Pitfalls and Challenges in Doppler Ultrasound - HD

Introduction

Hi, my name is Mindy Horo.
I'm a radiologist at the Einstein Medical Center in Philadelphia and the Director of Body Imaging and I oversee ultrasound, the vascular lab and ct.
Today I'm going to speak to you about pitfalls and challenges in Doppler ultrasound.
This is obviously not a fully comprehensive talk on a subject, but will be based on my clinical practice, which oversees most types of ultrasound.
Today is my pleasure to speak to you about pitfalls and challenges in Doppler ultrasound around the body.
I have no disclosures.

Outline

The outline of this has to do with broad general categories rather than specific areas of the body, but the examples will come from across the body.
These are the topics that we will be covering is a waveform, arterial or venous, and how can you tell what happens when something is in the incorrect direction of flow and what does it mean?
How can one use subtle changes in waveform to infer either proximal or distal disease that is outside of your viewing area?
We'll talk about some color doppler pitfalls.
Then we'll look at examples where you can find significant stenosis in a vessel without traditionally elevated velocities and vice versa, high velocities without significant stenosis.
We'll briefly touch upon various types of echoes in moving blood and then a few miscellaneous topics.

Determining Arterial vs. Venous Waveforms

The first thing is, is a waveform arterial or venous.
And this has to do with the overall puls fity.
So here we have a waveform from a hepatic vessel.
It's quite pulsatile, and you could ask, is this arterial or venous?
Most of you probably have already guessed.
This is a normal hepatic vein and hepatic veins being close to the heart have, waveforms that reflect the open enclosure of valves and the blood passing through the heart, as you can see in the A waves, s waves and D waves.
So this is a normal Doppler ultrasound of a hepatic vein.
What happens, in, in this situation, is that with the cardiac cycle, when you're close to the heart, be it on the abdominal side or the chest side, you will see reflected back the pulsations of the heart.
This can be associated or not with varying degrees of respiration and can be exaggerated with a variety of maneuvers.
So for instance, this is a patient with normal hepatic veins and these are progression of images from the middle hepatic vein with the patient at end expiration or Valsalva maneuver.
The normal ity is completely blunted and flattened with quiet respiration, we see some of the return of the normal ity and suspended end re inspiration fairly normal pulsatility.
So this patient is completely normal and it all depends on how you take your images at what stage of the respiratory cycle.
On the other hand, there are a variety of patterns that you can see in the hepatic veins, which are quite abnormal.
Increased pulsatility can occur in patients with congestive heart failure, tricuspid insufficiency, or incompetent valves in more proximal veins.
Decreased puls fity occurs when there is peripheral vasodilatation, more proximal venous occlusion or a stiff liver, for instance, in cirrhosis affecting the hepatic veins.
So here's a patient with leg swelling, orthopnea, and dyspnea, and these are images from the common femoral vein.
By the time you get to the common femoral vein, usually there's just normal respiratory variability and no pulsatility, but here we see puls fity akin and if not more accentuated than in the normal liver.
This is secondary to heart failure.
Now back in the liver, here's a doppler of a hepatic vessel at the porta hetus, and we're getting a very pulsatile waveform.
Is this arterial or venous?
And you can see in the image that it looks like it should be the portal vein, which normally does not have this kind of pulsatility.
This is an abnormal pattern for the portal vein, which normally shows sort of a flat wave form with some respiratory variability and a velocity, angle corrected velocity range of 20 to 33 cent, centimeters per second.
If this becomes more pulsatile or reversed, it is typically due to cardiac disease.
Low, levels of velocity are usually a reflection of portal hypertension.
So here's the same patient again, and now we're looking at the hepatic veins, which as you recall are normally pulsatile, but here we have a very accentuated saw tooth pattern of increased pulsatility.
And when you look in color, you get flashes from blue to red and blue to red in these distended veins.
This is the same patient's chest radiograph and you can see multi chamber cardiac enlargement and enlarged liver and ascites and multiple findings related to congestive heart failure.

Post-Renal Transplant Example

Now let's turn to this patient.
This is somebody who's two days after renal transplant and we're asked to do imaging and a variety of waveforms were obtained of the, person scanning was hoping to, obtain the waveforms of the arcuate vessels in the periphery of the kidney.
So in this image we've got a waveform, which was of cons, which was concerning for a low resistive index and a delayed upstroke and in a different place we had nice sharp upstrokes and literally no diastolic flow indicate that would give you a resistive index of one.
And, the question here is are these both, arcuate arteries?
How did we get both, these kinds of waveforms in the same kidney if these are arterial?
Well, the clue here is that on the left these are venous waveforms and this patient has very, very pulsatile venous flow, which can be checked by looking at the ipsilateral external iliac vein.
And the true arterial waveforms have normal upstrokes but no diastolic flow, indicating a resistive index of one.
Over the few days, as the patient's heart failure and fluids were normalized, the venous flow normalized as well with much less puls ity.
Here are the arterial waveforms, which started to show some diastolic flow.

