Lower Extremity Venous Evaluation - SD

Introduction

Hi, my name is George Bjo, and I'm director of Vascular Ultrasound Services for Vascular Surgical Associates at White Plains Hospital in New York.

Today I'll be discussing the use of duplex ultrasound for evaluation of the lower extremity veins for detecting the presence of deep vein thrombosis.

Today I will be discussing the use of duplex ultrasound for evaluation of patients with suspected lower extremity deep vein thrombosis.

Venous Thromboembolism Overview

Venous thromboembolism is a huge problem in the United States today.

There are approximately 2 million cases of deep vein thrombosis reported each year.

The post thrombotic syndrome, of course, is a long-term complication of deep vein thrombosis with approximately 800,000 cases of post-thrombotic syndrome reported each year.

Pulmonary embolus is noted to occur in about 600,000 patients every year with about 60,000 deaths related to pulmonary embolus.

It is thought that at least one of the three of Virchow's triad is associated with each and every incidence of deep vein thrombosis.

Stasis, a vessel wall injury and hypercoagulability, in some manifestation, will be a part of the process.

Signs and Symptoms of Deep Vein Thrombosis

The signs and symptoms of deep vein thrombosis can vary, however, typically patients present with swelling, pain, tenderness, or redness somewhere along the length of the lower extremity, but particularly at least in my experience in the calf.

The swelling that I refer to as different than the mild ankle swelling that one might experience in patients with congestive heart failure.

Typically the swelling associated with swelling below the knee, just below the knee, deep vein thrombosis usually affects only one leg.

And it's thought that the pain may be made worse by bending the foot upwards towards the knee, the so-called Homan's sign.

However, in my experience, I have found the Homan's sign to be quite weak in terms of diagnosing the presence of deep vein thrombosis.

Pre-Examination Preparation

I think it's critically important for the sonographer, the vascular technologist, to review the request form prior to starting the evaluation.

There should be a critical review with assessment of risk factors, and a questioning of the patient in terms of the symptoms, and also review of the lower extremity for findings.

This will help you to triage your patients appropriately, but I think more importantly, it allows you to suggest alternate or additional tests if they're necessary based on presenting signs, symptoms, and risk factors.

History and Physical Examination

In terms of the history and the physical examination, again, elicit information regarding the patient's symptoms.

Questions related to duration of pain, obviously which extremity and whether or not there's a history of deep vein thrombosis.

A visual inspection of the legs is in order.

A measurement of the calf circumference often will be quite coincident with the presence of deep vein thrombosis with the appropriate risk factors.

Always ask about recent procedures and other comorbid conditions.

I think it's also critically important to question the patient about specific areas of pain within the lower extremity that really should be evaluated, those segments that might fall outside of the typical protocol.

Examination Setup and Positioning

In terms of ruling out DVT, a warm room I think is appropriate, in that it allows the vessels to vasodilate and allows us to see the veins much more readily.

We test our patients in the supine position, with the patient in reverse Trendelenburg, and that is with the head higher than the feet, with the knee slightly bent, and the leg externally rotated.

And this gives us access to all of the vessels of interest from the level of the groin all the way down to the ankle.

Exam Protocol

The exam protocol is straightforward.

We're examining all of the major vessels from the level of the groin, routinely down to the ankle.

We will be performing compression maneuvers with the transducer in the transverse orientation, every one to two centimeters along the length of those vessels.

And in the process, we will be assessing the vessel for its diameter and also assessing for the presence of intraluminal echoes, which might suggest the presence of deep vein thrombosis.

When a deep vein thrombosis is suspected, we examine and confirm all suspected abnormal findings with the transducer oriented to the long axis of the vessel.

We also will Doppler for flow at the common femoral and popliteal veins, and then again, always go back to examine any specific areas of pain and or tenderness.

Criteria for Positive Diagnosis

The criteria for a positive diagnosis are three, first in compressibility of a venous segment, visualization of thrombus within the lumen of the vessel that's being evaluated, as well as the inability to elicit flow, either by color or by spectral Doppler.

