Uromodulin in Renal Transplant Recipients: Elevated Urinary Levels and Bimodal Association with Graft Failure

Background: Urinary uromodulin (UMOD) predicts renal prognosis in native kidneys, but data are conflicting. We investigated its prognostic impact for graft failure (GF) in renal transplant recipients (RTR; n = 600). Methods: UMOD concentration was measured cross-sectionally in RTR at 6.0 years [2.6-11.4] post-transplant, in matched patients with native chronic kidney disease (CKD) and healthy subjects. In 59 cases, RTR allograft biopsies were reviewed. Results: During a follow-up of 5.3 years [4.5-5.7], GF had occurred in 7% of RTR. Median UMOD excretion (mg/24 h) was 20.4 in RTR, 11.6 in CKD and 5.7 in controls (p <0.001). There was a curvilinear association between UMOD excretion and baseline renal function (p <0.003) and death-censored GF, with 5.5, 11.5 and 4.0% of the cases in subsequent UMOD excretion tertiles, respectively (p = 0.002). On multivariate Cox regression analysis, hazard ratios for GF for the 1st and 3rd tertiles were 0.37 (p = 0.01) and 0.21 (p = 0.001), respectively. Interstitial fibrosis and tubular atrophy were more severe in the middle tertile (p = 0.007). Conclusions: Urinary UMOD is elevated in RTR and associated with graft function, morphology and doutcome in a bimodal fashion. Dissection of the disparate mechanisms of GF prediction by urinary UMOD might provide new clues for its alleged pathogenetic significance in progressive renal function loss. Copyright (C) 2011 S. Karger AG, Basel