Doppler Ultrasound of the Liver and Portal Hypertension - HD

Doppler Ultrasound of the Liver and Portal Hypertension

Good afternoon.
My name is Wei Chung.
I am from the University of North Carolina,
and I'm going to be talking about Doppler ultrasound
of the liver and portal hypertension,
Doppler ultrasound of the liver and portal hypertension.

Technical Factors in Portal Hypertension

The portal may have slow or reverse flow
or may be thrombosis.
Detection of slow flow requires optimizing
Doppler parameters.
This involves setting the focal zone at the level
of the portal vein, minimizing the wall
filter on the right.
We have images of the wall filter set at a high
setting and a low setting.
The wall filter basically eliminates all the
low frequency signals.
So when you have a high wall filter,
this black band here represents the
low frequency signals that have been suppressed.
Since we want to detect slow flow,
we do not want a high wall filter.
And by changing to a low wall filter, we can see that
that black band is removed.
There are other factors that
can increase the sensitivity that you can
do these include
establishing a slow velocity range,
creating a small Doppler angle, making the portal vein
as superficial as possible
by putting the patient in a different position such
as decubitus or scanning intercostal.
And finally making the color box as small as possible.
All these factors will increase your
sensitivity to slow flow.
Finally, remember
that spectral Doppler is more sensitive than color
for slow flow aliasing
aliasing is the artifact
that you see in the image on the left here.
This is the portal vein, and you see blue
and yellow color within the portal vein.
Does this represent reversal of flow? It does not.
The reason you're seeing blue
and yellow color is that the velocity range is above the,
peak set by the color scale on the left here.
So since velocity within the portal vein are greater than
0.3 meters per second,
then you get a wraparound artifact,
and the velocity that are higher than 0.3
meters per second appear as blue or yellow.
So this artifact can be eliminated
by increasing the velocity range,
and we can see that this is the exact same portal vein.
And by increasing the velocity to
0.4 meters per second, the
false color blue
and yellow color within the portal vein has been eliminated.
It's important to recognize aliasing
because it may create a false impression of reverse flow.

Appearance of Cirrhotic Liver

On the right is a gray scale image of a cirrhotic liver.
The liver here shows a very nodular contour
and a heterogeneous echo pattern.
The nodularity is better seen in cirrhosis,
the nodularity of cirrhosis is better seen
when there is ascites.
So this patient has ascites
and the nodular appearance of the liver is
clearly seen here.
Once you look for liver lesions, the presence
of collateral vessels, vascular anatomy,
and the presence of ascites,
if there is no ascites present, one can increase sensitivity
for detection of nodularity
and abnormal liver parenchyma
by evaluating the liver surface with a high frequency probe.
Here, a linear five to 10 megahertz probe has been optimized
for the near field, and it demonstrates nodularity on the
liver surface as well
as a heterogeneous echo pattern consistent with cirrhosis.

Normal Doppler of the Portal Vein

The normal Doppler
of the portal vein increases postprandially
increases when supine
and has a velocity of between 20
to 30 centimeters per second.
Flow is hepatopetal with mild respiratory variation.
So in this Doppler image,
the cursor has been placed over the
main portal vein,
and you have a velocity of 0.27 meters per second,
or 27 centimeters per second.
Flow in the portal vein is laminar in the mid portal vein.
That is to say it is faster in the center
of the vessel than along the periphery,
but as the
portal vein approaches the porta hepatis, it tends to,
flow in a somewhat helical manner like
a spiral staircase.
And this will create an appearance that you see on the right side, you'll see red
and blue here in a kind of braided appearance
as the blood spirals its way up into the liver.
This helical flow pattern is normal,
but it becomes accentuated in the presence
of portal hypertension following liver
transplant and post TIPS.
So here's an example of the helical flow pattern.
Within the intrahepatic portal vein past the porta hepatis,
you see red and blue.
The blue in this case does not represent reversal flow.
It just represents the blood spiraling
upwards into the liver.

Normal Hepatic Vein Waveform

The normal hepatic vein waveform is phasic.
It is composed of a S wave
and D wave in the antegrade direction.
And the hepatic vein antegrade flow is away from
the transducer and therefore below the baseline.
Then when the
right atrium contracts, it sends a spike
of reversed flow known as the A wave.
So the normal hepatic vein waveform is said
to be triphasic.
Two forward spikes of flow and one reverse spike.
That means
that during ventricular systole
flow in the hepatic vein will be antegrade
and will appear blue as it
flows away from the transducer towards the IVC posteriorly.
But when the right atrium contracts,
you will get a spike of reverse flow.
So reversal of flow during the cardiac cycle is normal in the hepatic vein.

