CST3 and Renal insufficiency: For example, the application of this model to renal insufficiency patients undergoing cardiac surgery would show the following results: postoperative creatinine 271 μmol/L, aortic cross‐clamping time 106 min, non-emergency surgery, preoperative cystatin C 800 μg/L, the total score of 100, and the risk of RRT was about 68%.