Lower Extremity Venous Doppler - SD

Introduction

Good morning.
My name is Sandra Allison. I am currently the director
of ultrasound at Georgetown University Hospital in
Washington DC, and I'll be speaking about lower
extremity doppler.

Overview of Deep Venous Thrombosis Evaluation

This talk is about deep venous
thrombosis and its evaluation.
Even though this is not the favored study
of most sonographers or radiologists, it is important
because prompt diagnosis
of thromboembolic disease is critical as it may lead
to acute pulmonary embolism.
Pulmonary embolism can occur in up to 50% of cases
of untreated DVT
and as such, it is the most common reason
to order lower extremity duplex studies.
As I mentioned earlier, ultrasound is the initial diagnostic
test of choice, and with ultrasound we can visualize
complete or partial occlusion.
We can localize the thrombus,
we can identify whether it is
loosely attached or free floating.
We can also follow progression of thrombus, let's say,
with treatment.
And it is also useful in determining the age
of the thrombus, whether it is acute
or whether there are chronic changes in the vessel.

Objectives of the Examination

So the objective of the examination is first of all
to exclude thrombosis.
And as I mentioned earlier, we want
to determine the location, whether it's attached
or unattached, partial or complete,
and based on its appearance, whether it is acute
or chronic.

Indications for the Study

The indications for the study patients may present
with suspected pulmonary embolism
or they may present with more local symptoms such
as leg pain, swelling, and erythema, the presence
of a palpable cord.
They may present for follow up to
see if the thrombus is responding to therapy.
They may order the study pre or post surgery
or in patients with high risk for deep venous thrombosis.

Risk Factors

The risk factors include any patient who presents with
OSE triad, which includes venous stasis, endothelial damage,
or hypercoagulability patient.
These include patients who've experienced trauma
or surgery, which is a type of trauma
malignancy patients on oral contraceptives,
pregnant patients due to stasis in the lower extremities,
patients with liver failure who are hypercoagulable
or patients with a history of prior DVT.

Anatomy

The point of this slide is to demonstrate
the more central anatomy.
The external iliac vein I'd like to point out is medial
and posterior to the artery.
And you can see that the left vein is compressed
by the right artery, which leads
to increased risk of DVT on the left.

I just wanna point out the anatomy here.
The vessels that we study include the common femoral vein,
The femoral vein, which is formed here
after the confluence
of the deep femoral vein, which is right here.
We have the greater saphenous vein,
which is actually superficial.
It's more central portion is a part of the examination.
And coming down this whiteout area is the vein
as it's passing through the adductor canal.
And then we see here the popliteal vein.

Sonographic Appearance

This is the sonographic appearance.
A few things I wanted to point out.
These are, these images are obtained in the
transverse plane.
And if you see here, the vein is always
slightly larger than the artery at the level
of the common femoral vein.
The vein in the artery lies side by side.
As we come down to the femoral vein, the vein
and the artery are on top of each other.
And as we move posteriorly to the popal vein,
we can again see that the,
the vein is slightly larger than the artery.
Some landmarks, some people refer to this
as the Mickey Mouse view.
This is also obtained in the transverse plane.
We have the common femoral vein, the greater saphenous vein,
the common femoral artery
and deep femoral artery in the long axis.
We also look at the deep femoral vein as it's joining
with a femoral vein to form the common femoral vein.

This is an image obtained from netter demonstrating
the adductor canal.
The adductor canal is formed where the sartorius,
which is this cut muscle crosses over the adductor longus
right here and the vastus medias.
The importance of the adductor canal is this is an area
where the vein and artery dive deep into the thigh
and may be more difficult to image
and more difficult to compress.
You can eliminate this problem
by supporting the thigh posteriorly with your hand
and compressing from anterior with the transducer.
And in transverse, you can see here this is the femoral vein
and the artery as it's traversing the, Dr canal.
It's deeper in location.
And then here is a compression view
with just the artery showing the superficial veins
are not paired with arteries.
And you can see here there is a long access view
of the right greater saphenous vein
and more centrally you can see
that the greater saphenous vein joins
with the common femoral vein.
This is the location where we obtain our image.
One other thing to point out,
sometimes you may see echogenic linear structures projecting
into the lumen of the vein.
These are the valves.
and these are good locations to look for thrombus
as thrombus tends to form here.

