What is LI-RADS?
LI-RADS (Liver Imaging Reporting and Data System) is a comprehensive standardized system developed by the American College of Radiology to standardize the acquisition, interpretation, and reporting of CT, MRI, and contrast-enhanced ultrasound examinations in patients at risk for hepatocellular carcinoma (HCC). 1
Core Purpose and Design
LI-RADS provides a structured framework to categorize liver observations based on their probability of being HCC, non-HCC malignancy, or benign lesions. 1 The system was created through collaboration among radiologists, hepatologists, pathologists, and surgeons to address the full spectrum of lesions and pseudolesions encountered in at-risk populations. 1, 2
Categorization System
LI-RADS assigns observations into specific categories that reflect diagnostic certainty: 1, 3
- LR-1: Definitely benign
- LR-2: Probably benign
- LR-3: Intermediate probability of malignancy
- LR-4: Probably HCC
- LR-5: Definitely HCC
- LR-M: Probably or definitely malignant, but not HCC-specific (e.g., intrahepatic cholangiocarcinoma)
- LR-TIV: Tumor in vein
- LR-NC: Non-categorizable due to image degradation or technical issues
Major Imaging Features
The system uses specific major features to categorize observations: 1, 4
- Arterial phase hyperenhancement (APHE): Nonrim arterial enhancement greater than surrounding liver
- Washout appearance: Temporal reduction in enhancement relative to liver in portal venous or delayed phases
- Enhancing capsule: Smooth, uniform rim enhancement in portal venous or delayed phases
- Size: Measured in millimeters
- Threshold growth: Specific growth criteria over time
The diagnostic algorithm combines these features with lesion size to assign categories, with LR-5 requiring nonrim APHE plus either washout or enhancing capsule (depending on size). 1
Applicable Imaging Modalities
LI-RADS encompasses four distinct algorithms: 2
- Ultrasound for HCC surveillance
- CT and MRI for HCC diagnosis and tumor staging
- Contrast-enhanced ultrasound (CEUS) for HCC diagnosis
- CT/MRI for treatment response assessment
LI-RADS is the only major guideline system that permits definitive HCC diagnosis using CEUS as the initial imaging modality. 1 CEUS LI-RADS uses modified criteria, with LR-5 requiring APHE followed by late (>60 seconds) and mild washout. 1
Target Population
The system applies specifically to patients at high risk for HCC, including those with: 1, 2
- Cirrhosis (any etiology)
- Chronic hepatitis B infection
- Current or prior HCC
Clinical Integration and Validation
LI-RADS demonstrates high accuracy in stratifying HCC and malignancy probabilities, with systematic reviews confirming its diagnostic performance. 1 A 2023 meta-analysis showed clear stratification of HCC percentages across LI-RADS categories on both CT and MRI. 1
The 2025 EASL guidelines and 2018 AASLD guidelines both incorporate LI-RADS into their diagnostic algorithms, reflecting its acceptance as a standard approach. 1 The system has been integrated with the Organ Procurement Transplantation Network/United Network for Organ Sharing criteria. 2
Ancillary Features
Beyond major features, LI-RADS incorporates ancillary features that radiologists may use at their discretion to upgrade categories (up to but not beyond LR-4) or apply additional modifiers. 1, 5 These features help refine categorization when major features alone are insufficient.
Standardized Reporting
LI-RADS provides specific templates for reporting observations, either in continuous paragraph format or structured format with keywords. 6 This standardization facilitates multidisciplinary communication and clinical decision-making. [6, @17@, @18@]
Important Limitations
CEUS LI-RADS has specific constraints: it has fewer ancillary features than CT/MRI, permits characterization of only a limited number of targeted observations per examination (preferably those visible on precontrast ultrasound), and is not suitable for staging. 1
Arterial phase iso- or hypoenhancing observations cannot be categorized as LR-5 (definite HCC), though they may qualify as LR-4 (probable HCC) with appropriate combinations of other major features. 1
Evolution and Updates
The system has undergone iterative refinement since 2011 based on scientific evidence, expert opinion, and user feedback, with the most recent version being LI-RADS v2018. 1, 2 The goal is progressive worldwide adoption culminating in a single unified international system. 2