Advancing Age, Cholecystectomy and the Bile Duct Diameter - HD

Introduction

Hello, my name is Mindy Horo.

I'm a radiologist in Philadelphia, Pennsylvania.

I work at the Einstein Healthcare Network.

Today it is my pleasure to speak with you about the common bile duct.

The title of this talk is Advancing Age Cholecystectomy and the Bile Duct Diameter.

This is something that people who do ultrasound imaging have looked at, discussed, studied, debated for many years.

And it's interesting that after all this time we still come back to the discussion of what measurement can we rely on as normal?

Why is this so important? Obviously if you're going to be able to diagnose biliary dilatation, you have to figure out what size duct is normal or abnormal.

The questions that we are going to discuss today are as follows.

Does the normal bile duct dilate with age? Number two, does the normal bile duct dilate after cholecystectomy?

And the third thing that we'll talk about, which clearly is an outcome and related to the first two, is what is the significance of a dilated bile duct or something that we think is dilated without any imaging explanation?

Does the Normal Bile Duct Dilate with Age?

First, does the normal bile duct dilate with age?

This is important.

You need to know if it changes with age and what is normal at 80 may not be normal at 20.

So is this the case?

To understand the problem, we're gonna go back a little bit into ultrasound history.

In the early years of ultrasound, many papers published in the early eighties looked at cohorts of 200 to 300 to 400 patients.

And this initial paper in 1983 showed a small gradual increase in bile duct size with age.

The cohort looked at patients between 20 and approximately 70 years and showed a minimal increase.

This was followed in 1984 by a somewhat landmark paper that was published in the Journal of Clinical Ultrasound.

This cohort was 256 patients and they had a range of ages that included pediatric patients up to 70 years of age and found that the duct size varied from one to 10 millimeters, age dependent.

They had a logistic regression analysis.

But you need to remember that the inclusion of a pediatric cohort forces this regression analysis to show a significant effect of age based on this paper.

However, people began to feel that the duct clearly and logically and progressively increased with age.

And in one of the additions of the major diagnostic ultrasound text by Rumack, the chapter in 1998 said as follows, A simple rule of thumb is to consider as normal a four millimeter mean bile duct diameter at age 40, five millimeters at 50, six millimeters at 60, and so on.

And that's a very nice thing to be able to remember.

And that was published and people began to use that clinically.

I had started practicing before that text was published and it didn't seem to always make sense with things that I saw clinically.

And this would be an example of this.

This was a portable study we had done on an 83-year-old patient in the ICU.

Her common hepatic duct is measured here at an 8.1 millimeters and there was maybe minimal intra hepatic biliary dilatation.

We were unable to image the distal bile duct.

So do we say that this is normal? Don't do anything else.

Do we say it's a little bit abnormal?

Do we say it's a lot abnormal?

Obviously it depends a little bit on her clinic or somewhat on her clinical findings.

And those were abnormal.

So this patient went on to an MRCP and as you can see in the distal common bile duct, there is a calculus.

So here's a case of an eight millimeter duct in an 80-year-old woman and this is clearly abnormal with an important cause.

So the issue of bile duct size didn't go away with those articles in the eighties and it was revisited in the 21st century.

A large PA cohort was published in 2000, which again showed an increase in size in this relatively elderly cohort, but a much lower in a smaller increase.

And they found in conclusion that although the duct did increase slightly with age, the vast majority of the ducts in this population, which was older than the other paper were less than seven millimeters.

Our group published a cohort in 2001.

We were interested in could we reproduce that linear regression analysis of one millimeter per decade.

Our cohort had patients from 20 to 92 and we measured the duct at the mean duct diameter, at the proximal mid and distal portions and saw a slight increase, towards the more distal duct.

And we noted a slight increase in age that was not statistically significant, but disproved the one millimeter per decade by 2003, another paper also showed slight increase every 10 years less than the one millimeter and they recommended 8.5 as an upper limit of normal.

By this point, the next edition of Rumack had changed the conclusion to say that the normal caliber of the bile duct in patients without disease is up to six millimeters by most studies.

And there is controversy of whether the duct widened with age and whether it widened with cholecystectomy.

