Incidental Findings in the Abdomen on Ultrasound - HD

Introduction to Incidental Findings in the Abdomen on Ultrasound

I am Franklin Tesler from the Department of Radiology at the University of Alabama at Birmingham.

I'm going to be speaking about incidental findings in the abdomen.

On ultrasound, I'm going to be speaking of ultrasound of incidentalomas, concentrating on the abdomen.

I'm from the University of Alabama at Birmingham.

Anybody who does any sort of medical imaging, be it ultrasound, CT, MR, or any other imaging modality is familiar with the concept of incidental findings.

An incidental finding is defined as one that's unrelated to the disease or condition for which the scan was requested.

If you combine that with the suffix OMA, which comes from the Greek word soma, meaning growth, you end up with the term incidentalomas, which has become the term that's popularly applied to incidental findings in any part of the body on any imaging modality.

The Story of William Cassella

To start off by telling you a story.

This is a photograph of William Cassella, the former chair of the Department of Radiology at Emory University in Atlanta over a decade ago.

He published his experience, his personal experience with incidental findings.

He underwent a CT scan which disclosed several incidental findings, including a liver mass and some lung nodules.

Of course, physicians are never pleased to leave well enough alone, and they decided they needed to figure out what these are, which led to a liver biopsy.

Subsequently, a PET scan, positron emission tomography specifically to look at the lung nodules, and that was indeterminate.

So they decided to go ahead and do lung surgery.

Fortunately for Dr. Cassella, all these findings turned out to be benign, but he suffered a considerable amount of pain because of this, and the healthcare system spent a considerable amount of money investigating what didn't turn out to be clinically important to him.

Handling Incidental Findings

What do we do now when we see an incidental finding on sonogram or any other imaging modality?

In increasing order of magnitude, we usually or often start off with more tests.

And in the fee for service model where you get paid more for doing more tests, that always seemed to be a good thing.

Not only were you trying to figure out what the incidental finding was, but you'd be earning more money in the process.

Several years ago, Chris Systrom and coworkers published a really interesting article in radiology that's referenced here, and this graph is from their article.

It shows the recommendation rates for follow-up imaging according to the patient age in decades.

And as you can see from this curve, as you'd expect, the older the patient, the more likely the radiologist was to recommend follow-up studies.

And that makes sense because the older you are, the more likely an incidental finding is to be something clinically significant like a cancer.

Interestingly enough, in this study, they also looked at the rate of recommendation for follow-up studies plotted against the experience of the radiologist in years, which is here on the x axis, comparing it to the imaging recommendation percentage on the Y axis.

And you see it's an inverse relationship except for a little uptake here at the end.

The older radiologists tended to recommend follow-up studies less often than younger ones, and that might be due to the fact that older radiologists by benefit of more experience, are more likely to know that an incidental finding is something that doesn't need to be touched and doesn't require follow-up studies.

Levels of Intervention

A higher level of intervention for an incidental finding is biopsy.

Sometimes we look at something, an imaging test doesn't show what it really is, and we actually have to do a biopsy as in this case of a patient with hepatocellular carcinoma.

Of course, in this case, the biopsy was warranted.

But there are cases where the incidental finding turns out to be something completely benign, as in Dr. Cassella's case, and still a biopsy is performed and the highest level of intervention to figure out what something is is surgery.

And as you heard, Dr. Cassella did undergo surgery to prove that his lung nodules were benign.

Rational Approach to Incidentalomas

What is really needed is a rational approach to incidentalomas.

And the rationale for this rational approach, if you will, is to do two things.

One is to spare patients' unneeded suffering by having follow-up studies.

And that doesn't only mean reducing the rate of surgery or biopsy.

Patients who have an incidental finding and hear about it and are told that they require further imaging tests are often extremely nervous and worried about what those tests will show until they prove that the incidental finding is benign.

And second, the healthcare system, as everybody knows in this country, and true in many other countries as well, but especially true in the United States, is costing way, way too much.

And we have to reduce the number of unneeded imaging tests and other procedures in an effort to reach this rational approach.

