Early changes in renal resistive index and mortality in diabetic and nondiabetic kidney transplant recipients: a cohort study

Background Renal resistive index (RI) predicts mortality in renal transplant recipients (RTR). However, its predictive value may be different according to the time of measurement. We analysed RI changes between 1 month and 3 months after transplantation and its predictive value for death with a functioning graft (DWFG). Methods We conducted a retrospective study in 1685 RTR between 1985 and 2017. The long-term predictive value of changes in RI value from 1 month to 3 months was assessed in diabetic and non-diabetic RTR. Results Best survival was observed in RTR with RI < 0.70 both at 1 and 3 months, and the worst survival was found in RTR with RI >= 0.70 both at 1 and 3 months (HR = 3.77, [2.71-5.24], p < 0.001). The risk of DWFG was intermediate when RI was < 0.70 at 1 month and >= 0.70 at 3 months (HR = 2.15 [1.29-3.60], p = 0.003) and when RI was >= 0.70 at 1 month and < 0.70 at 3 months (HR = 1.90 [1.20-3.03], p = 0.006). In diabetic RTR, RI was significantly associated with an increased risk of death only in those with RI < 0.70 at 1 month and >= 0.70 at 3 months (HR = 4.69 [1.07-20.52], p = 0.040). RI considered as a continuous variable at 1 and 3 months was significantly associated with the risk of DWFG in nondiabetic but not in diabetic RTR. Conclusion RI changes overtime and this impacts differently diabetic and nondiabetic RTR. RI short-term changes have a strong prognosis value and refines the risk of DWFG associated with RI.