Deep Vein Thrombosis: Prevention, Diagnosis & Treatment

DVT most commonly occurs in the calf, thigh, or pelvis. Symptoms, when present, include unilateral leg swelling (one leg swells, the other remains normal), pain or tenderness in the calf or thigh — often described as cramping or aching — warmth and redness over the affected area, and skin discolouration ranging from red to bluish. Crucially, up to 50% of DVTs produce no symptoms at all. The first clinical presentation may be pulmonary embolism, which manifests as sudden breathlessness, pleuritic chest pain (sharp pain on breathing), coughing up blood (haemoptysis), rapid heart rate, or in severe cases, collapse. Any sudden breathlessness or chest pain requires immediate emergency evaluation.

DVT develops when conditions favour clot formation — classically described as Virchow's triad: venous stasis (slowed blood flow), hypercoagulability (increased tendency to clot), and endothelial injury (damage to the vein wall). Key risk factors include:

Clinical assessment alone is unreliable — DVT cannot be confirmed or excluded by symptoms and examination. The Wells Score is used to estimate pre-test probability and guide investigation. A D-dimer blood test is highly sensitive but non-specific: a negative result in a low-probability patient effectively excludes DVT, while a positive result requires imaging. Compression duplex ultrasound is the definitive diagnostic test — the affected vein fails to compress fully under probe pressure, confirming thrombosis. For suspected pulmonary embolism, CT pulmonary angiography (CTPA) is the standard investigation.

The cornerstone of DVT treatment is anticoagulation — blood-thinning medication that prevents the clot from extending and allows the body's natural fibrinolytic system to dissolve it over time. Direct oral anticoagulants (DOACs) — specifically apixaban, rivaroxaban, or edoxaban — are the first-line treatment for most patients. They are as effective as warfarin, easier to dose (fixed doses, no frequent blood monitoring), and have fewer serious bleeding complications. Treatment duration depends on whether the DVT was provoked or unprovoked: a provoked DVT (following surgery or immobility) typically requires 3 months of treatment; an unprovoked DVT requires a minimum of 3–6 months with a formal assessment of recurrence risk thereafter; cancer-related DVT is typically managed with indefinite anticoagulation.

In selected patients with extensive proximal DVT (involving the iliac or femoral veins), or when the clot threatens the limb, catheter-directed thrombolysis (CDT) or mechanical thrombectomy may be considered. These are catheter-based procedures performed by a vascular medicine specialist or interventional radiologist that rapidly dissolve or remove the clot, reduce the risk of post-thrombotic syndrome, and restore venous patency. They are not appropriate for all patients and are reserved for specific clinical scenarios.

DVT prevention is as important as its treatment, particularly in high-risk situations. During long-haul travel, staying hydrated, walking the aircraft aisle regularly, and wearing graduated compression stockings significantly reduce risk. High-risk travellers should discuss prophylactic anticoagulation with their doctor before the flight. After surgery, early mobilisation is the most important preventive measure, supplemented by mechanical compression devices during the operation and prophylactic anticoagulation for 10–35 days following high-risk procedures such as hip or knee replacement. In everyday life, avoiding prolonged sitting (standing up and moving every 1–2 hours), maintaining a healthy weight, and staying physically active all contribute to healthy venous circulation.