Prospective evaluation of renal artery resistance and pulsatility indices in normal pregnant women

The Ultrasound Window Into Vascular Ageing: A Technology Review by the VascAgeNet COST Action

Non-invasive ultrasound (US) imaging enables the assessment of the properties of superficial blood vessels. Various modes can be used for vascular characteristics analysis, ranging from radiofrequency (RF) data, Doppler- and standard B/M-mode imaging, to more recent ultra-high frequency and ultrafast techniques. The aim of the present work was to provide an overview of the current state-of-the-art non-invasive US technologies and corresponding vascular ageing characteristics from a technological perspective. Following an introduction about the basic concepts of the US technique, the characteristics considered in this review are clustered into: 1) vessel wall structure; 2) dynamic elastic properties, and 3) reactive vessel properties. The overview shows that ultrasound is a versatile, non-invasive, and safe imaging technique that can be adopted for obtaining information about function, structure, and reactivity in superficial arteries. The most suitable setting for a specific application must be selected according to spatial and temporal resolution requirements. The usefulness of standardization in the validation process and performance metric adoption emerges. Computer-based techniques should always be preferred to manual measures, as long as the algorithms and learning procedures are transparent and well described, and the performance leads to better results. Identification of a minimal clinically important difference is a crucial point for drawing conclusions regarding robustness of the techniques and for the translation into practice of any biomarker.

The role of angiotensin II and relaxin in vascular adaptation to pregnancy

In brief

There is a pregnancy-induced vasodilation of blood vessels, which is known to have a protective effect on cardiovascular function and can be maintained postpartum. This review outlines the cardiovascular changes that occur in a healthy human and rodent pregnancy, as well as different pathways that are activated by angiotensin II and relaxin that result in blood vessel dilation.

Abstract

During pregnancy, systemic and uteroplacental blood flow increase to ensure an adequate blood supply that carries oxygen and nutrients from the mother to the fetus. This results in changes to the function of the maternal cardiovascular system. There is also a pregnancy-induced vasodilation of blood vessels, which is known to have a protective effect on cardiovascular health/function. Additionally, there is evidence that the effects of maternal vascular vasodilation are maintained post-partum, which may reduce the risk of developing high blood pressure in the next pregnancy and reduce cardiovascular risk later in life. At both non-pregnant and pregnant stages, vascular endothelial cells produce a number of vasodilators and vasoconstrictors, which transduce signals to the contractile vascular smooth muscle cells to control the dilation and constriction of blood vessels. These vascular cells are also targets of other vasoactive factors, including angiotensin II (Ang II) and relaxin. The binding of Ang II to its receptors activates different pathways to regulate the blood vessel vasoconstriction/vasodilation, and relaxin can interact with some of these pathways to induce vasodilation. Based on the available literature, this review outlines the cardiovascular changes that occur in a healthy human pregnancy, supplemented by studies in rodents. A specific focus is placed on vasodilation of blood vessels during pregnancy; the role of endothelial cells and endothelium-derived vasodilators will also be discussed. Additionally, different pathways that are activated by Ang II and relaxin that result in blood vessel dilation will also be reviewed.

Maternal renal artery Doppler sonographic changes in pregnancy-induced hypertension in South West Nigeria

BACKGROUND

To evaluate the renal arterial hemodynamic changes caused by pregnancy-induced hypertension using Doppler ultrasonography.

MATERIALS AND METHODS

Eighty (80) subjects with pregnancy-induced hypertension (PIH) and 160 controls (80 pregnant normotensive women and 80 healthy, non-pregnant women) underwent triplex renal sonography prospectively to determine their renal volumes and right renal artery Doppler indices.

RESULTS

The peak systolic velocity, end diastolic velocity, pulsatility index, systolic/diastolic ratio and acceleration time were respectively significantly higher in the PIH group (68.67 cm/s, 21.55 cm/s, 1.23, 3.38, 123.2 ms) than the pregnant, normotensive group (65.19 cm/s, 20.27 cm/s, 0.88, 3.35, 61.14 ms) and healthy, non-pregnant group (52.06 cm/s, 18.27 cm/s, 0.84, 2.90, 68.48 ms). Resistivity index was also increased in the PIH group, but this was not statistically significant. Conversely, the systolic acceleration was significantly lower in the PIH group (6.06 m/s(2)) compared to the pregnant, normotensive group (11.82 m/s(2)) and healthy, non-pregnant group (8.26 m/s(2)). The right renal volume of the PIH group (132.76 cm(3)) was significantly higher that of the pregnant, normotensive group (125.29 cm(3)) and healthy, non-pregnant group (91.66 cm(3)). The same pattern was observed in the left renal volume which was 168.78 cm(3), 164.95 cm(3) and 113.80 cm(3) in the study groups, respectively.

