Urine biochemistry in septic and non-septic acute kidney injury: a prospective observational study.

Purpose: Determine whether there are unique patterns to the urine biochemistry profile in septic compared with non-septic acute kidney injury (AKI) and whether urinary biochemistry predicts worsening AKI, need for renal replacement therapy and mortality. Materials and Methods: Prospective cohort study of critically ill patients with septic and non-septic AKI, defined by the RIFLE (Risk, Injury, Failure, Loss, End-Stage) criteria. Urine biochemistry parameters were compared between septic and non-septic AKI and were correlated with neutrophil gelatinaseassociated lipocalin (NGAL), worsening AKI, renal replacement therapy (RRT), and mortality. Results: Eighty-three patients were enrolled, 43 (51.8%) with sepsis. RIFLE classwas not different between groups (P = .43). Urine sodium (UNa) b 20 mmol/L, fractional excretion of sodium (FeNa) b1%, and fractional excretion of urea (FeU) b 35% were observed in 25.3%, 57.8%, and 33.7%, respectively. Septic AKI had lower UNa compared with non-septic AKI (P = .04). There were no differences in FeNa or FeU between groups. Urine NGALwas higher for FeNa.1%compared to FeNab1%(177.4 ng/mL [31.9-956.5] vs 48.0 ng/mL [21.1-232.4], P = .04). FeNa showed low correlation with urine NGAL (P = .05) and plasma NGAL (P = .14). There was poor correlation between FeU and urine NGAL (P =.70) or plasmaNGAL (P = .41). UNa, FeNa, and FeU showed poor discrimination for worsening AKI, RRT and mortality. Conclusion: Urine biochemical profiles do not discriminate septic and non-septicAKI. UNa, FeNa, and FeU do not reliably predict biomarker release, worsening AKI, RRT ormortality. These data imply limited utility for these measures in clinical practice in critically ill patients with AKI. [ABSTRACT FROM AUTHOR]