Background The aim of the study is to investigate the effects of the contrast media on the renal function in children with congenital heart disease, and to clarify the prophylactic efficacy of hydration.Methods Thirty-eight patients with ventricular septal defect or patent ductus arteriosus were to operation, and iopromide was conducted as contrast agent for interventional procedures.Accordance with the dose of 1.5 ml·kg-1·h-l,these patients were hydrated for 13-17 hours, the changes of creatinine and calculated GFR at the baseline and at 48hours after operation were recorded.