Deep Vein Thrombosis

Deep vein thrombosis is the formation of a clot within a deep vein, most commonly in the calf or thigh. It matters because of what it can do next: a fragment breaking loose travels to the pulmonary arteries as a pulmonary embolism, which kills tens of thousands of people annually and can present with sudden breathlessness, chest pain worse on breathing in, or collapse. Risk follows Virchow's triad — stasis (immobility, long flights, hospitalization, casting), vessel injury (surgery, trauma, catheters), and hypercoagulability (cancer, pregnancy, estrogen-containing contraceptives, inherited thrombophilias such as factor V Leiden, and COVID-19). The classic presentation is one-sided: a leg that is swollen, painful, warm, and sometimes reddened or discolored, with calf tenderness. Diagnosis uses clinical probability scoring plus D-dimer and compression ultrasound. Treatment is anticoagulation — direct oral anticoagulants such as apixaban or rivaroxaban have largely replaced warfarin for most patients — typically for at least three months, longer when the clot was unprovoked or the risk factor persists. Long-term, up to a third of patients develop post-thrombotic syndrome with chronic leg swelling, aching, and skin changes.

• •Swelling in one leg, often with a measurable difference in calf circumference
• •Pain or cramping in the calf or thigh, frequently worse on standing or walking
• •Warmth over the affected area
• •Red, bluish, or darkened skin discoloration
• •Visible surface veins and a feeling of tightness or heaviness
• •Emergency signs of pulmonary embolism: sudden breathlessness, chest pain worse on inhaling, coughing blood, rapid heartbeat, or fainting

• •Immobility — hospitalization, surgery, long-haul travel, casting or bed rest
• •Recent surgery, especially orthopedic (hip and knee replacement)
• •Cancer and its treatments — one of the strongest risk factors
• •Pregnancy and the postpartum period
• •Estrogen-containing contraceptives and hormone therapy
• •Inherited clotting disorders (factor V Leiden, prothrombin gene mutation, antithrombin or protein C/S deficiency)
• •Obesity, smoking, increasing age, and a previous clot
• •Central venous catheters and severe infection, including COVID-19

Prevention and treatment both target the clotting process itself. Acutely, anticoagulation stops clot extension and lets the body's own system resolve what is there; catheter-directed thrombolysis is reserved for extensive limb-threatening clots. Duration is decided by cause: a clot provoked by surgery or a cast may need three months, while an unprovoked clot or ongoing risk factor (active cancer, thrombophilia) often warrants indefinite treatment. Prevention works on the same triad — early mobilization after surgery, prophylactic anticoagulation in hospital, compression stockings, movement and hydration on long journeys, and weight and smoking management.