Metabolic dysfunction-associated fatty liver disease (MAFLD) is a new concept proposed in 2020. Unlike non-alcoholic fatter liver disease (NAFLD), the diagnosis of MAFLD requires the presence any of the following 3 metabolic risks, including overweight/obesity, presence of diabetes mellitus, and evidence of metabolic dysregulation. However, there are patients that have hepatic steatosis but no metabolic risk, who thus do not meet the diagnostic criteria of MAFLD. Besides, there are patients with both MAFLD and other liver diseases. The clinical features and the management of these patients remain unclear. Thus, further histopathological and clinical study is required to elucidate and compare the characteristics of MAFLD and NAFLD.

Here, in this single-center, prospective clinical study, investigators are planning to establish a long-term follow-up cohort of patients with either MAFLD or NAFLD. In order to understand the risk of developing liver-related complications and important extra-hepatic outcomes (e.g. cardiovascular disease), and also to better elucidate the risk of disease progression in "lean" NAFLD individuals without any metabolic dysregulation and MAFLD individuals with dual or multiple causes.

Ultimately, investigators aim to improve the diagnosis of MAFLD and improve patients' outcomes.

The study is divided into 2 parts:

Firstly, it contains a cross-sectional study to collect the clinical data of the patients with fatty liver. The clinical features of this population will be analysed.

Secondly, the study will collect the plasma, urine and stool samples of the patients in this cohort. And then a long-term follow-up of these patients will be carried out. Investigators wish to find out biomarkers that can detail patient stratification and predict the prognosis of the disease.

Inclusion Criteria:

• Diagnosed as hepatic steatosis in adults (fulfill at least one of the followings):

  1. Liver ultrasound shows liver parenchymal hyperechoic or "bright liver"
  2. Controlled attenuation-parameter (CAP) ≥248dB/m
  3. Hepatic steatosis diagnosed by CT/MRI/MRS
  4. MRI-based proton-density fat fraction (MRI-PDFF) shows liver fat content>8%
  5. Fatty liver confirmed by liver histology.

Exclusion Criteria:

1. Diagnosed with hepatocellular carcinoma or other malignancy (in accordance with the appropriate diagnostic criteria);
2. During pregnancy;
3. Patients with history of liver transplantation;
4. Patients with serious cardiovascular and cerebrovascular events (such as acute myocardial infarction, cerebral infarction, cerebral hemorrhage, etc.).

This study include 3000 patients diagnosed as hepatic steatosis (both inpatients and outpatients of Nanfang hospital). We exclude the patients with history of liver transplantation, history of hepatocellular carcinoma (HCC) or other active malignancy, congestive heart failure and serious cerebrovascular disease, and pregnancy.