KL and acute kidney injury: Extracted data included the methodological framework of each study, demographic profiles, the spectrum of concurrent comorbidities, the incidence and temporality of AKI utilizing established criteria, the nature of the cardiac procedure, the duration of intraoperative events (specifically aortic cross-clamp and CPB durations), Klotho levels gauged at baseline and subsequent postoperative junctures (2, 4, 12, 24, 48, 72 h) whenever possible, the length of ICU and total hospital stay, mortality rates, and the duration of postoperative surveillance.