Renal Artery Pulsatility Index Research Articles

Renal artery Doppler findings in fetuses of mothers with preeclampsia

Objectives: Preeclampsia (PE), which affecting multi-organ systems, is one of the most common causes of feto-maternal morbidity and mortality. The fetal kidney is one of the vulnerable organs in PE caused by sustained vasospasm of the renal arteries. In this study, it was aimed to reveal the changes in the renal vascular bed with renal artery Doppler examinations in fetuses of pregnant women with PE. Methods: Fifty-five pregnant women with PE and 60 healthy pregnant women were included in this prospective study. Multiple pregnancies, those who did not want to participate in the study, and those with other co-morbidities were excluded from the study. Fetal renal artery Doppler studies included renal artery systolic/diastolic (S/D) ratio, pulsatility index (PI) and resistance index (RI) of the control and PE groups, and findings such as week of birth and birth weight were recorded and analyzed statistically. Results: Fetal renal artery PI values were found to be higher in pregnant women with PE compared to the control group (2.93 in the patient group, 2.28 in the control group, p < 0.001). There was no significant difference between RI values and S/D ratios between the two groups. In the preeclampsia group, gestational week and baby weight at birth were significantly lower. Conclusions: Due to preeclampsia, hypoxia occurs in peripheral tissues and organs at the maternal level. Fetal organs are also affected by these hypoxic conditions. Doppler is an extremely useful examination tool in the evaluation of the status of peripheral organs such as the kidney. This study suggests that PE increases the resistance of renal arteries in fetuses of mothers with PE compared to fetuses of mothers without PE, which may contribute critically to kidney disease later in life.

The renal artery pulsatility index enables real-time monitoring of acute kidney injury after digestive surgery

BackgroundPostoperative acute kidney injury after digestive surgery can be a critical problem that causes morbidity or mortality. Although serum creatinine reflects the renal function, it takes time to measure, and only severe renal failure induces an increase in creatinine. We tried to calculate the renal artery pulsatility index as a parameter to enable the real-time monitoring of acute kidney injury, which can be measured by routine bedside ultrasonography. This study aimed to evaluate the accuracy of the renal artery pulsatility index for the early detection of acute kidney injury after digestive surgery. MethodsOne hundred consecutive patients who underwent digestive surgery in a single institution from March to July 2018 were included. The renal artery pulsatility index was measured at 4 time points (preoperative day, postoperative day 1, postoperative day 4, and postoperative day 7). Perioperative acute kidney injury I was defined as a >0.3 mg/dL increase in serum creatinine and a serum creatinine level of >1.0 mg/dL at any postoperative time point. The association of the renal artery pulsatility index with perioperative acute kidney injury was analyzed. ResultsThe preoperative renal artery pulsatility index (average 1.4) was significantly high in aged patients and those with diabetes mellitus, hypertension, or chronic kidney disease. Furthermore, a high preoperative renal artery pulsatility index (cut-off: 1.6) was a predictor of perioperative acute kidney injury (n = 13). Moreover, the postoperative renal artery pulsatility index significantly increased in acute kidney injury cases. ConclusionThe renal artery pulsatility index was strongly correlated with acute kidney injury in the perioperative period. It appears to be an effective and less invasive procedure for the real-time monitoring that enables the early detection of acute kidney injury after digestive surgery.

Fetal left ventricular modified myocardial performance index and renal artery pulsatility index in pregnancies with isolated oligohydramnios before 37 weeks of gestation