Variants

First, Some variants
to be aware about 25 to 35%
of popliteal veins are duplicated or bifid.
Others believe that this may be related
to a high bifurcation of the posterior tibial
and perineal trunks.
20 to 40% of femoral veins are also duplicated.
One clue may be that the vein,
which is normally larger than the artery,
may look slightly smaller.
And then when you see this,
you this would should prompt a search for a second vein
or a duplicated vein.
This, this is also a potential pitfall when evaluating
for deep venous thrombosis
because if you see one patent vein,
you may miss the second duplicated vein that is thrombo.
It's very important to be aware of this variant.

Examination Protocol

Our protocol involves imaging the common femoral vein,
the saphenofemoral junction, which is
where the greater saphenous vein joins the common femoral
vein, the femoral vein, which we image
all the way down into the popal vein.
We also look at the proximal portion
of the deep femoral vein as it's joining
with the femoral vein, obviously we would like to
evaluate anything that appears abnormal,
any ancillary findings in the lower extremity.
There is a controversy,
or at least differences in the way
institutions perform the study.
Some may perform unilateral studies, some may do bilateral,
and there's a large variability in whether the calf
is included in this study.
At Georgetown University, we currently routinely perform,
imaging of the calf veins, which include the perineal
and posterior tibial veins with every study.

Patient Positioning and Transducers

The patients may be scanned, supine
or standing or sitting up.
We can have their legs dangling over the edge
of the stretcher,
and we usually position their legs in a semi
frog leg position.
A five to eight megahertz can be used a linear array
for femoral duplex study,
and we may switch to a higher frequency transducer
for the saphenous.
Since it is more superficial, we may also switch
to lower frequencies for deeper structures such
as the iliac vein or the vena cava if necessary,
or in larger patients, in this case, a four megahertz
or a curved or sector array can be used
for gray scale we use for transverse compression.
And then we can switch to color doppler
to detect non-visible plaque.
It's also good when compression could not be performed
or for finding deeper vessels.

Compression Technique

Now this is a cine loop of transverse compression.
It is the most important part of the examination.
I'm gonna play it again.
Now the vessel that is completely coapting is the vein.
We see the artery is on top
and is very important to apply pressure enough
to coap the vein or to make sure
that the vein wells walls come together.
The principle of this is if the vein walls completely
collapse or come together, then there must not be anything
inside the lumen, and therefore you can ex eliminate
or exclude the diagnosis of thrombosis.
Compression is performed in the transverse plane
because in the long axis during compression,
you the transducer may slide off the vein
and may simulate complete compression
and lead to a false diagnosis.
The vein is compressed every one centimeter all the way down
the leg from the common femoral vein down
to the popliteal vein.
And in some institutions,
the C veins may also be compressed, also augmented
with color and spectral doppler to confirm the presence
or absence of flow.
The one caveat that is that in the presence of
very slow flow,
color doppler may not detect flow.
It can also document the most proximal extent of thrombus.
It may be used in identifying smaller veins
or confirming,
blood flow when compression cannot be performed.

Normal Examination Criteria

We're gonna move on to the criteria for,
a normal study.
A normal vein is completely compressible.
It has a thin and very smooth wall, almost imperceptible
and an koic lumen.
The one exception to this, of course, is
with very slow flow.
The lumen may appear hypoechoic
or may have some internal echoes.
Walls will not coap when the lumen contains thrombus.
And remember again, compression should be performed in the
transverse plane, such as in this image.
Here we have a non compression image
with a vein slightly larger than the artery,
and then just the artery showing
as the vein walls have completely coapted.

