Sonography of the Gallbladder and Bile Ducts - HD

Introduction

Hi, I'm Mark Cleaver.

I'm a professor of radiology at the University of Wisconsin Madison, and I'm gonna talk about ultrasound of the gallbladder and bile ducts.

Today I'm gonna talk about sonography of the gallbladder and bile ducts.

Gallbladder Sonography

Gallstones

First, talking about the gallbladder.

I'll cover the topics of gallstones, wall thickening and acute cholecystitis.

With regards to bile ducts, we'll talk about dilatation, wall thickening, and cystic change.

First, with regard to gallstones, the diagnostic criteria are fairly straightforward.

Gallstones need to be mobile, echogenic, and then a shadow.

However, obtaining shadowing from a gallstone may not be altogether straightforward, and there are many determinants of shadowing.

Probably the most important one is simply stone size.

Stones smaller than three millimeters are frequently difficult to get shadowing from.

In addition, there are many technical features that contribute to the presence or absence of this distinctive shadowing behind gallstones.

In particular, one has to be careful to use a higher frequency, a focal zone that is appropriately placed, output power and receiver gain appropriately adjusted so that this shadow is not obscured unintentionally.

Second, the position and orientation of the stone is important.

I'm gonna talk a little bit about why stone's shadow 'cause that's important in some of their features.

And in particular, what surface features contribute to this presence or absence of shadowing?

With regard to technical factors, you can see that on this case, in this case, the shadowing from the stone is somewhat dirty, as we say, because there's acoustic noise within the shadow.

It's not clean.

Again, this one too.

But this one, in this case, the dirty shadowing is a result of an inappropriate gain setting.

And here, when we appropriately adjust the gain and the location of the focal zone as indicated by this carrot, here, we see that the shadowing looks essentially clean.

So the placement of the focal zone and the level of the acoustic gain are important in the quality of the shadow.

Now, as a general rule, we often say that shadowing behind gallstones is clean shadowing, whereas shadowing behind air or other similar things is dirty.

The reason for that is due to the character of the beam and the interaction of the beam with the surface of the gallstone.

In particular, a roughened surface will tend to scatter the beam.

So there are few returning echoes to the transducer face because there are very few back scatter events.

There is little or no acoustic noise written into the shadow.

In distinction, when there is dirty shadowing, there is a strong, coherent back scattered signal, such as from air.

And that is involved with multiple back scattering events, much of which comes back to the transducer.

And all of those back scattering echoes are written into the shadow as acoustic noise.

So in the roughened surface of the gallstone, clean shadows tend to predominate and on the flat and strongly reflective surface of air and other such surfaces interfaces, dirty shadows tend to predominate.

Pitfalls in the Diagnosis of Gallstones

There are many pitfalls in the diagnosis of gallstones, first of which is echogenic bile or sludge.

This can actually take on a rounded shape, the so-called tumefactive sludge and look for all the world like gallstones.

But the key feature here is that these are non-shadowing objects.

Echogenic bile or sludge is however important in as much as about 15% of such patients will go on to develop stones.

The other feature here that's important is that sludge can obscure the interfaces of small stones.

Here's an example of tumefactive sludge.

You can see it's rounded, almost polypoid in orientation and could easily be confused with a mass or if smaller, a small stone.

Here's an example of how sludge can obscure small stones.

This is a gallbladder containing predominantly sludge and a few echogenic interfaces.

The subsequent KUB or abdominal radiograph clearly demonstrates the presence of gallstones in the right upper quadrant, which are all but invisible to us on the ultrasound.

The other pitfall for gallstones of the so-called cholesterol crystals.

What's distinctive about these cholesterol crystals is that they have this comet tail artifact instead of a shadow, which of course is black.

What we see is a trailing line of echoes or a white tail.

And it narrows conically to a point.

This is so-called comet tail artifact, and is a consequence of short path reverberation artifact within the cholesterol crystals themselves.

So other pitfalls is sometimes a gallbladder filled with stones can be difficult to identify.