Cirrhotic Liver Example

So you can see that here we are, it's an image of a patient's liver, it's a kind of echogenic liver, and this is a vessel with flow away from the transducer as you can see in the color scale.
And we get a kind of flattened wave form.
So this is, venous, but is it a hepatic or portal vein?
Well, I told you that normal hepatic veins have lots of puls fity and portal veins, are normally slightly flattened, but this would be an incorrect direction for a portal vein.
The key here is to look at the liver and try and understand what might be going on.
And though on the normal routine low, frequency imaging, this just looked like an echogenic liver and it looked fairly smooth superficially.
If you image with a high frequency transducer, the clear nodularity of this cirrhotic liver becomes much more apparent.
So dampened pulsatility in hepatic veins, as was our case, can be seen in patients with cirrhosis as well as a variety of different, clinical situations.
And when you take it in the normal respiratory phase is a clue that something is amiss in the liver.

Lower Extremity Example

Next case here, we're imaging now at the popliteal level in the lower extremities and here's a vessel.
And this is the doppler tracing of it.
It's a very kind of low velocity tracing.
The resistive index is relatively low and there's a delay in upstroke.
So is this arterial or is this venous?
Is this a lot of ity in a vein or is this low puls fity in an artery?
The clue here is to look more proximally.
This is the normal high resistance pattern that one would obtain a nice sharp upstroke, a little bit of reversal in early diastole, a return to forward flow in aphasic waveform.
And this was normal in the same side in the common femoral artery.
As we started to come down the leg, we similarly had normal waveforms at the level of the mid superficial femoral artery by the time we got to the lower aspect of the thigh.
However, in the superficial femoral artery, the artery became completely occluded.
There was absolutely no flow.
And, this is with extremely sensitive settings.
So what were we seeing when we got to the popliteal level?
Well, this is the CTA and you can see that there was a complete occlusion and the patient had reconstitution of the popliteal artery through collaterals.
When this happens, the flow is usually very low velocity and not very good ity because of significant vasso dilatation.
And this is a typical waveform when there is reconstitution of any artery through collaterals, and you can see that you could mistake it potentially for a venous waveform.
In summary, normal upper and lower extremity arterial waveform should show nice sharp phasic types of waveforms with high forward flow in, in early cyst systole, a brief diastolic reversal, and then, a small amount of forward flow.
In later diastole, this pattern will become less prominent with vasodilation normally, which can occur with exercise or warming in the upper and lower extremities.
When occlusion occurs, hopefully you'll find the actual segment that has no flow, but if for some reason that's difficult, you get a clue.
When you see the distal waveforms that look like our case, there's decreased systolic velocity, a monophasic waveform and a delay in upstroke from the peripheral vasodilatation.
If there's stenosis, you would see spectral broadening in color and in spectral doppler increasing diastolic, increasing systolic velocities.
And the typical, criteria that we use for a severe stenosis is a peak systolic velocity of at least two times the proximal segment and loss of reverse flow with the color brewery.

Tumor Thrombus in Portal Vein

Turning to another topic, this is an example of a patient.
We're looking at the portal vein here, and you can certainly see that there's something that shouldn't be there.
That's inside the portal vein.
There are some low level echoes.
When we looked with the, color flow in some areas where there were no echoes, we certainly saw flow, but in other areas within the, thrombotic material or the material in the portal vein, we also saw flow.
And when we did a doppler of it, this flow, the flow within this echogenic material was actually an arterial waveform.
So how do you get a portal vein that has arterial flow inside of it?
This patient had a tumor in the liver and the thrombus that's sitting here is tumor thrombus.
So the thrombus itself has its own intrinsic arterial flow re irrespective of the any venous flow that might be around it.
Seeing these kinds of, thrombi in the portal veins can actually be rather challenging, especially as the liver itself becomes more and more abnormal.
This patient came with a history of rising, alpha feta protein and had a multicentric hepatocellular carcinoma.
The question is where is the portal vein in the middle of all of this?
And if you look carefully as I've drift, I've drawn this, this is a very expanded portal venous anatomy system with the right and left portal veins coming together in the main portal vein filled with all kinds of material.
And when, the vessels are that expanded, the likelihood of it being tumor thrombus increases the color flow and spectral flow are very helpful.
You can see actual little vessels in the tumor thrombus, confirming that this is arter and this was arterial flow within tumor thrombus.
So, malignant portal vein thrombus usually expands the portal vein.
The, gray scale appearance may be similar to the primary tumor.
You can look for the internal vascularity and certainly ultrasound contrast is useful for the diagnosis.