American College of Radiology Incidental Findings Committee

The American College of Radiology formed an incidental findings committee several years ago, and these are the people on the committee, which was chaired by one of my colleagues at UAB, Lincoln Berlin.

And they published a white paper of their committee's findings.

Ultrasound Contrast and Its Impact

So now what I'd like to do is go through several areas in the abdomen and talk about specific findings on ultrasound with one caveat that I show here with the bubbles in the background contrast.

That is ultrasound contrast changes everything.

I'm hopeful that FDA approval for ultrasound contrast will be attained within a year or two, and that's going to change in a remarkable way how we do ultrasound and how we investigate some incidental findings sonographically, but we're not quite there yet.

Liver Findings

So let's start off with the liver, right upper quadrant and talk about cysts, which are fairly commonly seen.

Simple cysts are often benign developmental cysts.

There are others as well, including Von Meyenburg Complex, which are multiple typically associated with multiple echogenic nodules, but can be multiple cystic nodules as well.

Other conditions in the differential diagnosis include Caroli disease, adult polycystic disease, but most often we deal with simple liver cysts and sometimes they can be hard to pick up.

If you look at this clip, because we're seeing lots of vessels in cross-section, it may be difficult to pick up where the cyst is.

And if you watch this part of the movie as it scrolls in and out, there actually is a cyst right where my pointer is appearing briefly right there, but it's easy to miss because it blends in with all the anechoic structures around it.

Here's a case of polycystic liver disease.

In fact, this patient also has polycystic kidneys, multiple cysts through the liver.

In fact, in these cases it's often difficult to separate the kidney from the liver because both contain so many cysts, but it's pretty easy to tell what you're dealing with in this situation.

Complex Cysts in the Liver

Complex cysts also occur in a variety of conditions and can be neoplastic related to inflammatory or infectious conditions or post-traumatic.

There's also of course a miscellaneous category as there is with anything else.

And by complex I am using the terminology that's typically applied to cystic structures anywhere in the body on ultrasound thickness or irregularity of the wall, presence of septations or mural nodules, calcification, or in some cases the contents of the cyst being something other than simple fluid.

And here's an example of a clip showing a complex cyst here in the right hepatic lobe, you can see a septation that's fairly thick traverses this cyst.

Here's another case of mildly complex cyst in the liver.

Some small septations peripherally in the cyst, so technically complex.

And here from the literature from this article in Journal of Ultrasound in Medicine is a case of a much more complex cyst that turned out to be a biliary cystadenoma.

Now how you deal with these depends, and I'll reemphasize this later, depends on the background of the patient.

In most cases, cysts including ones that are mildly or even moderately complex in the absence of any other concerning features about the patient historically can be safely ignored or followed.

Certainly simple cysts, we don't suggest any follow up before when we see them.

Incidentally, I show this case to highlight the fact that not everything that looks like a cyst is a cyst.

This is something I frequently emphasize to the sonographers, residents and fellows I work with.

So this is a case from not too long ago in our lab at UAB that was brought to me.

And if you looked at this fairly quickly, you'd see that there's this hypoechoic structure lesion very close to the anterior liver capsule.

And if you look at it, you could say that the through transmission is slightly increased and pass this off as a cyst.

This is quite small as you can see, but something about this bothered me when I was looking at it and I asked the sonographer to go in and get some color Doppler images, which they did.

And there's a clip from that.

You can clearly see that there is flow within this.

It's not cyst at all, this was neoplastic.

So you have to be very, very careful about calling things cystic, whether it's in the liver, kidney, or any other organ, and make sure that the lesion adheres to all the properties of cyst including through transmission that is commensurate with the size of the lesion.

And if you are in doubt, color Doppler is extremely helpful as it was in this case.

Pseudo Masses in the Liver

Pseudo masses frequently occur in the liver as well, commonly related to fat, either focal fat deposits or focal fatty sparing.

There are a number of clues you can use to distinguish focal fat from true space occupying lesions, including the location configuration, lack of mass effect, because fat typically does not have any effect on adjacent structures.

