Evaluation of Renal, Liver and Pancreas Transplants - HD

Introduction

Good afternoon.

My name is Sheila Sheth.

I'm an associate professor of radiology at Johns Hopkins medical institution in Baltimore.

And my lecture this afternoon will be on vascular complications in renal liver and pancreatic transplants, role of ultrasound.

This afternoon we'll discuss the role of doppler ultrasound in the diagnosis of vascular complications of renal liver and pancreatic transplants.

And the objectives of this lecture is to discuss the diagnosis of vascular complications in this transplant, and we'll focus on complications that may significantly impact the health or survival of the transplants and emphasize potentially subtle findings and pitfalls.

And this will be a case-based discussion.

Renal Transplants

We'll first start with renal transplants, and in the last statistics in 2013, there were little under 17,000 renal transplants done in the United States, either cadaveric or living donor.

And we'll start with a normal appearance of renal transplant.

So on the gray scale, here's the renal transplant.

You can see there is good differentiation between the renal cortex here and the medullary pyramids.

We always ask the sonographers to get a good evaluation of the perfusion of the transplant.

And you can see on this power doppler there is very good perfusion of the transplant with small arteries going all the way to the renal cortex.

And finally, we do a doppler spectral assessment looking at the resistive index in the peripheral transplant artery.

The resistive index is the systolic velocity minus end diastolic velocity over the systolic velocity.

And as we quote it here, systolic velocity minus end diastolic velocity here in this particular case, the resistive index is within normal range at 0.74.

And basically what this resistive index measures is an impedance to flow in the peripheral of the transplant or resistance to flow.

And this will be abnormal in certain pathological conditions of the renal transplant.

Now to look at perfusion, should we look at power or should we look at color doppler?

And I would answer that I like both with power doppler measures the amplitude of the doppler signal.

You can see smaller vessels all the way to the point where these little branching cortical vessels, but you do not have direction of flow.

So on color doppler, you have direction of flow and you also have aliasing, and that's very important if you want to detect as this patient had in this case, arteriovenous fistula.

So I think they both play a complementary role.

And then we also measure, in addition to the resistive index I mentioned earlier, we measure the peak systolic velocity at the anastomosis between the iliac artery and the renal transplant artery.

This of course, should be angle corrected and you really need to, because now we measuring an absolute velocity value the velocity.

And so you want to keep your angle 60 degrees or below to have an accurate doppler reading.

And you simply measure the peak systolic velocity, which is normal here at 136 cm per second.

And we also evaluate flow within the main renal transplant vein.

So this is a normal renal transplant.

Case 1: Postoperative Day One After Cadaveric Renal Transplant

Let's start with our case number one, which is a 45-year-old woman who was postoperative day one after cadaveric renal transplant, and she had severe oliguria.

So right away when you look at the perfusion of this kidney as opposed to the normal I just showed you, you can notice right away that there is pruning of the little vessels here.

You do not see good perfusion all the way to the cortex.

The vascularity seems actually sparse.

And this is confirmed when we do the resistive index, you see that there is absolutely no forward flow diastole in the kidney, which is abnormal.

Normal renal transplant should have forward flow diastole.

And this patient has a resistive index of one.

So this means that there is tremendous resistance to flow in the capillary bed of the renal transplant, which is an indication that this transplant is not really functioning normally.

And since this patient is only one day post-op, the most likely diagnosis is that of severe acute tubular necrosis or ATN.

Now, an abnormal elevated resistive index is a resistive index above, at or above 0.8.

So between up to 0.75 is normal between 0.75, 0.8 in the gray zone, but definitely above 0.8 is abnormal.

And in fact, although I just showed you a case where we thought that the patient really had acute tubular necrosis, there is a wide differential diagnosis.

And so in addition to the abnormal resistive index, you need to put the history in context.

So within one day postoperative, the most likely diagnosis as I was the case in the previous patient is acute tubular necrosis.

