Color Doppler During Abdominal Ultrasound. Techniques, Applications and Pitfalls - SD

Introduction

Hello, I am Dr. Hehe Chpi from Wake Forest University.
I am the director of ultrasound
and I'm gonna be talking to you about
color Doppler application in the abdomen.

All right, this is a keyword
before we start, this lecture.
So to be familiar with, I would like you to get familiar
with the CDS.
It stands for color doppler sonography,
the CCTA Color Tail Artifact.
The others are self-explanatory
and that should be easy for you to understand that.
So let's move on to the next slide.

Why We Need Color Doppler

Now, why do we need color doppler?
This is a question we all ask ourselves about.
Basically to identify the direction of low
to help us identify abnormalities is not anticipated
by the use of a gray scale imaging,
and also to aid us in our decision making strategies when
procedures like biopsies or drainages are
requested by clinicians.
The other important point is you need
to prevent disasters outcomes when abnormal vascular
structures are mistaken.
For abscesses or other masses,
color doppler sonography must be included with all
of your abdominal imaging studies.

Flow Direction and Imaging Components

So this is a slide showing the flow direction
that we appreciate On an image,
we see the gray scale in the background we give,
we see the overlay of the color doppler
and we can see in the bottom
of the slide the specter wave doppler.
So we have the combination of all three in the same
view or the same image.

Now what color doppler implies you have your color
saturations, you have your color maps, you have the velocity
and the doppler shift.
We're not gonna get into details into the physics
of their concepts, but the understanding
of the basic principles is important
for the purposes of this lecture.

Color Doppler Versus Spectral Doppler

Now, color doppler versus spectral doppler,
when you look at spectral doppler,
it's a small region sample.
Many times we are using about 30
to 256 samples per display line versus color doppler
where you are using fewer samples.
Eight 16 per display line and mean frequency shift display.

Now based on what we are getting, we are trying
to get something called the doppler shift,
which is the frequency shift.
This is, this phenomenon is observed when sound is reflected
from a moving target.

Factors Influencing Doppler Shift

Now the next slide is we are gonna discuss the
factor influencing doppler shift.
These are very important factors that you need to consider
while you are optimizing your color doppler.
The first one is frequency of the sound used.
The other one is the angle of the scan,
and the last one is the velocity
of lowering blood, the RBCs.

Frequency

Now frequency, what are you gonna use?
You're gonna use high or you're gonna use low.
The concept is you need to understand the advantages
of each of the two.

Now, higher frequency results in greater frequency shifts.
It's a more robust flow imaging,
but remember you can't use higher frequency all the time
because you're limited by the sound attenuation that will
affect the penetration.

Now we have two examples.
We have one slide on the right side,
we have another slide on the left side of the screen
and watch at seven megahertz.
I'm scanning this mass in the liver
and you can see the bulk
of the vascularity identified is in the superficial
component of the mass.

Now the same patient, same plan, I'm using a lower frequency
for megahertz probe
and you can see that I see more color doppler in the center
of the mass and in the deepest components of the mass.

Angle

The other component there is important to us is the angle,
the effects of the change in the angles
or the angle of insulation.
So lower scan angle will give you the best
or the highest doppler shift.
The optimum angle is zero degree
and the lower the angle the better the signal
and the higher the angle the less or worse the signal.

Now remember at 90 degrees you're not gonna get any
signal or doppler shift.

Now if you look at this slide, you can see the hepatic veins
nicely identified by color doppler,
particularly the middle and the left.
And if you look at the right HEPA vein,
you would see there's no blood flow.
So you don't want to jump to the conclusion that there is
a clot in this vein.
First you need to think I need to change my angle to be able
to see whether there is a clot or not.

So we go ahead.
On the next slide, we change our acoustic window
and as you can see, we can see a very nice
right hepa vein filling with color
and there is no evidence of clot
or any abnormality in this vein.

Velocity

Now we move to velocity measurements.
Higher frequency shift will correlate with
faster blood flow velocity.
It's good at showing relative velocities within a given
field of view, but you have
to keep in mind it is not a good measure
of the actual velocity.

Again, using color doppler,
you may get confused about some patterns of blood flow.
The reason why is that is
because we are limited by the construction of the probe
by the curvature of the probe itself and design.
So the angular flow is gonna vary across the image.
The color images or changes with angle to flow
will give you different blood flow.

