Duplex ultrasonography of the superficial venous system is carried out with the patient
standing.
In this episode Michelle Moore demonstrates the correct positioning of the patient, a
standardised sequence to the conduct of the examination, the key anatomical landmarks
in the ultrasound scan and she once again emphasises the key points in optimisation
of the image and flow settings.
The normal direction of blood flow in the superficial veins is from the feet to the
heart.
That is upwards in the standing position.
This depends on the healthy functioning of one-way valves in the veins, which are delicate
folds in the lining of the vein.
If these valve do not function correctly, blood may actually flow downwards in the wrong
direction, a condition called reflux.
Reflux is the most common condition to affect the superficial veins and in this episode,
Michelle concentrates on how to examine for superficial venous reflux.
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Right, so, firstly lets get plenty of jelly on this leg.
We always start at the level of the groin crease and that’s where we are going to
pick up the deep veins and the junction with the long saphenous vein.
To begin the scan we are going to start using a linear transducer.
This enables us to steer our colour flow box and that is much more advantageous to the
curvilinear where the transducer used to have to be rocked by the practitioner rather than
the machine.
So we are going to start in a transverse position and I’m going to start at the level of the
groin crease.
This picks up our junction with the common femoral vein, deep vein, common femoral artery
and the junction, the sapheno-femoral junction and we get our Mickey Mouse sign just there.
So most importantly to start off, is to assess the deep venous system and to check for deep
venous competency.
So turning the probe into a longitudinal position, that’s 90 degrees from the transverse position,
back to the longitudinal position.
This identifies the common femoral vein in longitudinal, this being the patient’s head
and feet and front and back.
To begin we need to press the pulse wave button and centre this in the middle of the vein.
You can see that the angle is appropriate to the vessel walls and this is going to give
us our best Doppler signal.
At the moment the trace is running a normal venous trace with breathing movements noted
and we are going to increase the pressure through the vein and to do this we need to
get a good squeeze on the patient’s leg.
It is inappropriate to squeeze round the front; it’s just not going to provide us with the
correct squeeze.
We need to get in nice and close.
Using your knee, press up against the calf.
Making sure you’re nicely in the centre of the vein and to squeeze the calf and then
quick release.
What we can see now is the initial squeeze and the release and the blood flow cessates
and goes back to normal because those valves are working well.
Moving further down the vein, we can see now that our angle has changed and we need to
appropriately change that angle to meet the vessel walls by manipulating the machine controls.
And again perform squeeze-release.
And again we can see good forward flow and complete cessation of flow demonstrating a
nice deep competent system.
Turning back to our Mickey Mouse sign, we pick up the sapheno-femoral junction.
Turning into a long section, and again perform the same procedure, put pulse wave on, again
the angle needs to be changed to meet the vessel walls.
So what we can see now is the initial squeeze and then a large reflux coming back after
the squeeze demonstrating incompetence of that vein.
To assess the run of the long saphenous or great saphenous vein, back into the transverse
position.
We can see our long saphenous vein sat within the saphenous fascia, identified by the muscle
fascia layer beneath and the saphenous fascia over the top.
It looks like an Egyptian eye.
Optimise our image, reduce the depth and follow down in transverse.
We can see now that the long saphenous vein becomes a little dilated at this point and
we need to measure the A-P diameter of the vein
to ensure that the maximum A-P diameter is within normal limits to allow for any treatment.
So for radiofrequency ablation it needs to be under 20 millimetres in diameter.
So we can see now that this long saphenous vein actually leaves the saphenous fascia
and becomes rather tortuous.
And we can see it wrapping round and around.
Follow down, it’s obviously incompetent but we can check that again a little lower
down.
Then again demonstrating large incompetence of that long saphenous vein.
You can follow this down to the level of the knee.
Here we can see that all of the visual varicose veins are all associated with the initial
incompetence at the sapheno-femoral junction.
So now we are going to move on to have a look at the short saphenous vein and also to check
the popliteal vein for deep vein incompetence distally.
Can I just get you to just turn around for me there?
Just mind yourself, hold on to the bar there.
That’s it.
Keep going round for me a little bit further.
That’s it.