After postoperative week one, there's a wider differential diagnosis, acute rejection can happen.

Acute rejection rarely happens within the first week post-op.

So acute rejection is definitely a strong consideration, but you can still have acute tubular necrosis, particularly the kidney had the transplanted kidney had a long cold ischemic situation before the kidney was transplanted.

Elevated resistive index can also be associated with calcineurin inhibitors toxicity polyomavirus, and that's commonly very severe hydronephrosis or pyelonephritis.

So in many cases, when the diagnosis is not clear based on clinical findings, and the patient will have a percutaneous renal transplant biopsy as was done in this case here to determine which of these conditions are responsible for the abnormally functioning kidney.

Case 2: Few Hours After Living Related Donor Renal Transplant

My next case is a 27-year-old man, which was only post-op a few hours after getting a living related donor renal transplant and the patient suddenly had severe oliguria.

So we look at, these slides are dark, but this was done in the ICU in not the best condition, but right away the striking thing is that both in the peripheral renal arteries as well as the main renal artery, there is actually reversal flow in diastole.

So not, it's not just with resistive index of one, but it's negative.

There is reversal flow in diastole.

Now this is a critical finding.

If you see reversal flow in the transplant artery, this is really an important, potentially very dangerous finding for this transplant.

And so the first thing we need to do is look for the renal vein.

That's very, very important because one of the underlying causes of having reversal flow in diastole in the artery is that the renal vein is thrombosed.

And in this patient you can see here that there is flow towards the transducer.

So this flow in the arterial system, we were never able to find the renal vein.

So our diagnosis was a thrombosed transplant renal vein.

This is a condition where you pick up the phone, call the transplant team right away, and the patient had an emergency surgery and unfortunately had to undergo transplant nephrectomy.

So reversal flow in diastole in the renal arteries, a dire situation, which requires immediate notification of the transplant team.

It requires urgent management, in one series of over 5,000 ultrasounds done was present in this article here in 1.2 percent of studies.

And the first thing you do is look at the renal vein because one of the conditions causing reversal flow in diastole is a thrombosis of the transplant vein.

Transplant vein thrombosis is a potentially catastrophic complication seen in about 0.4 to 4% of cases.

And because the transplant lacks collateral venous circulation, then the transplant is at risk for having necrosis.

You can have an it can be resulting from a complication.

Usually this occurs within 24 to 48 hours postoperative.

And it's important that this patient be taken emergently to surgery because potentially, there is a possibility to do a venous thrombectomy and save the transplant.

But you can also have delayed renal transplant vein thrombosis several weeks or days after the transplant.

And that is thought to be caused by severe vasculitis likely secondary to severe acute rejection.

And in this case, unfortunately it is usually not a reversible cause and most of these patients end up having a transplant nephrectomy.

We also have to be aware that a very severe venous kink sometimes can have similar doppler findings and mimic thrombosis.

Case 3: Postoperative Day One After Cadaveric Renal Transplant

Now this is my case number three.

This was a 40-year-old man post-op day one after cadaveric renal transplant where severe pain over the transplant site and anuria.

So here's the transplant.

And really if you look quickly, there is not really a significant abnormality, but if you look at the clip here, and I'm gonna play it again, you can see that the transplant really is not all the way here, right?

The vascularity, which seems pretty good in the transplant stops here.

So what is this?

So this is actually a hematoma, and again, the still picture confirms it.

There was actually good perfusion to the transplant, as you can see here.

And this perinephric soft tissue space was basically a hematoma.

The patient did have reversal flow in the main renal artery here, but we looked for the renal vein and which actually we could actually find the renal vein here.

So in this patient, the reversal flow in diastole in the arterial system was not caused by renal vein thrombosis, but was caused by a perinephric hematoma.

Again, this is a critical finding.

The patient had a quick CT scan, non-contrast CT scan confirming that the patient had subcapsular hyperdense fluid collection compatible with a recent hematoma.

