Category: 4. DVT Ultrasound Anatomy and Protocol

• Continue to scan slightly more distal from the popliteal vein to find its trifurcation.

Compress the popliteal vein periodically until you find where the popliteal vein trifurcates into the anterior tibial, peroneal, and posterior tibial veins. This junction signals the end of the examination.

• Move the probe into the posterior crease of the knee and scan 2 cm above and below to find the popliteal vein.
• Tip: Sometimes it is difficult to locate the popliteal vein when you first start scanning. An easy way to locate it is to place the probe directly in between the two hamstring tendons behind the knee.

• Use the probe to compress the popliteal vein and check for clots.
• Editor’s Note: Notice in this view that the popliteal vein is now on top and the popliteal artery is on the bottom. Think “Pop on Top!“

Compressible Popliteal Vein. Remember Pop on Top!

• Slide the probe 1-2 cm down the patient’s leg to find where the CFV branches into the deep femoral vein and (superficial) femoral vein.

• At this point, the deep femoral vein will dive deep in the thigh. However, the (superficial) femoral vein will travel alongside the femoral artery.
• Compress the (superficial) femoral vein just distal to the bifurcation.
• Optional: though the 3-point ultrasound protocol only requires you to compress just distal to the bifurcation, you can also periodically check for clots in the rest of the (superficial) femoral vein using compression as you gradually move the probe inferiorly and medially towards the popliteal fossa where the (superficial) femoral vein dives into the adductor canal.

• Slide the probe 1-2 cm down the patient’s leg to find where the great saphenous vein branches off of the CFV.

• Keep the vessels centered in the image. As the probe moves distally, the artery will typically bifurcate first and then the vein.
• Compress the CFV at the junction with the Great Saphenous Vein.
• Editor’s Note: Depending on the size and proximity of a clot in the great saphenous vein to the CFV, there is evidence that these should be treated as DVT too.

• Apply gel onto the probe and place it along the inguinal ligament midway between the pubic symphysis and the anterior superior iliac spine (ASIS).
• Orient the probe perpendicular to the skin with the indicator facing the patient’s right to obtain the transverse view.

• Locate the common femoral vein and artery.
  • Notice the CFV is medial to the CFA.
• Apply firm pressure with the ultrasound probe until the artery compresses slightly. In a normal scan, the vein should compress entirely.

• Locate the common femoral vein and artery.
  • Notice the CFV is medial to the CFA.
• Apply firm pressure with the ultrasound probe until the artery compresses slightly. In a normal scan, the vein should compress entirely.

The 3-Point DVT Ultrasound Protocol

In this section, we will go over a step-by-step ultrasound approach to evaluate for deep vein thrombosis by visualizing the veins and using venous compression using a standard DVT Ultrasound Protocol.

It is important to note that there are several published protocols using anywhere from a 2-point ultrasound scan to a whole leg scan. We have found a 3-point compression ultrasound protocol to be most feasible while maintaining similar sensitivity and specificity when compared to a whole leg scan (Lee, Lee & Yun). We will focus on performing the 3-Point Ultrasound scan in this post, but here are the differences between the protocols that you may encounter:

2-Point Lower Extremity DVT Ultrasound: compression ultrasound including the femoral vein 1 to 2 cm above and below the saphenofemoral junction and the popliteal vein up to the calf veins confluence.

3-Point Lower Extremity DVT Ultrasound: compression ultrasound including the femoral vein 1 to 2 cm above and below the saphenofemoral junction, 1 to 2 cm above and below the bifurcation of the common femoral vein into the deep femoral vein and the (superficial) femoral vein, and lastly the popliteal vein up to the trifurcation into the anterior tibial vein, the posterior tibial vein, and the peroneal vein (Garcia 2018).

Whole Leg/Complete Lower Extremity DVT Ultrasound: involves scanning the leg using compression, color Doppler, and pulse wave Doppler from the common femoral vein all the way to the ankle while evaluating the calf veins.

Proper Vein Compression Technique

One of the biggest issues with performing DVT ultrasound is knowing how much to compress the vein. If the operator does not apply enough pressure or if the ultrasound probe is not perpendicular, these can lead to false positives for DVTs.

You should apply pressure until the pulsatile artery compresses slightly. If the adjacent vein compresses completely, there is no DVT. Refer to the figure below for an example of proper technique. If the vein does not compress completely, it is likely the patient has a clot in that region.

Note: There is a theoretical risk of dislodging a clot and causing a pulmonary embolism with compression. This is a rare complication, but something you should be aware of.

The venous anatomy of the lower extremity is fairly simple. Going from proximal to distal, here are the most important veins in the leg you will need to know for DVT ultrasound:

1. Common Femoral Vein (CFV)
2. Great Saphenous Vein
3. Bifurcation of CFV into Femoral Vein (previously named Superficial Femoral Vein) and Deep Femoral Vein
4. Popliteal Vein
5. Trifurcation of the Popliteal Vein
   1. Anterior Tibial Vein
   2. Posterior Tibial Vein
   3. Peroneal Vein

The most proximal vessel is the Common Femoral Vein (CFV), which gives off an important superficial branch known as the great saphenous vein. The CFV continues on to give off a deep femoral vein, and a femoral vein.

Editor’s Note: The Femoral Vein is also previously known as the Superficial Femoral Vein. Don’t be misled by the name – the (superficial) femoral vein is actually part of the deep venous system. A study from 2011 showed that 75% of junior clinicians believed this vein was a part of the superficial venous system (Thiagarajah, Venkatanarasimha & Freeman). A clot in the (superficial) femoral vein is in fact a deep vein thrombosis and requires anticoagulant therapy to prevent a pulmonary embolus. Don’t get confused by the nomenclature!

As the femoral vein travels inferiorly and medially, it enters into the adductor canal and passes posterior to the knee to become the popliteal vein. At the level of the calf, the popliteal vein gives rise to three other deep veins: the anterior tibial vein, the posterior tibial vein, and the peroneal vein (Zitek, Baydoun & Baird).