Understanding LI-RADS, Its Relationship to AASLD and OPTN, and the Challenges of Its Adoption

Imaging-based diagnosis of hepatocellular carcinoma (HCC) is incorporated in many clinical guidelines on the management of HCC. However, there is variability in the diagnostic criteria for HCC and lack of precise definitions for imaging characteristics. With the intent of standardization and maintaining compatibility with the American Association for the Study of Liver Diseases (AASLD) and Organ Procurement and Transplantation Network (OPTN), the Liver Imaging Reporting and Data System (LI-RADS) was developed as a system for standardizing the performance, interpretation, and reporting of CT and MRI in patients at high risk of HCC. It precisely defines the terms and imaging features used in the diagnostic algorithm with the aid of a lexicon and illustrative atlas. While it is a comprehensive system, the challenges to its adoption are not trivial and can be controversial. A better understanding of the purpose and the limitation of the system can help in building consensus within and across disciplines. In this paper, we describe LI-RADS and its relationship to AASLD and OPTN guidelines. The LR-5 category is essentially equivalent to OPTN class 5 with few minor exceptions. LR-5 has been expanded to also encompass the AASLD definition of HCC. LR-4, LR-3, and LR-2 allow for more granular classification of indeterminate lesions. We highlight the advantages of the system and try to address the challenges that may impede or delay its adoption. We also review the emerging literature on its validation emphasizing that since LR-5 is designed to be specific, many HCCs will not meet LR-5 criteria and most of them will be LR-4.