Here, the patient underwent emergent surgical evacuation of the hematoma and on the surgical table had larger output and basically the transplant improved very, very quickly.

So there is a differential diagnosis for reverse diastolic flow.

Really the differential diagnosis depends on timing.

As I said before, in the early postoperative period, 24 to 48 hours.

The two things you really have to watch out for is renal vein thrombosis, which is the most common thing that I've observed, but also potentially hematoma with page kidney as we saw in the second case.

And occasionally if you have very severe rejection or ATN, well prob not severe rejection, actually ATN very severe.

Occasionally it can cause reversal of flow in diastole, but that's uncommon.

And then within a one month post-op, or delayed occurrence, this will be a slightly different diagnosis and I'll show you examples of that.

Unless there is a treatable surgical condition, having reversed diastolic flow in the arterial system of the renal transplant is a poor prognostic sign with about 33 to 35% graft loss reported in the literature.

So if you look at this situation, not immediately post-op, but within a month post-op, then it could be caused by acute tubular necrosis, acute rejection or delayed transplant vein thrombosis.

And then after a month post-op, then other conditions causing reversal diastolic flow include severe rejection glomerulosclerosis in the transplant or low cardiac output.

Again, remember however that this is a relatively poor prognostic sign for the life of this transplant.

And this is just an example of patient that was 10 days post-op.

You can see here that the kidney looks kind of edematous.

There is loss of the normal corticomedullary differentiation.

You don't see the renal sinus fat very well.

You have reversal flow in the arterial system in diastole here in the main renal artery.

And you look at the renal vein and there is good flow in the renal vein.

And this patient underwent a biopsy and had severe acute rejection.

Case 4: Elevated Velocity in Transplant Vein

Now, in some cases, the vein is the transplant vein is patent, but there is elevated velocity in the transplant vein, as you can see here.

So normally the vein, this is a transplant vein here, the velocity is 21 cm per second, which is way too high.

It should be no more than 40 to 50 cm per second.

And there are several, there's a differential diagnosis for this condition.

If it's in early in the postoperative period, it could simply be postoperative edema and this will resolve on its own or it could be a kink or as was the case in this particular patient, a severe stenosis.

And here I have the MR to prove it.

This is a renal transplant with a transplant vein here.

Here's the iliac vein.

And you can see that this segment of the vein here between the renal hilar region and the iliac vein here, this segment of the renal transplant is severely stenosed and hence the very elevated velocity.

Case 5: Nine Months After Renal Transplant

So my next case now is a 38-year-old woman who had a renal transplant nine months prior to this scan, had a rising creatinine and had hypertension that was difficult to control by medication.

So let's look at her case.

So here's her renal transplant, here's the iliac artery.

And you can see here this is the main renal vein to the transplant, and you could see aliasing.

So let us see what is going on here by putting a doppler spectrum.

And we, when we look at the area of the anastomosis here, we have a very high velocity of 467.5 cm per second.

So that's very high.

And if we look at the iliac artery before the anastomosis here, the velocity is 138.4 cm per second.

So we suspect here that the patient had renal artery stenosis in the renal transplant artery.

So this has been, this complication has been reported in one to 16% of patients.

Clinically, they present just like our present patient presented with worsening renal function and hypertension.

You use color doppler to identify the area of aliasing and you need to have the doppler spectrum just as was a case in the case I just showed you for diagnosis.

The criteria, there are not that many published papers, but they're basically similar to what you would do for the native kidney.

And we use a peak systolic velocity in the main renal artery above 200 to 250 cm per second combined with a systolic velocity ratio between the renal artery and the iliac artery above two to 3.5.

These are variable numbers reported in literature.

If there is any question, I think it's a good idea to get an MRA if possible, particularly if the patient has appropriate symptoms.

So if you have an elevated systolic velocity in the main renal artery for transplant, what is your diagnosis?

Where it could be, again, very early postoperatively, could be simply postoperative edema.

