Mastering a basic lower extremity arterial duplex protocol

There are five steps to performing a basic lower extremity arterial duplex ultrasound:

1. Prepare and position the patient for the examination.
2. Locate the Mickey Mouse view in the transverse plane.
3. Examine the common femoral artery (CFA) in the longitudinal view.
4. Examine the profunda femoris artery (PFA) and superficial femoral artery (SFA).
5. Examine the popliteal artery.

Let’s take a look at each of these steps in a little more detail.

Start by warning the patient that the exam initially requires the probe to be placed in their groin. Then, have the patient lie supine on the table and tuck a towel or washcloth into their underwear to keep the gel off of it.

Next, ask the patient to relax and bend their knee out to the side in a frog-legged position. Keep in mind that too much of a bend can make it difficult to find the popliteal artery.

As you begin the examination, the first thing you’ll be looking for is the Mickey Mouse view of the common femoral artery (CFA) in the transverse plane. Start by placing your probe in the middle of the slightly lateral inguinal crease. Slide the probe in the crease medially towards the inner thigh and you will cross the CFA.

Turn your probe 90° clockwise. Remember, this will move the notch towards the patient’s head so that you can obtain a longitudinal view of the artery. In the longitudinal view, look for plaque and aneurysms on two-dimension (2D) and color modes. Then, Doppler for a waveform.

Evaluate the PFA off of the CFA bifurcation, and then the proximal, middle, and distal SFA. Ideally, you want to slowly track the arteries in the longitudinal view (with color) to continuously evaluate the entire artery. This takes practice because you can easily slide off the artery and miss a segment. But, it’s the most effective way to locate stenosis. If you slide off, you can go back into the transverse view and locate the artery again.

If there is a blockage, waveforms can help you locate the blockage even if you don’t actually see it on the duplex ultrasound.

Next, evaluate further down the leg by placing the probe behind the knee. Evaluate the entire popliteal artery behind the knee by moving the probe down the calf until the vessels bifurcate. Again, this action will produce the black and white 2D images, color images, and Doppler waveforms.

It’s as simple as that!

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