Contrast-associated acute kidney injury (CA-AKI) is a prevalent complication following coronary angiography (CAG). However, there is ongoing controversy surrounding its precise definition. Although previous studies have demonstrated the successful application of appropriate definitions in managing high-risk CA-AKI patients, there remains limited research on the association between different definitions and prognosis specifically in patients with chronic kidney disease (CKD).A total of 4197 CKD patients undergoing coronary angiography (CAG) were included in this study. Two definitions of contrast-associated acute kidney injury (CA-AKI) were used: CA-AKIA, which was defined as an increase of ≥0.5 mg/dL or >25% in serum creatinine (SCr) from baseline within 72 hours after CAG, and CA-AKIB, which was defined as an increase of ≥0.3 mg/dL or >50% in SCr from baseline within 48 hours after CAG. Cox regression analysis was employed to assess the association between these two definitions and long-term mortality. Additionally, population attributable risks (PARs) were calculated to evaluate the impact of CA-AKI definitions on long-term prognosis.During the median follow-up period of 4.70 (2.50-7.78) years, the overall long-term mortality was 23.6%, and the long-term mortality in patients with CA-AKI according to both CA-AKIA and CA-AKIB criteria were 33.5% and 33.8%, respectively. We found that CA-AKIA (HR: 1.45, 95% CI: 1.23-1.70, p<0.001) and CA-AKIB (HR: 1.44, 95% CI: 1.23-1.69, p<0.001) were associated with long-term mortality. The PARs were the highest for CA-AKIA (5.87%), followed by CA-AKIB (5.70%).Contrast-associated acute kidney injury (CA-AKI) is a frequently observed complication in CKD patients undergoing coronary angiography (CAG), and both definitions of CA-AKI are significantly correlated with a poor long-term prognosis. Consequently, in the clinical management of CKD patients, it is crucial to prioritize CA-AKI, irrespective of the specific CA-AKI definition used.© 2024 Feng et al.