But you think about renal artery stenosis, you can also have a kink in the renal artery.

So it's not an anatomic stenosis, but the artery is just kinked or a size mismatch between a small donor artery and a larger recipient artery.

Other vascular complications are perhaps less common.

You can have complete thrombosis of the transplant artery or focal infarction.

This is a patient, if you look at the transplant here, you can see that even on gray scale, this portion of the transplant has a different echo texture than the bottom two third here, when we put with perfusion, you can see that there is no perfusion to this upper pole transplant.

And this is a focal infarction of the upper pole.

A more obvious case here, the patient, this patient had two kidneys transplanted next to each other.

And when we put color doppler here, we can see that there is flow in the left transplant, no flow in the right transplant.

So again, this is a critical finding, where we suspect that there is arterial thrombosis here because there is no flow whatsoever.

And this patient ended up having the right transplant removed, because there was no arterial flow confirmed on doppler during the surgical procedure.

And the right transplant was necrotic.

Case 6: Gross Hematuria After Renal Transplant Biopsy

Alright, so my next case now, case five, is a 44-year-old woman who had gross hematuria after a renal transplant biopsy.

So if we look at the gray scale, if the patient has a little bit of hydronephrosis, otherwise the transplant looks, the cortex looks normal.

We put the color doppler here, and you can see that there is this very large vessel going to the periphery here.

And then the key here is to put doppler spectral interrogation.

And you can see here that there is a color bruit in that area.

So there's tissue vibration, there is very high turbulent flow in that region.

And the patient does have an arteriovenous fistula, a large one for that matter.

And because of that, the patient underwent angiogram.

And there was, you can see the early draining vein here.

So this is an arteriovenous fistula post biopsy complication or arteriovenous fistula, actually not uncommon, iatrogenic, when the biopsy needle pierces the arterial and the venous wall during the biopsy procedures, many are asymptomatic and resolved spontaneously.

If they are large, like the one I just showed you, they may need intervention.

Other complications include post biopsy hematoma.

And here what we have to try to look with power doppler is look for an active extravasation or an expanding hematoma.

And then less commonly we have seen pseudoaneurysms either isolated or associated with an arteriovenous fistula.

So let's look at a couple of those examples.

Here's a patient who had a biopsy in the morning, the transplant is here, had abdominal pain, and was dropping hematocrit a little bit later in the afternoon.

So you can see now that there is this big echogenic collection superior to the transplant.

And at color doppler, you could see there is what a little kind of bleeder right there, or suspected bleeder.

And then this patient here, on the gray scale, you can see there is a cystic structure in the cortex of the transplant.

Very easy diagnosis.

By pushing the color button, you can see that this fills in and there is a yin yang.

So this part is a pseudoaneurysm.

There's also aliasing in that area.

So maybe with doppler spectrum, we can see a little bit what's going on here.

And basically the patient had a pseudoaneurysm.

And you can see, again, I'll show you the yin yang sign, but usually simple pseudoaneurysm would not have a turbulent flow, but there was also turbulent flow.

Okay?

So what basically this patient had, and you can see nicely at the angiogram there, this is an arterial phase study.

So you can see here the large feeding vessel, the pseudoaneurysm, and then the early draining vein.

So this patient had a combination of a pseudoaneurysm and an arteriovenous fistula.

And these of course, usually need to be treated, embolized by angiography.

Here's another patient.

The transplant perfusion here looks normal.

The patient had increased creatinine hematuria.

So every time a patient has hematuria, make sure that you put the doppler over the entire kidney to detect the small arteriovenous fistula who could potentially cause hematuria.

And so something's interesting in this patient because if we look at the mid pole doppler spectrum, the resistive index is one, there is no diastolic flow, so that's abnormal.

But if you look at the lower pole here, the vessel's a little bit more prominent and there is a continuous forward flow in diastole suggesting that the flow is actually turbulent.

So what is going on?

