Abstract: Objective To evaluate the feasibility of using trans-esophageal echocardiogram (TEE) in dynamic monitoring of renal blood flow (RBF) in pediatric patient undergoing cardiac surgery and to identify potential factors that affect RBF during cardiopulmonary bypass (CPB). Methods Pediatric patient (n=46) undergoing open surgical repair for congenital heart defect were recruited in this study. Velocity of RBF and renal artery diameter were measured during surgery for calculating volumetric RBF. Cardiopulmonary bypass and hemodynamic data were recorded. Results RBF was measured successfully in 42 patients (91%). Resistance index of renal artery increased significantly after CPB compared to the preoperative stage. A strong linear correlation was found between perfusion volume (V_mean) and RBF. Non-linear correlation was found between mean arterial pressure and RBF. Conclusion Perfusion volume is the major factor that determines RBF during CPB. Measuring renal blood flow using TEE in pediatric patient is highly feasible and it can serve as dynamic renal perfusion monitoring during CPB.