Students benefit from a clear step-wise approach to screening for a deep vein thrombosis (DVT). In this video, Elizabeth Tenny, from the Stanford Vascular Lab, focuses on femoral vein imaging and explains where to start the study, what techniques to use, and how to approach anatomical variations.
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Diagnosing and treating a leg vein thrombosis can save your patient’s life, and curing a venous insufficiency wound can prevent leg amputation. After attending this course, you will be confident in performing and interpreting lower extremity ultrasounds to save your patients and their legs. By the end, your new mastery of leg vein ultrasound will make you an invaluable asset to your team.
Learn to use ultrasound to diagnose deep venous thrombosis and demystify venous insufficiency reports.
The deep vein thrombosis or DVT ultrasound begins at the groin and ends at the ankle. Recall that deep veins run adjacent to arteries of the same name. The arteries can be important landmarks for vessel identification. Begin in the right inguinal crease, which is the natural crease in the groin just below the inguinal ligament. Start slightly on the lateral side and slide the probe medially. You will cross the common femoral artery, or CFA, and the common femoral vein or CFV.
Remember that the superficial great saphenous vein, or GSV, joins the deep system through the CFV at the saphenofemoral junction, or SFJ, in the groin. This landmark is known as the Mickey Mouse sign. It includes the common femoral artery as one of Mickey's ears, the common femoral vein as his head, and the saphenofemoral junction as his other ear. This image shows the CFV before compression on the left and after compression on the right.
You should compress the CFV in 2D transverse view to determine if its walls fully coapt. If the walls fully coapt, as shown here, then there is no clot inside preventing compression. If there is not full coaptation, there is something, namely thrombus, in the vein. This first video you are about to see shows a fully compressible CFV, which means there is no thrombus present. You can see that only the artery, or Mickey's right ear, does not compress, which is normal. Turn the common femoral vein into 2D longitudinal or long view to investigate for any intraluminal echoes, looking for any gray or bright tones within the vein that might indicate a thrombus.
Staying in long, press the color button to check for any filling defect that could also indicate DVT. Both images here are normal. At this point, some laboratories prefer to perform a distal augment. Other labs instruct scanners to determine compressibility of all deep veins first and then perform augments at the end in case there is an acute DVT which could potentially become dislodged. For whatever order you prefer, when you are ready to augment, press the pulse wave or PW button for Doppler.
The color and PW are usually combined in one steer box, so adjust that encompassing box until it is slanted the same direction as the vessel. Squeeze the thigh or calf distal to the probe and observe the inverted peak below the baseline, which you will recall represents increased venous return. Importantly, the PW Doppler is used to assess both the phasicity of the waveforms, which can be pulsatile, phasic or continuous, as well as the effect of distal augmentation, so pay attention to both. We will discuss this in detail in the interpretation lesson.
You will be able to see the confluence of the profunda femoris vein, or PFV, and the femoral vein, or FV, just distal to the CFV. In transverse this will look like four circles, the profunda femoris vein adjacent to the profunda femoris artery, or PFA, and the femoral vein adjacent to the superficial femoral artery or SFA. Compress these in transverse view and note both veins coapting. Next, obtain a long color image of the confluence, again checking for any filling defect that could indicate a DVT.
Change back to 2D transverse view and compress the femoral artery every couple of inches, moving to its proximal portion in the proximal thigh. Note that the femoral vein will be underneath the superficial femoral artery on the screen in most cases, as shown in this video of femoral vein compression. There may be a dual femoral vein system. If you see this, then you must test both femoral veins to check if they both coapt. This video shows a dual femoral vein system where only the right vein is fully compressible.
You can see the left vein on the right of the screen is less compressible than the right one as it contains a blood clot. In this example you can even see that the superficial femoral artery at the top partially compressed because so much pressure was applied. Continue to compress the femoral vein every couple of inches down the medial thigh to the mid femoral vein in the mid thigh. After compression at the mid thigh femoral vein, obtain a 2D image in long view, then add color, checking for any filling defects.
Perform PW Doppler phasicity analysis and augmentation if desired at this point. The distal femoral vein dives deep into the tissue and ultrasound depth will likely need to be increased. Record a distal femoral vein compression to check that the vein fully compresses as seen in the right-hand image here where only the artery remains visible after compression. Remember to use your other hand to lift the tissue from under the thigh while pressing down on the probe for the least painful patient experience. After compressing the distal femoral vein as far as possible, you can move on to the popliteal vein. Join me in the next Medmastery lesson where I will show you how to examine the popliteal and other veins below the knee for DVT, as well as the superficial veins.