CONCLUSION

Renal Doppler ultrasound is clinically relevant in the diagnosis and follow-up of renal complications in patients with pregnancy-induced hypertension.

Ultrasonographic study and Doppler flow velocimetry of maternal kidneys and liver in low-risk pregnancy

OBJECTIVE

Longitudinal study with B-mode ultrasonography and Doppler ultrasonography of maternal kidneys and liver in low-risk pregnancy, to establish and quantify normality parameters, correlating them with physiological changes.

MATERIALS AND METHODS

Twenty-five pregnant women were assessed and selected to participate in the study, each of them undergoing four examinations at the first, second, third trimesters and postpartum.

RESULTS

Findings during pregnancy were the following: increased renal volume, pyelocaliceal dilatation with incidence of 45.4% in the right kidney, and 9% in the left kidney; nephrolithiasis, 18.1% in the right kidney, 13.6% in the left kidney. With pyelocaliceal dilatation, mean values for resistivity index were: 0.68 for renal arteries; 0.66 for segmental arteries; 0.64 for interlobar arteries; 0.64 for arcuate arteries. Without pyelocaliceal dilatation, 0.67 for renal arteries; 0.64 for segmental arteries; 0.63 for interlobar arteries; and 0.61 for arcuate arteries. Portal vein flow velocities presented higher values in pregnancy, with mean value for maximum velocity of 28.9 cm/s, and 22.6 cm/s postpartum. The waveform pattern of the right hepatic vein presented changes persisting in the postpartum period in 31.8% of the patients. Cholelithiasis was observed in 18.1% of the patients.

CONCLUSION

Alterations in renal volume, pyelocaliceal dilatation, nephrolithiasis, cholelithiasis, changes in portal vein flow velocity, alterations in waveform pattern of the right hepatic vein, proved to be significant.

A longitudinal study of the control of renal and uterine hemodynamic changes of pregnancy

We have determined the sequence and extent of maternal renal and uterine adaptation to pregnancy and examined the role of hormonal factors in their regulation. Renal bipolar diameter (RBD), renal artery resistance index (RARI), uterine artery pulsatility index (UAPI), and plasma relaxin, human chorionic gonadotropin (hCG), progesterone, estradiol, urea, and creatinine were measured longitudinally in women with normal spontaneous singleton pregnancies, in vitro fertilization (IVF) singleton pregnancies, ovum donation (OD) singleton pregnancies, and multiple pregnancies from prepregnancy to postpartum. There was a progressive increase in the RBD and the RARI and a decrease in the UAPI during pregnancy. These changes reversed toward prepregnancy levels by 6 weeks post delivery. There was no difference in the rate of change of RBD, RARI, and UAPI between spontaneous singleton, IVF singleton, OD singleton, and multiple pregnancies (p < 0.05), but relaxin was directly correlated to the RARI (r = 0.654, p = 0.015), and progesterone was inversely correlated to uterine artery PI (r = 0.554, p = 0.049). These data show that renal size and resistance to blood flow increase with advancing gestation, whereas the uterine artery resistance declined with gestation. These changes may be influenced by relaxin and progesterone.

Assessment of variability of renal blood flow Doppler parameters during the menstrual cycle in women

OBJECTIVE

To estimate variability of renal flow Doppler parameters during the menstrual cycle in young women, and to explore whether the parameters oscillate substantially throughout the cycle.

METHODS

The peak systolic, mean, and end-diastolic velocities, pulsatility (PI) and resistance (RI) indices, acceleration time (AT) and index (AI) of the right renal artery were measured nine times during the cycle with duplex sonography in 14 healthy women (age range, 23-25 years), and correlated with plasma concentrations of 17beta-estradiol and progesterone. Coefficient of variation (CV), interclass correlation (rho), and repeatability coefficients (RC) were used to measure the variability.

RESULTS

The measures of the variability for AI and AT were: CV = 45.4% and 37.3%; rho = 0.25 and 0.15; RC = 10.1 and 99.5, respectively. The CV for flow velocities varied from 24.1% to 25.5%, rho from 0.49 to 0.50, RC from 22.7 for end-diastolic to 63.3 for peak systolic velocity. The respective figures for PI and RI were: CV = 17% and 8.3%; rho = 0.21 and 0.29; RC = 0.53 and 0.15. Fluctuations of the flow parameters, hematocrit, hemoglobin, heart rate, and systolic blood pressure during the menstrual cycle were insignificant, while the diastolic blood pressure decreased by about 7 mmHg (P < 0.01) in the luteal phase.

CONCLUSION

The variability of renal flow Doppler parameters during the menstrual cycle in young healthy women is substantial. However, fluctuations of the values of the parameters throughout the cycle were non-significant.