DVT

 

Lecture Topic: POCUS for Deep Vein Thrombosis (DVT)

Overview:

This lecture provides guidance on the performance, interpretation, clinical integration, and limitations of point-of-care ultrasound (POCUS) for DVT. The content is geared toward enhancing the clinical use of bedside ultrasound in evaluating lower extremity DVT.

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Learning Objectives:

By the end of this session, participants should be able to:

1. Define Indications of POCUS DVT Study

   • When to perform a bedside DVT ultrasound (e.g., unilateral leg swelling, pain, high Wells score, concern for PE without clear source).

2. Describe Preparation and Technique

   • Preparation:

     • Patient positioning (typically supine with slight external rotation of hip)

     • Gel and probe selection (linear transducer; use curvilinear for obese patients)

   • Technique:

     • Two-point or three-point compression method:

       • Common femoral vein (CFV)

       • Femoral vein (proximal superficial femoral vein)

       • Popliteal vein

     • Apply gentle compression every 1–2 cm; vein should compress fully—non-compressibility suggests DVT.

     • Scan in transverse (short-axis) view.

3. Interpret the POCUS DVT Study

   • Normal study: Veins are fully compressible; no echogenic material within lumen.

   • Positive for DVT: Incomplete compression, intraluminal thrombus, or lack of flow on Doppler.

   • Additional signs: Lack of augmentation with distal compression or absence of phasicity on spectral Doppler.

4. Define the Limitations

• Limited to proximal DVT (does not rule out distal calf DVT).

• Technically limited in obese patients or those with significant edema.

• Operator-dependent accuracy.

• May miss pelvic or iliac thrombi.

• Cannot definitively differentiate acute vs. chronic thrombus without additional modalities.

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Pearls & Pitfalls:

• Don’t forget to evaluate both legs if bilateral symptoms exist or if concern is high.

• Follow an algorithm: Wells score → POCUS → D-dimer/labs or comprehensive duplex depending on findings.

• Be cautious in non-diagnostic studies—these may still require formal vascular imaging.

Explanation:

• Lymph node – Can appear as a blind-ending, round structure and may be mistaken for a thrombus.

• Baker's cyst – A fluid collection in the popliteal fossa that can resemble a noncompressible vein.

• Superficial vein – Can be mistaken for a deep vein, especially if the anatomy is misidentified.

Compressible deep vein is not mistaken for a DVT—compression confirms it is not a thrombus. A truly compressible vein is normal.

So, this is the exception.

Correct! A compressible deep vein would be part of a negative compression point in a DVU study.

The correct answer is: The anterior and posterior wall coapt

Explanation:

• Patency means the vessel is open and free of thrombus.

• On ultrasound, this is confirmed when the anterior and posterior walls of the vein completely collapse and touch each other with compression — this is called coaptation.

Why not the others?

• "The visualized vessel does not compress" → suggests thrombus is present (i.e., not patent).

• "The anechoic area is self contained" → this is vague and may refer to a cyst or fluid collection, not a criterion for vessel patency.

• "Collapsibility is 50%" → incomplete compression implies possible partial thrombosis → not reliably patent.

Correct: "The anterior and posterior wall coapt" = patency. 

Correct! Coaptation (vessel walls touching eachother) with compression of the anterior and posterior walls of the vessel would be consistent with a normal vessel and no evidence of DVT. Be sure to apply enough pressure as sometimes inability to compress the vessel is simply not applying enough force.

A DVT can be hypoechoic, anechoic or hyperechoic. 

True 

False

Correct! Because DVT can be all of the above, this highlights the importance of compression during the ultrasound exam. With compression, you can identify hypochoic or anechoic DVTs that you may otherwise not have seen without this technique.

Explanation:

A DVT (deep vein thrombosis) can appear as:

• Hypoechoic (darker): Often seen in acute thrombus, which is soft and fresh.

• Anechoic (completely black): Also typical of very acute thrombus, which may lack internal echoes.

• Hyperechoic (brighter): Seen in chronic thrombus, which becomes more organized and fibrotic over time.

Therefore, a DVT can be hypoechoic, anechoic, or hyperechoic, depending on its age and composition.

Correct! Two point compression DVT study is highly sensitive and specific. Further work has been done on this topic and the recommendation is now at least three points of compression (common femoral, common femoral and saphenous junction, deep femoral vein and popliteal vein) as about 10% of DVTs identified would have been missed in the typical two point compression study.

Explanation:

• A blind-ending, hypoechoic, rounded or oval structure in the near field (superficial to the vessel) is most consistent with a lymph node.

  • Lymph nodes often have a hypoechoic cortex and hyperechoic hilum, and they do not compress like veins.

  • They can be mistaken for thrombus if their appearance is not recognized.

Why not the others?

• Femoral nerve – Appears as a hyperechoic, honeycomb-like structure and is usually lateral to the femoral vessels.

• Superficial femoral vein (now called femoral vein) – It is a deep vein, not a blind-ending structure, and lies deep to the femoral artery.

• Saphenous vein – Is a tubular, compressible vessel that joins the femoral vein medially, not a blind-ending structure.

Correct: Lymph node

Correct! Lymph nodes are frequently confused for cysts, abscesses, and clots. They have a characteristic appearance on ultrasound. The appearance of lymph nodes is similar to the appearance of the kidney, just on a much smaller scale. Lymph nodes will have a stalk, vascular supply, are well circumscribed and a relative hypochoic structure within. Placing color doppler on the structure should highlight core vascular structures.