Contrast Enhanced Ultrasound in the Abdomen: Liver and Kidneys - HD

Introduction

Hello, I'm Dr. Ed Grant, and I'm from the University of Southern California Department of Radiology.

Today I'm going to be giving a talk on contrast ultrasound of the liver and kidneys.

I'm going to be talking about contrast enhanced ultrasound in the abdomen with specific attention to the liver and to its use in the liver and kidneys.

Basic Principles of Contrast Agents

Just by way of background, some basic principles about contrast agents in general.

The reason that we actually use contrast agents of various types or of any type for that matter, is to change the property of a specific structure with regard to the surrounding tissue such that it stands out better or in fact we are able to see it at all.

One of the other important principles of contrast agents is the fact that they tend to increase the signal to noise ratio of the specific structure that we're looking to image.

We do this using various compounds.

Typically in x-ray or ct, we want to increase the density of the structure we'd like to see, in which case we often use iodinated or barium filled compounds.

In Mr we do this, we increase the signal to noise ratio by increasing the amount of magnetic signal typically used in some sort of iron containing compounds such as gadolinium and with ultrasound.

This is done by the use of air bubbles, which also of course are very highly reflective.

Now, air bubbles were used originally at this point we have more sophisticated contrast agents, so these are really microbubbles of various types.

Typically at this point, with the more modern agents, those would be using fluorocarbon bubbles and we'll talk more about that later.

Whenever you're going to inject a contrast agent, of course one should be thinking in terms of the amount of toxicity that it may cause versus of course, the benefit that it provides with regard to imaging of the patient.

As I mentioned, there are various agents that have been used for many years in imaging, for outlining the hollow viscous.

For example, the bowel.

Typically we use barium.

In ct, sometimes water can be a successful contrast agent, methylcellulose, or even bubbles to put gas into the area, for example, of the stomach.

Use of Contrast Agents in Cross-Sectional Imaging

When I think in terms of the use of contrast agents, with ultrasound or for that matter with most other forms of cross-sectional imaging, I usually think in terms of intravascular injections, and some of them will outline the macrovascular, the large vessels.

For this, we would be thinking in terms of the prototype, say of contrast, classic contrast angiography.

In the last decade or so, we've taken that to other heights using it as MRM RA or CT angiography, or now with ultrasound contrast as well, we can see the large vessels enhancing nicely after injection of these microbubble contrast agents.

This can be contrasted with what I call microvascular or parenchymal imaging where the vessels themselves are not typically individually seen, but rather you have enhancement of the entirety say of an organ such as the liver or the kidney.

This has been done again for many years with, intravenous graphy, CT or mr.

And of course ultrasound can do the same as well.

Do keep in mind that with CT and MR and the eye, with the contrast agents that are typically used with those forms of imaging, you do have a vascular and also, an interstitial phase such that these contrast agents actually, will, diffuse out into the interstitium, outside of the blood vessels themselves.

Remember that the ultrasound contrast agents, because they are microbubbles, are really pure blood p pool agents.

They do not actually, get outside of the blood vessels themselves.

One of the, advantages of ultrasound that is not enjoyed by CT or MR of course, is the fact that ultrasound is a real time imaging technique that provides a continuous display of the structures being evaluated, from the moment it's injected until the moment you stop scanning.

Physics of Contrast Ultrasound

Some basic physics about contrast ultrasound, as I mentioned earlier, gas or air of any kind is a strong sound reflector when it comes to the body because it's extremely different from the tissues of the body itself.

So again, we're increasing the back scatter or the amount of signal going back to the transducer from areas that have high concentration of these microbubbles.

Thinking in terms of physics, the amount of reflectivity of a structure is directly proportional to the size of the scatterer, the density of the scatterer and the compressibility in this case of the gas, do remember that if you put too much of a contrast agent into the patient, it may reflect so much sound that you actually have degradation of the area behind it, secondary to shadowing.

Requirements for Contrast Agents

Now, when would we use the well things that would make a contrast agent possible or one that you would want to use?

First of all, it needs to be injected through an easy IV access site.

