This study aims to explore the effects of tacrolimus sustained-release capsules on the incidence of biopsy-proven acute rejection(BPAR) and fibrosis in pediatric liver transplant recipients.

Tacrolimus is a commonly used immunosuppressant after liver transplantation. However, with increased postoperative time and a decline in postoperative compliance, some children may miss medication, leading to acute rejection. Repeated rejection can cause fibrosis of the transplanted liver, seriously impacting graft function and even postoperative survival, sometimes resulting in the need for a second liver transplant. In adult liver transplant recipients, tacrolimus sustained-release capsules have been shown to significantly improve overall and transplanted liver survival compared to conventional formulations (immediate-release tacrolimus，taken twice daily). Therefore, this study aims to explore the effects of tacrolimus sustained-release capsules on the incidence of biopsy-proven acute rejection(BPAR) and fibrosis in pediatric liver transplant recipients.

Inclusion Criteria:

1. Children (≤18 years old) who have undergone liver transplantation, with no gender limitations;
2. Able to completely swallow capsules;
3. Have been using immediate-release tacrolimus for at least three months prior to study enrollment;
4. Have normal blood count, liver and kidney function, coagulation function, and considered clinically stable by researchers;
5. Undergo a programmed liver biopsy;

Exclusion Criteria:

1. Multi-organ combined transplantation or multiple liver transplantation;
2. Adjuvant liver transplantation or use of bioartificial liver therapy;
3. ABO incompatible children with liver transplantation;
4. Allergic to tacrolimus;
5. Participation in any other clinical study within 3 months prior to enrollment;
6. Use of tacrolimus sustained release capsules before enrollment;
7. Tacrolimus trough concentration lower than 3.5 ng/ml at the time of screening;