Introduction: In the general population, lack of renal function recovery (RFR), 90 days after acute kidney injury (AKI) is a contributor to inferior renal outcomes and mortality. Ischemia and reperfusion during kidney transplantation (KT) contributes to AKI and  delayed graft function (DGF), a severe form of AKI. Our aim was to analyze the long-term prognostic implications of RFR at 90 days, in recipients with and without DGF.
Methods: This was a retrospective analysis of adult deceased donor KT recipients (1996 -2016). Outcome of interest was death censored graft failure (DCGF). RFR was calculated using the formula (observed eGFR/predicted eGFR) X 100. Predicted eGFR was half of the donor eGFR plus pre-emptive recipient eGFR, and observed eGFR was the average of 3 best values, 90 days post-KT. Grafts with primary non-function were excluded. The Chronic Kidney Disease Epidemiology Collaboration prediction equation was used to determine the eGFR.
Results: 941 KT recipients were eligible for analysis, of which 25% had DGF. RFR was divided into 3 tertiles <75% (360), 75-100% (218) and >100% (363). Higher DCGF was noted in recipients that developed DGF, and had RFR<75% (Figure 1). In recipients that developed DGF, RFR had no further prognostic implications on DCGF (Table 1). However, in those that did not develop DGF, RFR<75% was associated with an 82% and 89% higher DCGF in univariate  and multivariate analysis, respectively.
Conclusion: In recipients that do not develop DGF, 90-day RFR<75% was associated with DCGF. This indicates the prognostic relevance of RFR as a short-term outcome as most KT do not develop DGF. We propose that to truly capture the impact of AKI and ischemia and reperfusion injury during the transplantation surgery, one must quantify RFR over 90 days after KT.