Most of the time we inject these contrast agents through an arm vein, just an arm or hand vein, just as we would with IV contrast for CT or mr.

Remember that if you inject from an intravenous access site that in order to see tumors for the most part and other structures that we're usually interested in, these agents have to pass through the pulmonary vasculature and into the systemic circulation.

If we're actually going to be able to get adequate arterial or parenchymal imaging, for this reason, they must be small enough.

The microbubbles must be small enough to pass through the spongy, filter that is the lung.

And having consistently small particle size generally in the case of modern agents about the size of red blood cells is absolutely essential.

Remember, the agents must remain intact for a sufficient amount of time to be able to actually scan.

So in addition to using, the microbubbles themselves, typically the more modern agents, use a stabilizing shell.

Typically this will be consistent of lipid or some form of surfactant.

Other compounds such as, albumin, have been used as well.

As I mentioned, we are no longer using, typical air bubbles, for our contrast agents.

Most of the contrast agents that are currently in use, rely on perfluorocarbon gases.

And the reason for this is that this type of gas is not soluble in blood, again, increasing the amount of time, before it goes into solution and is no longer visible.

All this is aimed, of course, at providing a realistic amount of scan time, so that you can actually see the imaging or see the structure that you want to image.

And of course, you also don't want really too much because if it's a relatively short period of time, you can actually re-inject if you have any other questions.

Or for example, if you'd like to target a second or third lesion.

The major advantage really, or one of the major advantages of most contrast agents that are currently in use, if, if really all of them, is the fact that these agents are not nephrotoxic, the gases break down, in the bloodstream and they're simply excreted in the form of a gas through the lungs.

And so this is a major advantage over, iodinated contrast agents.

And to date, millions of these scans have been performed around the world.

And, again, there's no obvious evidence or no evidence to suggest that there may be a problem as occurred with Mr. Contrast where, systemic sclerosis became, a possible complication of injecting these contrast agents.

Although these are not approved in the United States for use outside of the heart, which is not a subject I want to go into, but hopefully will end soon and be more readily available or more readily usable in the United States, one can get reimbursed for these by most insurance, companies.

And in fact, there is even a specific code that we use, which is Q 9 9 5 7.

Specific Contrast Agents

At this point there have been a number of contrast agents on the market.

Many of them have gone by the wayside.

The older ones Alx, and Levo Vistas, again were micro air microbubbles, and they had albumin and galactose as their carriers stabilizing.

Kogen was one of the first of the, perfluorocarbon gases, to be used as an agent.

Again, no longer available.

Optisan and Definity are both available in the United States and are FDA approved for cardiac use only, although off-label use, again, is not a problem in my opinion.

In the United States, if it's medically indicated, Optisan again uses albumin.

Definity uses a lipid surfactant, stabilizer or carrier.

Probably the most widely used worldwide agent is sono view.

Again, this is a sulfur hexa fluoride compound using lipid and surfactant.

Again, the idea of the sulfur hexafluoride, the fluoride compounds are not soluble in blood and therefore, maintain stability of the agent.

Another interesting agent is known as Sona.

The interesting property of Sona is the fact that it provides the typical vascular phases of imaging that we need, but it is also taken up by the reticular endothelial cells of the liver.

And therefore, abnormal areas such as metastasis, hepatocellular carcinoma will be seen as hull or defect is very similar to the agent vist, or actually very similar to the old style nuclear medicine tracers that showed masses in the liver as holes.

This agent at this point is available in Japan only.

We were hoping there may be some trials beginning in the us but unfortunately this does not seem to have occurred.

This is in fact an image of Sona and, you can see here that the liver parenchyma is nicely enhanced in this delayed image, and that these multiple metastases within the liver are devoid of contrast.

Namely because anatomically they're devoid of reticular endothelial cells as would be seen in the normal liver.

Artifacts in Contrast Ultrasound

There are some artifacts which have been described with regard to or in, in the use of, contrast ultrasound.

The three major ones I'm thinking of would be color blooming bubble noise or changes in peak systolic velocity as a possibility.

