Mesenteric Duplex Evaluation - SD

Introduction

Hello, my name is Billy Zang.

I'm the former technical director at Penn State, Milton Hershey's Vascular Lab.

I now am the clinical marketing manager at GE Healthcare.

And today I'm gonna talk to you about the mesenteric duplex examination.

Mesenteric Duplex Evaluation Lecture

Okay, let's move to the mesenteric duplex evaluation lecture.

Just like you're doing any other abdominal work, you're going to have a high system requirements, and they're gonna include a system that has great resolution, and to have that great resolution.

It's gonna have to be probably the higher end systems that the major manufacturers have.

Although I can tell you that the mid-tier range systems also provide some pretty good resolution nowadays, as well as some of these compact systems are coming out.

So I do encourage everyone to look at all the systems and all the vendors to make sure that you choose the appropriate one.

And if you have antiquated systems and you're trying to do abdominal work, you may want to change out to get this ability to have this high resolution with high PRF scales that you're gonna need good color sensitivity, certainly good flash depression, because you're gonna have that no matter how good the machine is.

So if you can lessen the extent of that, it'll make this abdominal or any abdominal examination easier to do.

And imaging enhancements such as harmonics and spectral reduction, those little things that'll help you find these vessels a lot more easier, and obviously show them to your interpreting physician.

And when you find some type of anomaly, will make the interpretation much more accurate.

Transducers

Transducers. If you've listened to a renal exam before any abdominal exam, most people will start with the curved linear transducer, and the mesenteric system is no different.

You also want to have the ability to have that sector scan available to you if you have to use windows, especially if they're the windows going through the ribs.

And sometimes because these patients in a mesenteric duplex situation are come in with losing a lot of weight and may be very, very thin, you may be able to get away with using some type of linear transducer.

But certainly remember that most of these transducers that we see have multi frequency bandwidth, and you can choose the different higher end frequencies if needed, or go to a lower end frequency within one transducer.

So use that to your advantage when you're doing any type of abdominal examination, especially a mesenteric examination.

One thing you will find yourself doing in most cases is really going for that lower frequency because of the penetration problems that we'll come up to when we do any type of abdominal exam.

Patient Preparation

The patient preparation is gonna be the same as we would for a renal duplex examination.

You're probably not gonna have any trouble having the patient be NPO, like you may with the renal examination.

'cause unfortunately, as we're gonna see, one of the indications and the main indication is abdominal pain, and these people most of the time have a fear of food.

You will still need to ask them just like doing the renal exam, not to smoke or chew gum because it will introduce air into the system.

And then also you can have these patients take medicine with small sips of water and in the mesenteric examination, although I'd like to have that patient in the morning, unlike the renal where probably the renal examination can wait to the patient can come in the next morning, sometimes a mesenteric examination needs to be done right away, although we should be seeing these patients in a chronic situation.

But sometimes an acute situation will come up and this is a life-threatening problem.

And if duplex can help diagnose that, then certainly we want to bring that patient into the lab.

Common Indications

Some common indications I just mentioned that postprandial pain or pain after eating is one of the big ones.

And with that, this patient probably is going to come up with some type of fear of food because of that severe pain they have every time they eat.

Coupled with that, you're gonna have weight loss.

So often, quite often these patients will come in very thin and test oil vaginal or abdominal pain of unknown etiology.

So frankly have no clue what's going on that ubiquitous abdominal bruery.

That really tends to make you think that you have to look at every artery until you find something.

But certainly if it's coupled with abdominal pain, then you probably are looking at the mesenteric as a culprit as if you were looking at somebody that had a lot of hypertensive problems and were many medicines without abdominal brewery, you would be thinking that maybe the renal artery is the problem.

Any follow up of any surgical intervention of the spl system is also a common indication for patients that come into your lab for this examination.

And these patients are commonly misdiagnosed for things such as eating disorders and gallbladder problems.

