Kidney growth curves in healthy children from the third trimester of pregnancy until the age of two years. The Generation R Study

The NICHD Fetal 3D Study: A Pregnancy Cohort Study of Fetal Body Composition and Volumes

There's a paucity of robust normal fractional limb and organ volume standards from a large and diverse ethnic population. The Fetal 3D Study was designed to develop research and clinical applications for fetal soft tissue and organ volume assessment. The NICHD Fetal Growth Studies (2009-2013) collected 2D and 3D fetal volumes. In the Fetal 3D Study (2015-2019), sonographers performed longitudinal 2D and 3D measurements for specific fetal anatomical structures in research ultrasounds of singletons and dichorionic twins. The primary aim was to establish standards for fetal body composition and organ volumes, overall and by maternal race/ethnicity, and determine whether these standards vary for twins versus singletons. We describe the study design, methods, and details about reviewer training. Basic characteristics of this cohort, with their corresponding distributions of fetal 3D measurements by anatomical structure, are summarized. This investigation is responsive to critical data gaps in understanding serial changes in fetal subcutaneous fat, lean body mass, and organ volume in association with pregnancy complications. In the future, this cohort can answer critical questions regarding the potential influence of maternal characteristics, lifestyle factors, nutrition, and biomarker and chemical data on longitudinal measures of fetal subcutaneous fat, lean body mass, and organ volumes.

Pediatric kidney dimensions and risk of persistent albuminuria in Mexican adolescents

In Mexico, chronic kidney disease of unknown origin is highly prevalent. Screening studies in adolescents have shown persistent microalbuminuria (pACR), adaptive podocytopathy and decreased kidney volume (KV). Here, we sought to develop normality tables of kidney dimensions by ultrasound in the Mexican state of Aguascalientes pediatric population (0 to 18y) and evaluate the relationship between the KV and pACR among the region's adolescents in a cross-sectional study. Kidney length (KL) and KV were determined by ultrasound. Our findings were compared with those in international literature of different populations where tables and graphs of normal kidney dimensions by ultrasound were reported. We compared organ dimensions in individuals above the age of 11 without albuminuria with those in patients with pACR recruited through screening studies in adolescents in Aguascalientes. This included 1068 individuals to construct percentile tables and graphs of the KL. Kidney dimensions were significantly lower when compared with all international comparisons. From a total 14,805 screen individuals, we compared 218 adolescents with pACR and 377 individuals without significant albuminuria. The Total KV adjusted to body surface (TKVBS) was significantly associated with pACR (odds ratio 1.03, 95% confidence interval 1.02-1.03). The upper quartile of TKVBS was highly associated with pACR (7.57, 4.13-13.87), hypertension (2.53, 1.66-3.86), and hyperfiltration (26 vs 11.5%). Thus, TKVBS is directly associated with pACR while greater KV, arterial hypertension, and hyperfiltration in patients with pACR suggest that the increase in volume is secondary to kidney hypertrophy. Additionally, the adaptative podocytopathy with low fibrosis seen on kidney biopsy which was performed in a subset of patients, and the smaller kidney dimensions in our population point to prenatal oligonephronia as the primary cause of the detected kidney disease.

Sexual Dimorphism of Corticosteroid Signaling during Kidney Development

Sexual dimorphism involves differences between biological sexes that go beyond sexual characteristics. In mammals, differences between sexes have been demonstrated regarding various biological processes, including blood pressure and predisposition to develop hypertension early in adulthood, which may rely on early events during development and in the neonatal period. Recent studies suggest that corticosteroid signaling pathways (comprising glucocorticoid and mineralocorticoid signaling pathways) have distinct tissue-specific expression and regulation during this specific temporal window in a sex-dependent manner, most notably in the kidney. This review outlines the evidence for a gender differential expression and activation of renal corticosteroid signaling pathways in the mammalian fetus and neonate, from mouse to human, that may favor mineralocorticoid signaling in females and glucocorticoid signaling in males. Determining the effects of such differences may shed light on short term and long term pathophysiological consequences, markedly for males.

The old becomes new: advances in imaging techniques to assess nephron mass in children

Renal imaging is widely used in the assessment of surrogate markers of nephron mass correlated to renal function. Autopsy studies have tested the validity of various imaging modalities in accurately estimating "true" nephron mass. However, in vivo assessment of nephron mass has been largely limited to kidney volume determination by ultrasonography (US) in pediatric populations. Practical limitations and risks create challenges in incorporating more precise 3D volumetric imaging, like magnetic resonance imaging (MRI), and computed tomography (CT) technologies, compared to US for routine kidney volume assessment in children. Additionally, accounting for structural anomalies such as hydronephrosis when estimating renal parenchymal area in congenital anomalies of the kidney and urinary tract (CAKUT) is important, as it correlates with chronic kidney disease (CKD) progression. 3D imaging using CT and MRI has been shown to be superior to US, which has traditionally relied on 2D measurements to estimate kidney volume using the ellipsoid calculation. Recent innovations using 3D and contrast-enhanced US (CEUS) provide improved accuracy with low risk. Indexing kidney volume to body surface area in children is an important standard that may allow early detection of CKD progression in high-risk populations. This review highlights current understanding of various imaging modalities in assessing nephron mass, discusses applications and limitations, and describes recent advances in the field of imaging and kidney disease. Although renal imaging has been a long-standing, essential tool in assessing kidney disease, innovation and new applications of established technologies provide important tools in the study and management of kidney disease in children.

