Protocol graft biopsy in kidney transplantation.

Accurate interpretation of renal allograft biopsy is necessary to guide therapy, especially when an episode biopsy is taken to rescue the graft. Contrarily, a protocol biopsy is carried out routinely to identify baseline conditions (biopsy at 0 or 1 h), subclinical rejection, histological change under current immunosuppression regimen, drug nephrotoxicity, viral infection, and recurrence of glomerulonephritis. Semiquantitative scoring for active lesions including tubulitis, glomerulitis, capillaritis, arteritis, arteriopathy, and others such as polyomavirus infection are key factors in transplant pathology. Recently, the Banff classification has proposed several novel concepts focused on antibody-mediated rejection (ABMR). This review presents the interpretation of transplant pathology from rejection to infection, recurrence of glomerulonephritis, and drug nephrotoxicity, with a description of ABMR according to the 2013 and 2017 Banff classification.