Here you just see a, a blatant example of, color blooming, where very similar to turning the gain way high, or too high when performing a scan, the color or the signal bleeds outside of the area of the vessel.

This, of course, can be easily fixed by either lowering the gain, or by decreasing the amount of contrast injected on the next round.

Bubble noise also can manifest itself with one per, if one performs a scan, spectral scan here you can see what are probably bubble aggregates, within the zone of intonation, producing this very spiky appearance.

One of the questions that we asked a number of years ago was what would be the effect potentially on the peak systolic or measured peak systolic velocity if one were to provide or give a contrast agent?

We did this using a flow phantom with various degrees of, artificially induced stenosis, and actually found that it did not seem to change the perceived velocity.

Here you can see 124 centimeters per second peak, without contrast.

And after contrast was administered in this blood bath, you could see that it was 123, so it doesn't really seem to affect it.

As we all know, using changing the gain with doppler, can have quite an effect on the perception of velocity, but this did not seem to be the case in our phantom studies.

Machine Adaptations for Contrast Imaging

Most, imaging that we do today does, rely upon a number of adaptations of the machines.

So you can't just put in a contrast agent and expect to use your regular machine to get adequate imaging.

Most of these machines involve or use some form of harmonics.

Remember that when bubbles are struck by the ultrasound beam, they resonate at specific frequencies which are proportional to the particle size.

They therefore throw back to the machine resonant frequencies and subharmonics, which requires a machine modification such that you transmit at one frequency and you receive at another, which is basically the harmonic of the bubble, which then eliminates almost all of the, echoes coming back from the tissue itself and really makes an image that is, that consists almost exclusively of the echoes that are arising from the contrast agent.

This obviously, tremendously improves the signal to noise ratio.

One of the other adaptations that is frequently used is known as pulse inversion harmonics.

In this case, multiple pulses may be sent into the patient.

They're sent in at different times such that, again, the gray scale pulses are in the opposite sides of a sine wave cancel each other out, such that, again, the idea being it's almost like a subtraction technique such that again, you're trying to optimize the image that is exclusively the result of the contrast agent rather than interference or artifact from the underlying gray scale ultrasound image.

Display Methods and Dual Imaging

One of the other things that's probably worth mentioning, there are various ways that one can actually display, these, contrast images.

You can see here an image of the kidney with a small, very brightly, enhancing mass.

And, but you see two images.

And the reason for this is, when you look right after the injection, it happens very quickly in the kidney, but when you look right after the injection on the left, you really don't see much of an image at all until the contrast reaches the target organ.

Obviously, the right side is the gray scale, normal gray scale image.

The left is strictly the contrast because you don't see the contrast or much of anything on that screen because that screen is only displaying the harmonics, everything else has been wiped out.

This image on the right actually allows you to use or to visualize your target organ or structure, then inject the contrast such that you see it actually lighting up the image as it does on the left.

So dual imaging is something we typically do.

Occasionally if we're looking at something, you can actually give some contrast.

If there's a little bit of contrast in there, it may help you to localize the structure.

And then you can do it with a single screen if you need a wider field of view.

But typically, we rely very heavily on this, dual image to, to find the target lesion or a target organ on the right using gray scale and then inject contrast and that shows up in the left image.

High vs Low MI Imaging

There are other adaptations, remember that, we frequently will think in terms of high versus low MI imaging.

Most of the time we do low MI imaging.

Low MI or mechanical index is basically a reflection of the ultrasound power.

Remember, the stronger the ultrasound beam, the stronger it strikes the bubbles, the more likely it is to break them.

So you don't wanna break the images.

So high MI imaging is typically not used any longer.

It may be useful, however, if you want more of an arterio graphic image where only the larger vessels are seen.

As is the case here, in this particular case, you can see that there's kind of a starburst pattern in the image on the left typical of focal nodular hyperplasia.

Again, that's an unusual thing for us to do.

Typically, we use low eye, low mi or low power imaging, such that the bubbles are not broken.

Quantitative Imaging Parameters

There are also numerous quantitative imaging parameters that may be used in, contrast imaging.

Here you can see a wash in wash out curve, uh, from a liver mass.

