We performed an observational prospective cohort study on the applicability of two-dimensional echocardiography with pulsed Doppler technique as a noninvasive modality to serially evaluate renal blood velocities in premature neonates with and without umbilical artery catheters. We also sought to determine the incidence of umbilical artery catheter-related thrombus formation in our neonatal intensive-care unit. We established normative values for renal artery blood flow velocities in premature neonates and postulate that this echo-Doppler technique is valid and can be used to evaluate renal developmental physiology in the neonatal population. In addition, we observed that even in the absence of clinical sequelae due to thrombus formation, the presence of a thrombus in the aorta caused abnormalities in renal hemodynamics.