Transplant Sonography: Usual and Unusual Findings - SD

Introduction to Transplant Sonography

Good morning.
My name is Sandra Allison. I'm currently the director
of ultrasound at Georgetown University Hospital in
Washington, DC and I'll be lecturing about
transplant sonography.

This next lecture is transplant sonography,
and I'm gonna go over some
of the more common abnormalities found as well as some
of the more unusual findings.

Types of Organ Transplants at Georgetown

At Georgetown we have several types
of organ transplants.
We have liver transplants, kidney pancreas with some kidney,
kidney pancreas combinations.
We are also one of the few centers
that have small bowel transplants
and multivisceral visceral transplants,
which includes small bowel,
but may also include pancreas or, and or liver.

For the purpose of this talk, I will be going over
imaging of liver and kidney transplants.

Liver Transplants

Moving right onto liver transplants,
liver transplants are performed
for treating end stage liver disease,
and it's important to know
that there are actually more than one type.
There is whole liver transplantation,
but now in the setting of decreasing supply,
split liver transplants can be performed
as well as living donor.
Liver transplantation.

Ultrasound is the initial imaging modality of choice
for following up liver transplants,
but also detecting complications.
Liver transplantation is performed when life expectancy
without transplant is less than life expectancy
following the procedure.
The most common indication
for a liver transplant currently is hepatitis C, followed by
alcohol abuse and cryptogenic cirrhosis.

Surgical Technique for Liver Transplants

It's important to know when you're evaluating a
liver transplant the surgical technique,
and it may vary a little,
or there may have been some different part
of the procedure performed due
to variant anatomy in either the donor or in the recipient.
But the basic technique involves an end-to-end biliary
anastomosis, which is also called a cholo doco
colido ostomy, a hepatic artery anastomosis,
which is also end-to-end
and end-to-end portal vein anastomosis.
And then either an end-to-end IVC anastomosis
with the anastomosis performed both with the supra
and infra hepatic vena cava,
or what is called a piggyback anastomosis, which is an end
to side anastomosis between the transplanted liver
and the intact donor vena cava.

I mentioned earlier knowledge of the anatomy is key
to evaluating liver transplants
and knowing where to look at the vessels
and where to look at the anastomosis.
The other thing that's important is knowing whether a whole
or split liver transplant was performed,
because in the setting of a split liver transplant,
you do not wanna mistake for example, a bifurcation
of one supplying portal vein into a right
and left portal vein.

Routine Postoperative Ultrasound Evaluation

Our routine postoperative study includes
a gray scale evaluation to document either any collections
to look at the biliary tree
and also to look at the overall
appearance of the transplant.
The vascular anastomosis are evaluated with doppler
and I put this in here
because I think this is one of the most important parts
of the talk, which is knowledge of the anatomy.

Complications in Liver Transplants

Complications to transplants include complications
to the vasculature, the biliary duct, the parenchyma,
the per hepatic space, which includes collections,
and again, complications vary slightly between pediatric and adult transplants.

Normal Hepatic Arterial Waveform

This is the normal appearance
to the hepatic arterial wave form.
You can see that there is a brisk upstroke
and continuous suppli to the liver
during both systole and diastole.
A normal resistive index, which is shown here, is
between 0.5 to 0.8
and a normal acceleration time, which is not measured here,
is less than 0.08 seconds.

Hepatic Artery Complications

Complications of hepatic arteries include thrombosis,
stenosis, and pseudo aneurysm.
Hepatic artery thrombosis is
the most common vascular complication.
It occurs in up to 8% of transplants
and accounts for 60%
of all post-transplant vascular complications.
It's the second leading cause of early graft failure,
and it usually occurs early within the first 15 days,
either due to acute rejection
or prolonged cold ischemia time in the graft,
or due to small vessels in the graft.
It can also occur delayed in delayed setting many years
after transplantation, either due to chronic rejection
or due to stenosis in the hepatic artery.
This may present with fulminant hepatic failure,
delayed biliary leak relating from biliary necrosis
and relapsing bacteremia and sepsis.
Up to 60% of these patients
would require retrans plantation, but even
after re-transplant, the mor mortality rate approaches 30%.

Here's an image taken at the Port Heus three days
after transplantation,
and you can see that the portal vein is very easy to see,
but hepatic artery is not that obvious.
Even using the spectral doppler
and kind of marching around that area, it was very hard
to detect arterial flow.
The important thing to see here is a comparison
with the first day where the hepatic artery was patent
and also just very easy to find.
And so just this large difference from day
to day is already an indication of an abnormality
or a complication and is concerning
for hepatic arterial thrombosis.