And so they concluded that even though there could be normal diameters of up to 10, the vast majority of bile ducts were less than seven millimeters and anything greater should prompt further investigation, especially if there were clinical findings.

And so the story progresses, more recently again, people have been looking at the common bile duct both with ultrasound and with CT and endoscopic ultrasound.

And several good studies have been published, which again show slight increases in bile duct diameter with age, but at a much slower rate than was originally published many years ago.

And some of these people are well known in the ultrasound world.

So both by ultrasound and ct, there probably is a slight increase in bile duct size in the 0.2 to 0.3 range per decade, over time.

So we will conclude that there is slight dilatation of the bile duct with age.

It is a very small amount and that even with great advancing age, most bile ducts are less than seven millimeters.

Here are some important things to remember.

However, we are measuring the common duct at the porta hepatis.

So it's really the common hepatic duct.

The mid and distal duct could be a millimeter or two larger ultrasound measurements should be performed from inner to inner and from anterior to posterior.

Lastly, a normal bile duct diameter does not exclude obstruction and in addition, even a small bile duct diameter should be considered suspect and may be abnormal.

So those are the other side of the coin.

Let's look at some examples.

This is a 63-year-old patient she was having right upper quadrant pain.

Her common duct being measured in the upper left image is 3.4 millimeters, perfectly normal.

In front of the portal vein, she does have csis.

This is her gallbladder with multiple tiny calculi, little bit of adjacent fluid, and this is a transverse view of the distal common bile duct in the head of the pancreas.

It's not significantly enlarged, but there is a small calculus sitting right there.

This was her CT performed earlier at which time the stone in the gallbladder was noted.

This, as you can see on the arrow, was her common bile duct and the tiny little calculus there was not noticed.

It wasn't calcified, it was just slightly increased soft tissue density.

So here we have a normal bile duct with a distal stone.

This is an example of the bile duct that's too small.

So I put this ultrasound, turned it to make it the same as the patient's MRCP and subsequent ERCP here, the bile duct, the proximal duct was top normal.

It was about six millimeters.

The distal duct was only two millimeters and in between there was some soft tissue and you can barely see the lumen of the duct.

It had narrowed down completely.

Again, this is the same area on the MRCP and on the ERCP.

Of course the ultrasound allows you to see the soft tissue density that is causing this benign stricture.

So very small duct because of a benign stricture.

Lastly, here's a bile duct that was measured at top normal, almost essentially seven millimeters.

But look at the appearance of the duct.

This is a duct that is not correctly measured.

If you notice, it looks like there's something inside of it, two little parallel echogenic lines.

Well actually this bile duct lumen should have been measured from one of those lines to the other because this represents thickening an edema of the gallbladder wall.

This is the mucosa and the residual lumen is barely two millimeters.

This patient had primary sclerosing cholangitis, so it's not just enough to measure the duct.

You need to look at the duct, make sure you're measuring the correct thing.

And some situations such as this can be a little bit tricky for a correct measurement.

One last thing to consider is the rapidly changing bile duct.

And this is a phenomenon that you may see from time to time.

This patient came with right upper quadrant pain.

We initially imaged and found a distended gallbladder with calculi.

The patient had acute cholecystitis at this time, the extra hepatic bile duct was perfectly normal, nice and smooth and thin tapering into the head of the pancreas.

The patient continued to have symptoms.

Eight hours later this is what the common bile duct looked like and you can see three small calculi sitting in the duct.

The take home message here is that the second duct was still within the range of normal, but the duct has calculi in it.

It is not just enough to go to the porta hepatis and measure the bile duct.

You need to do a good survey trying to image the entire duct and looking inside it, looking for external compression, thickening of the wall, thickening of the mucosa, et cetera.

Lastly, this is an example of an ovoid bile duct at the head of the pancreas.

If you had just measured from side to side, you would've called it dilated at nine millimeters.

But the AP measurement is perfectly normal.

Does the Normal Bile Duct Dilate After Cholecystectomy?

Now we'll turn to the second major topic and that is what happens to the bile duct after cholecystectomy.

This has also been studied over time.

