Doppler velocimetry of maternal renal interlobar arteries in pregnancy-induced hypertension

Maternal and fetal artery Doppler findings in women with chronic hypertension who subsequently develop superimposed pre-eclampsia

OBJECTIVE

To carry out a prospective study of Doppler velocimetry of the fetomaternal circulation in women with chronic hypertension, to evaluate whether the subsequent development of superimposed pre-eclampsia can be predicted.

STUDY DESIGN

Serial Doppler studies of the maternal uterine and renal arteries, and fetal middle cerebral and umbilical arteries, were performed at 16-20 and at 28-32 weeks' gestation in 56 women with chronic hypertension. Pulsatility indices were compared using the Wilcoxon rank sum method. A p value of < 0.05 was considered significant.

RESULTS

Uterine artery impedance was significantly elevated as early as 16-20 and at 28-32 weeks' gestation, while the cerebroplacental ratio was lower at 28-32 weeks' gestation, in the 14 women who developed superimposed pre-eclampsia. The maternal renal artery impedance remained constant throughout gestation, regardless of the development of pre-eclampsia.

CONCLUSIONS

Uterine artery Doppler velocimetry at 16-20 and at 28-32 weeks' gestation showing increased impedance is predictive for the development of superimposed pre-eclampsia in women with chronic hypertension. The cerebroplacental ratio suggested early fetal brain sparing at 28-32 weeks' gestation in these women.

Reproducibility of pulsed Doppler measurements of the maternal renal circulation in normal pregnancies and those with pregnancy-induced hypertension

OBJECTIVE

To assess the inter- and intraobserver reproducibilities of pulsed Doppler measurements of the maternal renal circulation in normal pregnancies and those affected by pregnancy-induced hypertension.

MATERIALS AND METHODS

Color and pulsed Doppler ultrasound was used to measure acceleration time and resistance index in the renal segmental and interlobar arteries. For the investigation of interobserver reproducibility, two sonographers performed measurements blindly in six normal pregnant women and 14 women with pregnancy-induced hypertension between 28 and 36 weeks' gestation. A second group of 10 patients between 30 and 35 weeks' gestation were examined by one sonographer to assess the level of intraobserver reproducibility of measurements. For each patient in this group, the flow waveform was measured three times in succession. Calculations of the intraclass correlation coefficient Ri were used to determine the level of reproducibility.

RESULTS

The interobserver Ri and intraobserver Ri for acceleration time in the segmental artery were 0.95 and 0.96 and for the interlobar artery they were 0.97 and 0.98, respectively. For the resistance index, these values were 0.01 and 0.01 in the segmental artery and 0.52 and 0.29 in the interlobar artery.

CONCLUSION

Both the inter- and intraobserver reproducibility of acceleration time measurements in the renal segmental and interlobar arteries were clinically acceptable but the equivalent reproducibilities of resistance index measurements were poor.

Doppler velocimetry of maternal renal circulation in pregnancy-induced hypertension

PURPOSE

The purpose of this study was to evaluate whether the Doppler waveforms of the maternal main renal, segmental, and interlobar arteries are altered in women with pregnancy-induced hypertension (PIH) compared with healthy pregnant women.

METHODS

Flow waveforms of the maternal main renal, segmental, and interlobar arteries were obtained from 42 healthy pregnant women between 24 and 41 weeks of gestation and 21 women with PIH between 28 and 40 weeks of gestation using pulsed Doppler sonography. We used spectral analysis to measure the peak systolic and end-diastolic velocities and the acceleration time. The presence or absence of the normal early systolic compliance peak-reflective-wave complex (ESP) was assessed in only the main renal artery.

RESULTS

The acceleration times of the segmental and interlobar arteries were significantly prolonged in the PIH group compared with those in the healthy pregnant women. Of the 21 women with PIH, 3 showed loss of the ESP in the renal artery, but these changes were not significant.

CONCLUSIONS

Decreased systolic acceleration and the absence of ESP, the hemodynamic indicators for significant proximal stenosis, suggest that severe stenosis or continuous vasospasm in the proximal arteries, such as the main renal or segmental artery, may be implicated in the pathogenesis of PIH.

Pulsed Doppler US findings of renal interlobar arteries in pregnancy-induced hypertension

PURPOSE

To evaluate whether Doppler ultrasonographic (US) velocimetry in renal interlobar arteries is altered in women with pregnancy-induced hypertension (PIH) compared with that in healthy pregnant and nonpregnant women.

MATERIALS AND METHODS

Flow waveform measurements in renal interlobar arteries were obtained in 39 nonpregnant women, 77 healthy pregnant women at 16-40 weeks gestation, and 15 women with PIH at 28-39 weeks gestation by using color and pulsed Doppler US.

RESULTS

In the nonpregnant group, the mean (+/- SD) peak systolic velocity, end-diastolic blood flow velocity, resistive index, and acceleration time were 0.34 m/sec +/- 0.08, 0.14 m/sec +/- 0.03, 0.62 m/sec +/- 0.07, and 52.3 m/sec +/- 13.7, respectively. In the healthy pregnant group, the peak systolic and end-diastolic blood flow velocities at 16 weeks gestation had decreased greatly by 40 weeks gestation. However, the values of other indexes in this group did not change with gestational age. In the PIH group, the acceleration time values were greatly prolonged compared with those in the other groups.

CONCLUSION

Acceleration time is one of the hemodynamic parameters of substantial upstream stenosis. These findings suggest that severe stenosis or continuous vasospasm in the proximal arteries, such as the main renal artery and segmental artery, might be implicated in the pathogenesis of PIH.

Doppler assessment of the maternal interlobar renal and uterine arteries in mid-pregnancy in women at low and high risk for pregnancy-induced hypertension

PURPOSE

The purpose of this study was to examine the relationship between vascular resistance of the maternal intrarenal arteries and the main uterine arteries in pregnant women at low and high risk for pregnancy-induced hypertension.

METHODS

The resistance indices (RIs) in the main uterine arteries and the interlobar branches of the right renal artery were measured by duplex Doppler sonography in 338 pregnant women at 21-24 weeks of gestation, including 175 women at high risk for pregnancy-induced hypertension. Of those, 54 patients had repeat Doppler measurements during pregnancy.

RESULTS

Cross-sectional data showed no correlation between the RIs in the right interlobar renal arteries and either uterine artery. Furthermore, no relationship existed between persistent diastolic notching in the uterine arteries and the RI in the renal circulation. The mean renal artery RI was 0.62. Compared to that in patients with a normal outcome, the renal artery RI was not significantly different in patients who developed proteinuric pregnancy-induced hypertension (PPIH) or severe pregnancy-induced hypertension (PIH) later during pregnancy. Multiple analysis of variance for longitudinal data showed no correlation between the RI in the maternal renal arteries and gestational age, severe PIH, or PPIH.

CONCLUSIONS

The RIs in the maternal intrarenal arteries and the main uterine arteries are not related to each other in pregnant women, even in patients with abnormal uterine artery Doppler findings, severe PIH, or PPIH.