Liver Transplantation - HD

Introduction to Contrast Enhanced Ultrasound in Liver Transplantation

Let me introduce myself because I'm gonna do the next speak as a talk.

And what I'm gonna do very quickly is to show you why we use contrast enhanced ultrasound in liver transplantation.

We are the biggest liver transplant hospital in Europe.

It's not something that you should ignore liver transplantation because you're going to see one of these patients there are in between the years 1968, 2008, there are nearly 85,000 patients with a liver transplant.

So wherever your practices, even if it's not in a transplant center, you're going to actually come across these patients.

Guidelines and Applications of Contrast Enhanced Ultrasound

The FS m guidelines contain recommendations.

They're only a short set of recommendations.

So, but where you can use it, but if you look at where you using it, you really using it in areas where you can confirm that vascularity is present or absent.

And you're also looking at fluid collections, active breathing, bleeding infarction, and monitoring thrombolysis if you use it.

So they're very limited areas to use it, but it makes it quite a difference to your patient if you're using this because you can use contrast enhanced ultrasound at the bedside instead of transferring the patient further imaging.

Surgical Techniques in Liver Transplantation

Those of you're not familiar with the surgical techniques of liver transplantation.

These are quite important because this is the traditional surgical technique where you just cut something out, take the liver out, and replug it in exactly the same manner.

The problem with this is you'd have to clamp the IVC during the whole operation, which would take four or five hours, and this would increase patient morbidity because of the peripheral edema that would present itself more.

Now in adult transplantation, you'll get piggyback transplantation where you've actually preserved the IVC and you anastomose the hole of the transplant liver at one point to the IVC usually in the hepatic veins.

So that's what you'll be dealing with, important to know that.

But of course your surgeons won't tell you what sort of operation the patient's had on the request form.

You have to figure it out looking for the various options.

You can do a split liver transplant to two recipients from the donor liver and this becomes a little bit more problematic because of the bleeding and oozing a bile from the cut liver surface segmental reduction, this is something that you cut the liver down to to fit the patient.

This is for pediatric patient auxiliary transplant where you put a transplant on a disease liver that you're expecting to recover.

And now of course there's living related transplantation, usually the right lobe, but quite often you are doing the left lobe lobe as well.

Complications in Liver Transplantation

Where will the complications arise?

Well, if you divide it into vascular or nonvascular, it's only gonna be the hepatic artery, hepatic veins, and IVC or portal vein nonvascular complications.

Graft rejection is largely outta your hands, but ability biliary tract complications can be quite profound and may require re-transplant localized infections and miscellaneous vascular complications to the hepatic artery, thrombosis stenosis or pseudo aneurysm.

The portal vein, because it's bigger, it's stenosis or thrombosis, rarely do get a pseudo aneurysm and hepatic veins in IVCs against osis.

Hepatic Artery Complications

The hepatic artery after transplantation is crucial to the viability to transplant because it's the sole supply to the biliary system.

And if you lose the hepatic artery in an adult patient, you will eventually lose that hepatic graft from biliary epsis, et cetera in the child.

This may not be true because of usually a happy to go g ostomy is formed and there is lot of extra vascularity in that area, which you may get away from losing the transplant.

And if you don't see a hepatic artery on tra on ultrasound, usually you're going to do a multi detector CT or and angiography, but adding contrast may actually help you.

These figures are from old studies 'cause there are very few new studies done on transplantation, but hepatic artery thrombosis was estimated up to 12% in adults and in the smaller arteries in children up to 42%.

I would say these figures are much lower now with improved techniques and detection of imaging as well.

You will see that more often and of course if you delay the diagnosis liver a transplantation, it will occur.

Color DOP ultrasound is really very good at picking up the hepatic artery before the advent of color.

Doppler ultrasound, of course you had no idea what was going on with the patient unless you biopsied the patient because the presentation of hepatic artery thrombus is so non-specific.

It could be exactly the same as rejection, but color doppler ultrasound should see in normally 96% of the hepatic arteries.

So our practice here is you do on the liver failure unit at a dopplar sign at 24 hours.

Then day four, very often by day four, they can come down to the department and then just prior to discharge.

