Are varicose veins blood clots? Varicose veins vs thrombosis

Varicose veins are not blood clots. They are widened veins under the skin in which weak valves let liquid blood pool and flow back down the leg. Thrombosis is a clot of blood that partly or completely blocks a vein. Most people with varicose veins have no clots at all: a clot appears as a complication, most often as superficial thrombophlebitis, and the only reliable way to tell one from the other is a venous ultrasound.

A familiar situation: in the evening you notice bulging bluish knots on your shin, and a relative says, “Those are clots, they can break off.” Suddenly walking feels risky, you rub on whatever cream someone recommended, and the visit to a doctor keeps getting postponed. Let us look at how these conditions differ and when you should not wait.

Are varicose veins blood clots?

No. A bulging varicose vein is filled with liquid blood that is still moving, just more slowly and partly in the wrong direction. That is why a varicose knot feels soft, is easy to compress with a finger, and visibly flattens when you lie down with your leg raised. As a rule there is no clot inside it: on ultrasound, most varicose veins are fully open.

The confusion is understandable, because varicose veins can be the ground on which a clot forms. But varicose disease is a chronic condition that develops over years, while thrombosis is an acute event that develops over hours or days. The myth that “varicose veins always mean clots” does harm in two ways. Some people stop walking, even though the work of the calf muscles helps the veins. Others put off treatment because “there are clots in there already, it is dangerous to touch them.” A clot is a complication, not a built-in part of varicose veins.

Varicose veins vs thrombosis: what is the difference

• Varicose veins are widened veins under the skin (superficial veins) caused by valves that no longer close properly.
• Superficial thrombophlebitis, or superficial vein thrombosis, is a clot in a vein under the skin with inflammation of the vein wall, most often in a varicose vein.
• Deep vein thrombosis (DVT) is a clot in a vein that runs between the muscles and cannot be seen from outside, so its signs are indirect.

The table helps you get your bearings, but it does not make a diagnosis: deep vein thrombosis sometimes causes almost no symptoms, and swelling of one leg can have other causes too.

Can varicose veins turn into thrombosis?

In a widened vein, blood flows slowly and swirls, and the vein wall itself is altered: these are two of the three classic causes of a clot. The third is blood that clots more easily than usual: dehydration in hot weather, pregnancy and the first weeks after childbirth, hormonal medicines, surgery, cancer, and an inherited tendency to clotting. Long periods without moving make the stagnation worse.

• The clot stays in a small varicose knot: local pain, redness, a firm lump. If the clot is short and far from the points where the superficial veins drain into the deep ones, the risk is usually low. But its length and its distance from the deep veins are measured by the doctor on ultrasound, and this decides whether medication is needed. More on this in the article “Thrombophlebitis: is an inflamed vein an emergency?”.
• The clot grows upwards: along the great saphenous vein towards the groin, or along the small saphenous vein towards the back of the knee, where the superficial veins join the deep ones. This situation is treated as equivalent to deep vein thrombosis.
• Thrombophlebitis and deep vein thrombosis can occur at the same time: from outside you see only a reddened vein under the skin, while the deep clot is found on ultrasound. That is why the deep veins are always checked when someone has thrombophlebitis.

The danger is not the varicose knot itself but a clot in the deep veins, or a superficial clot that has reached the junction with a deep vein: a fragment of it can travel to the arteries of the lungs. The mechanism is explained calmly in the article “Can a blood clot break off?”.

It also works the other way round: after a deep vein thrombosis, the superficial veins can become overloaded and widen. This is secondary vein enlargement in post-thrombotic syndrome, and it is treated differently from ordinary varicose veins. That is why, before any procedure on the superficial veins, I check that the deep veins are open.

Can you have varicose veins in the deep veins?

People often search for “deep varicose veins”, but there is no such diagnosis in clinical guidelines: by definition, varicose veins are a disease of the superficial veins. The deep veins are surrounded by muscle and a tough layer of fascia and, as a rule, do not turn into twisted knots. What can happen to them is something else:

• Deep venous valve incompetence (deep reflux). It can be primary, when the valves are weak in themselves, and it often occurs together with varicose veins.
• Post-thrombotic syndrome, the after-effect of a previous thrombosis: the valves are damaged, the vein is partly narrowed, and the leg swells chronically.
• Acute deep vein thrombosis, the clot described above.

Deep vein incompetence cannot be seen from outside. It shows up as heaviness and swelling of the lower leg by evening and, over a long time, as darkening and hardening of the skin above the ankle. Superficial varicose veins and a past thrombosis cause the same complaints, so symptoms alone cannot tell them apart.

