cm in women or 5.5 cm in men, the risk of rupture becomes high enough that surgery is usually recommended. Smaller aneurysms are followed with annual or semi annual ultrasounds.

For veins, the ultrasound checks for two main problems. First, a deep vein thrombosis (DVT) appears as a clot within the vein. The technologist applies pressure with the probe – a normal vein compresses completely, but a vein with a clot does not. Second, chronic venous insufficiency is diagnosed when the vein valves fail. During a Valsalva maneuver or calf squeeze, the technologist watches for reflux – blood that flows backward instead of toward the heart. Reflux lasting longer than 0.5 seconds is considered abnormal.

How Should You Care for Yourself After the Test and When Will You Get Results?

After the technologist finishes acquiring images, they will wipe the gel off your skin. You can dress and leave immediately. There are no restrictions on driving, eating, or physical activity. You may resume all normal medications.

The images are sent electronically to a physician who specializes in vascular interpretation. In most clinics, a vascular surgeon or a radiologist reads the study within 24 to 48 hours. The technologist cannot give you results during the test because they are not trained to interpret the findings. Formal interpretation requires comparing your measurements to established normal values and clinical guidelines.

Once the report is complete, your doctor’s office will contact you. This may be by phone, secure patient portal message, or a follow up appointment. The report will include numerical data – for example, “right common carotid artery peak systolic velocity 125 cm/s, internal carotid artery peak systolic velocity 210 cm/s, ratio 1.7, consistent with 50–69% stenosis.” If the results are normal, you may simply be told that no significant disease was found.

If the results show significant abnormalities – such as an abdominal aortic aneurysm larger than 5 cm, a carotid artery stenosis greater than 70%, or severe peripheral artery disease with an ankle brachial index below 0.5 – you will be scheduled for a consultation with a vascular surgeon to discuss treatment options. These may include lifestyle modifications, medications, or procedures such as angioplasty, stenting, or open surgery.

Many patients without symptoms still benefit from routine screening. Preventative health vascular screenings can detect silent diseases like aneurysms or advanced PAD before they cause a rupture or limb loss. For patients with diabetes, high blood pressure, a smoking history, or a family history of vascular disease, a vascular screening is a simple, painless way to identify problems early.

Medical Disclaimer: This information is for educational purposes only and does not replace professional medical advice. Always consult your physician or a vascular surgeon for any health concerns or before starting any treatment.

Frequently Asked Questions About Vascular Ultrasound

Article Information

Author: Jacek J. Paszkowiak, MD, FACS

Medical Reviewer: Donald C. Carmichael, MD, FACS

Last reviewed: March 13, 2026