LCN2 and acute kidney injury: Variables are given as median and interquartile range; age is given as median (min -max). P-values were calculated using Wilcoxon rank-sum test (significance level α = 0.05); for categorical variables Chi-square and Fisher’s tests were used. AKI - acute kidney injury. No-AKI - no acute kidney injury. Euroscore - European System for Cardiac Operative Risk Evaluation. NGAL - neutrophil gelatinase-associated lipocalin. sCrea - serum creatinine. CKD - chronic kidney disease. *ΔsCrea was obtained as difference between serum creatinine concentration after and before surgery.