Venous thrombosis is a medical condition in which blood clots (thrombi) form within a vein. This condition can occur in any vein but is most commonly found in the deep veins of the legs, a condition known as deep vein thrombosis (DVT). When a blood clot dislodges and travels to the lungs, it can cause a life-threatening condition known as pulmonary embolism (PE). Together, DVT and PE are referred to as venous thromboembolism (VTE).

Symptoms

The symptoms of venous thrombosis can vary depending on the location and size of the blood clot. Common symptoms of DVT include:

• Swelling in the affected leg, usually on one side
• Pain or tenderness in the leg, often starting in the calf
• Warmth in the affected area
• Red or discolored skin

Symptoms of PE include:

• Sudden shortness of breath
• Chest pain may become worse when breathing deeply, coughing, eating, or bending
• Rapid heart rate
• Unexplained cough, sometimes with bloody mucus

Causes

Venous thrombosis is caused by a combination of factors that affect blood flow, blood clotting, and the vein walls. These factors include:

• Venous stasis: Slow blood flow due to immobility, such as after surgery, long travel, or bed rest.
• Hypercoagulability: Increased tendency of the blood to clot due to genetic factors, certain medications, or medical conditions.
• Endothelial injury: Damage to the inner lining of the veins from trauma, surgery, or intravenous catheters.

Risk Factors

Several factors increase the risk of developing venous thrombosis, including:

• Age: The risk increases with age, especially after 50.
• Obesity: Excess weight puts pressure on the veins.
• Prolonged immobility: Extended bed rest or long-haul flights increase the risk.
• Injury or surgery: Trauma or surgical procedures can damage veins or reduce blood flow.
• Cancer: Some cancers and cancer treatments can increase the risk.
• Hormonal treatments: Birth control pills, hormone replacement therapy, or pregnancy can increase the risk.

Prevention

Preventing venous thrombosis involves taking measures to improve blood flow and reduce clotting risk:

• Regular movement: Move around regularly, especially during long trips or periods of immobility.
• Compression stockings: These can help improve blood flow in the legs.
• Lifestyle changes: Maintain a healthy weight, stay active, and avoid smoking.
• Blood-thinning medications: In high-risk situations, doctors may prescribe anticoagulants.

When to See a Doctor

Seek medical help if you experience symptoms of venous thrombosis, like swelling, pain, or redness in one leg, or if you have symptoms of PE. Early diagnosis and treatment are crucial for managing the condition and preventing complications.

Inherited Risk Factors

There are several inherited conditions that increase the risk of venous thrombosis. Some of the most common include:

1. Factor V Leiden: The most common genetic risk factor for venous thrombosis. This mutation makes blood clot more easily.
2. Prothrombin gene mutation: Increases the levels of a protein involved in the clotting process, increasing the risk of clotting.
3. Deficiencies in proteins C, S, or antithrombin: These proteins naturally prevent clotting, and their deficiency can lead to an increased risk of venous thrombosis.

Complications of Venous Thrombosis

If left untreated, venous thrombosis can lead to several complications, including:

1. Post-thrombotic syndrome (PTS): A long-term condition where blood pooling in the legs leads to pain, swelling, and ulcers.
2. Chronic thromboembolic pulmonary hypertension (CTEPH): Long-term high blood pressure in the lungs due to unresolved pulmonary embolisms.
3. Recurrent venous thrombosis: Having one blood clot increases the risk of having another in the future.

Diagnosis of Venous Thrombosis

The diagnosis of venous thrombosis usually involves a physical exam, medical history review, and imaging tests, including:

1. Duplex ultrasound: The first-line diagnostic tool for suspected DVT. It uses sound waves to create images of the veins and assess blood flow.
2. D-dimer blood test: Measures a substance released when a blood clot dissolves. High levels may indicate a clot, but further tests are needed for confirmation.
3. Computed tomography (CT) or magnetic resonance imaging (MRI) scans: Used for diagnosing clots in veins of the abdomen or pelvis.
4. Venography: A less common test where a contrast dye is injected into a large vein, and X-rays are taken to visualize the veins.

Treatment of Venous Thrombosis

Treatment aims to prevent the clot from growing, breaking off, or recurring. It usually involves:

1. Anticoagulants: Also known as blood thinners, these medications reduce the blood’s ability to clot. Examples include warfarin, heparin, and newer drugs like rivaroxaban or apixaban.
2. Thrombolytics: These clot-dissolving drugs are used in life-threatening situations or extensive clots.
3. Compression stockings: Help reduce swelling and prevent post-thrombotic syndrome.
4. Inferior vena cava (IVC) filter: A device placed in the main abdominal vein to prevent clots from traveling to the lungs. It’s used when anticoagulants can’t be taken.
5. Thrombectomy or thrombolysis: Surgical or minimally invasive procedures to remove or dissolve large clots.