Quantitative three-dimensional power Doppler sonography for assessment of the fetal renal blood flow in normal gestation.

Renal blood flow is very important to fetal hemodynamics. To assess the development of fetal renal vascularization and blood flow in normal gestation, we measured the fetal renal vascularization and blood flow in healthy fetuses using three-dimensional (3-D) power Doppler sonography and quantitative 3-D power Doppler histogram analysis. This study was undertaken with a prospective, cross-sectional design. In total, 106 healthy singletons with gestational ages between 20 and 40 weeks were included. The 3-D power Doppler sonography and quantitative histogram analyses were used to assess the fetal renal vascularization index (VI), flow index (FI) and vascularization-flow index (VFI) in each case. Our results showed that all the VI, FI and VFI increased significantly with gestational age (GA). Using GA as the independent variable, the linear regression equations for fetal renal VI, FI and VFI were VI = 0.214 x GA - 3.5289 (r = 0.84, n = 106, p < 0.0001); FI = 0.3326 x GA + 35.224 (r = 0.33, n = 106, p < 0.001); and VFI = 0.1047 x GA - 1.8064 (r = 0.82, n = 106, p < 0.0001). Our study indicates that normal fetal renal vasculature and blood flow increase with the advancement of gestational age. In addition to our previous study for fetal renal volume using 3-D sonography, our data in this series may serve as a reference for further studies of fetal renal blood flow in abnormal conditions.