Deep vein thrombosis (DVT), pulmonary embolism (PE), venous thromboembolism (VTE)

Deep vein thrombosis (DVT): Thrombus forms within deep venous system, typically in lower limbs

Complete compression ensures no thrombus is present

Thrombus becomes more echogenic as it ages, as well as more linear and cord-like as chronic process

Chronic sequelae of thrombus can cause scarring, decrease in vessel lumen, and chronic reflux and stasis

Loss of respiratory phasicity is suggestive of obstruction closer to heart

Augmentation (↑ in flow velocity with distal compression)

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  Poor augmentation suggests downstream obstruction

Acute thrombosis (~ 14 days)

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  Thrombus hypoechoic, may distend vein if occlusive

  
  
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  May see free-floating thrombus

  
  
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  Collateralization: Tortuous and braided collateral veins, usually smaller than normal vein

  
  
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  Associated slow flow may be seen as visible mobile echoes moving back and forth in real time/cine clip

Subacute thrombosis (~ 2 weeks to 6 months)

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  Thrombus becomes more echogenic, variable

  
  
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  Luminal flow may be restored or vein may stay occluded

  
  
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  Collateral venous channel continues to develop

Chronic phase (≥ 6 months)

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  Postthrombotic scarring forms

  
  
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  Scarred veins are thick-walled with reduced diameter

  
  
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  Plaque-like fibrous scars, synechiae form along vein periphery and may occasionally calcify

  
  
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  Synechiae: Formed from unlysed thrombus that is attached to one side of vein wall and gradually transformed into fibrous band

  
  
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  Fibrous cord: In nonrecannalized vein, vein reduced to echogenic cord smaller than normal vein

  
  
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  Valve abnormalities

Most are treated with anticoagulation or IVC filter, with thrombolysis having role in severe situations

Important to assess if there is any history of prothrombotic risk (congenital or acquired)

Perivascular edema may mimic nonocclusive thrombus especially on compression views; however, look for smooth echogenic intima of vein, which is often more prominent with perivascular edema

Femoral vein (FV) and popliteal veins are often duplicated

If 9 linear transducer is not able to penetrate to level of vein due to patient body habitus or limb swelling, try curvilinear probe

Refractive edge shadow from fascial planes may obscure distal FV; slightly anterior/medial approach using vastus medialis muscle as acoustic window may help visualization

Calcified arteries may obscure visualization of adjacent deep vein and create pseudo filling defect on color Doppler images; avoid using adjacent artery as acoustic window in these patients