So they may be very, very frustrated and you need to be aware that nobody, they seem to feel that nobody knows what's going on because we're kind of the last result.

And what is no better feeling than the feeling you have when you actually find something that can possibly be fixed on these patients that are really, really sick when it's caused by chronic mesenteric ischemia.

So it's something that one of those things that you can pat yourself on the back for, for really helping out this patient that may have gone through a long road before they got to your vascular lab.

Coexisting Conditions

Coexisting conditions that you need to be familiar with.

Atherosclerotic disease, obviously of the mesenteric system, affects the property approximately 18% of adults greater than 65.

So the patient population that you're gonna be coming, that will be coming into your lab will not be unlike the patient population that we see for peripheral arterial disease.

The older patients are the ones that will be more susceptible to this disease.

Patients that have diabetes will also present patients that smoke tobacco and nobody's unfamiliar with effective tobacco on the arterial system.

So certainly if they're the patient is a smoker, they have a higher incidence or a chance of having some type of athero disease that may affect the mesenteric system as well as any artery in the body.

Generalized atherosclerotic disease of the carotid coronaries, renals or extremity in the artery also is an indicator that this patient may have this disease in these organs.

And so what you also find is that females have this more often than men.

And an increased incidence of AA is also found with patients with mesenteric ischemia or renal artery or the stenosis within the mesenteric system.

Patient Positioning

Patient positioning is not unlike we would use for the renal artery examination.

You can see some good friends of mine helping out with these pictures.

Stephanie Rose is scanning Lori Watson here, and Lori is in a supine position with her hands above her head like the renal examination.

This exam may take over an hour to perform, and so the patient may not be able to sustain this type of positioning, but you will note that you will get a better access to that proximal portion of the aorta as it comes through the diaphragm, and that's right where that celiac axis will probably be.

So you may want to start with the hands up here like this, and then maybe move the hands down as you move towards the SMA and the inferior mesenteric artery.

Certainly you have the ability to go and put the patient in lateral acute position if you're really having trouble.

But unlike the kidney, you're pretty far away from the organs or from the origin of those celiac and SMA arteries as well as the IMA may have a better approach using this type of patient positioning.

But certainly you would want to use the liver here as well as the left lobe of the liver when you have the patient in a supine position from the medial approach.

B Mode Imaging

Okay, so in B mode, we are going to kind of identify the anatomy, look for disease segments and look for other pathologies such as this dissection that we see on a patient that had marfan that presented to the lab at the Hershey Medical Center, Penn State's Medical School in Hershey.

Also you want to kind of look for little clues and signs of things that may go wrong.

It's probably not typical to see this celiac artery curve like this.

Frankly, a lot of times the celiac artery will come straight off and you'll be insinuating it at less than a 30 degree angle and most some of the times at a zero degree angle from the midline approach.

And that SMA looks appropriate here.

Usually you can get this at 45 to 60 degrees.

But when I see this curved area right here, I'm suspicious that maybe there's a median ligament compression that's taken place.

So from a b mode image, kind of pay attention to that and look for any disease within the aorta, which is also a sign that there may be disease within the mesenteric system.

Color Doppler

Color's gonna help us really identify exactly where that disease may be located by the color aliasing that happens when you have increase in velocities.

You can see a nice little color blurry that is noted in this image right here.

It'll help us guide the doppler signal then into this specific area.

So we can take that spectral doppler waveform and measure the peak and end diastolic values and use those as a grading system for a percent stenosis in our interpretation spectra.

Dopa, therefore will identify that disease and categorize it.

Spectral Doppler

Just like the renals, we don't have to rely on angles always at 60 degrees.

And in fact, it'll be very, very difficult to obtain 60 degree angles throughout this whole exam and frankly, probably impossible.

And you also wanna note that you don't have to maintain a 60 degree angle and you have a better shift coming back and a stronger shift if you can get to that zero degree angle.

And that is the most favorable.

