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

Multilevel multinomial regression analysis of factors associated with birth weight in sub-Saharan Africa

Birth weight significantly determines newborns immediate and future health. Globally, the incidence of both low birth weight (LBW) and macrosomia have increased dramatically including sub-Saharan African (SSA) countries. However, there is limited study on the magnitude and associated factors of birth weight in SSA. Thus, thus study investigated factors associated factors of birth weight in SSA using multilevel multinomial logistic regression analysis. The latest demographic and health survey (DHS) data of 36 sub-Saharan African (SSA) countries was used for this study. A total of a weighted sample of 207,548 live births for whom birth weight data were available were used. Multilevel multinomial logistic regression model was fitted to identify factors associated with birth weight. Variables with p-value < 0.2 in the bivariable analysis were considered for the multivariable analysis. In the multivariable multilevel multinomial logistic regression analysis, the adjusted Relative Risk Ratio (aRRR) with the 95% confidence interval (CI) was reported to declare the statistical significance and strength of association. The prevalence of LBW and macrosomia in SSA were 10.44% (95% CI 10.31%, 10.57%) and 8.33% (95% CI 8.21%, 8.45%), respectively. Maternal education level, household wealth status, age, and the number of pregnancies were among the individual-level variables associated with both LBW and macrosomia in the final multilevel multinomial logistic regression analysis. The community-level factors that had a significant association with both macrosomia and LBW were the place of residence and the sub-Saharan African region. The study found a significant association between LBW and distance to the health facility, while macrosomia had a significant association with parity, marital status, and desired pregnancy. In SSA, macrosomia and LBW were found to be major public health issues. Maternal education, household wealth status, age, place of residence, number of pregnancies, distance to the health facility, and parity were found to be significant factors of LBW and macrosomia in this study. Reducing the double burden (low birth weight and macrosomia) and its related short- and long-term effects, therefore, calls for improving mothers' socioeconomic status and expanding access to and availability of health care.

Impact of preterm birth on kidney health and development

Preterm birth, defined as birth before the gestational age of 37 weeks, affects 11% of the newborns worldwide. While extensive research has focused on the immediate complications associated with prematurity, emerging evidence suggests a link between prematurity and the development of kidney disease later in life. It has been demonstrated that the normal course of kidney development is interrupted in infants born prematurely, causing an overall decrease in functional nephrons. Yet, the pathogenesis leading to the alterations in kidney development and the subsequent pathophysiological consequences causing kidney disease on the long-term are incompletely understood. In the present review, we discuss the current knowledge on nephrogenesis and how this process is affected in prematurity. We further discuss the epidemiological evidence and experimental data demonstrating the increased risk of kidney disease in these individuals and highlight important knowledge gaps. Importantly, understanding the intricate interplay between prematurity, abnormal kidney development, and the long-term risk of kidney disease is crucial for implementing effective preventive and therapeutic strategies.

Early postnatal nutrition and renal consequences in preterm infants

Perinatal nutritional factors may lead to decreased nephron endowment, decreased kidney function, and long-term development of chronic kidney disease and non-communicable diseases. At the same time, optimal postnatal nutrition and catch-up growth are associated with better neurodevelopmental outcomes in preterm infants. Therefore, nutritional management of preterm infants is a major challenge for neonatologists. In this context, the Section of Nutrition, Gastroenterology and Metabolism reviewed the current knowledge on nutritional issues related to kidney function. This narrative review discusses the clinical impact of early postnatal nutrition on long-term kidney function. In preterm infants, data are largely lacking to determine the extent to which early nutrition contributes to nephrogenesis and nephron endowment. However, some nutritional principles may help clinicians better protect the developing kidney in preterm infants. IMPACT: Clinical data show that preterm infants are an emerging population at high risk for chronic kidney disease. Both undernutrition and overnutrition can alter long-term kidney function. In preterm infants, data are largely lacking to determine the extent to which early postnatal nutrition contributes to nephrogenesis, nephron endowment and increased risk for chronic kidney disease. Some nutritional principles may help clinicians better protect the developing kidney in preterm infants: avoiding extrauterine growth restriction; providing adequate protein and caloric intakes; limiting exposure to high and prolonged hyperglycaemia; avoiding micronutrient deficiencies and maintaining acid-base and electrolyte balance.

Prematurity and Low Birth Weight and Their Impact on Childhood Growth Patterns and the Risk of Long-Term Cardiovascular Sequelae

Preterm birth (before 37 completed weeks of gestation) is a global health problem, remaining the main reason for neonatal mortality and morbidity. Improvements in perinatal and neonatal care in recent decades have been associated with a higher survival rate of extremely preterm infants, leading to a higher risk of long-term sequelae in this population throughout life. Numerous surveillance programs for formerly premature infants continue to focus on neurodevelopmental disorders, while long-term assessment of the impact of preterm birth and low birth weight on child growth and the associated risk of cardiovascular disease in young adults is equally necessary. This review will discuss the influence of prematurity and low birth weight on childhood growth and cardiovascular risk in children, adolescents and young adults. The risk of cardiovascular and metabolic disorders is increased in adult preterm survivors. In early childhood, preterm infants may show elevated blood pressure, weakened vascular growth, augmented peripheral vascular resistance and cardiomyocyte remodeling. Increased weight gain during the early postnatal period may influence later body composition, promote obesity and impair cardiovascular results. These adverse metabolic alterations contribute to an increased risk of cardiovascular incidents, adult hypertension and diabetes. Preterm-born children and those with fetal growth restriction (FGR) who demonstrate rapid changes in their weight percentile should remain under surveillance with blood pressure monitoring. A better understanding of lifelong health outcomes of preterm-born individuals is crucial for developing strategies to prevent cardiovascular sequelae and may be the basis for future research to provide effective interventions.

Using household survey data to explore the effects of the domiciliary environment on weight at birth: a multilevel mixed-effects analysis of the 2016 Ethiopian Demographic Health Survey

BACKGROUND

Low birth weight (LBW) is associated with infant mortality and postpartum health complications. In previous studies, overall LBW has been found to be significantly associated with several sociodemographic factors, including ethnicity, maternal age, and family income. Few studies have evaluated the association between environmental risk factors and LBW rates. This study investigated the effect of pre-birth water, sanitation, and hygiene (WASH) and housing conditions on self-reported low birth weight.

METHODS

The Ethiopian Demographic and Health Survey, which covered all administrative regions of Ethiopia from January to June 2016, provided data for this study. STATA version 16 was used to analyze 12,125 participants across weighted samples. Multivariable multilevel mixed-effect logistic regression analysis was conducted to determine the effects of each factor on the outcome while accounting for data clustering. The adjusted odds ratios and corresponding 95% confidence intervals were used to determine the statistical significance of the independent variables.

RESULTS

One thousand five hundred and seventeen newborns, or 12.59% [95% CI (10.2- 15.3)], had low birth weights. When other factors were taken into account, the following factors were significantly associated with low birth weight: not using small-scale water treatment technology before using water [AOR (95% CI) 1.36 (1.08-2.23)], burning solid fuels for energy [AOR (95% CI) 1.99 (1.60-2.21)], living in homes with natural wall coverings [AOR (95% CI) 1.81 (1.47-2.21)], using a shared latrine within a woman's housing complex or compound [AOR (95% CI) 1.63(1.06-2.25)], and living in peripheral, isolated regions [AOR (95% CI) 1.38 (1.06-2.21)].

CONCLUSION

A little more than one out of every ten deliveries in Ethiopia was under normal (recommended) weight. This study shows that poor housing conditions and lack of household WASH infrastructure are independent predictors of poor birth outcomes among Ethiopian women, adding to the limited evidence that environmental factors within the domicile contribute to low birth weight. Interventions to address these issues may help lower the prevalence of LBW.

