DVT and PE


Deep Vein Thromobsis is exactly as its name suggests: a clot in the veins. They can occur in any vein, although they are much more likely in the veins of the pelvis and legs. If they occur in other locations (e.g. in the arm) they are often indicative of a more sinister underlying cause (e.g. clotting disorder, carcinoma, or an increased clotting risk of unknown cause) and are more likely to require life-long treatment / prevention. On their own, they are not particularly significant, however, they are dangerous because they can embolise, and cause a pulmonary embolism – these can be fatal.



  • Stasis/immobility – e.g. hospital bed, long flight
  • Dehydration
  • Oestrogen (pregnancy, and to a lesser extent, the COC pill)
  • Genetic clotting defect (e.g. lack of protein C)
  • Obesity (atherosclerosis)
  • Age (old)
  • Varicose veins
  • Surgery
  • Previous DVT/embolism
  • Trauma
  • Infection
  • Malignancy
Virchow’s triad of risk factors:
  • Stasis
  • Hypercoagulability
  • Vessel wall injury

Signs & Symptoms

  • Red, swollen leg (particularly calf)
  • Tenderness
  • Pitting oedema
  • Fever


This is often made clinically, using the Well’s score. Treatment can be initiated in cases of high clinical suspicion without further investigation, although in reality often an USS is used for confirmation. Also be aware that there are two separate Well's scoring systems: one for DVT and one for PE.
  • Score >3 – Treat as DVT – and also perform a compression USS to confirm
  • Score 1-2 – Treat as DVT – and perform compression USS to confirm
  • Score 0 – do a D-dimer test. If negative, then unlikely to be DVT. If positive, Treat as DVT, and perform compression USS.


  • Ruptured Baker’s cyst
  • Cellulitis
  • Lymphadenopathy


A clot develops at a site of damage to a vessel wall (e.g. an atherosclerotic plaque, or perhaps a site of trauma). This can impair venous drainage of the leg. Clots below the knee will rarely embolise, but above the knee, they are far more dangerous. They will often spontaneously resolve over time, however, they are usually treated to reduce the risk of embolism.
  • If they appear in a superficial vein, then they do not embolise, and can be left to resolve, you just have to raise the leg.


  • Venography – this is the gold standard test. A radio-opaque dye is injected into the foot, and then you can see if it is blocked off as it travels up the leg
  • D-dimer – negative test rules out DVT, but a positive test does not diagnose DVT. D-dimer is a breakdown product of fibrin, and can be released by many things,