“Acute kidney dysfunction with no rejection” is associated with poor renal outcomes at 2 years post kidney transplantation

BACKGROUND: “Acute kidney dysfunction with no rejection” (ADNR) corresponds to acute kidney injury without histological evidence of acute rejection (AR) in kidney transplant recipients (KTR). The prognosis of ADNR is unknown. METHODS: From 2007 to 2015, we categorized KTR with for-cause kidney biopsy within the first 12 months post kidney transplantation (KTx) into ADNR (n = 93) and biopsy-proven AR (n = 22). Controls (C, n = 135) included KTR with no ADNR or AR within the first 24 months post-KTx. A piecewise linear regression with a single fixed-knot at 12 months served to establish intercepts and slopes of MDRD-eGFR variations from 12 to 24 months. The percentage of KTR with ≥30% reduction of eGFR from 12 to 24 months was calculated as a surrogate marker of future graft loss. RESULTS: The median time for for-cause biopsy was 22 [10–70] and 13 [7–43] days for ADNR and AR, respectively. At 12 months, eGFR was significantly higher in C (57.6 ± 14.9 mL/min/1.73m(2)) vs. ADNR (43.5 ± 15.4 mL/min/1.73m(2), p < 0.0001) and vs. AR (46.5 ± 15.2 mL/min/1.73m(2), p < 0.0065). The proportion of KTR with ≥30% reduction in eGFR from 12 to 24 months reached 16.3% in C vs. 29.9% in ADNR (p = 0.02) and vs. 15% in AR (not significant). CONCLUSIONS: ADNR is associated with poor outcomes within 2 years post-KTx.