Preterm Birth, Kidney Function and Cardiovascular Disease in Children and Adolescents

Over recent decades, there has been a global increase in preterm birth rate, which constitutes about 11% of total births worldwide. The present review aims to summarize the current knowledge on the long-term consequences of prematurity on renal and cardiovascular development and function. Recent literature supports that prematurity, intrauterine growth restriction or low birth weight (LBW) may have an adverse impact on the development of multiple organ systems, predisposing to chronic diseases in childhood and adulthood, such as arterial hypertension and chronic kidney disease. According to human autopsy and epidemiological studies, children born preterm have a lower nephron number, decreased kidney size and, in some cases, affected renal function. The origin of hypertension in children and adults born preterm seems to be multifactorial as a result of alterations in renal, cardiac and vascular development and function. The majority of the studies report increased systolic and diastolic blood pressure (BP) in individuals born preterm compared to full term. The early prevention and detection of chronic non-communicable diseases, which start from childhood and track until adulthood in children with a history of prematurity or LBW, are important.

Long-term follow-up of patients after acute kidney injury in the neonatal period: abnormal ambulatory blood pressure findings

Background

Data on the long-term effects of neonatal acute kidney injury (AKI) are limited.

Methods

We invited 302 children who had neonatal AKI and survived to hospital discharge; out of 95 patients who agreed to participate in the study, 23 cases were excluded due to primary kidney, cardiac, or metabolic diseases. KDIGO definition was used to define AKI. When a newborn had no previous serum creatinine, AKI was defined as serum creatinine above the mean plus two standard deviations (SD) (or above 97.5^th percentile) according to gestational age, weight, and postnatal age. Clinical and laboratory features in the neonatal AKI period were recorded for 72 cases; at long-term evaluation (2–12 years), kidney function tests with glomerular filtration rate (eGFR) by the Schwartz formula, microalbuminuria, office and 24-h ambulatory blood pressure monitoring (ABPM), and kidney ultrasonography were performed.

Results

Forty-two patients (58%) had stage I AKI during the neonatal period. Mean age at long-term evaluation was 6.8 ± 2.9 years (range: 2.3–12.0); mean eGFR was 152.3 ± 26.5 ml/min/1.73 m². Office hypertension (systolic and/or diastolic BP ≥ 95^th percentile), microalbuminuria (> 30 mg/g creatinine), and hyperfiltration (> 187 ml/min/1.73 m²) were present in 13.0%, 12.7%, and 9.7% of patients, respectively. ABPM was performed on 27 patients, 18.5% had hypertension, and 40.7% were non-dippers; 48.1% had abnormal findings. Female sex was associated with microalbuminuria; low birth weight (< 1,500 g) and low gestational age (< 32 weeks) were associated with hypertension by ABPM. Twenty-three patients (33.8%) had at least one sign of microalbuminuria, office hypertension, or hyperfiltration. Among 27 patients who had ABPM, 16 (59.3%) had at least one sign of microalbuminuria, abnormal ABPM (hypertension and/or non-dipping), or hyperfiltration.

Conclusion

Even children who experienced stage 1 and 2 neonatal AKI are at risk for subclinical kidney dysfunction. Non-dipping is seen in four out of 10 children. Long-term follow-up of these patients is necessary.

The developmental origins of health and chronic kidney disease: Current status and practices in Japan

The concept of the developmental origins of health and disease (DOHaD) views unfavorable perinatal circumstances as contributing to the development of diseases in later life. It is well known that such unfavorable circumstances play an important role as a risk factor for chronic kidney disease (CKD) in infants born with prematurity. Low birthweight (LBW) is believed to be a potential contributor to CKD in adulthood. Preterm and/or LBW infants are born with incomplete nephrogenesis. As a result, the number of nephrons is low. The poor intrauterine environment also causes epigenetic changes that adversely affect postnatal renal function. After birth, hyperfiltration of individual nephrons due to low nephron numbers causes proteinuria and secondary glomerulosclerosis. Furthermore, the risk of CKD increases as renal damage takes a second hit from exposure to nephrotoxic substances and acquired insults such as acute kidney injury after birth among infants in neonatal intensive care. Meanwhile, unfortunately, recent studies have shown that the number of nephrons in healthy Japanese individuals is approximately two-thirds lower than that in previous reports. This means that Japanese premature infants are clearly at a high risk of developing CKD in later life. Recently, several DOHaD-related CKD studies from Japanese researchers have been reported. Here, we summarize the relevance of CKD in conjunction with DOHaD and review recent studies that have examined the impact of the upward LBW trend in Japan on renal health.

Renal morphology and glomerular capillarisation in young adult sheep born moderately preterm

Preterm birth (delivery <37 weeks of gestation) is associated with impaired glomerular capillary growth in neonates; if this persists, it may be a contributing factor in the increased risk of hypertension and chronic kidney disease in people born preterm. Therefore, in this study, we aimed to determine the long-term impact of preterm birth on renal morphology, in adult sheep. Singleton male sheep were delivered moderately preterm at 132 days (~0.9) of gestation (n = 6) or at term (147 days gestation; n = 6) and euthanised at 14.5 months of age (early adulthood). Stereological methods were used to determine mean renal corpuscle and glomerular volumes, and glomerular capillary length and surface area, in the outer, mid and inner regions of the renal cortex. Glomerulosclerosis and interstitial collagen levels were assessed histologically. By 14.5 months of age, there was no difference between the term and preterm sheep in body or kidney weight. Renal corpuscle volume was significantly larger in the preterm sheep than the term sheep, with the preterm sheep exhibiting enlarged Bowman's spaces; however, there was no difference in glomerular volume between groups, with no impact of preterm birth on capillary length or surface area per glomerulus. There was also no difference in interstitial collagen levels or glomerulosclerosis index between groups. Findings suggest that moderate preterm birth does not adversely affect glomerular structure in early adulthood. The enlarged Bowman's space in the renal corpuscles of the preterm sheep kidneys, however, is of concern and merits further research into its cause and functional consequences.

Renal function in short-statured children born small for gestational age and treated with growth hormone

BACKGROUND

Children born small for gestational age (SGA), particularly when associated with an extremely low birthweight (ELBW), have a higher risk of renal dysfunction. Growth hormone (GH) treatment is used to treat short-statured children born SGA; however, its effects on renal function remain elusive, especially in those born SGA with ELBW.

METHODS

Short-statured children born SGA (N = 42) were included. Subjects were subdivided into two groups based on their birthweight: the ELBW group (N = 15) with a birthweight of <1,000 g, and the non-ELBW group (N = 27) with birthweights ranging between 1,000 and 2,500 g. The creatinine-based estimated glomerular filtration rates (eGFR) before (pre-eGFR) and 5 years after GH treatment (post-eGFR) were compared. Correlations between eGFR, anthropometric, or birth parameters, and cumulative GH dose were evaluated using Spearman's rank correlation coefficient.

RESULTS

The ELBW group had a lower pre- and post-eGFR than the non-ELBW group. Five-year GH treatment did not significantly reduce eGFR in either group. Post-eGFR was positively associated with gestational week and birthweight. However, the cumulative GH dose was not correlated with pre-eGFR, post-eGFR, or percentage change in eGFR (%ΔeGFR). The change in bodyweight standard deviation score during GH treatment was positively correlated with %ΔeGFR in the ELBW group.

CONCLUSIONS

The current results indicated that GH treatment was unlikely a risk for the reduction in eGFR in short-statured children born SGA. However, eGFR should be carefully monitored, especially in those born SGA with ELBW because these subjects had lower eGFR than non-ELBW subjects.

Nephron number and its determinants: a 2020 update

Studies of human nephron number have been conducted for well over a century and have uncovered a large variability in nephron number. However, the mechanisms influencing nephron endowment and loss, along with the etiology for the wide range among individuals are largely unknown. Advances in imaging technology have allowed investigators to revisit the principles of renal structure and physiology and their roles in the progression of kidney disease. Here, we will review the latest data on the influences impacting nephron number, innovations made over the last 6 years to understand and integrate renal structure and function, and new developments in the tools used to count nephrons in vivo.