For example, blood vessels will traverse the region rather than being displaced by it.

And here's an example of the two sides of the same coin.

In this case, we see a fairly geographic echogenic area in the liver distinguished from the area around it.

And this is a focal fat deposit and you can see that its margins are unlike most masses, which are round or nearly.

So this has a straight anterior margin, a so-called geographic pattern.

The flip side of that is shown here.

This is a fatty liver.

It's steatosis is shown by the increased reflectivity, but there's an area that's somewhat elongated here that is less echogenic that represents focal fatty sparing.

And this illustrates one of the signs that I talked about, namely lack of displacement of vessel.

As you can see that this venous branch traverses this area of focal sparing rather than being displaced by it.

Location is another important feature near the gallbladder fossa, near the portal vein.

Those are common places for focal fatty sparing.

Solid Masses in the Liver

Solid masses are sometimes seen incidentally on sonography of the right upper quadrant as well.

And it's very important to remember that management.

That is your recommendations of what to do depends on the patient's risk status.

So if a patient, for example, has a known primary malignancy or is at risk for malignancy that is their cirrhotic or has a history of hepatitis, those will have to be handled differently from a young patient without any such history.

One of the commonest incidental findings that we see in the liver are hemangiomas and we see probably in our lab at least two or three of them incidentally every day, their ultrasound appearance is well known.

They're well-defined homogeneous echogenic compared to the adjacent liver, with the caveat that if the liver itself is abnormally echogenic as in steatosis, a hemangioma may actually appear hypoechoic relative to the fatty liver.

They may have increased through transmission, not as much as a cyst as of the same size, but there nevertheless, if you look at it, and I'll show you an example of that, and here's an example of a movie clip of one small incidental hemangioma.

This was a young patient without any risk factors and in cases such as this, you can safely say that the patient doesn't need any follow up.

One of the important features in distinguishing echogenic lesions that require follow up from those who don't, and this applies to liver lesions in general, is the lack of a hypoechoic halo, which you would see around the lesion, which doesn't exist in this case.

And that's further evidence that this is benign.

Here's another example of a hemangioma, and you can see if you look behind this one, and I'll get to the right point in the clip right there, you can appreciate subtly increased through transmission behind it.

And this is another clue.

Again, there's no hypoechoic halo.

It's well-defined, it's relatively small and these can be safely ignored.

Here's one that's a little bit different, although this turned out to be a hemangioma, it's being measured here near the liver dome.

You can see this one is a little bit heterogeneous and cases that are atypical, even if the patient is at low to moderate risk.

It's worth I think, in those cases, suggesting a follow up study.

On the other hand, compare it to this case that I don't think anybody would have difficulty with.

This is a fairly echogenic mass within an echogenic liver.

It's actually nearly isoechoic, but it also shows the halo.

And I don't think anybody would mistake this for a benign hemangioma, nor would they in this case.

The only feature in common is the increased echogenicity, but this is a hepatocellular carcinoma, an irregularly shaped mass.

So again, what you're looking for in hemangiomas are relatively small, say around three centimeters or less.

Well-defined, increased through transmission, homogeneous with in a patient with really low risk of malignancy and those can be safely ignored.

Spleen Findings

Let's move on to the spleen.

And the spleen is an area that's sort of tough on ultrasound.

I think a lot of radiologists would prefer not to look at the spleen because there are a lot of findings in there that as I'll show you in a moment, are relatively non-specific.

But we do look at them as part of the abdominal ultrasound.

So we need to be aware of the appearance of splenic lesions.

And I'm going to divide them based on this article from JUM by Benter et al into hypoechoic and echogenic and the hypoechoic lesions.

It's a large differential including cysts, metastasis, lymphoma, abscesses in the acute trauma situation, hematomas.

And just to append to that, it doesn't take a lot of trauma to produce a splenic hematoma.

I recall a patient some years ago who had a huge intrasplenic hematoma and injury from a relatively minor fall.

And this is especially true in patients who are predisposed to have hemorrhage or injure the spleen if the spleen is large or they're on anticoagulants or conditions like that hemangiomas occur in the spleen.

