Leg vein thrombosis

Leg vein thrombosis is a blood clot or thrombus that closes a vein. This can be fatal, for example if it migrates in the direction of the lungs (pulmonary embolism). To avoid this, here you will learn how to prevent leg vein thrombosis.

Leg vein thrombosis

What is leg venous thrombosis?

Thrombosis often manifests in the leg. Medicine distinguishes between superficial vein thrombosis (thrombophlebitis) and the far more dangerous deep vein thrombosis (DVT). The symptoms can occur in the thigh or lower leg, in the back of the knee or in the calf.

Attention: Leg vein thrombosis often develops without symptoms. The body does not always manage to break down the clot unnoticed. This can lead to a dangerous pulmonary embolism.

In a survey1, the German Society for Phlebology found that almost 50 percent of respondents in Germany do not know what thrombosis is and therefore do not take preventive measures when there is an increased risk.

Development of thrombosis

In this video you will learn how thrombosis develops and what effects it can have.

Causes: How does thrombosis develop in the leg?

Why does a clot form? Blood coagulation is a protective mechanism of the body that protects against bleeding in the event of external injuries: The blood clots and closes the wound. If the blood coagulates in uninjured leg vessels, a clot forms – an obstruction to the blood flow. If the blood’s natural ability to coagulate increases – usually temporarily – the risk of leg vein thrombosis increases.

Virchow’s triad: Main causes of deep vein thrombosis

The Berlin pathologist Rudolf Virchow described the three main causes of deep vein thrombosis in 1856. This is why we speak of Virchow’s triad:

Damage to the vein wall

In the event of injury to the veins, for example as a result of an operation or an accident, the tendency to coagulate is intensified as a natural protective reaction of the body. Blood vessels that have already been affected by leg vein thrombosis are also susceptible to a new blood clot. In addition, the risk of inflammation and tumours is increased. Other factors:

Slowed blood flow

Disrupted blood circulation can affect the flow rate of the blood. A bedridden patient’s lack of movement does not require the pumping effect of the calf muscle, so the blood in the veins flows only slowly and therefore the tendency to coagulate increases. This category also includes:

  • Heart failure
  • Myocardial infarction
  • Restrictive clothing
  • Pronounced dehydration
  • Being overweight
  • Pregnancy / puerperium
  • Job that requires long periods of sitting or standing
  • Long flights or car journeys with the legs bent

Changes in the blood

Medications, for example diclofenac and ibuprofen, as well as other factors, can influence the composition of the blood and therefore trigger thrombosis. These include:

  • Birth control pill
  • Hormone preparations for menopausal symptoms
  • Pregnancy
  • Certain medications such as diuretics, steroids
  • Serious injuries, fractures
  • Cancer
  • Severe inflammation
  • Hereditary blood coagulation disorder

Attention: Approximately 40 percent of all patients suffer from leg vein thrombosis without recognisable triggers.1

Risk factors: These groups of patients are at increased risk of developing leg vein thrombosis:

  • Patients in hospital with and without surgery or injury
  • Cancer patients
  • Patients who are experiencing increased influence of hormones (birth control pills, pregnancy, hormone replacement therapy in the menopause)

In addition, the risk of developing leg vein thrombosis increases with age, with immobility, and in smokers.

Symptoms: What are the signs of leg vein thrombosis?

A blood clot leads to blood congestion. This can lead to swelling of the affected extremity, often accompanied by a feeling of tension. Depending on the location, type and size of the thrombosis, different symptoms arise. In the case of thrombosis in the deep leg veins, sufferers often experience a dull pain, similar to muscle soreness. Other signs:

  • Swelling of the lower or entire leg
  • Overheating of the swollen leg
  • Pain, especially during exercise, for example in the calf when it occurs
  • Tenderness on palpation
  • Red / blue discolouration of the skin
  • Tightness of the skin (the skin “shines”)
  • Possibly visible superficial veins (congestion)

Attention: In many cases, leg vein thrombosis causes little discomfort in the initial phase. This makes it particularly dangerous!

What are the options for preventing thrombosis in the leg?

Diagnosis and therapy: What should you do in the case of leg vein thrombosis?

The aim of therapy for leg vein thrombosis is to dissolve the blood clot. Medicines and physical measures are available for this purpose. Both are used as treatment in combined therapy.

First, the doctor takes a medical history. He or she asks about the patient's medical history and current situation: Is the patient a smoker, were they resting in bed or on a long-distance trip, do they have a history of vascular disease, are there any previous or concomitant diseases? It also excludes other indications which may be confused with thrombosis, such as:

  • Torn muscle (other symptoms)
  • Erysipelas
  • Compartment syndrome
  • Inflammation of the lymphatic system (lymphangitis)
  • Lymphoedema
  • Baker's cyst (synovial fluid in the back of the knee)

The actual diagnosis is made using various methods, for example: Palpation (observation and sensing), MRI, ultrasound. A reliable diagnostic method for leg vein thrombosis is the D-dimer test: D-dimers are fibrin breakdown products that are created in the event of increased coagulation activity. A negative D-dimer test therefore excludes a thrombosis with a high level of probability.

Medicinal therapy – therapy from within

In the case of acute leg vein thrombosis, the patient receives an anticoagulant drug (a blood thinner, for example heparin or Marcumar). This ensures that the blood clot does not become larger and reduces the risk of complication of the pulmonary embolism. Then the body begins to break down the blood clot. Depending on the type of thrombosis, this can take a few weeks to months. During this time, the risk of developing another blood clot is particularly high. Therefore, blood thinners must continue to be taken in tablet form.

Physical therapy with compression – external therapy

Medical compression stockings or compression bandages exert external pressure on the tissue, muscles and veins. They support the return of blood to the heart. At the beginning of thrombosis therapy, the compression stocking helps reduce discomfort and swelling. Early compression therapy may also reduce the incidence and severity of post-thrombotic syndrome (PTS). In the long term, compression stockings can help prevent diseased skin changes in venous patients and the development of a leg ulcer.

If the individual risk factors persist, the patient may suffer further thrombosis. Your doctor will advise you on your subsequent thrombosis prophylaxis.

What kind of doctor treats leg venous thrombosis?

If you suspect that you have leg vein thrombosis, please contact your GP immediately. Don’t delay, because: If the blood clot dissolves, it can lead to a life-threatening pulmonary embolism. If necessary, your GP/family doctor will refer you to a specialist, for example a vascular specialist (phlebologist).

Products by medi: Preventing thrombosis


1 Hofmann J, Nissen H, Strube K. Thrombose und Lungenembolie. Venenratgeber. Deutsche Gesellschaft für Angiologie – Gesellschaft für Gefäßmedizin e. V. 2019;7:12.

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