Objective:The aim was to evaluate fetal left modified myocardial performance index (Mod-MPI) and renal artery Doppler parameters in fetuses with isolated oligohydramnios and a normal amount of amniotic fluid.Material and Methods:This was a prospective cohort study; 25 pregnancies with isolated oligohydramnios and 25 healthy, gestational age-matched controls, between 24+0 to 36+6 weeks of gestation, were recruited. Primary outcome was to compare left modified MPI and mean fetal renal artery pulsatility index (PI). The secondary outcome was to compare adverse perinatal outcomes between the groups.Results:Mean Mod-MPI was significantly higher (p=0.001) and isovolumetric relaxation time was longer (p=0.009) in the isolated oligohydramnios group. Mean renal artery PI values were not different between the groups. Birthweight (p=0.041) and gestational age at birth (p=0.001) were significantly lower, and incidences of delivery before 37 weeks (p=0.034) and Cesarean section due to non-reassuring fetal heart rate testing (p=0.021) were significantly higher in women with isolated oligohydramnios than the control group. We found no significant relationship between Mod-MPI and adverse perinatal outcomes.Conclusion:Fetuses with isolated oligohydramnios have increased left Mod-MPI, which may be due to mild cardiac diastolic dysfunction. Increased Mod-MPI is not associated with adverse perinatal outcomes and does not seem to help in the management of pregnancies before 37 weeks of gestation with isolated oligohydramnios.

Evaluation of Fetal Renal Artery Doppler Indices in Pregnancies Complicated with Preeclampsia

Objective: Preeclampsia, characterized by endothelial dysfunction, is associated with maternal and fetal Doppler alterations. This study aimed to evaluate fetal renal artery Doppler indices in pregnancies complicated with preeclampsia and compare them with normotensive pregnancies. Design: This cross-sectional study enrolled 46 pregnancies complicated with preeclampsia between weeks 24 and 37 of gestation as the study group and 48 normotensive pregnancies as the control group. Materials and Methods: The abdominal aorta, its bifurcation, and the renal arteries were visualized in the coronal view of the fetal abdomen using color Doppler. Renal artery Doppler indices were measured after arising from the abdominal aorta. The angle of insonation was ≤30° from the direction of blood flow, and the sample volume was 2 mm. Fetal renal artery pulsatility index, resistance index, systolic/diastolic ratio, and peak systolic velocity (PSV) were measured. All Doppler measurements were performed in the absence of fetal movements. Moreover, demographic characteristics and the perinatal outcome data of patients were recorded. Results: The values of fetal renal artery pulsatility and resistance indices were found to be significantly lower in the study group than those in the control group (p < 0.001 and p = 0.013, respectively). The fetal renal artery systolic/diastolic ratio and PSV values were also significantly lower in the study group compared with those in the control group (p = 0.007 and p < 0.001, respectively). Renal artery pulsatility and resistance indices were negatively correlated with mean arterial pressure (r = −0.381, p < 0.001 and r = −0.267, p = 0.009, respectively). The renal artery systolic/diastolic ratio was also significantly negatively correlated with the mean arterial pressure (r = −0.257, p = 0.013). Limitations: The main limitations of this study are its cross-sectional design and the small number of participants. Another limitation of the study is that preeclamptic pregnancies complicated with fetal growth restriction were not included. Conclusion: The observed decrease in fetal renal artery Doppler impedance may be caused by the unique response of the fetal renal artery to the factors involved in the etiopathogenesis of preeclampsia than other fetal peripheral vessels. These changes in fetal renal artery indices in pregnancies complicated with preeclampsia could be taken into account in the assessment of fetal health.

Fetal renal artery blood flow - Normal ranges.

The study objectives were to develop standard charts for fetal renal artery blood flow to define normal ranges and to assess the reliability of the measurements. This prospective, longitudinal study reviewed 72 low-risk singleton pregnancies who had serial ultrasound examinations. Pulse wave Doppler was used to obtain the resistivity and pulsatility indices of the fetal renal arteries. Standard charts of the fetal renal arteries were created using mixed effects modelling and the intra- and interobserver reliability for the renal blood flow measurements was analysed. Standard charts of the normal ranges of the renal artery resistive index (RI) and pulsatility index (PI) of the fetal renal arteries were created. The 3rd, 5th, 10th, 50th, 90th, 95th and 97th centiles were calculated. The intraclass correlation coefficient was acceptable for intraobserver reliability (RI = 0.66, PI = 0.88) and poor for interobserver reliability (RI = 0.11, PI = -0.56). These novel charts demonstrate the change of the fetal renal artery blood flow during pregnancy. These may be used in clinical practice to detect variations from these normal ranges and be useful in future studies of kidney function projection.