In my word slide, I made a comment at the bottom of
syndrome of impending thrombosis.
And really what it is, is it's a recognizable pattern
that may indicate that a thrombosis will happen.
You can see a progressive decrease of systolic
and diastolic flow with the diastolic flow eventually
becoming absent.
And then we can see a, we may
or may not see a dampening of the systolic peak, sort
of like a parvis tars waveform.
And finally, a total loss of the hepatic waveform.
You can see that in this patient immediately post-op,
you can see a normal hepatic arterial pattern
in the right hepatic artery.
Actually this is near where the main hepatic artery is,
and you can see a brisk upstroke
and continuous forward diastolic flow.
The resistive index is 0.73, which is normal
on follow up next day, you can see
that the systolic velocity has now decreased from 83
to 27 centimeters per second.
The diastolic velocity has also decreased from 22
to 14 centimeters per second.
Again, the follow up examination demonstrates further
decrease in the peak systolic velocity and
diastolic velocity
and possibly dampening of the systolic peak.
And again, you can see here a progression further decrease
in velocity, further dampening of the systolic peak,
and eventually a loss of diastolic flow.
And here you can see the resistive index is one
and the p systolic velocity has really decreased.
And this patient presented,
or proceeded to thrombosis hepatic artery,
which was proven at angiography.

So again, this is a very good example
of why the knowledge
of anatomy is very important in this patient.
There was already a large concern
for hepatic arterial thrombosis,
and hepatic arterial flow could not be found
in the hepatic parenchyma,
but the hepatic artery was not easily found.
And it turns out with communication with a surgeon,
this patient actually necessitated a jump graft extending
between the aorta to the liver,
And he drew us a diagram
and showed us that the jump graft was extending, was
above the celiac artery.
So we went back to the patient, we looked for the aorta,
and we looked for the celiac artery,
which I don't have in these images, but superior to this.
You can actually see the graft extending off the aorta.
You can see the graft flow in it for a very short distance.
But then after that you can see thrombosis of the graft.
So this is important because when they went in,
they went right in this area,
and according to the surgeon, right in this area,
the surgical knot was projecting into
the lumen of the graft.
And this was the NIUs four thrombosis.

It's important to communicate with the surgeons,
as I said, as to the anatomy,
and especially when they deviate from protocol.
And I just wanted to show this picture
because the picture really, truly is worth a thousand words.
And when you can see here, this is
different institutions can have forms
that the surgeons fill out.
We're a little less formal,
but we do on occasion require a drawing from them
just to show you the variant anatomy so that when we go in
and evaluate the patient, we know where to look
for the anastomosis.
And this is just an example of one such patient
where an iliac arterial jump graft was necessitated.
And from the drawing here, it looks like it's extending from
below the renal arteries
and coming up and supplying the liver.
And so a lot
of times when we wanna look at the anastomosis, we have
to look here, and then we have to look where the second
anastomosis of the jump draft is
with the hepatic arterial system.

Hepatic Arterial Stenosis

Moving on to hepatic arterial stenosis.
This occurs in five
or up to 11 percent of liver transplant recipients.
It usually occurs at the site of anastomosis.
And within three months of transplantation, the causes include clamp injury.
There may be intimal trauma either from the presence
of a perfusion catheter or from disruption of the vasorum.
With result in ischemia of the arterial ends.
This can lead to thrombosis
and ischemia of the biliary tree, biliary strictures,
sepsis and graft loss.
The criteria we use is a peak hepatic arterial
systolic velocity greater than 200 centimeters per second.
You may or may not see an intra hepatic tardis parvis
with a resistive index of less than 0.5
or an accelerator acceleration time greater than
0.08 seconds.
And again, the importance of this is
that it may lead eventually to hepatic arterial thrombosis.

And this is actually a patient who's had a her transplant
two years before this examination.
And you can see that when we were evaluating the right
hepatic artery, a parvis art waveform was seen.
The resistive index in this case was 0.37.
We see a little bit of a slope here.
And same similar pattern in the left hepatic artery.
So we looked a little bit more closely in the
region of the Porto Hepititis.
And you can see on this image, frequently
with stenosis, the hepatic arteries can
be pretty difficult to find.
Perhaps they're small
or they're somewhat removed from the portal vein,
and you have to look for them.
You really have to prompt a search for these.
But in this case, you can see adjacent to the portal vein,
there is a suggestion of abnormal flow with disturbed flow in the area of the hepatic arterial stenosis.
And a wave from obtained from
that area demonstrated a very high peak systolic velocity
of 390 degrees.
And this area of stenosis was confirmed at angiography.