Subtle Changes in Waveforms to Infer Proximal or Distal Disease

Now we'll turn to the topic of subtle changes in waveforms or asymmetry between sides, which allow you to infer more proximal or distal disease.
And this is where it's fortunate that we usually have two of everything, two arms, two legs, and we have a way of comparing.

Groin Swelling After Cardiac Catheterization

So let's look at this patient.
This patient came with swelling in the groin after cardiac catheterization, and we're looking at the groin.
We're imaging the common femoral artery proximally.
And here are the, here are the waveforms, a nice sharp up stroke, excellent velocities, but this is not the same phasic waveform that I showed you earlier.
For normal, there's no reversal of diastolic flow, and in fact there's uniform forward flow during diastole.
This is a monophasic waveform and is not normal.
We continued along the way and a little more distally and looked at the common femoral artery a few centimeters below, and here the waveform returned to a normal triassic pattern, up a little bit of reversal that you can barely see there, and then a little forward flow.
So what is the issue here?
If you fiddle with the color and the spectral, you can see that there's actually a connection between the common femoral artery and the common femoral vein.
If you doppler that connection, this fistula, you get very high velocities with extreme turbulence and this patient has an arterial venous fistula.
If you doppler the vein at this level, you'll find the arterialized venous wave form.
So an acquired arterial venous fistula results in a change from low to high resistance, and if you're close to the fistula, the flow just proximal to it in the artery will become a low resistance waveform, but just distal to it.
The vessel doesn't remember and it is, returns to the high resistance.
It's a clue that something is going on here.
You can usually find high velocity arterialized venous flow.
The turbulence and the supplying artery may have increased in size.
The color Doppler brewery is also a helpful hint.

Post-Liver Biopsy

This patient had a history of liver biopsy and came to us for doppler.
This is the hepatic artery and there's a pretty normal resistive index and a normal peak systolic velocity with a normal monophasic waveform, which is the kind of waveform that a visceral organ should have.
However, as we crept along the artery more inside the liver, the resistive index decreased.
We were getting more diastolic flow for the systolic flow that we still had a nice sharp upstroke.
We went a little bit further and the velocity went sky high.
The resistive index went down and there was a lot of turbulence.
So as we're creeping along from the artery going more and more into the liver, usually the velocity doesn't increase.
And here we got a huge increase and a lot of turbulence and a very low resistance waveform.
So again, we would suspect that there's some sort of unusual connection.
And, in this case, there was a hepatic artery to portal vein fistula that we were able to detect.
And you can see, in the right portal vein a normal venous waveform at the fistula level.
Much more pulsatile.

Lower Extremity Swelling with Thrombus

This patient came to us with lower extremity swelling for a Doppler examination, and we're looking at the common femoral vein.
Clearly the vein is somewhat expanded and there's a thrombus inside.
I'm not showing you the, compression images.
They certainly did not compress normally, however, you can see in the color and spectral that this is not an occlusive thrombus and that we had flow around it and this was what the waveform looked like in that portion that had flow.
It was a very flattened waveform, without much respiratory variability.
In all of our patients who are ordered to have a unilateral study, we do at least one, usually one image of the contralateral vein and its waveform for comparison.
And that's what happened in this situation.
This is the other side, and you can see that this vein, the on the right side, had flow in the correct direction and it had a much, a slightly more prominent ity than we were seeing on the left side.
What does this mean? It means that the thrombus that we found right here may not be the only thing going on here, and that we're going to need to look more out of the field than we would ordinarily, and in this situation, we need to look more proximally when the venous waveform is flattened on the on one side only.
And when we did that very simply, this was the external iliac vein, completely thrombosis here with no flow.
That was as high as we could get.
And so the, the thrombus we were seeing in the common femoral vein was just the tip of the iceberg, if you will.