Use of the Renal Artery Doppler to Identify Small for Gestational Age Fetuses at Risk for Adverse Neonatal Outcomes.

Objective: To measure the sensitivity and positive predictive value (PPV) for an adverse neonatal outcome among growth-restricted fetuses (FGR) comparing the cerebral–placental ratio (CPR) with the cerebral–renal ratio (CRR). Methods: Retrospective analysis of 92 women who underwent prenatal ultrasound at the University of Maryland and the University of Padua. Renal, middle cerebral and umbilical artery Doppler waveforms were recorded for all scans during the third trimester. The last scan prior to delivery was included for analysis. We calculated the test characteristics of the pulsatility indices (PI) of the umbilical and renal arteries in addition to the derived CPR and CRR to detect a composite adverse neonatal outcome. Results: The test characteristics of the four Doppler ratios to detect increased risk for the composite neonatal outcome demonstrated that the umbilical artery pulsatility index had the best test performance (sensitivity 64% (95% CI: 47–82%), PPV 24% (95% CI: 21–27), and positive likelihood ratio 2.7 (95% CI: 1.4–5.2)). There was no benefit to using the CRR compared with the CPR. The agreement between tests was moderate to poor (Kappa value CPR compared with CRR: 0.5 (95%CI 0.4–0.70), renal artery PI:−0.1 (95% CI −0.2–0.0), umbilical artery PI: 0.5 (95% CI 0.4–0.7)). Only the umbilical artery had an area under the receiver operating curve that was significantly better compared with the CPR as a reference (p-value < 0.01). Conclusions: The data that we present do not support the use of renal artery Doppler as a useful clinical test to identify a fetus at risk for an adverse neonatal outcome. Within the various indices applied to this population, umbilical artery Doppler performed the best in identifying the fetuses at risk for an adverse perinatal outcome.

Decreased biventricular myocardial deformation in fetuses with lower urinary tract obstruction

BackgroundTo observe myocardial deformations in fetuses with isolated lower urinary tract obstruction (LUTO) and identify the correlation between myocardial deformation and the severity of obstruction.MethodsThe strain (S), strain rate in systole (SRs) and strain rate in diastole (SRd) of the left and right ventricles at the first examination were prospectively analyzed and compared between fetuses with isolated LUTO and gestational age (GA)-matched normal control fetuses. Multiple regression analyses were used to assess the obstructive factors for impaired strain and strain rate, and the independent variables included bladder volume, sum of the bilateral pelvic diameters, sum of the bilateral ureteral diameters, mean bilateral renal artery pulsatility index, and amniotic fluid index.ResultsThirty-six fetuses with isolated LUTO and 36 normal controls were enrolled. Overall, decreased S, SRs and SRd of both ventricles were noted in fetuses with LUTO (p < 0.001). Moreover, S and SR were significantly negatively related to distended bladder volume (p < 0.001).ConclusionsFetuses with LUTO demonstrated decreased left and right myocardial deformation, and this impaired cardiac dysfunction was correlated with the urinary bladder volume. Evaluating the myocardial deformation in fetal LUTO could provide information to aid in parental counselling and intervention monitoring.

Effects of Klotho supplementation on hyperoxia-induced renal injury in a rodent model of postnatal nephrogenesis.

Hyperoxia (HO) causes kidney injury in preterm infants; however, whether these effects are modifiable is unknown. We hypothesized that administration of exogenous soluble Klotho, a kidney-derived antioxidant, would attenuate HO-induced kidney injury during postnatal nephrogenesis in rats. Sprague Dawley neonatal rats assigned to normoxia (21% O2) or HO (85% O2) groups from postnatal day (P) 1 to 21 were randomly assigned to receive alternate day intraperitoneal injections of recombinant Klotho or placebo for 3 weeks. They were recovered in normoxia for an additional 3 weeks and sacrificed at 6 weeks. Renal artery resistance and pulsatility indices, tubular injury scores, glomerular area, and renal antioxidant capacity were assessed. Rodents exposed to HO during postnatal nephrogenesis had reduced kidney Klotho expression, glomerulomegaly, and higher tubular injury scores. Exogenous Klotho administration improved renal perfusion as indicated by decreases in both resistance and pulsatility indices and increased antioxidant enzyme expression. HO exposure during postnatal nephrogenesis in rodents results in a decline in kidney Klotho expression, decreased renal perfusion, enlarged glomerular size, and tubular injury. The exogenous administration of Klotho attenuated HO-induced kidney injury and augmented antioxidant capacity.

