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Defil'd with ropy gore and clots of blood… Dismal and cold, where not a beam of light invades the winter.


A thrombus is defined as a clot formed in the circulationfrom the constituents of the blood, whereas emboli arefragments of thrombus that break off and block vesselsdownstream. Almost half of adult deaths in Westerncountries are due to thrombosis of coronary or cerebralarteries, or to pulmonary embolism.1 A thrombus isthe result of a cascade of events involving platelets,RBCs, coagulation factors and the vessel wall.

Conditions predisposing to thrombosis:

  • thrombophilia

  • thrombocytosis (platelets)

  • polycythaemia rubra vera


Thrombophilia refers to a disorder of haemostasisin the form of a primary coagulopathy leading to atendency to thrombosis. This should be consideredin those with major unprecipitated venousthromboembolism with or without a strong familyhistory of venous thrombosis. Several causes can betested, both inherited and acquired:

  • inherited:

    • – factor V Leiden gene mutation (activatedprotein C resistance)

    • – prothrombin gene mutation

    • – protein C deficiency

    • – protein S deficiency

    • – antithrombin deficiency

  • acquired:

    • – antiphospholipid antibodies (anticardiolipin oranti-62 GPI)

    • – elevated homocysteine level

    • – lupus anticoagulant

The above factors can all be measured in thelaboratory with specific genetic, coagulation orantibody-based tests. Other acquired causes (regardedas risk factors) include smoking (the big one),malignancy, oral contraceptives, HRT, immobilisation, obesity, pregnancy and major surgery. Most DVTs donot require investigation for an underlying cause, butconsideration should be given to screening patientswith an unprovoked DVT. Refer to a haematologistif thrombophilia is proven or suspected. Of particularinterest is factor V Leiden, which occurs in about 4%of Caucasians; the relative risk of venous thrombosisis increased three to seven times in heterozygotes and80 times in homozygotes.2

Indications for investigation

  • Recurrent or unusual thrombosis

  • Arterial thrombosis <30 years

  • Skin necrosis, especially on warfarin

  • Recurrent fetal loss

  • Familial thromboembolism

Venous thromboembolism

A feature of venous thrombosis is that it developsin normal vessels, with key factors being stasis andincreased coagulability, including thrombophilia.The classic example is deep venous thrombosis ofthe leg veins. Another poorly recognised thrombosisis axillosubclavian venous thrombosis, which isassociated with pulmonary embolism in 30% of cases.3

Other sites of deep vein thrombosis are the pelvic/ovarian veins, which should be suspected in a personat risk with pelvic pain and swollen upper thighs, mesenteric venous thrombosis and cerebral sinusthrombosis, which are usually due to thrombophilia.

Deep venous thrombosis

Past history is very important.

Risk factors

  • Family history

  • Thrombophilia

  • History of previous thromboembolism

  • Drugs (e.g. OCP, tamoxifen, HRT)

  • Malignancy (watch idiopathic DVT)

  • Increasing age; age >40

  • Varicose veins

  • Significant illness, esp. heart failure and cancer

  • Other chronic illness

  • Recent surgeryMajor/orthopaedic surgery

  • Immobility

  • Long ...

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