Look at this example. The spin vein is coming all the way
to the level of the pancreas
and you can see at the midline of the transducer,
the flow pattern changes from going towards the probe
to going away from the probe.
This is normal accepted variation
and you have to be familiar with that.

Optimizing Color Doppler

Now we get to the most important element of this talk is
how we get the best of our color doppler on any machine.
So in other words, we need to optimize our color Doppler
achieving the best color doppler image is synonymous
with tuning a musical instrument.
You need to tune the instrument
to enjoy the sound produced by that instrument.
If you do it right, you will get the information you need
and help solve problems.
On the other hand, if you don't do it right,
you will get confused.
You'll make make erroneous diagnosis or maybe
or may miss an important one.

So optimizing a color dopper starts with an initial syrup.
The first you can look at parameters
and how we're gonna adjust them.
All these parameters exist on all
machines on the market today.

So the first parameter is acoustic access.
Alright, this is the easiest way
to do just if you can see what you're looking for.
Change the area from which you're accessing the organ
of interest and you can improve that by optimizing
the image, the color flow in the image.

The other thing is frequency.
As we said, choose high versus low based on
what you're looking at, closer to the surface, deeper
to the surface, and also consider the limitations of
how far the organ of interest is far from the surface.

Next parameter is scan angle.
Make sure you have the lowest angle possible
to achieve the best results.

The next parameter is color gain.
Set this at the noise floor level, the focal zone,
depth the area of interest.
Make sure your focal zone depth are always at the same level
of the area or the structure of interest that you need
to identify or interrogate.

With color Doppler power output,
the maximum allowable by the machine that you can get.

Now, beyond that initial step, you need to go
and fine tune your machine,
fine tune your color doppler settings.
This starts with the wall filter adjustments decrease
so that you can allow more RBCs
or red blood cells to come through the system
to be sampled the scale.
Decrease the scale. You will get more blood flow
or more color signal.

The color priority, this thing is very tough to
tell you how to optimize.
But the thing is many of the machines nowadays,
are like built in modality that you cannot change much
and it is part of the manufacturers pre-set
parameters.

The sample volume size increase the volumes increasing the
volume size also helps you
to get better flow in the area of interest.

The car box width decrease the car buck box width.
This help you to get the best out of
what you're looking at specifically it'll improve
your frame rate.

Frame averaging, increase frame averaging.
Again, adjust accordingly.
Make sure you don't have any color bleed
and make sure that the vessel of interest that you want
to interrogate is filled with color, confined to its lumen.

Artifacts in Color Doppler

Now color doppler has artifacts like any
other imaging modality.
Sometimes it can be good to have these artifacts
and one of those good artifacts
and my opinion is color aliasing.
But aliasing is the result
of an adequate sampling resulting from wraparound displays.
But remember, ambiguous displays on the image
may lead to confusion.

Now how does aliasing help help us?
It helps us to identify specific areas
and structures in the abdomen.
It can help us distinguish between arteries and vein.
We can also benefit from the artifact
by producing other artifacts
that can help us in our interrogation of the organ
or pathology in interest.

Now look at this image. You have a color double image.
You look at the portal vein, you see the portal vein going
in the right flow in the right direction.
It's al.
But if you look at the fifth part of the end of the vein
where the arrow is showing, you see some color map change,
this indicates color aliasing.
This color aliasing is not coming from
flow within the portal vein.
It's actually coming from a flow within the
nearby HEPA artery.
So this aliasing helps you distinguish between
what is a vein and what is an artery, which is a good sign
or a helpful tool without even interrogating the structure
With speaker wave doppler.

Power Doppler

Now we move to talk about power doppler.
Power doppler also is available
to us on all high end equipment.
It helps us to add to what we see with color Doppler
power doppler has advantages.
It is less angle dependent.
It does not suffer from aliasing just like color
doppler unfortunately.
It also suffers from
some limitations like you can't get information about
direction of flow, you can't get much
information about velocity.
But it also helps us
because it has a better signal to noise ratio.
You can also scan at a higher gain without
distorting the image.

