CST3 and acute kidney injury: In the cohort of children in this study, serum cystatin c levels were significantly increased both before [1.41 (1.19–1.86) mg/L vs. 1.14 (0.91–1.28) mg/L, (P = 0.014)] and after CPB in AKI children [1.18 (1.13–1.46) mg/L vs. 0.85 (0.77–1.04) mg/L, (P = 0.001)].