The one thing that you do want to take into consideration is if the patient returns.

You wanna make sure that the same angle is used if you're comparing those velocities.

So that is something you wanna make sure of.

So I'll reiterate the fact that you do not have to maintain a 60 degree angle throughout the entire mesenteric duplex examination, but you do want to make sure that you have the same type of angle or close to it if you're trying to compare these velocities.

And certainly you do not want to have an angle that's greater than 60 degrees.

And if you do, you wanna make note of that.

So the interpreting physician can include that as a part of the interpretation, saying that these velocities may be overestimated due to the fact that it was impossible to obtain a angle of insonation of less than 60 degrees.

You wanna make sure that systolic velocities are maintained or obtain, because you're gonna use that as a marker for the disease, as well as the end diastolic values.

Looking for post stenotic turbulence right here, we can see that, and that is a clear indicator that something happened proximal to this vessel.

And something that we need to note when we are showing that we have seen a disease segment and the tardis parvis waveform is really gonna be a very strong indicator that you had a more proximal critical stenosis and something that you can feel very confident about if you display that that you in fact have seen a problem within that artery that needs to be evaluated a little further.

Anatomy Overview

Here is a nice drawing from Dr. Netter of the classic anatomy, and you can see that this first major branch off of the aorta as it comes through the diaphragm right here is the celiac axis, and there's three branches that come off of the celiac, the left gastric, which kind of moves up towards the head, toward that, towards the stomach.

And we don't really see that in the plane that we are scanning in, to the left, we will see the hepatic artery moving towards the liver, and to the right we will see the splenic artery moving towards the spleen.

And those are the arteries that we interrogate that splenic and hepatic along with the celiac when we're doing this examination.

We also look at the SMA, which is located right below this area, and the IMA, which is located a pretty good distance from the SMA, but should be incorporated within this mesenteric examination.

And I frankly, and we'll talk about this, kind of have a transverse view of the aorta, go down to the bifurcation of the iliacs and then move my way back up.

Cephalad to the area of the IMA, we wanna take an aortic signal.

We wanna look for any evidence of aneurysmal disease, and we wanna make sure that there's no inflow stenosis within this vessel.

'cause obviously, an inflow stenosis, anything above these arteries that we are interrogating the celiac, the SMA and the inferior mesenteric would cause a flow reducing problem within these vessels.

So interrogating the aorta is very, very important.

Look for both flow stenosis and also looking for aneurysm disease.

Celiac Artery Interrogation

The celiac artery is probably the first artery that you will interrogate, and you can see a nice gray scale image.

The left gastric artery actually can be seen on most of these patients.

And you see this artery right here as we move from into the celiac, with the left gastric artery located right here.

And we see the splenic artery.

Also, what we don't see is the hepatic artery, which is probably out of plane and somewhere out here in space.

We do see the SMA and we see nice angles that we can use that are gonna be much less than 60 degree angles or right at 60 degrees.

So very appropriate.

And also we see the color avenue that we could use to identify where this vessel is.

And typically it looks like some type of seagull that you may draw when you're a little kid.

And maybe frankly, this is probably the best way I can draw a seagull now, even that I've passed that stage.

But it does have this same type of pattern, with the aorta here, the celiac axis.

Can you see how short that celiac axis is, giving branches off to the common hepatic and to the splenic artery?

This anatomy that we see here is typically seen in 65 to 75% of the patients.

But as we all know, when we dealing with vessels, there's a plenty of different types of anomalies that we can see within the system that we have to look out for.

And nothing is ever perfect in many of these cases.

So we need to be aware that this, the hepatic arteries can come off the splenic, we can have common origins and things like that.

So that waveform in a normal celiac artery as we put our Doppler signal within, that usually has a very high diastolic flow component.

It's low resistive.

We're looking at peak systolic and end diastolic values to define disease.