Intima-media thickness of the common carotid arteries as a marker of retinopathy and nephropathy in sickle cell disease.

PurposeThis study was conducted to test the hypothesis that the carotid intima-media thickness (CIMT) is higher in patients with sickle cell disease (SCD) than in the normal population, and to determine the relationships of the CIMT with central retinal artery (CRA) and renal artery Doppler indices.MethodsForty-four confirmed steady-state SCD patients aged 16 years and above were recruited consecutively. The Doppler velocimetric indices of their right renal artery and both CRAs were obtained. The CIMT was also measured on each side via B-mode ultrasonography. The subjects were categorized by age and sex. Mean and median values for each group were determined. The Spearman correlation test was used to quantify the relationships between CIMT and the Doppler parameters.ResultsThe participants had a median age of 24.50 years (interquartile range, 12.50 to 36.50 years). Twenty-three were men (52.3%) and 21 were women (47.7%). The median CIMT was 0.70 mm (IQR, 0.50 to 0.90 mm). Significant correlations with the CIMT were found for the CRA peak systolic velocity (r=0.312, P=0.003), the renal artery resistivity index (RI) (r=0.284, P=0.007), and the renal artery pulsatility index (PI) (r=0.273, P=0.010). There was no significant relationship between the CIMT and the CRA end-diastolic velocity, CRA RI, or CRA PI.ConclusionCIMT in SCD patients was higher than in the previously reported age groups of the reference populations. In addition, the CIMT was significantly correlated with the CRA peak systolic velocity, the renal artery RI, and the renal artery PI.

Fetal renal blood flow velocimetry and cerebro-placental ratio in patients with isolated oligohydramnios

ObjectiveIt’s proposed that oligohydramnios is caused by decreased renal perfusion due to redistribution of fetal blood at fetal growth restriction. Isolated oligohydramnios refers to the presence of oligohydramnios without fetal structural and chromosomal abnormalities, without fetal growth restriction, without intrauterine infection, and in the absence of known maternal disease. It’s unknown whether the redistribution or decreased renal perfusion cause isolated oligohydramnios. The aim of the study was to evaluate fetal renal artery Doppler blood velocimetry and cerebro-placental ratio (CPR) among women with isolated oligohydramnios between 25–40 weeks of gestational age. Study designThe middle cerebral artery, umbilical artery and, renal artery pulsatility index (PI) values were measured in 45 fetuses with isolated oligohydramnios and 65 fetuses with normal amniotic fluid. Oligohydramnios was defined as deepest vertical amniotic fluid being measured lower than 1cm. The CPR (middle cerebral artery PI/umbilical artery PI) and renal artery PI values were expressed as multiples of the normal median (MoM) and were compared between the two groups. ResultsThere was no difference in MoM of CPR PI (p=0.167) and MoM of renal artery PI values (right p=0.253, left p=0.353) between the groups. ConclusionThe renal artery Doppler velocimetry and CPR were not significantly different in the women with isolated oligohydramnios, compared to the women with normal amniotic fluid.

Has GnRH a direct role in amh regulation?

