*Purpose: Graft fibrosis is a concerning long-term complication after pediatric liver transplant (LT) and though perivenular (PV) fibrosis is common, its likelihood of progression and clinical significance are unclear; we seek to investigate PV fibrosis prevalence and both clinical and histologic associations.

*Methods: We conducted a single-center, retrospective, cohort study of children (0-18 years at LT) who had undergone surveillance liver biopsies (2006-2020). Biopsies were reviewed and scored for 15 features according to a standardized protocol by 2 pathologists. PV fibrosis was scored as 0, none; 1, mild; or 2, moderate/severe.

*Results: We reviewed 96 children (56% male; 49% biliary atresia; 55% partial grafts; 31% living donors) who underwent 118 surveillance biopsies; 22 had 2 biopsies. First biopsy was done at median (IQR) 8.7 (5.1-13.4) years after LT with ALT 27 (20-41) U/L and GGT 15 (12-32) U/L; 43%, 44%, and 13% showed no, mild, and moderate/severe PV fibrosis. Neither PV fibrosis presence nor severity was associated with donor or graft type, bile duct damage, portal inflammation or portal fibrosis (FIG).

The 22 paired biopsies were separated by median 4.6 (3.0-5.5) yrs. PV fibrosis regressed for 8 and progressed for 5. Among regressors 3, 3, and 2 had increased, stable, and reduced immunosuppression, respectively. Among progressors, 1, 2, and 2 had increased, stable, and reduced immunosuppression, respectively. No progressors had portal fibrosis or interface activity on either biopsy, nor vascular or biliary complications between biopsies.

*Conclusions: PV fibrosis is present in the majority of pediatric LT surveillance (normal liver tests) biopsies but is most commonly mild and remains stable over time. PV fibrosis is not associated with histologic features of rejection. Longitudinal study of sequential biopsies is needed to understand the causes and impact of PV fibrosis, and to inform its impact on long-term immunosuppression management.

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