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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
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
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
|Active cancer (treatment ongoing or within previous 6 months or palliative)||1|
|Paralysis, paresis or recent plaster immobilization of lower extremities||1|
|Recently bedridden for more than 3 days or major surgery within 4 weeks||1|
|Localized tenderness along distribution of the deep vein system||1|
|Entire leg swollen||1|
|Calf swelling by more than 3 cm when compared with asymptomatic leg||1|
|Collateral superficial veins||1|
|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
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
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:
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