Renal Hypoplasia, From Grossly Insufficient to Not Quite Enough: Consideration for Expanded Concepts Based Upon the Author's Perspective With Historical Review

Hypoplasia is defined in the Merriman-Webster dictionary as "a condition of arrested development in which an organ, or part, remains below the normal size, or in an immature state." The degree of reduced size is not definitional. Renal hypoplasia, however, has historically been defined as a more marked reduction in renal mass such that presentation in childhood is the norm. There are 3 commonly recognized types of renal hypoplasia, simple hypoplasia, oligomeganephronic hypoplasia (oligomeganephronia) and segmental hypoplasia (Ask-Upmark kidney). They have in common a reduction in the number of renal lobes. A fourth type, not widely recognized, is cortical hypoplasia where nephrogenesis is normal but there is a reduction in the number of nephron generations. Recently there has been great interest in milder degrees of reduced nephron mass, known as oligonephronia because of its association with risk of adult-onset hypertension and chronic kidney disease. Since the last pathology review of this topic was published by Jay Bernstein in 1968, an update of the renal pathology findings in renal hypoplasia is provided with a review of 18 new cases. The renal hypoplasias are then framed within the modern concept of oligonephronia, its diverse causes and prognostic implications.

Fetal Physiologically Based Pharmacokinetic Models: Systems Information on the Growth and Composition of Fetal Organs

BACKGROUND

The growth of fetal organs is a dynamic process involving considerable changes in the anatomical and physiological parameters that can alter fetal exposure to xenobiotics in utero. Physiologically based pharmacokinetic models can be used to predict the fetal exposure as time-varying parameters can easily be incorporated.

OBJECTIVE

The objective of this study was to collate, analyse and integrate the available time-varying parameters needed for the physiologically based pharmacokinetic modelling of xenobiotic kinetics in a fetal population.

METHODS

We performed a comprehensive literature search on the physiological development of fetal organs. Data were carefully assessed, integrated and a meta-analysis was performed to establish growth trends with fetal age and weight. Algorithms and models were generated to describe the growth of these parameter values as functions of age and/or weight.

RESULTS

Fetal physiologically based pharmacokinetic parameters, including the size of the heart, liver, brain, kidneys, lungs, spleen, muscles, pancreas, skin, bones, adrenal and thyroid glands, thymus, gut and gonads were quantified as a function of fetal age and weight. Variability around the means of these parameters at different fetal ages was also reported. The growth of the investigated parameters was not consistent (with respect to direction and monotonicity).

CONCLUSION

Despite the limitations identified in the availability of some values, the data presented in this article provide a unique resource for age-dependent organ size and composition parameters needed for fetal physiologically based pharmacokinetic modelling. This will facilitate the application of physiologically based pharmacokinetic models during drug development and in the risk assessment of environmental chemicals and following maternally administered drugs or unintended exposure to environmental toxicants in this population.

Reference ranges for ultrasound measurements of fetal kidneys in a cohort of low-risk pregnant women

PURPOSE

Alterations in renal dimensions may be an early manifestation of deviation from normality, with possible repercussions beyond intrauterine life. The objective of this study was to establish reference curves for fetal kidney dimensions and volume from 14 to 40 weeks of gestation.

METHODS

This is a prospective longitudinal study of 115 Brazilian participants in the "WHO multicentre study for the development of growth standards from fetal life to childhood: the fetal component". Pregnant women with clinical and sociodemographic characteristics allowing the full potential fetal growth were followed up from the first trimester until delivery. These women underwent serial sonographic evaluation of fetal kidneys. The longitudinal, anteroposterior and transverse diameters of both fetal kidneys were measured, in addition to calculation of kidney volume. By quantile regression analysis, reference curves of renal measurements related to gestational age were built.

RESULTS

Standard normal sonographic values of renal biometry were defined during pregnancy. Reference values for the 10th, 50th and 90th centiles of different fetal kidney measurements (longitudinal, anteroposterior, transverse and volume) from the 14th to the 40th week of gestation were fitted.

CONCLUSION

The reference curves presented should be of the utmost importance for screening and diagnosis of alterations in renal development during the intrauterine period.

