NAFLD Histology: a Critical Review and Comparison of Scoring Systems

Abstract

Despite the emergence of non-invasive tests, liver biopsy remains the gold standard for the diagnosis of non-alcoholic fatty liver disease (NAFLD). This review will provide an overview of the histology of adult NAFLD with a focus on current scoring systems, histologic features that predict clinical outcomes, and areas in need of improvement. Studies during the last two decades have established the histologic features used to categorize NAFLD into non-alcoholic fatty liver (NAFL) and non-alcoholic steatohepatitis (NASH), described histologic scoring systems that measure disease activity and fibrosis, and correlated histologic features with fibrosis progression and liver-related outcomes. Hepatocellular ballooning degeneration with associated lobular inflammation is the key feature that distinguishes NAFL from NASH. Fibrosis remains the most important feature in predicting relevant clinical outcomes; however, fibrosis and ballooning degeneration are tightly linked. Despite these advances, deficiencies remain in the histologic evaluation of NAFLD. While histologic scoring systems have been developed and used in both clinical trials and clinical practice, areas of uncertainty exist, and refinement of current histologic indices is needed. Standardized assessment of these features is essential in clinical trials.