We want to keep our angle insonation parallel to the vessel wall, and we certainly wanna take samples throughout the length of this very short celiac axis before it splits into the common hepatic and to the splenic artery.

We wanna make sure also that there's no turbulence signals throughout any of these any of the portion of the vessels that we are interrogating as we move out into the hepatic and the splenic arteries.

We will note the same type of waveform morphology in a normal situation with high diastolic flow, nice systolic rise time.

And they'll be noted both in the splenic and the hepatic arteries, those vessels, as you saw in that example where I said it looked like a seagull, will kind of curve around.

So angles of insonation are important to regard.

You may not be able to obtain a angle less than 60 degrees in the same midline position you may have to move the transducer laterally or even reposition the patient to obtain a less than 60 degree angle in these arteries.

And in fact, just to go back to this other slide, we will also note that we would have to take the proximal distal portions of both the splenic and the hepatic artery as it moves towards the respected liver and the splenic or the spleen itself.

Diagnostic Criteria for Celiac Artery

Diagnostic criteria, I'm sorry, in the celiac artery really are based on Dr. Moneta's landmark paper in 1991 in the Journal of Vascular Surgery, where he noted that a PSV velocity above 200 centimeters per second, coupled with that post stenotic turbulence and also a tardis parvis wave form would be a strong indicator of greater than 70% stenosis.

Doctors Ack at a Dartmouth also looked at the end diastolic values and came up with some criteria that looked at 55 centimeters per second, and the end diastolic portion of the waveform indicating a greater than 70% stenosis celiac artery compression is something I'd like to quickly talk about.

Celiac Artery Compression (Median Arcuate Ligament Syndrome)

I actually have some great slides from one of my favorite teachers, Cindy Owen, and luckily one of my great friends that really do a great job in talking about this issue that we may see within the celiac artery diaphragmatic crura is really something that I frankly have never taken the opportunity or never did until I learned about this to look for.

But it arises from the vertebral bodies in the location of this celiac artery right at the level of that diaphragm.

And that the crura passed the superior anteriorly surrounding the aortic opening and is joined by this thing that I am very familiar with, the median arcuate ligament at the aortic hiatus.

And this ligament is usually superior to the origin of this of the celiac artery, and in most cases does not play a role in causing a stenosis.

But in 10 to 24% of patients that you may see the ligament may be low and crosses over that proximal celiac causing an extrinsic compression.

And therefore high velocities when you're interrogating that and may in fact be the cause of that abdominal bruery that the patient came into your lab for as an indication.

And a small set of these patients will be symptomatic, in fact, but not very many.

Most of these patients will come in with asymptomatic symptoms in just that abdominal bru.

So it'll most commonly affect a patient that is younger, 20 to 40 years old, and these patients will mainly be female, and oftentimes they're very, very thin.

The characteristic indentation or hooked like appearance is something that you need to note on a beam mode image.

And I mentioned this earlier in this lecture, where I saw this B mode image, nice image of the aorta and the spleen.

The SMA and I have this hooked appearance to the celiac artery.

And that median arcuate ligament is probably causing that by its extrinsic compression.

Alright, when we think that this may be the problem, we need to put the patient in different positionings and also take them through some provocative movements in relationship to their breathing patterns.

This will decrease with inspiration as the lungs expand.

The celiac artery has more collateral orientation, and it decreases with an upright position.

So putting the patient in an upright position and re-scanning them usually will alleviate that stenosis, severe compression persists during inspiration and must be correlated with symptoms.

If we do see that post stenotic dilatation may be present with severe compression.

The SMA is rarely involved, and collateralization can occur from the SMA through the pancreatic duodenal arcade Doppler evaluation of this the waveforms should be obtained in both inspiration and expiration.

We should evaluate the patient, like I said in the supine and the erect position.

Look for the characteristic hooked appearance like I mentioned before, also in that B mode and the color duplex image, we can see a indication here where the velocities really are pretty high with inspiration, where we would think in this situation that they would be a little bit lower than with expiration, where you can see that raises a little bit.