Renal Transplant Asymmetry

Here's a patient who had a renal transplant.
This is the transplant and the color is applied, and as you can see, it's rather oddly asymmetric color.
There's considerably less color in the upper pole than in the lower pole.
These are the arterial waveforms we obtained from the upper pole compared to the lower pole.
So what is going on here?
Are either of these normal and what do they imply?
So the, the key here is again, to look more proximally on the upper pole.
We found the artery that was supplying that area had very, very high velocities and a significant amount of turbulence on the lower pole had a, an artery as well.
And that wave form looked very similar to the one in the arcuate.
So what were we dealing here with?
Two renal arteries and the upper pole had a renal artery stenosis, it was significantly affecting the quality of flow in the upper pole and with just diffusely decreased color flow.
Here are the high velocities and this is the classic parvis tardis waveform distal to the stenosis.
In the lower pole, we didn't have a stenosis, but we had high resistive indices, both in the renal artery supplying that area and in the arcuate vessels.
This is the angiogram of that patient.
You can see the two renal arteries.
This is the stenosis for the upper pole here.
And after a stent was placed, the perfusion of the kidney became much more normal across from upper to lower pole, and the waveform became similar, upper and lower.
They were all high resistance, but now they were quite similar.

Changes Over Time in Renal Transplant

Another patient with a renal transplant.
We're looking at the arcuate arteries again, this was the patient in 2013 when the patient had normal waveforms and a normal reive index of 0.72.
A year later, the patient came to us and you can see the the color flow again is qualitatively decreased throughout the kidney.
We're just looking at the lower pole.
The resistive indices have gone down and there is now clearly a delay in systolic upstroke.
So between 2013 and 2014, we now have obtained a subtle change in the waveform, a shift to a parvis tardis.
So again, this tells you to look more proximally for the stenosis.
The prior case we looked more proximally and we found the stenosis in one of two renal arteries.
So let's see what happened in this patient.
We went to the main renal artery.
We did not find any elevated velocities or increased turbulence.
Here we are at the level of the anastomosis.
You can see the external iliac vessels, but here as well, the systolic upstroke is delayed.
So there was no stenosis of the renal artery.
Well, now what do we do? You keep looking more proximally.
We went to the external iliac artery, proximal to the anastomosis, and again, no high velocity and a delay in systolic upstroke.
In addition, as you know, in the external iliac artery, we should have had a phasic waveform.
It should have looked like the common femoral artery that I showed you.
And we now have a monophasic waveform, again abnormal, but we have not yet found the level of the abnormality, so proceed more proximally.
And finally, when we got to the right common iliac artery, there we found the high velocity 713 centimeters per second and the increased turbulence, this is the contralateral left common iliac artery for comparison, a normal phasic waveform with a normal velocity.
So this led us to an iliac stenosis that we would not have otherwise known.
We found the effect on the kidney and just kept tracing it back further and further to find the source.

Distal Disease Example: Carotid

So those are going more proximally.
You can also have issues that may be more distal.
This patient came for carotid sonogram and here are the color images in the proximal common carotid artery, the proximal internal carotid artery and the distal internal carotid artery.
All of these had normal color images.
There was no plaque that we could see.
However, the velocities and the waveforms are distinctly abnormal.
The carotid circulation should be a low resistance kind of pattern with a monophasic waveform.
And as you can see here in from the common to the internal and the proceeding more distally, these are high resistance waveforms.
There is no flow during diastole.
These are clearly abnormal.
In addition, the peak systolic velocity is progressively decreasing from 51 to 20 to 13, obviously an incorrect pattern.
So no stenosis here, but waveforms that tip us off to something that's now going to be more distal in this patient.
We can't look more distally with, color doppler in this situation.
This patient had an angiogram and you can see that there was an occlusion eventually along the way, at the ophthalmic origin.

Incorrect Direction of Flow

Now we'll turn to how, what things happen when there's incorrect direction of flow in a vessel and what information you can glean from it and where you might look otherwise.
And the kinds of, incorrect direction that we'll look at are the vertebral artery, the external carotid artery, the jugular vein, the portal vein, and the hepatic vein.

Vertebral Artery Reversal

This is a patient in whom we're looking at the, vertebral arteries.
And the vertebral artery is normally, as you can see on the right side, a monophasic low resistance vessel because it is supplying, the brain in nice sharp upstroke and good diastolic flow.
When we looked and, this in this color image, you can see that we're looking at the artery.
The vein is next to it.
This is the shadow from the vertebral arteries in between.
So we know that we're looking in the correct direction and the vein is in one direction and the artery in the other.
When we got to the left vertebral artery, we had complete reversal of flow and you should check this by comparing usually to the, the common carotid artery.
So we're going to go in color, from the common carotid artery.
There we go To the vertebral artery.
You can see pulsing between the, vertebral bodies, the carotid artery in red and the vertebral in blue.
They should both be the same color.
And this is a good, way to make sure you haven't, done something incorrectly.
Even if you had the colors mis registered red blue and they should still both be the same color, whatever color that might be.
If the carotid was blue and the vertebral is blue, you just had just need to invert the color.
So this will imply to us this is the so-called subclavian steel.
And this tells us, that there is a, a subclavian occlusion and reversal of flow through the vertebral system.
That's not uncommon.