And if there's a normal recovery, there should be no problems there at all.

You may get a high resistance hepatic artery in severe hepatic edema, hypotension, or high grade hepatic stenosis.

And this is what the hepatic artery would look like in that liver.

This not, it is not necessarily a harboring a doom, but I very persistently high with the patient quite ill.

You may want to think about further management, particularly biopsy, and you're looking for the change of the high resistance to the lower resistance over a period of time.

So this is a patient from day one to day five, and it's improved considerably over that time.

So but you want to pick up hepatic artery thrombosis early so you can manage it with thrombolysis or revascularization quickly to save that liver.

The study we did looking at contrast in al ultrasound quite some time ago now was actually looking at just color dola flow, not the low mechanical index imaging.

And we could see the hepatic artery in 95.6% of those patients anyway before contrast, but this improved it to 98%.

It doesn't sound like very much, but it does make a big difference to the patient and management of the patients.

If you can almost get 100% sensitivity and specificity for this.

And only on one patient on angiography that we thought the hepatic artery was occluded.

It wasn't occluded, it was just very, very high resistance.

And these were the images we got and we were using in those days vis rather than vu to give you doppler rescue injecting the contrast and not seeing that artery at all confirmed on angiography.

Now we use low mechanical index imaging and you can pick up that hepatic artery quite clearly.

You follow the line of that hepatic artery and the imaging is much better, but you've got the arterial phase at the very beginning to see that hepatic artery on its own before you get the portal venous flow coming in and getting both enhancement together.

You can use flash imaging to burst all the bubbles and try and watch the hepatic artery separate from the portal vein coming in, but it can be difficult.

So you've got a very small window of opportunity to witness this.

And if I show you just an example of a patient that's done as a portable examination on the ITU, you can't really see on color doppler whether or not there's a pad artery patent.

It should be along that area.

But look at this, inject your contrast.

There's the aorta, celiac, axi, splenic artery, and you're absolutely sure that there's no hepatic artery there.

Management now is along a different pathway.

This patient can be revascularized immediately after the ultrasound examination.

The introduction of CT is has changed the management of hepatic artery thrombus because you can do this now very quickly and easily, but you need to transfer the patient down to the angio suite as opposed to what we did in the past.

Angiography, you can pick up collateralization around included hepatic artery, but this is the waveform that's quite a clue to whether or not you've got another complication of a transplant artery.

How can you use it in a practical manner?

Well, if you're doing a portable examination on the intensive care unit and you see a liver like this, eject contrast, and you can immediately tell them that no, there is no hepatic artery.

You can't see it.

There's a collection.

But more importantly, there is either collections, abscesses, or necrosis of that liver.

Hepatic artery stenosis is the next most common complication of the transplant artery.

And you the ideal scenario is to pick up that focus of high velocity in the hepatic artery, but often it's obscured by a number of factors in the postoperative patient, not least the number of surgical dressings that may be present.

What you look at for is the TARDIS parvis waveform, which I showed you a little bit earlier, which you are all very familiar with, looking for that acceleration time, the resistance index and the RI as it's called.

And if you've got a prolonged acceleration time and a low ri, you're likely to have hepatic art stenosis.

But a similar pattern can be seen in a number of other diseases associated with that.

This is a classic tardis par this way from the hepatic artery of this patient.

We looked at seeing whether or not we could use microbubble contrast to look at hepatic artery stenosis, a large number of patients over a couple of years.

And what we found was that even using contrast enhanced ultrasound, yes, you could pick up the areas of stenosis directly measure that area of stenosis.

And again, this is in the days of color doppler, but it was just as good to and here's one that you see with the low mechanical index imaging.

It was just as good to just pick out the tardis parvis to diagnose a hepatic artery stenosis.

So the adding contrast didn't really help you there, but it made you more confident it's actually detecting these the focus of the stenosis.

The other complication that can occur as hepatic artery, pseudo aism, it can be within the liver or outside the liver and outside the liver is associated with much higher frequency of death because it's usually associated with sepsis and fungal sepsis.

Again, we looked at our patients over a number of years, over a thousand liver transplants.

