AGE AND LEAN BODY WEIGHT RELATED GROWTH CURVES OF KIDNEYS USING REAL-TIME 3-DIMENSIONAL ULTRASOUND IN PEDIATRIC UROLOGY

Kidney impairment in fetal growth restriction: three-dimensional evaluation of volume and vascularization

OBJECTIVES

Renal development is impaired in fetal growth restriction (FGR). Renal size can be considered a surrogate of renal function in childhood, and could be impaired in that condition. Our aim was to evaluate the ratio of total renal volume, measured by three-dimensional ultrasound, to estimated fetal weight (TRV/EFW) among fetuses with and without growth restriction. Furthermore, we correlated TRV/EFW with fetal Doppler velocimetry and renal vascularization indexes and evaluated the association of renal volume and vascular parameters with adverse neonatal events in growth-restricted fetuses.

METHODS

In a retrospective cohort, TRV and renal vascularization of growth-restricted and normal fetuses were evaluated by three-dimensional ultrasonography and VOCAL technique. Independent samples t-tests and Mann-Whitney test were used for comparisons between groups. Logistic regression model was applied to evaluate the association between renal characteristics and adverse neonatal events.

RESULTS

Seventy-one growth-restricted fetuses were compared to 194 controls. The TRV/EFW was lower in the growth-restricted group (P < .001). In our sample, this ratio did not correlate with Doppler velocimetry parameters, renal vascular indexes or any adverse neonatal events.

CONCLUSION

The TRV/EFW ratio is decreased in FGR. Further studies are needed to investigate the association of this ratio with long-term renal outcomes.

Renal size and cardiovascular risk in prepubertal children

Renal size is an important parameter for the evaluation and diagnosis of kidney disease and has been associated with several cardiovascular risk factors in patients with kidney failure. These results are however discordant and studies in healthy children are lacking. We aimed to study the association between renal size (length and volume) and cardiovascular risk parameters in healthy children. Clinical, analytical and ultrasound parameters [renal length, renal volume, perirenal fat and carotid intima-media thickness (cIMT)] were determined in 515 healthy prepubertal children (176 lean, 208 overweight and 131 obese). Renal length and volume associated significantly and positively with several anthropometric and cardiovascular risk parameters including cIMT and systolic blood pressure (SBP) (all p < 0.001). Renal length and volume associated with cIMT and SBP in all study subgroups, but these associations were predominant in obese children, in whom these associations were independent after adjusting for age, gender and BSA (all p < 0.05). In multivariate analyses in the study subjects as a whole, renal length was an independent predictor of cIMT (β = 0.310, p < 0.0001) and SBP (β = 0.116, p = 0.03). Renal size associates with cIMT and SBP, independent of other well-established cardiovascular risk factors, and may represent helpful parameters for the early assessment of cardiovascular risk in children.

Ultrasonographic renal volume in Chinese children: Results of 1683 cases

BACKGROUND

At present, little information has been made available in the evaluation of renal volume in pediatric groups of different ages.

PURPOSE

The purposes of the study are to evaluate the relationship between anthropometric measurements and renal volume measured with three-dimensional ultrasonography in Chinese children who have normal kidneys, and to attempt to develop reliable reference values of renal volume to estimate the renal sizes.

METHODS

A total of 1572 Chinese Han children suffering from stomachache, cryptorchidism and neurogenic enuresis with no history of renal disease or pathological abnormalities that might affect measurements, aged 1month to 12years (mean, 5.64years) were examined bilateral kidneys by ultrasonography. The measurements of renal volume were determined using QLAB software in IU22 units (Philips Medical Systems, Holland). Anthropometric indices including sex, age, height and weight were collected for reviewed analysis.

