Diagnosis · Reflux
Venous Reflux Testing Explained
Quick answer: A venous reflux test checks whether the one-way valves in your leg veins are leaking, letting blood fall back toward your feet. It is done with duplex ultrasound while you stand: the doctor squeezes your calf, releases it, and measures whether blood flows backward and for how long. Lasting backward flow confirms reflux, the root cause of most varicose veins.
Key facts at a glance
- Venous reflux: blood flowing backward (down the leg) through a vein because its valves no longer close properly.
- Also called: venous insufficiency or valve incompetence.
- How it is tested: standing duplex ultrasound with calf squeeze or Valsalva (bearing down) maneuvers.
- What is measured: the direction of flow and how long backward flow lasts after the squeeze is released.
- Common reflux sites: the saphenofemoral junction (groin), saphenopopliteal junction (behind the knee), saphenous veins and perforators.
- Why it matters: reflux mapping decides which veins need treatment, and which don't.
What is venous reflux?
Your leg veins carry blood uphill to the heart. To stop it sliding back down, they contain small one-way valves, like doors that only swing one way. When you walk, your calf muscles squeeze the veins and push blood upward; the valves then close to hold it there.
In venous reflux , the valve leaflets no longer meet. Each time the calf relaxes, or simply when you stand, blood falls back down through the leaking valve. Pressure builds in the lower leg, veins stretch, and over time the surface branches bulge into varicose veins . Reflux is also behind heavy legs , swelling , night cramps and, eventually, skin damage.
How is a venous reflux test done?
The test is part of a duplex ultrasound exam . At LEDAS it runs like this:
- You stand. Reflux depends on gravity, so testing while standing is far more reliable than lying down. LEDAS uses its own examination table designed for standing scans.
- The vein is located. The probe finds each key vein: the deep veins, the great and small saphenous veins, their junctions with the deep system, and any perforators.
- A provocation is applied. The doctor squeezes your calf firmly for a moment, or asks you to take a breath and bear down (Valsalva maneuver).
- Flow is measured on release. In a healthy vein, blood moves up during the squeeze and stops almost immediately afterward. In a leaking vein, the color on screen flips and the Doppler trace shows blood flowing back down.
- Duration is recorded. The length of backward flow is measured. Brief reverse flow is normal while a valve closes; prolonged reverse flow indicates reflux. Commonly used guidance treats reverse flow longer than about half a second in superficial veins as abnormal, with slightly longer thresholds for some deep veins.
- The map is drawn. The test is repeated along the leg to find where reflux starts and how far down it runs.
The full LEDAS exam, including reflux testing, takes about 15–20 minutes, and you can watch the color changes on the Philips EPIQ Elite monitor as Dr. Kim Byoung Joon explains them.
What do the results mean?
No significant reflux
Your valves are working. If you have symptoms, they likely come from something else, and you will be advised where to look next.
Reflux in small surface veins only
Spider or reticular veins without main-vein reflux. These can often be managed with sclerotherapy if they bother you.
Reflux in a saphenous vein
The great or small saphenous vein is leaking, usually starting at its junction with a deep vein. This is the most common pattern behind varicose veins, and is typically treated with EVLT , with sclerotherapy for branches.
Perforator or hidden-branch reflux
Leaking veins between muscles or connecting to the deep system. LEDAS treats these with duplex-guided sclerotherapy , which it regards as key to preventing recurrence.
Deep vein reflux or obstruction
Valve damage or narrowing in the deep veins, sometimes after a past clot. This changes the plan and may limit which surface veins can safely be closed.
Why does careful reflux mapping matter?
Dr. Kim Byoung Joon identifies incomplete diagnosis as one of the leading causes of recurrent varicose veins . If a leaking perforator or accessory vein is missed, it keeps feeding pressure into the leg after treatment. Detailed reflux testing finds every source so the treatment plan covers them all, and also avoids treating veins that are actually healthy.
Reflux test findings and what usually follows
| Where reflux is found | What it means | Usual approach at LEDAS |
|---|---|---|
| None | Valves working normally | Look for other causes; healthy habits |
| Spider / reticular veins only | Small surface vessels | Sclerotherapy (SCT) if desired |
| Great or small saphenous vein | Main source of varicose veins | EVLT plus sclerotherapy for branches |
| Perforator or hidden branches | Feeders that often cause recurrence | Duplex-guided sclerotherapy (DGS) |
| Deep veins | Deep valve damage or past clot | Individual plan; compression; caution with closure |
Venous reflux testing – frequently asked questions
Is the calf squeeze during a reflux test painful?
It feels like a firm, brief squeeze and is not painful for most people. If your leg is tender or swollen, tell the doctor and the pressure can be adjusted. The squeeze lasts only a second or two each time.
Can venous reflux be present without varicose veins?
Yes. Reflux often begins in veins under the skin years before any surface vein bulges. During that time it may cause only heaviness, swelling, cramps or itching. A reflux test can detect it early, when treatment is usually simpler.
Does venous reflux go away on its own?
No. Once valves fail, they do not repair themselves. Compression, walking and leg elevation ease symptoms and slow progression, but the leak remains. Closing the refluxing vein lets blood reroute through healthy veins.
How often should reflux be re-tested?
After treatment, LEDAS recommends a follow-up ultrasound every one to two years, or whenever an overseas patient visits Korea. If new symptoms appear in between, an earlier check is sensible. See follow-up ultrasound and long-term care.
About this page
Clinical information:
LEDAS Varicose Vein Clinic, led by
Dr. Kim Byoung Joon , thoracic and cardiovascular surgeon, founding member of the Korean Society for Phlebology.
Medical reviewer:
Dr. Kim Byoung Joon ·
Review status:
Pending ·
Last updated:
October 2026
This page is general information and not a diagnosis. Treatment is decided only after an in-person examination. Read our
editorial policy .
Related: Duplex ultrasound exam · Chronic venous insufficiency · How your treatment plan is built · Vein health glossary · Self-check checklist
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