You can actually do an a, an averaging and get a nice smooth curve.

The spikes in there, are of the patients, either breathing sometimes or cardiac motion, but, you can see a nice wash in washout curve.

And obviously certain types of tumors, benign versus malignant or even certain histologic types of malignancy or benign tumors, may provide differing wash in washout curves.

There are other curves or quantitative parameters that may be useful.

There are a whole host of them, such as peak intensity area under the curve.

There are a whole group of them that have been investigated, in various ways by various groups around the world.

Liver Imaging with Contrast

So getting more specific now, I'm gonna talk a little bit about liver imaging with contrast and then turn my attention to kidneys.

We use this quite a lot in our practice.

We have a very active liver tumor, group at USC.

One of the simplest things and very, very helpful is the simple evaluation of portal vein thrombosis.

We can use it to characterize masses, in our county hospital, for example, where it may be very difficult to get patients back.

We can use it as sort of a one-stop shop.

Patient comes in, you find a mass, you give them contrast, and you can pretty much know whether you're dealing with a benign or malignant mass.

And whether this needs to be more carefully worked up or not.

It can actually also be an adjunct for indeterminate masses that have been seen or imaged with CT or mr.

Remember because it is a real-time examination, you may see things that can be missed in the sweep that typically accompanies a CT or mr.

We use it extensively to follow treated masses, masses that have undergone either interarterial chemotherapy or radiofrequency ablation.

In fact, there is abundant literature from some time ago now, showing that after piol has been injected.

Contrast enhanced ultrasound is superior to CT in determining whether the patients have been adequately treated.

We actually have folks in our own institution who use contrast injections to direct treatment or direct their needle in treating patients with RFA.

Portal Vein Thrombosis

Now in portal vein thrombosis, remember, it is absolutely essential to know if you're dealing with bland versus malignant thrombus in patients with cirrhosis, and of course hepatocellular carcinoma or suspected hepatocellular carcinoma.

This changes everything with regard to therapy.

If the patients have malignant thrombus, they are no longer transplant candidates and it's a rather bad prognostic sign because it's very difficult to treat.

It does not respond like the tumors themselves when these patients undergo IA chemotherapy.

Doppler typically should be applied when one sees a potential portal vein thrombosis, but it is extremely insensitive.

In fact, a article a number of years ago actually, found it was only about 25%, sensitive in identifying flow in, malignant portal venous thrombosis.

The published results, on contrast ultrasound have been spectacular.

Maybe a little questionably too spectacular, but extremely good.

With, one group reporting 98% accuracy versus CT 68%.

And do remember that the differentiation between benign and malign between benign or bland and malignant portal vein thrombosis can be very, very challenging on ct.

And mr.

In this case, they published a report showing that CT was only 68% accurate.

Another actually showed a hundred percent sensitivity and specificity.

So again, a simple technique that can be extremely valuable that we use quite a lot in our practice.

You can see in this particular patient that there is a large thrombus within the anterior or right portal vein.

I don't think anybody would have to point out where the tumor thrombus is.

You can see the immediate enhancement of the arteries.

You can actually see the feeding artery traversing down through the portal vein into the malignant thrombus.

This obviously is an extremely, dramatic example.

You can also see flow in the patent portion of the portal vein more inferiorly.

This can be contrasted with the image of a patient with bland thrombus in which you obviously see no flow within the thrombus at all.

Obviously a much better prognostic sign than that which was seen in the first patient.

Hepatocellular Carcinoma Enhancement and Washout

When we do imaging of liver tumors, typically we perform with CT or mr what we term multi-phase or a three or four phase imaging.

The idea being that hepatocellular carcinomas, will have intense enhancement in the arterial phase, generally said to be about 30 seconds after injection on ct, and then show what is termed washout in the later delayed phases, usually between 60 seconds and three to five minutes.

The theory behind washout, of course, is the fact that the blood flow to the hepatic, tumors to the hepatocellular carcinoma is typically derived from the artery, whereas the blood flow to the remaining liver is most of the time derived or largely derived from the portal vein.