The incident's only about 1% nine at the site of anastomosis four intrahepatic 70% mortality with it and the management is choal embolization, but most of these patients will eventually require retrans plantation, and this is where contrast enhanced ultrasound can be more useful than in hepatic artery stenosis.

Just as some examples of pseudo aneurysms within the liver after a biopsy.

And it can be very slow flow in there.

The hepatic angiogram took a long time to fill that.

One up.

This is just a couple of cases with low mechanical index imaging.

This is a patient with CCI came in with patag artery with a small pseudo aneurysm.

This was then embolized.

These are the embolization coils, but there's still swirling of contrast in that pseudo aneurysm.

The patient goes back based on that, a further embolization rechecked with contrast enhanced ultrasound the next day.

And you can see it's gone from something like that to that to show you it's really embolized portal vein.

Portal Vein Complications

There are a lot of risk factors to portal vein complications, and most of them are to do with the premorbid existence of portal hypertension.

The portal vein is much bigger than the hepatic artery and less of a surgical challenge.

So less often you get portal vein stenosis.

But again, rather than just relying on velocity measurements, losing low mechanical index, you can delineate the degree of stenosis of the portal vein.

However, the portal vein is very flexible.

The stenosis need not always be treated and can be watched over a period of time looking for complications of portal hypertension.

What you're looking on colored op ultrasound is to look at the step up in velocity across that stenosis.

But in this patient with this such severe stenosis, this actually resolved over a period of one year.

IVC and Hepatic Vein Complications

IVAC stenosis is rare again because it's a big vessel.

Patag vein stenosis, more common thrombosis is very rare, but will occur with Bud Chiari.

And this is an image led to me by professor Pascal, showing you stenosis in the that piggyback anastomosis of the hepatic veins to the IVC and the narrowing there.

So you can make the diagnosis with more confidence using contrast.

Enhanced ultrasound, probably not needing to go on any other imaging.

Non-Vascular Complications

The nonvascular cal complications, the liver transplantation, graft rejection, blue tract, localized infection, graft rejection.

You get these multiple areas of focal stenosis through the hepatic artery, which are not amenable to blue angioplasty and quite often just requires treatment and possible retrans plantation.

If it gets too severe, you can pick up any evidence of biliary obstruction quite easily.

And biliary sepsis, which is abscesses forming around the biliary tree, which are not sites so evident on the on the beam mode ultrasound examination.

You can also pick up areas of focal infarction and focal biliary dilatation.

This is dilatation of the biliary tree in one segment of the liver secondary to a segmental infarction of the HEPA artery.

It delineates this more clearly than you do on the B mode ultrasound to allow you to make the diagnosis.

Other Complications and Uses

Other complications where you may use contrast enhanced ultrasound include abscesses and PTLD, post-transplant lymph disorder.

This is a patient only just come through the department a couple of weeks ago.

There is no hepatic artery, it's thrombo and he's developed biliary abscesses.

And the contrast enhanced ultrasound shows this clearly and there is some echogenic debris in there that's not vascularized, it's echogenic debris.

PTLD occurs more often in children bec and is associated with the EP Epstein bar virus.

And you'll find that these occur in many different organs.

The kidney, the liver, the bowel, the lymph nodes, and it's quite nice to make the diagnosis and it behaves exactly like lymphoma elsewhere.

And this is old imaging and this is in the spleen.

This is where we're using high mechanical index imaging to burst those bubbles.

But you get that characteristic feathery pattern that we've seen a little bit earlier on today in some of the presentations.

And this is a renal lymphoma in a patient.

And again, look at that appearance of that feathery pattern through that lesion almost characteristic of lymphoma seen elsewhere.

You can use it to in areas where you want to delineate not just the abscesses, but the fluids surrounding organs and pleural space to get a more confident visualization of what you're doing.

And this is the cut surface of that liver with a little bit of viable tissue there.

And this is a myeloma on the surface, you can see exactly what you're dealing with.

If you need to drain it, of course, you can use it under contrast enhanced ultrasound.

Conclusion

So there are limited areas of use of contrast in liver transplantation.

It's more a practical tool.

It's not a diagnostic tool, but it's certainly useful in thrombosis and areas of infarction and picking up complications within the abdomen and chest.

Thank you.