Abnormal Hepatic Vein Patterns

Loss of the phasic pattern in hepatic vein is abnormal.
On the right here we see an image
of a hepatic vein waveform, which is monophasic.
The normal S and D waveforms
and reverse spike of flow in the A wave
are not present.
This is a sign of reduced liver compliance
and is seen in cirrhosis
where it is considered a poor prognostic sign
and is also seen in infiltrative liver disease.
The other cause of loss
of phasicity in the hepatic vein is Budd-Chiari syndrome.
On the other hand, exaggerated phasicity in the hepatic vein is a
sign of congestive cardiac failure
or tricuspid incompetence.
The forward flow
or S/D flow should always be larger than the A
or reversed component.
In this case, we see forward flow
and reverse flow of equal dimension on the Doppler spectrum.
This is abnormal and is a sign of heart failure
or tricuspid incompetence.
This is a color Doppler image on the left
and a gray scale image on the right of heart failure.
Note that the hepatic veins and IVC are dilated,
and that on the color Doppler, the color shifts from red
to blue in equal measure.
This is a color analog of the waveform that we saw.
Here where you have forward and reverse flow
in equal measure.

Portal Vein Waveform in Cardiac Failure

In cardiac failure, the portal vein waveform
can also be abnormal.
This patient has congestive cardiac failure
and the exaggerated phasicity in the hepatic vein has been
transmitted into the portal vein.
Remember that the normal portal vein flow is always
antegrade with mild phasicity.
It should never go into reverse, as in this case
where there is a pulsatile portal vein waveform with reverse flow during part of the cardiac cycle.
The color Doppler image shows the portal vein flipping from
red to blue to red with each cardiac pulsation,
and this is a sign of congestive cardiac failure
and tricuspid regurgitation.
It can also be seen in abnormal flow states such
as hereditary hemorrhagic telangiectasia due to high volume
or in arterial portal shunting in cirrhosis
portal hypertension.

Example of Portal Hypertension Due to Cirrhosis

This is a video clip of a patient
with portal hypertension due to cirrhosis.
We see a nodular cirrhotic liver, ascites,
and on the color Doppler portion of the image,
we see a pulsatile vessel in the liver hilum, as well
as a hypoechoic tubular structure posterior
to this pulsatile vessel that does not have any flow.
So what is this tubular hypoechoic structure
and what is this pulsatile vessel?
Well, the pulsatile vessel is actually a
hypertrophied hepatic artery.
The tubular structure without flow is a thrombosed portal
vein, and this patient has a number
of features seen in portal hypertension,
which we will go over in a little bit more detail.

Sonographic Signs of Portal Hypertension

The sonographic signs of portal hypertension are
splenomegaly spleen larger than greater than 12 centimeters,
or area greater than 45 square centimeters.
Loss of respiratory variation in the SMV
and splenic vein caliber
Increased resistance in the hepatic artery pulsatility index
of greater than 1.0 splenic artery
and renal artery resistance also rises the splenic artery RI rises
to greater than 0.6,
and the renal artery resistive index is greater than 0.7.
The latter can be a sign of hepatorenal syndrome.
Hepatorenal syndrome is renal failure developing secondary
to renal artery vasoconstriction as a result
of portal hypertension.
The vasoconstriction in the renal artery leads
to activation of the renal angiotensin system,
and this causes renal failure or,
and is known as the hepatorenal syndrome.

Hepatic Artery Hypertrophy

The hepatic artery hypertrophies in portal hypertension
because the body responds by the increased
pressure in the portal venous system
by sending more blood into the liver
through the hepatic artery.
So this is a color Doppler clip
and a spectral Doppler of a patient with a cirrhotic liver
with a large hypertrophic hepatic artery that shows up
as this pulsating multicolored vessel.
And the portal vein is patent,
but is almost the same size as the
bulked up hepatic artery,
and it shows up as this area in red here.
It's almost hidden by the strongly
pulsatile hepatic artery.