External Carotid Reversal

This situation of reverse flow in the carotid circulation is much less common in this patient.
We've set the color so that what's coming towards the transducer, is blue and that's the incorrect, direction of flow, right?
The common carotid artery flow should be going, towards the brain.
When we looked at the external and internal carotid arteries using the same color, pattern, as you can see, the internal carotid artery was going in the correct direction up towards the brain.
The external was reversed, as was this small piece of the common carotid artery.
So what is happening in this situation?
This is the spectral doppler to go along with it.
The external carotid artery was reversed.
The internal carotid artery had very low velocity and a poor upstroke because it was being supplied essentially as a collateral from the external carotid artery.
The common carotid much further down was occluded.
And so we had a pattern set up as can occasionally happen where collaterals from all around the thyroid trunk and the subclavian region were supplying the external carotid artery, which had retrograde flow to the bifurcation and then antegrade flow through the internal carotid artery with parvis tartus waveform to supply the brain.

Internal Jugular Vein Reversal

Here's a patient who came to us for a carotid ultrasound, a history of TIA and this patient happened to have a dialysis fistula in the left arm while we were imaging the carotid circulation, obviously the colors on and we happened to notice the flow in the internal jugular vein nearby.
This is the normal right side and you can see the carotid artery in red and the jugular vein in the reverse direction with a normal phasic kind of flow pattern because we're relatively close to the heart when we went to the left side, however, the carotid was still fine, but the internal jugular vein had reversed flow.
The flow is going in the same direction as the common carotid artery.
Remember, this patient has a fistula in the upper extremity.
So what was this telling us here?
Certainly nothing about the carotid circulation, that was fine.
But there's something going on here on the venous side, reverse flow in the eternal jugular vein in a patient such as this or in general, and implies that there's probably a high grade stenosis or more likely even an occlusion of the brachiocephalic vein more centrally.
So if we look at this patient who went on to have a venogram, we injected here, peripherally and instead of going centrally, there was an occlusion and the flow went up the internal jugular vein.
In a retrograde pattern.
This is very common in patients who have dialysis fistulas and have had many lines in.
And so that was the tip off in this patient.
The patient then went on to have an angioplasty and a stent placed here, as you can see.
And now when we inject, we are filling more centrally.
The patient came back to us in ultrasound after the procedure and we re-image the left side.
And now you can see color in the correct direction, still obviously in the carotid and now in the correct direction in the, ipsilateral internal jugular vein since we opened up the brachiocephalic occlusion.

Portal Vein Reversal in Portal Hypertension

Other places that flow can reverse and it's extremely important to make this diagnosis are in patients who have portal hypertension.
This is a patient with cirrhosis.
You can see the nodular liver and ascites and we're looking at the port of hetus where normally regardless of how you set the flow colors towards or away from the transducer, the hepatic artery and the portal vein should have flow in the same direction.
And here we've labeled it with the artery red and the portal vein is blue, it's going in the reverse direction.
This is not uncommon in patients, with portal hypertension to have flow away from the liver.
That's pretty straightforward.
What happens is that sometimes there are odd variations that you have to be sensitive of.
This patient also had cirrhosis and during the same examination, sometimes the flow was away from the liver in the portal vein and sometimes the flow was towards the liver.
That's not uncommon.
You sort of get a sloshing back and forth when the levels of flow are fairly low.
It can be intermittently one way or the other.
So look for a little while and see what's happening.
This is still very important information.
This is another patient with a history of cirrhosis and the main portal vein had flow in the correct direction with some, ity.
The left portal vein had flow going in the same direction.
But with a little bit of compression of the transducer, we reversed the flow.
What's going on here? Same thing, quiet respiration.
You can have reversal flow.
So again, these patients are fairly sensitive, to subtle changes in respiration compression with transducers.
And these patients can sometimes reverse the flow and you shouldn't be surprised that this might happen occasionally.
How about this patient? We turned on the color at the port of hetus and what is the direction actually of the portal flow?
In some cases we were able to doppler something that had flow away and in some cases towards literally almost at the same time, there's red and blue all over the place.
The key here is that there actually is no portal vein left.
These are multiple collaterals that the port of Hetus and we call this cavernous transformation of the portal vein.
Sometimes one of these can be a little bit large and somebody might choose that one, label it the portal vein with flow in the correct direction.
And it's very important to not miss this diagnosis.
What if the patient was going to be sent for a tips, in which case they need to shunt from a hepatic vein to a portal vein when in point of fact there is no portal vein to shunt into.

