Thrombosis – When a Blood Clot Forms

Thrombosis occurs when the balance between blood clotting and blood flow is disrupted. The main causes are summarized in what is known as Virchow’s triad:

• Slowed blood flow—for example, due to lack of exercise, being bedridden, long trips, or casts
  
  
• Altered blood vessel walls—e.g., due to injuries, inflammation, or surgery
  
  
• Increased tendency of the blood to clot—due to congenital clotting disorders, hormones (e.g., the birth control pill), pregnancy, or cancer
  
  

The most important risk factors include obesity, smoking, advanced age, high blood pressure, diabetes, and a history of thrombosis.

Depending on the location, symptoms can vary in severity. Typical signs of venous thrombosis, particularly in the deep veins of the leg (DVT), include:

• Swelling of a leg (or arm)
  
  
• A feeling of tightness and pain, especially in the calf or when stepping down
  
  
• Redness or bluish discoloration of the skin
  
  
• Warmth in the affected area
  
  
• Visibly prominent superficial veins
  
  

Superficial thrombophlebitis (inflammation of superficial veins) is characterized by redness, pain, and a palpable hardening along the course of the vein.

The diagnosis is made through a combination of clinical examination and imaging studies:

• Duplex or compression ultrasound: A standard procedure for visualizing the veins and blood flow.
  
  
• D-dimer test: A laboratory test that indicates possible thrombosis if levels are elevated.
  
  
• Phlebography (X-ray imaging): Used only in specific cases when ultrasound does not provide clarity.
  
  

The goal of treatment is to stop the clot from spreading, prevent embolisms, and restore blood flow in the vessel.

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 recommended to prevent long-term complications.
  
  

Additional measures

• Thrombolysis: In severe cases, the clot can be dissolved with medication.
  
  
• Thrombectomy: Surgical removal of the clot in cases of impending tissue damage or massive thrombosis.
  
  

After a thrombosis, several months of follow-up treatment with anticoagulants is necessary, usually lasting 3 to 6 months. In certain cases—such as genetic clotting disorders or recurrent thromboses—long-term therapy is required.

The following measures can help prevent thrombosis:

• Regular exercise, especially after prolonged sitting or traveling
  
  
• Drinking plenty of fluids to keep the blood thin
  
  
• Compression stockings for at-risk patients
  
  
• Early mobilization after surgery
  
  
• Treatment of underlying conditions such as diabetes or heart failure
  
  

If left untreated, a thrombosis can lead to serious consequences:

• Pulmonary embolism, if a piece of the thrombus breaks off and travels to the lungs
  
  
• Post-thrombotic syndrome, a chronic venous insufficiency characterized by swelling, skin changes, or open leg ulcers
  
  
• Recurrent thrombosis due to inadequate anticoagulation
  
  

Regular follow-up care and monitoring of coagulation levels reduce the risk.