Neonatal renal artery blood flow velocities using color Doppler ultrasonography

It is essential to evaluate the renal function for the management of high risk neonates. Color Doppler ultrasound technique can provide a useful information to evaluate the neonatal renal artery blood flow velocities. This study was performed to obtain the normative data of renal blood flow velocities in preterm and fullterm neonates and to compare the renal blood flow velocities with the aortic blood flow velocities. The normal volumetric state of fluid balance and renal function are essential in the management of the sick neonates.

The renal peak systolic blood flow velocity (renal PSFV), the renal mean blood flow velocity (renal MFV), the renal end diastolic blood flow velocity (renal EDFV) and the renal resistance index (renal RI) and also the cardiac output, the aortic peak systolic blood flow velocity (aortic PSFV) and the aortic mean blood flow velocity (aortic MFV) were serially recorded from one to 7 days after birth in 16 preterm and one to 5 days in 23 normal fullterm neonates.

The renal PSFV was significantly increased with the postnatal age, and the renal MFV was significantly increased between three and five days of age in the preterm neonates. In the fullterm neonates there was no significant change of the renal PSFV between one and five days of age, but the renal MFV was significantly increased between three and five days of age. There were no statistically significant differences of the renal PSFV, the renal MFV, the renal EDFV and the renal RI between the preterm and the fullterm neonates in the first five days after birth. The cardiac output in the preterm neonates was higher than that in the fullterm neonates: on day 3; 313 +/- 59 vs. 254 +/- 40 ml/kg/min. (p < 0.001) and on day 5; 357 +/- 95 vs. 280 +/- 35 ml/kg/min. (p < 0.01). The renal blood flow velocities were not significantly correlated with the aortic blood flow velocities in the normal fullterm neonates, whereas, in the preterm neonates the renal PSFV correlated with the cardiac output (r = 0.35, p < 0.01), the aortic PSFV (r = 0.45, p < 0.001) and the aortic MFV (r = 0.39, p < 0.01), and the renal MFV also correlated with the aortic PSFV (r = 0.30, p < 0.05) and the aortic MFV (r = 0.32, p < 0.05).

The increased renal flow velocities with the postnatal age in the preterm infants might depend on the increased cardiac output.