Clinicopathological Correlation of Kidney Allograft Biopsies According to the Banff 2022 Classification.

Introduction Kidney allograft biopsy remains the gold standard for the diagnosis of allograft dysfunction, providing essential information for identifying immune- and non-immune-mediated injuries. The Banff 2022 Classification represents the current international standard for the histopathological evaluation of kidney transplant biopsies. This study aimed to describe the clinicopathological distribution of kidney allograft biopsies according to the Banff 2022 Classification and to assess graft function 12 months after the index biopsy. Methods A retrospective descriptive study was conducted involving 119 kidney transplant recipients who underwent kidney allograft biopsy at Hospital Hermanos Ameijeiras, Havana, Cuba, between January 2006 and December 2018. Archived biopsy specimens were re-evaluated by an experienced renal pathologist according to the Banff 2022 Classification. Demographic characteristics, histopathological diagnoses, time from transplantation to biopsy, and graft function 12 months after the index biopsy were analyzed using descriptive statistics. Graft function was assessed by estimated glomerular filtration rate (eGFR) and proteinuria. Results Male recipients and patients younger than 60 years predominated in the study population. Non-rejection causes of allograft injury represented the largest diagnostic group, accounting for 52 (43.7%) biopsies, followed by T cell-mediated rejection (TCMR) in 37 (31.1%) and antibody-mediated rejection (ABMR) in 14 (11.8%). Histopathological diagnoses exhibited distinct temporal patterns after transplantation. During the first three months, acute cyclosporine nephrotoxicity was the most frequent diagnosis, followed by acute tubular necrosis (ATN) and acute TCMR, whereas after the first post-transplant year, chronic active TCMR was the most frequent diagnosis, followed by chronic active antibody-mediated rejection and chronic cyclosporine nephrotoxicity. At 12 months after the index biopsy, immune-mediated lesions generally showed lower mean eGFR values and more frequent proteinuria, whereas normal biopsies and non-immunological lesions, particularly ATN and acute cyclosporine nephrotoxicity, showed comparatively better graft function. Conclusions Kidney allograft biopsies demonstrated a broad spectrum of histopathological diagnoses, with non-rejection causes of allograft injury representing the most frequent findings. Histopathological diagnoses showed distinct temporal patterns according to the time from transplantation to biopsy, with acute cyclosporine nephrotoxicity predominating during the first three months after transplantation. At 12 months after the index biopsy, immune-mediated lesions generally showed lower eGFR and more frequent proteinuria, whereas normal biopsies and non-immune-mediated lesions showed comparatively better graft function.