GFR is the best measure of overall kidney function (22). The Cockroft-Gault formula is a commonly used way to predict GFR (23). GFR <30 mL/min/1.73 m2 is accepted as "severe RD" (22). SCr is a simple and practical universal biologic marker used for estimating glomerular filtration. Although SCr does not have a linear association with GFR, it has also been reported to be a powerful predictor of operative mortality (6). Thus, SCr and GFR were both accepted as preoperative indicators of RD with the cut-off levels of 180 µmol/L (or 2.0 mg/dL) and 30 mL/min/1.73 m2, respectively.