So in this lecture we will be discussing benign liver disease.
It's important to recognize benign liver disease findings
so that you can help differentiate it from malignant liver disease
and malignant liver lesions.
So let's take a look at these CT images.
This patient came in and had an abdominal and pelvic CT scan
and we saw this lesion within the liver as an incidental finding.
Take a look at these images and see what you recognize.
As we go through the lecture keep these in mind
and we'll go back to it at the end.
So benign liver abnormalities can be both focal or diffuse,
focal abnormalities include cavernous hemangioma,
hepatic cyst, focal nodular hyperplasia and hepatic adenoma.
Those are the most common benign liver abnormalities that are focal.
There can be multiple diffuse liver abnormalities as well,
including hepatic steatosis which is also known as fatty liver,
hepatitis metabolic liver disease, iron overload
and autoimmune disease of the liver.
The one that will be discussing today of the diffuse category
is the hepatic steatosis because that's really the only one
that can be diagnosed just based on imaging.
So let's take a look at hepatic steatosis.
It's a very common diffuse benign abnormality of the liver.
It's caused by accumulation of fat in the hepatocytes
and it could be diffuse or focal. It’s usually seen as a diffuse abnormality
but occasionally it can be focal as well,
and often is associated with either diabetes or obesity.
So this is an example of an ultrasound in a patient that has hepatic steatosis.
You can see a diffusely echogenic slightly heterogeneous liver.
This right here I'm outlining is the liver.
Usually, the liver parenchyma should be approximately equal to that
of the renal cortex which is right here.
On this image you can see that the renal cortex is actually quite a bit darker
than the liver and that tells you that there’s a hepatic steatosis.
Hepatic steatosis can also be diagnosed on MRI.
These are two MRI images demonstrating hepatic steatosis.
So in this first image we have the liver with a normal appearance.
A little bit brighter than the spleen, here we have the liver
and here we have the spleen, on opposed phase imaging
the liver demonstrates loss of signal. So again here's the liver,
it's a little bit darker than it was on the in phase image over here.
And the spleen remains approximately the same.
So hepatic steatosis is best evaluated on chemical shift imaging on MRI
and what we just saw the in phase and the opposed phase
is an example of chemical shift imaging.
So the in phase imaging demonstrates normal signal intensity of lipid
containing structures, while the out-of-phase or opposed phase imaging
results in loss of signal in lipid containing tissues.
So chemical shift imaging it's really based on the very magnetic properties
of lipid and water and it's very useful in identifying structures that contain lipid.
So when we discussed focal liver lesions,
the most common that comes to mind is the cavernous hemangioma.
It's usually solitary, it may be multiple
and if it's less than 2 cm in size is called a capillary hemangioma.
Essentially, a cavernous hemangioma and a capillary hemangioma
are pathologically the same, it's just a difference in the size.
So let's take a look at what a cavernous hemangioma looks like on imaging.
Here we have multiple CT images and then an ultrasound images
demonstrating the imaging characteristics of a cavernous hemangioma.
Will go into detail of each one of these in just a minute,
but you can see here that we start off with a non-contrast examination.
So this is a multi-phase study. We then have an arterial phase
and the portal venous phase. After that we have the ultrasound,
so let’s go into a little more detail.
So on CT, a cavernous hemangioma is hypodense on the noncontrast images.
It demonstrates nodular peripheral enhancement
on the early postcontrast imaging, and then it gradually becomes isodense
overtime and then hyperdense on delayed imaging.
So let's take a look at the CT images here.
This is an example of our noncontrast image
and you can see the lesion is actually hypodense on this noncontrast image.
It almost looks like a little cyst, this is normal liver parenchyma here
but as we give contrast on the arterial phase,
this is a coronal arterial phase CT scan,
you can see that there is peripheral nodular enhancement.
You can see little nodules all around the periphery of this lesion.
And then on the delayed images you can also see that it's starting to fill-in,
you have a little more of this nodularity around the periphery
and you have a little more enhancement within the lesion as well.
On ultrasound the lesion is diffusely hyperechoic.
So let's take a look. Here we have an ultrasound image of the liver.
I'm outlining the entire liver here,
and the lesion is right here diffusely hyperechoic.
This is a very non-specific finding, when you see an echogenic liver
or hyperechoic lesion within the liver,
you can think of cavernous hemangioma but you really do need to perform
a CT or an MRI for better evaluation of this.
On MRI the lesion appears hypointense on T1.
It's hyperintense on T2. And the CT it demonstrates
nodular peripheral enhancement on early postcontrast imaging.
And then gradually becomes hyperintense on delayed imaging.
So the imaging characteristics are very similar to that seen on CT.
So let's talk about hepatic cyst. This is also another very common finding
that's found within the liver.
A hepatic cyst is a well circumscribed lesion and it has fluid characteristics.
So you can see here within the liver there are two hepatic cysts.
They are very well circumscribed, they’re hypodense
and after contrast administration they do not enhance.
So they appear very similar initially to hemangioma.
However, after contrast administration the hemangioma
will demonstrate nodular enhancement
while hepatic cyst shouldn’t demonstrate any enhancement
and that's how you differentiate the two.