Well, we look a little bit more careful, and what happened is that the patient does have an arteriovenous fistula.

Here's the nicely shown large draining vein here.

And that was the explanation for the focal turbulent flow in the lower pole.

And at biopsy, the patient had drug toxicity, which explained the high resistive index, but also had an arteriovenous fistula.

Liver Transplants

Okay, so now we'll switch organs and we'll talk about liver transplants.

Now, approximately 6,000 liver transplants are done per year.

Vast majority, at least at our institution are cadaveric.

But more and more because of the short supply of cadaveric liver transplants, living related transplant becomes an option in some patients.

And so before, so this, I'm gonna talk about cadaveric liver transplant anatomy here.

And I just want to show a diagram, and I'm grateful to Platt and Larso where I could borrow this diagram here and look at the vascular anastomosis.

So when the liver is transplanted, there are three vascular anastomosis, the portal vein anastomosis, the IVC anastomosis.

And depending on the way that the liver is transplanted back, you can have two anastomosis or a piggyback anastomosis where there is only one venous anastomosis for the IVC.

And very importantly, because that's the one that creates the most common complications, the arterial anastomosis of the between the recipient and the donor hepatic artery.

And then of course there's a bile duct anastomosis as well.

But we're not going to be as concerned about this today.

So this is a normal doppler spectral evaluation of the liver transplant.

So we look for a main portal venous flow, and oftentimes, especially early in surgery, the velocity may be a little high.

This is about 46 cm per second.

It's okay.

We look at the hepatic artery and the easiest place to find the hepatic artery, of course, in the region of the porta hepatis.

But if you can try to trace it more proximally, try to find at least a portion of the extrahepatic hepatic artery possible, and you should have some forward flowing diastole.

And then we'll look at flow within the inferior cava and flow in the hepatic veins.

And so this is a normal examination.

Now this is just an example of a piggyback where basically there is more back table preparation of the liver, but in the piggyback anastomosis, the donor IVC is anastomosis usually a side to side anastomosis with the recipient IVC.

And this is what it looks like.

And the advantage here is that there is only one IVC anastomosis.

So this is a piggyback configuration.

Case: Postoperative Day One After Liver Transplant

So let's start with this case of a 29-year-old woman, who was post-op day one after liver transplant, had abnormal liver function test and was acidotic, so not doing well.

So here, when we try to find the hepatic artery, you can see there is nice flow in the portal vein here.

We could not really find flow in the hepatic artery.

So we tried to look more centrally and there was just maybe a little bit of flow here in the hepatic artery.

Very, very difficult to find.

So, but we were unable to find flow in the more distal or towards the liver, a portion of the hepatic artery.

So this is a critical finding, no flow in the hepatic artery.

And basically the patient underwent an emergency hepatic artery thrombectomy, and unfortunately this was unsuccessful and she required retransplantation.

So hepatic artery thrombosis and stenosis are the most common and the most serious vascular complication after liver transplant.

If it's an acute phenomenon, then there is risk of septicemia, gangrene into the liver and the patient will need retransplantation or will die.

If it's a more gradual process, then because the hepatic artery is the only vascular arterial supply to the biliary system, there's a high risk of biliary ischemia.

Now remember the liver has a dual inflow system, portal venous as well as hepatic artery, but the biliary system only has the hepatic artery as its arterial supply.

And so if there is delayed thrombosis or stenosis, you have biliary ischemia.

And this is a complication that affects approximately 7 to 13% of patients who had a liver transplant.

Now hepatic artery thrombosis.

So complete thrombosis account for about 60% of all vascular complications.

The liver transplant, it's more common in the pediatric patient.

It's a catastrophic complication.

If it's in the immediate postoperative period, these patients have fever and sepsis, gangrene to the liver and may die without retransplantation.

But you can also have delayed hepatic artery thrombosis where there is some small amount of collateral flow, which is not sufficient to maintain a healthy biliary system.

