Introduction: Kidney biopsy is the gold standard for diagnosing rejection, transplant glomerulopathy, and other pathology after transplantation. We aimed to understand the distribution of Banff classification of biopsy proven acute rejection in our population over a four year period.

Methods: We reviewed all transplant kidney biopsies performed at Cincinnati Children's Hospital Medical Center from 2013 – 2016. Biopsies are performed “for cause” at our institution. We recorded rejection episodes as well as classification according to Banff 2013 criteria and performed analysis of frequency of acute rejection and individual Banff classifications.

Results: A total of 215 biopsies were performed over the four years in 74 patients. 106/215 (49%) biopsies showed Banff 1a or higher acute cellular rejection ACR) and/or acute antibody mediated rejection (AMR) in 47/74 (64%) of patients. Of biopsies that showed acute cellular rejection (ACR), Banff classification was borderline in 21 (10%), 1A in 45 (21%), 1B in 33 (15%), 2A in 4 (2%), and 2B in none. Nine (4%) biopsies showed AMR without ACR and 16 (7%) showed mixed ACR and AMR. In these biopsies ACR grades were borderline (n=1), 1A (n=7), 1B (n=6), and 2a (n=2). Ten (4.6%) biopsies showed resolving rejection, no grade given. Average age at first rejection was 14.5 years (+/- 6.2 years). Median time to first rejection from time of transplant was 747 days with an IQR 286-2159 days, range 28-6681 days. Over the four year period we cared for 135 transplant patients, of which 47 (35%) ever experienced rejection (> Banff 1A), and 14 of those patients only experienced 1 episode of rejection, thus 33 (24%) patients of the population accounted for all repeat rejection episodes.

Conclusions: Acute rejection was diagnosed in nearly half of “for cause” kidney biopsies, and was almost always mild (Banff 1A or 1B). AMR and mixed rejection were relatively rare. The vast majority of biopsies and rejections were in a relatively few individuals. In the future non-invasive monitoring may reduce the need for biopsy to diagnose rejection. Risk prediction models and new treatment modalities must be developed to identify those at highest risk for rejection and decrease their rejection risk.

CITATION INFORMATION: Varnell, Jr. C., Carle A., Hooper D. Distribution of Biopsy Proven Acute Rejection in a Large Pediatric Kidney Transplant Program: A Four Year Experience Am J Transplant. 2017;17 (suppl 3).

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