Infarctions fairly common and lymphangiomas all can be hypoechoic.

And here's an example from Benter's article of a splenic cyst.

Splenic cysts are actually fairly uncommon.

Some are developmental, some are congenital, some are acquired.

But generally if you see a structure that looks like a simple cyst, it usually doesn't need follow up, compare it to this hypoechoic lesion, also from the same article, which is geographic and wedge shaped and hypoechoic, which is a splenic infarct.

Sometimes color Doppler can help with these or power Doppler, but usually not.

It's more the geographic appearance, although I will mention that many, as one of my chiefs used to say, patients don't usually read the books and it's not uncommon.

We see this more in CT and than ultrasound that splenic infarcts adopt very, very odd patterns and don't have the typical wedge shaped appearance.

This is another case from the same article.

This is a large spleen too large to fit in this linear array image, but multiple hypoechoic nodules throughout the spleen, which represent splenic lymphoma.

I think anybody seeing this case in no matter what the clinical setting would realize that this is something that can't be ignored and requires further follow up on the echogenic side of splenic lesion cysts, that hemorrhage can be echogenic as can metastasis.

Some abscesses hematomas when they reach the subacute stage, hemangiomas subacute or chronic infarctions or calcifications.

And here's a case from our lab of a small echogenic splenic lesion, which was a hemangioma.

It said that these are fairly common.

We actually don't see them as often as we would expect to.

I think that's probably because we perhaps don't scrutinize the spleen as much as we should or as much as we do the liver.

But we see these from time to time.

Now you may have noticed that in describing a hypoechoic versus the echogenic lesion, there's a lot of overlap and I'll go through this list again side by side to emphasize that.

So a lot of splenic lesions have variable ultrasound appearances.

The important thing is with all incidentalomas is to recognize the cases that need something else done to diagnose them, whether it's additional imaging or other types of investigation.

Pancreas Findings

Let's move on to the pancreas.

Now, the pancreas, although it can be seen with ultrasound and it's part of every routine abdominal sonogram that we do, is not an organ that is typically thought of as being exquisitely well evaluated by ultrasound because of the presence of intervening bowel.

But nevertheless, you do occasionally encounter incidental pancreatic masses sonographically.

Ultrasound does have a strong role to play in the endoscopic realm in many cases of especially cystic lesions, but also non-cystic lesions of the pancreas.

Endoscopic ultrasound is the next procedure of choice because it can be used to guide FNA biopsy at the same time.

So pancreatic masses can be divided broadly into solid or cystic categories.

I don't think anybody would have trouble with this case of an abnormal pancreas.

You can see here that the main pancreatic duct is dilated and as you trace it toward the pancreatic neck region over here, there's an irregular mass.

And seeing this as an incidental finding, nobody would have any difficulty saying that this requires further investigation.

And this is a pancreatic adenocarcinoma in order to put some structure around the handling of pancreatic cystic masses.

This is from the article from Lincoln Berlin et al and JACR that summarized the results from the Incidental Findings Committee.

There is this algorithm for handling cystic pancreatic masses detected on CT MRI with or without contrast or ultrasound.

And I'm not going to go through this whole paradigm, but I just want to point out that how you handle these in their schema depends partially on size.

And that usually requires some sort of follow up.

Even for the ones that are less than two centimeters in this case, they suggest a follow up in one year if it's less than two centimeters.

This article is widely available and I encourage you to look at it because it gives you something to hang your hat on in terms of how to handle these.

Again, one of the real important goals of this committee and of any group that's looked at incidental findings in general is to put some structure around it because otherwise everybody does pretty much what they want to do in terms of recommendations based on their own experience.

And this gives you something to go by in deciding what to do.

So the general rule for these pancreatic cystic lesions is follow up CT or MRI and solid lesions in the pancreas, as I mentioned, always require some sort of other test.

Kidney Findings

Let's move on to the kidneys.

Looking at renal masses, which again can be divided into solid or cystic in nature.