So you see intense arterial enhancement with hepatocellular carcinoma and then you see washout where basically the flow goes into the tumor early, it's intense, and then it washes out before the remaining liver begins to enhance from portal venous flow.

So that's a nice example there of, arterial enhancement.

Here you can see some static images.

You can see, that the, image on the left is at approximately only four seconds, so it's very, very rapid.

The image on the right is several seconds later.

And you can see that the entire image or the entire mass is more, echogenic or more reflective than the surrounding liver.

This can be, contrasted with washout.

The images, the ultrasound images on the left obviously show that this tumor is now less reflective or darker than the surrounding liver.

Again, because it has come in through the artery, it washes out quickly and, in usually around maybe 20 seconds to 60 seconds, although again, washout may be as delayed as three minutes.

You'll see that the liver remains more enhanced than the mass itself.

And again, this is considered to be diagnostic of hepatocellular carcinoma.

Really, no other tumors will do this.

And you can see the correlate there on ct.

You can see that the remaining portions of the liver, the non-tumor portions of the liver remain enhanced, whereas the mass itself, same mass as shown on the ultrasound is less dense.

Response to Treatment

One of the other things I mentioned that we do with contrast ultrasound is, to look at the response of tumors to treatment, both with intraarterial chemotherapy and with, RFA radiofrequency ablation.

Successfully treated tumor is shown here.

You can see an echogenic mass beneath the dome of the right lobe of the liver.

At 25 seconds post enhancement, you can see that there is no flow within this tumor.

The devascularization of the tumor is much more important than size.

These tumors don't tend to shrink that much, after successful treatment.

So this is one of the ways that we monitor successive treatment.

This patient of course, you can see quite differently, this following intra arterial chemotherapy, shows a large area of persistent enhancement, very similar again to what's shown on the adjacent ct, telling us that this lesion is less than 50% successfully treated.

Typically these patients will go back and have another, treatment round with intra arterial chemotherapy, or in some cases when there is minimal amount of residual tumor, either no further treatment or potentially targeted treatment after contrast injection with an RFA to get the residual portions of the tumor.

Benign Liver Masses

Turning our attention to benign masses, Iman, he angios have very typical appearances on CT MR and also ultrasound.

This patient you can see on the gray scale image has a very, very fatty liver.

In these patients, he angios can be very difficult to diagnose definitively because with gray scale or diagnose at all with gray scale because they often show up as hypoechoic masses therefore being indistinguishable from other lesions, including malignancies.

Again, the classic features are shown here in this patient following injection of contrast early on, you can see that there is this peripheral intense nodular enhancement.

In going to more delayed imaging in this particular patient, you can now see that this mass has essentially become iso coic to the liver.

These findings are essentially diagnostic of a benign cavernous hemangioma peripheral fill in early, which is nodular in appearance.

Then complete fill in as we progress to more delayed imaging.

And again, the MR in this particular case is diagnostic in a very similar way.

You can see here on the T two imaging, this is a fluid-filled structure, so it's very, very bright.

After injection of contrast, you can see that there is some peripheral enhancement, very similar to what we saw on the ultrasound.

And then finally on delayed imaging, almost the entirety of this lesion fills in with contrast.

So very classic features of a cavernous, he angio another form of he angio has been termed flash filling him angios.

These can be somewhat problematic, particularly in a patient such as this where there is cirrhosis and there's a high question of, hepatocellular carcinoma.

This was a relatively subtle lesion that was seen on CT as intensely enhancing.

You can see here that there is a mass, which we might not have picked up on ultrasound prospectively.

It is echogenic, which is again typical of hemangiomas, but certainly may be seen with hepatocellular carcinomas.

And the interesting thing about this is that, again, these show up as intensely enhancing small masses on ct.

But if you watch these and go frame by frame, you can see here on this frame on the left nine seconds, you can see 10 seconds.

You can see very similar features to what we saw on that last patient with a large hemangioma that in the initial seconds there is intense peripheral nodular enhancement.

And then over the ensuing couple of seconds, this is only 11, and then 13 seconds or four seconds after those earlier images were shown, you can see that this thing again, shows more nodular fill in and eventually completely fills in just as would happen with a larger mass, larger hemangioma.

