0:01

So this case is of a patient, 55-year old

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gentleman with a cystic mass seen

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on an ultrasound for which an MRI

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was requested for further evaluation.

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And we're going to start off with

0:12

our axial T2-weighted image over here.

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And as we scroll downwards, notice

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that the bile duct is dilated, not a

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lot of intrahepatic ductal dilatation.

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This itself, we're going to look at

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it as probably actually going to be

0:27

a portion of the common hepatic duct.

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And as you go downwards, look how

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it just sort of balloons outwards.

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Really large extrahepatic biliary tree.

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This is a common bile duct at this instance,

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and sort of then tapers downwards again.

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We can see it on the coronal

0:45

T2-weighted image as well.

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Quite dramatic cystic dilatation

0:51

of the extrahepatic biliary tree.

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A little bit involved in the common

0:55

hepatic duct over here as well.

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This is the left hepatic duct that

0:59

looks relatively normal in caliber.

1:00

That's the right hepatic duct

1:01

that looks normal in caliber.

1:03

But really beyond that, the common hepatic

1:05

and the common bile ducts are quite dilated.

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We're not seeing any filling defects

1:11

inside of them, and they can be

1:13

followed fairly nicely to the ampulla.

1:16

This is a coronal MRCP image, again,

1:19

showcasing the same findings of dilatation

1:21

of the common hepatic and common bile

1:22

ducts with the intrahepatic duct is

1:24

relatively normal in caliber, the left

1:27

one over here and the right one over here.

1:30

And so this entity is highly, highly suggestive

1:34

of something called a choledochal cyst.

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And we're going to spend a few cases talking

1:41

about the different types of choledochal cysts.

1:44

But the big picture here is that

1:46

overall, we're not really sure why these occur.

1:49

It's an unclear etiology, but what

1:51

they present is some sort of cystic

1:53

dilatation of the bile ducts.

1:54

It's thought to be congenital.

1:56

It's more often seen in

1:58

patients of Asian descent.

2:00

It's more often seen in females.

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And, you know, often it's diagnosed

2:03

in infancy, in childhood.

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This patient is a little bit older, at 55.

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We don't often see it this late out.

2:10

There are some complications associated with

2:11

all choledochal cysts that we need to know about.

2:14

Because you have these ballooning and cystic

2:17

dilatation, you have areas of relative stasis

2:19

that can result in the formation of stones.

2:22

Biliary stasis can also result

2:23

in superimposed cholangitis.

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But more importantly, or perhaps most

2:27

importantly, these patients are also at risk for

2:29

developing cancer, that is cholangiocarcinoma.

2:32

As I had mentioned, there are different

2:33

types of choledochal cysts, which we're

2:35

going to go through some of them.

2:37

This happens to be a Type 1 choledochal

2:40

cyst, and this, by the way, is

2:41

based out of a classification system

2:43

known as the Todani classification.

2:46

And Type 1 choledochal cysts are the most

2:48

common, and they represent a fusiform or cystic

2:51

dilatation of the extrahepatic biliary tree.

2:54

They are further classified as associated

2:58

with like a Type 1a, Type 1b, Type 1c.

3:01

I'm not going to go into those details

3:03

simply because I don't have good examples

3:05

of them, but that's something that you

3:06

should know about and you can read about

3:07

if something that your referring providers

3:10

would like you to know at your institution.

3:13

But when you see the sort of fusiform or cystic

3:16

dilatation of the extrahepatic biliary tree,

3:19

it sort of just balloons outwards like this.

3:21

You’ve got to think of a choledochal cyst.

3:23

In this instance, this turned out to be a Type I

3:25

choledochal cyst, which is the most common type.