CST3 and acute kidney injury: This study has several key limitations: its retrospective single-center design introduces selection bias and constrains generalizability across diverse healthcare settings; the absence of tubular injury markers (e.g., cystatin C, NGAL) restricts mechanistic exploration of FAR-AKI relationships; and reliance on single static FAR measurements fails to capture dynamic perioperative trajectories, potentially underestimating delayed AKI prediction.