LCN2 and acute kidney injury: S-AKI: Sepsis Associated Acute Kidney Injury; NGAL: neutrophil gelatinase-associated lipocalin; IL-18: interleukin-18; Cr: urine creatinine; KIM-1: kidney injury molecule-1; L-FABP: liver-type fatty acid-binding protein; TIMP-2 × IGFBP-7: tissue inhibitor of metalloproteinases-2 × insulin-like growth factor-binding protein-7