Doppler Criteria

The normal criteria for doppler,
there are five important features
of blood flow in normal veins.
First of all, there should always be spontaneous flow.
Even with the extremity independent position,
blood flow should occur towards the heart,
even without muscular compression.
Sometimes in small veins, spontaneous flow is difficult
to detect due to slow flow.
Normal venous flow also changes in response to respiration.
This is sometimes termed respir phasic.
When absent the flow is described as continuous.
This may indicate the presence of obstruction proximal
to the site of Doppler.
Examination
flow can also cease with Valsalva Val salves.
Deep inspiration followed by bearing down.
It can result in cessation of blood flow in large
and medium sized veins.
But this documents patency between the doppler portion
and the thorax
augmentation can be performed
by distal compression with augmentation.
And abrupt increase in doppler frequency shift can be seen
after manual compression of the extremity distal to the site
of ultrasound examination.
An absence of response would indicate a substantial
obstruction distal to the site of Doppler examination.
Delayed or weak augmentation may indicate distal obstruction
that is incomplete or circumvented by collateral vessels.
Currently at Georgetown University,
we do not include this in our examination
as it has not proven reliable for excluding thrombosis.
And in the present, in the setting of a normal study,
augmentation has not proven
to provide any additional information.
Now, in a normal venous system,
blood flows only towards the heart
because of the presence of valves.
Valves permit retrograde. When they permit retrograde flow.
These valves are described as incompetent.
And this is a diagnosis when retrograde flow occurs in
response to Val Salva or manual compression proximal
to the site of ultrasound examination.

Images Obtained

So there's a difference in what is evaluated
and what images are obtained.
We routinely tr compress every centimeter down the length
of the veins being examined.
However, we only take representative pictures
for documentation in the transverse plane.
We obtain images of the common representative images
of the common femoral vein.
We obtain images of the femoral vein in three locations.
And some people would like to designate these as proximal,
mid and distal, but we prefer to
Designate them as central, mid and peripheral.
To avoid any confusion between the anatomic
naming and some other naming systems,
central would mean closest to the heart
and peripheral would mean farthest away from the heart.
We also obtain images of the popliteal vein in transverse
and then in the long axis view,
we take representative images
of the common femoral vein at the saphenofemoral junction
to document the absence
of thrombus in the greater saphenous vein near its
confluence, again, we
obtain images of the femoral vein, the popal vein
and lung axis, and also the confluence
of the common femoral vein with the deep femoral vein.
Again, if there's anything abnormal, obviously we would like
to document that with images as well.

Abnormal Findings

An abnormal study, let's talk about that.
Non compressibility of the vein is the most important
criteria for establishing the diagnosis of thrombosis.
If the vein does not compress,
there is something in the lumen.
Usually the vein is somewhat larger than a corresponding
artery, but if it is even larger than that, then
a thrombus should be suspected.
And sometimes this may be the only sign
of thrombosis on gray scale.
You can see here there is a little bit of thrombus shown,
but you do see that the vein is somewhat larger
or substantially larger than the artery
and thrombus is suspected.
In addition, in the the image on the right, you can see
that there is non compression of the vein
also indicating the presence of thrombus
Free floating or partially attached thrombus
may also be seen on gray scale,
but normally that is much easier
to detect either in the long access view
or with color doppler.
And here's an example of that.
In the long access view, you can actually see that
a large portion of the thrombus is actually not attached
to the vessel wall.
This is sometimes called free floating
or partially attached thrombus.
This is a partially occlusive thrombus
and is at a greater risk for detaching
and embolizing on color.
It has this appearance. You can see here we have the
artery and the vein.
The vein is filled with echogenic material.
It is not substantially larger than the artery in this
image, but you can see that you have the impression
that this is completely occluded with thrombus.
With color doppler, you can actually see
that there is flow around this.
And this was further evaluated centrally.
You can see here's a greater saphenous vein coming in.
We have a little bit more space around this thrombus.
And as you can see here in the iliac veins,
this vein is partially attached.
We usually prefer our technologists
to not compress in the situation
because this type of thrombus is associated
with a greater risk for detaching and embolizing.

And here is a syne Of that thrombus.
And as you can see, it does appear
to be floating within the vessel.
And again, when our technologists see this,
they're instructed to not compress the vein.

