Lower Extremity Venous Protocols and Interpretation - SD

Introduction

Hi, my name is Sandra Allison.
I'm coming from Georgetown University Hospital in Washington DC and today's lecture will be about lower extremity venous protocols and interpretation.

Summary of the Talk

I'm gonna start with a summary of this talk.
First, you wanna follow protocol when doing this examination and pay careful attention to technique.
The second part is about interpretation and I wanna point out that the phrase chronic thrombus is something that we don't want to use.
We might wanna say chronic changes or sequelae of prior thrombosis.
And the third is important to know certain pitfalls that you may face in order to avoid making a misdiagnosis.

Deep Venous Thrombosis Overview

A little bit about deep venous thrombosis.
It affects over 2 million individuals in the United States each year, and diagnosis is critical because acute pulmonary embolism occurs in up to 50% of cases of unre DVT.
It's also associated with a mortality rate of 30%.
Deep ven thrombosis is the most common reason to order lower extremity duplex sonography.
80% of emboli to lungs arise from leg thrombus.
And not only that, in those that may or may not have pulmonary embolism, it can lead to post-thrombotic syndrome and venous insufficiency.

Risk Factors

Now here's a list of the risk factors.
The top three that I wanted to point to are trauma, surgery and malignancy.
Because protocols or practices may vary in this population.

Clinical Presentation

Patients with deep venous thrombosis may present with pain and swelling in the calf.
This pain may increase with ambulation and be relieved with rest.
Patients also experience warmth, tenderness, and redness in the calf or in the area that is affected with ileal femoral DVT patients may experience buttock or groin pain, and this may extend to the medial thigh.
They may also present with proximal leg swelling.
Also important to note that in many cases patients may be asymptomatic.

Indications for Lower Extremity Examination

What are the indications for lower extremity examination while patients with suspected pulmonary embolism, those experiencing leg pain, swelling, or erythema, the presence of a palpable cord, patients may have a lower extremity Doppler exam after treatment, pre and postoperative patients may also get the study as well as high risk patients with predisposing factors.

Examination Protocol

As I indicated in the prior slide, our protocol includes evaluation of the common femoral vein, femoral vein, and popal vein, certain portions of the saphenofemoral junction and central portions of the deep femoral vein.
We also include the caffeines in our examination.
Anything that is abnormal should be documented as well as ancillary findings.
And we do the examination in gray scale.
And with doppler imaging.
We don't normally image the anterior tibial veins unless the patient is symptomatic in this area.
Augmentation is optional and can be used to answer questions or when the examination is unclear and the gastro anemia.
And so veins may also be evaluated if those areas are symptomatic.

Patient Positioning

Now it's important to position your patient properly and there are several ways to do this.
The way we prefer is to have the patient lying at an incline to allow pooling of blood to the legs and have the leg in the frog leg position.
This will allow you to do the femoral popliteal venous system and then do the calf scan at the same time.

Calf Vein Examination

Now, when doing the calf scan, we like to start from the foot and progress centrally.
And having your hand in this position will allow you to augment with your pinky while doing the examination, especially when you have trouble finding the veins.
This also allows you to angle the probe in order to look at the posterior tibial and peroneal veins without repositioning the patient.
When that doesn't work or when you cannot image deeper structures, you may try a lateral approach.
And here you see the patient now lying on their side and you can access the perineal veins and bring them closer to the transducer.

Challenges in Imaging the Femoral Vein

Now one other thing to point out is the femoral vein as it traverses the adductor canal.
Here we have a diagram from the atlas of human anatomy and you can see that the femoral artery and vein dive down and go in the adductor canal and deep to muscle.
And this may limit your ability to compress this vein during the examination.
And one way to overcome that is to bring your hand underneath the thigh and compress from both sides.
And as you can see on this ultrasound image of the femoral veins, the veins are deeper and beneath the muscle, making it difficult to compress from above.

Compression Technique

Now, compression is the most important part of the examination.
We do the compression in the transverse plane in gray scale, and we compress the venous structures every two to three centimeters.
We look at the common femoral, femoral and popliteal veins.
We designate the femoral vein as central, mid and peripheral with central being closest to the heart and peripheral being farthest away.
We document areas that do not compress.
And again, as mentioned earlier, it may be useful to use two hands when compressing the vein in the region of the adductor canal.

Doppler Imaging

Doppler can be used to confirm the presence or absence of flow.
We can use both color and spectral doppler and we can also use it to document the most proximal extent of thrombus.
And here we see a color Doppler image with color filling the vein and showing that there is nothing that's preventing the color flow or implying that there's thrombus.
Spectral. Doppler can also be used to confirm flow or confirm the absence of thrombus.
Is important to note that there may be some respiratory and cardiac variation within the waveform that is obtained.
And this can vary from patient to patient.
We do not include augmentation as a standard part or examination, but we can turn to it when we want to clarify a question.
Augmentation can be performed by externally compressing or squeezing the calf, or we can have the patient dorsiflex or plant or flex their foot.
When this is performed, we may see flow extenuation in the vessel, which indicates patent venous return and indicates that there's likely no significant obstruction to venous flow.

