*Purpose: DGF after kidney transplantation (KTx) has been associated with an increased risk of rejection. For this reason, clinical guideline recommends weekly allograft biospy (Bx) in all patients with DGF. However, risks and benefits of such an aggressive policy remain unclear.

*Methods: In this retrospective, cohort study, we reviewed data from 223 consecutive allograft Bx performed in 145 deceased donor KTx. Only recipients treated with basiliximab or rabbit anti-thymocyte globulin (rATG) and standard-dose calcineurin inhibitor-mycofenolate mofetil-steroid were included. Our goal was to assess utility and safety of Bx obtained within 28 days of surgery. As utility measure, we considered the ability of the information gained with histology to affect clinical management. Relationships between transplant characteristics, indication, timing, and Bx-related outcomes were evaluated.

*Results: Indications for Bx were DGF (88%), lack of improvement in graft function (9%), and worsening graft function (3%). Histology showed acute tubular necrosis in 90% of the specimens whereas cell-mediated rejection, borderline rejection, and antibody-mediated rejection were detected in only 5%, 3%, and 0%, respectively. Overall, management was affected by the information gained with histology in 12% of the cases whereas complication rate was 4%. Recipients biopsied due to worsening graft function or lack of improvement in graft function were more likely to be diagnosed rejection (67% vs 33% vs 3%; P<0.01) and to have their treatment modified (100% vs 33% vs 7%; P<0.001) than those with DGF. We also observed that rejection (31% vs 4%; P<0.001) and treatment modification (38% vs 7%; P<0.001) were more frequently recorded in Bx performed between day 15 and 28 than from day 0 to 14. Utility of Bx was similar in all transplant categories (DBD vs DCD, standard vs expanded criteria, and low vs high immunological risk). However, the proportion of Bx leading to treatment modification was higher in the group receiving basiliximab than rATG (22% vs 7%; P<0.05). In particular, no rejections nor treatment modifications were recorded among low immunological risk recipients treated with rATG.

*Conclusions: Our experience demonstrates that current rejection rate during DGF is lower than previously reported. It also shows that in low immunological risk KTx treated with rATG and standard-dose calcineurin inhibitor, DGF protocol Bx performed in the first 2 post-transplant weeks are more risky than beneficial. In this group of patients, a tailored approach would allow to optimize results. Prospective interventional studies are warranted.

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