Deep Venous Venous Thrombosis

The bedside DVT scan is one of the most helpful scans that you'll use in the ED. From helping to identify patients short of breath and suspected of having a PE, to the very common unilateral leg swelling, point of care US for DVT is becoming more popular each year. Approximately 260,000 cases of lower extremity DVT are diagnosed each year in the United States alone. These DVTS are thought to lead to nearly 50,000 Pulmonary Embolism deaths per year. Physicians in the United States order almost 500,000 lower extremity duplex ultrasound exams per year to exclude this high-stakes diagnosis.

With peripheral vascular laboratories finding it difficult to staff coverage 24hrs 7days a week, emergency department bedside ultrasound in conjunction with low-weight molecular heparin has made it possible for rapid diagnosis and the ability to send pts home with treatment.

Brief Technique

A high resolution (8-10 MHz) linear array probe is used. The exam should start as proximally as possible just below the inguinal ligament where the common femoral artery and vein should be visualized. The transducer is transverse to the vessels. Slowly move the probe distally to the junction of the common femoral, deep femoral and superficial femoral veins are encountered. Firm compression should be used to fully compress the vein. (If the artery begins to deform, you're using plenty of pressure). If the lumen walls of the vein are able to touch each other COMPLETELY, no DVT is present at this location. Move the probe distally centimeter by centimeter down the Superficial Femoral Vein checking for compressiblilty. About 2/3 down the thigh the SFV will be difficult to see as it dives into the Adductor canal. This is expected, and you may move on to the popliteal vein at this point. Color Doppler is useful if vascular structures are difficult to distinguish initally.

Next check the popliteal fossa by placing the probe behind the knee to assess the popliteal vein which lies superficial to the artery (it will be superior to the artery on the monitor ) Again, check compressibility 1-2 cm up and down the vein. If the popliteal vein does not collapse completely upon compression, DVT is likely present. Use pulse wave doppler, color doppler and power doppler to confirm your diagnosis.

Pitfalls in ED bedside DVT Study

1. Non compressible vein mistaken for artery, leading to a false negative exam.
2. Artery mistaken for a non-compressible vein leading to a false positive.
3. Large superficial veins mistaken for deep veins.
4. Failure to see echogenic clot used to exclude diagnosis. (you don't have to see clot for it to be positive!!)
5. Inguinal lymphadenopathy mistakened for non-compressible common femoral vein (easy to do-- use power doppler).
6. A negative scan for lower extremity DVT does not rule out presence of PE.
7. The superficial femoral vein IS part of the deep venous system (its a misnomer!).



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