0:01

This case is a young lady in her 20s

0:03

who is being evaluated as a liver donor,

0:06

so we are being asked to look at her MR imaging.

0:10

She's also getting CT imaging, which I will not

0:12

show you, but we're looking at her MR imaging

0:15

to evaluate some of her biliary anatomy prior

0:18

to her potential consideration as a liver donor.

0:22

So we'll start off with the T2-weighted

0:23

sequences, even though in this instance,

0:25

I don't think it's as useful, but I

0:27

just want to show you how we sort

0:30

of use it, if at all, or what the utility

0:32

could be to evaluate the biliary anatomy.

0:34

So T2-weighted sequences,

0:35

everything looks pretty good.

0:36

This is a healthy patient.

0:38

You know, we're asked to look at the

0:39

bile ducts, and it's very challenging

0:42

to look at the biliary tree.

0:43

We see no dilatation of the biliary tree.

0:45

This looks, this is the extrahepatic

0:47

biliary tree; the common

0:48

bile duct looks in normal caliber.

0:49

The intrahepatic bile ducts are very,

0:51

very small, which is a good thing.

0:54

It means that they're normal, but it doesn't

0:55

quite give us the anatomy that we need to see

0:59

in order to tell the surgeons what's going on.

1:01

We often do MRCP sequences as well to

1:03

try to evaluate the biliary tree.

1:06

In my own experience, sometimes

1:08

they come out great.

1:08

A lot of times, again,

1:10

they're quite limited.

1:11

And this one is an MRCP sequence

1:12

in a coronal plane.

1:15

We can see that there's high T2

1:17

hyperintense fluid in the CSF,

1:18

something in the stomach as well.

1:20

But again, the bile ducts are

1:21

very, very tough to see over here.

1:23

So if we were to just use our T2-weighted

1:25

sequences and MRCP sequence, I think

1:28

we'd be in trouble here and we would have a

1:30

tough time telling the surgeons what they needed

1:32

to know in terms of the discrete anatomy.

1:34

So we use intravenous contrast

1:36

with an agent with partial

1:38

hepatobiliary excretion called Eovist.

1:40

And we wait at different time

1:42

points: 10 minutes, 15 minutes,

1:44

20 minutes, 30 minutes as well.

1:47

At some of the later time points,

1:48

you're going to start to see contrast

1:49

that's excreted through the bile ducts.

1:51

on your post-contrast sequences.

1:53

And it's going to be those sequences

1:55

that we use in order to identify

1:57

its discrete biliary anatomy.

1:59

So this is a post-contrast sequence after

2:02

giving Eovist, and I'm just going to zoom up

2:03

a little bit over here, magnify, just so you

2:05

can kind of see what we're talking about.

2:08

And as I scroll through these

2:09

images, just want you to get a

2:12

sense of what you think is going on.

2:14

And there's a very, very

2:16

subtle anatomic variation here.

2:19

And so, as mentioned in the normal

2:21

anatomy case, the right hepatic duct

2:23

is composed of an anterior

2:25

branch and the posterior branch.

2:27

Over here is the anterior branch and

2:31

over here is the posterior branch.

2:33

Here is the left hepatic duct.

2:36

What we notice is that the posterior

2:38

right hepatic duct is actually draining

2:40

directly into the left hepatic duct.

2:44

The anterior branch still hasn't drained

2:45

in, but it's coming downwards now.

2:49

The posterior is still draining into the left.

2:51

The anterior branch hasn't come in yet.

2:53

And right there is when the

2:54

anterior branch comes in.

2:57

Let's view this in the coronal plane.

2:59

Again, I'm going to magnify

3:01

here is the left hepatic duct.

3:03

This is the anterior branch

3:04

of the right hepatic duct.

3:06

And right over here is another bile duct.

3:08

And that's actually going to be

3:11

the posterior right hepatic duct.

3:13

You see how it's going posteriorly

3:14

into the right hepatic lobe.

3:16

It's draining from this, coming upwards,

3:17

coming upwards and draining right into

3:19

that left hepatic duct before then meeting

3:21

the anterior hepatic duct and forming

3:24

the common hepatic duct over here.

3:26

And so I wanted to show this because

3:28

we will often see anatomic variations.

3:31

And when you do see anatomic variations, this

3:33

one is relatively common, by some

3:36

estimates seen in about 15 percent of cases.

3:39

And so when I look at patients and

3:41

they're asking me to look at biliary

3:44

variations, this is the first one that I

3:45

look for because it's relatively common.

3:48

And so specifically, it's when the right

3:50

posterior duct drains to the left duct,

3:53

rather than joining the anterior hepatic

3:56

duct and forming the right hepatic duct.

3:57

And so this is a common anatomic

4:00

variation seen in our patients.