Preoperative syndecan-1 concentration showed a non-significant association with the incidence of severe AKI (OR, 1.003; 95% confidence interval (CI), 1.000–1.006; p = 0.065), and post-CPB syndecan-1 concentration was significantly associated with the incidence of severe AKI (OR, 1.002; 95% CI, 1.000–1.005; p = 0.024). Here, SDC1 is linked to acute kidney injury.