RESULTS

A total of 1683 children were included, and renal volume of 1572 cases (93.4%) was accepted. There was no significant difference between renal volumes of male and female separately in left and right kidneys (P=0.844 and P=0.621, respectively), whereas there was a significant difference between mean left and right renal volumes (P=0.000). Age, height and weight were all significant correlations with renal volume (R(2), 0.885 and 0.913 for the left and right kidneys, respectively, both P=0.000), and age was the strongest correlation with renal volume (r, 0.472 and 0.399 for the left and right kidneys, respectively) among the anthropometric indices. We drew regression equations to estimate renal volume as follows: left renal volume (cm(3))=0.441×age+0.156×height+0.398×weight+6.677 and right renal volume (cm(3))=0.256×age+0.195×height+0.632×weight+1.788, and developed reference values of renal volume separately for the left and right kidneys in different age groups.

CONCLUSIONS

Regression equations have been developed, which define the renal volume from three-dimensional ultrasonography and may assist pediatricians in monitoring renal growth and detecting of unsuspected bilateral increases or decreases in renal size.

A new serum cystatin C formula for estimating glomerular filtration rate in newborns

BACKGROUND

The levels of serum cystatin C (CysC) and creatinine (Cr) were determined in small-for-gestational-age (SGA) babies and compared with those for normal term newborns appropriate for gestational age (AGA), at birth and 3 days later. We then compared a number of cysC-based, Cr-based and combined formulas for estimation of glomerular filtration rate (GFR) with the neonatal reference GFR.

METHODS

Fifty full-term SGA and 50 AGA newborns were enrolled in the study. Kidney volume measurements were performed by ultrasound for each newborn.

RESULTS

At birth, the mean level of CysC in SGA babies was 1.48 ± 0.30 mg/l in cord blood and 1.38 ± 0.18 mg/l in day 3 blood samples, and the mean Cr level, determined simultaneously, was 67.08 ± 17.62 and 55.62 ± 14.91 μmol/l, respectively. These levels did not differ significantly from those determined in AGA babies. A 10 % reduction in kidney volume was associated with an increase in CysC value of 9.3 % in cord blood. The Cr-based and Schwartz-combined equations underestimated GFR relative to CysC-based and Zappitelli-based equations at birth and 3 days later.

CONCLUSIONS

A newly constructed Cys-C based formula which includes kidney volume and body surface area in the calculations for GFR is a reliable marker of GFR compared with neonatal reference clearance values.

Transient renal enlargement in pediatric hematopoietic cell transplant recipients

Age-dependent renal length tables are routinely used when interpreting pediatric ultrasound. Standard renal length tables may not be accurate for HCT patients due to treatment effects on kidney size. The purpose of this study was to determine whether renal size changes from expected lengths based on age after HCT in the absence of other markers of renal disease. Four hundred and fifty renal measurements were made on 101 patients who underwent HCT between 2006 and 2010. Renal length was measured at 1-90 days pre-HCT and at 0-30, 31-90, 91-180, and 181+ days post-HCT. Values were compared with normal renal length tables. Average post-HCT renal lengths were greater than established normative renal length data within every age group. Age-adjusted average renal lengths measured at 0-30 and 31-90 days post-transplantation were significantly larger than pre-HCT renal lengths, with relative increases of 6.9% (4.5, 9.4; p < 0.001) and 3.9% (1.4, 6.4; p = 0.003), respectively. Average renal length did not differ significantly after 90 days post-transplantation. HCT patients may have larger kidneys in the absence of renal disease. Awareness of the potential phenomenon of transient renal enlargement following HCT can prevent misdiagnosis and eliminate unnecessary diagnostic evaluations, interventions, anxiety, resource allocation, and financial costs.

