Lower Extremity Veins: Techniques and Interpretation with How To Demonstration

Acute Thrombus

When we find acute thrombus,
the thrombus is brand new or relatively new.
There's a lot of liquid plasma still within that clot, so
that thrombus may appear spongy
or deformable with ultrasound transducer pressure.
The thrombus itself may be koic or hypoechoic,
but you can't rely on the echogenicity alone.
It may be poorly attached.
We may see a tip or tail visible.
The thrombus itself will have smooth borders
and the vein will be dilated
because what happens is as the thrombus starts to form,
that creates an increase in venous pressure more
distal to the thrombus.
That vein will dilate
with the increase in venous pressure.
So the vessel will be quite dilated with acute thrombus.
And here's an example of that.
Here's an artery up here.
Here's the vein.
And you can see
that the vein is very dilated compared
to the companion artery, but relatively anti coic,
and that's consistent with acute thrombus.

This image I showed a few minutes ago of a thrombus here
and this vein, but let's pay attention a little bit closer
to some of the information here.
We have the artery in this view
where it's being compressed is actually being,
slightly compressed itself.
And it's turned from a relatively
circular artery into more elliptical artery.
But the vein has changed as well.
We have a relatively circular vein here,
and the vein has become more elliptical.
That's because it's new and it's what we call spongy.
It's deformable.
Of course, when we see images like this,
we know that we're dealing with an acute thrombus.
Again, real smooth on the borders.
And this tail or tip, sort of just extending into the vessel lumen.

Here's another image of an acute thrombus.
And I think if you look at this quickly,
you can again distinguish up here the muscle bed
and these vessels in the muscle.
There's the gastroc artery,
there's one vein and there's the other.
And this is probably a good four, five times
the size of this vein.
So it is dilated.
And if we were even to look a little bit closer,
I think we can see the edge
of the thrombus here a little bit.
There's a little bit of anti coic lumen.
It's relatively smooth, so we have something that's dilated,
relatively smooth anti coic,
all characteristic
of an acute thrombus.

Chronic Thrombus

Now, when we get chronic thrombus,
chronic thrombus is rigid.
It's firm, it's hard,
It's been there for a while.
The liquid, the plasma has been reabsorbed.
When that liquid gets reabsorbed, all we're left
with is fibrin and some dead cells.
But this is all attached to the vessel wall.
So as the clot itself constricts
or contracts,
because the water's being reabsorbed,
the plasma is being reabsorbed, that
clot actually pulls the walls of the vein with it.
So the vein now looks constricted or contracted,
and is smaller as compared to its companion artery.
The walls of the thrombus, the edges of the thrombus,
I should say itself look irregular.
Maybe hyper coic the main walls too.
And we may see collaterals.
And here is a good image of a chronic thrombus.
Here's the artery.
Here's the vein.
We can see mixed level echoes here,
and a vein that's just about the same size
as its companion artery.

Here's another view of chronic thrombus
where we see this tail.
This just fibrotic material where we have a vein here
that's about the same size as the companion artery,
and again, some chronic residual thrombus.

Comparison of Acute and Chronic Thrombus

So to compare and contrast, generally spongy, smooth surface
dilated versus ridge rigid,
irregular surface contracted.
Those are some of the key characteristics between chronic
and acute thrombus.

Venous Doppler Signals

In terms of the venous doppler signals,
venous doppler signals from the lower extremity should
display these five characteristics.
It should be spontaneous,
it should be phasic with respiration.
It should cease with proximal compression
and augment with distal compression
and should be unidirectional towards the heart.
This is a little bit different in the upper extremity,
but for the lower extremity,
these five things should take place.

Here we have two examples of venous doppler signals.
On the top, we see nice phasic flow.
On the bottom,
we see vasic flow as well, but we've got flow
and the no flow flow and the no flow.
But we're seeing a little bit of super
and impulse pulsations here.
This is just transmitted cardiac pulsations.
It does not represent true pulsatility.
As we are getting cessation of flow in
between these breaths, augmentation,
we should see this augment.
When we do a squeeze, when we do a val Salva,
we should see the flow stop.
And those are all important images
to document when we're doing our doppler signals.

Abnormal Pulsatile Doppler Signals

What if we don't find that in our doppler signals?
What if the doppler signals are slightly pulsatile?
Well, if they're pulsatile
and they're pulsatile bilaterally, this is an indication
of systemic venous hypertension.
There's a lot of things
that can cause systemic venous hypertension, right?
Heart failure, tricuspid insufficiency,
pulmonary hypertension, any of those things
can be present
and will create puls ity within the venous side.
Most folks don't get into things too specifically other than
noting that there's pulsitile signals bilaterally at the common femoral veins.
And you can add in something like it's suggestive
of systemic venous hypertension
or indicative of systemic venous hypertension.

Now, if you only get a pulsatile signal on one leg,
it's probably because there might be some sort of a VF
or arterial venous fistula.
Present could be congenital traumatic iatrogenic.
Any of those will give you a pulsitile signal.
These two types of pulsitile signals differ just a little
bit, but they are going to be something similar to this.
This is in a patient with systemic venous hypertension
where we're seeing beat, beat, beat.
And if we were to move into the companion artery,
we'd see the same type of rhythm placed
within that artery.
Kind of mimicking the venous rhythm here.

Continuous Doppler Signals

Well, if we get a continuous Doppler signal
that's equally abnormal on one leg, we have
to think what's going on with that one leg.
That would create a continuous doppler signal.
A continuous doppler signal comes about
because the pressure in that vein is now increased
and it's increased to a point
where it's exceeding abdominal pressure changes.
So what can increase the pressure in that vein?
What can back it up?
Well, partial DVT or previous DVT
or intrinsic venous compression,
or extrinsic venous compression will also
produce a continuous doppler signal.
If we see a continuous doppler signal bilaterally,
then we have to think further centrally
and that the IVC may be involved either with thrombus
or extrinsic compression.
And here we see a common femoral vein
with a continuous doppler signal.
But we know there's something wrong here.
We see all this thrombus within the vein,
so we have a partial thrombus.
That partial thrombus is not letting all the flow through.
The flow is backing up, it's increasing the pressure,
and it's producing this non vasic doppler signal.
Okay.