Resistive index as a predictor of early failure of kidney transplantation

Current Insights into the Significance of the Renal Resistive Index in Kidney and Cardiovascular Disease

Initially, the renal resistive index (RRI) was investigated with the aim of improving diagnosis in kidney diseases, but this goal was not met. Recently, many papers have highlighted the prognostic significance of the RRI in chronic kidney disease: specifically, in estimating the revascularization success of renal artery stenoses or the evolution of the graft and the recipients in renal transplantation. Moreover, the RRI has become significant in the prediction of acute kidney injury in critically ill patients. Studies in renal pathology have revealed correlations of this index with parameters of systemic circulation. The theoretical and experimental premises of this connection were then reconsidered, and studies analyzing the link between RRI and arterial stiffness, central and peripheral pressure, and left ventricular flow were conducted with this purpose. Many data currently indicate that RRI is influenced more by pulse pressure and vascular compliance than by renal vascular resistance-assuming that RRI reflects the complex interplay between systemic circulation and renal microcirculation and should be considered a marker of systemic cardiovascular risk beyond its prognostic relevance for kidney disease. In this review, we overview the clinical research that reveals the implications of RRI in renal and cardiovascular disease.

Application of Ex Vivo Normothermic Machine Perfusion in Deceased Donors With Acute Kidney Injury With Successful Renal Transplantation: A Preliminary Experience

Ex vivo normothermic machine perfusion (NMP) has improved organ preservation and viability assessment among heart, liver, and lung transplantation. However, literature regarding the application of NMP in human clinical kidney transplantation remains limited. Numerous kidneys, especially from donors with stage 3 acute kidney injury (AKI), are not utilized concerning the high rate of delayed graft function (DGF) and primary nonfunction. The present study investigated the impact of NMP (135-150 min) on short-term outcomes after kidney transplantation from deceased donors with AKI.

Methods

Graft outcomes of NMP kidneys were compared with contralateral kidneys stored in static cold storage (SCS) from the same donor with AKI during December 2019-June 2021. The study's primary aim is to assess the safety and feasibility of NMP in deceased donors with AKI. The primary outcome was DGF. Secondary outcomes were duration of DGF, biopsy-proven rejection, postoperative intrarenal resistive index, postoperative infections, hospital stay duration, primary nonfunction, and kidney function estimated glomerular filtrate rate at discharge, 3 mo, and 1 y.

Results

Five pairs of AKI kidneys (NMP versus SCS) were included in the final analysis. The results show no statistically significant differences in clinical outcomes between NMP versus SCS kidneys; however, NMP kidneys demonstrated slightly improved estimated glomerular filtrate rate at 3 mo (59.8 ± 5.93 [59] versus 75.20 ± 14.94 [74]) mL/min/1.73 m² (P < 0.065) and at the last follow-up (12-29 mo) (72.80 ± 10.71 [75]) versus (94 ± 22.67 [82]) mL/min/1.73 m² (P < 0.059) as compared with SCS kidneys. A higher proportion of NMP kidneys had normal intrarenal resistive index (0.5-0.7) and mild acute tubular injury on protocol biopsy, suggesting NMP is safe and feasible in deceased donors with acute kidney injury.

Conclusions

NMPs of AKI donor kidneys are safe and feasible. A larger cohort is required to explore the reconditioning effect of NMP on AKI kidneys.