It looks all the world like bowel gas, perhaps like a porcelain gallbladder in phlegmonous cholecystitis or an abscess.

So all these things can have a similar appearance.

The important feature that distinguishes the gallbladder filled with stones from the other entities is the so-called wall echo shadow sign.

This wall echo shadow sign, I believe, is a somewhat unfortunately named sign because it calls attention to everything that is not diagnostic.

The most diagnostic feature of the wall echo shadow sign is a thin crescent of bile that exists between the wall of the gallbladder and the echo produced by the stones.

So the reason we see a wall echo, and then the shadow is because this crescent of bile separates the wall from the stones.

So one could argue that it might be more appropriately referred to as a crescent sign.

However, wall echo shadow is a time honored reference that has now been cemented in the literature.

And this is how you'll read it.

So the wall echo shadow sign again is the gallbladder wall.

The echo is the stones, and the shadow is of course, the shadow produced by the stones.

In contradistinction, the porcelain gallbladder looks very different.

You will not get a crescent of bile that separates the wall from the echo and the shadow.

In this case, the shadow arises from the wall itself.

So in this gallbladder, you can see this brightly reflective interface here, and again, posteriorly and the echo, but no separation between the wall and the interface that is producing the shadow, because in this case, the calcification is in the gallbladder wall.

And as has been described over time that this is a sign of potential risk for gallbladder carcinoma.

Here are a couple of examples.

If you have any doubts about whether you're seeing a wall echo shadow or a porcelain gallbladder, or for that matter, an emphysematous gallbladder.

Oftentimes simple radiography, as we see here on our left or CT scan, can provide useful confirmation.

Here you can see the calcification outlining the wall of the gallbladder in this case, and the CT shows the calcification in the wall indicating that what we're looking at is a porcelain gallbladder.

Incidentally, this porcelain gallbladder also has stones within the lumen of the gallbladder.

And that's not an uncommon occurrence.

Emphysematous cholecystitis is similar to the porcelain gallbladder in as much as the echogenic interface producing the shadow is located within the wall of the gallbladder itself, rather than separated from the wall, as in the case of the gallstones within the gallbladder lumen.

Emphysematous cholecystitis is an important diagnosis because it's often indicates a infection with gas forming organisms.

It tends to be seen with diabetics, and this circumstance needs to be taken very seriously because of the possibility of gallbladder necrosis, gangrene and perforation.

You sometimes see a ring down artifact from the air bubbles.

Sometimes you see that dirty shadowing that I described earlier because of the very strong and very flat, coherent back scatter from the flat surface of the air in the wall of the gallbladder.

Again, plain film or CT are important confirmatory signs of this diagnosis.

Here's an example of emphysematous cholecystitis.

Again, the reflection highly reflective material is within the gallbladder itself, but instead of the black shadow, you can see the acoustic noise of the so-called dirty shadowing behind this echogenic interface here.

And again, if you do the plain film, you can see the crescent of air within the lumen.

And actually, there's quite a bit of intraluminal air in this circumstance as well.

Gallbladder Wall Thickening

Gallbladder wall thickening is an important feature of gallbladder disease that comes in two varieties.

It can be focal or diffuse.

In circumstances where the gallbladder wall thickening is focal, there are several different possibilities to be considered.

There are the hyperplastic cholecystoses, such as cholesterolosis and adenomyosis, as well as various masses, of course, infection in the setting of acute or chronic cholecystitis.

And then sludge or stones that may be adherent to the wall, giving the impression of focal wall thickening.

The hyperplastic cholecystoses come in two major varieties.

The so-called cholesterolosis are the strawberry gallbladder in which deposits of cholesterol stud the wall and create surface irregularities.

These tend to be small polypoid intraluminal masses, often multiple.

They have kind of a salt and pepper look containing echogenic speckles within them, and they often have a lobular, almost cauliflower surface or contour.

Here, it's a typical gallbladder polyp.

You can see that sort of lobular contour and the sort of salt and pepper, the black and white appearance of the polyp itself.

