LCN2 and acute kidney injury: Pre-operatively, there were 10/20 (50%) biomarkers which were significantly elevated in patients with PTOS-AKI (Table 2): sTNFR1 (serum and urine), sTNFR2 (serum), H-FABP (serum), NGAL (plasma), IL-12p40 (serum), MIP-1α (plasma), TNFα (plasma), MCP-1 (plasma), and midkine (serum).