['To assess the impact of preoperative renal dysfunction on in-hospital mortality and late survival outcome following adult cardiac surgery.', 'Prospectively collected data were analysed on 7621 consecutive patients not requiring preoperative renal-replacement therapy, who underwent CABG, valve surgery or combined procedures from 1/1/98 to 1/12/06. Preoperative estimated glomerular filtration rate was calculated using Cockcroft-Gault formula. Patients were classified in the four chronic kidney disease (CKD) stage classes defined by the National Kidney Foundation Disease Outcome Quality Initiative Advisory Board. Late survival data were obtained from the UK Central Cardiac Audit Database.', 'There were 243 in-hospital deaths (3.2%). There was a stepwise increase in operative mortality with each CKD class independent of the type of surgery. Multivariate analysis confirmed CKD class to be an independent predictor of in-hospital mortality (class 2 OR 1.45, 95% CI 1.1-2.35, p=0.001; class 3 OR 2.8, 95% CI 1.68-4.46, p=0.0001; class 4 OR 7.5, 95% CI 3.76-15.2, p=0.0001). The median follow-up after surgery was 42 months (IQR 18-74) and there were 728 late deaths. Survival analysis using a Cox regression model confirmed CKD class to be an independent predictor of late survival (class 2 HR 1.2, 95% CI 1.1-1.6, p=0.0001; class 3 HR 1.95, 95% CI 1.6-2.4, p=0.0001; and class 4 HR 3.2, 95% CI 2.2-4.6, p=0.0001). Ninety-eight percent (7517/7621) of patients had a preoperative creatinine <200 micromol/l, which is not included as a risk factor in most risk stratification systems.'] Does mild renal dysfunction predict in-hospital mortality and post-discharge survival following cardiac surgery?