The Long-Term Effect of Preterm Birth on Renal Function: A Meta-Analysis

The preterm-born adult population is ever increasing following improved survival rates of premature births. We conducted a meta-analysis to investigate long-term effects of preterm birth on renal function in preterm-born survivors. We searched PubMed and EMBASE to identify studies that compared renal function in preterm-born survivors and full-term-born controls, published until 2 February 2019. A random effects model with standardized mean difference (SMD) was used for meta-analyses. Heterogeneity of the studies was evaluated using Higgin’s I² statistics. Risk of bias was assessed using the Newcastle–Ottawa quality assessment scale. Of a total of 24,388 articles screened, 27 articles were finally included. Compared to full-term-born controls, glomerular filtration rate and effective renal plasma flow were significantly decreased in preterm survivors (SMD −0.54, 95% confidence interval (CI), −0.85 to −0.22, p = 0.0008; SMD −0.39, 95% CI, −0.74 to −0.04, p = 0.03, respectively). Length and volume of the kidneys were significantly decreased in the preterm group compared to the full-term controls (SMD −0.73, 95% CI, −1.04 to −0.41, p < 0.001; SMD −0.82, 95% CI, −1.05 to −0.60, p < 0.001, respectively). However, serum levels of blood urea nitrogen, creatinine, and cystatin C showed no significant difference. The urine microalbumin to creatinine ratio was significantly increased in the preterm group. Both systolic and diastolic blood pressures were also significantly elevated in the preterm group, although the plasma renin level did not differ. This meta-analysis demonstrates that preterm-born survivors may be subject to decreased glomerular filtration, increased albuminuria, decreased kidney size and volume, and hypertension even though their laboratory results may not yet deteriorate.

Perinatal factors contributing to chronic kidney disease in a cohort of Japanese children with very low birth weight

BACKGROUND

Developmental programming of chronic kidney disease (CKD) in young adults is linked to preterm birth and intrauterine growth restriction (IUGR). Which confers a higher risk of progression to chronic kidney damage in children with very low birth weight (VLBW; born weighing < 1500 g): prematurity or IUGR?

METHODS

This is a national historical cohort study of children with VLBW cared for in perinatal medical centers in Japan. Predictive factors included three latent variables (prematurity, IUGR, stress during neonatal period) and eight observed variables (gestational age, birth weight Z-score, maternal age, duration of treatment with antibiotics and diuretics, maternal smoking, late-onset circulatory collapse, kidney dysfunction) during the perinatal period. The primary endpoint was estimated glomerular filtration rate (eGFR) at age ≥ 3 years. A structural equation model was used to examine the pathologic constitution.

RESULTS

The 446 children with VLBW included 253 boys and 193 girls, of mean age 5.8 ± 2.6 years and mean eGFR 111.7 ml/min/1.73 m² at last encounter. Pathway analyses showed intrauterine malnutrition (β = 0.85) contributed more to chronic kidney damage than stress during the neonatal period (β = - 0.19) and prematurity (β = 0.12), and kidney dysfunction and late-onset circulatory collapse were important observed variables in stress during the neonatal period.

CONCLUSIONS

IUGR was more harmful to future kidneys of VLBW neonates. Neonatal kidney dysfunction and late-onset circulatory collapse were important risk factors for subsequent CKD development. This emphasizes the need for obstetricians to monitor for fetal growth restriction and neonatologists to minimize neonatal stress to prevent CKD in later life.

Cardiovascular risk factors in those born preterm - systematic review and meta-analysis

Emerging evidence demonstrates a link between preterm birth (PTB) and later life cardiovascular disease (CVD). We conducted a systematic review and meta-analysis to compare conventional CVD risk factors between those born preterm and at term. PubMed, CINAHL, SCOPUS, and EMBASE databases were searched. The review protocol is registered in PROSPERO (CRD42018095005). CVD risk factors including systolic blood pressure (SBP), diastolic blood pressure (DBP), body mass index, lipid profile, blood glucose, and fasting insulin among those born preterm (<37 weeks' gestation) were compared with those born at term (≥37 weeks' gestation). Subgroup analyses based on gender, age, gestational at birth (<32 weeks' gestation and <28 weeks' gestation), and PTB associated with small for gestational age or average for gestational age were also performed. Fifty-six studies provided data on 308,987 individuals. Being born preterm was associated with 3.26 mmHg (95% confidence interval [CI] 2.08 to 4.44) higher mean SBP and 1.32 mmHg (95% CI: 0.61 to 2.04) higher mean DBP compared to being born at term. Subgroup analyses demonstrated that SBP was higher among (a) preterm compared to term groups from early adolescence until adulthood; (b) females born preterm but not among males born preterm compared to term controls; and (c) those born at <32 weeks or <28 weeks compared to term. Our meta-analyses demonstrate higher SBP and DBP among those born preterm compared to term. The difference in SBP is evident from early adolescence until adulthood.

Mapping vascular and glomerular pathology in a rabbit model of neonatal acute kidney injury using MRI

Acute kidney injury (AKI) in premature neonates is common due to the administration of life-saving therapies. The impact of AKI on renal morphology and susceptibility to further renal damage is poorly understood. Recent advances in radiological imaging have allowed integration of soft tissue morphology in the intact organ, facilitating a more complete understanding of changes in tissue microstructure associated with pathology. Here, we applied magnetic resonance imaging (MRI) to detect both glomerular and vascular changes in a rabbit model of neonatal AKI, induced by indomethacin and gentamicin. Using combined spin-echo MRI and cationic ferritin enhanced gradient-echo MRI (CFE-MRI), we observed (a) an increased cortical arterial diameter in the AKI cohort compared to healthy controls, and (b) focal loss of vascular density and glomerular loss in a circumferential band ~1 mm from the cortical surface. This combined use of vascular and glomerular imaging may give insight into the etiology of AKI and its impact on renal health later in life.

Reduction in urinary angiotensinogen levels and improvement of proteinuria by renin-angiotensin system blockade in pediatric chronic kidney disease patients with very low birth weight

BACKGROUND

Children with low birth weight (LBW) have an increased risk of developing chronic kidney disease (CKD), and no effective strategies have been established to prevent the progression of CKD in these patients. Urinary angiotensinogen (UAGT) may represent a useful marker of intrarenal renin-angiotensin system (RAS) activation, which has been suggested to play a critical role in the development of hypertension and CKD. Herein, we conducted a prospective study to determine whether RAS blockade is beneficial for suppressing the progression of CKD in children with LBW, using UAGT as a surrogate marker of renal impairment.

METHODS

Nine children with CKD (stages: 1-2) who had very low birth weight (VLBW; < 1500 g) were started on RAS blockade with candesartan. We measured blood pressure and laboratory parameters, including urinary concentrations of angiotensinogen, protein, albumin, creatinine (Cr), and estimated glomerular filtration rate (eGFR), before and after candesartan treatment.

RESULTS

Birth weight was 712 g (range, 536-800 g). Age at evaluation was 11.6 years (range, 10.3-15.6 years). After candesartan treatment for 47.6 ± 25.0 months, the UAGT to urinary Cr ratio decreased from 61.9 ± 44.7 to 16.8 ± 14.4 μg/g (p = 0.015). The urinary protein to Cr and albumin to Cr ratios also decreased (p = 0.008 and p = 0.012, respectively), whereas there was no significant change in eGFR.

CONCLUSIONS

RAS blockade reduced UAGT levels and improved proteinuria/albuminuria in children with CKD who had VLBW. Suppression of intrarenal RAS activity may slow the progression of CKD in children with LBW.

Glomerular Filtration Rate in Former Extreme Low Birth Weight Infants over the Full Pediatric Age Range: A Pooled Analysis

Various cohort studies document a lower glomerular filtration rate (GFR) in former extremely low birth weight (ELBW, <1000 g) neonates throughout childhood when compared to term controls. The current aim is to pool these studies to describe the GFR pattern over the pediatric age range. To do so, we conducted a systematic review on studies reporting on GFR measurements in former ELBW cases while GFR data of healthy age-matched controls included in these studies were co-collected. Based on 248 hits, 6 case-control and 3 cohort studies were identified, with 444 GFR measurements in 380 former ELBW cases (median age 5.3–20.7 years). The majority were small (17–78 cases) single center studies, with heterogeneity in GFR measurement (inulin, cystatin C or creatinine estimated GFR formulae) tools. Despite this, the median GFR (mL/min/1.73 m²) within case-control studies was consistently lower (−13%, range −8% to −25%) in cases, so that a relevant minority (15–30%) has a eGFR<90 mL/min/1.73 m²). Consequently, this pooled analysis describes a consistent pattern of reduced eGFR in former ELBW cases throughout childhood. Research should focus on perinatal risk factors for impaired GFR and long-term outcome, but is hampered by single center cohorts, study size and heterogeneity of GFR assessment tools.