Evaluation of fetal kidney growth using ultrasound: A systematic review

PURPOSE

To determine the role of ultrasound imaging in evaluating fetal kidney growth.

METHODS

MEDLINE, CINAHL and EMBASE databases were electronically searched for studies between 1996 and January 2017 and limited to English language. Studies were included if they reported on an ultrasound technique to assess fetal kidney growth and they were not a case report or case series. There was independent selection of studies by two reviewers in consensus with one other reviewer. Data were extracted by one reviewer in consensus with two other reviewers.

RESULTS

A total of 1785 articles were identified. The full text of 39 of these were assessed for eligibility for inclusion. Twenty-eight studies were then included in the review. Standard two dimensional (2D) fetal renal measurements are easy to perform, however, this review identified that most studies had some methodological limitations. The disadvantage with 2D and three dimensional (3D) fetal renal volumes are that they include the entire kidney and good reproducibility of 3D volumes has not yet been demonstrated. Currently there is limited research on fetal kidney growth in the setting of abnormal fetal growth. Research focussing directly on fetal kidney parenchyma and blood flow is scarce.

CONCLUSIONS

Some nomograms of 2D and 3D fetal kidney size and volume have been developed. Kidney length is the most popular single fetal kidney measurement; however, it does not seem to be a good indicator of growth. In IUGR fetuses, kidney length remained similar to appropriately grown fetuses whereas AP and TS dimensions were significantly decreased. New ultrasound techniques focusing on the parenchyma of the kidney and perfusion to the kidney should be explored as they may provide more meaningful information on kidney development in the fetus and future kidney function.

Maternal and Fetal Folate, Vitamin B12, and Homocysteine Concentrations and Childhood Kidney Outcomes

Background

Folate, vitamin B₁₂ and homocysteine concentrations during pregnancy are important factors for early development and may persistently influence kidney function in the offspring. We examined the associations of folate, vitamin B₁₂, and homocysteine concentrations during pregnancy with kidney outcomes in school-aged children.

Study design

Population-based prospective cohort study from fetal life onwards.

Settings & participants

This study was performed among 4,226 pregnant women and their children.

Predictors

Folate, vitamin B₁₂ and homocysteine blood concentrations measured in early pregnancy (median gestational age 13.2 weeks (25th to 75th percentiles 12.2, 14.8) and at birth (cord blood).

Outcomes & measurements

At the median age of 6.0 years (25th to 75th percentiles 5.9, 6.3) we measured combined kidney volume with ultrasound, estimated glomerular filtration rate based on creatinine (eGFR_creat) and cystatin C (eGFR_cystC) concentrations and microalbuminuria.

Results

We observed that higher maternal folate concentrations were associated with larger childhood combined kidney volume, whereas higher maternal vitamin B₁₂ concentrations were associated with higher childhood eGFR_cystC (p-values <0.05). These associations were independent of homocysteine concentrations. Higher maternal homocysteine concentrations were associated with smaller combined kidney volume and lower childhood eGFR_cystC (p-values <0.05). The association of maternal homocysteine concentrations with childhood eGFR_cystC was largely explained by combined kidney volume. Higher cord blood homocysteine concentrations were associated with larger combined kidney volume and lower eGFR_cystC (p-values <0.05). Folate, vitamin B₁₂ or homocysteine concentrations were not associated microalbuminuria.

Limitations

Observational study, so causality cannot be established.

Conclusion

Our findings suggest that folate, vitamin B₁₂ and homocysteine concentrations during fetal life are associated with offspring kidney development. However, the effect sizes are small. Further studies are needed to replicate these findings and assess the causality and consequences for kidney health in later life.

Fetal first trimester growth is not associated with kidney outcomes in childhood

BACKGROUND

Impaired fetal growth is associated with increased risks of kidney diseases in later life. Because human development rates are highest during the first trimester, this trimester may be a particularly critical period for kidney outcomes. We have therefore examined the association of fetal first trimester growth with kidney outcomes in childhood.

METHODS

This study was embedded in a prospective population-based cohort study among 1176 pregnant women and their children. We used fetal first trimester crown-length as the growth measure among mothers with a regular menstrual cycle and a known first day of the last menstrual period. At the childhood age of 6 (median 5.7-6.8) years, we measured combined kidney volume, microalbuminuria and estimated glomerular filtration rate (eGFR) based on serum creatinine and cystatin C concentrations.

RESULTS

No consistent associations of fetal first trimester crown-rump length with childhood combined kidney volume, eGFR and microalbuminuria were observed. Compared to children with a fetal first trimester crown-rump length in the highest quintile, those in the lowest quintile had a larger childhood combined kidney volume (difference 5.32 cm³, 95 % confidence interval 1.06 to 9.57), but no differences in kidney function.