Let's look at this example of this case.
This patient had a kidney transplant earlier during the day,
had a kidney biopsy and the clinicians wants us to evaluate
for left lower quadrant pain.
As you can see, you can see the kidney nicely
but you cannot really appreciate what's really exactly
going around this kidney.
So there's a concern for hematoma in this instance.

So power doppler comes to our help.
We do the power doppler
and you can see how the kidney is nicely outlined
with power doppler and you can see the surrounding hematoma
without much of a mass effect on the kidney.

Advantages of Color Doppler in Abdominal Imaging

Now let's look. Let's talk about color doppler advantages in
general including power doppler.
It'll definitely make your exams faster, it'll help you
to establish a new diagnosis.
It'll add value to your practice.
This value can be in areas like tumor,
resectability liver
and the pancreas, vascular injury, malformations, clots,
transplants, portal hypertension, and many other areas.

On the bottom line you can get a greater diagnostic
confidence, which is the most important feature.
Why color doppler is important when imaging the abdomen.

Must-Have Images Using Color Doppler

Now when we look at color doppler,
when we do color doppler in the abdomen, what are the must
to have images using color doppler?
You need to do the portal veins splenic vein,
evaluate the splenic vein direction
and the level of the hili also at the level of the pancreas.
Look at the hepatic veins with the IVC.

The hepatic ery is really not important as much
as the portal venous system or hepatic veins.
However this important,
this becomes important when you look at liver transplants
because that's the most important vessel you need
to interrogate to evaluate transplant for rejection
or possibly thrombosis.

We also look at the SMA and the SMV and the celiac axis.
Looking at these vessels helps us many times
to localize the pancreas.
When we're looking at the pancreas,
it helps us identify the pancreas
and may also help us localize lesions
of the pancreas better than when looking at the pancreas.
With in gray scale alone, the both kidneys,
we look at the kidneys with colored and powered doppler.

But any attempts to interrogate resistive indices
or attempt to measure these resistive indices
is gonna create a problems
'cause you're gonna get yourself into a dilemma.
What if they are elevated? What are you gonna do next?
Are you gonna switch
to evaluate the aorta, the renal arteries?
Unless there is concern for renal vascular hypertension,
we do not attempt to do resistive indices.

The abdominal aorta is also, you need to look at that so
that you won't miss any potential silent aneurysms
specifically in elderly patients.

Now as you look at this slide,
there are too many applications
where you can use cardo in the in the abdomen ranging from
portal hypertension to vascular malformations
even you can use it not for purposes
of evaluating a blood flow,
but to help you distinguish between what is bile duct
and what is a vessel in the liver.

Portal Hypertension

Let's have a look. Let's have an example. Port hypertension.
This is very important topic because
whenever you evaluate, when you scan the liver,
you have too many things you need to keep in mind.
There's a large population of patients
that have any chronic liver disease and maybe cirrhosis.
So these things you need to look at.

You look at the pattern
of the blood flow in the portal vein,
check if it's biphasic or reversed.
Now check if there's evidence
of portal venous aneurysms thrombosis.
Make sure you'll be able to distinguish
between a bland thrombus versus a tumor thrombus.
Look for size of port hypertension like
ly para umbilical vein venous collaterals.

Now remember if you want to do this, it's a good thing
to perform this using a C loop function
or you need to confirm
with spectral doppler the change in flow.
If you interpret your imaging,
you're just using static images.

Let's look at this example.
This video clip demonstrates biphasic blood
flow in the portal vein.
This indicates that there's presence of port hypertension.
This patient is sera. The reason also is to focus.
There's another reason you need
to focus on this slide is you look at the nearby arteries.
Look at these ies. The IES are big
and they demonstrate in color aliasing
and artifact that you can use to your advantage.

Another example, in this patient we see complete reversal
of the portal vein and we can see
that artery is causing nearby and showing color aliasing.

Another example of a patient with portal venous aneurysm.
You can see the gray scale
and you can see on the color doppler mixing
of the signal within the dilated component of the aneurysm.
And this is known complication
of longstanding portal hypertension.

The next thing you need to do about these patients
with advanced cirrhosis is they can come down with
a blood clots in the portal system.
If you look at this example on the right upper corner
of this slide, you can see on this gray scale without color
doppler there there's an echogenic material within
this portal vein.
So this indicates thrombosis.
Now notice that the portal vein is not expanding,
so this most likely indicate we are dealing
with a bland thrombus in this patient.

