FGF23 and acute kidney injury: Third, although predictable intraoperative variables (e.g., operation time, operation trauma, anesthesia type) and novel biomarkers, such as microRNAs [43], urine neutrophil gelatinase-associated lipocalin (NGAL) [44–47], cystatin C [44], fibroblast growth factor-23 [48], and interleukin-18 [46,49], have been proposed as alternative methods for detecting individuals at high risk for AKI, the analysis used in the present study was limited to measurements of variables available in <5% of study participants.