Abstract: Objective To investigate the alteration of renal microcirculation perfusion during cardiopulmonary bypass (CPB) in adult patients with contrast-enhanced ultrasound (CEU). Methods Six patients undergoing cardiac surgery with CPB and twelve patients undergoing non-cardiac surgery were enrolled and classified into CPB group and control group. CEU images of kidney were collected at the point of 30 min after CPB or 5 min after anesthesia induction respectively. Time intensity curve (TIC) was derived from three regions of interest (ROI): superficial cortex, deep cortex and medulla. Parameters including wash in slope ( α ), area under curve (AUC), peak intensity (PI) and time to peak (TTP) were calculated based on gamma-variant function. Results CEU showed a significant reduction of AUC in all three regions (superficial cortex, deep cortex and medulla) during CPB, compared with anesthetic condition. Ultrasound contrast agent-related adverse reactions were not occurred in all enrolled patients. Conclusion Renal microcirculation perfusion was dramatically reduced during CPB, especially in the medulla. CEU could be detected the renal microcirculation perfusion in the perioperative period of cardiac surgery.