0:01

So this case is a 35-year-old female,

0:03

and the history is follow-up bile abnormality.

0:06

So we're going to go right to it and look

0:07

at the biliary tree and see what's going on.

0:09

Axial T2 image here, coronal T2 image here.

0:12

I think that'll be sufficient

0:13

to see this abnormality.

0:15

If you scroll through, we're already

0:17

starting to see some of the left

0:17

hepatic ducts that are dilated.

0:20

You can see down some of the right hepatic

0:22

ducts that are dilated, but they're

0:23

really just ballooning outwards, right?

0:25

So unlike some of the other areas of ductal

0:28

dilatation we've seen here, we have really

0:29

sort of cystic and almost fusiform dilatation

0:33

of some of the intrahepatic bile ducts.

0:35

As you follow it, you can

0:36

see quite large over here.

0:39

And this is the extrahepatic

0:40

biliary, also looks quite abnormally

0:43

enlarged, right, right over there.

0:45

And as you go downwards, relatively

0:48

normal caliber as you go towards

0:50

the distal CBD over here.

0:53

Let's look at it on the coronal

0:54

images, and I think it'll give you a

0:55

good sense of what's happening here.

0:57

Dilated bile ducts on the

0:59

left side, on the right side.

1:00

Quite a fusiform and cystic dilatation.

1:04

Similar appearance really

1:05

involving the common hepatic duct.

1:06

Some of the common bile

1:07

duct is also quite dilated.

1:09

And then as you go more distally, the common

1:11

bile duct is relatively normal in caliber.

1:15

So what you're seeing here is dilatation of

1:17

both the intrahepatic and extrahepatic bile ducts.

1:20

Bile ducts, the sort of cystic dilatation

1:23

of both those segments of the biliary

1:25

tree, and the appearance is quite

1:27

characteristic of a choledochal cyst, and

1:30

specifically of a type 4 choledochal cyst.

1:34

So choledochal cysts, as we've talked

1:35

about in a few cases, are congenital

1:37

cystic dilatations of the bile ducts.

1:39

There's a variety that we see, you

1:41

know, type 1 is the most common.

1:43

Type 2 represents a small diverticulum

1:45

off the extrahepatic bile ducts.

1:48

Type 3 is when you have that cystic

1:49

dilatation within the intraduodenal

1:52

segment of the extrahepatic biliary tree.

1:54

And type 4 is when you have involvement of

1:58

both the extrahepatic and intrahepatic bile ducts.

2:01

Now, I'll qualify that by saying type

2:03

4, there's actually two varieties.

2:06

Type 4a, which is what this is, has involvement

2:08

of both the extrahepatic and intrahepatic bile ducts.

2:11

And type 4b is when you have multiple

2:14

discrete areas of cystic dilatation

2:17

involving only the extrahepatic biliary

2:18

tree and the intrahepatic biliary ducts,

2:20

without involvement of the

2:21

intrahepatic bile ducts.

2:23

And so that's just sort of something that one

2:26

needs to know about, learn about, can look up

2:28

whenever they see these sorts of abnormalities

2:30

to remember how to best qualify them.

2:32

But this instance where we have

2:33

cystic dilatation of both the intra

2:35

and extrahepatic biliary tree, this is

2:37

compatible with a type 4a choledochal cyst.