Abnormal Spectral Criteria

Let's talk about abnormal spectral criteria.
As mentioned earlier, there should be
respiratory ity to the vein.
And in this image you can see a continuous pattern.
This may indicate that there is an obstruction central
to this or an extrinsically compressing lesion on
the central veins.
Spectral can also be used to confirm the absence of flow,
such as in this case you can see
that the artery is patent on this color doppler image,
but there is thrombus, occupying
and occluding the associated vein
and absence of flow on the spectral image.

Classification of Thrombus

Now thrombus, can be classified as acute.
Some classifications will include subacute,
though there is a lot of overlap between the acute
and subacute phases.
And thrombus may persist up to six months
and therefore it's difficult
to separate these two classifications.
Chronic thrombus is actually a misnomer.
We prefer to use the term chronic changes in the vessel
related to thrombosis.
So this may include, epigenic material such
as a calcified residual thrombus.
The vein may completely occlude and never become patent
and result in a fibrous cord.
There may be wall thickening possibly with calcification.
The wall thickening may prevent
compression, may see a valve abnormality
or acal scarred valve,
and there can be doppler flow abnormalities.
Going back to the acute, acute thrombus tends to be
very low in echogenicity.
Again, in the acute setting, the vein
is substantially larger than the artery.
There is absence of compression
or inability to compress the vein.
Again, we may see free floating thrombus over time
as thrombus ages.
Echogenicity will increase slightly,
but the intensity of the echoes remain low.
Over time, the vein lumen may decrease in diameter,
and this is in the subacute setting.
Thrombus will no longer be free floating,
but become adherent to the vein.
Recanalization may be occurring
and collateral veins may be seen.
The one misnomer
or misconception is that collateral veins take time
to develop and that is actually not true.
Collateral veins can be seen often immediately
after acute thrombosis.
In the subacute setting, collateral veins may continue
to enlarge and in the chronic se setting,
if the vein remains completely thrombose and becomes a
or completely occluded
and becomes a fibrous cord, one pitfall is
to avoid mistaking a large collateral vessel
for a native vein,
usually a collateral vessel will have
an abnormal doppler pattern.
Spectral pattern.

Examples of Abnormal Findings

Here's some examples we have here in the transverse
compression views the right common femoral vein,
which is substantially larger than the associated artery.
We see a little bit of material within the vein,
but you can see that it, there is more than what is
present on the,
or what is visible on the non compression view.
Limiting compression of the vein
in the long axis view, you can see that there is expansion
of the vein compared to its normal diameter.
And in, in the acute setting,
a collateral vein has already formed.
Spectral doppler here will confirm that there is absence
of flow, which is also not detected on the color doppler.

An example of chronic change.
You can see here the vein is the same size
or smaller than the accompanying artery.
The vein wall is echogenic and thickened
and compression is not
Easily Obtained.
Other findings that may be seen calcifications webbing,
which I will show in a second,
or there may just be an echogenic sclerotic cord.
Here's an example of webbing or syne.
They may present as fine linear structures within the
lumen of the vein.
The difference between this and a valve is that syne
may traverse the entire lumen of the vein
or may extend for longer
distances than a typical valve.
As mentioned earlier, collateral formation which may occur
early, can be seen
and these should not be mistaken
for patent veins when they are larger.
Here we see smaller collateral veins in the presence
of a thrombo common femoral vein.
And here are more examples
with collateral vessels around a thrombosis vein.
And again, there is
continuous flow present in this collateral vein,
which should not be confused with a partially
occluded femoral vein.

