Thrombosis

A thrombosis is a blood clot which forms in a vein (venous thrombosis) or artery (arterial thrombosis). The blood coagulates when circulating blood is slowed by immobilisation of a limb (leg) or by an obstruction (atheroma).

Consequences of thrombosis

Venous thrombosis may cause phlebitis, obstruction of the venous circulation resulting in pain, local warmth, and swelling of the leg.

Arterial thrombosis may ultimately obstruct the artery and cause ischaemia.

Embolism

In both situations, detachment of the clot and its transport through the blood circulation to other organs is called embolism. The clot then blocks the circulation in organs such as the lung (pulmonary embolism) or the brain (CVA), and can also lead to myocardial infarction.