In general, people have had varying opinions on whether the bile duct dilates after cholecystectomy.

An original older paper by Paul in 1935, a surgical paper showed significant dilatation with time, after cholecystectomy, though this was debated in the early eighties in which papers came out showing minimal or no dilatation.

This was followed in the nineties and then more recently by papers which clearly show both on ultrasound and CT that there is dilatation of the bile duct after cholecystectomy.

The major conclusion one can take from these papers is mild dilatation can occur with cholecystectomy, not necessarily, but especially occurs in the combination of advancing age and cholecystectomy and the longer the time from the cholecystectomy to the imaging.

This is an example of a 27-year-old female.

On the left is her bile duct at the time of acute cholecystitis, right before her cholecystectomy when it measured three millimeters.

One year later after her cholecystectomy, she came for re-imaging for some other reason and the bile duct was 5.3 millimeters.

It did taper to normal but it was slightly larger, otherwise normal.

And she had normal liver function studies.

These are two different patients with distant cholecystectomy greater than 10 years.

This patient is 98 years old, the duct is four millimeters here, it dilates a little bit to seven millimeters.

This patient who's younger at 53 5 millimeters here, almost 11 millimeters here, neither of them had any further distal bile duct pathology.

Significance of a Dilated Bile Duct Without Imaging Explanation

Let's now turn to the issue of if you see a duct that you would consider dilated based on what I've told you, but you absolutely cannot find a cause on imaging.

And that imaging includes ultrasound, CT ERCP MRCP, any of these kinds of things, we cannot find a cause.

What might be the etiology if there is one?

If you look in the literature, there are a variety of papers in the clinical literature usually looking at this issue and typically using endoscopic ultrasound, which would be considered sort of the end of the line procedure.

When you look at the data from these, you have to look very carefully.

There are sub selected groups of patients.

Many of them have symptoms and I don't know how applicable it is to the entire population, but it does give you an idea of the kinds of etiologies that you might find in some of these patients.

What might be found. So if you look down this list here, you can see that there are more findings when patients have abnormal liver function studies than when they don't.

I don't know how they convince patients with totally normal liver function studies and nothing on imaging to have endoscopic ultrasound, but some people obviously did.

So from time to time you'll find some calculi.

People find periampullary diverticula and it's a little bit controversial as whether that's really a cause of the dilatation, but nonetheless we find it, occasionally some benign strictures, pancreatitis, once or twice there may be a pancreatic carcinoma.

You have to take these all with a grain of salt as the ones that have tumors.

But basically there's not a lot to find.

And if you do find something, it's generally a benign issue.

We can sometimes suggest some of these diagnoses.

This is a patient with this top normal sized bile duct and as you come along the end, it almost looks like there's some gas nearby or almost in this bile duct.

But there was no gas elsewhere in the biliary tree.

And on ct you can see this is the gas filled juxta ampullary diverticulum sitting right next to the bile duct.

And maybe it's compressing it a little bit.

If you look at this reformatted image, another patient 42 years old who happened to have cirrhosis, slightly dilated bile duct.

And this is the diverticulum, slightly squashing perhaps the bile duct.

Some patients probably just have a fusiform shape of their bile duct.

And you have to be careful. We think this might be actually a form of a choledochal cyst in which at the porta hepatis, the bile duct is normal and then it smoothly dilates and often tapers in this case where you can see the whole bile duct, it's normal, slightly dilated, and then tapers absolutely nothing else wrong.

Probably no reason to do anything more in this patient.

So in the clinical literature, they conclude that if the patient is truly asymptomatic and has normal liver function studies, but a slightly dilated or somewhat dilated bile duct, you can probably just follow them clinically before doing any more imaging.

Conclusion

So in conclusion, what number can we use to best discriminate normal from an obstructed extra hepatic bile duct?

I think we can go back to a very nice editorial written by Dr. Bowie in 2000, in which he concluded that the vast majority of normal extra hepatic bile ducts will be less than seven millimeters.

And that is when you do an AP measurement of the common hepatic duct at the porta hepatis.

And this is regardless of age and cholecystectomy.

Thank you.