Adenomyosis is a common disease, and it has a distinctive appearance.

Oftentimes this can be a focal process.

It also can be diffuse.

More often it is focal.

It is created because of the ingrowth of the epithelium within the lumen of the gallbladder into the muscle.

That ingrowth of that glandular tissue creates pockets or sinuses, some so-called Rokitansky-Aschoff sinuses, which fill with bile and sometimes stones and sometimes cholesterol crystals.

One of the most common presentations of adenomyosis is this of a fundal mass.

This is the gallbladder, of course, I'll outline that with the cursor here.

And this fundal mass here within the gallbladder fundus is typical of adenomyosis.

This can of course also be neoplastic.

It's difficult to tell, but that is a much more characteristic, much more typically going to be adenomyosis.

Even more distinctive for the diagnosis is the segmentation of the gallbladder created by a narrowing or a waist in the mid body of the gallbladder that is often associated with reflectors or brightly echogenic reflectors or foci within the wall of the gallbladder.

With this comet tail artifact that we saw earlier in association with cholesterol crystals, that combination of intramural reflectors with a comet tail artifact is virtually diagnostic of the diagnosis of adenomyosis.

Those are cholesterol crystals within these Rokitansky-Aschoff sinuses that I described earlier.

And this segmentation or constriction of the mid body of the gallbladder is also very characteristic of this diagnosis.

There are other masses that can occur.

Of course, these occur much less commonly than cholesterol polyps, but of course, adenomas and papillomas can have a similar appearance.

Adenomas as a rule tend to be sessile and broad-based papillomas tend to be pedunculated and lobular.

They're almost always solitary, usually echogenic and often benign when small.

But we do tend to follow small polyps.

As a general rule of thumb, polyps less than five millimeters are usually dismissed and not followed.

Those between five and 10 millimeters are followed at a six to 12 month interval, and those greater than 10 millimeters are, there's some consideration perhaps for surgery or even closer follow ultrasound follow up.

Here's an example of a polyp now that is reaching a size that surgery should be considered something over 10 millimeters.

Gallbladder Carcinoma

Gallbladder carcinoma is a rare disease, but a devastating one, so one that no one would want to miss.

This carcinoma tends to be a sessile or polypoid mass, if caught early.

More commonly though, the presentation of gallbladder carcinoma is somewhat late.

This is because it tends to be asymptomatic until it is so large and infiltrative that it's causing bile duct dilatation.

By that point, the mass within the gallbladder fossa is usually quite large and has infiltrated or involved adjacent structures such as the liver or possibly the fat.

Oftentimes you will see calcification associated with the gallbladder carcinoma sometimes, and in many cases, stones.

If you were to see something that you suspected to be gallbladder carcinoma, it would be important at the time of the study to look for more distant metastases, such as in the liver adenopathy in the porta hepatis, bile duct dilatation, of course, anywhere proximal to the site of the mass.

Here's an example of gallbladder carcinoma that became apparent late.

You can see it's a solid mass that virtually fills the gallbladder fossa.

That our secondary signs of gallbladder cancer that have been promoted.

People have talked about looking at for discontinuity of the echogenic mucosa of the gallbladder.

Normally, the mucosa lining of the gallbladder is continuous all the way around, but in the case of gallbladder carcinoma, that continuity is disrupted.

Disrupted because remember, the gallbladder carcinoma is a mucosal origin lesion.

Sometimes people have tried to characterize the flow within gallbladder carcinoma.

Suffice it to say that there tends to be abundance of flow, and often that flow can be higher velocity than would be expected in a more benign mass.

And finally, the echogenic speckles that salt and pepper look that I described with cholesterol polyps is absent.

Here is an example of a gallbladder carcinoma.

Here's another with abundance of flow within it.

So putting on color doppler can be helpful in the identification of this mass.

Here's some proximal bile duct dilatation proximal to the mass.

Acute Cholecystitis

Finally, in regards to the gallbladder, I'll talk a little bit about acute cholecystitis.

