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Thứ Ba, 21 tháng 8, 2018

Deep Vein Thrombosis [D V T]

Deep vein thrombosis


https://radiopaedia.org/articles/deep-vein-thrombosis

The term deep vein thrombosis (DVT) is practically a synonym for those that occur in the lower limbs. However, it can also be used for those that occur in the upper limbs and neck veins. Other types of venous thrombosis, such as intra-abdominal and intracranial, are discussed in separate articles.




The majority of deep venous thromboses occur in the lower extremities and begin in the soleal veins of the calf. Doppler compression sonography is the imaging modality of choice.

Features include:
  • non-compressible venous segment
  • increased venous diameter: acute thrombus
  • decreased venous diameter: chronic thrombus
  • loss of phasic flow on Valsalva manoeuvre
  • absent colour flow: if completely occlusive
  • increased flow in superficial veins
  • lack of flow augmentation with calf squeeze
  • anechoic thrombus: acute thrombus
  • echogenic thrombus: chronic thrombus

  Key Points

© Springer International Publishing AG 2018

A. Creditt et al., Clinical Ultrasound,  
https://doi.org/10.1007/978-3-319-68634-9_14


  Using point-of-care ultrasound to evaluate patients  in the emergency department has been shown to decrease length of stay when compared with patients who receive studies performed by the radiology department [4].
  Classically the femoral vein lies medial to the femoral artery; however, a common anatomic variant is for the femoral artery to travel anterior to the femoral vein [1].
  Veins collapse easily with pressure. If you cannot visualize a vein, apply less pressure with the transducer.
  Apply direct and even pressure over the vein to assess its compressibility:
  – A false-positive DVT can be diagnosed if uneven pressure is applied, therefore, resulting in an inability to completely compress the vein.
  – This can also occur with patients who have larger body habitus as it is harder to apply direct and even pressure.
  Noncompressible veins can also be seen with chronic DVTs:
  – When a DVT re-cannulates, it can cause the walls of the vein to become stiffer and less responsive to compression.
  Do not rely on visualization of the clot for diagnosis of a DVT as the appearance changes with maturation:
  – If a vein does not completely compress, this is diagnostic of a DVT even if no thrombus is visualized within the lumen [2].
  While a chronic DVT may appear more echogenic with thickened irregular walls, these findings may not be present and it may not be possible to distinguish an acute from a chronic thrombus [3].
  Point-of-care ultrasound for DVT without the use of color Doppler can be less reliable in patients with recurrent DVT:
  – Approximately 50% of ultrasounds can be abnormal 1 year after initial diagnosis of a DVT [5].
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