0:01

So let's move into some abdominal vascular applications.

0:04

Understanding normal liver Doppler is critical, because not only is that important

0:08

for a huge subset of the population, transplant imaging is going to depend on it as

0:12

well.

0:14

So the liver is unique. About 75% of the blood supply to the liver comes from the

0:18

portal vein, and 25% comes from the hepatic artery.

0:21

Importantly, the hepatic artery is one of the areas that perfuses the biliary

0:25

tract, so you always want to think about those things potentially going hand in

0:29

hand. So let's look at some normal waveforms.

0:32

So the portal vein waveform has what we call continuous hepatopedial flow, meaning

0:36

flow going towards the liver at all times.

0:39

This should have a waveform that looks pretty non-phasic.

0:43

Sometimes it has a little bit of an up and down flow, but essentially it should be

0:47

relatively flat as you go along. We shouldn't see any big significant changes.

0:53

If we do see a significant phasicity to the flow, that can be an indicator that the

0:57

patient has cardiac dysfunction, typically a right heart cardiac dysfunction.

1:01

It's a low velocity system, so it goes from about 20 to 40 centimeters per second,

1:06

and that's to be expected. The hepatic veins are a little bit different.

1:10

So the hepatic veins do have a respiratory variability, and so we have what is

1:15

called a triphasic waveform, and so there are different portions of that waveform

1:19

called the S, the D, and the A portions.

1:21

What you want to know is that this is the baseline of what you expect to see.

1:26

As we move along and we start to bring some pathology into the mix, specifically

1:31

things that might cause the liver to be increased in stiffness, for instance, we

1:36

start to lose some of that phasicity because you don't have that normal flex in the

1:39

vessel and in the surrounding tissue.

1:42

So once we start to lose some of this phasicity, whether that's losing from just an

1:48

up and down portion alone or actually losing the below the baseline portion, that

1:54

is varying degrees of what we would call monophasicity or lack of phasicity in the

1:58

waveform. And then finally, the hepatic arteries.

2:02

So the hepatic artery, as we've mentioned with other structures, are low resistance

2:06

vessels. We are perfusing a liver. We always want forward flow towards it.

2:11

And you can see we have that standard low resistance waveform with a relatively

2:15

prominent end-diastolic velocity.

2:17

And like other structures, the resistive indices here should range from 0.5 to 0.7

2:23

or so.