CONCLUSION

Our results do not support the hypothesis that fetal first trimester growth restriction affects kidney size and function in childhood. Further studies are needed to focus on critical periods in early life for kidney function and disease in later life.

Are low birth weight neonates at risk for suboptimal renal growth and function during infancy?

Background

To assess the renal growth and function of neonates during infancy in relation to birth weight and gestational age.

Methods

A longitudinal study was conducted at a tertiary hospital in South India from June 2010 to August 2014. Low birth weight neonates (LBW) were further sub-classified based on gestational age and compared with normal birth weight (NBW) full term neonates at birth, 6 months and 18-24months of age. The renal volume was measured by ultrasound and renal function by Cystatin C- derived glomerular filtration rate (CysGFR) at the three time points during the dynamic phase of renal maturation in infancy.

Results

We recruited 100 LBW and 66 NBW term neonates. Thirty five percent of the LBW neonates were SGA. Among the AGA neonates, 39 % were LBW neonates. The mean height and weight of the LBW neonates were significantly lower compared to NBW neonates throughout infancy. The increment in kidney volume was in accordance with the change in body size, being lower in LBW compared to NBW infants. The combined kidney volume was significantly lower in LBW and SGA neonates across all three time points (p < 0.001). CysGFR in the LBW and SGA infants, despite having low kidney volumes, were comparable to the GFRs of NBW and AGA neonates at the end of infancy.

Conclusion

This study highlights the fact that both birth weight and gestational age influence kidney growth and function in infancy. At the end of infancy, despite a significant difference in kidney volumes and age at last follow up, the glomerular filtration rate was comparable between LBW and NBW infants. Though not statistically significant, there was a trend towards higher urine microalbumin in LBW compared to NBW in infancy.

Electronic supplementary material

The online version of this article (doi:10.1186/s12882-016-0314-7) contains supplementary material, which is available to authorized users.

Influence of common genetic variants on childhood kidney outcomes

BACKGROUND

Kidney measures in early life are associated with kidney disease in later life. We hypothesized that these associations are partly explained by common genetic variants that lead to both smaller kidneys with lower kidney function in early childhood and kidney disease in adulthood.

METHODS

We examined in a population-based prospective cohort study among 4,119 children the associations of a weighted genetic risk score combining 20 previously identified common genetic variants related to adult eGFRcreat with kidney outcomes in children aged 6.0 years (95% range 5.7-7.8). Childhood kidney outcomes included combined kidney volume, glomerular filtration rate (eGFR) based on creatinine levels, and microalbuminuria based on albumin and creatinine urine levels.

RESULTS

We observed that the genetic risk score based on variants related to impaired kidney function in adults was associated with a smaller combined kidney volume (P value 3.0 × 10(-3)) and with a lower eGFR (P value 4.0 × 10(-4)) in children. The genetic risk score was not associated with microalbuminuria.

CONCLUSION

Common genetic variants related to impaired kidney function in adults already lead to subclinical changes in childhood kidney outcomes. The well-known associations of kidney measures in early life with kidney disease in later life may at least be partly explained by common genetic variants.

Vitamin D status during fetal life and childhood kidney outcomes

BACKGROUND/OBJECTIVES

Maternal vitamin D deficiency during pregnancy may influence offspring kidney health. We aimed to examine the associations of 25-hydroxyvitamin D (25(OH)D) blood levels during fetal life with kidney outcomes at school age.

SUBJECTS/METHODS

This study was embedded in a population-based prospective cohort study among 4212 mother-child pairs. We measured maternal second trimester (18-25 weeks) and fetal cord blood (at birth) 25(OH)D levels. At a median age of 6.0 years, we measured children's combined kidney volume, glomerular filtration rate (eGFR) from creatinine and cystatin C serum levels, and microalbuminuria from albumin and creatinine urine levels.

RESULTS

Of all mothers, 21.9% had severely deficient levels (25(OH)D <25.0 nmol/l), 25.7% had deficient levels (25.0-49.9 nmol/l), 25% had sufficient levels (50.0-74.9 nmol/l) and 27.4% had optimal levels (⩾75.0 nmol/l). Maternal 25(OH)D levels were not consistently associated with childhood combined kidney volume. Higher maternal 25(OH)D levels were associated with lower childhood eGFR (difference -0.94 ml/min per 1.73 m(2) (95% confidence interval, -1.73; -0.15) per 1 standard deviation (s.d.) increase in 25(OH)D). Maternal 25(OH)D levels were not associated with microalbuminuria. Cord blood 25(OH)D levels were not associated with childhood kidney outcomes. The associations of maternal 25(OH)D levels with childhood eGFR were partly explained by childhood vitamin D status.