Of course, this is one of the most common indications for right upper quadrant ultrasound and right upper and a cause for right upper quadrant pain.

I'll talk a little bit about the pathophysiology because the pathophysiology really determines what we're gonna see by ultrasound.

The inciting factor for acute cholecystitis is obstruction of the cystic duct, usually by a gallstone.

Subsequently, the gallbladder fills with bile.

There's a chemical inflammation or irritation of the lining, and the mucosa actually puts out more bile in response.

So you get this mucosal secretion and luminal distension.

That luminal distension causes an increase intraluminal pressure, and so you get a tense and tender gallbladder.

Finally, you get edema within the gallbladder wall because of the inflammation and then secondary bacterial infection in about two thirds of patients.

So here are some ultrasound images that illustrate some of that, those changes, the edema and inflammation of the gallbladder wall, which can either be focal or diffuse.

As a rule, we tend to use three millimeters as the upper limits of normal for the gallbladder wall thickness.

Here is the gallstone that is lodged and immobile within the neck of the gallbladder.

And in this setting, you can see if you look carefully, a small stone here in the gallbladder neck with the, this can be quite difficult to identify, on some patients, if the stone is small, the gallbladder, as I mentioned earlier, tends to become distended, hydropic and tense.

Here's an example of a very distended and hydropic gallbladder.

And finally, you can get pericholecystic fluid at the periphery of the gallbladder, which indicates adjacent inflammation.

Oftentimes, this fluid is intramural, which is to say that you're getting small abscesses within the wall of the gallbladder itself.

Occasionally you will see undermining of the mucosa.

In the setting of acute cholecystitis, you'll see these little membranes that are lifted up, and that's an important sign.

Not often discussed, but an important sign of an acute infection.

If as the disease progresses, you can get a gallbladder full of pus, the so-called gallbladder empyema.

And here you can see the low level echoes filling this very distended gallbladder.

The most important features to keep in mind are the most predictive features of acute cholecystitis are the presence or absence of the sonographic Murphy sign, the wall thickening and the identification of gallstones, particularly if those gallstones or a gallstone appears to be lodged within the neck of the gallbladder.

So those three features alone get you most of the way to the diagnosis.

Secondary signs, gallbladder distension, pericholecystic fluid, and the like, are important confirmatory features.

But the most important three signs are wall thickening, Murphy sign, and stones.

Bile Duct Sonography

Evaluation of the Bile Ducts

Now, just a few words about the bile ducts.

I'll talk a little bit about how bile ducts are evaluated.

Then we'll talk what causes dilatation, wall thickening, and then something about biliary cystic disease.

As a rule, we tend to evaluate the patient with in the left side down, using the liver as an acoustic window.

There are alternative views.

The patient can be supine or upright.

Sometimes you do have to get a little bit creative in identifying the ducts, particularly the distal duct, because that is frequently obscured by bowel gas.

So sometimes we use the left hepatic lobe or even the gallbladder.

It's an acoustic window to see the more distal duct.

In addition, remember that when you move the patient left side down, gas can obscure things because it's going to tend to bring the gas up into the right side.

So sometimes it makes sense to reverse that and bring and put the right side down to move the gas around to see the distal duct.

So looking at for bile duct dilatation, we often can start in the pancreatic head.

This, of course, is the portal confluence and the splenic vein.

This is the dilated duct at the head of the pancreas, usually located posteriorly.

Remembering that the gastroduodenal artery tends to be more anterior in the pancreatic head.

When evaluating cystic or predominantly cystic structures such as the bile ducts, it is important to always remember to use harmonic imaging.

Those tend to bring out and decrease artifacts within the bile ducts and improve the conspicuity of the ducts.

In particular, harmonic imaging reduces reverberation and side lobe artifacts.

And of course, as always, as in the case, we always have to pay attention to the gain settings and the location of the focal zone to get adequate or optimal imaging of the bile ducts.

As with most things, the closer you can get to it, the more clearly you're going to see the structure.