Another patient presenting with stenosis, again,
showing a parvis artis wave wave form with a
decreased resistive index and a delayed upstroke.
And centrally at the region of the anastomosis,
there is pre anastomotic velocity of 55
and post anastomotic of 400.

Hepatic Artery Pseudoaneurysm

This is much less common,
but can occur hepatic artery psal aneurysm.
It's the only example I actually have where you can see an abnormal cystic structure near the port of Hetus.
This one demonstrating a y yin yang pattern,
but the majority of the vessel was not easily found due
to overlying gas and due to the location
of the pseudo aneurysm.
But it was confirmed here with CT scanning.

Postoperative High Resistive Index in Hepatic Arteries

This is a somewhat common finding postoperatively on day one,
you may not see good diastolic flow to hepatic arteries.
And this can be seen due to edema,
maybe related to cold ischemia.
And you can see a very high resistive index
which actually is in this case is really one.
And this should be closely followed to establish
diastolic flow eventually occurring in the transplant.

So in this case, follow up still with a lack
of diastolic flow.
And then on day five, you can see restoration
of the normal hepatic arterial waveform pattern.
This again is usually due to edema in
or cold ischemia,
or may sometimes be related
to large collections pressing on the liver.
But either way these are closely followed
until the wave form appears normal.
And the one other thing that you wanna watch in this
situation is that the hepatic arterial velocities do not
trend down leading to eventual thrombosis.

Portal Vein Complications

This is a normal porter vein pattern.
You can see here a little bit of flow indicating
where the anastomosis was performed.
But do you have the same waveform pattern
associated with a native liver?

In this case,
we can see portal vein thrombosis
with echogenic thrombus filling the lumen of the portal vein
and absence of flow on the color doppler images.
And yet another example with partial thrombosis,
which is extending into the right and left portal veins
and partially occluding the lumen at the port of habitus.

Portal vein thrombosis affects one to 2% of transplants.
It's much less common,
but can be seen either due to excessive vessel length
or faulty technique, which we don't
really wanna put in our reports.
Patients may present with a hypercoagulable state
or if they've had previous portal vein surgery,
they may be at increased risk for thrombosis.
Clinically, this will present with findings
of portal hypertension.
The thrombus appears echogenic usually
or just inability to detect the portal vein
and presenting with lack of doppler.
Flow stenosis, on the other hand, will present
with focal aliasing.
And it's normal to have a little bit
of a stenosis at the anastomosis.
Sometimes there is a size mismatch
between the donor and the recipient.
But when there's a three
to fourfold increase in velocity relative
to the pres stenotic segment,
we get a little bit more concerned about stenosis,
and especially if the patient is presenting with symptoms
of portal hypertension,
We may want to make a comment on this.

And in this situation here, the portal vein,
you just see a lot of disturbed flow in this area,
some vibration.
And when the velocity is obtained,
you can see in the pre anastomotic segment,
the velocity is about 19 centimeters per second.
And in the region of the anastomosis it's up to 100
and 18.
And this patient was actually presenting
with some symptoms of portal hypertension necessitating
evaluation and treatment for the stenosis.

Hepatic Veins and Vena Cava Complications

Complications of hepatic veins
and vena ca cava are much less common.
In fact, less than 1% of liver transplant complications.
This may be due to technical factors,
especially in the early setting, either due
to size discrepancy or maybe in pediatric or in small
or split transplants.
There may be super hepatic cava kinking from organ rotation.
In the delayed setting. Stenosis can be seen related
to fibrosis in the region of anastomosis
or related to fibrosis or stenosis from chronic thrombosis.
Chronic cable stenosis is actually more common
after re-transplant, but is also more common in the
pediatric population.

Here's an example of the traditional
IVC anastomosis where you can see both the supra
and infra hepatic anastomotic sites.
It may present with some narrowing.
We don't really won't call this stenosis
unless it was causing abnormal waveforms
peripherally from this,
or symptoms such as lower extremity edema.

And this is an ex pictorial example
of a piggyback anastomosis where there is preservation
of the recipient vena cava.
Here you can see. And then the vena cava
of the graft is anastomosis in an end decide fashion
to the recipient vena cava.
At times the reci, the donor
or the graft stump
of the vena cava may thrombo over time.
But as long as drainage is preserved from the graft,
then this is an expected situation.

