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; I2 = 56.9%), short-term all-cause mortality (9 studies; n = 13,895; RR = 5.55, 95% CI 3.53–8.73; I2 = 60.1%), major adverse cardiac events (7 studies; n = 19,841; RR = 1.49, 95% CI: 1.34–1.65; I2 = 0), major adverse cardiovascular and cerebrovascular events (3 studies; n = 2768; RR = 1.86, 95% CI: 1.42–2.43; I2 = 0) and stent restenosis (3 studies; n = 130,678; RR = 1.50, 95% CI: 1.24–1.81; I2 = 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.