Abstract: Objective To investigate the etiology of liver injury through pathological analysis of 40 patients with unexplained liver injury in order to guide clinical treatment. Methods Collect 40 patients with unexplained liver injury admitted from January 2017 to December 2019, and retrospectively analyze histopathological examination and clinical characteristics of liver biopsy. Results Among 40 hospitalized patients with abnormal liver function, 15 cases (37.5%) of drug-induced liver injury (DILI), 7 cases (17.5%) of non-alcoholic fatty liver disease (NAFLD), and 18 cases of liver damage caused by other reasons (45%); Different causes of liver injury have their own specific pathological characteristics. DILI is mainly manifested as lobular hepatitis, non-alcoholic steatohepatitis is manifested as fatty liver cell necrosis with hepatocyte ballooning, autoimmune hepatitis (AIH) Mainly manifested as obvious interface inflammation and clusters of plasma cells at the interface. Primary biliary cholangitis (PBC) is mainly manifested as biliary granuloma. Conclusion There are many causes of liver injury, drug-induced liver injury and fatty liver disease are the most common; liver biopsy has important diagnostic value in liver injury of unknown cause.

Key words: Unexplained cause, Liver injury, Clinical pathology, Liver biopsy