It’s proposed that oligohydramnios is caused by decreased renal perfusion due to redistribution of fetal blood at fetal growth restriction. Isolated oligohydramnios refers to the presence of oligohydramnios without fetal structural and chromosomal abnormalities, without fetal growth restriction, without intrauterine infection, and in the absence of known maternal disease. It’s unknown whether the redistribution or decreased renal perfusion cause isolated oligohydramnios. The aim of the study was to evaluate fetal renal artery Doppler blood velocimetry and cerebro-placental ratio (CPR) among women with isolated oligohydramnios between 25–40 weeks of gestational age.The middle cerebral artery, umbilical artery and, renal artery pulsatility index (PI) values were measured in 45 fetuses with isolated oligohydramnios and 65 fetuses with normal amniotic fluid. Oligohydramnios was defined as deepest vertical amniotic fluid being measured lower than 1 cm. The CPR (middle cerebral artery PI/umbilical artery PI) and renal artery PI values were expressed as multiples of the normal median (MoM) and were compared between the two groups.There was no difference in MoM of CPR PI (p = 0.167) and MoM of renal artery PI values (right p = 0.253, left p = 0.353) between the groups.The renal artery Doppler velocimetry and CPR were not significantly different in the women with isolated oligohydramnios, compared to the women with normal amniotic fluid.

Renal artery Doppler compared with the cerebral placental ratio to identify fetuses at risk for adverse neonatal outcome

Background: Current clinical practice incorporates an umbilical artery resistance index or a ratio of the middle cerebral artery (MCA PI) to the umbilical artery pulsatility index (UA PI) known as the cerebral placental ratio (CPR) to assess wellbeing in the small for gestational age fetus. Previous reports using the renal artery Doppler indices have not been consistent in regards to their design and clinical use. Our objective is to develop reference values for renal artery Doppler indices and validate their use compared with the UA PI or CPR to identify fetuses that will develop a composite neonatal outcome.Methods: We performed 9700 ultrasounds among 2852 women at 20–40 weeks of gestation at the University of Maryland between 1 June 2016 and 1 December 2016. Nomograms were first developed using one randomly selected scan from each of a subgroup of 860 women without any comorbidities. The nomograms were validated among a cohort of 550 women who subsequently delivered at the University of Maryland Medical Center. We compared the area under the receiver operating characteristic curve (AUROC) between the CPR and UA PI, and the renal artery Doppler parameters (renal artery pulsatility index (RA PI), systolic diastolic ratio (RA SDR), and peak systolic velocity (RA PSV)). The primary outcome was the development any one of the composite neonatal outcome components (death, intensive care unit admission, ventilator for more than 6 h, hypoxic ischemic encephalopathy or necrotizing enterocolitis) or admission to the neonatal intensive care unit (NICU) for any indication.Results: The renal artery Doppler indices did not improve identification of fetuses that would subsequently develop one of the components of the composite neonatal outcome (AUROC for CPR 0.54, 95% CI (0.49–0.59), versus the UA PI: 0.59 (0.54–0.64) p = .07, the RA PI: 0.51 (0.48–0.55) p = .41, RA SDR 0.54 (0.49–0.58) p = .99, or RA PSV 0.51 (0.47–0.55) p = .37). There was no difference when comparing AUROC to detect NICU admission (AUROC for CPR 0.53, 95% CI (0.49–0.58), versus the UA PI: 0.57 (0.52–0.62) p = .14, the RA PI: 0.50 (0.47–0.54) p = .44, RA SDR: 0.54 (0.50–0.59) p = .62 or RAPSV: 0.51 (0.47–0.55) p = .54).Conclusion: The renal artery indices do not improve detection of fetuses at risk for adverse neonatal outcomes compared with the CPR or the UA PI.