Interpretation

Criteria for a Normal Vein or Normal Study

Okay, moving on to interpretation.
These are the criteria for a normal vein or normal study.
The vein is normally larger than the adjacent artery and it has an ovoid shape.
The size may vary with respiration.
The vein lumen should be an coic, and the vein should have a thin wall.
You may see slight dilatation where there are valves.
And the most important part of the study, the vein should be easily compressed to exclude the presence of thrombus Starting from the foot or from peripherally.

Normal Imaging Findings

We can see here's an image of the posterior tibial veins.
The veins are paired with the artery in between, and we take images in transverse with compression.
And in long axis with color, the peroneal veins are also paired with a single artery.
When imaging the femoral popliteal venous system, we see the common femoral vein side by side with the artery.
Note that the vein is thin walled and is larger and than the artery with an ovoid shape.
The femoral vein typically lies below the artery, and then the popliteal vein, depending on where you scan it, may look like it's above the artery or superficial to the artery.
And here we see that the vein, again is larger than the artery with a thin wall and koic lumen.
You may sometimes see the valves as thin mobile linear structures that project from the venous walls.
And you may watch the vein, the valves open and close, and sometimes you may see a focal dilatation in the vein where there are valves and you may see increased echoes due to the slow flow of blood behind the valves.

Normal Spectral Doppler Findings

Now with spectral doppler, you should see spontaneous or continuous flow at all times.
You may see go to baseline due to respiratory ity with inspiration, having decreased flow and expiration having increased flow, Val salva and augmentation can be performed to see increased flow during these maneuvers and Suggest the absence of thrombus.
And again, flow should be unidirectional as with bidirectional flow, that may suggest venous incompetence or insufficiency.

Abnormal Findings: Non-Compressibility and Thrombus

Now, when interpreting abnormal studies, we see non compressibility of the vein implying that there is something within the lumen.
In this case, thrombus, the vein size may be increased and much larger than the artery than expected.
And again, with thrombus, you may see intraluminal echoes or bright or bright material or heterogeneous material within the vein.
And acute thrombus may be deformable, or when you compress it, it can decrease in size.
Now, sometimes the echoes are not easy to see, and this is why compressibility is the important part of the study.
These is an image from the right common from a vein.
This was taken before compression.
We see a little bit of echoes here, but nothing in here.
But with compression, you see that we cannot completely coap the vein walls because there is thrombus within its lumen.
Here is a video of that same patient, and you can see that with compression.
You can see the thrombus a little bit more easily.
Thrombus can fill the vein and can expand the vein.
And you can see here that this vein is filled with thrombus, but is also much larger than the adjacent artery.
You may see echoes within the lumen, and you've seen from the prior pictures that the echoes may vary.
You may see more echogenic material or less echogenic material, and it sometimes may look anti coic depending on the settings in your machine.
Acute thrombus tends to be deformable.
So you can see in this picture we have the pre compression image and the post compression image, and you can see that the thrombus within the lumen is deformable.
And then we have this thing called free floating thrombus, which isn't exactly completely free floating, but very loosely attached to the vein walls.
And you can see the thrombus projecting within the lumen.
And you can see that it appears to be free floating or moving within the vein lumen on this cene clip of the common femoral vein with color doppler, it seems again to be unattached because you see color projecting around the thrombus.
But again, this thrombus is loosely attached to the vein wall.

Abnormal Doppler Findings

Now with a doppler examination, the presence of thrombus may present with either absent color or filling defects within the vessel lumen.
On spectral doppler, you may see loss of ity or absence of respiratory or cardiac pulsatility.

Evolution of Thrombus Over Time

Okay, now what does thrombus do over time?
Well, it may completely resolve.
It may retract or recanalize.
It may appear more irregular over time.
Over time, the vein may become scarred and you may have remnants of the thrombus with syne or scarring.
There may be wall thickening which may prevent compression and present as a pitfall to your evaluation of the vein.
The res, the thrombus may calcify, and again cause wall thickening, wall thickening may result in a narrowed vein.
Thrombus in the region of valves can damage the valves and also present with syn ga or the vein may become permanently occluded with collateral vessels in this area.
I have some images to show this.
Over time, thrombus can appear irregular, it can increase in echogenicity, may not as the thrombus is resolving.
It may leave behind a web or a sneakier, and these may sometimes be attached to scarred valves and cause incompetence of the valves.
Over time, the thrombus may calcify and not completely resolve.
With recanalization, you can see that the lumen is established centrally with the thrombus adherent to or or lining the walls of the veins.
Here over here you see there's thrombus lining the venous wall with patency established centrally.
And again, over time, the vein may become scarred and may have a thickened wall.
Now notice here the vein is no longer, much bigger than the artery, but also the wall thickening is preventing compression or complete tation of the wall.
The vein may become narrowed due to scarring over time, it may remain patent, but I wanna point out again that it is smaller than the adjacent artery.
It may become narrowed and chronically occluded, and at times you may not even see the vein.
So the clue here is that we have the artery but not the adjacent vein.
In this picture, Sometimes You can see the vein, but it is chronically occluded and with no flow within that vein, sometimes the only clue to a prior thrombotic event is the presence of collateral vessels.
These vessels do not have the same appearance as the native vein.
They may be more tortuous.
They may not sit adjacent to the artery where you expect the native vein.
The native vein may not even be seen.