Ancillary Findings

Moving on to ancillary findings.
Sometimes a patient may present
with lower extremity symptoms
and not have deep venous thrombosis.
Though you may find other reasons
for the patient's symptomatology.
One of the most common findings ancillary findings in a,
in a lower extremity examination is a baker cyst.
And there is,
a jerk reaction when people see a cyst in the popliteal
fossa, they tend to call these baker cysts automatically.
But the one caveat is that in a small proportion
of these patients, synovial sarcomas may present
with the same appearance as a baker cyst.
So we prefer to image what we think are baker cysts
with the three landmarks present.
Now, baker cyst is nothing
but distension of the the
gastroc anemia semimembranosus bursa.
And in order to prove that you are in that bursa, you want
to demonstrate the medial head of the gastroc anemia
and the semimembranosus tendon.
And you wanna show that the fluid is coming from
between these two structures
and extending into the cystic structure.
And here we have the back of the tibia.
So without those landmarks, you don't know
what you you're looking at.
It may be that the patient is post-op
and you weren't informed of this information
and you may be looking at a seroma or resolving hematoma.
And again, in a very small population you may be looking at
a synovial sarcoma.
So I think it would be very important
that you're very strict about showing the landmarks to,
to prove that you are looking at a bigger cyst
in the long access view.
Here you can see that the cyst has rounded margins,
so you know it's under tension
and in this case it's likely intact.
But in this case you can see
that the inferior border is pointed
and you can see fluid tracking in
between the fascial planes of the calf.
This indicates that this cyst is likely ruptured
and this commonly presents with symptoms that mimic
or at least can be confused with deep venous thrombosis
or calf thrombosis.
Edema is a very common finding.
Also you may see interdigitating black lines
or an coic lines, which is fluid within fascial planes
of the subcutaneous tissues.
Oftentimes all you may see is just echogenic appearance
to the subcutaneous fat,
which is normally dark when there is no edema.
Present fluid collections which look very similar to
popliteal cysts, can present in the popliteal fossa
after surgery, but can also present
in the proximal extremity when there is trauma
or recent injections
or in this case a rupture of the quadriceps muscle.
And you can see here our collection with some complexity
because this actually represents a hematoma.
Lymph nodes are commonly found in the groin
and when they are ovoid
or kidney being inha, when there is an intact fatty hilum
or you may see one vascular pedicle, they are
considered normal even when they appear large.
An abnormal lymph node on the other hand becomes rounded.
It may become more hypo coic, it will lose its fatty hilum.
And when dopplers perform, you can see
that there is more flow than just a simple vascular pedicle
Aneurysms can sometimes be incidentally found.
Here we have an example of a right common femoral
artery aneurysm.
The vein is here next to the artery,
but you can see that the artery is much larger than the vein
and there is plaque along the periphery of this artery.
In long axis, you can see
that there is SIF formm dilatation of this vessel.
This is something that we more recently recognized
as a common occurrence
or at least a common presentation for patients presenting
for a DVT study in our department.
Here we have an image,
and just to orient you, this is imaging from behind.
This is the proximal calf
and we have the medial gastroc anemia fibers present here,
which are terminating abruptly here.
And then we have a complex fluid collection
representing a hematoma.
On this panoramic view, we again see this is the medial head
of the gastroc anemia, which is interrupted.
The large hematoma in that area of interruption.
And deep to this is the soleus muscle.
This represents a tear of the medial head
of the gastric anemia, which is actually not that uncommon
and can present with calf pain obviously.
And present to the department for a DVT study.
Another Diagnosis that can present
with very similar symptoms
and in a similar location is a rupture
of the plantars tendon.
So on this image I'd like
to point out this is the plantar tendon,
which is seen medially distally.
It will join and reside in the medial edge
of the achilles tendon.
And it runs in between the sous muscle
and the gastroc anus muscle.
These patients can present
with an elongated fluid collection, which tracks
between the gastroc anus and the sous muscle.
And you can see here on this panoramic view,
the fluid collection tracking again in
between the gastroc anemia and the sous
and a free edge of the plantar tendon distally.
This is a plantar tendon rupture.
This patient also had a medial gastroc anemia tear,
as you can see here, which can occur
in conjunction with the plantar.
But the major pathology
that's present on this patient is the
plantar tendon rupture.
These two entities are not that uncommon.
They can present and often with a very acute history.