Predictive value of fetal renal artery Doppler indices in idiopathic oligohydramnios and polyhydramnios

Objective The aim of this work was to study the relation of renal artery (RA) and umbilical artery (UA) flow velocity waveforms and amniotic fluid volume in normal pregnancies and those complicated by either polyhydramnios or oligohydramnios. Background There is a relation between RA and UA flow velocity waveforms and amniotic fluid volume in normal pregnancies and those complicated by either polyhydramnios or oligohydramnios. Patients and methods All patients were enrolled from patients attending the outpatient clinic of El-Galaa Maternity Teaching Hospital. All patients were matched for maternal age, gestational age, and parity at the time of sonography, comparing RA Doppler indices pulsatility index (PI) and resistance index at 22, 28, and 34 weeks in three groups. Group I consisted of 20 patients of normal amniotic fluid index, group II consisted of 20 patients with oligohydramnios, and group III consisted of 20 patients with polyhydramnios. Results RA PI values were higher in group II than group I at 22 weeks, 28 weeks, and 34 weeks. The PI value at 28 weeks of gestation was statistically significant (P = 0.016). At 28 weeks of gestation, group II also had higher UA PI and resistance index values than group I. Conclusion An increase in RA PI develops in early pregnancy before the development of oligohydramnios. In pregnancies developing polyhydramnios, RA PI was lower.

Cardiovascular Hemodynamic Changes After Antenatal Corticosteroids in Growth Restricted and Appropriate for GestationalAge Fetuses.

To investigate hemodynamic effects after antenatal corticosteroids (ACS) administration in appropriate for gestational age (AGA) and early growth restricted (GR) fetuses by measurement of Doppler cardiovascular function parameters. Prospective cohort study. AGA and GR singleton pregnancies receiving ACS for fetal lung maturation between 24 + 0-33 + 6 weeks were enrolled. Feto-placental vascular hemodynamics were studied by: umbilical artery (UA) pulsatility index (PI), middle cerebral artery (MCA) PI, renal artery (RenA) PI. Cardiac function was evaluated by ductus venosus (DV) PI and by echocardiographic parameters: E to A wave ratios (E/A) and mitral and tricuspid annular plane systolic excursion (MAPSE and TAPSE) for diastolic function, left and right myocardial performance index (MPI) for overall (diastolic and systolic) function. A single operator performed all the measurements at 3 different time points (E): E0 before or within 4 hours of ACS administration (baseline examination), E1 24-48 hours after the first dose and E2 7 days after the second dose of ACS. The values were expressed as z-scores. Pairwise comparisons with paired t-test were performed to compare measurements before and after exposure to ACS. 25 AGA and 20 GR fetuses (mean gestational age: 31 + 1 and 30 + 6, respectively) were included in the analysis. In the AGA group ACS administration was associated with a significant reduction in UA PI. In the GR fetuses ACS temporarily (E0-E1) restored UA-end diastolic flow (EDF) in 6 of 9 fetuses with A/R-EDF ("Return of EDF phenomenon") and produced a significant increase (worsening) in right MPI (both in E1-E2 and in E0-E2). ACS administration is associated with UA vasodilation in both AGA and GR fetuses and with an increase in right MPI in the latter group. This suggests a worsening in cardiac function in GR fetuses.

The Relationship between the Fetal Volume-Corrected Renal Artery Pulsatility Index and Amniotic Fluid Volume

Introduction: To evaluate if the volume-corrected renal artery pulsatility index (vcRA-PI) is more closely related to the amniotic fluid level than the uncorrected or the gestational age (GA)-adjusted RA-PI. Methods: RA-PI and kidney volume were measured in low- and high-risk pregnancies at 17–38 weeks. Fetal anomalies associated with nonrenal causes of abnormal amniotic fluid volume were excluded. The vcRA-PI was calculated by dividing the RA-PI by the renal volume. The RA-PI was adjusted for GA, to obtain the GA-adjusted RA-PI. The uncorrected, GA-adjusted, and the vcRA-PI were related to the amniotic fluid level using nonparametric tests and receiver operating characteristic (ROC) curve analyses. Results: 146 examinations from 59 pregnancies were reviewed. Of these, 16 had oligo- and 15 had polyhydramnios. A higher vcRA-PI was associated with oligohydramnios (OR 2.54, 95% CI 1.67–3.86, p < 0.001), while the uncorrected RA-PI and GA-adjusted RA-PI were not able to predict oligohydramnios. ROC curve analysis showed a high predictive accuracy of the vcRA-PI for oligohydramnios (AUC 0.84, 95% CI 0.72–0.94). On the other hand, the uncorrected RA-PI and GA-adjusted RA-PI significantly predicted polyhydramnios (p = 0.04 and 0.02, respectively), while the vcRA-PI did not. Conclusion: The vcRA-PI is superior to the uncorrected and the GA-adjusted RA-PI in predicting oligohydramnios.