Starting off with solid masses, they almost always will lead further characterization with CT or MR.

The only exception to this are small echogenic masses.

This is a case of a larger echogenic mass that is a renal cancer.

Again, I don't think anybody would pass this off as a benign lesion that needs no further workup.

Here's another case of an echogenic mass.

In fact, this one is infiltrative enough that it blends in almost imperceptibly with the rest of the kidney here in the interpolar region.

Again, this would obviously need further workup.

The one area that I mentioned where you may be able to get away with not recommending a million dollar workup is angiomyolipoma versus neoplasm.

And if you see acoustic shadowing related to a small echogenic mass is probably reliable for AML.

On the other hand, a hypoechoic halo as in the liver is worrisome for neoplasm.

And here's some cases, some small echogenic masses in a young patient without any other risk factors and no history of hematuria.

You can probably safely follow this with imaging.

And if I see something on ultrasound that requires follow up with imaging, and I can see it on ultrasound, I'll often recommend sonography as the modality of choice for follow up.

On the other hand, here's a much more ugly looking echogenic mass arising from the kidney.

You can see as this clip played, here's the kidney and here's the mass.

And this actually turned out to be an angiomyolipoma.

If you're in doubt, it's easy enough to do a CT or MR and pick up the macroscopic fat in AML, which is very unusual in a renal cancer.

Bosniak Classification for Cystic Renal Masses

Now the Bosniak classification is something that's been around for many years, which was developed by Bosniak, after whom the classification scheme is named.

And that's well known.

And one of the advantages of this classification is that it's been widely adopted, not only in the imaging community, but also by the urology community.

And this ranges from one simple cysts two minimally complex cysts, two F, which was added after the original classification F for follow up for slightly greater degrees of complexity.

Three very complex cysts and four extremely complex cystic masses.

And as you go up in this classification from one to four, you have a much higher chance of malignancy.

So simple or minimally complex cysts don't require follow up, whereas these others do.

And in fact, in the three to four lesions will typically require surgery to remove them and achieve a diagnosis.

Now, Bosniak in an article that he wrote in 2012 stated categorically that ultrasonography can't be applied directly to the classification system that is named for him.

Nevertheless, radiologists do sometimes use the Bosniak classification to apply to cystic lesions.

I personally don't because I'm a purist about it and I like listening to the guy who came up with the classification system to begin with.

On the other hand, if you see a simple or minimally complex cyst, you can probably safely call it a Bosniak one or two, even though you are strictly speaking, not supposed to be able to do that and say that no further follow-up is required.

The one exception for all cysts is large cysts, even if they're simple, can cause pain and those may require some sort of intervention, but you can just describe the size of the cyst.

By the way, when I'm describing cysts, because they're typically round, I usually give only one dimension.

I only give multidimensional measurements when they have an irregular elongated shape.

And here's some examples of mildly complex cyst here arising of the kidney.

From the right kidney, you can see a fairly thin septation.

This would probably require at most ultrasound follow up.

Here's another one with a little bit more complexity, which I definitely would recommend follow up on.

And I mentioned earlier that contrast changes everything.

This is one area where I think ultrasound contrast is going to have a huge, huge benefit because when we see something like this, rather than guessing about it and maybe saying follow it up in some amount of time or suggesting a contrast enhanced CT or MR, we'll be able to give the contrast right on the spot and be more specific about what we say.

As I said, contrast changes everything as this Galapagos giant tortoise knows they're smart, they've been around a long time and they see people from all over the world.

Everywhere else is using contrast pretty much.

But the United States, when this is available, it's going to be change what we do in our daily practice.

We're going to have to change how we work to accommodate this because for incidental findings, be they in the liver or kidney, we're going to say, we don't know what this is.

Give a shot of ultrasound contrast and be able to characterize it right there.

Conclusion

So again, the overarching rule is that you want to, in finding things that you didn't expect to see incidentalomas, you want to decide does this need further workup or is it something that could be safely ignored and not just routinely.

Every time you see something that wasn't unexpected, automatically recommend some sort of further workup.

Thank you very much.