A thrombosis occurs when a blood clot (thrombus) forms inside a blood vessel, impeding or completely blocking blood flow. This condition most commonly affects the veins in the legs, and less frequently, arteries or other vessels. If a thrombus is not detected in time, it may detach and travel through the bloodstream to other organs – in the worst case, reaching the lungs and causing a pulmonary embolism.
Causes and Risk Factors
A thrombosis develops when the balance between blood coagulation and blood flow is disrupted. The main causes are summarized in the so-called Virchow’s triad:
- Slowed blood flow – for example, due to lack of movement, prolonged bed rest, long-distance travel, or casts
- Vessel wall changes – such as those caused by injury, inflammation, or surgery
- Increased blood clotting tendency – caused by congenital clotting disorders, hormones (e.g., oral contraceptives), pregnancy, or cancer
Major risk factors include obesity, smoking, advanced age, high blood pressure, diabetes, and a history of thrombosis.
Symptoms – How Does a Thrombosis Manifest?
The severity of symptoms can vary depending on the location. Typical signs of a venous thrombosis, especially deep vein thrombosis (DVT) of the legs, include:
- Swelling of one leg (or arm)
- Sensation of tightness and pain, especially in the calf or when walking
- Redness or bluish discoloration of the skin
- Warmth in the affected area
- Visible, prominent superficial veins
In cases of superficial thrombophlebitis (inflammation of superficial veins), redness, pain, and a palpable hardening along the vein’s course are common.
Diagnosis
Diagnosis is based on a combination of clinical examination and imaging techniques:
- Duplex or compression ultrasonography: The standard procedure for visualizing veins and blood flow.
- D-dimer test: A laboratory test that, when elevated, suggests the presence of a possible thrombosis.
- Phlebography (X-ray imaging): Used only in specific cases when ultrasound results are inconclusive.
Treatment of Thrombosis
The goal of therapy is to stop the clot from spreading, prevent embolisms, and restore normal blood vessel patency.
Acute Treatment
- Anticoagulation (blood thinning): Standard therapy with heparin or direct oral anticoagulants (DOACs).
- Compression therapy: Compression stockings improve venous return and reduce swelling.
- Movement instead of bed rest: Early mobilization is encouraged to avoid long-term complications.
Additional Measures
- Thrombolysis: In severe cases, the clot may be dissolved with medication.
- Thrombectomy: Surgical removal of the clot in cases of imminent tissue damage or extensive thrombosis.
Aftercare and Prevention
Following a thrombosis, several months of medication with anticoagulants are usually required, typically for 3 to 6 months. In certain cases – for example, with genetic clotting disorders or recurrent thromboses – long-term therapy is necessary.
Preventive measures include:
- Regular physical activity, especially during long periods of sitting or travel
- Staying well hydrated to keep the blood fluid
- Compression stockings for at-risk individuals
- Early mobilization after surgery
- Treatment of underlying conditions such as diabetes or heart failure
Possible Complications
If left untreated, a thrombosis can lead to serious consequences:
- Pulmonary embolism, if part of the clot breaks loose and travels to the lungs
- Post-thrombotic syndrome, a chronic venous insufficiency with swelling, skin changes, or leg ulcers
- Recurrent thrombosis due to insufficient anticoagulation
Regular follow-up and monitoring of coagulation levels help reduce the risk of complications.