Compression Maneuver Description

In this cartoon here on the right, we see an artery and a vein and the transducer, and we push down manually.

And the idea is to see that the walls coapt.

If the vessel walls do touch, then we can feel fairly confident that that area of the vein is free of intraluminal thrombus, sonographically.

Here is the vein and the artery, and in the image to the right, what we're doing is we're pushing down.

As you can see, the vein disappears, however the artery is visible in this patient.

This is diagnostic of a negative examination at that level to the right.

As we're pushing down, we see that the vessel walls do not touch.

This is the common femoral vein in the common femoral artery.

The vessel walls do not touch.

We see evidence of color flow within the lumen of the artery.

However, there is an absence of flow within the lumen of the vein, and we can see evidence, B-mode evidence of thrombotic material within the lumen of that vessel.

The combination of those three factors gives us a high level of confidence for a positive diagnosis.

This patient is positive for deep vein thrombosis at that level.

Color Flow Usage

In general, I do not use color flow for the lower extremity vein examination.

Case Study: Postpartum Patient

And in this quick case study, we have a 23-year-old female who's postpartum five days, who presents with some severe shortness of breath.

The suspicion was the pulmonary embolus and the venous duplex was ordered.

As you can see in the color flow image to the right, we have a very normal appearance for the common femoral vein.

However, when we remove the color, you can see that there's a significant size thrombus at the level of the common femoral vein.

And if we had not taken off the color, this could have been missed, and this could have been tragic for the patient.

I would recommend that you not use color at all, in fact, for the lower extremity vein evaluation, except if you have to confirm the presence of flow in a vessel where you couldn't compress it or a patient couldn't tolerate a compression.

But mostly those are for confirmatory issues just to confirm either the absence of flow or the presence of flow where you could not use one of the other parameters.

Otherwise I really don't use color.

Also, I compress only in the transverse orientation, and do most of my evaluation in the transverse orientation.

Duplicated Veins and Thrombus Detection

Here we have a very nice image of a duplicated popliteal vein with a normal, again, color flow appearance.

However, what we don't see is in this plane, a third vessel where there is a tail of thrombus extending into the popliteal vein.

And again, if you had not evaluated this patient in another plane, this would've been missed.

However, if you were evaluating this patient transversely, which is what our protocol calls for, it's almost impossible to miss presence of a thrombus.

You can see here we have posterior tibial artery and multiple veins, none of which would be missed if they were thrombosis.

Here, peroneal artery with accompanying veins here is a popliteal artery and vein.

In this case, there is no duplication, but you can see multiple small collateral vessels in the area of the popliteal vein.

The transverse orientation allows us to visualize and detect the presence of thrombus, regardless of the plane that we're looking in.

Zones of Evaluation

What how we practice in terms of the venous ultrasound evaluation in our facility is that we break down the leg into zones of evaluation.

The first zone being the examination of the external iliac and common femoral veins, distal to that, we look at the femoral deep femoral origin, great saphenous in popliteal veins, and that's zone two.

And then zone three would be evaluation of the tibial veins in the leg to start the examination.

Zone One: External Iliac and Common Femoral Veins

In zone one, what we do is we place the transducer at the level of the groin and identify the saphenofemoral junction.

You can see that in the image on the bottom here.

Here is the common femoral vein.

This is the superficial femoral artery and the deep femoral artery.

And here you see the great saphenous vein.

Once this image has been identified, we can then take the transducer and move it proximally to the level of the inguinal ligament, where you will identify the distal external iliac vein as it dives deeply into the pelvis.

At this point, I would begin my compression maneuvers while slowly moving the transducer to the bifurcation of the common femoral vein.

Once I've completed evaluation of the common femoral vein in terms of its my ability to compress the vessels, I would then turn the transducer to the long axis to assess the common femoral vein for flow dynamics.

And this is a part of the examination that should be done bilaterally.

And what I would do is evaluate the ipsilateral side for flow dynamics, and then immediately go over to the contralateral side to evaluate it as well.

Not leaving any significant amount of time in between evaluation of the flow dynamics to give the patient a opportunity to change positions or change other parameters that might affect the flow dynamics and comparison of one side to the other.