One other finding here, patient
with lower extremity edema, no DVT,
but as the vein was being imaged, you can see
that there is an arterialized flow pattern in the vein,
which prompted imaging of the associated popliteal artery.
This is not the normal appearance
to a lower extremity arterial waveform.
This is actually decreased in resistance
and the conjunction of these two findings is most compatible
with an arterial venous fistula.
Sometimes the fistula may not be seen,
but this high arterialized flow in the vein,
is enough to make the diagnosis.
This doesn't occur very often,
but this patient did present with lower extremity pain.
No deep venous thrombosis was found.
However, there is a mass in the tibia,
which is invading the cortex and is within the marrow.
There's a lot of vascularity to this mass.
And this was a Ewing sarcoma diagnosed
during a lower extremity study.
One other thing, commonly presenting in patients
with groin pain who come to our department to evaluate
for common femoral vein thrombosis is, ilio bursitis.
And here we can see a compression view.
We have the artery in the vein.
The vein completely collapses,
but there is an extra structure which is
actually a fluid collection.
And you can see again here we have the artery in the vein.
And then we have a fluid fluid collection deep
to the common femoral vessels.
And you can see it here on this CT scan.
Again, artery and vein and the fluid collection.
This is ilio bursitis.
Oftentimes You may see a cystic structure in the popal
fossa and it may be called a baker cyst.
In this case, the cyst contained several calcified
or ossified bodies residing within the cyst.
And this is a presentation of synovial osteo andro mitosis,
which is confirmed here on this lateral
plain radiograph of the knee.

Pitfalls

This is, this can be tricky in examination.
You can see here on a collar doppler view
of the external iliac vein, there is flow in the artery
but no flow in the vein.
So as I mentioned earlier, compression is actually
the most important part of the study.
And you can see here during compression,
the vein completely coops.
So this is one of the pitfalls, when evaluating
for thrombosis, color can sometimes simulate the presence,
or sorry, the absence of flow.
But really what is happening is there's very slow flow.
And in this same patient you can see that there is
no flow detected on color,
but there is very slow flow detected
on the spectral doppler.
Here we have it again, and this is the same pattern
demonstrated all the way down the extremity.
But when we augment, there is suggestion
that there is no obstruction.
So when you see this loss of ity
or a continuous waveform, very slow flow, what you need
to do is look for a central obstructing process
or a central extrinsically compressing process.
And in this patient who presented
with these findings bilaterally,
there are bilateral lympho seals which are compressing the
veins in this patient who had surgery,
for prostate cancer.

So just going back to some of the pitfalls again, just
what we just saw is slow flow may mimic absence
of flow on the color Doppler images I talked about earlier.
Com compression difficulties with thickened veins
or veins with chronic changes from prior thrombosis.
A mistaken identity of a collateral vessel
or a superficial vein may give a false
negative diagnosis in the setting of a duplicated system.
The presence of one patent vein
may result in a negative study with, non-identification
of the paired thrombosis vein.
Chronic changes should not be called chronic thrombus,
mainly because referring physicians may see the word
thrombus and,
start treatment recurrent.
DVT can sometimes be difficult
because there'll be chronic changes
with a superimposed acute changes.
And, poor venous distension
and reduced flow may also result in a false diagnosis.
Here's an example of acute and chronic.
You can see that the vein is much larger than the artery.
It is distended, it does not compress,
and there is some hypoechoic material
within the vessel lumen.
But in addition, the vein walls are thickened
limiting compression somewhat and are echogenic.
So this is a patient with chronic changes from prior
thrombosis who also acutely thrombosis.
I mentioned before that in normal a normal criteria
for vein has is an anti coic lumen,
but in this case, there are echoes within this vein,
simulating the presence of thrombus on the compression view,
you can see that there, the vein walls completely coac,
which excludes the diagnosis of thrombosis.
This increased e echogenicity is related to low formation
and again, can be seen with slow flow.

Limitations of the Examination

And lastly, just wanna point out some
limitations to the examination.
Patients with open wounds may sometimes,
not be open
to you compressing their leg,
and obviously we don't like to do that
when they have dressings.
We may remove dressings,
but there are a few complicated surgical dressings
that we need to leave alone
and we can may sometimes not be able to evaluate vessels
that are deep to these dressings.
Larger patients are obviously difficult to examine
and can also be difficult to examine,
due to either their size or due to severe edema.
It may necessitate switching
to a lower frequency transducer.
If there's calcification in the adjacent artery
for atherosclerotic disease, it may limit compression
of the adjacent vein.
And again, patients who are recently postoperative,
may not be positioned properly for the examination.
And we may sometimes have to rely on the color
and spectral doppler to aid in the diagnosis
of deep venous thrombosis.