What is fatty liver? Fatty liver is a lesion caused by excessive accumulation of fat in the liver cells due to various reasons. Fatty liver disease is posing a serious threat to the health of the nation, becoming the second most common liver disease after viral hepatitis, and has been recognized as a common cause of insidious cirrhosis. Fatty liver is a common clinical phenomenon rather than an independent disease. Its clinical manifestations are asymptomatic in mild cases and aggressive in severe cases. In general, fatty liver is a reversible disease, and early diagnosis and timely treatment can often restore normalcy. The total amount of fat in the liver of a normal person is about 5% of the liver weight and contains phospholipids, triglycerides, lipids, cholesterol and cholesterol lipids. The amount of fat over 5% is mild fatty liver, over 10% is moderate fatty liver and over 25% is severe fatty liver. When the total fat in the liver exceeds 30%, it can only be detected by ultrasound and diagnosed as “fatty liver” by ultrasound. In patients with fatty liver, the total lipid amount can reach 40%-50%, some reaching 60% or more, mainly triglycerides and fatty acids, while phospholipids, cholesterol and cholesterol lipids only increase in small amounts. How can fatty liver be detected early? Fatty liver is a common diffuse liver disease that can be reversed if treated promptly; conversely, some patients can develop steatohepatitis or even cirrhosis. Therefore, early diagnosis and treatment is important to stop the progression of fatty liver and improve the prognosis. In recent years, with the development of imaging technology, especially the wide application of CT, MRI and ultrasound imaging in clinical practice, a more accurate clinical diagnosis can no longer be made by liver puncture biopsy. Due to the lack of specific clinical manifestations and laboratory indices for fatty liver, and the invasiveness of liver puncture biopsy, ultrasound and CT are now mainly used to diagnose fatty liver. It has been confirmed that imaging can not only screen for fatty liver but also confirm the diagnosis. Given that ultrasound has the advantages of being economical, rapid and non-invasive in diagnosing fatty liver, regular ultrasound examination of the liver for people at high risk of fatty liver is the best method for early detection of fatty liver. People at high risk for fatty liver are those who have risk factors for the development of fatty liver and are more likely to develop fatty liver than the general population. The main risk groups for fatty liver include obesity, especially visceral fatty obesity; diabetes mellitus, especially adult non-insulin-dependent diabetes mellitus; chronic heavy alcohol drinkers; hyperlipidemia, especially those with elevated blood triglycerides; long-term users of liver-damaging drugs; and individuals with a family history of obesity, diabetes mellitus and fatty liver. In conclusion, people with risk factors for the development of fatty liver should be aware of self-care and should undergo regular (1 to 2 times a year) liver ultrasound and other imaging examinations for early detection of fatty liver.