n. obstruction of a vein by a blood clot, without preceding inflammation of its wall. It is most common within the deep veins of the calf of the leg – deep vein thrombosis (DVT) – in contrast to thrombophlebitis, which affects superficial leg veins. Prolonged immobility, heart failure, pregnancy, injury, and surgery predispose to thrombosis by encouraging sluggish blood flow. Many of these conditions are associated with changes in the clotting factors in the blood that increase the tendency to thrombosis; these changes also occur in some women taking oral contraceptives.
The affected leg may become swollen and tender. The main danger is that the clot may become detached and give rise to pulmonary embolism. Regular leg exercises help to prevent deep vein thrombosis, and anticoagulant drugs (such as heparin and warfarin) are used in prevention and treatment. Large clots may be removed surgically in the operation of thrombectomy to relieve leg swelling.
Subjects: Medicine and Health.