Background: The shortage of donor kidneys has prompted interest in using organs from donors with severe acute kidney injury (AKI), but robust data on outcomes from donors with AKIN stage 3 remain limited. Methods: This single-centre, retrospective cohort study compared outcomes of kidney transplants from deceased donors with AKIN stage 3 AKI to matched non-AKI donors (n = 57 per group; matched by donor age ±5 years, year of transplant, and major cardiovascular risk factors). Primary outcomes were delayed graft function (DGF), death-censored graft survival, and patient survival. Secondary outcomes included renal function at follow-up. Results: DGF occurred in 54.4% (31/57) of AKIN 3 recipients vs. 33.3% (19/57) of non-AKI recipients (risk difference 21.1%, 95% CI 3.1–39.2; p = 0.037). Five-year death-censored graft survival was 94.7% vs. 96.4% (HR 1.28, 95% CI 0.25–6.52; p = 0.645). Five-year patient survival was 84.8% vs. 84.0% (HR 0.96, 95% CI 0.30–3.05; p = 0.979). Median follow-up was 32 months. Conclusions: In this preliminary, selected kidneys from AKIN stage 3 donors yielded similar medium-term graft and patient survival to non-AKI donors, despite higher DGF incidence. Findings should be interpreted cautiously and confirmed in adequately powered, multicentre studies with extended follow-up.

(1) Background: donor-derived circulating free DNA (dd-cfDNA) is an innovative biomarker with great potential for the early identification and prevention of graft damage; (2) Methods: Prospective study to analyze dd-cfDNA plasma levels in 30 kidney transplant patients during their post-transplant follow-up (15 days, 3, 6 and 9 months), to determine if the result could be of interest in the identification of possible adverse events, specially allograft rejection. In addition, the aim is also to verify the obtained data on sensitivity, specificity, NPV and PPV; (3) Results: Plasma levels of dd-cfDNA could be considered a novel biomarker of graft rejection after first term post-transplant up to several months before its clinical presentation, mainly in TCMR or ABMR. In this study, it appears to have no positive predictive value for borderline rejection or TCMR IA. Our results show a low NPV of the technique because other pathologies or biological post-transplant complications can also affect dd-cfDNA levels and they must be considered in the interpretation of the result.; (4) Conclusions: dd cfDNA could allow, together with other additional biomarkers in the context of a future score, avoid invasive biopsies in most cases, mainly in the case of suspected TCMR or ABMR.