Liver - LI-RADS

Liver Imaging Reporting And Data System

Frederieke Elsinger, Christopher Lunt, Alison Harris and Silvia Chang

Vancouver General Hospital

The Liver Imaging Reporting and Data System (LI-RADS) is a classification system which is used in patients with liver cirrhosis and chronic hepatitis B virus infection (HBV) who  have an increased risk of hepatocellular carcinoma (HCC).

The LI-RADS categories reflect the probability of HCC and are based on the typical CT or MR-findings in HCC.

Introduction

LI-RADS - Major features

The LI-RADS categories reflect the probability of HCC and are based on the typical CT or MR-findings in HCC (see table).

  1. Arterial phase hyperenhancement (APHE)
    APHE is non-rim arterial hyperenhancement of an observation or part of an observation which is greater than the enhancement of the surrounding liver.
    Rim APHE is not a feature of HCC and would result in category LR-M.
  2. Non-peripheral washout
    Decrease in attenuation or intensity from earlier to later phase, resulting in hypoenhancement in the portal venous or delayed phase.
  3. Capsule
    Smooth, uniform border surrounding all or most of an observation.
  4. Size and Threshold growth
    Threshold growth is increase in size of 50% or more within 6 months time during follow-up imaging. 
Click to enlarge

LI-RADS categories

The term observation is used when it is not sure, whether something is a lesion or a pseudolesion.

The LI-RADS categories reflect the probability of an observation being a HCC and ranges from LR-1 (definitely benign) to LR-5 (definitely HCC).

Use LI-RADS as follows:

  1. First determine whether there is enhancement.
  2. Then look at the type of enhancement.
    Non-rim hyperenhancement scores higher than hypo- or isoenhancement.
  3. Then look at the size of the lesion.
  4. Finally look for additional typical features of HCC like enhancing capsule, non-peripheral washout and growth of the lesion.

Additional categories are:

  • LR-TIV when there is tumor in a vein.
  • LR-M when a lesion is probably malignant but not HCC.
  • LR-TR when we are dealing with a treated HCC.

The most interesting part of the table is when we have to decide if an observation has to be placed in category LR-3, which is intermediate probability or in LR-4, which is probable HCC or in category LR-5, which is definitely HCC.

As mentioned above, first determine if there is enhancement and if it is non-rim APHE.
Then look at the size of the observation and finally count the number of additional major features.

Mass versus Pseudolesion

LI-RADS uses the term ‘observations’ to describe focal abnormalities which are distinct from the background liver parenchyma.
It is preferred not to use the word ‘lesion’ or ‘nodule’ as some of these abnormalities do not represent true lesions but are the result of a perfusion alteration, a hypertrophic pseudomass or an artifact. .

When to use LI-RADS

LI-RADS is used in patients with cirrhosis and chronic HBV infection.

LI-RADS should not be used in patients with cirrhosis caused by vascular disorders (see table).
In these patients the formation of benign hyperplastic nodules may resemble HCC on imaging and cause false positive diagnoses.

Major features

Typical HCC with APHE and washout.

Arterial Phase non-rim Hyperenhancement (APHE)

Here an image in the late arterial phase.
There is non-rim hyperenhancement.
In a late phase there is washout.

Typical HCC with APHE, washout and enhancing capsule

Washout - Capsule

This is another patient with an enhancing lesion and washout.
Note also the enhancing rim on the delayed phase.

A capsule is one of the major features of HCC and can be complete or partial.
A capsule should always be included within the measurement of the lesion.

LEFT: Hyperenhancing observation detected in segment 5. RIGHT: follow up 3 months later shows growth.

Size - Threshold growth

Size also determines in which category a lesion is placed.
The bigger the lesion, the higher the chance that it is a HCC.

Therhold growth is also an important finding.
It is defined as more tha 50% growth in less than 6 months

The images show an observation in segment 5 of the liver demonstrating arterial hyperenhancement.
The lesion has grown from 8 mm to 21 mm in 3 months, which means that there is threshold growth.

LI-RADS categories

Non enhancing lesions in a cirrhotic liver, compatible with cysts, LR-1

LR-1 definitely benign

Observations in this categorie are definite benign. 

Examples of LR-1 lesions are cysts or lesions that show spontaneous disappearance. 