Now let's compare this slide
to the other slide in the lower bottom here on the bottom
right corner of this slide,
you can see the portal vein is coming into the liver.
It's very expanded.
You can barely distinguish it from the nearby liver
parenchyma, but you notice
that there is an arterial signal within that clot.
This raises the suspicion for a tumor thrombus
and in any satic patient with a tumor thrombus,
you need to always think about the presence
of hepatocellular carcinoma in these patients.

This is an example of an enlarged paraumbilical vein
that extends all the way to the surface of the abdomen
and goes all the way up north towards the chest.
So without color doppler, you may have a problem identifying
that component in the abdominal wall.
So color doppler is important in this instance.

Another example of for hypertension, this is an example
of massive sub hepatic venous collaterals in this patient
with port hypertension and cirrhosis.

Pitfalls in Portal Hypertension

Now, pitfalls you need to avoid in port hypertension.
You need to make sure that is the portal vein,
partially thrombosis or completely thromboses.
You need to scan with different probes,
change the frequency, optimize your color scale,
adjust your filter sittings and gain.

The second point is make sure you don't give a false
impression of a portal venous thrombosis.
In cases where there is sluggish portal venous flow,
which is a common finding in many s cirrhotic patients
on the other hand be aware of the fact
that you can falsely get the fact
that the portal vein is patent while it is clotted.
The reason behind that is you have two high color
sensitivity to low PRF low filter settings
and color override will distort your image
and make you believe that the vein is patent.

The other one, force reversal
of the right portal vein flow when sampling the right
posterior branch, be careful about this point
'cause flow in the right posterior branch.
In normal portal veins will go away from your probe
and will be encoded blue.
And on the spectra wave doppler,
this thing is gonna appear below the baseline.

It's an example of a pitfall when evaluating a portal vein
in this patient with cirrhosis at three megahertz.
You can notice that there's little blood flow going into the
portal vein raising the suspicion for
portal vein thrombosis.
Switching this doppler frequency to two megahertz,
we managed to fill the vein with nice color signal,
avoiding the diagnosis
and false diagnosis of portal vein thrombosis.

Another patient with port hypertension with cirrhosis.
If you look at this slide,
initially this interrogation was performed
with a very high scale demonstrating
that there is no evidence of flow in the portal vein.
The impression was complete occlusion
or thrombosis of the left portal vein.

Now improving the sensitivity sensitivity
of this slide demonstrate that there's a flow in the portal.
Vein bars reversed. So this is portal hypertension
and not portal vein thrombosis.

Another pit for that can be encountered.
When you get biphasic flow, you need to make sure
that you do not interpret any biphasic flow just based on
the pattern you encounter as cirrhosis
or port hypertension secondary to cirrhosis.
This is interrogation of the portal vein in a patient
who is known to have tricuspid valve regurgitation.

So this pattern can also be encountered in patients
with right side heart failure
and patients with tricuspid valve disease.

Also remember that if you,
if you identify isolated gastric varis,
make sure you don't think of port hypertension.
Think of splenic vein thrombosis.
The etiologies can be two, can be many.
However, don't jump to the conclusion
that this is for hypertension.

And another point that is important is clinicians many times
ask you to evaluate the splenic vein for thrombosis.
And unfortunately ultrasound is not a great tool to do that.
Why is that? Because you need
to interrogate the whole length of the spleen,
which is not really accessible with sonography.
So presence of in
of flow in a splenic vein does not exclude a splenic vein
thrombosis And always look for little hints.
Look for the look at the liver texture
and surface it's S nodular.
There's cirrhosis. Look for signs
of ized para umbilical vein check if there is
enlarged spleen or not.

Another example of portal hypertension
you can see in this patient when you look at this study,
you would say there is a flow going completely he patal in
this left oral vein.
But if you need notice carefully
the enlarged HEPA artery indicate there is some decrease in
the portal venous flow going into the S liver.
And you can see in this tiny anterior branch
of the portal vein there is reversal.

So that tiny reversal indicates that there's element
of portal hypertension in this patient.
So the complete combined color picture of the main vein
and the arteries and looking at the flow in all the branches
can help you to establish the right diagnosis
and not miss the possibility of reversal
of flow as in this instance.