CONCLUSIONS

Our findings suggest that maternal 25(OH)D levels during pregnancy may influence childhood kidney outcomes. These results should be considered hypothesis generating. Further studies are needed to replicate the observations, to examine the underlying mechanisms and to identify the long-term clinical consequences.

First-trimester maternal protein intake and childhood kidney outcomes: the Generation R Study

BACKGROUND

Nutritional exposures during in utero development may have long-lasting consequences for postnatal renal health. Animal studies suggest that specifically maternal dietary protein intake during pregnancy influences childhood kidney function.

OBJECTIVE

We examined the associations of total, animal, and vegetable maternal protein intake during pregnancy with kidney volume and function in school-aged children.

DESIGN

This study was conducted in 3650 pregnant women and their children who were participating in a population-based cohort study from early life onward. First-trimester energy-adjusted maternal protein intake was assessed with a food-frequency questionnaire. At the child's age of 6 y, we assessed kidney volume, estimated glomerular filtration rate (eGFR) using serum creatinine and cystatin C concentrations, and microalbuminuria using urine albumin:creatinine ratios.

RESULTS

First-trimester maternal total protein intake was associated with a higher childhood creatinine-based eGFR (difference: 0.06 mL × min(-1) × 1.73 m(-2); 95% CI: 0.01, 0.12 mL · min(-1) · 1.73 m(-2) per gram of protein intake). This association was mainly driven by vegetable protein intake (0.22 mL × min(-1) × 1.73 m(-2); 95% CI: 0.10, 0.35 mL · min(-1) · 1.73 m(-2) per gram of vegetable protein intake). These associations were not explained by protein intake in early childhood. First-trimester maternal protein intake was not significantly associated with childhood kidney volume, cystatin C-based eGFR, or the risk of microalbuminuria.

CONCLUSIONS

Our findings suggest that higher total and vegetable, but not animal, maternal protein intake during the first trimester of pregnancy is associated with a higher eGFR in childhood. Further follow-up studies are needed to investigate whether maternal protein intake in early pregnancy also affects the risk of kidney diseases in later life.

Infant Breastfeeding and Kidney Function in School-Aged Children

BACKGROUND

Early life factors may influence kidney growth and function throughout the life course. We examined the associations of breastfeeding duration and exclusivity and age at introduction of solid foods with kidney outcomes at school age.

STUDY DESIGN

Prospective cohort study from fetal life onward.

SETTING & PARTICIPANTS

5,043 children in the Netherlands.

PREDICTORS

Infant feeding was assessed prospectively using questionnaires.

OUTCOMES & MEASUREMENTS

In children at a median age of 6.0 years, we measured kidney volume with ultrasound, estimated glomerular filtration rate (eGFR) from serum creatinine level, and microalbuminuria from urinary albumin and creatinine levels.

RESULTS

92% of all children were ever breastfed, of whom 27% were breastfed for more than 6 months and 21% were breastfed exclusively for at least 4 months. Compared with ever-breastfed children, never-breastfed children had smaller combined kidney volumes (-2.69 [95% CI, -4.83 to -0.56] cm(3)) and lower eGFRs (-2.42 [95% CI, -4.56 to -0.28] mL/min/1.73 m(2)) at school age. Among breastfed children, shorter duration of breastfeeding was associated with smaller combined kidney volume and lower microalbuminuria risk (P<0.05). Compared to exclusive breastfeeding for 4 months, nonexclusive breastfeeding in the first 4 months was associated with smaller combined kidney volume and lower eGFR (both P<0.05). Associations with eGFR were explained largely by kidney volume. Age at introduction of solid foods was not associated with any kidney outcome.

LIMITATIONS

Observational study, so causality cannot be established. Follow-up measurements were available for 76% of children.

CONCLUSIONS

These results suggest that breastfeeding is associated with subclinical changes in kidney outcomes in childhood. Further studies are needed to explore whether early life nutrition also affects the risk of kidney disease in adulthood.

Fetal Smoke Exposure and Kidney Outcomes in School-Aged Children

BACKGROUND

Fetal smoke exposure may result in developmental adaptations that permanently affect the developing kidney. In this study, the associations of maternal and paternal smoking during pregnancy with childhood kidney size and function were assessed.

STUDY DESIGN

Prospective cohort study from fetal life onward.

SETTING & PARTICIPANTS

This study was conducted in a group of 5,622 children in Rotterdam, the Netherlands.

PREDICTORS

Maternal and paternal smoking were assessed during pregnancy by questionnaires.

OUTCOMES & MEASUREMENTS

At a median age of 6.0 (5th-95th percentile, 5.6-7.9) years, we measured childhood kidney volumes, estimated glomerular filtration rate (eGFR), and albumin-creatinine ratio.