Helical Portal Venous Flow

Here's another thing that can happen to the portal vein.
This is a fairly good sized portal vein.
You turn on the color and what's going on.
It goes red, blue, red, all in the same image.
This is not changing during time with respiration or compression.
This is at the same time you can see flow here.
And depending on where you doppler the flow will be below or it will be above.
This is a situation where if I, if you think about it in a 3D kind of format, you actually have a tube and the blood flow is ally flowing like this.
So it goes towards away, towards away.
And we call this helal portal venous flow.
The spectral doppler will depend on where you place your cursor in the helix of flow.
This can occasionally be found in normal patients, but it's more common in patients who have liver disease or have something, diffuse liver disease or something wrong specifically in their liver.
If you see it in a transplant patient persisting over time, it may be a tip off that there's a portal.
Vein stenosis, true bidirectional flow is rarely simultaneous.
So this is flow in the correct direction towards the liver.
It's just an hel pattern.

Hepatic Vein Reversal in Budd-Chiari Syndrome

Reverse flow can occur in other vessels in the liver, and this is a color Doppler image of the main hepatic veins up high in the liver and red is towards the transducer.
Blue is away. The hepatic veins should predominantly be away from the transducer as are the left and the middle hepatic veins.
But the right hepatic vein in this patient was persistently in the incorrect direction towards the more towards the transducer.
And in addition, there were multiple odd vessels curving around in this area of the liver.
There aren't normally vessels that do this of this size in the liver.
This is a clue to a patient who had chronic Bud Keri syndrome.
And you can see here these unusual vessels because of the central occlusion of the hepatic vein on this side.
So Bud Kiri syndrome is hepatic venous outflow obstruction.
There are a variety of causes both congenital and acquired, in gray scale that hepatic veins may be completely absent, there may be stenosis, the inferior vena cava may be narrowed and there may be an enlarged caudate load in Doppler.
There can be absent or reversed flow and this can affect some or all of the hepatic veins.

Color Doppler Pitfalls

Now let's look at some color doppler pitfalls or un pitfalls, things that you should be aware of.
This is a kind of not uncommon one unfortunately, and and I would show it to you and caution you to be careful about it.
So we're imaging this patient who had ascites and routine imaging, and this is a fairly normal color Doppler, setting here in the pulse repetition frequency.
You can see a nice normal hepatic artery here and it looks as though there is no color flow in the portal vein.
So is this portal venous thrombosis clearly a very important diagnosis to make.
Well, don't be drawn into this pitfall.
Make sure you maximize any kinds of settings.
And when we changed the PRF and made it more sensitive, we were able to pick up flow in the correct direction in the portal vein, albeit at a relatively low velocity.

Lower Extremity Veins

Here's a patient. We were asked to look at the lower extremity veins for swelling.
This is what the common femoral vein looked like in color.
Looked fairly normal, the color was turned on and there was color throughout the vessel.
Well, does this mean it's normal?
You know that you have to do compression and when we compressed, we had only a little bit of compression in the, common femoral vein.
So this was not normal at all.
The color was made too sensitive.
The PRF was too low in this patient and the color completely overwhelmed the hypo coic thrombus.
So you need to set correctly and also, believe your compression, which was abnormal.

Carotid Occlusion vs. Low Flow

This is an older case of a 39-year-old who had had a severe cough and pneumonia and then developed some neurologic symptoms and came for, carotid ultrasound.
These images were brought out and, allegedly were sh the person, doing the study said that the left internal carotid artery was abruptly occluded.
We in made the PRF more sensitive and were able to pick up a very, very tiny flow, in the middle of the vessel.
Very abnormal pattern of flow and low velocities that we could only pick up with a more sensitive setting.
Here's the, the, the, angiographic, views and from the MR angiogram.
And, this was consistent with a long segment dissection with thrombosis of the false lumen of the vessel and very, very low level flow that we only picked up with sensitive settings.

Internal Carotid Occlusion

Here's a patient. This is a gray scale image of the internal carotid artery, which doesn't look too bad in terms of plaque.
We turned on the color and the power though, and it looked as though we weren't getting flow in this portion of the vessel.
Here's the Image of that and you can see how helpful the real time images in the CIC clip.
You can see the flow bumping up against this thrombotic, material, which was so, low level echogenicity that in the gray scale you could almost not appreciate it, but the flow bounces up and it's very, very, high resistance as it does against that, occlusion.
So the color doppler in this case makes it more obviously, that it's occluded.

