Ultrasound On The Dynamic Monitoring Of The Fetal Urinary System

ObjectiveAn adverse fetal environment may lead to smaller kidneys and subsequent hypertension with renal disease in adult life. Measurement of renal size can be a useful aid to diagnose renal abnormalities. The purpose of this study is to establish reference values for Chinese fetal renal diameters and volume by two-dimensional and three-dimensional ultrasonography using the VOCAL (Virtual Organ Computer-Aided Analysis) method.Materials and methodsThis cross sectional study involved 197 healthy pregnant women who were examined between 15 and 38 weeks of pregnancy. Bland and Altman's graphical approach was utilized to investigate the agreement between intra-and inter-observer variability. Three fetal renal diameters (longitudinal, anteroposterior, and transverse diameters) were measured then each fetal kidney volume was evaluated separately using the VOCAL method with a 30 degree rotation angle. For each fetus, the mean and standard deviation measures were obtained for the left and right kidneys. The Wilcoxon test was used to evaluate the concordance between the left and right renal diameters and volumes. Polynomial regression models were constructed to assess the relationship between renal two-dimensional diameters, renal volumes and gestational age, adjusted by the coefficient of correlation(R) or coefficient of determination(R2).ResultsNineteen of renal two-dimensional samples were excluded because the kidney image quality was insufficient for correct visualization cause by bone shadowing, eleven of renal three-dimensional samples were excluded because the contour of kidney can not be clearly seen in the rotational process. Thus,375 renal diameters and 364 renal volumes were obtained.1. Renal two-dimensional diameters(1) The left renal diameters (longitudinal, anteroposterior, transverse diameters) increased from 1.18±0.09cm,0.82±0.08cm,0.76±0.05cm at 15-16 weeks to 4.26±0.36cm,2.48±0.26cm,2.45±0.34cm at 37-38 weeks. The right renal diameters increased from 1.23±0.06cm,0.82±0.13cm,0.75±0.09cm at 15-16 weeks to 4.10±0.32cm,2.65±0.29cm,2.47±0.44cm at 37-38 weeks.(2) There were no significant differences between the right and left renal two-dimensional diameters. Our results revealed that both renal diameters are highly correlated with the fetal gestational age (R= 0.945,0.920,0.898 for left kidney, R=0.937, 0.927,0.891 for right kidney, respectively).2. Renal three-dimensional volumes(1) The mean difference between repeated measures by the same examiner was-0.22cm3 (95%CI:-1.42 to 0.99cm3). The mean difference between repeated measures obtained by two different examiners was-0.40cm3 (95%CI:-2.48 to 1.69cm3).(2) The left renal volume increased from 0.47±0.15 cm3 at 15-16 weeks to 16.75±2.47 cm3 at 37-38 weeks. The right renal volume increased from 0.43±0.15 cm3 at 15-16 weeks to 15.47±2.54 cm3 at 37-38 weeks.(3) There were no significant differences between the right and left renal volumes. Our results revealed that both renal volumes are highly correlated with the fetal gestational age. (R2= 0.857 and 0.876, respectively).3. There were good correlation between abdominal circumference, longitudinal diameter and renal volume.ConclusionReference values were generated for fetal renal diameters and volumes assessed by two-dimensional and three-dimensional ultrasonography using the VOCAL method. To our knowledge this is a relative complete report of fetal renal growth chart in china. The normative parameters of fetal kidney could have practical applications in detection and monitoring of renal anomalies in fetal urology. ObjectiveMeasurement of fetal urine production may provide a means of evaluating amniotic fluid volume, which is difficult to measure directly, and predicting fetal hypoxia. Although there have been some reports on fetal urine production, most of those have used two-dimensional ultrasonography to measure bladder volume. Three-dimensional ultrasonography is known to be superior to 2D ultrasonography in organ volume measurements. Thus, we undertook this study to measure bladder volumes using 3D ultrasonography and to establish a normal range for fetal UPR in the Chinese population.Materials and methodsA cross sectional study was performed in 197 normal singleton fetuses with gestational ages ranging from 15 to 38 weeks. The women had no medical or obstetric complications affecting amniotic fluid volume. Fetal bladder volume was measured using 3D ultrasound imaging and VOCAL with a rotational angle of 30 degrees and manual surface tracing technique. Bland and Altman's graphical approach was utilized to investigate the agreement between intra-and inter-observer variability. Bladder volume was measured consecutively three or seven times within a 30-120 second interval and fetal UPR was calculated from serial measurements. UPR (ml/h) was calculated during the filling phase by using the equation UPR= (Vmax-Vmin)×60/time interval. Polynomial regression analysis of UPR as a function of gestational age generated a curve adjusted by the coefficient of determination that represents the normal range for fetal UPR in the Chinese population.ResultsEight of fetuses were excluded because the bladder image quality was insufficient for correct visualization of the bladder contour (n=3), no filling phase (n=3), the consecutive filling