Editorial review: pediatric 3D ultrasound

Three-dimensional ultrasound is an established diagnostic imaging technique in many specialties. However, in neonates, infants and children three-dimensional ultrasound still is underutilized, partially due to time constraints for post-processing and restricted availability, of devices as well as dedicated pediatric transducers. Also reimbursement issues still need to be addressed. This editorial review presents more or less established pediatric three-dimensional ultrasound applications with proven diagnostic benefit as well as potential future applications of three-dimensional/four-dimensional ultrasound in infants and children, aiming at enhancing research and promoting practical use of three-dimensional ultrasound in relevant pediatric conditions. Particularly, applications in neonatal neurosonography, ultrasound of the urogenital tract as well as some other small part and miscellaneous queries are highlighted. Additional other potential and future indications are discussed briefly, also mentioning restrictions and potential future developments. In summary, three-dimensional ultrasound holds some potential to widen sonographic diagnostic capabilities throughout childhood and hopefully will be increasingly investigated and introduced into clinical practice provided respective equipment and pediatric three-dimensional/four-dimensional ultrasound transducers become available.

Assessment of long-term renal complications in extremely low birth weight children

We assessed the long-term renal complications in a regional cohort of extremely low birth weight (ELBW) children born in 2002-2004. The study group, comprising 78 children born as ELBW infants (88% of the available cohort), was evaluated with measurement of serum cystatin C, urinary albumin excretion, renal ultrasound, and 24-h ambulatory blood pressure measurements. The control group included 38 children born full-term selected from one general practice in the district. Study patients were evaluated at a mean age of 6.7 years, and had a median birthweight of 890 g (25th-75th percentile: 760-950 g) and a median gestational age of 27 weeks (25th-75th percentile: 26-29 weeks). Mean serum cystatin C levels were significantly higher (0.64 vs. 0.59 mg/l; p = 0.01) in the ELBW group. Hypertension was diagnosed in 8/78 ELBW and 2/38 of the control children (p = 0.5). Microalbuminuria (>20 mg/g of creatinine) was detected only in five ELBW children (p = 0.17). The mean renal volume was significantly lower in the ELBW group (absolute kidney volume 81 ml vs. 113 ml; p < 0.001, relative kidney volume 85 vs. 97%; p < 0.001). Abnormally small kidneys (<2/3 of predicted size) were detected in 19 ELBW and four control children (p = 0.08). Multivariate logistic regression revealed that the only independent risk factor for renal complications was weight gained during neonatal hospitalization (odds ratio: 0.67; 95% confidence interval: 0.39-0.94). Serum cystatin C and kidney volume are significantly lower in school-age ELBW children. It is important to include systematic renal evaluation in the follow-up programs of ELBW infants.

Predictors of kidney volume change and delayed kidney function recovery after donor nephrectomy

PURPOSE

To our knowledge the effects of preoperative kidney volume in living donors on the post-donation change in size and function of the remaining kidney have not been investigated. We studied the association between preoperative kidney volume, and volume change and delayed kidney function recovery in donors.

MATERIALS AND METHODS

From 2007 to 2008 we investigated 222 living donors. Kidney volume before and 6 months after surgery was estimated using the voxel count method. We analyzed correlations of kidney volume with patient characteristics, kidney function and actual kidney weight. To identify predictors of the volume increase of the remaining kidney and predictors of delayed kidney function recovery we performed regression analysis.

RESULTS

Mean +/- SD total kidney volume was 311.9 +/- 50.6 cc and it correlated with weight, body surface area and kidney function (p <0.001). The mean volume increase in the remaining kidney was 27.6% +/- 9.7% (range 4.5% to 66.1%). Younger age (p <0.001) and lower preoperative volume of the remaining kidney (p = 0.019) were significant predictors of a greater increase in kidney volume on multiple linear regression analysis. Older age (OR 1.07, p <0.001), higher body mass index (OR 1.20, p = 0.008), lower preoperative kidney volume of the remaining kidney (OR 0.98, p = 0.003) and a lower preoperative diethylenetetramine pentaacetic acid glomerular filtration rate in the remaining kidney (OR 0.95, p = 0.017) were significant predictors of delayed kidney function recovery on multiple regression analysis.

CONCLUSIONS

Kidney volume measured by the voxel count method was accurate and correlated with kidney function. Preoperative kidney volume is an independent predictor of the volume increase and delayed kidney function recovery in donors that could be used clinically.