Albuminuria, Hypertension, and Reduced Kidney Volumes in Adolescents Born Extremely Premature

Background: Premature birth is associated with decreased nephron number and an increased risk for chronic kidney disease (CKD). To inform the development of guidelines for kidney follow up of children born prematurely, we undertook a study of individuals born extremely preterm, with the aim of characterizing the prevalence and predictors of microalbuminuria, elevated blood pressure, and/or abnormal kidney volume in adolescence. Methods: Study participants (n = 42) were born before 28 weeks of gestation and were enrolled at birth in the Extremely Low Gestational Age Newborns (ELGAN) study. When participants were 15 years old, we obtained 2 manual blood pressures, a spot urine microalbumin measurement, and sonographic measurements of kidney length and volume. Results: Of the 42 participants, 60% were male, 52% were Caucasian (18% Hispanic), and 43% were African-American. Their median age was 15 (IQR 15, 15.3) years. In 33.3% of the cohort, blood pressure was elevated (>120/80 mmHg). Microalbuminuria (>30 mg/g) was present in 11.9% of the cohort, and kidney volume below the 10th percentile of normative data was present in 14%. Twenty-one (50%) of the sample had at least one kidney abnormality (microalbuminuria, elevated blood pressures, and/or kidney hypoplasia); these individuals were more likely to have experienced neonatal hypotension [55% vs. 17% among those with no kidney abnormality, p = 0.02]. Conclusions: Half of adolescents in this subset of ELGAN cohort have at least one risk factor of kidney disease (reduced kidney volume, microalbuminuria, and/or elevated blood pressures) at 15 years of age. This study suggests the importance of monitoring kidney outcomes in children after extremely preterm birth, especially those with a history of neonatal hypotension.

Associated factors for acute kidney injury in preterm infants

ABSTRACT Objective: to analyze the prevalence and factors associated with acute kidney injury in preterm newborns. Method: a cross-sectional study based on records data of preterm newborns hospitalized in two neonatal units in northwest Paraná State in 2015. For data analysis, the logistic regression model was used by the stepwise forward method and Fisher’s Exact Test. Results: 132 preterm newborns, with a prevalence of 7.5% of acute kidney injury, were hospitalized. Majority of males, extremely preterm and very low birth weight. Associated factors were the use of non-nephrotoxic antibiotics and the presence of mechanical pulmonary ventilation, increasing the chance of developing acute kidney damage by 2.98 and 1.33/day, respectively. Hospitalization days constituted a protection factor. Conclusion: this study was able to identify the prevalence, and outline the variables associated with acute kidney injury in preterm newborns in a particular care situation.

Clinical consequences of developmental programming of low nephron number

Nephron number in humans varies up to 13-fold, likely reflecting the impact of multiple factors on kidney development, including inherited body size and ethnicity, as well as maternal health and nutrition, fetal exposure to gestational diabetes or preeclampsia and other environmental factors, which may potentially be modifiable. Such conditions predispose to low or high offspring birth weight, growth restriction or preterm birth, which have all been associated with increased risks of higher blood pressures and/or kidney dysfunction in later life. Low birth weight, preterm birth, and intrauterine growth restriction are associated with reduced nephron numbers. Humans with hypertension and chronic kidney disease tend to have fewer nephrons than their counterparts with normal blood pressures or kidney function. A developmentally programmed reduction in nephron number therefore enhances an individual's susceptibility to hypertension and kidney disease in later life. A low nephron number at birth may not lead to kidney dysfunction alone except when severe, but in the face of superimposed acute or chronic kidney injury, a kidney endowed with fewer nephrons may be less able to adapt, and overt kidney disease may develop. Given that millions of babies are born either too small, too big or too soon each year, the population impact of altered renal programming is likely to be significant. Many gestational exposures are modifiable, therefore urgent attention is required to implement public health measures to optimize maternal, fetal, and child health, to prevent or mitigate the consequences of developmental programming, to improve the health future generations.

Extremely Low Birth Weight Predisposes to Impaired Renal Health: A Pooled Analysis

BACKGROUND

A number of studies examined the association between preterm delivery and kidney size and function later in life. However, the number of cases in published cohort studies is low. This study was aimed at performing a multicenter collaboration to pool data to obtain more accurate results to quantify the extent of renal impairment in former extremely low birth weight (ELBW; <1,000 g) children.

METHODOLOGY

We performed a subject-level meta-analysis to pool data from Cracow (64 cases/34 controls) and Leuven (93 cases/87 controls). We assessed and analyzed cystatin C, estimated glomerular filtration rate (eGFR), ultrasound kidney length, and blood pressure (BP) in 11-year-old ELBW children compared with controls born at term. The prevalence of hypertension (HT) and prehypertension (preHT) in both groups was also analyzed.

RESULTS

The study group comprised 157 former ELBW children (gestational age 23-33 weeks and birth weight 430-1,000 g) and 123 children born at term. Former ELBW children had lower mean eGFR (100.62 ± 16.53 vs. 111.89 ± 15.26 mL/min/1.73 m2; p < 0.001), smaller absolute kidney length (8.56 ± 0.78 vs. 9.008 ± 0.73 cm; <0.001), and higher systolic (111.8 ± 9.8 vs. 107.2 ± 9.07 mm Hg; p = 0.01) and diastolic (68.6 ± 6.8 vs. 66.3 ± 7.7 mm Hg; p = 0.03) BP. Smaller renal size in former ELBW children was positively associated with lower birth weight, shorter gestational age, and severity of perinatal complications (intraventricular hemorrhage, length of stay, mechanical ventilation, and oxygen therapy).

CONCLUSION

ELBW is associated with lower eGFR and a high frequency of preHT and HT.

Effects of Prenatal Growth Status on Subsequent Childhood Renal Function Related to High Blood Pressure

BACKGROUND

Hypertension is one of the major causes of chronic diseases. The effect on high blood pressure (BP) with fetal growth restriction is now well-established. Recent studies suggest that a reduced number of nephrons programmed during the intrauterine period contribute to a subsequently elevated BP, due to a permanent nephron deficit. However, few studies have examined this in children. We investigated the effects of low birth weight (LBW) and preterm birth on the renal function markers related to a high BP in childhood.

METHODS

We used data from 304 children aged 7-12 years who participated in the 2014 Ewha Birth and Growth Cohort survey in Korea. We assessed the serum uric acid, cystatin C, blood urea nitrogen (BUN), creatinine levels, and the estimated glomerular filtration rate (eGFR) in childhood. Anthropometric characteristics, BP in childhood, birth weight and gestational age were collected.

RESULTS

The serum uric acid was significantly higher in LBW children (4.0 mg/dL) than in normal birth weight children (3.7 mg/dL). The cystatin C levels were highest among children who were very preterm (0.89 mg/dL) compared with those who were not (preterm, 0.84 mg/dL; normal, 0.81 mg/dL), although the result was only borderline significant (P for trend = 0.06). Decreased birth weight was found to be significantly associated with an increased serum BUN level in childhood. In the analysis of the effects of renal function on BP, subjects with an eGFR lower than the median value had a significantly higher diastolic BP in childhood (difference = 2.4 mmHg; P < 0.05).

CONCLUSION

These findings suggest that LBW and preterm birth are risk factors for increased serum levels of renal function markers in childhood. Reduced eGFR levels were significantly associated with elevated diastolic BP in childhood. It is necessary to identify vulnerable individuals during their life and intervene appropriately to reduce the risk of an increased BP in the future.

