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A venous thrombus is a blood clot (thrombus) that forms within a vein. ''Thrombosis'' is a term for a blood clot occurring inside a blood vessel. A common type of venous thrombosis is a deep vein thrombosis (DVT), which is a blood clot in the deep veins of the leg. If the thrombus breaks off (embolizes) and flows towards the lungs, it can become a life-threatening pulmonary embolism (PE), a blood clot in the lungs. When a blood clot breaks loose and travels in the blood, this is called a venous thromboembolism (VTE). The abbreviation DVT/PE refers to a VTE where a deep vein thrombosis (DVT) has moved to the lungs (PE or pulmonary embolism). An inflammatory reaction is usually present, mainly in the superficial veins and, for this reason this pathology is called most of the time thrombophlebitis. In fact, the inflammatory reaction and the white blood cells play a role in the resolution of venous clots. ==Classification== ''Superficial venous thromboses'' cause discomfort but generally not serious consequences, as do the ''deep venous thromboses'' (DVTs) that form in the deep veins of the legs or in the pelvic veins. Nevertheless they can progress to the deep veins through the perforator veins or, they can be responsible for a lung embolism mainly if the head of the clot is poorly attached to the vein wall and is situated near the sapheno-femoral junction. Clinical trials suggest that fondaparinux, a direct factor Xa inhibitor, reduces extension and recurrence of superficial venous thrombosis, and progression to symptomatic embolism. Since the veins return blood to the heart, if a piece of a blood clot formed in a vein breaks off it can be transported to the right side of the heart, and from there into the lungs. A piece of thrombus that is transported in this way is an ''embolus'': the process of forming a thrombus that becomes embolic is called a ''thromboembolism''. An embolism that lodges in the lungs is a ''pulmonary embolism'' (PE). A pulmonary embolism is a very serious condition that can be fatal depending on the dimensions of the embolus. Venous thromboembolism (VTE) refers to both DVTs and PEs. Systemic embolisms of venous origin can occur in patients with an atrial or ventricular septal defect, through which an embolus may pass into the arterial system. Such an event is termed a paradoxical embolism. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Venous thrombosis」の詳細全文を読む スポンサード リンク
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