Portal Vein Enlargement and Flow Changes

Other sonographic signs
of portal hypertension are increased in
size of the portal vein.
The portal vein is measured
in gray scale from the inner anterior wall
to the inner posterior wall at the crossing point
with the hepatic artery
or greater than two centimeters from the bifurcation.
A portal vein is considered enlarged if it is greater than
1.2 centimeters in diameter.
As the portal hypertension worsens portal vein velocity
drops lower and lower,
and eventually you reach a stagnant state normal portal.
Vein velocity is greater than 0.2 meters per second
or 20 centimeters per second.
This patient has very slow
antegrade flow in the portal vein down
to 0.05 meters per second, or five centimeters per second.
And as the velocity drops lower
and lower, you reach the stagnant state where you have
slow to and fro flow with little bit of blood going
forward and little bit of blood going
retrograde.
So this is known as the stagnant or to
and fro flow in advanced portal hypertension.
As portal hypertension worsens even further flow starts
going into reverse.
So this patient has complete reversal of flow.
We see that the portal vein is entirely in blue
while the hepatic artery is this multicolored vessel
running anterior to it.
This is an image of the intrahepatic portal vein.
In this patient, we see the hepatic artery,
which is hypertrophied
and in red, while the portal vein running next
to it is in blue, indicating complete reversal of flow.
So reversed flow in the portal vein is a sign
of severe portal hypertension.

Portal Vein Thrombosis

Portal vein thrombus portal
vein thrombus occurs in the setting
of portal hypertension due to the
slow flow in the portal vein and stagnance.
You can also see portal vein thrombus in acute pancreatitis
in abdominal sepsis
and in tumor invasion from hepatoma metastases
or pancreatic cancer.
Acute thrombus is usually hypoechoic
and may be indistinguishable from flowing blood.
The portal vein is dilated
and here is a case of acute thrombus of the portal vein,
which appears the vein itself does not
has very few internal echoes,
but the vein is shown to be thrombosis
by the absence of color flow.
The hepatic artery is the vessel running anterior to the
thrombosed portal vein.
Eventually, as the thrombus evolves, it becomes chronic
and the portal vein,
the thrombosed portal vein becomes more echogenic.
Multiple collateral vessels then develop
and run in the bed of the thrombosed portal vein.
And this appearance is known as chronic thrombus
or cavernous transformation of the portal vein
on the gray scale image.
Here we see instead of a single hypoechoic vessel running
into the liver, we see an echogenic portal vein in
which is embedded multiple tubular structures consistent
with collateral vessels.
And this is the color Doppler image of this patient showing
that the multiple tubular structures are actually small
collateral vessels.

Varices

Varices formation sites
of natural portosystemic venous communication.
These sites are closed in normal patients,
but when portal pressure rises,
blood is shunted from the portal circulation into the
systemic circulation at these sites
of natural portosystemic venous communication, the sites
that are visible on sonography are the splenorenal varices,
gastroesophageal gallbladder recanalization
of the umbilical vein and the coronary vein.
The coronary vein is actually the left gastric vein,
and it comes off the splenic vein and runs posteriorly.
This is a recanalized paraumbilical vein.
The recanalized paraumbilical vein arises
from the left portal vein.
It runs inferiorly in the falciform ligament
towards the umbilicus.
Eventually, it joins the systemic epigastric veins at the
umbilicus creating a cluster of veins known as
known as a caput medusae.
So this gray scale image shows the
paraumbilical vein coming off the portal vein,
then running anteriorly on the sagittal image
towards the umbilicus.
Here we are following the recanalized umbilical vein
towards the umbilicus.
Gastroesophageal varices connect the coronary vein
and the azygos vein.
On this sagittal clip here through the left lobe
of the liver, we see a cluster of vessels running anterior
to the aorta,
and posterior to the left lobe of the liver.
The esophageal hiatus is roughly here at this point, and these vessels are
large gastroesophageal varices
as shown on this color Doppler image.
Splenorenal varices are found at the splenic hilum.
They appear as a bunch
of tortuous veins in the splenic hilum
that eventually empty into the renal vein,
creating a spontaneous splenorenal shunt.
This color Doppler clip demonstrates a bunch
of splenic varices emptying into the splenic
vein.

