Biopsy of the transplanted kidney: current state of the issue (experience of the transplantation center)

Kidney transplant rejection is the main cause of graft dysfunction and kidney transplantation failure. Antibody-mediated rejection (AMR) and T-cell-mediated rejection (TCMR) are the most important causes of graft rejection. Other causes of graft loss include vascular thrombosis, urinary tract obstruction and nephrotoxicity of calcineurin inhibitors. Aim - to present the experience of performing transplanted kidney biopsies in patients of different ages in a single transplantation center to study the feasibility of performing protocol biopsies. Materials and methods. Since 2020, we have performed 332 kidney transplantations. Of these, 21 (6.3%) were kidney transplants in children. Over the past three years, 89 transplanted kidney biopsies have been histologically examined, of which 8 (9%) were pediatric. Among them, 10 (11.2%) were repeat (second). Results. The vast majority of results were isolated AMR (67.6% before 14 days and 57.9% after 14 days). Suspected TCMR was observed in 10.6% of biopsies. 34 (38.2%) biopsies were performed in the first 14 days after transplantation. Among them, isolated active AMR was diagnosed in 23 (67.6%) cases, combined rejection was detected in five (14.7%) cases, microvascular inflammation (C4d negative) in three (8.8%) cases, active AMR combined with suspected TCMR was detected in two (5.8%) cases, and there were no signs of rejection in one (2.9%) case. Another 19 (21.3%) biopsies were performed between 14 and 100 days, where in 11 (57.9%) cases isolated AMR was diagnosed, in three (15.8%) cases a combination of AMR and suspected TCMR was detected, in two (10.5%) cases combined rejection was observed, in another two (10.5%) cases microvascular inflammation (C4d negative) was observed and in 1 (5.3%) case signs of immunological rejection were absent. Conclusions. Signs of rejection of the transplanted kidney are more often observed in children, which requires an earlier approach to performing a biopsy (protocol biopsy option). In the first 100 days after transplantation, when performing a biopsy in patients with impaired graft function, in most cases, active AMR is detected. However, a fairly large proportion also accounts for cases of combined rejection, suspected TCMR and cases of absent immunological rejection, which confirms the appropriateness of using biopsy “on demand”. The study was performed in accordance with the principles of the Declaration of Helsinki. The study protocol was approved by the local ethics committee of the mentioned institutions. Informed consent of the patients was obtained for the study. The authors declare that there is no conflict of interest.