bladder volumes less than three (n=2). UPR of 189 fetuses were obtained.Bland and Altman's graphic plots confirm the significant agreement between intra-and inter-observer. Fetal UPR increased with gestational age from a mean value of 1.00 ml/h at 15-16 weeks'gestation to 81.09 ml/h at term, and could be calculated from GA using the formula:UPR=0.0000001.285×GA5.604 (R2=0.848). There were poor correlation between UPR and renal volume.Conclusion Fetal UPR can be easily measured by serial 3D ultrasound assessment of bladder volume. Differences were observed between the values for UPR observed in our sample and the normal values described in previous studies. These differences are mainly related to technological differences. This modality may be a promising alternative to conventional methods of amniotic fluid volume measurement, and might be an alternative option for assessing the function of fetal kidneys. ObjectiveTo produce normograms of Doppler indices including peak systolic velocity (PSV), end diastolic velocity (EDV) and pulsatility index (PI) of umbilical and fetal renal arteries in non-complicated gestations of Chinese population, and thus to identify normal values that can be used routinely. Then to evaluate and. compare how those values vary between umbilical and fetal renal arteries. From analysis of fetal artery hemodynamics, we attempted to reveal placenta and renal functional development in normal fetuses during pregnancy.Materials and methodsThis cross sectional study involved 197 healthy pregnant women who were examined between 15 and 38 weeks of pregnancy. All subjects underwent color Doppler ultrasonography and the Doppler indices of the umbilical and renal arteries were measured for each fetus. We acquire 197 cases of umbilical arteries and 354 cases (n=180 for left kidneys, n=174 for right kidneys) of renal arteries'Doppler indices.For the acquisition of the umbilical and renal arteries Doppler indices, the sample volume has been placed in the free part of the umbilical artery and the center of the renal artery respectively for the evaluation through pulsed Doppler ultrasonography. The measurement of PSV, EDV and PI from three consecutive waves was performed with the automatic mode. In addition, the renal blood flow waveforms were concurrently examined. The Mann-Whitney U test was used to evaluate the concordance between the left and right renal arteries indices. To detect significant differences in the indices'values along gestation, blood flow indices were divided to 6 stages (the first stage is from 15 to 18 weeks of gestation and every 4 weeks thereafter). We have compared values obtained at the different gestational stages, For the determination of statistically significant differences, we used Fishers'protected least significant difference. Finally, we compare these indices between umbilical and fetal renal arteries.Results197 umbilical artery indices and 354 renal artery indices were obtained.1. Hemodynamics of umbilical artery(1) PSV of the umbilical artery increased from 35.66±9.02 cm/sec at 15-18 weeks to 49.57±9.46 cm/sec at 31-34 weeks, then decreased a little. EDV increased from 7.23±3.13 cm/sec at 15-18 weeks to 21.43±7.12 cm/sec at 35-38 weeks. PI decreased from1.49±0.30 at 15-18 weeks to 0.86±0.28 cm/sec at 35-38 weeks.(2) Significant change in the values of PSV, EDV and PI of the umbilical artery has been observed between the 23-30,15-38,15-30 weeks of gestation.2. Hemodynamics of fetal renal artery(1) There were no significant differences between the right and left renal arteries, when the PSV, EDV and PI were compared.(2) PSV and EDV of the left renal artery increased from 20.89±3.02cm/sec and Ocm/sec at 15-18 weeks to 45.72±11.77cm/sec and 7.76±4.34cm/sec at 35-38 weeks, respectively. PI decreased from 2.94±0.34 at 15-18 weeks to 1.96±0.48 at 35-38 weeks.(3) PSV and EDV of the right renal artery increased from 21.26±7.23cm/sec and 0 cm/sec at 15-18 weeks to 49.41±12.47cm/sec and 7.75±3.18cm/sec at 35-38 weeks, respectively. PI decreased from 3.13±0.47 at 15-18 weeks to 2.03±0.28 at 35-38 weeks.(4) At 15-18 weeks of gestation, the blood flow wave forms mainly consisted of type I (only systolic waveforms) and type II (both systolic and diastolic waveforms). Type III waveforms (waveforms that extended beyond the diastolic to the next systolic component) were not recognized. At 19 to 38 week, Type I waveforms were almost disappeared, and the proportion of type II waveforms were decreased, type III increased steadily.(5) Significant change in the values of PSV of the renal artery has been observed between the 15-30 week of gestation. Significant change in the values of EDV and PI has been observed between the 31-38 week of gestation.ConclusionWe have clarified the changes of umbilical and fetal renal hemodynamic indices during the normal course of pregnancy. PSV, EDV of umbilical and renal artery have presented increasing values between 15 and 38 weeks, PI of these arteries has presented decreasing values. The Doppler indices of the umbilical and renal artery in normal fetuses exhibit a different rate. The physiological development of the placenta and kidney cause different considerable variability in PSV, EDV and PI with advancing gestational age. Thus, it was inferred that this finding was related to the development of the placental and renal function.