The images show lesions that show no enhancement in both late arterial, portal venous and delayed phase.

Typical haemangioma in a patient with livercirrhosis.

LR-2 probably benign

LR-2 observations are probably benign.
Of all LR-2 lesions about 16% are HCC and 18% are malignant. 

Is dit niet heel veel??


Examples are perfusions alterations (shunts), hemangiomas, hepatic fat deposition or fat-sparing, hypertrophic pseudo mass, confluent fibrosis or scar. 

Distinct nodules < 20 mm without malignant features (see section of ancillary malignant features) can be categorized as LR-2.

Examples are nodules which are T1 hyperintense, T2 hypointense, siderotic or hepatobiliary phase hyperintense.

Heb je daar voorbeelden van?? mn siderotic

Continue with the MR of this patient.

MRI-images of the same patient.

The enhancement of this lesion follows the enhancement of the blood pool, which is typical for a hemangioma.

LR-3 intermediate probability

LR-3 observations vary from benign lesions to dysplastic nodules to HCC. 
Many LR-3s are vascular pseudolesions. 
Of all LR-3 lesions approximately 37% are HCC and 39% are malignant. 

Lesions that are placed in category LI-RADS 3 are:

  • Nodules with features of focal nodular hyperplasia or hepatic adenoma. 
  • Nodules of < 20mm without major features but with one or more ancillary findings of malignancy such as intralesional fat, T2 hyperintensity, diffusion restriction and HB phase hypointensity. 
  • Nodules above 20 mm and without major or ancillary features.

Study the MR-images. What are the findings?

The findings are:

  • Post contrast subtraction imaging shows a small arterially enhancing lesion.
  • lesion < 2cm
  • No washout on the portal venous or delayed phase.
  • The lesion was categorized as LI-RADS-3

Moet deze volledig beschreven worden.... geen wash out - geen capsule - < 2cm wel hyperenhancement ergo LR3

of misschien zo??

LR-4

Of all LR-4 observations about 74% are HCC and 81% are malignant. The categorizing of an observation as LR-4 depends on the size of the lesion, the presence of APHE and the amount of additional major features (see LIRADS table). If an arterial enhancing lesion measures between 10-19 mm and has one additional major feature, the assigned category depends on which type of feature is present. If capsular enhancement is noticed the lesion should be described as LR-4. If there is wash out or threshold growth the category changes to LR-5.

LR-5

The observed liver lesion has classic imaging characteristics of a HCC.
Of all LR-5 lesions 95% are HCC and 98% are malignant.
In patients with concurrent extra-hepatic malignancy the positive predictive value of LR-5 for HCC drops, especially if the primary tumor is hypervascular.
When in doubt, categorizing a lesion as LR-M might be more appropriate in this group of patients.

Arterially enhancing lesion with washout in segment VI suspicious of HCC; LR-5.
Note that the arterial enhancement is faint due to early arterial phase scanning with unopacified portal vein.
Additional small lesions can therefore be easily missed.

Volledige beschrijving...met tabel??

LR-TIV

LR-TIV should be applied when there is unequivocal soft tissue within a vein, regardless if an associated mass is seen or not. In most cases  venous invasion by tumor is related to HCC.
In a small percentage however this is caused by other, non-HCC malignancies. 
Additional clues of possible venous invasion by tumor can be the presence of an occluded vein with ill-defined margins or diffusion restriction.
An occluded vein contiguous with a malignant parenchymal mass should also raise suspicion of tumor invasion and should be scrutinized for enhancing soft tissue.

Volledige beschrijving volgens LI-RADS

LR-M

When a patient already has a known extrahepatic malignancy LI-RADS can still be used, however the positive predictive value of LR-5 for HCC decreases, especially if the patient has a hypervascular malignancy. 

When in doubt, classify as LR-M

Voorbeeld??

Ancillary features

Features favoring benignity

Ancillary features may be used for detection improvement, increase in confidence or category adjustment.
These features are not obligatory and can be used at the radiologist’s discretion. 
In case of category adjustment, observations can only be upgraded or downgraded one category. 
However you are not allowed to upgrade from LR-4 to LR-5, because these ancillary features lack sufficient specificity for HCC to allow for an LR-5 upgrade.

