Varicose Veins

What is the difference between varicose veins and thrombosis?

Martin Deterre

July 14, 2026

· — min de lecture

Varicose veins and thrombosis are both leg vein disorders, but very different. One is a refluxing vein, the other a dangerous clot. Here is how to tell them apart.

Key points :

Varicose veins and thrombosis are different vein disorders.
A varicose vein is a stretched, refluxing vein with faulty valves.
A thrombosis is a blood clot that blocks the vein.
Thrombosis is an emergency: it can cause a pulmonary embolism.
Varicose veins are treated calmly, without surgery.

Both varicose veins and thrombosis are vein disorders that most often occur in the legs. Yet they are two very different conditions, with different features, symptoms and risks. Here is how to tell them apart.

What are varicose veins?

Veins have one-way valves that open and close to push blood back to the heart against gravity. With varicose veins, these valves no longer close fully, so some blood flows back down and pools in the leg, a phenomenon called venous reflux. The rising pressure stretches the vein walls, which bulge into the visible, twisted veins we call varicose veins. The visible part is often only a portion of the diseased segment: deeper hidden varicose veins may also be affected, and the disease can exist without any visible vein.

How do varicose veins show up?

Varicose veins are often felt as unsightly and bothersome. Early on there is usually no pain, but symptoms can worsen over time, with pain or irritated, sore skin. Left untreated, they can seriously affect quality of life and, in the worst case, lead to an open leg ulcer (ulcus cruris).

Good news: a varicose vein can be treated without surgery. Echotherapy closes it without an incision.

Thrombosis: a dangerous clot in the vein

A thrombosis is a blood clot, usually forming in the leg veins where blood moves more slowly against gravity. When the clot grows large enough to block the vessel, it becomes a thrombosis: signs include leg swelling, pain and a reddish-blue discoloration of the skin. It must be taken seriously, because if the clot breaks off and travels it can cause a pulmonary embolism in the lungs, a stroke in the brain or a heart attack. See a doctor immediately if you suspect one.

This is the key difference: a varicose vein is a stretched, refluxing vein, whereas a thrombosis is a clot blocking the vein.

Varicose veins vs thrombosis at a glance

Feature	Varicose veins	Thrombosis
What it is	Stretched, refluxing surface veins (faulty valves).	A blood clot blocking a vein.
Appearance	Twisted, bulging, visible veins.	Swelling, pain, reddish-blue skin.
Danger	Slow progression; possible ulcer if untreated.	Emergency: risk of pulmonary embolism, stroke, heart attack.
When to act	At the first symptoms, to avoid complications.	Immediately, see a doctor.

How are they treated?

Thrombosis is treated with compression, medication (blood thinners), surgery or a combination, depending on the case. Varicose veins have their own options: endothermal ablation (laser or radiofrequency via a catheter), foam sclerotherapy, vein glue or surgical stripping. The newest thermal method, echotherapy, treats non-invasively with therapeutic ultrasound, entirely from the outside.

Wondering whether echotherapy is available near you? A growing network of centers is already equipped with the SONOVEIN.

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