Flow Dynamics Assessment

Now, flow in the lower extremity is characterized primarily at the level of the common femoral vein, according to its phasicity flow, at the level of the common femoral vein should wax and wane with respiration, with deep breaths, the flow should cease and with resuming of normal breathing, the flow should resume flow at the level of the common femoral vein should also be spontaneous, and that is that you should not have to perform any provocative maneuvers to elicit flow at that level.

If you're having to do that, especially when it's a unilateral issue, you need to be clued to the potential for an issue.

Augmentation is something that we look for occasionally, and augmentation is an increase in flow with distal compression.

That can sometimes be helpful if there are segments in between where you're compressing and where your transducer is that are not visualized for whatever reason, whether it be overlying dressings or perhaps you can't compress it because the patient can't tolerate a compression.

You can sometimes document patency by doing an augmentation maneuver.

And then we always have the patient Valsalva.

And again, with the Valsalva maneuver, the flow should cease.

And again, with normal breathing, the flow should resume, in lieu of doing a Valsalva.

If your patient cannot perform the Valsalva maneuver, you can always do a proximal manual compression at the level of the belly and then observe what's happening at the level of the common femoral vein.

Here we are seeing a normal phasic venous flow pattern at the level of the femoral vein.

Here you can see normal flow moving toward the transducer in this image.

And then with a deep breath, the flow ceases, and then there's a transient reversal of flow.

And then again, with normal breathing, the flow resumes on up to the heart.

This is a normal response to a Valsalva maneuver.

Keep in mind, in terms of your Doppler examination, that it can be affected by the patient's position, and this is the reason why we do one side and then immediately go over to the contralateral side to do our comparison.

Spontaneous flow that we see in the common femoral vein may not at all be present at the level of the tibial vein, so don't look for that.

And we don't variation of flow or the phasicity that I described may not be present in shallow breathers, because the changes in the pressure don't allow for the changes in for the phasicity that you might be looking for.

The bottom line when doing evaluation of the waveform right versus left is to look for asymmetric changes.

So it, a waveform like this that you see on the left, a contralateral to the normal wave form that we see here on the right, should clue you into the possibility that there are issues going on above the level of your transducer.

Zone Two: Femoral Vein and Related Structures

Once we've completed the evaluation of the common femoral vein, we then would move into zone two, which calls for evaluation of the great saphenous vein in the proximal thigh, the origin of the deep femoral vein and the femoral vein itself in the thigh to the level of the adductor canal.

One of the things to be aware of is that the femoral vein may be difficult to compress because of overlying bony structures, and as well as because of the depth of that vessel as it starts to dive deeply in the distal thigh.

One of the things that we you can't do to help is keeping in mind that because the vessel is taking a deep dive here, the orientation of the transducer is no longer a perpendicular to the course of the vessel.

So taking that transducer and pointing cephalad so you can have a good perpendicular incidence, will allow for a better compression.

The other thing you can do is you can use some hand pressure from the posterior distal thigh while pointing that transducer cephalad, and it'll make the compression much easier for you and for your patient.

The great saphenous vein itself is evaluated for about the first 10 centimeters beyond the saphenofemoral junction, and then distally is needed.

One of the things we know about the great saphenous vein is that when it does become thrombosed, the patients tend to be very symptomatic.

We will routinely look at the great saphenous vein that its origin.

You don't wanna miss a thrombus like you see here in this image, because of the proximity to the deep system.

If this propagates into the deep system, this can result in a significant pulmonary embolus.

However, superficial thrombophlebitis really is an inflammatory condition, which presents with local tenderness, usually lots of pain and a palpable venous cord.

In the absence of those symptoms, we will not look at the distal great saphenous vein, because there is a low yield for positive findings without symptoms.

We will routinely, however, look at the origin of the deep femoral vein, and this is a vessel that is sometimes ignored and really shouldn't be because, although it's not common, you can get patients who present with thrombus at the orifice of the deep femoral vein, approximately, and again, because of the proximity to the common femoral vein and embolus from this area, can result in a significant pulmonary embolus.