The only way to distinguish them is a duplex ultrasound. The doctor presses on the vein with the probe: a healthy vein collapses completely, while a vein with a clot does not. Colour mode shows which way the blood flows when the calf is squeezed or when you strain. Backward flow lasting longer than 0.5 seconds in the superficial veins, or longer than 1 second in the femoral and popliteal veins, is considered reflux.

A common mistake is to hear “deep varicose veins” and treat it with nothing but a cream. A cream can ease the sensations a little, but it does not restore valves and does not dissolve a clot. Ask what exactly the ultrasound found: reflux, signs of a past thrombosis, or a fresh clot. The treatment depends on the answer.

Blood clot in the leg or just varicose veins: how to check at home

This check does not replace an ultrasound, but it helps you judge how urgent things are. Compare both legs in good light.

1. 1Touch the bulging vein lightly with your fingertips, without pressing. Soft and easy to compress is how a varicose vein behaves. Firm like a cord and painful is a reason to suspect a clot.
2. 2Lie down for 10–15 minutes with your legs up on a pillow. Varicose knots visibly flatten; a spot that stays hard and raised is suspicious.
3. 3Look at the skin over the vein. A strip of redness along the vein, warmth to the touch and pain when touched are signs of thrombophlebitis.
4. 4Follow where the red strip runs. If it climbs along the inner side of the shin and thigh towards the groin, or along the back of the shin towards the back of the knee, this is urgent.
5. 5Measure the circumference of both calves with a tape at the same level, 10 cm below the bony bump just under the kneecap. If one calf has recently become noticeably thicker, especially with calf pain, get an ultrasound the same day. A difference of more than 3 cm is used in clinical scores for the probability of thrombosis, but a smaller difference, or equal measurements with calf pain, does not rule thrombosis out.

What not to do: do not massage the lump, do not apply heat, do not bandage it tightly, and do not start “blood-thinning” tablets on a friend's advice. These medicines are prescribed by a doctor after an ultrasound: without a diagnosis they may be useless or cause dangerous bleeding.

At the ultrasound, ask the doctor three questions:

• Is there a clot in the superficial or deep veins, and where is its upper end?
• Are the deep veins open, and are there signs of a past thrombosis?
• Where is the reflux: in which vein trunk and at what level?

The plan depends on the answers. During a duplex venous ultrasound I examine both the superficial and the deep veins, not only the spot that is bothering you.

When to see a doctor urgently

The signs below need medical help the same day, and if you have any trouble breathing, call an ambulance immediately on 103.

• Sudden swelling of one leg, either the lower leg or the whole leg, especially with pain in the calf or thigh. Do not wait until morning to see whether it goes down.
• Pain, a bursting feeling or tightness in the calf that gets worse when you walk.
• A red, hot, firm cord under the skin, especially one climbing the inner side of the leg towards the groin or the back of the shin towards the back of the knee.
• Thrombophlebitis in a vein that does not look varicose, or repeated episodes: a reason for an in-person examination, not just a cream.
• Bleeding from a varicose vein: lie down, raise the leg, press firmly on the bleeding spot and get medical help.
• The leg suddenly becomes very painful, swollen and bluish, or pale and cold: call an ambulance.
• Shortness of breath, chest pain that gets worse when you breathe in, coughing up blood, a racing heartbeat or fainting: call an ambulance, as these can be signs of a pulmonary embolism.

Do not wait for it to “pass on its own.” Why deep vein thrombosis is sometimes barely noticeable, and what other symptoms it can cause, is covered in the article “Deep vein thrombosis: symptoms you should not wait out”.

What next: if there is no clot and if there is one

If there is no clot but there are varicose veins with reflux, treatment is planned rather than urgent: compression stockings, sclerotherapy, endovenous laser ablation (EVLA) or miniphlebectomy, depending on the examination results. Removing the diseased veins removes the stagnation in them and lowers the risk of thrombophlebitis in those veins, although no treatment can rule out clots completely.

If there is a clot, it is treated first. The scope of treatment depends on where the clot is: in a varicose knot, in the trunk of a superficial vein close to the deep veins, or in the deep veins themselves. The doctor decides on medication, how long to take it and whether to use compression based on the ultrasound, usually with a follow-up scan; planned treatment of the varicose veins is postponed until the acute process settles. How I manage these patients is described on the page about treatment of venous thrombosis.

You can book an ultrasound by phone at +998 99 883-93-21 (Monday to Saturday, 8:00–20:00); if you have warning signs, do not wait for a routine appointment.

The bottom line: soft, bulging veins that flatten when you lie down are not clots, and they can be examined calmly and on a planned basis. A firm, red, painful strip, swelling of one leg or pain in the calf is a reason to have an ultrasound the same day.

Not sure? Call and I'll tell you how urgent your situation is: +998 99 883-93-21

This article is for informational purposes only and does not replace a consultation with a qualified physician. If you are experiencing symptoms, please see a specialist.