Deep Vein Thrombosis [D V T]

Deep vein thrombosis

Dr Yuranga Weerakkody◉ and A.Prof Frank Gaillard◉◈ et al.

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].

Doppler Ultrasonography of the Lower Extremity Arteries

https://www.e-ultrasonography.org/upload/usg-16054.pdf

Doppler ultrasonography of the lower extremity arteries is a valuable technique, although it is less frequently indicated for peripheral arterial disease than for deep vein thrombosis or varicose veins. Ultrasonography can diagnose stenosis through the direct visualization of plaques and through the analysis of the Doppler waveforms in stenotic and poststenotic arteries. To perform Doppler ultrasonography of the lower extremity arteries, the operator should be familiar with the arterial anatomy of the lower extremities, basic scanning techniques, and the parameters used in color and pulsed-wave Doppler ultrasonography.

Doppler US is the only noninvasive technique that does not require contrast enhancement, preparation of the patient before the study, or radiation exposure [1,2]. Doppler US is a good method for screening and follow-up, as well as for the definitive diagnosis of peripheral arterial disease [3-7]. Color Doppler US can easily identify arteries by finding round objects with regular pulsation and can be used to detect stenotic or occluded segments [4,8]. Pulsed-wave Doppler US can show the exact flow velocity of each arterial segment and determine the degree of severity of the stenosis based on an analysis of the pulsed-wave Doppler spectral waveform [9]. Knowledge of the ultrasonographic anatomy of the lower extremity arteries and the corresponding anatomical landmarks is essential for performing Doppler US. In this article, we review the basic scanning techniques of color and pulsed-wave Doppler US for the lower extremity arteries and the spectral analysis of normal and stenotic arteries on pulsed-wave Doppler US.

Conclusion 

Doppler US has been found to distinguish between stenosis with a diameter reduction greater than or less than 50% (corresponding to an area reduction of 70%) with a sensitivity of 77%-82% and a specificity of 92%-98% [18,20-24]. Complete scanning of both lower extremities may require up to 2 hours depending on the operator’s experience [18]. However, if the operator is familiar with the US anatomy of the lower extremity arteries and understands the parameters and Doppler waveforms of Doppler US, accurate diagnostic results can be produced with less scanning time.