RESULTS

The confounder model, which included size at birth, shows that compared with children from mothers who did not smoke during pregnancy, those from mothers who continued smoking during pregnancy had smaller combined kidney volumes at the age of 6 years. The strongest effect estimate was observed for mothers who smoked 5 or more cigarettes per day during pregnancy (difference for combined kidney volume, -2.80 [95% CI, -5.15 to -0.45] cm(3)). Similarly, continued maternal smoking during pregnancy also was associated with a lower eGFR in childhood (difference, -2.25 [95% CI, -3.70 to -0.79] mL/min/1.73 m(2)). First-trimester-only smoking was associated with a higher risk of increased albumin-creatinine ratio (OR, 1.45; 95% CI, 1.05-2.01). Among mothers who did not smoke during pregnancy, paternal smoking was associated with smaller childhood combined kidney volume (difference, -1.78 [95% CI, -3.48 to -0.07] cm(3)), but not with childhood kidney function measures.

LIMITATIONS

Smoking behavior was measured with questionnaires. Follow-up measurements were available for only 70% of the children.

CONCLUSIONS

Continued maternal smoking during pregnancy is associated with smaller combined kidney volume and lower eGFR in school-aged children. Stronger effect estimates for maternal versus paternal smoking suggest that intrauterine adaptive responses may play a role as underlying mechanisms.

Protein intake in infancy and kidney size and function at the age of 6 years: The Generation R Study

BACKGROUND

High protein intake has been linked to kidney growth and function. Whether protein intake is related to kidney outcomes in healthy children is unclear.

METHODS

We examined the associations between protein intake in infancy and kidney outcomes at age 6 years in 2968 children participating in a population-based cohort study. Protein intake at 1 year was assessed using a food-frequency questionnaire and was adjusted for energy intake. At age 6 years we measured the kidney volume and urinary albumin/creatinine ratio (ACR) of all participating children, and we estimated glomerular filtration rate (eGFR) using serum creatinine and cystatin C levels.

RESULTS

In models adjusted for age, sex, body surface area, and sociodemographic factors, a higher protein intake was associated with a lower ACR and a higher eGFR but was not consistently associated with kidney volume. However, after further adjustment for additional dietary and lifestyle factors, such as sodium intake, diet quality, and television watching, higher protein intake was no longer associated with kidney function. No differences in associations were observed between animal and vegetable protein intake.

CONCLUSIONS

Our findings show that protein intake in early childhood is not independently associated with kidney size or function at the age of 6 years. Further study is needed on other early life predictors of kidney size and function in later life.

Kidney size and function in a multi-ethnic population-based cohort of school-age children

BACKGROUND

Subclinical impaired kidney growth and function in childhood may lead to kidney diseases and high blood pressure in adulthood. We assessed the cross-sectional associations of childhood characteristics with kidney size and function in a multi-ethnic cohort.

METHODS

This study was embedded in a population-based cohort study of 6,397 children with a median age of 6.0 years.Kidney volume, creatinine and cystatin C blood levels, microalbuminuria and blood pressure were measured, and glomerular filtration rate (GFR) was estimated.

RESULTS

Childhood anthropometrics were positively associated with kidney volume, creatinine level and blood pressure (all p < 0.05). We observed ethnic differences in all kidney size and function measures (all p < 0.05). Children with smaller kidneys had higher creatinine and cystatin C blood levels, leading to a lower estimated GFR [difference 5.68 ml/min/1.73 m2 (95% confidence interval 5.14-6.12) per 1 standard deviation increase in kidney volume]. Larger kidney volume was associated with an increased risk of microalbuminuria.

CONCLUSIONS

Childhood kidney volume and function are influenced by body mass index and ethnicity. Kidney volume is related with kidney function but not with blood pressure. These results may help to identify individuals at risk for kidney disease in an early stage.

Childhood kidney outcomes in relation to fetal blood flow and kidney size

Impaired fetal abdominal blood flow may lead to smaller kidneys and subsequent impaired kidney function in later life. In a prospective cohort study among 923 pregnant women and their children, we measured fetal growth, kidney volumes, and umbilical and cerebral artery blood flow (median gestational age of 30.3 weeks; 95% range, 28.5-32.7 weeks). We used a higher umbilical/cerebral artery pulsatility index ratio as an indicator of preferential fetal blood flow to the upper body parts at the expense of the intra-abdominal organs. At a median age of 5.9 years (95% range, 5.7-6.6 years), we measured childhood kidney volumes, creatinine and cystatin C blood levels, microalbuminuria, BP, and eGFR. A preferential fetal blood flow to the upper body parts at the expense of the intra-abdominal organs associated only with a smaller combined kidney volume in childhood. Fetal combined kidney volume positively associated with childhood combined kidney volume and eGFR, and inversely associated with childhood creatinine and cystatin C levels (all P values <0.05), but did not associate with childhood microalbuminuria and BP. Children within the highest tertile of fetal umbilical/cerebral ratio and the lowest tertile of fetal combined kidney volume had the lowest eGFR (difference, -6.36 ml/min per 1.73 m(2); 95% confidence interval, -11.78 to -0.94 compared with children within the middle tertiles). These data suggest that impaired fetal blood to the abdominal organs and smaller fetal kidney size are associated with subclinical changes in kidney outcomes in school-aged children.