Kidney Size, Renal Function, Ang (Angiotensin) Peptides, and Blood Pressure in Young Adults Born Preterm

Preterm birth incurs a higher risk for adult cardiovascular diseases, including hypertension. Because preterm birth may impact nephrogenesis, study objectives were to assess renal size and function of adults born preterm versus full term and to examine their relationship with blood pressure (BP; 24-hour ambulatory BP monitoring) and circulating renin-Ang (angiotensin) system peptides. The study included 92 young adults born (1987-1997) preterm (≤29 weeks of gestation) and term (n=92) matched for age, sex, and race. Young adults born preterm had smaller kidneys (80±17 versus 90±18 cm³/m²; P<0.001), higher urine albumin-to-creatinine ratio (0.70; interquartile range, 0.47-1.14 versus 0.58, interquartile range 0.42 to 0.78 mg/mmol, P=0.007), higher 24-hour systolic (121±9 versus 116±8 mm Hg; P=0.001) and diastolic (69±5 versus 66±6 mm Hg; P=0.004) BP, but similar estimated glomerular filtration rate. BP was inversely correlated with kidney size in preterm participants. Plasma Ang I was higher in preterm versus term participants (36.3; interquartile range, 13.2-62.3 versus 19.4; interquartile range, 9.9-28.1 pg/mL; P<0.001). There was no group difference in renin, Ang II, Ang (1-7), and alamandine. In the preterm, but not in the term group, higher BP was significantly associated with higher renin and alamandine and lower birth weight and gestational age with smaller adult kidney size. Young adults born preterm have smaller kidneys, higher urine albumin-to-creatinine ratio, higher BP, and higher circulating Ang I levels compared with term controls. Preterm young adults with smaller kidneys have higher BP. Clinical Trial Registration- URL: http://www.clinicaltrials.gov . Unique identifier: NCT03261609.

Renal function in prepubertal children born with very low birthweight

OBJECTIVES

The objective of this study was to evaluate estimated glomerular filtration rates (eGFR) and markers of renal function in very low birthweight (VLBW) children and to relate these parameters to current nutritional status.

METHODS

A cross-sectional and controlled study was performed with prepubertal children between ages 5 and 10, including 44 VLBW participants and 30 healthy participants born at full term with an adequate birthweight (control group). The following data were collected: perinatal history; current weight, height and waist circumference; blood pressure (three measures); blood creatinine, urea, uric acid, cystatin-C, and neutrophil gelatinase-associated lipocalin levels; and urine albumin, creatinine, and calcium levels.

RESULTS

Blood pressure, eGFR, albuminuria, concentrations of cystatin-C, neutrophil gelatinase-associated lipocalin, uric acid, urea, creatinine, and fractional calcium excretion did not differ between VLBW and control groups. Regarding the VLBW group, there was no difference in eGFR, albuminuria, and other markers of renal injury in overweight or obese children compared with children with a normal body mass index.

CONCLUSIONS

Prepubertal children born with VLBW did not have altered renal function, regardless of their current nutritional status.

Renal function and blood pressure are altered in adolescents born preterm

BACKGROUND

Preterm birth increases the risk of hypertension and kidney disease. However, it is unclear when changes in blood pressure (BP) and renal function become apparent and what role obesity and sex play. We hypothesized adolescents born preterm have higher BP and worse kidney function compared to term in an obesity- and sex-dependent manner.

METHODS

Cross-sectional analysis of 14-year-olds born preterm with very low birth weight (n = 96) compared to term (n = 43). We used generalized linear models to estimate the associations among preterm birth and BP, estimated glomerular filtration rate (eGFR), and ln (x) urinary albumin-to-creatinine ratio (ACR), stratified by overweight/obesity (OWO, body mass index (BMI) ≥ 85th percentile) and sex.

RESULTS

Compared to term, preterm-born adolescents had higher systolic blood pressure (SBP) and diastolic blood pressure (DBP) (adjusted β (aβ) 3.5 mmHg, 95% CI - 0.1 to 7.2 and 3.6 mmHg, 95% CI 0.1 to 7.0), lower eGFR (β - 8.2 mL/min/1.73 m², 95% CI - 15.9 to - 0.4), and higher ACR (aβ 0.34, 95% CI - 0.04 to 0.72). OWO modified the preterm-term difference in DBP (BMI < 85th percentile aβ 5.0 mmHg, 95% CI 0.7 to 9.2 vs. OWO 0.2 mmHg, 95% CI - 5.3 to 5.6) and ACR (OWO aβ 0.72, 95% CI 0.15 to 1.29 vs. BMI < 85th percentile 0.17, 95% CI - 0.31 to 0.65). Sex modified the preterm-term ACR difference (female aβ 0.52, 95% CI 0.001 to 1.04 vs. male 0.18, 95% CI - 0.36 to 0.72).

CONCLUSIONS

Prematurity was associated with higher BP and reduced renal function that were detectable in adolescence. OWO and sex may modify the strength of these relationships.

Kidney volume, kidney function, and ambulatory blood pressure in children born extremely preterm with and without nephrocalcinosis

BACKGROUND

Reduced kidney volume (KV) following prematurity is a proxy for reduced nephron number and is associated with the development of hypertension and end-stage renal disease in adults. We investigated whether extreme prematurity affects KV, function, and blood pressure in school-aged children and if nephrocalcinosis (NC) developed during the neonatal period had additional effects.

METHODS

We investigated 60 children at a mean age of 7.7 years: 20 born extremely preterm (EPT < 28 weeks gestational age with NC (NC+)), 20 born EPT without NC (NC-), and 19 born as full-term infants (control). We measured KV by ultrasound, collected blood and urine samples to evaluate renal function, and measured office and 24-h ambulatory blood pressure (ABPM).

RESULTS

Children born EPT had significantly smaller kidneys (EPT (NC+ NC-) vs control (estimated difference, 11.8 (CI - 21.51 to - 2.09 ml), p = 0.018) and lower but normal cystatin C-based glomerular filtration rate compared with control (estimated difference, - 10.11 (CI - 0.69 to - 19.5), p = 0.035). KV and function were not different between NC+ and NC- groups. Change in KV in relation to BSA (KV/BSA) from the neonatal period to school age showed significantly more EPT children with neonatal NC having a negative evolution of KV (p = 0.01). Blood pressure was normal and not different between the 3 groups. Fifty percent of EPT had a less than 10% day-to-night decline in ABPM.

CONCLUSIONS

Kidney growth and volume is affected by EPT birth with NC being a potential aggravating factor. Circadian blood pressure regulation seems abnormal in EPT-born children.

Tubular dysfunction in extremely low birth weight survivors

BACKGROUND

Extremely low birth weight (ELBW) survivors may develop glomerulosclerosis due to low nephron number, whereas their tubular function remains unknown except for hypercalciuria and phosphaturia.

METHODS

Fifty-three subjects (30 boys and 23 girls, aged 7 months-19 years, median 36 months) were studied retrospectively. The median gestational age and birth weight were 26 weeks (range 22-32) and 745 g (range 316-999), respectively. Urine calcium-to-creatinine ratio (Ca/Cr), N-acetyl-β-D-glucosaminidase-to-creatinine ratio (NAG/Cr), β2 microglobulin-to-creatinine ratio (β2m/Cr), uric acid-to-creatinine ratio (UA/Cr), glucose-to-creatinine ratio (glu/Cr), and microalbumin-to-creatinine ratio (malb/Cr) were examined. We also assessed the association between urine parameters and current age, gestational age, birth weight, and predictors of renal injury. Follow-up data were analyzed in 43 subjects 4-6 years later.

RESULTS

Ninety percent of subjects had at least one tubular dysfunction. Frequency of elevated values was NAG/Cr 77.5%, UA/Cr 54.1%, β2m/Cr 38.2%, malb/Cr 30.4%, Ca/Cr 21.5%, and glu/Cr 20.5%. There were significant negative correlations between the current age and Ca/Cr, NAG/Cr, glu/Cr, and UA/Cr, suggesting tubular function maturation. Urine β2M/Cr and glu/Cr were negatively correlated with the gestational age. There were significant associations between elevated glu/Cr and asphyxia or neonatal acute kidney injury, and elevated NAG/Cr and indomethacin use, although these were not confirmed by multivariate analysis. At follow-up, the frequency of elevated NAG/Cr, glu/Cr, UA/Cr, and malb/Cr was reduced but that of elevated Ca/Cr, IgG/Cr, and β2m/Cr remained similar or increased.

CONCLUSION

Tubular dysfunction is common in ELBW survivors. Some abnormalities resolved with age while some remained persistent or even increased.