But has some hepatic arterial peripheral flow.

And so these patients present usually with recurrent sepsis, liver abscesses, biliary leaks, and ischemic cholangitis.

So this is a patient who had a liver transplant six months prior, was doing okay, and then presented with right upper quadrant pain and fevers.

And so the first thing we see on these two gray scale images is the patient has a lesion here, which has some cystic areas here, maybe another lesion here.

And in a patient who has septic, of course you think about hepatic abscesses.

And so then we looked for her hepatic artery, and here there is some flow in the hepatic artery.

Okay, so in the region of the porta hepatis, we do see flow in the hepatic artery.

But notice two things.

The systolic upstroke here is not sharp, it's there's an increased slope.

And this is a parvus tardus type phenomenon.

And also the resistive index is too low, below 0.5 is abnormal, so there's too much diastolic flow.

And so that's a kind of an indirect indication that perhaps there is a problem in the more proximal portion of the hepatic artery.

So if you see a doppler spectrum like that parvus tardus appearance, a low resistive index, you need to trace the hepatic artery more proximally.

And when we did that in this patient, here's the aorta, the celiac axis, the splenic artery, and there is no hepatic artery.

So there was an occlusion near the origin of the hepatic artery.

And so this patient had what's called collateral transformation of the hepatic artery.

This patient did undergo angiogram, and you can see here that there is an occlusion near the origin of the hepatic artery from the celiac axis.

But you see this irregular kind of small neo vessels in the porta hepatis.

And this is why when there is delayed hepatic artery thrombosis, you have some hepatic arterial flow in the porta hepatis region.

And that's been called the collateral transformation of the hepatic artery.

So it's important to realize that in hepatic artery thrombosis, the presence of arterial flow in the porta hepatis does not exclude the diagnosis of hepatic artery thrombosis.

Okay, again, this parvus tardus type pattern in the porta hepatis is abnormal.

So you have an abnormal doppler spectrum with a low resistive index below 0.5 and the tardus parvus appearance.

And if you see that, you need to trace a hepatic artery more proximally from its origin to the celiac axis.

And in patients who have a liver transplant have repeated liver abscesses or bilomas or cholangitis, you have to maintain a high index of suspicion for this condition.

Now this is another patient who had fever, abnormal liver function test three months post-op.

And here you can see that there is this was a hepatic artery tracing in December, 2009.

And you can see that there is very little flow here in the hepatic artery.

This is all venous flow here.

And then follow up a couple months later, we can't find the hepatic artery at all.

So this was an abnormal doppler spectrum here.

Couple months later, we can't find the hepatic artery.

There is still some flow in the liver because the portal vein is patent, but this patient had this large amount of gas in the liver here.

And on the CT scan, you see nicely that there is a large necrotic area with a large abscess or necrosis caused by delayed hepatic artery thrombosis.

And again, this was confirmed on this patient's CT scan.

Here's the celiac axis and nicely shown on this MIP image.

Here you have the splenic artery and there is no hepatic artery.

This is another patient who presented several months after liver transplant.

Very similar findings of abnormal liver function tests and fevers.

And again, very similar pattern.

There is this gas formation in the liver.

So we are worried about an abscess.

When we looked at the porta hepatis you now can recognize the parvus tardus appearance and the low resistive index below 0.5 in this patient.

So we are going to trace the hepatic artery more proximally because we're suspecting that the patient has a problem with the hepatic artery.

And in this case, here's the celiac axis, we can see the origin of the hepatic artery.

But you can see here that there is an area of narrowing with a waist type appearance.

And in that area you can see that there is very high peak systolic velocity, probably above 326 cm per second.

Okay, so this patient had a stenosis in the hepatic artery causing very similar symptoms in the patients.

And again, nice correlation between the ultrasound here with the area of stenosis.

And this is the angiogram at the time of balloon angioplasty.

You can see here there's a focal significant narrowing of the hepatic artery.