In vitro assessment of a 3D segmentation algorithm based on the belief functions theory in calculating renal volumes by MRI

OBJECTIVE

Renal volumetry is an essential part of split renal function assessment in MR urography. The aim of this study was to assess the accuracy and repeatability of a 3D segmentation algorithm based on the belief functions theory for calculating renal volumes from MR images.

MATERIALS AND METHODS

The true volumes of 20 animal kidneys of various sizes were obtained by fluid displacement. Each kidney was examined using two different MR units. Three-dimensional proton density-weighted acquisitions with an incremental slice thickness were performed. The MR volume was then measured with a segmentation algorithm based on the belief functions theory. Two independent observers performed all segmentations twice. Accuracy, intraobserver variability, and interobserver variability were evaluated by the Bland-Altman method. The number and type of manual corrections were recorded as well as the entire processing time.

RESULTS

The mean renal volume estimated by fluid displacement was 114 mL (range, 38-224 mL). With regard to the renal volumes obtained from assessments of adjacent axial MR images, the maximal SDs of the difference were 2.2 mL (accuracy), 0.6 mL (intraobserver variability), and 1.8 mL (interobserver variability). Segmentation of axial slices provided better accuracy and reproducibility than coronal slices. Overlapped coronal slices yielded poor results because of the partial volume effect. The mean processing time including optional manual modifications was less than 75 seconds.

CONCLUSION

The belief functions theory can be considered an accurate and reproducible mathematic method to assess renal volume from MR adjacent images.

Reproducibility of fetal renal pelvis volume measurement using three-dimensional ultrasound

OBJECTIVE

To assess the reproducibility of fetal renal pelvis volume measurement in hydronephrotic kidneys using transabdominal three-dimensional (3D) ultrasound.

METHODS

The fetal renal pelvis volume was measured using 3D ultrasound in one kidney in each of 15 fetuses with hydronephrosis in the second or third trimester of pregnancy. Hydronephrosis was diagnosed when the fetus had an anteroposterior renal pelvis diameter > or = 5 mm. After volume acquisition by one of the observers, the repeatability of volume calculation with manual delineation of the fetal renal pelvis was assessed by six different observers using the Virtual Organ Computer-aided AnaLysis (VOCAL(trade mark)) imaging program. The intraclass correlation coefficients (ICC), coefficient of variation (CV) and within- and between-observer repeatability coefficient (r) were calculated and Bland-Altman plots were constructed.

RESULTS

Both intra- and interobserver reliability of the fetal renal pelvis volume measurements were considered to be very good. For intraobserver reliability, the ICC was 0.996 and the CV was 10.8%. For the overall interobserver reliability, the ICC was 0.998 and the CV was 15.7%; the interobserver reliability between pairs of observers had ICCs between 0.994 and 0.999, and CVs between 19.5% and 7.6% for inexperienced and experienced observers, respectively.

CONCLUSION

With 3D ultrasound using the VOCAL imaging program, it is technically feasible to reproduce fetal renal pelvis volume measurements. Further research to establish the clinical applications of this technology is warranted.

Nomogram of fetal renal growth expressed in length and parenchymal area derived from ultrasound images

PURPOSE

We constructed nomograms of fetal renal length and parenchymal area derived from ultrasound images to develop a standard for normal fetal renal growth.

MATERIALS AND METHODS

Longitudinal and transverse ultrasound renal images from 216 normal fetuses (16 to 41 weeks of gestation) were evaluated to construct growth charts. We measured the parenchymal area as well as the longitudinal and transverse lengths of each kidney using computer software for image analysis. Data were separately plotted as a mean +/- 2 SD determined by polynomial regression analysis.