So you really don't wanna miss that.

Always take a look at the origin of the deep femoral vein.

When it's needed, you can do calf augmentation again to augment flow past your transducer at the level of the femoral vein.

This does not need to be part of the routine protocol.

However, again, if you have a suspicion of thrombus in places that you can't see occasionally, an augmentation can be useful to document patency.

However, this does not exclude the presence of a partial thrombus, so be careful in terms of your distal augmentation zone two.

We continue on to the level of the popliteal vein, and we use an overlapping technique to evaluate the popliteal vein.

We'll evaluate it in the distal thigh from a medial approach, and then take the transducer and position it behind the knee, and then work our way back, so that we're overlapping areas from both the medial and a posterior approach, making sure that we're not missing any area of the popliteal vein.

We would then work your way distally into the proximal calf, assessing the popliteal vein through the bifurcation, where it becomes the posterior tibial and the peroneal veins.

And again, we're using the overlapping technique.

We're using both a posterior approach following the popliteal vein from the back of the leg posteriorly, and then placing the transducer on the medial calf proximally, to follow the tibial and peroneal veins approximately to their origin, to their confluence, where they form the popliteal vein.

Popliteal Vein Examples

Here's an example of a patient who comes in and we see here a patent popliteal artery, but with occlusion of the popliteal vein.

One other very important thing is, you really should examine the popliteal fossa for vascular as well as nonvascular masses.

This is an area that's quite productive for these kinds of issues.

Here's an example of a patient who presented with a little bit of calf pain, where the popliteal vein was patent, but in fact, this patient had an occluded gastrocnemius vein.

Here we see the paired gastrocs.

Here's one vessel, this is the other.

Here's the accompanying artery.

And again, this these are important vessels to evaluate.

Here we see three sets of gastrocs, and you can see the proximity to the popliteal vein, if there's enough of a burden of a thrombus burden.

And if you get propagation, these can't propagate into the popliteal vein, and then up further into the deep system and put the patient at significant risk for a pulmonary embolus.

So you don't wanna miss the potential for gastrocnemius vein thrombus.

Differential Diagnoses in the Popliteal Fossa

And there are other differential diagnoses.

Again, the popliteal fossa is quite productive for other issues that may be the cause of the patient's symptoms.

These patients will come in with a referral for a rule out deep vein thrombosis for various signs and symptoms.

Many of them are negative, but they can have other issues that are relevant to those symptoms.

As we know, the clinical signs and symptoms for DVT are nonspecific, and in up to 10% of patients, there will be other causes that can be found with ultrasounds.

So always examine the patient where the patient says that it's hurt, including soft tissues, as well as arteries and veins.

Baker cysts are not at all uncommon in the popliteal fossa, and in fact can be found in 3% of all your DVT studies, often presenting as a cystic area medial in the popliteal fossa itself.

You need to look for a connection to the joint space between the semimembranosus tendon and the medial head of the gastrocnemius muscle.

Occasionally, patients can present with ruptured Baker cysts, and these will often present as tear shaped structures.

They can be irregular, often resulting in edema, and have a complex appearance on the ultrasound image.

Here, just a few examples, a couple of examples of a Baker cyst.

You can see here an encapsulated fluid fill structure that's communicating with the joint space.

And this is a typical appearance of a Baker cyst.

One of the vascular issues related to the popliteal fossa, but not with the venous system, is a popliteal artery aneurysm.

And patients can present either with patent or thrombosed popliteal artery aneurysms.

These tend to be asymptomatic, I'm sorry, they're usually symptomatic due to distal embolic events, but often they are asymptomatic.

A rupture of a popliteal artery aneurysm really is uncommon.

The biggest issues with popliteal artery aneurysms, again, are distal emboli, and the risk of compression of adjacent neurovascular structure, such as the popliteal vein, popliteal artery aneurysm will be found bilaterally in up to 78% of cases.

And by the way, if you do find the popliteal artery aneurysm, probably you should be looking at the abdominal aorta to rule out an aneurysm as well, is there's a up to a 40% incidence of AAA when a patient has a popliteal artery aneurysm.