Post-Biopsy Pseudoaneurysm

How else to keep yourself out of trouble and not fall into pitfalls by using color.
This is a patient who had, this is a kidney that had been, biopsied and all of a sudden cyst popped up in this kidney.
Well, is this a cyst?
Always make sure to turn on the color and you can see that there was flow in here towards the transducer away from it, and we were able to find the, this towards and away flow at the neck of this pseudo aneurysm after a biopsy color.
Can sometimes, show you that there's some abnormality, but you have to be careful about what it actually shows.

Renal Transplant Pseudoaneurysm Mimic

This was a patient who had a renal transplant and we were looking at the main renal artery and it looked like there was some sort of branching little aneurysm coming off the vessel here.
And we were worried about a pseudo aneurysm.
The patient hadn't had any biopsy or anything happen to that vessel.
When we did the doppler, we had very high velocities and a lot of, diastolic flow, low resistive index.
The arcuate vessels here, however, were the tip off.
This is a doppler of the arcuate vessels in the kidney and you can see that they were slightly par tardis with a low resistive index.
So what was going on here was that this was the main renal artery.
This was a branch vessel with an extremely high grade stenosis and marked post stenotic dilatation, which was simulating masquerading and aneurysm.
And this was the post angioplasty color, again, is helpful all the time in the kidneys to keep you out of trouble.

Hydronephrosis Mimic

This patient was having right flank pain is this very mild hydronephrosis and we should go looking for hydroureter and a calculus.
Always turn on the color when you think it's low grade hydronephrosis because this is just prominent veins in the kidney.
This is the color compare.

Stenosis Without Elevated Velocities and Vice Versa

Now let's turn to stenosis without elevated velocities and steno, no stenosis, but with elevated velocities.

High Velocities Without Stenosis

Here we have a patient, and this is the right internal carotid artery and the left internal carotid artery.
The peak systolic velocities are 1 36 and 1 39.
They're slightly higher, than the, the normal range.
Well are, they're moderate ICA stenosis in this patient.
The key here is that there are very normal color, images where these waveforms were obtained.
You have to make sure that the color goes with the, with the doppler before you are calling any kind of stenosis.
And if you don't see a stenosis, then figure out some other reason why the velocities might be high.
And there's a laundry list of reasons for having diffusely.
High carotid velocities. Younger patients are very common.
They have higher cardiac output if the patient has exercise tortuosity, if your ankle corrections are abnormal.
And you can have it unilaterally if on the contralateral side there's a high grade stenosis or occlusion.
Here's another example.
We had fairly high 203 centimeters per second in the mid, internal carotid artery.
And if you look at this composite picture, you can see just how tortuous the vessel is, how difficult it is to get a true, angle correction, and that the velocities were higher around this bend.
This patient does not have a stenosis.
You should comment that the velocities are high, but do not read this out as a stenosis merely based on the peak systolic velocity.

Low Velocities with Significant Stenosis

Let's look at this patient here.
We have images on the right side and the left side and symmetry and symmetry of velocities and waveforms again is important.
So in the internal carotid arteries, there's not that much difference In peak systole, a little bit of difference, but not that much.
Here we have about 50 centimeters per second here, 56, the diastolic velocities are a little bit off 11 and 18.
As we went more distally, however, the differences were accentuated on the left side, which was remained normal.
This peak systolic velocity of 86 and end diastole of nearly 35 in the internal carotid artery On the other side, the peak systolic velocity was considerably lower and there was virtually no end diastolic flow.
Nonetheless, there was no obvious, stenosis here in the color.
When we looked further in the color, a little bit more distally, we could see that there was a high grade narrowing and a little bit of color flow getting through, but we had no high velocities.
And to understand this, you have to remember what happens as the stenosis.
The degree of luminal narrowing increases.
The velocities increase in a fairly linear fashion until you get to a very, very, very high grade stenosis.
And then the velocities can become variable, decreasing eventually to an occlusion.
And depending on where you are along here, you might have high, fairly normal or even low.
So in this situation, and here you can see the CTA, there was a very, very high grade stenosis.
We were somewhere on the low end of the curve, so we had low velocity, but a very significant stenosis.

Miscellaneous Topics

And now just for a few miscellaneous items.