Perinatal outcomes in uncomplicated late preterm pregnancies with borderline oligohydramnios

Purpose: The purpose of this study is to determine the adverse perinatal outcomes in uncomplicated late preterm pregnancies with borderline oligohydramnios.Methods: A total of 430 pregnant women with an uncomplicated singleton pregnancy at a gestational age of 34 + 0–36 + 6 weeks were included. Borderline oligohydramnios was defined as an amniotic fluid index (AFI) of 5.1–8 cm, which was measured using the four-quadrant technique. Adverse perinatal outcomes were compared between the borderline and normal AFI groups.Results: Approximately 107 of the 430 pregnant women were borderline AFI, and 323 were normal AFI. The demographic and obstetric characteristics were similar in both groups. Delivery <37 weeks, cesarean delivery for non-reassuring fetal heart-rate testing, meconium-stained amniotic fluid, Apgar 5 min <7, transient tachypnea of the newborn, respiratory distress syndrome, neonatal intensive care unit, and hyperbilirubinemia were not statistically different between the groups (p = .054, p = .134, p = .749, p = 0.858, p = .703, p = .320, p = .185, and p = .996, respectively). Although gestational age was full-term, induction of labor rates were significantly higher in the borderline AFI group (p = .040). In addition, fetal renal artery pulsatility index pulsatility index (PI) was significantly lower in the borderline AFI group than in the normal AFI group (p = .014).Conclusion: Our results indicated that borderline AFI was not a risk for adverse perinatal outcomes in uncomplicated, late preterm pregnancies.

Renal Artery Doppler Findings in the Patients with Polyhydramnios before and after the Conservative Treatment.

The aim of this study was to evaluate the foetal renal blood flow with colour Doppler ultrasonography. Patients with polyhydramnios were investigated for the foetal renal artery pulsatility index (PI) at the beginning of the treatment, and after the conservative treatment in those who reached the normal amniotic fluid index. In this prospective study, 39 foetuses with polyhydramnios were evaluated at gestational weeks 26 to 36. The foetal development parameters, right and left foetal renal artery PIs, and amniotic fluid index were measured at the beginning of the treatment in all of these patients. Of these patients, 19 who responded to the conservative treatment were also revaluated when their amniotic fluid index reached normal levels, and statistical analyses were performed for the renal artery PIs before and after the treatment. In this study, 19 patients fulfilled the inclusion criteria as patients with polyhydramnios who responded to conservative treatment. For these patients, the mean foetal renal artery PI was 2.08 (range 1.5-3.0) at the first sonographic examination, and the mean foetal renal artery PI was 1.94 (range 1.53-2.69) after the conservative treatment. However, there was no statistically significant difference between these two groups (p=0.117). In this study, no statistically significant difference was found in the foetal renal artery PIs of the patients with polyhydramnios before and after the conservative treatment. These results suggest that the renal artery blood flow may not have any effect on the renal artery PI; therefore, these findings indicate that the renal artery PI cannot be used as a marker in the evaluation of polyhydramnios.

Predictive value of second and third trimester fetal renal artery Doppler indices in idiopathic oligohydramnios and polyhydramnios in low-risk pregnancies: a longitudinal study.