Pre-Sinusoidal Portal Hypertension

Portal hypertension can be presinusoidal, that is
to say the obstruction to the portal flow occurs
proximal to the liver, within the liver from cirrhosis
or parenchymal liver disease,
or distal to the liver at the level of the hepatic veins.
We are now going to talk about presinusoidal portal
hypertension, and one of the causes of
presinusoidal portal hypertension is liver schistosomiasis,
which is one of the most important causes worldwide.
Schistosomiasis is caused by a parasite known as a trematode,
which lodges in the venules of the mesentery.
It lays eggs, and these eggs eventually get trapped in the
liver and create a granulomatous reaction.
This granulomatous reaction causes an fibrosis,
and the result is a dense fibrotic reaction forming
around the portal vein.
This gray scale image shows
the portal vein here embedded within an echogenic
cuff that surrounds the portal vein and its branches,
and the portal vein eventually becomes narrowed
by this fibrous reaction.
And the obstruction to the portal vein leads
to portal hypertension.
This appearance of the liver is known
as the tortoise shell liver,
as shown on this T2 weighted MRI
where the fibrous bands appear as
high signal structures within the liver,
somewhat resembling the shell of a tortoise.
On this color Doppler image, we see that
the portal vein here is occluded.
There is echogenic
material surrounding the portal vein on either side,
and this is the fibrous reaction.
This is the hepatic artery here.

Post-Sinusoidal Portal Hypertension (Budd-Chiari Syndrome)

Post sinusoidal portal hypertension is caused by obstruction
at the level of hepatic veins.
This is otherwise known as the Budd-Chiari syndrome.
The causes of the Budd-Chiari syndrome are,
it can be idiopathic tumor invasion from hepatoma
coagulopathy pregnancy
and oral contraceptive predispose to
hepatic vein obstruction,
and rarely from obstructing membranes caused
by certain toxins.
The sonographic features of Budd-Chiari syndrome
are obliteration of the hepatic veins lost
or attenuation of the normal pulsatile pattern
and intrahepatic collateral vessels.
Acute hepatic vein thrombosis will appear
as in the form of a filling defect.
So this is an example of an acute hepatic vein thrombosis.
This is hepatic vein draining into the IVC
and within the hepatic vein,
we see an echogenic filling defect, which is a clot,
however, Budd-Chiari usually presents in the setting
of chronic hepatic vein obstruction.
And this slide illustrates the appearance
of chronic hepatic vein obstruction.
On the middle and right hand side,
we have chronically obstructed hepatic vein.
On the left is normal hepatic vein for comparison.
So a normal hepatic vein has a hypoechoic lumen
and the wall of the hepatic vein is very thin
or imperceptible.
The waveform within the hepatic vein is phasic
with a forward S and D waveform,
and a small reverse A waveform.
This is chronic hepatic vein obstruction,
and the vein is markedly narrowed in its luminal diameter
while the wall, which is this echogenic structure next
to the lumen, is markedly thickened.
This is color Doppler image showing a markedly narrowed
hepatic vein with a thick echogenic wall.
And the waveform from this vein is monophasic.
And this is a gray scale clip of a patient with
Budd-Chiari syndrome in the sagittal plane.
The caudate lobe is markedly enlarged.
This is one of the features of hepatic vein obstruction.
You see multiple tortuous tubular structures
running through the liver that do not correspond
to the normal anatomical hepatic or portal veins.
These are portal venous
collaterals running from the portal vein
to the hepatic veins that have formed as a result
of the hepatic vein obstruction.
And we see here on this color Doppler clip
through the same area that the blood is running
through these collateral vessels is blue.
That's to say they're running away from the liver surface
towards the IVC.
So the liver is enlarged specifically the
caudate lobe, and there are multiple intrahepatic
collateral veins
that do not follow a normal anatomical course running from
the surface of the liver peripherally towards the IVC.
And they will appear blue.

Vascular Stenoses

Hepatic Artery Stenosis

Hepatic artery stenosis
produces a tardus parvus waveform
distal to the point of stenosis.
On the left is a normal common hepatic artery,
and the normal waveform has a sharp upstroke
in early systole.
The tardus parvus waveform is characterized
by a much more gentle upstroke in early systole,
a resistive index of less than 0.5
or acceleration time of greater than 80 milliseconds.
The acceleration time is the time it takes from the start
of systole to the point where it starts
to flatten off over here.
So in hepatic artery stenosis,
the acceleration time, the time it takes
to reach maximum velocity is prolonged.
The resistive index is lowered and in this patient,
this waveform was obtained at this point here, marked
by this small red arrow.
The stenosis is shown by this narrowed arrow here,
more proximally by the tardus parvus waveform is
seen distal to the point of stenosis.