Mirror Image Artifact in Carotid

This patient came for carotid ultrasound for TIA.
This was what the common carotid artery looked like.
There was no plaque, we didn't see any areas of narrowing and there were normal waveforms and normal velocities.
However, these were images from the gray scale.
I'm showing you sadly on the left and transverse on the right.
And if you look at these, you'll see that there's some sort of odd linear thing in the middle of the vessel and it's pulsing here and it's pulsing here.
And you can see that in both of these.
This was actually interpreted by a somewhat novice person as a common carotid artery dissection and it's caused a lot of consternation.
Patient went on to have other imaging studies which, were actually normal.
Well, what's going on in this situation and how could we have used doppler to, figure this out?
Well, this is the same patient, and while we're imaging and transverse, you can see that line.
And then we compress the jugular vein and the line goes away.
So here's the line we compress and it's gone, right?
It comes back. When we don't compress, we compress the vein and this alleged dissection flap disappears.
So this is not a dissection, this is a mirror image artifact from the jugular vein that we can get rid of by squashing the jugular vein.
This is the, actually the CTA that the patient had.
There's absolutely no dissection at all.
Now, in addition to figuring this out with the mirror image artifact, we also should have understood that something that this wasn't a dissection based on the spectral doppler itself.
And to illustrate that, I'll show you the kinds of velocities and waveforms that you get if there is truly a dissection.

True Dissection Example

So this patient had a type a aortic dissection that was coming up the carotid artery.
This is the dissection flap.
And what you need to do in that situation is to take doppler on both sides of the flap and there will be some abnormality, one side or the other.
So you can see in the larger lumen here, there were pretty normal low resistance wave forms In the smaller lumen, which was probably the true lumen, which was very high resistance, you can see more high resistance wave form.
So this is a true dissection as opposed to the pseudo dissection.
And this was the CTA.
You can see the dissection here in the aorta going up the carotid artery.

Intra-Aortic Balloon Pump Waveforms

Other miscellaneous kinds of things.
This is a doppler in the common carotid arteries bilaterally.
What in the world type of waveform is this?
We saw it bilaterally and symmetrically.
It kind of almost makes you think of the hepatic vein venous kinds of waveforms.
Well, this is what the waveforms look like when a patient is on an intraaortic balloon pump in which the pump, makes this extra systolic peak.
And you can't measure diastole here.
I mean, you can attempt to, you can't really even measure systole.
You can look at the images and if you see something that looks like a stenosis, get somebody to turn off the pump for a few beats and take a true waveform.

LVAD Device Waveforms

How about this one? Both common carotid arteries and in fact, all the vessels had these odd sort of looking waveform, sort of neither arterial or venous.
Well, what's going on in this situation?
You can see vertebrals, common carotids bilaterally.
This is a patient who's on an LVAD device and this is the kind of waveforms that you get on that device.

Slow Portal Flow and Echoes

This patient had a history of primary sclerosis and cholangitis and had cirrhosis, a large caudate lobe.
And you can see in the gray scale imaging there were weird or just echoes in the portal vein.
This was just very, very slow flow.
And so I'm just showing you some odd kinds of moving echoes that can occur.
This wasn't thrombotic yet, but you'd certainly, be concerned that this was going to go on quite soon to perhaps a portal vein thrombosis.
So that's slow portal flow.

Portal Venous Gas

Here's the patient who actually has portal venous gas.
This flow is not slow, but there are all these little bright echoes in it just pouring in and going out into all of these little portal radicals, enhancing them if you will, like bubbles and contrast.
And when you turn on the spectral doppler here, you get a normal portal vein waveform, and then these bubbles of spikes all over.
Those are the bubbles superimposed and it will sort of enhance all the portal flow in the liver.
So this is portal venous gas normally flowing.
There's no thrombosis as opposed to the other case.

Post-Cardiac Catheterization Needle Tract Flow

And lastly, this patient had a recent cardiac catheterization and we were asked to look at the groin for, hematoma.
When we looked at the common femoral artery, we had normal phasic waveforms, but there was a little branch or something odd coming off the common femoral artery, which when we doppler it had a monophasic waveform.
Well, what was this waveform? Why did it change?
And what was this odd perhaps branch vessel?
This is actually flow in the needle tract, and it's not, a pseudo aneurysm.
Typically these will close off, but they often have monophasic flow, and you can report it out, but doesn't typically need to be followed even.

Summary

So in summary, I hope I've showed you, a variety of possible pitfalls, pitfalls you shouldn't, fall into.
We've looked at spectral doppler and arteries and veins that can at times look very similar.
Looked at incorrect direction of flow in unusual locations as a key to important diagnoses.
I would caution you to always compare side to side because subtle changes in waveforms may be a key to more proximal or distal disease.
Color doppler pitfalls are common and you need to be careful about them.
And always remember that significant stenosis can occur without elevated velocities and vice versa.
Thank you.