Cystatin C has been reported to be superior to creatinine in the diagnosis of contrast-induced AKI14, AKI after cardiac transplantation15, and in patients in the high-risk group.16 In contrast, there are also studies that have found that AKI cystatin C is not more effective than creatinine.9 In the present study, we observed a decrease in the level of the cystatin C marker at hour 6 due to serum dilation caused by post-operative hydration. This evidence concerns the gene CST3 and acute kidney injury.