Proteinuric glomerulopathy in an adolescent with a distal partial trisomy chromosome 1

We report a case of distal partial trisomy 1 from q32.1 to 41 that have exhibited proteinuric glomerulopathy. The patient was a 17-year-old adolescent with clinical features of low birth weight, mild mental retardation and mild deafness, from the birth. He exhibited non-nephrotic range proteinuria with the mild obesity since the age of sixteen. Image studies did not reveal morphological abnormalities of the kidneys. Renal biopsy findings showed no definitive evidence of primary glomerular diseases, and were characterized by a very low glomerular density, glomerulomegaly and focal effacement of podocyte foot processes. Therapies with dietary sodium restriction, body weight reduction and the administration of angiotensin receptor blocker markedly reduced his proteinuria. It was likely that mismatch between congenital reduction in the nephron number and catch-up growth of the whole body size played a major role in the development of glomerular hyperperfusion injury. At present, the direct contribution of genetic factors due to this chromosomal disorder to such a substantial reduction in the nephron number remains uncertain.

Risk factors associated with a decreased estimated glomerular filtration rate based on cystatin C levels in school-age children with extremely low birthweight

AIM

A single centre retrospective cohort study was designed to investigate the estimated glomerular filtration rate (eGFR) in school-age children born with extremely low birthweight (ELBW) and to determine risk factors predictive of decreased eGFR.

METHODS

We compared eGFR based on cystatin C (CysC-eGFR) between school-age children born with ELBW (ELBW group, n = 48; median gestational age: 26.9 weeks; median birthweight: 792 g) and children born at term (control group, n = 48). The ELBW group was then further divided into a decreased CysC-eGFR subgroup (eGFR <90 mL/min per 1.73 m² , n = 20) and a normal CysC-eGFR subgroup (n = 28), and perinatal background factors were compared.

RESULTS

The ELBW group showed a significantly lower CysC-eGFR compared with the control group (P < 0.001). Comparison between the decreased and normal CysC-eGFR subgroups in the ELBW group showed that children with lower birthweight, shorter gestational age, lower 5-min Apgar score, longer length of mechanical ventilation, lower weight gain in the first 11 weeks, chronic lung disease, and postnatal corticosteroid administration had significantly decreased CysC-eGFR. Multivariate logistic regression showed that a lower 5-min Apgar score was the only independent risk factor for decreased CysC-eGFR.

CONCLUSIONS

CysC-eGFR might already be decreased at school age in children born with ELBW. Renal assessment in regular follow-up examinations is recommended.

Association among prematurity (<30 weeks' gestational age), blood pressure, urinary albumin, calcium, and phosphate in early childhood

BACKGROUND

There is a paucity of data on blood pressures (BP), urinary albumin, and mineral excretion in early childhood in contemporary cohorts of extremely low gestational age (GA) neonates. Our aim was to compare BPs and the urinary excretion of albumin, calcium, and phosphate in preterm and term-born cohorts in early childhood.

METHODS

This was a prospective observational study conducted at a single center, involving children <5 years age, born preterm (GA <30 weeks) or at term (≥37 weeks' GA). Urinary albumin (mg/L), calcium and phosphate levels indexed to creatinine (mg/dL), and BP were measured.

RESULTS

The median (IQR) follow-up age of our cohort (n = 106) was 30 (16-48) months. Preterm-born children (n = 55) had a significantly lower mean GA and birth weight and higher mean systolic, diastolic, and mean BPs, compared with term (n = 51) controls. A significantly higher proportion of preterm-born children weighed <10th centile and had systolic BP >95th centile at follow-up. Albumin and calcium excretion did not differ between the groups; median urine-phosphate creatinine ratios were higher in the preterm group. On logistic regression, lower GA and younger age at follow-up were significantly associated with an increased risk of systolic and diastolic BP above the 95th centile; male gender was associated with decreased risk of diastolic hypertension.

CONCLUSIONS

Even in early childhood, children born preterm had significantly elevated BP, compared with their term-born counterparts. Closer monitoring of BPs in this population may be warranted.

Long-Term Impact of Preterm Birth: Neurodevelopmental and Physical Health Outcomes

Preterm birth severely disrupts the normal developmental maturation of organ systems, resulting in lasting adverse effects. High blood pressure, cardiac dysfunction, obstructive lung disease, elevated blood glucose, and mental health problems occur earlier and at higher rates in the preterm-born than in the term populations. Disadvantageous health conditions may have a significant impact on the well-being of preterm-born individuals from childhood through adulthood. This review summarizes the impact of preterm birth on neurodevelopment and on cardiovascular, renal, metabolic, and pulmonary health.

Impaired nephrogenesis in neonatal rats with oxygen-induced retinopathy

BACKGROUND

Preterm neonates are born while nephrogenesis is ongoing, and are commonly exposed to factors in a hyperoxic environment that can impair renal development. Oxidative stress has also been implicated in the development of retinopathy of prematurity (ROP). The rat model of oxygen-induced retinopathy (OIR) is the most clinically relevant model of ROP because its biologic features closely resemble those of ROP in preterm infants. We investigated impaired renal development in a rat model of OIR.

METHODS

Newborn Sprague-Dawley rats were maintained in either a normoxic (room air, 21% O₂ ; control group) or a controlled hyperoxic (80% O₂ ; OIR group) environment from birth to postnatal day (P) 12. All pups were then raised in room air from P12 to P19.

RESULTS

The hyperoxic environment led to significantly higher urinary excretion of 8-hydroxy-2'-deoxyguanosine, a marker of oxidative DNA damage, and a reduction in nephrogenic zone width at P5 in OIR pups. Additionally, glomerular count was significantly reduced by 20% in the OIR group, and avascular and neovascular changes in the retina were observed only in the OIR group at P19. Messenger RNA levels of vascular endothelial growth factor-A (VEGF-A) and platelet-derived growth factor-β, essential angiogenic cytokines for glomerulogenesis, in the renal cortex were significantly lower at P5 and significantly higher at P19 in the OIR group compared with controls.

CONCLUSION

Renal impairment was caused by exposure to a hyperoxic environment during nephrogenesis, and the pathology of the impaired nephrogenesis in this OIR model reflects the characteristics of ROP observed in preterm infants.

Adult Consequences of Extremely Preterm Birth: Cardiovascular and Metabolic Diseases Risk Factors, Mechanisms, and Prevention Avenues

Extremely preterm babies are exposed to various sources of injury during critical stages of development. The extremely preterm infant faces premature transition to ex utero physiology and undergoes adaptive mechanisms that may be deleterious in the long term because of permanent alterations in organ structure and function. Perinatal events can also directly cause structural injury. These disturbances induce morphologic and functional changes in their organ systems that might heighten their risks for later adult chronic diseases. This review examines the pathophysiology of programming of long-term health and diseases after preterm birth and associated perinatal risk factors.

The Impact of Kidney Development on the Life Course: A Consensus Document for Action

Hypertension and chronic kidney disease (CKD) have a significant impact on global morbidity and mortality. The Low Birth Weight and Nephron Number Working Group has prepared a consensus document aimed to address the relatively neglected issue for the developmental programming of hypertension and CKD. It emerged from a workshop held on April 2, 2016, including eminent internationally recognized experts in the field of obstetrics, neonatology, and nephrology. Through multidisciplinary engagement, the goal of the workshop was to highlight the association between fetal and childhood development and an increased risk of adult diseases, focusing on hypertension and CKD, and to suggest possible practical solutions for the future. The recommendations for action of the consensus workshop are the results of combined clinical experience, shared research expertise, and a review of the literature. They highlight the need to act early to prevent CKD and other related noncommunicable diseases later in life by reducing low birth weight, small for gestational age, prematurity, and low nephron numbers at birth through coordinated interventions. Meeting the current unmet needs would help to define the most cost-effective strategies and to optimize interventions to limit or interrupt the developmental programming cycle of CKD later in life, especially in the poorest part of the world.

Age- and sex-related changes in rat renal function and pathology following neonatal hyperoxia exposure

Preterm neonates are prematurely exposed to high oxygen levels at birth which may adversely impact ongoing renal development. The aim of this study was to determine the effects of neonatal hyperoxia exposure on renal function and morphology with aging. Sprague Dawley rat pups were raised in a hyperoxic environment (80% oxygen) from P3 to P10 during ongoing postnatal nephrogenesis. Control litters were kept in room air (n = 6–8 litters/group; one male, one female/litter/age). Kidney function (urine and plasma creatinine, sodium, and protein) and morphology (renal corpuscle size, glomerulosclerosis, fibrosis, and glomerular crescents) were assessed at 1, 5, and 11 months of age. Neonatal hyperoxia exposure had no impact on body or kidney weights. Creatinine clearance was significantly reduced following hyperoxia exposure at 5 months; there was no significant effect on renal function at 1 or 11 months. The percentage of crescentic glomeruli (indicative of glomerular injury) was markedly increased in 11 month hyperoxia‐exposed males. Renal corpuscle size, glomerulosclerosis index, and renal fibrosis were not affected. Findings suggest that exposure to high oxygen levels during development may impact renal functional capacity and increase susceptibility to renal disease in adulthood depending on age and sex.