This patient, you can see an IVC
or stenosis, a stenosis at the anastomosis.
This is relatively rare, less than 1%.
Again, this more commonly occurs in Retrans plantation
and in the pediatric population
in the acute setting, it may be related
to a size discrepancy.
But you can see here that the hepatic veins
where they're joining into the IVC,
there is an abnormal color doppler picture.
And when velocities are obtained in the hepatic vein,
you can see that there is absence of the expected ity.
Further evaluation demonstrated a narrowing in the vena cava
with a greater than fourfold increase between the pre
and post anastomotic segment here at the stenosis
of velocity is up to 275 centimeters per second.
And then you can see distally in the vena cava
slow velocity and loss of ity
Thrombosis is uncommon, but can be seen after stenosis
or in the acute setting.
You can see here there's echogenic material filling The vena
cava flow could not be detected on both power and color.
Doppler and even with spectral doppler flow could not be confirmed.
And this is a case of IVC thrombosis.
Again, these complications are not common
but on occasion you may see them
stenosis we usually call again
after a three to four fold increase in velocity.
Sometimes you may see reverse flow
or absence of ity in the hepatic veins.

Gray Scale and Biliary Abnormalities

The focus of this talk is usually for a doppler
evaluation of transplants.
But I did include a few images for some gray scale abnormalities
or abnormalities of the biliary ducts.
And here you can see that there is dilatation
of the common bile duct
in here, which is indicated by the arrow.
And the identity
of the duct is confirmed on the color images,
where you can see the adjacent portal vein
and the hepatic artery, and then again, a dilated duct.

Now this can occur in up to 25% of transplants,
and 80% of them occur within the first six months
after transplantation.
This may result in biliary leak or stricter stones
or sludge and recurrent disease.
And Usually a leak may occur
at the site of ttu entry.

Perihepatic Collections

Collections can occur around the liver, usually at the,
they can occur near the diaphragm at the caval anastomosis,
but can occur anywhere around the periphery of the organ.
Hematoma is the most common,
which is the one I show here.
And you can see that there's echogenic material adjacent
to the liver with no flow on the Doppler images.
Hematomas can be followed over time where they tend
to evolve and become more hypo,
and then eventually an coic.

Summary of Liver Transplant Complications

As in summary, liver transplants can
present with collections.
Hepatic arteries may thrombosis or stenosis.
You may get portal vein thrombosis or stenosis.
Same type of complications can occur in the vena cava.
And then again, you may get biliary stenosis resulting in
biliary dilatation.
And one thing I didn't cover is you may get transplants in
the liver transplant or recurrent disease.

Renal Transplants

Now moving on to renal transplants.
This is actually a little bit faster
because the complications are similar,
just occurring in a different graft.
Renal transplant is the treatment of choice
for end stage liver disease.
And again, ultrasound is the imaging method of choice
for transplant evaluation and follow up.

The transplant may be placed in the right
or left lower quadrant
and are most commonly anastomosis
to the external iliac artery and vein.
The anastomosis is an endocyte side type variety
with a ureteral neo cystostomy.

Similar to liver transplants,
we wanna look at the gray scale appearance of the graft.
We wanna look for any peri transplant collections.
In addition, we wanna look at the collecting system
and then again, evaluate the renal arteries
and veins, both at the anastomosis and in the parenchyma.

Perinephric Fluid Collections in Renal Transplants

Just a few examples of perinephric fluid collections.
You may get hematomas, which will resolve over time.
Obviously you wanna check, especially in the setting
of fever, that these are not infected
and becoming abscesses.
Because the surgery is performed in the pelvis,
you may wanna worry about lymphic seals,
which occur a little bit farther out.
In the more acute setting,
omas are part of the differential.

Vascular Complications in Renal Transplants

Moving on to vascular complications.
This patient actually presented
with elevated creatinine.
And you can see here evaluation
of the arcuate vessels demonstrates a somewhat parvis tus
pattern, just as I showed earlier with hepatic transplants.
You can see the resistive index is decreased below 0.5
and further evaluation in near the anastomosis demonstrates
an elevation in the p systolic velocity
of the renal artery.
Pre anastomotic,
the velocity in the iliac artery is
106 centimeters per second.
And in the renal artery a little bit downstream,
you see a parvis tarus wave form with a delayed
acceleration.

Criteria we use is a velocity greater than two meters
per second or two to one velocity
gradient pre and post anastomotic or pre and post stenotic.
You may see focal color aliasing
on the color doppler images.
This is the most common vascular complication
of transplantation,
and it can occur in up to 10% of patients.
This usually occurs at the anastomosis,
but can occur at the clamp site due to crush injury to the vessel.
Tardis parvis is only variably present.
So if you have the velocity criteria met,
you may wanna call this diagnosis.
And again, you may see spectral broadening
or turbulence distally, just distal tooth the stenosis.