So using strong compression to displace abdominal fat or to see or get closer to the bile ducts is a useful technique.

So here's an example of using harmonics and how that has helped.

This is an example, of course, is the bile duct sitting anterior to the portal vein in this case.

And you can see that this is a much more conspicuous and cleaner appearance with harmonics than it is without the harmonics, where you get all this reverberation artifact within the central duct.

This, of course, can obscure wall thickening and potentially gallstones as well.

So do remember to use harmonic imaging.

Bile Duct Dilatation

Dilatation in the common duct is usually defined by diameters or calibers of six millimeters or greater.

In the intrahepatic duct, it's a little bit harder.

There's less strongly defined criteria.

As a general rule, if you see intrahepatic bile ducts greater than two millimeters, we tend to think about intrahepatic bile duct dilatation.

Remember that the extrahepatic duct, though the criteria is wider.

And as a general rule, somewhere around six millimeters or six to eight millimeters is where people set the threshold for bile duct dilatation.

In the extrahepatic duct, in the setting of bile duct dilatation, you can have, of course, gallstones in the extrahepatic duct.

But remember that these stones can also form or reflux into the intrahepatic ducts, and those can be quite confusing because it can look for all the world like air.

But if you're paying careful attention, you can see the small bile ducts filling the dilated bile channels within the liver itself.

So approximately 20% of common bile duct stones will not shadow.

Remember, these are quite small, and one of the principle determinants of shadowing is size of the stone.

One could use, one could seek out twinkle artifact using color doppler imaging as a helpful adjunct to the diagnosis.

And most people who have that capability will use color doppler to look for the twinkle artifact behind occult stones.

Obstruction is distal in about 90% of cases.

Stones can be particularly hard to identify distally as bowel gas tends to obscure the distal duct.

Measurement of the hepatic duct is usually done in the proximal duct near the crossing of the hepatic artery.

Classically that measurement is an inner to inner diameter.

This is frequently mismeasured as a wall to wall or even an outer to outer measurement.

But remember that the initial tables that identified this six to eight millimeter threshold depended on an inner to inner measurement.

So the cursor should be on the inside of the duct.

In both cases, harmonics is essential compression where you need to do it and remember to always adjust your focal zone appropriately.

There has been some controversy about whether duct diameter can exceed the six to eight millimeter threshold in settings where the patient ages.

It is my belief that it certainly does increase with age, and patients over 50 and certainly 60 or 70 years of age often have slightly more dilated bile ducts than the remainder of the population.

In addition, in patients who have had a cholecystectomy, the common bile duct can take on a reservoir function and be distended with bile simply because the gallbladder, which would have stored the bile, is no longer present.

Then there are other reasons for bile duct dilatation, sphincter of Oddi dyskinesia.

Sometimes people have talked about pregnancy as being associated with ductal dilatation as well.

It is always important to remember the dilated ducts are not necessarily obstructed and obstructed ducts are not necessarily dilated in the early stages of bile duct obstruction.

Certainly within the first 24 hours, the bile ducts may not dilate, and that is particularly true of the intrahepatic ducts, because dilatation tends to progress from the extrahepatic to the intrahepatic ducts.

You can also, of course, get incomplete, or intermittent obstruction, you can get stones that have already passed and the obstruction can start to subside.

And of course, there are cases where the obstruction is due to fibrosis of the walls as in sclerosing cholangitis.

And in that case, you may not get ductal dilatation because there is not the compliance of the ductal wall that it would allow that dilatation to occur.

As I said earlier, extrahepatic bile duct dilatation precedes intrahepatic bile duct dilatation.

The threshold is usually in the six to eight millimeter range in the proximal duct.

Most people will start talking about abnormality greater than eight millimeters.

Some people advocate 10 millimeters, but these are very similar measurements.

Many of these threshold studies were done very early in the development of ultrasound, some dating back to the late seventies or early eighties.

So there are variable threshold values that are advocated in the literature.

