Thrombosis

Thrombosis is the formation of a blood clot, or thrombus, within a blood vessel, which can obstruct normal blood flow. It may occur in arteries or veins and can lead to tissue ischemia or, in the venous system, to pulmonary embolism if clot fragments migrate to the lungs.

Most thrombosis develops through Virchow's triad: hypercoagulability, hemodynamic changes such as venous stasis, and endothelial injury. Risk factors include advanced age, recent surgery or trauma, cancer, immobilization, pregnancy, estrogen-containing medications, obesity, smoking, and inherited clotting disorders.

Arterial thrombosis often causes sudden limb or organ ischemia and may contribute to heart attack or stroke. Venous thrombosis commonly presents as deep vein thrombosis, typically in the legs (swelling, pain), and can lead to pulmonary embolism when parts of the clot travel to the lungs.

Diagnosis relies on clinical assessment combined with laboratory and imaging tests. D-dimer testing is sensitive but not specific; imaging such as compression ultrasonography is used for DVT, and CT pulmonary angiography or ventilation-perfusion scanning is used for PE. Evaluation of arterial thrombosis may involve vascular imaging and neurological or cardiac assessment.

Treatment centers on anticoagulation to prevent clot growth and new clots, using agents such as heparin, low-molecular-weight heparin, or direct oral anticoagulants. In selected cases, thrombolysis or mechanical thrombectomy may be used. Prevention focuses on risk factor modification, early mobilization after surgery, and, in high-risk patients, appropriate anticoagulation strategies.