Vascular Complications of Acute Pancreatitis

Now vascular complications
of acute pancreatitis can be evaluated with color doppler.
30% is seen without necrosis, 57%
with pan parenchymal necrosis.
So the most common veins
or vessels involved are the portal vein, the splenic vein.

Now remember you're gonna get cavernous transformation
of the portal vein as a result of occlusion
or thrombosis of the portal vein.
The arteries that are involved with acute pancreatitis
commonly are the splenic and the gastroduodenal artery.

Now remember the presence
of aneurysms will increase the morbidity
and mortality in these patients.
So attention must be made to exclude the presence
of these vascular complications.

This is an example of cavernous
transformation of the portal vein.
In this patient with acute pancreatitis you can see chaotic
vascular structures with that with disorganized pair of
of color indicating tiny little veins as a result of
occlusion of the portal vein.

This is another example of a patient with acute pancreatitis
who has multiple short gastric varis.
Look at the liver surface.
The liver surface is smooth,
there are no signs of cirrhosis.
So this is isolated.
This is a sign of isolated splenic vein thrombosis.

Another example of vascular complicated acute pancreatitis.
This patient with acute pancreatitis as you can see presents
with a large pseudo of the GDA
partially thrombosis color doppler helps us
to identify the feeder
and this will eventually end up going
to the intervention suite for embolization
to treat this complication.

Another example of complication, acute pancreatitis.
If you look at this gray scale image on the right hand side,
you would see there's nothing
or no abnormalities of interest to you.
But when you use color doer you can easily identify
that this cystic structure here is actually an
pseudo aneurysm of the splenic artery.

Tumor Vascularity

Color doctor also can helps us to look at tumor vascularity.
It can helps us to identify, characterize those,
but remember both malignant
and benign tumors can have increased vascularity.

This is an example of patient who presented
with right of quadrant pain.
Incidentally, we look at this liver
and we can see fairy liver.
The sonographer convinced me
that this is most likely a fairly sparing area
in common location anterior to the portal vein bifurcation.
As you can see that's the portal veins here.
Then we decide to go and evaluate this with color doppler
and to our surprise, we managed to identify
that there is a feeding vessel here in the center coming off
the portal vein and feeding this mass.
Subsequently the patient went to MRI
and this has been proven to be a hemangioma.

Another example of a mass in the liver.
This mass shows spoken wheel pattern
and this spoken wheel pattern is typical of
focal nodular hyperplasia.

A very large patient came for renal ultrasound
and this large patient came with ultrasound
and incidentally we identified a hypoechoic mass in the
lower pole of the right kidney.
And if you see, look at this carefully, you don't see much
of an acoustic enhancement behind this mass.
So we went and we did power doppler
and power doppler identified areas of increased vascularity
and this was subsequently proven
to be a renal SAR carcinoma.

Another patient who presented for renal ultrasound.
And during the examination incidentally we identified this
soft tissue mass.
In the bladder. We apply color doppler,
it's avidly vascular there.
So the patient did not have hematuria.
Nonetheless, she was taken for cystoscopy
and biopsy proven transitional SAR carcinoma
that was asymptomatic.

As I said earlier, Carl Doppler can help you in your
practice to identify and stage pancreatic cancer.
And this is a nice example
of a pancreatic cancer encasing the SMA,
the celiac axis in this instance
and the SMA, you can see the soft tissue mass surrounding
the celiac axis.

Another area where receptivity can help is
evaluating cholangiocarcinomas.
As you know, cholangiocarcinomas as not easy to identify
even with CT scan MRI may have an advantage
but ultrasound can identify the vasculature
and relation to the tumor.
Look at the tumor sitting here
and you have more than one sartorial duct dilated
and you can see the relationship of the tumor
and the thickened common duct.
It's close to the hepatic artery
but most of the time it's not invading the artery.
The sign here, the presence
of two more than two al duct indicate
that this tumor is not resectable.

This is the MRI of the same patient
and you can see the thickened common bile duct
indicating the presence of the tumor.

Aorta and IVC Evaluation

Again, you can also look at the aorta
and the IVC with colored doppler,
which is should be evaluated properly
during your abdominal exam
because you can identify pathology
that was is not suspected.