If you do read the literature and want to adopt someone's criteria, remember to be careful about where they're doing the measurement, what patient population they are working with, and whether or not they have controlled confounding variables such as age and the presence or absence of cholecystectomy.

There has been in the past some enthusiasm for using fatty meals to look for the contraction of the gallbladder and the decrease in the size of the ducts.

In my own experience that enthusiasm has waned, and we rarely do fatty meals to assess for bile duct dilatation.

Now, it is also possible that after a passage of a stone that the elasticity or the compliance of the duct can be damaged and the duct can become necessarily larger and more dilated simply because the bile duct does not have the same elastic properties that it had earlier.

And this could possibly explain why the bile duct tends to increase with age, because as the bile duct ages, so as the patient ages that elasticity can be compromised.

Here is an example of a dilated bile duct here sitting anterior to the hepatic artery.

And of course, the portal vein, it's back here.

This is the dilated duct itself.

So in the setting of bile duct dilatation, here is the differential diagnosis.

Most commonly, it's gonna be due to choledocholithiasis or gallstones within the bile duct.

Of course, we always have to be concerned about the presence of masses, both internal and external to the bile ducts.

A common example of external mass causing bile duct dilatation would of course be gallbladder carcinoma, as we saw earlier, but also pancreatic carcinoma.

Intraluminal masses such as cholangiocarcinoma, are ductal by definition and cause dilatation proximal to their occurrence.

Sclerosing cholangitis or AIDS cholangitis can cause bile duct dilatation, porta hepatis obstruction either hepatic metastasis or lymphadenopathy.

Occasionally you can see cases of Mirizzi syndrome where a gallstone impacted within the gallbladder neck causes extrinsic compression of the common hepatic duct and upstream dilatation.

And finally, less commonly pancreatitis can cause milder degrees of ductal dilatation, choledocholithiasis.

The detection of choledocholithiasis, particularly distally in the duct, is widely variable.

Depending on what study you read, it can be as little as 40% and as much as 70%.

Suffice it to say that to identify distal stones, a significant amount of effort needs to be expended to see that distal duct clearly.

As a general rule, the more dilated the duct is, the easier it is to see the stone as one might expect.

And this is the setting where the fatty meal may be helpful, but rarely performed anymore.

Here is an example of a gallbladder full of gallstones dilated ducts.

So you may suspect the presence of choledocholithiasis.

And as you follow the duct down, you can see the stone here, which in this case does not shadow convincingly, but is unequivocally present.

Couple more examples of a dilated duct proximally that is traced to a small stone here distally.

This could be a small soft tissue mass.

There's no way of telling in something this small.

And another small stone within the distal duct.

Pitfalls in the diagnosis of choledocholithiasis include surgical clips adjacent to the duct vascular calcifications, biliary air, or pneumobilia and partial volume averaging of bowel gas.

Bile Duct Wall Thickening

Wall thickening of the bile ducts can occur in many different circumstances, some degree of cholangitis, either ascending cholangitis or more commonly in our population, sclerosing cholangitis.

This is of course found in associated with ulcerative colitis in about 50% of cases, but sonographically, you'll see wall thickening luminal tapering.

Sometimes you'll see areas of beading where there is bile duct dilatation, and then constriction.

And those areas of dilatation can contain pus or sludge or sloughed epithelium because of the obstruction of the ducts and the collection of this material.

Here's an example of sclerosing cholangitis with intrahepatic bile duct dilatation.

Here's an example of the same patient you can see as we're getting into the bile duct.

Again, just to give you the anatomy, this is the gallbladder.

This is the duct hepatic artery portal vein, but the duct here now is filled with intraluminal echoes and some of that resulting from wall thickening.

More examples of cholangitis, wall thickening, sometimes that wall thickening can be quite severe.

Here's some very distinctive wall thickening of the bile duct.

Remember that the bile duct wall is virtually invisible to us on ultrasound when normal.

Here's an example of an ERCP, retrograde injection of contrast into the bile duct, and you can see that area of narrowing and widening and narrowing and widening.