Here's one other example
where you can actually see morphologically
that there is a narrowing at the anastomosis.
The color images of normal
and the systolic velocity is 426 centimeters per second.

Renal Vein Thrombosis

Moving on.
Here is a patient who presented on day two
with pain over the graft And sudden oli uria.
Usually there is tenderness
and there is swelling of the graft.
And you can see in the renal artery,
there is an abnormal waveform with reversal
of flow during diastole.
Now, while this may be somewhat nonspecific,
the most important thing that you might wanna consider here
is renal vein thrombosis
which should be recognized early,
possibly if a thrombectomy can be performed,
then the graft can be saved.
And the causes of this include surgical technique,
maybe compression of the renal veins, either
by com collections, hematomas or omas
or hypovolemia with slower flow in the renal vein.
This can result in infarction
and a nephrectomy to prevent infection.
Oftentimes, the vein may be difficult to find
and it's the arterial waveform
with the reversed diastolic flow that could tip you off.
In this case you can see the renal artery
or the transplant artery is easily detected,
but the associated vein is not seen.
This is not that common.
But again, it's important to recognize this
abnormality early because you may salvage the graft

Arteriovenous Fistula

This patient presented after a transplant three years prior
and presented with abnormal brewery over the graft.
You can see here that there's an abnormal waveform
to the arcuate arteries
and arterial of the renal vein at the hilum.
Further imaging demonstrated an abnormal vascular
structure near the upper pole of this transplant.
And this is actually art tear venous fistula.
This can occur frequently in transplants
as a complication of biopsy.
But if large and it may spontaneously resolve
or thrombose, but if large marked AV shunting can result in
renal ischemia, and
you can only see these at times at Doppler,
but when large enough may present
as a cystic structure in the renal parenchyma.
And here you can see that when we
perform spectral doppler in this area,
you can see very high both systolic and diastolic velocities in the fistula.
Again, the most common cause of this is percutaneous biopsy
but can be occur occurring in the main renal artery
and vein due to surgery.

High Resistive Index in Renal Transplants

One of the parts of the renal transplant examination is
evaluation of the OID arteries.
In this case, we obtain a resistive index,
and we talked about low resistive index as an indication
of renal artery stenosis.
But you can also get an
abnormally high resistive index.
And in this case, there is no
diastolic flow to the transplant.
The resistive index is 1.0
and this is a pretty non-specific finding.
These patients usually present with
diminished renal function and the most common cause would
be a TN related to prolonged ischemia
or maybe reperfusion injury.
And this is the most common cause in the early setting
in the early and delayed setting.
This can be seen with rejection
and in the appropriate setting can be seen
with cyclosporine toxicity.
Other causes for a high resistive index may be related
to an obstruction or extrinsic collections.
And again, you can see here I listed all the
findings that I just discussed.
Extrinsic collections, compressing on the kidney,
an obstruction of the collecting system
or an abnormality within the graft parenchyma such
as rejection, acute tubular necrosis,
or drug nephrotoxicity.
Renal vein thrombosis can also present with this finding,
but as I showed earlier can also present with reversal of flow in diastole.

Renal Infarct

One other vascular complication includes infarct.
And you can see here in the gray scale image there is a
wedge-shaped area of abnormal echogenicity,
which does not demonstrate flow on the color.
Doppler compatible with infarct.
Infarct can be due to renal artery thrombosis
and maybe total or segmental due to vasculitis.
Patients may present with swelling
and tenderness over the graft.

Summary of Renal Transplant Complications

So I've gone over renal artery stenosis
and renal vein thrombosis, which are the two most common
transplant abnormalities
you can get AV fistulas from biopsies and infarct.

So I've just gone over the more common renal transplant abnormalities.
Renal artery thrombosis is not so common
and neither is renal vein stenosis,
but there was a suggestion
of a renal vein stenosis in this examination
where the velocity was abnormally increased
to 222 centimeters per second.
But in this case, there actually wasn't a focal stenosis,
but actually compression from one of the other known complications of renal transplantation.

Here we see a complex multi lobulated fluid collection,
which is most compatible with a lymphic seal.
And this collection was actually causing mass effect on the
renal vein causing these high velocities over a long segment.
And this collection was actually drained but did recur
and required multiple drainages.

Conclusion

And that ends my talk on both liver
and renal transplantation.
Thank you very much.