Maternal renal and arcuate artery flow velocity waveforms in severe preeclampsia

Objectives: We previously reported that renal artery Doppler waveforms were not affected by hypertensive disorders of pregnancy. This seemed to disprove the concept of renal arteriospasm in preeclampsia. However, intrarenal shunting has been suggested as an explanation for these findings. The purpose of the study was to determine whether there is maternal renal cortical arteriospasm or an intrarenal shunting mechanism in severely preeclamptic women. Methods: Using color and pulsed Doppler we identified and insonated the right renal and arcuate arteries of 25 severely preeclamptic women delivered by cesarean section prior to the onset of labor and 25 normotensive pregnant women who were matched for maternal age, race, parity, and gestational age. Three recordings of the systolic/diastolic ratio, pulsatility index, and resistance index were obtained and averaged. Results: There was no difference in the renal or arcuate artery waveform indices in the severely preeclamptic or normotensive pregnant women. In preeclamptic women there was no correlation between the renal artery waveform indices and renal function tests and mean arterial blood pressure. The arcuate artery waveform indices in preeclamptic women were not correlated with renal function tests but had a significant positive correlation with mean arterial blood pressure. There was no correlation between the renal and arcuate artery waveform indices in normotensive women. Conclusions: The results are conflicting and do not allow for a firm conclusion. Comparisons of renal and arcuate artery Doppler waveform indices between preeclamptic and normotensive pregnant women did not demonstrate renal corticospasm or intrarenal shunting. On the other hand the relationship between the arcuate artery indices and mean arterial blood pressure in preeclamptics indicates that there is renal corticospasm with the possibility of intrarenal shunting. Further studies are needed for clarification. It may be that the Doppler techniques employed in this study are insensitive in capturing increases in vascular impedance in the vessels studied.