Posterior urethral valves: Impact of low birth weight and preterm delivery on the final renal outcome

Objective

To investigate the relationship between low birth weight (LBW; <2.5 kg) and preterm delivery (<37 weeks gestational age) and final renal outcome in infants with posterior urethral valves (PUVs), emphasising the risk factors for the development of chronic kidney disease (CKD).

Patients and methods

A retrospective review was performed for all infants with PUVs who were treated between 1990 and 2010. In all, 52 infants were identified to have LBW and/or delivered preterm (Group 1). Infants in Group 1 were compared with a matching group (Group 2) of 60 full-term normal birth weight (NBW) infants with PUVs managed during the same period. The outcome of both groups was analysed.

Results

During follow-up, CKD developed in 17 (32.5%) and 22 patients (36.5%) in Groups 1 and 2, respectively (P = 0.812). Patients with LBW or delivered preterm had significantly higher incidence of oligohydramnios (P = 0.009), increased risk of vesicostomy (P < 0.001), longer hospital stay (P < 0.001), and higher incidence of vesico-ureteric reflux (VUR, P = 0.024). In the LBW patients, initial serum creatinine, nadir serum creatinine, oligohydramnios and Neonatal Intensive Care Unit (NICU) length of stay were significant predictors of final renal outcome (P < 0.001, P = 0.002, P = 0.004 and P = 0.012, respectively).

Conclusion

In our cohort of LBW and preterm delivery infants with PUVs, outcomes were similar to those of NBW full-term infants with PUVs but with an increased risk of vesicostomy, longer hospital stay, and higher incidence of VUR. LBW was associated with oligohydramnios, longer NICU admission, high initial and nadir serum creatinine, which were associated with a poor prognosis.

Effect of birth weight on adulthood renal function: A bias-adjusted meta-analytic approach

While the association between low birth weight (LBW; <2500 g) and development of adult chronic renal disease (CKD) is inconsistently reported, less information is available regarding association of high birth weight (HBW; ≥4000 g) with CKD. We undertook a systematic review and meta-analysis on studies published before 30 September 2015 and report associations between birth weight and renal function. Blood (glomerular filtration rate (GFR)) and urine (microalbuminuria/albumin excreation rate (AER)/urinary albumin creatinine ratio (ACR)) parameters were used to define CKD. Three different effect size estimates were used (odds ratio, regression coefficient and mean difference). The odds of developing CKD in the life course among those born LBW was 1.77 (95% CI: 1.42, 2.20) times and 1.68 (1.27, 2.33) times, assessed by blood and urine parameters respectively. Higher risk was also observed among Asian and Australian populations (blood: OR 2.68; urine: OR 2.28), individuals aged ≤30 years (blood: OR 2.30; urine: OR 1.26), and ≥50 years (blood: OR 3.66; urine: OR 3.10), people with diabetes (blood: OR 2.51), and aborigines (urine: OR 2.32). There was no significant association between HBW and CKD. For every 1 kg increase in BW, the estimated GFR increased by 2.09 mL/min per 1.73 m(2) (1.33-2.85), and it was negatively associated with LogACR (ß -0.07, 95% CI: -0.14, 0.00). LBW inborn had lower mean GFR -4.62 (-7.10, -2.14) compared with normal BW. Findings of this study suggest that LBW increased the risk of developing CKD, and HBW did not show any significant impact.

The path to chronic kidney disease following acute kidney injury: a neonatal perspective

The risk of acute kidney injury (AKI) in hospitalized critically ill neonatal populations without primary renal disease continues to be high, in both term and premature infants. Observational studies have revealed high rates of chronic kidney disease (CKD) in survivors of neonatal AKI. Proposed mechanisms underlying the progression of CKD following AKI include nephron loss and hyperfiltration, vascular insufficiency and maladaptive repair mechanisms. Other factors, including prematurity and low birth weight, have an independent relationship with the development of CKD, but they may also be positive effect modifiers in the relationship of AKI and CKD. The large degree of heterogeneity in the literature on AKI in the neonatal population, including the use of various AKI definitions and CKD outcomes, has hampered the medical community's ability to properly assess the relationship of AKI and CKD in this vulnerable population. Larger prospective cohort studies with control groups which utilize recently proposed neonatal AKI definitions and standardized CKD definitions are much needed to properly quantify the risk of CKD following an episode of AKI. Until there is further evidence to guide us, we recommend that all neonates with an identified episode of AKI should have an appropriate longitudinal follow-up in order to identify CKD at its earliest stages.

Renal outcome in children born preterm with neonatal acute renal failure: IRENEO-a prospective controlled study

OBJECTIVES

Acute kidney injury (AKI) is a severe complication of prematurity, with currently unknown consequences for renal function in childhood. The objective of this study was to search for signs of reduced nephron number in children aged 3-10 years who had been born preterm with neonatal AKI and compare this group to control children.

METHODS

IRENEO was a prospective, controlled study conducted in 2013 in Nantes University Hospital. Children who were born at less than 33 weeks gestational age (GA) and included in the LIFT cohort were eligible for entry. Twenty-five children with AKI (AKI-C) and 49 no-AKI children were matched on a propensity score of neonatal AKI and age. AKI was defined as a serum creatinine level higher than critical values: 1.6 mg/dl (GA 24-27 weeks), 1.1 mg/dl (28-29) and 1 mg/dl (GA 30-32). Renal function was evaluated during childhood.

RESULTS

Mean age of the children at the time of the study was 6.6 years. No difference in microalbuminuria, estimated glomerular filtration rate (GFR) or pulse wave velocity was observed between the two groups. Renal volume was lower in the AKI-C group (57 vs. 68; p = 0.04). In the entire cohort, 10.8 % had a microalbuminuria, and 23 % had a diminished GFR (median 79 ml/min/1.73 m²). The GFR was lower in children with very low birth weight of <1000 g (99 vs. 107 ml/min/1.73 m²; p = 0.04).

CONCLUSION

In children born preterm, neonatal AKI does not seem to influence renal function. However, independent ofAKI, a large proportion of very preterm infants, especially those with very low birth weight, presented with signs of nephron reduction, thus requiring follow-up with a nephrologist.

Blood Pressure Profile in the 7th and 11th Year of Life in Children Born Prematurely

Background

Several research trials have analyzed the impact of prematurity on the prevalence of hypertension (HT). However, prospective long-term studies are lacking.

Objectives

The aim of this study was to evaluate the prevalence of HT at the age of 7 and 11 years in a regional cohort of preterm infants with a birth weight of ≤ 1000 g.

Patients and Methods

This study included 67 children with a birth weight of ≤ 1000 g who were born in Malopolska between September 2002 and August 2004. The control group consisted of 38 children born at term, matched for age. Each child underwent 24-h ambulatory blood pressure measurement (ABPM) twice, once at the age of 7 and again at 11 years. The presence of HT was estimated according to the mean arterial pressure (MAP) and a number of individual measurements.

Results

At aged 7 years, preterm infants had a significantly higher incidence of HT, defined on the basis of MAP (15% vs. 0%; P < 0.02) and on the percent of individual measurements (56% vs. 33%, P < 0.036). After taking into account the group of patients who received anti-HT treatment after the first part of the study, the incidence of HT at the age of 11 years based on MAP was 19% vs. 10%. Based on the individual measurements, it was 36.5% in the preterm infants vs. 24% in the control group. The differences were not statistically significant. At both time points, the preterm group had a higher mean heart rate (HR) than the control group.

Conclusions

Children born prematurely are predisposed to HT in later life, in addition to the persistence of an increased HR.

Longitudinal assessment of renal size and function in extremely low birth weight children at 7 and 11 years of age

BACKGROUND

There are a lack of studies describing a longitudinal association between preterm delivery and renal complications later in life. We assessed renal size and function in preterm infants born with extremely low birth weight (ELBW) during 4 years of follow-up, comparing these parameters to age-matched children born full term (term controls).