Pitfalls in Diagnosis

Now some pitfalls to face when you're evaluating a patient for DVT, you may have a patient that cannot be scanned optimally, either due to their body size or due to edema in their leg, or maybe the presence of bandages.
These may limit your ability to compress the vein mistaken identity.
If you're looking at the collateral vessel and not the native vein, you may mistake it for a patent native vein and miss the thrombus.
Duplicated veins may also be confusing.
Thrombus age cannot be assessed based on its echogenicity.
Slow flow may not be detected on color. Doppler and compression may be your only clue to the absence of intraluminal thrombus recurrent DVT may be difficult to age and may be difficult for you to tell the difference between acute or chronic chronic changes in the vessel.
Improper use of color or settings in your machine may lead you to believe that there is no flow within the vessel, and reduced flow within the vessel may not be detected with color doppler.

Misconceptions About Collateral Vessels

Now, one misconception is that collateral vessels occur over time and that if you have collaterals, this is a chronic situation, collateral vessels may open up acutely in this patient.
You see there is distension of the vein.
We don't see the thrombus that well, but there are collateral vessels in this area, and this is a patient with acute thrombosis, not chronic situation.

Duplicated Veins and Missed Thrombus

Now, sometimes the presence of a duplicated vein may not clue you into the presence of a thrombus.
So in this case, we have a patient with a duplicated vein.
But in this study, because the vein compressed, it was read as a negative DVT and the fact that the duplicated vein was thrombosis was missed.
On the following exam, you can see that there were two femoral veins with both of 'em.
Now Being without thrombus, one clue perhaps to use is the vein here is smaller than the accompanying artery.
And when you see this, you might wanna look for a second vein in a duplicated system.
The other possibility for the vein being smaller as mentioned earlier, is a chronically scarred vein.
But in any event, if you see that the vein is smaller than the adjacent artery, be careful to look for the duplicated vein and not miss that that vein is filled with thrombus.

Avoiding the Phrase "Chronic Thrombus"

Now, as I mentioned earlier, chronic thrombus is not a phrase that we'd like to use because that implies the presence of something, a situation that is treatable.
But in this case, this is a syne or a scar or a web, and it is a chronic sequelae or a chronic change related to prior thrombosis.
And therefore the, the phrase chronic change or scarring may be more appropriate and not lead to overtreatment of the patient.

Slow Flow Mimicking Thrombus

Now, slow flow may present as a luminal filling defect or echogenic or echoes within the VA vein lumen and may be mistaken for a thrombus.
But in this case, you can see that the, the vein easily compresses and the vein walls completely coapt and that this echogenic material is slow flowing blood.

Acute Thrombus in Chronic Changes

Now, patients may present with acute thrombus in the setting of chronic changes.
In this case, the vein walls are thickened due to a prior thrombotic event, but it is much larger than the adjacent artery and ha and is unable to be compressed to the presence of acute thrombus lower in the leg.
Again, you can see that this vein is not as large as as you expect it to be because of chronic scarring, but there is acute thrombus within the lumen.

Low Gain and Echogenicity Issues

Two little gain may imply the presence of mural or re canalizing thrombus.
So it is important to optimize the gain and fill the vessel lumen.
Now, in some patients it may be difficult to adequately visualize compression of the vein.
Sometimes you can use color to localize the vein or identify the vein and then do compression in gray scale once you find the vein.
Now, as mentioned earlier, echogenicity is not a reliable sign of, thrombus age and acute thrombus may also appear echogenic.
You can see that this vein is filled with echogenic material.
The vein is enlarged much larger than the adjacent artery.
And then you can see that we are unable to coapt the vein walls due to this thrombus, but also that the thrombus is deformable, which is a characteristic of acute thrombus.

Limitations in Examination

Some limitations you may face patients with open wounds cannot be compressed in that area.
Dressings may also limit your ability to compress, especially in patients who have read recent surgery.
Patients who are large or who have enlarged legs due to severe edema may not be able to be compressed adequately.
Calcification in the artery may limit your ability to compress, and patients who have recent surgery or in pain may not be positioned adequately for the examination.

Conclusion

So in conclusion, when performing these examinations, it's important to follow protocols as to not miss important findings.
It's important to pay attention to technique so as to not, have false positive examinations or for false negative examinations.
Also, it's not desirable to use the phrase chronic thrombus and imply that you have a treatable situation.
Perhaps use the phrase chronic changes or scarring or sequelae of prior thrombosis when reading these examinations or interpreting the examinations.
And last to be aware of pitfalls so as not to make a false diagnosis.
Thank you for your attention and for watching this video.
I hope that you find it useful.