RESULTS

Nomograms for a renal growth chart were constructed independently for the right and left fetal kidneys. No statistically significant difference was noted between the right and left renal measurements. The polynomial regression equations for the left renal longitudinal length and parenchymal area, respectively, were y = -0.0002x(3) + 0.0139x(2) - 0.2162 x 2.3929 (r(2) = 0.9842), and y = -0.0009x(3) + 0.0724x(2) - 1.5643 x 11.68 (r(2) = 0.9779). The longitudinal and transverse fetal renal growth curves displayed significant growth associated with gestational age (p <0.001). Our data on left longitudinal renal length exhibited an intermediate level compared to 2 published Western growth charts. However, statistical comparisons revealed the differences were partially, but not universally, significant.

CONCLUSIONS

We present our nomogram of fetal renal growth expressed in length and parenchymal area. To our knowledge this is the first report of a fetal renal growth chart in Asia that includes the parenchymal area. This nomogram may serve as a valuable tool for evaluation of fetal renal growth.

Nomograms of total renal volume, urinary bladder volume and bladder wall thickness index in 3,376 children with a normal urinary tract

BACKGROUND

We have previously shown that urinary bladder volume index (BVI = length x width x depth of bladder) and bladder volume wall thickness index (BVWI = BVI at full bladder/average bladder wall thickness) are useful indicators of bladder dysfunction in children with enuresis and urinary tract infection. These indices show a good correlation with urodynamic studies. We have expanded the study to include normal paediatric subjects with a wide age range. We illustrate a simple sonography protocol with nomograms of different parameters, which provide useful references for functional assessment in children with urological abnormalities.

OBJECTIVE

To construct nomograms of total renal volume, maximum BVI and BVWI based on a Chinese paediatric population with age range from newborn to adolescence.

MATERIALS AND METHODS

Sonography was performed in consecutive children with normal urinary tracts on imaging, using a standardized protocol. Data were collected for construction of nomograms for different parameters.

RESULTS

Nomograms of total renal volume, BVI and BVWI were constructed based on 3,376 consecutive paediatric subjects. All parameters consistently increased with age.

CONCLUSION

Nomograms of total renal volume, BVI and BVWI could provide useful references for studying bladder dysfunction in children using noninvasive dynamic sonography.

Impaired kidney growth in low-birth-weight children: Distinct effects of maturity and weight for gestational age

BACKGROUND

Chronic kidney disease (CKD) alters the regulation of calcium and phosphate homeostasis, leading to secondary hyperparathyroidism, metabolic bone disease, soft tissue calcifications, and other metabolic derangements that have a significant impact on morbidity and mortality. The parathyroid gland is the central organ responsible for regulating these adaptive responses. Suppression of parathyroid hormone (PTH) secretion, hypertrophy, and hyperplasia are a major goal of treatment of CKD.

METHODS

Current literature was reviewed and combined with the author's experience to address a number of issues regarding the optimal treatment of secondary hyperparathyroidism in hemodialysis patients.

RESULTS

The calcium sensing receptor (CASR) is the most important factor regulating parathyroid gland function, and allosteric modulators of CASR, called calcimimetics, provide a novel drug therapy to suppress PTH secretion. The current use of active vitamin D analogues to suppress PTH is often limited by hypercalcemia and hyperphosphatemia. Clinical trials of cinacalcet HCl, the first calcimimetic to be approved for treatment of secondary hyperparathyroidism in CKD, have demonstrated suppression of circulating PTH levels without increments in the calcium-phosphorus (Ca x P) product, making it easier to achieve the stringent management guidelines proposed for subjects with CKD by the National Kidney Foundation Kidney Disease Outcomes Quality Initiative (K/DOQI).

CONCLUSION

The management of disordered calcium and phosphate homeostasis in CKD patients is evolving based on our knowledge of the major importance of the calcium sensing receptor (CASR) in controlling parathyroid gland function and the potent actions of calcimimetics to target CASR. The purpose of this presentation is to provide an overview of the role of the CASR in regulation of parathyroid gland function, to examine the mechanisms whereby calcimimetics target the CASR, and to review the clinical trials that support the use of cinacalcet HCl for the treatment of secondary hyperparathyroidism in stage 5 chronic kidney disease (CKD).