Characterization of residual kidney function in chronic hemodialysis patients using plasma metabolomics.

In dialysis, preservation of residual kidney function (RKF) is associated with a favorable prognosis. We aimed to identify differences in plasma metabolites depending on the presence of RKF and to evaluate whether a subset of biomarkers could assist in classifying RKF. A prospective study was conducted among chronic hemodialysis (HD) patients in Geneva, Switzerland. Presence of significant RKF was defined as residual clearance of urea (KRU) ≥ 2 mL/min on 24 h urine collection. A total of 89 a priori selected plasma metabolites were analyzed by liquid chromatography-mass spectrometry. We included 136 patients, 54 with KRU ≥ 2 mL/min (40%) and 82 (60%) with KRU < 2 mL/min. The overall metabolic profile strongly differed between patients with and without significant RKF, despite similar total (residual + dialytic) clearances. Classification based on the metabolic profile achieved a 93% accuracy to predict significant RKF at a 2 mL/min cut-off. A subset of 3 biomarkers allowed RKF classification with 87% accuracy. RKF has a decisive influence on the overall metabolic profile of HD patients, which may partly explain its clinical benefit. This provides a physiological rationale for RKF preservation in incremental HD programs, while a limited subset of metabolites could prove useful in monitoring RKF in this setting.