BackgroundRecent studies have shown associations between contrast-induced acute kidney injury (CI-AKI) and increased risk of adverse clinical outcomes in acute coronary syndrome (ACS) patients undergoing percutaneous coronary intervention (PCI); however, the estimates are inconsistent and vary widely. Therefore, this meta-analysis aimed to evaluate the precise associations between CI-AKI and adverse clinical consequences in patients undergoing PCI for ACS.MethodsEMBASE, PubMed, Web of Science and Cochrane Library databases were systematically searched from inception to December 16, 2016 for cohort studies assessing the association between CI-AKI and any adverse clinical outcomes in ACS patients treated with PCI. The results were demonstrated as pooled risk ratios (RRs) with 95% confidence intervals (CI). Heterogeneity was explored by subgroup analyses.ResultsWe identified 1857 articles in electronic search, of which 22 (n=32,781) were included. Our meta-analysis revealed that in ACS patients undergoing PCI, CI-AKI significantly increased the risk of adverse clinical outcomes including all-cause mortality (18 studies; n=28,367; RR=3.16, 95% CI 2.52-3.97; I-2=56.9%), short-term all-cause mortality (9 studies; n=13,895; RR=5.55, 95% CI 3.53-8.73; I-2=60.1%), major adverse cardiac events (7 studies; n=19,841; RR=1.49, 95% CI: 1.34-1.65; I-2=0), major adverse cardiovascular and cerebrovascular events (3 studies; n=2768; RR=1.86, 95% CI: 1.42-2.43; I-2=0) and stent restenosis (3 studies; n=130,678; RR=1.50, 95% CI: 1.24-1.81; I-2=0), respectively. Subgroup analyses revealed that the studies with prospective cohort design, larger sample size and lower prevalence of CI-AKI might have higher short-term all-cause mortality risk.ConclusionsCI-AKI may be a prognostic marker of adverse outcomes in ACS patients undergoing PCI. More attention should be paid to the diagnosis and management of CI-AKI.