Abstract: Objective To analyze the etiological characteristics of unexplained liver dysfunction in children and provide a basis for the diagnosis and treatment of such disease. Methods From January 2020 to December 2023, 969 children with "liver dysfunction" were admitted to the 988th Hospital of the Joint Logistics Support Force, including 530 males and 439 females, with a ratio of 1.2:1 and no significant difference (P>0.05); Patiens were divided into infant and toddler group (≤ 3 years old), preschool group (4-6 years old), and school-age group (7-14 years old) by age, and conduct statistical analysis on clinical case data of all patients. Results The causes of abnormal liver function in children were generally divided into infectious causes, non infectious causes, and unknown causes. Infectious causes accounted for the highest proportion (53.9%), while EB virus (16.9%) and cytomegalovirus (13.7%) were the most common, and mycoplasma pneumoniae, adenovirus, COVID-19 also accounted for a certain proportion; Among non infectious causes, drug-induced liver injury (DILI) (8.5%), non-alcoholic fatty liver disease (NAFLD) (8.0%), and trauma (4.6%) were the most common; 203 cases (20.9%) of children with abnormal liver function could not be diagnosed clearly, accounting for a relatively high proportion. In the infant and toddler group, the proportion of cytomegalovirus (22.7%) was the highest, and the incidence rate was significantly higher than the other two groups (P<0.05); In the school-age group, NAFLD was the most common disease, accounting for 31.5%, with a significantly higher incidence rate than the other two groups (P<0.05). All patients had mild and moderate liver injury, accounting for 65.4% and 30.5% respectively. After active treatment, the overall effective rate was 98.1%. Conclusion Among the causes of liver dysfunction in children, infection remains the main factor, with EB virus and cytomegalovirus infections being the most common; Among non infectious factors, the prevalence of DILI and NAFLD is relatively high and showing an upward trend. Further strengthening of rational medication and lifestyle interventions in children is needed; Liver injury caused by trauma is not uncommon and may be related to hepatic stress injury (HSI); There are still many unexplained liver injuries that require further research; Abnormal liver function in children is often characterized by mild to moderate damage. After early diagnosis and active treatment, the overall prognosis is good.

Key words: Children, Abnormal liver function, Infection, EB virus, Cytomegalovirus, Drug induced liver injury, Non alcoholic fatty liver disease