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See Also

Peripheral Artery Disease: causes and consequences

Coronary Artery Disease: causes and consequences

Introduction to Deep Vein

This section introduces DVT, its clinical presentation, risk assessment scores and diagnostic strategies

DVT is the formation of a thrombus in the deep veins.1

  • Most commonly in the leg either above (proximal) or below (distal) the knee, or less commonly in the upper extremities
  • May be spontaneous without a known underlying cause (unprovoked/idiopathic) provoked after events, such as trauma, surgery or acute illness (provoked)
  • In the shorter-term, may lead to potentially life-threatening PE
  • Long-term complications may include chronic conditions such as PTS
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Major veins of the lower limb. The most common type of VTE is DVT, which occurs most frequently in veins deep within the muscles of the leg and pelvis

Common symptoms of DVT include:2

  • Leg pain and tenderness
  • Redness
  • Oedema (swelling)



The Wells’ score is commonly used to evaluate the probability of DVT based on a patient’s medical history and physical examination. Clinical judgment plays a critical role because certain DVT risk factors and markers are evident early in the diagnostic process.3,4

Wells’ score for prediction of DVT.3,4 A score of ≥2 indicates that DVT is likely and that the patient should undergo a diagnostic scan
Active cancer (treatment ongoing or within previous 6 months or palliative)1
Paralysis, paresis or recent plaster immobilization of lower extremities1
Recently bedridden for more than 3 days or major surgery within 4 weeks1
Localized tenderness along distribution of the deep vein system1
Entire leg swollen1
Calf swelling by more than 3 cm when compared with asymptomatic leg1
Pitting oedema1
Collateral superficial veins1
Alternative diagnosis as likely or greater than that of DVT–2

Although a high Wells’ score indicates a clinical probability of DVT, an objective imaging technique such as compression ultrasonography, CT venography or MRI must be used to confirm or rule out DVT. D-dimer testing can also be used to rule out DVT.


The flow diagrams below indicate the pathway for confirming or ruling out a diagnosis of DVT after the Wells’ score has been determined, as recommended by the American College of Chest Physicians (ACCP)5,6 and in the UK by the National Institute of Health and Care Excellence (NICE).4

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Flow diagrams showing recommended pathways for diagnosis of DVT after the Wells’ score has been determined4-6

Compression ultrasonography (also called venous ultrasonography or ultrasound) is the most widely used method for evaluating suspected DVT because it is safe and non-invasive.7

  • Involves compressing and imaging the femoral veins down to the most proximal calf veins8
  • Has some limitations but is considered acceptable for confirming suspected DVT when combined with a Wells’ score ≥2 (indicating DVT is likely)4
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Cross-sectional view of the popliteal vein by compression ultrasonography showing partial obstruction of the vessel lumen. This imaging technique renders the thrombus (no flow) as black, whereas areas of blood flow are coloured.

Alternatives to ultrasound are CT venography or MRI:

  • CT venography detects both distal and proximal DVT but is invasive, painful and expensive, and is, therefore, usually used when ultrasound does not support the clinical suspicion of DVT but other assessments do9
  • MRI employs a powerful magnetic field to generate a high-resolution image of anatomic structures. It is non-invasive, but its use can be limited by a long examination time and a lack of access to equipment10



D-dimer is a protein fragment produced by thrombus degradation and it forms when plasmin dissolves the fibrin strands that hold a thrombus together.11 A highly sensitive D-dimer test has high negative predictive value, meaning that it can be used to effectively rule out DVT in a patient with a negative ultrasound scan.4


Next section: Pulmonary Embolism


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