But when I sat the patient up, and that's what Cindy did during this examination, you can see that these waveforms really dropped in their peak and end diastolic value saying, showing, and hopefully proving to the interpreting physician that the median arcuate ligament or the vessel orientation has changed just due to positioning.

And this is probably an extrinsic compression problem, but something you really really want to be aware of, especially when the patient presents with his abdominal brewing.

And you see no indication from the B mode in a color situation in any other vessel that there's a disease state taking presence when you do see things like this or especially when they're chronic and they are fixed, unlike the situation that we saw here where the patient kind of is put in this extrinsic compression situation based on their their orientation, whether they're lying down or standing up, it's there or it's not there.

Patients with fixed disease will often cause blood flow to move through arteries in different directions for compensatory reasons.

And unlike the renal artery, which is really the only artery that's going to the kidney to supply it with blood, the mesenteric system is supplied by all three of these vessels, and it is very well collateralized.

So paying attention to the other arteries that potentially could reverse directions and help out arteries that may be occluded or critically stenosis is something that you need to be aware of and take note of when you're doing this exam.

And the most important artery to note is a gastroduodenal artery, which arises off the common hepatic artery.

And in normal cases, of course, anterior to the pancreatic head and that flow direction that you would expect to see is towards the feet.

As you can see here, in normal flow direction with our probe orientation is showing that gastroduodenal artery coming towards our transducer, and here's a normal doppler signal, but as we have severe disease and the collateral pathway is being set up, we note that that GDA now is reversed.

And we can see that within the color spectrum and also within the Doppler spectrum as we move a the celiac artery into the SMA, we note that this artery is often very close in relationship to the SMA, I mean to the celiac artery.

I apologize and just superior to the renal artery.

So it's a nice marker for a lot of things.

In fact, I use the SMA as a guide to get me back to the celiac artery if I'm finding it hard to find that celiac artery because this SMA will move juxtapose and you can see it right here and cross-section layer or parallel to the aorta as it moves down into down through the abdomen.

So I can go a little bit further away from that very high transducer positioning underneath of the xiphoid process.

And start at the at the mid portion of the abdomen, find that in a cross section at SMA and the aorta, and then move my way back to the origin of this SMA.

And if I haven't found that celiac artery know that that celiac artery is a little bit proximal to the location of the origin of the SMA.

And we also note here, as we as we see a in the cross-sectional area, this is a good situation to know that you're close to the origin too.

'cause here's that left renal vein and here's that splenic vein and that SMA as well as that aorta.

And we know that this left renal vein is a good marker for the renal arteries, which you can see right here in this gray scale image.

And also a great marker to know that that SMA is gonna be right above it.

Okay? So that is something that you want to note as we move further distally.

Superior Mesenteric Artery (SMA) Interrogation

And you have the third artery that we're gonna interrogate the inferior mesenteric artery.

No, wait, moving to SMA first.

The SMA is located right below the celiac area.

(Note: Transcript flows to IMA after, but logically SMA before IMA.)

We see nice angles for SMA interrogation.

Inferior Mesenteric Artery (IMA) Interrogation

And you have the third artery that we're gonna interrogate the inferior mesenteric artery.

And you'll note that that artery is located further away from the SMA and the celiac than you would expect.

In fact, it's right above the bifurcation of the aorta.

So that is where I kind of search for it and how I search for it.

I do a cross-sectional image, take it down to the level of the bifurcation of the aorta to the iliacs, and then I go back cephalad.

And I note that that IMA is coming off in an anterior lateral position about one or two o'clock if you're using this as a clock.

And this being 12 o'clock here, and it's usually pretty easy to find.

A lot of people are intimidated or just skip it completely because they've heard it was very difficult to see.

But I encourage you to set your parameters right.

Look for that IMA after you found that iliac bifurcation, moving back cephalad, and at two o'clock, you should see it almost every time.