The table shows an overview of the benign and HCC specific ancillary features.
The table of features that favor the diagnosis of not HCC specific malignancy is shown in the next paragraph.


Features favoring HCC


Non-enhancing capsule
feature of a capsule surrounding an observation not appearing as an enhancing rim


Mosaic structure
the presence of randomly distributed compartments or nodules within an observation, usually with different imaging features

Blood products in mass
intralesional or perilesional hemorrhage in the absence of biopsy or trauma

Fat in mass
excess fat with the whole or part of the mass, more than adjacent liver.

Nodule in nodule

The imaging findings of a nodule, present within a larger nodule with different imaging characteristics.

Mosaic architecture

CT of a cirrhotic liver with a focal abnormality with a mosaic architecture.

IP and OP image

Blood products in mass

Study the CT-image.
What are the findings?

The findings are:

  • High signal in a mass in segment II both on an in-phase image aswell as on the out-of-phase image (arrow).

This represents internal hemorrhage and in the absence of biopsy or trauma, is a feature that favors the diagnosis of HCC.

Fat in mass

Excess of fat in the whole or part of a mass is an ancillary findings that favors the diagnosis of HCC.

HCC classified as LI-RADS 5.

Study the CT-image.
What are the findings?

The findings are:

  • irregular contour of the liver in a patient with cirrhosis
  • large spleen
  • ascites
  • an observation with non-rim hyperenhancement and macroscopic fat in segment VII of the liver (-50 HU, yellow arrow).

This was classified as LI-RADS 5

Study the CT-image.
What are the findings?

The findings are:

  • non-rim APHE in segment VI of the liver
  • Washout on PV phase 
  • Enhancing capsule
  • Microscopic fat on IP/OOP sequences

 These are all typical findings of HCC and the lesion was classified as LR-5.

Diffusion restriction

MR of a cirrhotic liver with an arterially enhancing observation (< 2 cm) in the right lobe (red arrow).
As there is no washout observed this should be classified as a LR-3 lesion.
However due to ancillary finding of diffusion restriction this observation can be upgraded to a LR-4.

Moet diffusie restrictie ook in de tabel genoemd??

Favoring non-HCC Malignancy

Protocols

Left image: early aterial phase (no enhancement of portal vein and poor arterial enhancerment of liver). Right image: Late arterial phase with good enhancement of both hepatic artery (white arrow) and portal vein (green arrow).

CT protocol

Arterial phase imaging

Required images for CT are arterial, portal venous and delayed phase.
Precontrast images recommended after locoregional treatment.

Arterial phase imaging refers to the hepatic arterial phase in which the hepatic artery and branches are fully enhanced and the hepatic veins are not yet enhancing. 

HCC usually enhances more strongly in the late arterial phase showing early enhancement of the portal vein and is therefore preferred over the early arterial phase (no enhancement of PV and poor enhancement of HCC).

Portal venous phase

Portal venous phase

There is complete enhancement of the portal veins with antegrade filling of hepatic veins. 
Liver parenchyma is usually at its peak of enhancement

Delayed phase

Delayed phase

Portal and hepatic veins are enhanced but less than in the portal venous phase. 
Liver parenchyma is enhanced but also less than in PV phase.
This phase is typically acquired 2-5 min after injection.

Hepatobiliary phase study: diffuse uptake of contrast by normal liver parenchyma with hypointense appearance of the vessels and contrast excreted within the bile ducts.

MRI protocol

The required sequences for MRI are: 

  • Unenhanced T1 IP and OP imaging
  • T2 (with or without fat suppression) 
  • Multiphase T1 pre and post contrast. 
  • Optional sequences: diffusion-weighted and subtraction imaging.

Transitional phase: acquired with a hepatobiliary contrast agent after the extracellular phase but before hepatobiliary phase. Liver vessels and hepatic parenchyma are of similar intensity. Typically acquired 2-5 min after injection.

Hepatobiliary phase: acquired with a hepatobiliary agent. Liver parenchyma is hyperintense to the hepatic vessels. There is excretion of contrast in the biliary system. Typically acquired about 20 min after injection of gadoxetate (or 1-3 hours after gadobenate)

Liver - LI-RADS