But this would never be visible on CT or mr because again, you only get a single sweep.

This is delayed imaging.

Again, these things can be persistently, echogenic or enhancing.

And again, typically you would expect washout if this were a hemangioma.

But just some interesting features that I think you would never be able to see, with the non-real time imaging of CT and Mr.

This patient, has again, a very intensely enhancing mass in the liver.

You can see that it's much more, echogenic than the surrounding liver.

This is a persistently enhancing mass.

And the interesting thing about this is if you look now in the delayed, you can see this is not washout.

It's quite the opposite.

You can actually see that this is more echogenic than the surrounding liver.

So this is not typical of a, hepatocellular carcinoma.

And the two major things that would be in the differential would be either an adenoma or a focal nodular hyperplasia.

The interesting thing about focal nodular hyperplasia is that it in some cases does demonstrate this stellate or star shaped pattern early on.

Again, you can only see this if you review image by image of the real time clip.

You don't really, it is very difficult to see with your eye.

And in this particular case, you can see these branching vessels that are coming out of the central portion of the tumor.

Again, very typical of a focal nodular hyperplasia.

Also an article, by Kim Etal described as, as typical of FNH centripetal filling versus in adenomas, there tends to be filling of the entire mass all at the same time.

Again, the CT shows very nicely, that this is an intensely enhancing mass.

I think CT and Mr. May be better at showing the sometimes scar that you see with focal nodular hyperplasia.

Again, this is not specific, and, is very nicely seen with, Mr.

One of the other, of course, things that MR can do that the other contrast agents do not is that, with EO vst you can actually see, imaging or enhancement of the tumor in delayed phase imaging, because of the uptake of EO VST by the hepatocytes.

And so, again, if this were in adenoma, which, or rather not hepatocytes, but the uptake of the, contrast agent, by the re system, if this were actually a adenoma, this would show up as a dark lesion or a hepatocellular carcinoma for that matter.

But because focal nodular hyperplasia is really, almost like a scar containing normal liver tissue, it tends to persistently enhance with vis something that Sona actually is also capable of doing.

This is a patient who had numerous masses throughout the liver, you can see that they're relatively echogenic.

And with contrast, you can actually see that these things enhance avidly.

And you can see this large one here just posterior to the main portal vein.

There were multiple other masses in this case.

And again, as opposed to FNH, again, this is not a hundred percent, as opposed to centripetal filling from the middle out, these lesions may, typically present with either heterogeneous, enhancement or diffuse filling such that the entire mass fills up or lights up at the same time.

And there isn't that central start of the enhancement pattern.

Here you can see that there is, again, persistent enhancement, just like in the FNH you can see here and up here, these two masses actually are more vascular than the surrounding liver.

In delayed phase imaging, again, not at all typical of what you would expect to see with hepatocellular carcinoma.

This is an interesting patient here where you see this large mass like area next to the spleen, in the arterial phase.

And this turns out to be a large HEPA or a large splenic artery aneurysm.

Something that is often associated, with cirrhosis.

Renal Masses

Turning our attention now to renal masses.

Just a moment of background.

At this point, because of the amount of imaging of the kidneys, that is done really as part of other techniques.

Patients have a gallbladder ultrasound, patients have a CT for back pain.

61% of renal masses are now said to be found incidentally before they present with symptoms.

This is a good thing in that the majority of these can now be resected, without actually even having to do a nephrectomy.

But there are issues with imaging, and contrast may be of value in some cases.

One of the problems is that renal masses often will remain indeterminate after conventional imaging.

So we don't really know what they are, so we often will actually have to surgically remove what turn out to be benign lesions.

Atypical cystic masses may be extremely challenging, and pose a real problem.

As we learn more about the behavior of these renal masses, we are now following patients over time, particularly those who are not great surgical candidates rather than actively intervening and doing a partial or complete nephrectomy.

Obviously the prolonged follow up of these patients with ct, does produce a large radiation burden and MR.

Or ultrasound, may be very valuable.

Probably the biggest thing, that is problematic about imaging these patients is the problem of renal function.

