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A blood clot that has formed inside an intact blood vessel – as distinct from one that has form to seal the wall of a blood vessel after injury (see blood clotting).

A thrombus is life-threatening if it grows to obstruct the blood supply to an organ such as the heart or brain. Even a thrombus in a less vital blood vessel can be dangerous because it can produce gangrene in part of an organ or extremity served by the blood vessel, or lead to embolism, in which a fragment of the thrombus breaks off and is carried to obstruct the blood circulation elsewhere.

Related entries

   • deep vein thrombosis
   • stroke
   • thrombocythemia and thrombocytosis
   • thrombocytopenia
   • thrombosis
   • varicose veins

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