LCN2 and acute kidney injury: Postoperative urinary NGAL, L-FABP, and KIM1 did not differentiate AKI and non-AKI patients (Fig 1), whereas postoperative urinary albumin/creatinine ratio (ACR) detected AKI with an AUC [95% CI] of 0.63 [0.51–0.74] at 2h and 0.65 [0.55–0.76] at 4h after CPB (Fig 3).