The CT and MR without contrast is extremely insensitive and very, very nonspecific with regard to, renal masses.

And of course, because contrast ultrasound is not, does not affect the kidneys, it's an excellent technique for characterizing masses within kidneys of patients who have had, issues with renal function.

And again, patients who have had partial nephrectomy will very frequently have poor renal function afterwards.

So this is a very good technique in our experience for this group of patients in particular, there is considerable literature out there on the use of contrast agents in renal masses.

Again, it allows the assessment of the internal vascularity of both the kidney and the tumor.

It can be helpful in identifying flow in the wall of complex cysts or in septi.

It can help with defining pseudo lesions such as column of britan or infarcts or scars.

It can help to characterize indeterminate masses on CT or mr.

And again, as I mentioned, is extremely useful in patients in this regard with who have, chronic renal failure.

Just as we mentioned in the liver, it is possible to do, quantitative or semi-quantitative analysis.

And again, those same kind of wash in wash out curves, may be valuable in differentiating one type of renal mass from another.

Case Examples of Renal Masses

And just a couple of cases, this is a patient, 68-year-old man with chronic renal failure who presented with hematuria.

You can see on the, several MR slices, that he does have at least two masses in the kidney.

One higher signal intensity in the lower pole, one of lower signal intensity in the upper.

Again, given his renal failure, he was not a great candidate to undergo.

Contrast enhanced mr.

And we brought him and did this ultrasound on him.

With contrast, you can certainly see here that there is early on a more intense enhancement of this mass.

This mass then washes out with regard to the kidney.

Remember, the kidneys are extremely vascular and therefore everything happens very quickly.

So you may need to go back and review image by image to get more information about the enhancement characteristics of these lesions.

This did turn out to be a clear cell carcinoma.

This is the inferior mass of this patient.

And in this particular case, although this is a little bit worrisome, remember that septi do have blood vessels.

And you can see here that there is some enhancement of these septi.

This turned out to be a benign complex cyst.

This is another man, 74-year-old with chronic renal failure.

CT identified, two masses within the right kidney or a bi lobed mass.

When we performed ultrasound on this patient, you can see here that there is a large mass here, which again is relatively hypovascular.

It never reaches a point of being more vascular than the surrounding liver.

And this turned out to be a papillary carcinoma.

A second lesion was identified in this patient also, clearly less vascular than the surrounding, liver or kidney parenchyma.

And again, you can see both of these masses here and both of these turned out to be papillary carcinomas.

Interestingly, there was a third mass that was identified, which is shown here to be extremely vascular, more so than the surrounding kidney.

This never washes out and, this was not seen or appreciated on the CT scan, but in fact represented clear cell carcinoma.

There is some literature which actually suggests that clear cell carcinomas tend to have these characteristics versus the papillary carcinoma, such that clear cells tend to be more vascular, remain hypervascular, where papillary carcinomas tend to be less vascular and will sometimes wash out.

This is another patient with a GFR of 30.

This woman presented with a, cystic lesion on T two, which appeared to have a solid component centrally.

Obviously she had a CT to begin with, which, was not terribly useful, although the cyst was not low density.

So that raised some initial concern, which is why she wound up with the mr.

Again, on the, even on power doppler, we were able to see that there's solid component, a solid component here with some flow, which enhances dramatically on the, contrast and after contrast injection.

Here you can see again, this dramatically enhancing component of this malignant renal mass.

This turned out again, given the very, very high vascularity, this did turn out to be a partially cystic clear cell carcinoma.

This is another interesting patient where contrast was very helpful on the gray scale evaluation.

This patient was on chronic dialysis and had multiple cysts within the kidney.

On gray scale evaluation, we saw this area of solid material within a cyst.

Obviously, this was unable to be differentiated as opposed as whether as to whether this actually represented a hemorrhage, for example, into a cyst or potentially a tumor.

These patients do have a propensity to develop renal cell carcinomas.

And on the ultrasound you can see here that there is maybe a septum in here, but this is largely an avascular area.

You can see the gray scale appearance of this here.

