New concept in fatty liver diseases

In 2023, the nonalcoholic fatty liver disease (NAFLD) Nomenclature Consensus group proposed a new name and concept for NAFLD/nonalcoholic steatohepatitis. The Japanese Society of Gastroenterology and the Japanese Society of Hepatology have accepted these new names and concepts. It was reported that the terms "nonalcoholic" and "fatty" are misleading and inappropriate, because NAFLD does not reflect the etiology. Thus, appropriate disease names are discussed, and new concepts are published. First, the concept of steatotic liver disease (SLD) was proposed to encompass fatty liver diseases of various etiologies, which are classified into five categories. The diagnostic criteria for metabolic dysfunction-associated steatotic liver disease (MASLD) included fatty liver with at least one of the five cardiometabolic risk factors (body mass index or waist diameter, blood glucose or glycated hemoglobin, blood pressure, triglycerides, and high-density lipoprotein cholesterol) and the same restriction of alcohol consumption as NAFLD. A new fatty liver category was described, MetALD, to represent the intermediate drinker group (patients with MASLD with high weekly alcohol intake [140-350 g/week in women and 210-420 g/week in men]). The other five categories are alcohol-associated liver disease, fatty liver with an identifiable specific cause, and other fatty livers of unknown cause. Nonalcoholic steatohepatitis is an important pathological concept (metabolic dysfunction-associated steatohepatitis); however, its definition, including hepatocellular balloon-like degeneration, needs to be reassessed. In Japan, we should use these names and criteria to manage SLD, including hepatocellular carcinoma, which is markedly increasing.