Fetal and infant growth patterns and kidney function at school age

Low birth weight is associated with ESRD. To identify specific growth patterns in early life that may be related to kidney function in later life, we examined the associations of longitudinally measured fetal and infant growth with kidney function in school-aged children. This study was embedded in a population-based prospective cohort study among 6482 children followed from fetal life onward. Fetal and childhood growth was measured during second and third trimesters of pregnancy, at birth, and at 6, 12, 24, 36, and 48 months postnatally. At the age of 6 years, we measured kidney volume by ultrasound. GFR was estimated using blood creatinine levels. Higher gestational age-adjusted birth weight was associated with higher combined kidney volume and higher eGFR (per 1 SD score increase in birth weight; 1.27 cm(3) [95% confidence interval, 0.61 to 1.93] and 0.78 ml/min per 1.73 m2 [95% CI, 0.16 to 1.39], respectively). Fetal weight, birth weight, and weight at 6 months were positively associated with childhood kidney volume, whereas higher second trimester fetal weight was positively associated with higher GFR (all P values<0.05). Fetal and childhood lengths were not consistently associated with kidney function. In this cohort, lower fetal and early infant weight growth is associated with smaller kidney volume in childhood, whereas only lower fetal weight growth is associated with lower kidney function in childhood, independent of childhood growth. Whether these associations lead to an increased risk of kidney disease needs to be studied further.

Kidney grafts from donors ≤ 5 yr of age: single kidney transplantation for pediatric recipients or en bloc transplantation for adults?

Kidneys from donors ≤5 yr of age represent a controversial issue. The purpose of this study was to compare the transplant outcomes as single and single/en bloc grafts into pediatric and adult KT recipients, respectively. All recipients of kidneys from donors ≤5 yr old transplanted at our institution from 3/2003 to 12/2010 were evaluated, and corresponding data were analyzed. There were 11 pediatric and 14 adult recipients. Median donor age and body weight were 38 months and 14 kg, respectively. PNF, n = 2 and DGF, n = 1 were observed only among adult recipients. Five-yr graft survival was 100% for children and 86% for adults. There were no significant differences in graft and patient survival, PNF, DGF, acute rejection, or postoperative complications among children/single (n = 10), adults/en bloc (n = 10), and adults/single (n = 4) KT. Major complications were documented in six adult recipients and one pediatric recipient after en bloc KT. Pediatric recipients showed significantly higher GFR during the first post-transplant year. Kidneys from donors ≤5 yr of age have at least as good outcomes as when transplanted as single allografts into children. Although the study-volume is small, it seems that children benefit from a pediatric-oriented allocation policy.

Size and volume charts of fetal kidney, renal pelvis and adrenal gland

OBJECTIVE

To establish reference curves for size and volume of the fetal kidney, renal pelvis and adrenal gland, as measured using ultrasound from the 15(th) week of gestation.

METHODS

This was a prospective, longitudinal study of 96 fetuses in low-risk singleton pregnancies, in which we performed serial ultrasound examinations at 4-week intervals. The length and anteroposterior and transverse diameters of both kidneys, the anteroposterior and transverse diameters of the renal pelvises and the length of the adrenal glands were measured three times at each examination, with the average being used for further analysis. Reference charts were constructed using multilevel statistical analysis and comparisons were made with previously published charts derived from cross-sectional data.

RESULTS

We present nomograms for fetal kidney dimensions and volume, renal pelvis dimensions and adrenal gland length. The new charts show differences in shape and have narrower percentile bands in comparison to previously published reference ranges.

CONCLUSIONS

These new charts of measurements of the fetal kidney, renal pelvis and adrenal gland, from a prospective, longitudinal study, may be useful in the diagnosis and assessment of pathology of the kidney and adrenal gland.

Genetic variants associated with adult blood pressure and kidney function do not affect fetal kidney volume. The Generation R Study

BACKGROUND

Smaller kidneys with reduced number of nephrons in early life lead to impaired kidney function and risk for hypertension and chronic kidney disease. These associations might be partly explained by common genetic variation.

AIMS

To assess the associations between common genetic variants, which have recently shown to be associated with blood pressure or kidney function, with fetal kidney volume.

STUDY DESIGN

A prospective population based cohort study in Rotterdam, The Netherlands.

SUBJECTS

855 children, followed from early fetal life onwards (born 2003-2005).

PREDICTOR

Common genetic variants previously associated with blood pressure or kidney function.