Here's an example of a long axis view of a popliteal artery aneurysm.

Here we see the distal popliteal artery itself, and you can see here the focal dilatation.

This is a transverse view of a popliteal artery aneurysm, and you can see the lumen here and the adjacent vein itself.

And here a color flow image showing the reduced lumen, lots of thrombus here in this popliteal artery aneurysm.

Again, putting this patient at risk for an embolic issue, potentially outside of the popliteal fossa itself, we can have other issues, other atherosclerotic etiology for leg pain, such as common femoral artery occlusion.

Here's a patient who presented with some leg pain, who in fact had acute occlusion of the arterial system up to the level of the common femoral artery.

Here you can see color flow evidence of a patent common femoral vein, but no color flow elicited within the artery that's adjacent to it.

This vessel was occluded and resulted in this patient's pain.

This can also happen at the level of the superficial femoral artery and even the popliteal artery, as again, a popliteal artery aneurysm can itself occlude.

There are some differences in terms of the presentation versus the venous occlusion.

The pain associated with arterial occlusion is usually more severe, and it's acute onset.

Patients can often tell you exactly when those vessels went down.

These patients will present with decreased pulses and often a cold foot.

But occasionally this can be subacute.

The issue is usually an embolic issue when these patients present acutely.

There are other differential diagnoses you need to look for, such as hematomas, muscle tears, the presence of infection, abscess formation, and even muscle mass.

Sometimes patients present with cellulitis as a differential diagnosis for the cause of their pain, but as you can see, when you take a look at these images, some of them are very similar to others.

Often you can't tell by the duplex ultrasound what entity you're dealing with.

So I would give a differential diagnosis and always say that additional imaging is suggested or recommended if it's clinically indicated in that patient.

Zone Three: Calf Veins

Once we're through with the popliteal fossa, we would then take the examination on into the leg, and identify the posterior tibial and peroneal veins.

And this probably will be the most time consuming part of the examination.

It does take some practice and a little bit of clinical skill and experience.

But if you do it enough, you probably can do it well.

I usually will locate the calf veins in the midcalf, and there are several ways you can do that.

You can identify the tibia and the muscle from a medial approach, and just really drop the transducer right into that groove in the long axis, such as you see here.

That often will produce an image like you see here on the bottom.

If you're lucky, you can get the peroneal artery, posterior tibial artery, and the accompanying veins.

Often you'll have to rock back and forth to see these vessels as the they may not be in the same plane.

You can also use bony landmarks as well as adjacent arteries, scanning these patients transversely.

We use the same overlapping technique that I described proximally following the patients from the knee down from a posterior approach, and then working from the mid-calf up to the confluence of the vessels and the forming of the popliteal vein.

We do not scan anterior tibial veins routinely, as they're rarely part of the thrombotic process as an isolated event.

However, again, if the patient is symptomatic in the distribution of the anterior tibial veins, and perhaps they've had trauma there or some good reason for a thrombotic event, you really should look in that area.

Here is a transverse view of the posterior tibial veins here and the peroneal veins.

You'll see the great saphenous vein in the near field.

And you can, again, see multiple veins accompanying one artery here, a paired set of peroneal veins around the peroneal artery.

If you look at this cross-sectional image, and keeping in mind that when we scan, we scan from a medial approach, usually when we're in the calf.

Here is your line of sight.

These are the posterior tibial veins and the artery.

These are the peroneal veins in the artery.

Here are the bony landmarks. Here's the tibia.

This is the fibula.

This is what you would see from this projection.

You can get an idea here of the tibia.

Here is the fibula in this image.

Here, we identify the posterior tibial artery, and it's accompanying veins, the peroneal artery, and it's accompanying veins.

So again, you can use the bony structures to identify the vessel of interest in the leg.

Conclusion and Resources

For more information regarding the use of duplex ultrasound for the evaluation of deep vein thrombosis, I would refer you to the SVU website.

That's SVU.net.org, where you can find SVU's professional performance guidelines and position papers relevant to the evaluation of lower extremity deep vein thrombosis using duplex ultrasound.

Thank you very much and happy scanning.