METHODS

The results of selected renal laboratory tests [levels of cystatin C, creatinine, blood urea nitrogen (BUN)] and of renal ultrasound evaluations were compared between the ELBW group and the term control group at age 7 and 11 years.

RESULTS

The study population consisted of 64 children born with ELBW (ELBW children) who had been recruited at birth and 36 children born at term (term children) who took part in both follow-up assessments. Renal ultrasound examination revealed a significantly smaller renal volume in the 7- and 11-year-old ELBW children compared to the term controls [right kidney volume: 50.8 vs. 61.2 ml/m(2), respectively, at 7 years (p <0.01) and 51.4 vs. 58.2 ml/m(2), respectively, at 11 years (p <0.01); left kidney volume: 51.4 vs. 60.3 ml/m(2), respectively, at 7 years (p <0.01) and 55.2 vs. 60.7 ml/m(2), respectively, at 11 years (p = 0.02)]. Renal function in ELBW children was also affected. Serum cystatin C levels were significantly higher in ELBW children than in the controls at 7 years of age, and this difference remained statistically significant at 11 years of age [0.63 vs. 0.59 mg/l, respectively, at 7 years (p = 0.02) and 0.72 vs. 0.61 mg/l, respectively, at 11 years (p = 0.01)]. Six ELBW children also had elevated cystatin C levels (0.97-1.11 mg/l) at 11 years of age. Cystatin C levels were within normal range in the ELBW children at age 7 years and in term children in both follow-up studies. BUN levels were higher in ELBW children at the age of 11 years (4.49 vs. 4.15 mmol/l; p = 0.028).

CONCLUSION

Continued follow-up of these patients will reveal whether the observed worsening in renal function will persist into adulthood.

Proteinuria caused by glomerular hypertension during adolescence associated with extremely premature birth: a report of two cases

BACKGROUND

Prematurity and low birth weight are risk factors for the future development of chronic kidney disease (CKD) and hypertension caused by fewer nephrons with limited filtration surface area. Few reports to date have evaluated their clinical backgrounds and pathological findings, including glomerular hypertension and focal segmental glomerulosclerosis.

CASE-DIAGNOSIS/TREATMENT

This report describes two patients, a 15-year-old girl (patient 1), with a birth weight of 618 g and a gestational age of 24 weeks, and a 14-year-old boy (patient 2), with a birth weight of 842 g and a gestational age at 25 weeks. Both had a birth weight appropriate for gestational age. Both were first diagnosed with proteinuria during adolescence, and patient 2 also had hypertension. Pathological findings included glomerulomegaly in both and hypertrophy of the juxtaglomerular apparatus and perihilar glomerulosclerosis in patient 1, suggesting glomerular hypertension. Treatment with lisinopril resulted in the immediate disappearance of proteinuria. Renal dysfunction was observed in both patients, but neither showed evidence of severe aggravation after a follow-up of 5 or 6 years.

CONCLUSIONS

Proteinuria in both patients was caused by glomerular hypertension with hyperfiltration. Extremely preterm birth itself may be a risk factor for future CKD. Long-term follow-up of patients born prematurely and at low birth weight, including urinalysis and blood pressure measurements, is necessary to diagnose and treat late renal complications.

Birth weight, malnutrition and kidney-associated outcomes--a global concern

An adverse intrauterine environment is associated with an increased risk of elevated blood pressure and kidney disease in later life. Many studies have focused on low birth weight, prematurity and growth restriction as surrogate markers of an adverse intrauterine environment; however, high birth weight, exposure to maternal diabetes and rapid growth during early childhood are also emerging as developmental risk factors for chronic diseases. Altered programming of nephron number is an important link between exposure to developmental stressors and subsequent risk of hypertension and kidney disease. Maternal, fetal, and childhood nutrition are crucial contributors to these programming effects. Resource-poor countries experience the sequential burdens of fetal and childhood undernutrition and subsequent overnutrition, which synergistically act to augment the effects of developmental programming; this observation might explain in part the disproportionate burden of chronic disease in these regions. Numerous nutritional interventions have been effective in reducing the short-term risk of low birth weight and prematurity. Understanding the potential long-term benefits of such interventions is crucial to inform policy decisions to interrupt the developmental programming cycle and stem the growing epidemics of hypertension and kidney disease worldwide.

The Importance of Accurately Assessing Renal Function in the Neonate and Infant

Measuring renal function in neonates and small infants is important to ensure that drugs are safely dosed and to detect acute kidney injuries early on. Serum creatinine (Cr) remains the most widely used marker, but its shortcomings are particularly important in neonates. For example, neonatal Cr largely depends on maternal renal function for at least the first 72 h of life. Novel approaches for assessing neonatal renal function include cystatin C and beta-trace protein. Another way to assess renal function is to measure renal volume by ultrasound. Although this approach may assess neonatal nephron endowment, it is insensitive to the postnatal adaptation of renal function in term and preterm neonates. The purpose of this review is to summarize what is known about measuring renal function in term and preterm newborns, and to summarize existing knowledge gaps, including a description of steps to take to close these gaps.

Long-term renal consequences of preterm birth

The normal development of the kidney may be affected by several factors, including abnormalities in placental function, resulting in fetal growth restriction, exposure to maternal disease states, including hypertension and diabetes, antenatal steroids, chorioamnionitis, and preterm delivery. After preterm birth, several further insults may occur that may influence nephrogenesis and renal health, including exposure to nephrotoxic medications, postnatal growth failure, and obesity after growth restriction. In this review article, common clinical neonatal scenarios are used to highlight these renal risk factors, and the animal and human evidence on which these risk factors are based are discussed.

Hyperoxia exposure impairs nephrogenesis in the neonatal rat: role of HIF-1α

Preterm neonates are exposed at birth to high oxygen concentrations relative to the intrauterine environment. We have previously shown in a rat model that a hyperoxic insult results in a reduced nephron number in adulthood. Therefore, the aim of this study was to determine the effects of transient neonatal hyperoxia exposure on nephrogenesis. Sprague-Dawley rat pups were raised in 80% O₂ or room air from P3 to P10. Pups (n = 12/group, 6 males and 6 females) were sacrificed at P5 (during active nephrogenesis) and at P10 (after the completion of nephrogenesis). Hyperoxia exposure resulted in a significant reduction in both nephrogenic zone width and glomerular diameter at P5, and a significantly increased apoptotic cell count; however, nephron number at P10 was not affected. HIF-1α expression in the developing kidney was significantly reduced following hyperoxia exposure. Systemic administration of the HIF-1α stabilizer dimethyloxalylglycine (DMOG) resulted in enhanced expression of HIF-1α and improved nephrogenesis: kidneys from hyperoxia-exposed pups treated with DMOG exhibited a nephrogenic zone width and glomerular diameter similar to room-air controls. These findings demonstrate that neonatal hyperoxia exposure results in impaired nephrogenesis, which may be at least in part HIF-1α-mediated. Although nephron number was not significantly reduced at the completion of nephrogenesis, early indicators of maldevelopment suggest the potential for accelerated nephron loss in adulthood. Overall, this study supports the premise that prematurely born neonates exposed to high oxygen levels after birth are vulnerable to impaired renal development.

Renal parenchymal thickness as a measure of renal growth in low-birth-weight infants versus normal-birth-weight infants

Low birth weight (LBW, <2500 g) infants have a reduced number of glomeruli and nephrons and, therefore, smaller kidneys. The purpose of this pilot study was to determine whether renal parenchymal thickness might be a better indicator of renal growth. We carried out a pilot study over 12 mo to determine whether renal parenchymal thickness could be used to detect differences in renal growth between LBW and normal birth weight (NBW, 2500-4500 g) infants. Thirty-eight term infants (12 LBW and 26 NBW) underwent renal ultrasound. Parenchymal thickness, length, transverse diameter and antero-posterior diameter were measured. Mean renal parenchymal thickness was significantly lower in LBW infants than in NBW infants. Renal parenchymal thickness was closely correlated with an increase in renal volume (r = 0.76, p < 0.0001). Renal parenchymal thickness is a single measurement that could potentially be a more useful and accurate approach to monitoring renal growth in growth-restricted infants than renal volume.