And this patient was treated with balloon angioplasty.

So hepatic artery stenosis has a clinical presentation that is similar to delayed hepatic artery thrombosis.

It's occurs in about 11% of patients or liver transplant recipients.

And again, they're the same doppler findings as hepatic artery delayed thrombosis with resistive index less than 0.5, and a parvus tardus phenomenon and more proximally.

If you're lucky, you can find the area of stenosis with a focal elevated systolic velocity above 200 to 300 cm per second.

Now, Dr. Haro from Albert Einstein in Philadelphia gave me this case.

Some of the patients who have hepatic artery stenosis have a complication of biliary casts.

What happens is that they have ischemia of the biliary wall and necrosis of the biliary wall, and then this cast formation, this echogenic, the bile duct is basically filled with this echogenic material.

So hepatic artery stenosis with biliary casts.

What are the potential pitfalls in this diagnosis?

Were, first of all, potential false negatives as I showed you.

And again, remember, the presence of hepatic arterial flow in the porta hepatis does not exclude thrombosis or stenosis, potential false positives, severe postop edema in the early postoperative period.

So the thing is, in a patient who has sepsis or abscesses, just think about this condition.

Okay?

Think about it.

And then I want to talk a little bit about the syndrome of impending hepatic artery thrombosis.

And this was an article published several years ago now, who discussed the sequential doppler of the hepatic artery shows loss of diastolic flow in hepatic artery, dampened systolic flow, and then a few days later, it's followed by complete loss of hepatic arterial flow.

So the syndrome of impending hepatic artery thrombosis.

So here's an example.

Post-op day one, there is a little bit of hepatic arterial flow.

You can see, first of all, it's very low.

The velocity is extremely low here, probably like 20 or 30 cm per second.

There is no diastolic flow.

So we would recommend very careful follow up of this patient, because this is, this potentially could have a thrombosis of the hepatic artery.

And sure enough, two days later, the patient was not doing well.

We bring the patient back.

And at this time, even with power doppler, we can't find the hepatic artery.

So again, this patient unfortunately had a hepatic artery thrombosis, hepatic necrosis, and had to go emergency retransplantation.

The caveat is that some of these patients are on pressors for hypotension, and if you're on vasopressors, then you may not have forward diastole that's just a function of the medication they're on.

So if I see no forward flowing diastole early postoperative period, always call the ICU and find out if the patient's on pressors, because that, you know, in these patients, it could be a good explanation without having to invoke an impending thrombosis.

Regardless, I think it's a good idea to have careful follow up in these patients.

Now, portal vein complications in liver transplants are less common and are less catastrophic.

They represent one to 2.7% of vascular complications.

They're more common in living donor liver transplants.

And the complications include portal vein thrombosis, stenosis, either at the anastomosis, usually at the anastomosis with a velocity gradient, or you can have a portal venous aneurysm.

And this is just an example of a patient who had a lobe of the liver donated by a living donor.

You can see in the portal vein, which is patent, there is an aliasing with very high focal elevated velocity of 121.7 cm per second.

So this is a portal vein stenosis.

Hepatic venous complications are also relatively uncommon.

They represent two to 10% of vascular complications.

You can have hepatic vein or IVC thrombosis, or you can have a partial clot you can see in this patient, or you can have stenosis at the anastomosis you'll see a velocity gradient.

And again, these complications are more common probably cause the surgery, the surgery is more technically difficult in patients who have a living donor.

And this is an example of hepatic venous stenosis.

Now, you can see here right away what is abnormal is that the hepatic veins should really drain towards the IVC.

This is a transverse view of the liver, so they should be away from the transducer and blue.

And you can see here in this middle hepatic vein that the flow here is reversed.

It's going towards the transducer, which obviously is abnormal.

And then you can see again aliasing in the right hepatic vein as well.

And the patient had an area stenosis here near the IVC anastomosis and was treated with angioplasty.