Normal Waveforms for SMA and IMA

The normal SMA and IMA doppler waveforms are gonna be a little bit different than the celiac waveform, which we noted before.

Celiac is predominantly gonna be feeding the liver and the spleen, and therefore, since they're high demand organs have a very high diastolic signal.

The SMA and the IMA in a patient that has been fasting is gonna be very resistant because the mesenteric is not demanding blood at this time.

So you can see this very different waveform when compared to the celiac artery.

Diagnostic Criteria for SMA and IMA

The diagnostic criteria for a greater than 70% stenosis is a little bit different than the celiac where we looked at 200 centimeters per second as being an indicator.

In Dr. Moneta's paper.

We are looking at 275 centimeters per second as being an indicator of greater than 70% stenosis within the SMA and Dr. Rolex lab also looked at the end diastolic value within the SMA and came up with 45 centimeters per second as a strong indicator that you are dealing with a stenosis of greater than 70%.

Now, you have to remember, every time that I say this or anybody really says that, they're also looking at other indicators to tell them that this is probably correct, and those are focal increases in velocities.

And that post stenotic turbulence signal coupled with a TARDIS parv waveform, if you can obtain it, which really is a good indicator that there is a problem proximal to this signal.

The IMA, if you do a literature search, you're not gonna find too much.

But I had the pleasure of being at RSNA two years ago, and Dr. Pato gave a lecture on IMA diagnostic criteria, and I think it was all on mesenteric criteria as a whole, but noted that he found the, and his lab, that 200 centimeters per second and an end diastolic velocity of greater than 45 was a pretty good indicator coupled with that focal increase of post stenotic turbulence and that tardis parvis waveform, if you can obtain it, of greater than 70% stenosis.

So that is something that you may want to look at.

And if we look at this video, we can see that this velocity is at that level of greater than 200 centimeters per second.

And this may in fact be a stenosis, but if I note here that color velocity or this color scale is not really showing that big of a bruery.

So I really want to look a little bit further distally, see if I pick up any turbulent flow in this situation or a TARDIS parvis wave form.

You can see this is kind of bending a little bit, so I'm still suspicious, but with this type of color duplex here, I'm not convinced just based on this waveform, that this may be, this may be being used as a collateral to feed a maybe a occluded or stenotic celiac or SMA, mesenteric occlusion, which you wanna remember when you see that is that this staccato flow pattern should be set up because of the really high flow states going through that aorta.

And if it's trying to push into an occluded SMA or celiac or IMA, you'll note that you'll have this very resistant waveform and kind of banging or knocking on the door type of pattern that I like to refer to as a staccato signal.

And also the color duplex as well as a spectral may show the occlusion and the retrograde flow that you will be aware of.

When you note that there's an occlusion within these vessels, because of what I said before that it's very well collateralized anomalies that you need to be aware of are most commonly right.

Mesenteric Anomalies

The replaced hepatic artery or the replaced hepatic artery in total, the pad artery arises from the SMA, in this case for the replaced hepatic incidence is up to 40%.

This presence of replaced hepatic artery alters flow dynamics, because remember, some people use that end diastolic criteria.

And if the hepatic artery is coming off the SMA and that hepatic artery is feeding the liver, your end diastolic value is probably gonna raise up a little bit.

So you probably want to rely on your peak systolic values if in fact you see that that replaced hepatic artery is in fact located within the patient that you're scanning.

Other mesenteric anomalies, there are origin of hepatic artery from the splenic trunk and the absence of a celiac trunk also with a presence of a celiac and SMA origin.

Some of these patients you all need to be aware that these situations may be set up when you're doing this type of examination.

Conclusion

With that, I'd like to thank you for listening to this lecture, and I hope that it has taught you something or refresh something that you maybe needed to have when you're doing mesenteric exams.

And good luck with this very difficult, challenging, and rewarding exam.