Portal Vein Stenosis

The portal vein stenosis is caused by
post hepatectomy
or an anastomotic stenosis in the context
of a liver transplant.
The portal vein can also be narrowed in patients
with pancreatic cancer.
This is a color Doppler clip of a patient
with portal vein stenosis.
The normal portal vein is here
and we see a marked narrowing
or waist form at the point of this red arrow
with an increase in velocity as the blood goes through
and aliasing as a result in the post stenotic area.
So we have turbulent post stenotic flow marked by this blue
and yellow area distal to the point of stenosis,
which is marked by the red arrow.
This is a corresponding angiogram showing a stenosis in the main portal vein.
This was an anastomotic stenosis in a patient
who had undergone liver transplant.
A velocity step up of three to one is considered significant
for portal vein stenosis.
On the left is Doppler spectrum of a patient
with a liver transplant showing a marked rise in velocity
of greater than three times pre stenosis to the
stenotic point where we see a velocity
of greater than two meters per second beyond the stenosis, the velocity drops again.
And on the gray scale image,
this stenotic area is clearly shown by this
arrow showing the point of narrowing.
There is also dilatation of the portal vein distal
to the stenosis.

Hepatocellular Carcinoma (HCC)

Hepatocellular carcinoma can appear as a solitary mass
or a multifocal
or diffusely infiltrative mass within the liver.
It can be a variable echogenicity on sonography,
and it's characterized by
high flow intratumoral vessels on color Doppler portal
and hepatic vein invasion are seen.
So this is a patient with a large HCC within the liver,
and the portal vein here is full of echogenic material,
which actually can be seen on this gray scale image,
which is invasion of the portal vein
by the tumor.
This material within the portal vein is actually made up
of living tumor, as is shown by this color Doppler image.
The arrow points towards the thrombus within the portal
vein, but within the thrombus we can actually see
little flecks of color.
And that's because this is a living thrombus.
It's actual tumor tissue.
And what we are seeing here is the tumor vascularity within
the living thrombus.

Arteriovenous Fistula and False Aneurysm

Arteriovenous fistula is a
abnormal communication between the hepatic artery
and the portal vein or hepatic vein.
This is a patient with a large arteriovenous fistula caused
as a result of liver biopsy.
We see this area of abnormal color Doppler with
mosaic appearance, multiple colors,
and we see a large feeding artery in red here, as well
as a draining vein.
This is another patient who underwent a
liver biopsy, and the gray scale image
after the liver biopsy shows a complex, partly solid,
partly cystic mass inside the liver.
But if we look closely at the cystic portion of the
mass, we see that there is some movement within it.
So this is not a simple hematoma
and color Doppler here shows
a red and blue pattern, which is,
has been described as the yin yang or Korean flag sign.
And this is a sign of a false aneurysm.
The red and blue is caused
by blood entering the false aneurysm, circulating
and swirling around the false aneurysm and then exiting.
So this is a large false aneurysm caused
as a result of liver biopsy.
This is the corresponding CT image showing the feeding
artery and the large false aneurysm.

Post-Transplant Arterial Portal Fistula

And finally, this was a patient
who had had a liver transplant a few days earlier
and had abnormal liver function.
This was the color Doppler image from the liver hilum,
and it shows a very abnormal pattern.
We see this vessel here in blue,
and we also see that it's very high velocity flow
because we see aliasing here.
So this vessel we see a high velocity vessel
with flow headed away from the liver,
and we see that the portal vein on the gray scale is
markedly dilated.
This high velocity vessel is arterial, as you might expect.
It's very turbulent with velocities
of greater than three meters per second.
This was an arterial portal fistula.
The hepatic artery had fistulized into the portal vein
and was sending a jet of arterial blood retrograde
into the portal vein, away from the liver.
This is shown by on the MRI in the form
of early opacification of the portal vein
during the arterial phase, a markedly dilated portal vein.

Conclusion

So in conclusion, Doppler ultrasound findings in cirrhotic
portal hypertension include a nodular heterogeneous liver
with ascites enlargement
of the spleen greater than 12 centimeters
or greater than 45 square centimeters.
A hypertrophied hepatic artery with increased resistance,
a pulsatility index of greater than 1.0
increased resistance in the splenic artery
and renal artery dilatation
of the portal vein greater than 1.2 centimeters, slow flow
less than 20 centimeters per second,
and then with worsening portal hypertension,
stagnant flow, then reverse flow.
Additionally, there's an increased incidence
of portal vein thrombosis
and development of portal systemic collaterals in
the form of varices.
The splenic vein and SMV may also demonstrate dilatation
and reversal of flow, as well as loss
of respiratory size variation,
and the hepatic veins may demonstrate a monophasic
or flat waveform.
Thank you.