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Deep vein thrombosis

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Definition

A thrombus in a deep vein. Woo.

Epidemiology

Common.jpgIt's common. You can get it. It's bad when you do get it because it can lead to a PE.

Pathophysiology

Essentially, keeping blood viscous is an active process. When veins are damaged, when blood stops moving it forms clots. (There's some clever physiology as to why that's true but I've forgotten it.)

These clots fly up the IVC and usually end up getting lodged in the lungs, causing a PE - that's why DVTs are so dangerous.

Risk Factors

There are lot so things that increase your risk of forming a DVT. They are basically split into the three categories: venous stasis, hypercoagubility and/or injury to vein intima. Each factor is either high, medium or low risk:

High risk

  • Previous venous thrombo-embolism
  • Recent surgery (particularly abdominal or lower limb)
  • Cancer (particularly abdominal or lower limb)
  • Immobilisiation
  • Others: antiphospholipid syndrome, increased haematocrit, thrombphilia

Medium risk

  • Some types of chemotherapy
  • MI
  • CHF

Low risk

Pregnancy, COCP, tamoxifen, leg casts or other localised immobility, hyperlipidaemia, IBD (increased activity of a bunch of stuff involved in clotting)

Clinical Features

Classically, you get a unilateral, lower limb, painful, hot swelling. Skin discoloration, low-grade fever, superficial vein distention (due to the blood trying to find another way aroud) are also all clinical features.

The important differential is cellulitis.

Investigations

Bloods

D-dimer is the first test to do. It very sensitive but it is not specific (i.e. high number of false positives). What this means in practice is that you can rule out a DVT but you CANNOT DIAGNOSE a DVT solely on the basis of this test.

Other tests include:

  • FBC - cellulitis, polycythaemia, endocarditis (in drug users)
  • U+Es -
  • LFTs - anticoagulants are a likely treatment so the liver needs to be in tip-top shape. Also, DVTs are common in drug users.
  • Clotting - as above
  • INR - in case you start warfarin

Diagnosis

Ultrasound is the test of choice. However, MRI and CT venography are also options. The gold standard is contrast venography but that's effort and has high morbidity and mortality.

Management

Low-molecular weight heparin (enoxaparin) is given to anybody where there is suspicion of DVT. Essentially, if you're in doubt, give it.

Warfarin is given to those with a confirmed diagnosis. You also need to add:

  • Compression stockings - these reduce the risk of clot formation
  • Filters - well, consider them but they're actually pretty rubbish. They sit in the IVC and stop clots getting to the lungs.

Prognosis