Dist Fem Vein visualisation challenges

[Linh]

Dear Steve,

For patients with high BMI or with little mobility/bed bound, I find it hard to see the distal fem vein just 15cm AKC to the Knee crease. And it is quite hard to compress the vein at this region. Do you have any tips for direct visualization/ compression window?

A protocol to assess this segment might be taking a spectral trace where the fem vein is seen (as distal as possible) with distal augmentation at just below the knee. If there is phasic flow with sharp peak from the augmentation, can one be confident there is no clot (for example in this case) from 15 cm AKC to KC?

But as I read some more, you can’t be sure that when doing this, there isn’t a partial clot in the distal fem vein (which would give the same spectral trace as if there is no clot) or if there are other branches of the distal fem veins that might have an occlusive clot. So then, under the circumstance that distal fem vein is not seen, what is the value of doing an augmented manoeuvre at the adductor canal if it doesn’t prove anything?

If the trace shows monophasic waveform, then there is a clot proximal to the sample site. But I can only see this being useful for CFV for suspicion of Iliac/IVC occlusive clot. Augmentation distally will show a dampened peak from the CFV if there is indeed a proximal occlusive clot. (correct me if I’m wrong)

Best regards,
Linh

[Stephen Bird]

I agree with your comments here in terms of phasic flow only being useful for CFV. also like to see respiratory variation.
The distal FV is always challenging in larger patients.
I use a convex array transducer which gives me much better image quality and you can push hard on it without causing pain. If you use colour Doppler with the convex you should be able to se flow easily in large patients. Keep the sector width narrow and the colour box small. Low PRF and high colour gain. Augment the cold and you will see good colour filling. With a convex you cannot steer the box, but you don’t need to anyway as there is a nice natural Doppler angle to work with.

Another thing I do with the compression technique is to use my other hand and compress the vein from the poster-medial aspect of the thigh using my hand while also compressing from the anterograde-medial aspect with the transducer.

Also look at your acoustic window. If the sartorius is nice and black you can use it effectively but sometimes it is echogenic and a poor window. If this hapens I take the transducer more medially and use the vests medals muscle belly as an acoustic window.

Steve

[Linh]

Thanks Steve. I do move my probe in various windows and compress with my hand posteriorly. Will try Colour only at that segment next time.

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