*Purpose: Progressive liver fibrosis threatens graft and patient longevity for children after liver transplantation (LT). Previous studies are limited to single-center, cross-sectional analyses. To address this knowledge gap, we examined prevalence of progressive allograft fibrosis in sequential surveillance biopsies from 78 pediatric LT recipients from 11 centers.

*Methods: Biopsies from 78 children (43 prospectively, 35 retrospectively, 0 LT for viral or autoimmune hepatitis) assessed by 1 central pathologist; paired biopsies compared side-by-side. Serum ALT and GGT levels were <40 U/L, index biopsy ≥4 yrs after LT, 2nd biopsy ≥4 yrs later. Fibrosis was staged by the liver allograft fibrosis score (LAFSc 0-9; 0 none, mild 1-2, moderate 3-5; severe 6-9) on H&E, trichrome stains. Significant fibrosis progression or regression was defined as LAFSc increase or decrease by ≥3.

*Results: Of 78 children, 51 were male, 44 had biliary atresia, 50 had living donors. Index biopsy was done at a median (IQR) 8.2 (5.9-11.6) yrs after LT with 89% on immunosuppression monotherapy, ALT 24 (19-35), GGT 15 (12-22) U/L. Fibrosis was none/mild in 29%, moderate in 56%, and severe in 14%. 2^nd biopsy was done a median (IQR) of 4.7 (4.3-5.1) yrs later, at 13.8 (10.9-16.8) after LT, with 91% on monotherapy, ALT 25 (19-37), and GGT 17 (14-28) U/L. The majority (56%) had minimal LAFSc change (-1, 0, +1; FIGURE): 10 (13%) progressed (7 mild to mod) and 4 (5%) regressed (mod to mild). After adjusting for baseline LAFSc, progression was associated with younger age at LT [median (IQR) 0.7 (0.6-1.0) vs. 1.3 (0.6-2.0) yrs; p=0.02] but not with donor/graft type, time from LT to 1st or 2nd biopsy, time between biopsies, or ALT/GGT/inflammation at 1st biopsy. None had biliary or vascular complications. 8 of 10 with progression were on less IS at 2nd biopsy, as were 33% of those with stable/improved fibrosis.

*Conclusions: In our multicenter cohort, at 8 and 14 years after LT, only 14% and 19% respectively, of surveillance biopsies showed severe fibrosis. Progression was uncommon, seen in only 13%. This differs distinctly from previously reported cohorts, which may reflect a more modern, tacrolimus-based regimen and the subset of children studied. Our low prevalence of severe or progressive fibrosis suggests that non-invasive fibrosis assessment could be a useful adjunct in long-term monitoring for children with normal transaminases.

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