Inability of color and spectral Doppler to identify fetal renal obstruction.

Color flow Doppler imaging was used to obtain fetal renal artery flow velocity waveforms in 130 normal fetuses at various gestational ages to build a database for the establishment of normal ranges for the Pulsatility Index in the fetal renal arteries throughout pregnancy. Twenty-nine cases of fetal renal tract dilation (greater than 5 mm anteroposterior diameter of the renal pelvis) of various causes were investigated. We found that measurements of the pulsatility index were not significantly altered from the normal range, so that color flow Doppler does not appear to be helpful in the differential diagnosis of fetal renal dilation.