And this represented a, a hematoma within a small cyst in this, dialysis kidney.

This is another interesting patient with a somewhat indeterminate mass.

This mass was relatively high density on, non-contrast ct.

You can see here that there was enhancement after contrast, but less than 15 hounds field units.

And, the clinicians were somewhat concerned about this.

This is kind of scary on the ultrasound because I must say if I were actually to just look at this on non-con, I would probably have chalked this up to some back scatter in an otherwise simple cyst.

You can clearly see here, that this enhances and did turn out to be a renal cell carcinoma.

Another simple thing that we do here is a patient with a, history of malignancy, with a pet ct, an area of low density here with no enhancement following the agent, injection of the, fluoro FDG.

And clearly this turned out to be a simple cyst on, contrast ultrasound.

One of the areas that you can also look at is the, finding of renal vein thrombosis.

We found that this tends to be somewhat challenging On contrast, potentially we don't have enough experience with this yet.

But you can see that there are some defects within this area of the renal vein corresponding to this large thrombus seen here on the con on the contrast enhanced mr.

This is a patient with a very large, remember when these rccs become very large, they may cut off their own blood supply and become partially necrotic.

You can see that this kidney is kind of splayed, all around this very large enhancing mass, which has an, a large area centrally of necrosis with no vascularity.

Very similar to what is seen in this patient who did eventually have a CT with contrast.

You can see this large relatively, non enhancing area centrally.

You can see that there's a lot of disorganized vascularity here.

And again, just this very small or thin shell of, displaced renal tissue more peripherally there.

Rarely we may see.

Oncocytoma.

There is a, a recent article actually describing, the features on contrast of oncocytoma.

This is a surgically proven oncocytoma.

You can see that it has this kind of blotchy area of central, low area, area of low, enhancement.

And although, again, not specific, this is something that might suggest the presence of an oncocytoma.

Very similar to again, what is seen on the, CT with contrast.

In these kinds of patients, it may be, depending upon the clinician, they may wanna simply remove them, but it would be potentially something upon which one could perform a biopsy and avoid surgery.

Another interesting group of patients is shown here.

We have a very large, onco or urology group.

We have a a, a, a urology group that sees large numbers of patients, and they are well known for their partial nephrectomies.

Obviously while rare there is the possibility of local recurrence after the nephrectomy for their, renal cell carcinomas.

Again, the problem in these patients is oftentimes they will have, abnormal GFR, this was 50, which is below the level that we typically would like to perform contrast on these patients, either with CT or mr.

But on the lateral, on the axial view, there's this mass like low density area.

Here you can see some surgical clips.

And of course the question was, are we dealing with a tumor?

On the contrast ultrasound, you can very nicely see that this actually represents probably a small seroma, and that there is absolutely no abnormal areas of enhancement in this particular case.

So it's gonna be very, very useful again, particularly as many of these patients will suffer from impairment of their renal function and are unable to safely undergo CT or mr.

Guiding Biopsy with Contrast

Another interesting use of contrast, in closing is that that of guiding a biopsy, this is something we've only occasionally done, but you can see that there's this rather poorly defined mass on ct, in the upper pole of the kidney.

On ultrasound there was a suggestion of a mass again, in this region, in the medial portion of the kidney.

The, patient and the clinician did not want to undergo a nephrectomy or even laparoscopic resection until they were certain of number one, was it really there?

And number two, what was the cell type.

Interestingly when you look at this on contrast, enhanced ultrasound, you can very clearly define that there is a hypo enhancing mass in a, in the same region, and it's certainly much better defined than on the non-contrast CT or non-contrast ultrasound.

We eventually then were able to use this as a guidance technique, to perform a biopsy of that specific area, with much greater confidence than we would've, had we not had the contrast enhanced, ultrasound as well.

This actually turned out to be a transitional cell, which did of course alter the surgical technique.

Conclusion

So, we've, had a very good run in the last couple of years with contrast ultrasound in the kidneys and the liver.

We're using it in several other areas at this point, and I'm hoping that, before too long, this will be something that is more widely applied than it has been in the past in the United States.

Thank you.