Pancreatic Transplants

Okay, and the last organ I'm gonna discuss is a pancreatic transplant.

About 800 pancreatic transplants were done in 2012 in the United States.

800 combined renal and pancreatic transplants and maybe about 450 pancreatic transplants alone.

They tend to be diabetic patients.

And basically, so the transplants, usually they also have renal failure.

So they get a renal transplant for the renal failure in the pancreatic transplant for the islet cell endocrine pancreas.

So there are two different surgical techniques.

The one that is used most commonly at our institution.

The pancreatic transplant is transplanted in the iliac fossa.

So it will have a systemic vascular drainage, and the vascular anastomosis will be done with the iliac vessels.

And remember, it's important to have an exocrine drainage of the pancreas as well.

And the drainage is done in the bladder more commonly than in the bowel.

And then there is also another technique that's been described, portal enteric drainage where the pancreas stays in its anatomic location.

So it's higher in the abdomen.

The venous drainage is in the SMV and the exocrine pancreas of the transplant is drained in the small bowel.

So this is again, courtesy of University of Minnesota diagram of the pancreatic transplant, which is draining in the systemic circulation in the iliac fossa.

So here's a transplant here you have the vein here, draining in iliac vein.

And the SMA and celiac type vessel is taken from the pancreas, from the donor, and it's grafted in the iliac artery of the recipient.

And there is the splenic vein and SDV are tied off here.

And then there is a piece of jejunum connecting the pancreatic transplant to the bladder for the exocrine drainage.

And the advantage of this also is that if you want to assess the health of the pancreatic transplant, you can measure the amylase in the urine.

And if the amylase drops, it means that perhaps a pancreatic transplant is not functioning properly.

So this is a normal pancreatic transplant in gray scale.

Maybe a little challenging sometimes to find them, but basically just looks like a pancreas.

Okay, this is in the iliac fossa, and you want to look for good vascularity within the transplant here.

And you want to look at the venous anastomosis between the portal vein and the iliac vein here.

Nice venous flow.

And usually there are two arteries, one which has more of an SMA type flow with higher resistance.

And the second one, which has more like a celiac axis type flow with lower resistance.

So you look for one venous doppler signal and two different arterial doppler signals.

So this is a normal case.

Case: One Day After Pancreatic Transplant

Now, this patient was a 50 year old man with a pancreatic transplant one day prior and had increasing insulin requirement.

So if we look at the transplant here, there is some perfusion here, but we couldn't find the portal vein.

And we were wondering, is that the area of the pancreatic vein, is it expanded?

Is there a clot?

And then when we look at the arterial doppler, you can see again the dreaded reversal of flow in diastole here.

So just like in the kidney, you have to concern that there is very high resistance, something's going on.

And combined with this finding, we're suspecting that the patient had no flow in the pancreatic transplant vein, and the vein was actually thrombosed, and the patient did undergo an emergency thrombectomy.

So what are the complications?

Vascular complications are found in two to 19% of cases.

And biochemical markers are very important to detect graft dysfunction.

As I mentioned, one of the ways to do it is to measure the amylase in the patient's urine.

They also are prone to other complications including graft rejection, pancreatitis, and fluid collections.

Conclusion

So in conclusion then, there are many challenges to be met when we evaluate a vascular complication of transplants.

You need to know the surgical technique.

You need to be able to interpret the doppler parameters, and they vary with a type of organ transplant.

So it's gonna be very different what you're looking for in a liver versus a renal transplant.

And so what I would suggest is that you get as much clinical information as possible if you can look at the postoperative note or talk to the surgeons, we need a meticulous scanning technique.

And to remember all this numbers, I recommend you have a cheat sheet either online or in the reading room to remember the numbers and the criteria.

And again, another challenge that I should mention, that especially early on, these patients are done in the ICU, they're very sick, and the image quality is also sometimes challenging.

So, but I hope that I've helped you look at some of the complications and how to deal with them.

And I thank you very much for your attention.