Intermittent assessment of renal artery flow velocity waveforms during the early stages of pregnancy may help in predicting changes in amniotic fluid dynamics. The current study sought to determine the relation of renal artery and umbilical artery flow velocity waveforms with normal pregnancies and pregnancies complicated by either polyhydramnios or oligohydramnios. Renal and umbilical artery Doppler values were evaluated at 22, 28 and 34 weeks' gestation in 300 low-risk pregnant women with singleton pregnancies. Pulsatility index (PI) and resistance index (RI) were recorded and the amniotic fluid volume was evaluated. Three groups were formed according to the amniotic fluid volume at birth. Group I consisted of 264 pregnant women with normal amniotic fluid, group II included 30 pregnant women with oligohydramnios and group III included six pregnant women with polyhydramnios. Doppler parameters were compared between the groups and within each group according to gestational age. Renal artery PI values were higher in group II than group I at 22 weeks, 28 weeks and 34 weeks. The PI value at 28 weeks' gestation was statistically significant (P = 0.011). At 28 weeks' gestation, group II also had higher umbilical artery PI and RI values than group I. An increase in renal artery PI develops in early pregnancy before the development of oligohydramnios. In pregnancies developing polyhydramnios, renal artery PI was lower; however, our study included a small number of women with polyhydramnios.

Mediation analysis of aortic stiffness and renal microvascular function.

Aortic stiffening, assessed by carotid-femoral pulse wave velocity, is associated with CKD. Transmission of excessive flow pulsatility into the low-impedance renal microvasculature may mediate this association. However, direct analyses of macrovascular-microvascular relations in the kidney are limited. Using arterial tonometry, iohexol clearance, and magnetic resonance imaging, we related arterial stiffness, GFR, urinary albumin excretion, and potential mediators, including renal artery pulsatility index, renal vascular resistance, and arterial volume in the cortex, in 367 older adults (ages 72-92 years) participating in the Age, Gene/Environment Susceptibility-Reykjavik Study. In a model adjusted for age, sex, heart rate, and body size, aortic stiffness was related to GFR (Slope of regression B=-2.28±0.85 ml/min per SD, P=0.008) but not urine albumin (P=0.09). After accounting for pulsatility index, the relation between aortic stiffness and GFR was no longer significant (P=0.10). Mediation analysis showed that 34% of the relation between aortic stiffness and GFR was mediated by pulsatility index (95% confidence interval of indirect effect, -1.35 to -0.29). An additional 20% or 36% of the relation was mediated by lower arterial volume in the cortex or higher renal vascular resistance, respectively, when offered as mediators downstream from higher pulsatility index (95% confidence interval of indirect effect including arterial volume in the cortex, -2.22 to -0.40; 95% confidence interval of indirect effect including renal vascular resistance, -2.51 to -0.76). These analyses provide the first evidence that aortic stiffness may contribute to lower GFR by transferring excessive flow pulsatility into the susceptible renal microvasculature, leading to dynamic constriction or vessel loss.

Fetal Renal Volume and Fetal Doppler in Normal and Growth Restricted Fetuses: Is there a Correlation?

Objective: To evaluate if umbilical, middle cerebral and fetal renal artery Doppler could affect fetal kidney volume in healthy and growth restricted fetuses after 26 weeks of gestation. Design: A prospective cross sectional study. Setting: Obstetrics& Gynecology department, Zagazig University, Egypt. Sample: One hundred ten pregnant women, 77 with normal fetal growth parameter, and 43 with IUGR fetuses. Methods: Fetal renal volume, combined and relative kidney volume were measured using 2-dimensional ultrasound. Umbilical, middle cerebral artery and fetal renal artery Doppler indices were examined. Main outcome measures: Correlation of Doppler parameter to fetal kidney volume, and association of fetal biometric indices to combined fetal kidney volume. Results: Combined and relative fetal kidney volume was significantly reduced in growth restricted fetuses than in normally grown fetuses 29% (95% CI, 18%-37%), for the former and 18% (95% CI, 3%-22) for the latter. All fetal biometric indices were positively associated with combined kidney volume. The largest effects were found for estimated fetal weight and abdominal circumference after adjustment for gestational age. No correlation exists between umbilical or middle cerebral artery Doppler and fetal renal volume. A significant negative correlation was found between fetal renal artery pulsatility index and fetal renal volume after adjustment for abdominal circumference. Conclusion: Increased fetal renal artery pulsatility index in growth restricted fetuses is negatively correlated with fetal kidney volume with resultant decreased renal perfusion and impaired nephrogensis.