Pus can form, as I say, or collect behind areas of stricturing, and you can see that as low level echoes within the lumen of the bile duct itself.

Cholangiocarcinoma

Cholangiocarcinoma is sometimes a difficult diagnosis.

There are predisposing conditions that would raise your level of suspicion.

Of course, ulcerative colitis sclerosing cholangitis, biliary cystic disease.

In some parts of the world, liver flukes and some occupational exposures have been associated with cholangiocarcinoma, and those include work in the aircraft and auto industries as well as chemical, rubber and wood finishing products.

There are two types of cholangiocarcinoma, the so-called peripheral type and the so-called central type.

These are distinctions based on imaging rather than pathologic differences.

The peripheral types tend to be quite large.

They're more common type in the United States.

They can be seen as either hyper or hypoechoic, and they often arise from the smallest bile ducts at the periphery of the liver.

The peripheral cholangiocarcinoma can be nodular, but more frequently you see it as an infiltrating process.

The nodular form, as a rule, is more common and has a distinct right lobe predilection.

The infiltrating form of the peripheral carcinoma is relatively uncommon, and is seen as diffusely abnormal liver echo texture, and can be very difficult to identify if it is infiltrating only, as a rule, because of the growth of the cholangiocarcinoma being relatively slow, there is no hypoechoic halo around those particular masses.

And the dilatation of the bile ducts peripheral to the mass tends to be very characteristic and very helpful in my experience in distinguishing cholangiocarcinoma from hepatocellular carcinomas.

Again, the important feature here is at the cholangiocarcinoma, is a ductal tumor, and being in the ductal tumor, the presence of proximal bile duct dilatation is a critical and important feature to recognize.

So finding the bile duct dilatation and tracing it more centrally and looking for a mass is usually the process involved in diagnosis of cholangiocarcinoma.

So as we trace this down, you can see the dilated intrahepatic ducts have become dilated extrahepatic ducts, and following that, we can see the soft tissue mass more distally, and that is the hallmark of cholangiocarcinoma.

If confirmation can be found with MRCP or ERCP, depending on institutional preference.

Hilar cholangiocarcinoma, the so-called Klatskin variety of it tends to cause obstructive jaundice early.

They often are difficult to identify by imaging because of their relatively small size, they're often small nodular masses that infiltrate along bile duct walls.

Occasionally they're papillary and they're often associated with atrophy of the involved hepatic lobe.

These are very difficult tumors to treat because surgery is usually not an option for these patients.

In particular surgery is precluded if there is involvement of both sides of the liver, both the right and left sides of the liver, or the presence of hepatic or peritoneal metastasis.

So staging requires assessment of the bile ducts, of the vessels, and of adjacent lymph nodes, particularly those lymph nodes around the pancreas or between the pancreas and the duodenum.

Of course, most of those sort of surveys will be done with CT or MR.

Biliary Cystic Disease

Finally, I'll talk a little bit about biliary cystic disease choledochal cyst.

The etiology is unknown.

There has been some speculation that it is a consequence of reflux of pancreatic enzymes into the bile ducts and causing some bile duct wall destruction and dilatation.

There typically subtype as cystic segmental or fusiform ductal dilatation, and outpocketing or diverticulum, a choledochocele, which is an invagination of the distal duct into the duodenum.

And finally, multiple intra and extrahepatic cysts.

This is a typical choledochal cyst, frequently seen as a saccular diverticulum from the common duct.

Here.

Sometimes you can see the origin or the neck of the choledochal cyst as it points to the common duct.

And there is the common duct in this setting.

Sometimes CT or MR can be confirmatory or helpful in this diagnosis.

Remember that you do not want to confuse the gallbladder itself for the choledochal cyst, and you frequently you'll see these as two separate structures.

Summary

So in summary, I've talked about certain features of the gallbladder and the bile ducts.

We've talked about gallstones, wall thickening, and acute cholecystitis, as well as bile duct dilatation, wall thickening, and cystic change.

Thank you for your attention.