ABSTRACT: BACKGROUND:Recent 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. METHODS:EMBASE, 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. RESULTS:We 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. CONCLUSIONS:CI-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.