Venous Reflux Test: What to Expect from a Vein Ultrasound Study

What Is a Venous Reflux Test?

A venous reflux test, also called a venous reflux study or venous duplex ultrasound, is a non-invasive imaging exam that uses sound waves to evaluate how blood flows through the veins in your legs. The study is the standard diagnostic tool for chronic venous disease and is the most common workup ordered for patients with leg swelling, aching, heaviness, or visible varicose veins.

The test specifically looks at whether the one-way valves in your leg veins are working correctly. When those valves leak, blood flows backward (refluxes) and pools in the lower leg, causing the symptoms most patients recognize: swelling at the end of the day, aching after standing, restless legs at night, and skin changes around the ankle.

Why Your Doctor Ordered the Test

A venous reflux study is typically ordered when you have one or more of the following:

• Visible varicose veins or bulging leg veins
• Leg swelling that worsens through the day
• Aching, heaviness, or fatigue in the legs
• Skin discoloration or thickening near the ankle
• A non-healing wound on the lower leg
• Restless legs at night

The test confirms whether your symptoms come from venous insufficiency (leaky valves), arterial disease (blocked arteries), or a deep vein clot. Each condition is treated differently, so an accurate diagnosis is the foundation of any treatment plan.

How to Prepare

There is almost no preparation for a venous reflux study. Most patients can:

• Eat and drink normally before the exam
• Take all regular medications
• Wear loose clothing that can be rolled above the knee, or change into a gown at the clinic

Plan for the appointment to take 45 to 60 minutes per leg.

What the Test Feels Like

The test is performed by a registered vascular sonographer using a hand-held ultrasound probe and a small amount of warm gel. You will be asked to stand for most of the study, because gravity is what makes the leaky valves visible on ultrasound. (If standing is difficult, the test can be performed reclining on a tilt table.)

The sonographer presses the probe gently against the skin along the length of the leg and uses two techniques:

• Compression — squeezing the calf or thigh to push blood up the vein toward the heart
• Release — letting go and watching how the blood moves once the squeeze stops

In a healthy vein, the valves snap shut when the squeeze releases. In a leaking vein, blood flows backward through the open valve. The sonographer measures how long that backward flow lasts.

The test is painless. You may feel mild pressure from the probe. There is no radiation, no contrast dye, no needles, and no recovery time.

What Reflux Time Means

What reflux time means. Reflux duration is measured in seconds. Threshold values vary by vein type:

• Superficial veins (great saphenous, small saphenous): reflux of 0.5 seconds or longer is generally considered pathologic.
• Deep veins (femoral, popliteal): reflux of 1.0 second or longer is generally considered pathologic.
• Perforator veins: thresholds are even shorter (around 0.35 seconds) for clinical significance.

Your sonographer and physician interpret your specific results in clinical context — duration alone doesn’t determine treatment. Anatomy, symptoms, and other findings all factor in.

The report also tells your doctor which specific veins are leaking (great saphenous, small saphenous, accessory branches, perforators), how wide each vein is, and whether there is any deep vein thrombosis or scarring.

What Happens Next

If the study shows no reflux, your symptoms are likely coming from another source and your doctor will work through the next set of tests. If the study shows clinically significant reflux, you have several treatment options, all minimally invasive:

• Endovenous ablation (radiofrequency or laser closure of the leaking vein)
• VenaSeal medical adhesive closure
• Sclerotherapy for smaller branch veins
• Compression therapy as a first-line conservative option

These treatments are performed in our outpatient clinics, take less than an hour, and most patients return to normal activity the same day.

Schedule Your Vein Evaluation

If you have leg pain, swelling, or visible veins and have not had a venous reflux study, schedule a consultation with one of our vascular specialists. The test is non-invasive, covered by most insurance plans when medical necessity criteria are met (typically requires CEAP class 2+ symptoms, documented reflux, and a trial of conservative therapy like compression stockings), and the foundation of any vein treatment plan.

All treatments carry potential risks and benefits. Your physician will discuss what’s appropriate for your specific situation during consultation.