Background: The Banff criteria have been developed to assess acute and chronic injury in renal allografts. However, the criteria have been based on biopsies for cause and may not reflect the true spectrum of pathologic injury that occurs. The goal of this study was to determine if new criteria are needed to assess injury in 10 year protocol biopsies.

Methods: Protocol renal allograft biopsies were obtained 10 years post-transplant in 100 patients transplanted between 1/1/2002 and 8/1/2004. During this period 449 adult conventional transplants were performed; prior to 10 years, 101 grafts were lost to patient death and 78 to other causes; 85 lost to follow-up. Immunosuppression consisted of tacrolimus, MMF, and prednisone in 76%. Scoring was performed using the Banff 2013 system and additional scoring not addressed by Banff.

Results: Histologic findings present at 10 years but not accounted for in the Banff schema included: diffuse mesangiosclerosis (MS), glomerulomegaly (GM), focal segmental glomerulosclerosis (FSGS), increased global glomerulosclerosis (GG), and specific patterns of arteriolar hyalinosis (AH). 85% of biopsies showed one or more chronic glomerular change, including MS in 63% of biopsies, GM in 31%, and FSGS in 19%. Compared to expected values for kidney age, there was increased GG in 52%. 53% of patients with MS did not have diabetes. Patients with FSGS had significantly increased proteinuria and decreased GFR versus those without FSGS. AH was present in 89% and was moderate or severe in 66%; 6% showed vacuolated arteriolar myocytes. When present, AH was intimal in 92% and both intimal and peripheral in 8%. Arteriosclerosis was present in 81%, moderate or severe in 40%. Only 16% of biopsies showed moderate or severe interstitial fibrosis and tubular atrophy, and only 13% showed transplant glomerulopathy (TG).

Conclusion: Most protocol biopsies at 10 years post-transplant show chronic histopathologic changes, particularly in glomeruli, that are not accounted for in the current Banff grading schema. These changes provide insight into late graft injury and call for a revised Banff system for late allograft biopsies.

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