OUTCOME MEASURES

Combined third trimester fetal kidney volume.

RESULTS

After taking into account multiple testing, only rs12940887 (near ZNF652) was significantly associated with fetal kidney volume (β: 0.88 (95% CI: 0.40; 1.37) cm(3) per minor allele, P-value<0.001), but the effect showed the opposite direction as expected. The remaining common genetic variants were not associated with fetal kidney volume. We also did not find associations of genetic variants previously shown to affect newborn kidney volume, with third trimester fetal kidney volume.

CONCLUSIONS

Our results suggest that common genetic variants, associated with kidney function or disease and blood pressure, do not affect the third trimester fetal kidney volume. Further studies are needed to elucidate the mechanisms underlying the associations between small kidney size and increased risks of hypertension and impaired kidney function in adulthood.

Maternal smoking during pregnancy and kidney volume in the offspring: the Generation R Study

An adverse fetal environment leads to smaller kidneys, with fewer nephrons, which might predispose an individual to the development of kidney disease and hypertension in adult life. In a prospective cohort study among 1,072 children followed from early fetal life onward, we examined whether maternal smoking during pregnancy, as a significant adverse fetal exposure, is associated with fetal (third trimester of pregnancy, n = 1,031) and infant kidney volume (2 years of age, n = 538) measured by ultrasound. Analyses were adjusted for various potential confounders. Among mothers who continued smoking, we observed dose-dependent associations between the number of cigarettes smoked during pregnancy and kidney volume in fetal life. Smoking less than five cigarettes per day was associated with larger fetal combined kidney volume, while smoking more than ten cigarettes per day tended to be associated with smaller fetal combined kidney volume (p for trend: 0.002). This pattern was not significant for kidney volume at the age of 2 years. Our results suggest that smoking during pregnancy might affect kidney development in fetal life with a dose-dependent relationship. Further studies are needed to assess the underlying mechanisms and whether these differences in fetal kidney volume have postnatal consequences for kidney function and blood pressure.

The Generation R Study: design and cohort update 2010

The Generation R Study is a population-based prospective cohort study from fetal life until young adulthood. The study is designed to identify early environmental and genetic causes of normal and abnormal growth, development and health during fetal life, childhood and adulthood. The study focuses on four primary areas of research: (1) growth and physical development; (2) behavioural and cognitive development; (3) diseases in childhood; and (4) health and healthcare for pregnant women and children. In total, 9,778 mothers with a delivery date from April 2002 until January 2006 were enrolled in the study. General follow-up rates until the age of 4 years exceed 75%. Data collection in mothers, fathers and preschool children included questionnaires, detailed physical and ultrasound examinations, behavioural observations, and biological samples. A genome wide association screen is available in the participating children. Regular detailed hands on assessment are performed from the age of 5 years onwards. Eventually, results forthcoming from the Generation R Study have to contribute to the development of strategies for optimizing health and healthcare for pregnant women and children.

Kidney growth in twin children born small for gestational age

BACKGROUND

Low birth weight (LBW) is associated with adult-onset diseases, including hypertension and renal disease; altered renal development after intrauterine growth restriction (IUGR) may underlie related prenatal programming. No data are available on longitudinal renal growth in twin infants born small for gestational age (SGA). The aim of this prospective longitudinal study was to estimate the renal size during the first 2 years of life in SGA twin infants.

METHODS

The study included 613 children, of which 145 were SGA twins, 141 twins appropriate for gestational age (AGA), 148 matched AGA singletons and 179 matched SGA singletons, classified according to GA into two groups (28-36 and >36 weeks). The SGA children were also classified according to the degree of IUGR: birth weight (BW) <3rd percentile and BW 3rd-10th percentiles. Serial renal ultrasonography (US) for kidney length (KL) measurement was performed at the ages of 36 and 40 weeks corrected age (CA) and 3, 6, 12 and 24 months of age, and KL was related to other anthropometric indices. Twin data were examined both as individuals and as members of twin pairs.

RESULTS

A total of 2317 measurements were performed. KL was lower at 40 weeks CA in all the SGA twin subgroups. In the SGA twins with GA >36 weeks, KL increased thereafter and became similar to AGA twins and single AGA control subjects. Among pre-term infants of GA <36 weeks, only those with BW 3rd-10th percentile experienced catch-up in KL, while in those with BW <3rd percentile, KL remained lower than in AGA infants throughout the study period, both in absolute terms and relative to other anthropometric indices. No differences in KL were found between twin SGA and singleton SGA or between twin AGA and singleton AGA infants. Intrapair BW differences were correlated with the intrapair differences in KL.

CONCLUSIONS

Twin SGA infants born prematurely with BW <3rd percentile are unable to achieve catch-up in KL in the first 24 months of life, and long-term follow-up is recommended.