Now the most in common indication is you look at the aorta
or the presence of triple A or aortic aneurysms.
In our practice we feel that clinicians
and vascular surgeons feel happy if we give them information
about the perfusion of both kidneys by color doppler
above the level of the aneurysm when we identify it.

Now this is an important way to important uh, hint here.
Whenever you evaluate the aorta,
make sure you have the right settings
of your scale and frequency.
And this instance you have a lot
of aliasing in this aorta there is an aneurysmal irritation
but if there's a dissection you can easily miss that
and you adjust your scale
and that scale can help you confine your color signal
to the lumen and you can get rid of the aliasing.
And if there's any abnormality to the flow
or two liens, you should be able to identify that with ease.

Another example is the IVC.
You can look at the IVC
and you can easily be misled sometimes if you
start with color doppler.
This is an example where color override
can miss the diagnosis of thrombosis.

Look at this slide.
You see color doppler nicely filling the lumen here
and honestly if you get this still image by itself,
you would easily say everything is fine
because you don't see much expansion in the venous lumen.
But when you look at the gray scale,
the gray scale showed an echogenic material within that IVC
and that is consistent with a clot
that you can ev easily miss if you overwrite that clot
with color doppler.

Other Clinical Applications

Now other important clinical applications
with color doppler you can use for acute poly nephritis.
You can look for the presence of jets in the bladder
in patient with hydronephrosis you can distinguish
what is bi reduct from hepatic arties portal veins.
You can use the artifacts as we mentioned to your advantage
the CCTA or the twinkling artifact and also color aliasing.

Acute Pyelonephritis

Now acute poly nephritis,
the diagnosis can easily be made made by urine test
however many times patients present with flank pain
or right upper quadrant pain
and they need to distinguish
that from gall gall bladder disease.
So what are the features you can get?
A fo or diffuse process may mimic a mass lesion.

Now remember most of the time it's gonna be hypo coic area
and not hypoechoic area.
In other words, it's gonna be a bright area in the kidney
affected rather than a dark area.
And then you can get some urothelial
thickening if there's some hydro.
And color doppler of course will demonstrate evidence
of devoid signal in that area involved
with inflammation and infection.

So this is an example of an acute pine nephritis.
You look at the kidney, the kidney echogenicity is similar
to that of the liver in its most parts except when you come
to this portion in the inner polar to the upper pole of that
kidney and make sure that there might be evidence
of acute poly nephritis.

And this is the power doppler
and you can see the power doppler is filling nicely the
kidney except for this same area
and that's how you make the diagnosis of acute p nephritis.

Ureteral Jets

Color doppler can help us also evaluate for the presence
of jets in the bladder from the ureters.
Now keep in mind the following, if both are absent,
there is no clinical significance when both are present
but asymmetrical it may be significant
but most of the time there may be nothing
to go and identify.

The most important point here is if one is present
and the other one is absent.

Now how much time do you need to wait
to establish whether you can see the jets or not?
Alright, time varies
but sometimes you may have to wait 10 minutes to be able
to establish that a jet does not exist
or does not present on one or other or the other side.

The other thing is if you don't have a jet on one side,
just go and check the kidney and save yourself the time.
You may identify the cause behind that absence of the jet.
An example is as in this slide we see a nice jet
coming from one side.
There's no jet from the right side.
We go on the same right side
and we can identify hydronephrosis in the right kidney.

So here we managed
to identify the reason why we do not have a jet.
Because the kidney is obstructed, there's a blockage,
there has to be a reason for the absence of
that jet bi dilatation.

You can easily apply color doppler
and make sure that any cystic structure that is not filling
with color and you know it's an atomic course which is
important, is most likely a bile duct.

Conclusion

So in conclusion, we managed to go
and cover the color Doppler applications of the abdomen
and we need to keep in mind
that always include color Doppler evaluation
during your abdominal exams regardless of the indication.
Know and be familiar
with the most common pitfalls to avoid them.
Spend time optimizing your machine parameter
and always think where do I need to look next.

And please never aspirate
or drain any lesion anywhere in the abdomen if even if
you're a hundred percent sure that this thing is nonvascular
without applying color Doppler.

And thank you for your time and attention.