A little bit more.
Fantastic.
Are you OK there?
Ok.
So starting in the posterior knee fossa, will bring up your popliteal vein and the short
saphenous vein, again looking like a little Egyptian eye.
You can pick that up just behind the knee crease.
Turn into a longitudinal section, then we are going to check the competence of the deep
vein.
Again angle the colour wave box, a nice squeeze on the calf and we can see a lovely forward
flow.
And again cessation of flow demonstrating competence of the deep system.
And our short saphenous vein – there is quite a lot of variation of the short saphenous
vein as to the level of the junction with the popliteal vein.
In this gentleman there isn’t actually a sapheno-popliteal junction.
It’s called a Giacomini variant and we can follow the short saphenous vein right up the
way up the calf, up the thigh where it eventually meets
the great saphenous vein.
So the short saphenous vein looks nice and normal in calibre and again we can check the
competency.
Obtaining the short saphenous vein in nice longitudinal section.
So we can see now that this vessel is a bit smaller so our sample volume is too great.
So we need to reduce the size of the sample volume box, and this is going to make the
sample volume much more accurate.
And again we need to angle to the vessel walls.
And again a good squeeze.
Now we can see nice cessation of flow, a little bit of movement, but that’s just because
I’m so close to the area of the probe where we’re squeezing.
Nice cessation of flow and a nice competent short saphenous vein.
Ok, so now we need to assess for calf perforators.
Now we can see, there’s a large deep perforating vein coming from what seems to be the medial
gastrocnemius vein and coming up through here into the fascia with the short saphenous vein,
but not actually affecting it or making become incompetent.
You can see this is the level where it perforates through and we can measure the width of the
incompetent vein.
And we can also prove its incompetence again by doing a Doppler trace.
Again angling to the vessel as it perforates through the muscular fascia.
And a little bit higher, into this varix.
And although it looks very prominent, the incompetence is only a very low level.
Squeezing above the level of the varix can also help to some back flow as we can just
interpret there.
So here we can demonstrate a significantly large calf perforator, we can see it’s a
perforator extending from the medial gastrocnemius vein here and it perforates through the muscle
fascia just there.
So what we are going to do is measure the diameter of the perforator as it perforates
through the fascial layer and we can see that that’s measuring 6 millimetres; and that’s
a significant perforator.
But now we need to check the incompetency of that perforator so see whether it is significantly
incompetent.
Again placing the calliper, pulse wave calliper, in the vessel centre is going to give us our
best measure of incompetence.
We can see we have a little bit of noise just going on here so we just going to reduce our
overall pulse wave just to get rid of that background noise; just by reducing the overall
gain.
And now we’re going to do a little squeeze.
So we can see on that trace that although the vessel is quite dilated, the actual incompetence
is less than 0.5 of a second and that suggests that this actually is an insignificant perforator.
Anything over 0.5 to 1 is low-level incompetence and then greater than 1 you’re going to
be looking at significant incompetence.
So the other way we can demonstrate incompetence during a Doppler scan is by using the colour
flow Doppler and this is going to demonstrate both forward and reverse flow using the red
and blue colour Doppler box.
So to select colour flow, again similar to using the pulse wave we need to ensure that
the colour wave box is angled appropriately to the level of the vessels.
And we can see that we are getting some nice fill within that vessel there but it could
be optimised by reducing the PRF, also known as flow or scale and this helps to show, demonstrate
the filling of the whole of the vessel by reducing the speed needed for the machine
to detect the blood flow within the vessel.
So we can see that under normal phasic respiration, that we have the blue flow and that demonstrates
that the blood is flowing away from the probe and that’s going back up to the heart, in
the correct direction.
And this is our common femoral vein.
To find the great saphenous vein which we have demonstrated previously to be incompetent.
We can place our colour box over the top and we can see that there are some low level echoes
inside here anyway and this is just stagnant blood flow and the quality of the machine
being able to detect those low level echoes within the vein itself.
So again, following a good calf squeeze, we can see initial forward flow, and then we
see the red so this is demonstrating blood flow towards us.
So it is coming back down from the heart, which again demonstrates incompetence of the
valves within the great saphenous vein.