Investigations of renal artery blood flow velocity in preterm and term neonates by pulsed Doppler ultrasonography.

So far, echo-Doppler studies of the renal arteries have only been performed in adult subjects. They dealt with qualitative parameters of blood flow, but absolute velocity values could not be determined. This paper presents a method for measurement of absolute values of renal artery blood flow velocity in infancy with a well-defined steep angle of insonation of less than 25 degrees by using a range-gated Doppler system with Duplex-scan. The renal blood flow patterns were studied at specified sites by placement of the transducer below the costal arches on the right flank and left flank, respectively. Thus, a reference collective of 65 infants (26-40 weeks of gestational age, 650-3990 g body weight and 1-145 days of postnatal age at the time of examination) were studied. The time mean of maximum velocity significantly increased with the body weight from 17 cm/s below 1000 g to 29 cm/s above 3000 g of body weight. Whereas the pulsatility indices were independent of body weight. The reproducibility of the method, coefficient of variation (CV) 3%-9%, is comparable with the studies of cerebral vessels.