Analysis of Renal Artery Hemodynamics in Normal Fetuses Using the Color Doppler Method

OBJECTIVE: From analysis of fetal renal artery hemodynamics, we attempted to reveal renal glomerular and tubular function in normal fetuses during pregnancy. DESIGN: The study included 36 cases of normal fetuses from the 20th to the 40th week of gestation; V(max) (the systolic peak velocity of main renal artery), V(mean) (time averages of trace of peak velocity) blood flow were initially measured between 20 and 24 weeks of gestation and every 4 weeks thereafter. The measurement was performed a total of five times in a longitudinal study. In addition, the blood flow waveform was concurrently examined. RESULTS: The V(max) was 22.02 +/- 0.50 cm/s at 20-24 weeks of gestation. This standard value (100%) was found to increase for each group as follows: 125.2, 149.1, 156.1, and 181.5%. Furthermore, using 20-24()weeks of gestation as the standard, the V(mean) increased after the 37th week of gestation: 186.7%, respectively. At 20-24 weeks of gestation, the blood flow wave forms consisted of 43.2% type I (only systolic waveforms), and 56.8% type II (both systolic and diastolic waveforms). Type III waveforms (waveforms that extended beyond the diastolic to the next systolic component) were not recognized. In the 33- to 36-week group, 82.6% of the waveforms were type II, and in the 37- to 40-week group, 76.2% of the waveforms were type III. CONCLUSIONS: The V(max) and V(mean) of the renal artery in normal fetuses exhibit a similar rate increase when 20-24 weeks of gestation is compared to 37-40 weeks of gestation. The blood flow waveforms changed as pregnancy progresses; thus, it was inferred that this finding was related to the development of the renal glomerular and renal tubular function.