The most promising early indicators of AKI directly after surgery across all age groups were Chitotriosidase-1 (AUC 0.79; 95% CI:0.64–0.94), Kallikrein-1 (AUC 0.76; 95% CI:0.76–0.89), and Carbonic anhydrase 3 (AUC 0.73; 95% CI:0.6–0.87). The gene discussed is KLK4; the disease is acute kidney injury.