Why Varicose Veins Occur in Only One Leg: Causes and What to Do

Varicose veins in only one leg may be associated with anatomical features, uneven physical load, an old injury, or impaired venous outflow. Enlarged veins should be examined by a doctor and checked with vein duplex ultrasound: sometimes the cause is related to previous thrombosis, compression of a vein, or the effects of pregnancy.

By evening, twisted veins may become noticeable on one leg, along with heaviness, sock marks, or slight swelling. The other leg may look normal. The appearance of the legs cannot show how well the venous valves are working.

Why Varicose Veins Occur on Only One Side

The veins in the right and left legs may differ in where they join, the diameter of individual segments, and the connections between the superficial and deep systems. Therefore, venous insufficiency may sometimes first appear on only one side.

Other possible causes:

• Uneven load on the legs. The dominant leg is more often involved in climbing stairs, carrying heavy objects, standing work, or sports. This is not the only cause of varicose veins, but load asymmetry may be significant.
• An old injury or surgery. Tissue damage, prolonged immobilization, a fracture, or an intervention on the limb may alter venous outflow.
• Previous thrombosis. After thrombosis, the valves and walls of the veins may work less effectively. Over time, heaviness, swelling, changes in skin color, and enlarged superficial vessels may appear. This condition is called post-thrombotic syndrome.
• Compression of a vein from the outside. Surrounding tissues or anatomical structures may impair blood outflow predominantly on one side.
• May-Thurner syndrome. This is an anatomical variation in which outflow through the left iliac vein is impaired in some people. Therefore, symptoms occur more often in the left leg. This cause cannot be confirmed or ruled out based on the appearance of the veins.
• A history of pregnancy. During pregnancy, the load on the venous system increases, hormonal levels change, and pressure in the pelvic area rises. Symptoms may remain predominantly in one leg, especially in people predisposed to venous problems.

Sometimes varicose veins are visible externally, while the main problem lies deeper. The opposite can also occur: symptoms may be pronounced, but the superficial veins are barely noticeable. Therefore, the appearance of the legs does not reliably indicate the condition of the veins.

What Vein Duplex Ultrasound Checks

For unilateral symptoms, I start with vein duplex ultrasound. The examination shows more than just enlarged vessels. It is important to assess:

• the patency of the deep and superficial veins;
• the direction of blood flow;
• the function of the venous valves;
• the presence of pathological reverse blood flow;
• signs of previous thrombosis;
• the condition of connecting veins;
• possible impaired outflow above the groin.

The ultrasound examination is performed in different body positions and with functional tests. This is important: while lying down, a vein may appear normal, but when standing, it becomes possible to see where blood flow is impaired.

Unilateral varicose veins should not automatically be considered a cosmetic issue. Even without pain, an examination helps determine whether treatment, monitoring, or measures to reduce the load on the legs are needed.

After the examination and ultrasound, the doctor determines the treatment plan. This may include treatment for varicose veins, compression support in appropriate cases, or monitoring with a repeat assessment. I provide the treatment cost after the examination in a written estimate. It depends on the extent of the problem, not only on whether the veins are visible in one or both legs.

How to Distinguish Ordinary Asymmetry from a Reason to Get Checked

One noticeable vein alone does not provide an answer. It is important to consider the symptoms and how they change over time.

If varicose veins are accompanied only by spider veins, the treatment approach may differ from that used for bulging veins. For spider veins, I use CLaCS: a combination of a cryolaser and sclerotherapy. The laser acts through the skin, while the sclerosant is injected into the spider vein feeder vessel. Nothing is removed through punctures. The removal of individual varicose tributaries through small punctures is called miniphlebectomy.

When reflux in a main saphenous vein is confirmed, EVLA with a Biolitec laser may be possible. Sclerotherapy, including micro- and foam Echo-Foam sclerotherapy, is used for individual vessels. The method is selected after vein duplex ultrasound, not from a photograph of the leg.

Self-Check at Home: What You Can Do Today

A home check does not replace diagnosis, but it can help you collect information for the doctor.

• Examine both legs in the morning and evening under the same lighting. Note the location of enlarged veins, differences in skin color, and the degree of swelling.
• Compare whether your shoes fit equally on both feet at the end of the day. Separately note sock marks and any feeling of tightness on one side.
• Pay attention to heaviness, a feeling of pressure, itching, nighttime cramps, pain, and burning.
• Recall when the changes began. Relate them to pregnancy, an injury, surgery, a long flight, bed rest, or previously diagnosed thrombosis.
• Measure the circumference of your calves only to monitor changes over time: at the same location and at the same time of day. Do not use the result as a diagnosis.
• Do not massage a painful swelling or start taking medications 「to thin the blood」 on your own.

It is useful to bring a list of medications, discharge summaries after surgeries, and information about previous thromboses to your appointment. You may want to ask the doctor specific questions:

• Is there impaired valve function, and in which segment?
• Are the deep veins patent?
• Are there signs of previous thrombosis?
• Is it necessary to assess the pelvic veins and possible compression?
• Is monitoring, compression, or a procedure suitable for me?
• How long should I wear compression hosiery if it is needed?
• Which physical activities and restrictions are relevant specifically to my case?

For general information about risk factors, you can also read the material on thrombosis and air travel. However, an article does not replace an in-person assessment, especially if the symptom has appeared recently or is changing quickly.

When to Seek Urgent Medical Care

Do not wait for a scheduled examination if the following suddenly appear in one leg:

• rapidly increasing swelling;
• new pain or pronounced pressure;
• noticeable redness and a localized increase in skin temperature;
• sharp tenderness along the vein;
• sudden bluish discoloration or unusual paleness of the limb;
• swelling combined with shortness of breath, chest pain, a feeling of not getting enough air, or coughing up blood.

These symptoms require urgent in-person medical attention. Do not try to determine the cause yourself and do not apply heat to the leg. A sauna, intensive massage, and physical exertion may be inappropriate before examination.

Myths and Mistakes

Myth: If varicose veins occur in only one leg, the problem is not serious.

Unilateral symptoms only indicate how the changes are distributed. They may be associated with anatomical asymmetry, but they also occur after thrombosis or when outflow is impaired. The results of vein duplex ultrasound and the examination matter, not the number of legs with visible veins.

Mistake: Treating a visible vein with a cream without checking the deep system.

A cream may temporarily reduce dryness or discomfort, but it does not correct venous valve function or show the cause of swelling. First, it is necessary to determine the anatomy and the source of reverse blood flow.

Mistake: Assuming that an examination is unnecessary if there is no pain.

Venous changes may remain limited for a long time to heaviness, marks from clothing, or noticeable veins. The absence of pain does not rule out problems with venous outflow.

The practical sequence is simple: for stable unilateral changes, schedule an in-person examination and vein duplex ultrasound, prepare information about injuries, pregnancy, and thromboses, and then choose a treatment plan together with the doctor. If swelling, pain, or a change in color appears suddenly, seek urgent medical care. Appointments at M-Clinic can be scheduled by phone at +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.