Low birth weight and kidney function: is there a relationship and is it determined by the intrauterine environment?

Hypertension in children with congenital anomalies of the kidney and urinary tract

BACKGROUND

Congenital anomalies of the kidney and urinary tract (CAKUT) are the most common cause of childhood chronic kidney disease (CKD). We hypothesized that hypertension varies across CAKUT categories and increases the risk of CKD.

METHODS

This was a retrospective cohort study and included cases with a multicystic dysplastic kidney (MCDK, n = 81), unilateral kidney agenesis (UKA, n = 47), kidney hypoplasia (KH, n = 130), and posterior urethral valves (PUV, n = 75). Hypertension was defined as systolic or diastolic blood pressure ≥ 95th percentile for age, sex and height, and CKD as an estimated glomerular filtration rate < 60 ml/min/1.73 m2, both at 2 consecutive clinic visits at least 3 months apart.

RESULTS

Sixty-two (19%) out of 333 cases developed hypertension, with significant difference according to CAKUT type. Patients with smaller kidney size (7.7 vs. 8.3, p = 0.045), kidney anomalies in addition to the primary diagnosis (aCAKUT) (53 vs. 38%, p = 0.03), proteinuria (46 vs. 12%, p < 0.001), and CKD (51 vs. 23%, p < 0.001) were more likely to develop hypertension. When adjusted for kidney size, the diagnoses of PUV (OR 10.9, 95%CI 3.0, 40.5), UKA (OR 6.4, 95%CI 1.6, 24.9) and KH (OR 4.2, 95%CI 1.1, 16.1), and aCAKUT (OR 2.1, 95%CI 1.2, 3.9) were independent risk factors for hypertension. Hypertension increased the risk of developing CKD by twofold (HR 1.9, 95%CI 1.19, 2.94).

CONCLUSION

Hypertension is common in children with CAKUT and increases the risk of CKD. These findings will aid in the development of a standardized clinical pathway for the care of hypertensive children with CAKUT.

When will the Glomerular Filtration Rate in Former Preterm Neonates Catch up with Their Term Peers?

AIMS

Whether and when glomerular filtration rate (GFR) in preterms catches up with term peers is unknown. This study aims to develop a GFR maturation model for (pre)term-born individuals from birth to 18 years of age. Secondarily, the function is applied to data of different renally excreted drugs.

METHODS

We combined published inulin clearance values and serum creatinine (Scr) concentrations in (pre)term born individuals throughout childhood. Inulin clearance was assumed to be equal to GFR, and Scr to reflect creatinine synthesis rate/GFR. We developed a GFR function consisting of GFRbirth (GFR at birth), and an Emax model dependent on PNA (with GFRmax, PNA50 (PNA at which half ofGFR max is reached) and Hill coefficient). The final GFR model was applied to predict gentamicin, tobramycin and vancomycin concentrations.

RESULT

In the GFR model, GFRbirth varied with birthweight linearly while in the PNA-based Emax equation, GA was the best covariate for PNA50, and current weight for GFRmax. The final model showed that for a child born at 26 weeks GA, absolute GFR is 18%, 63%, 80%, 92% and 96% of the GFR of a child born at 40 weeks GA at 1 month, 6 months, 1 year, 3 years and 12 years, respectively. PopPK models with the GFR maturation equations predicted concentrations of renally cleared antibiotics across (pre)term-born neonates until 18 years well.

CONCLUSIONS

GFR of preterm individuals catches up with term peers at around three years of age, implying reduced dosages of renally cleared drugs should be considered below this age.

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.

Association of preterm birth and small for gestational age with metabolic outcomes in children and adolescents: A population-based cohort study from Taiwan

BACKGROUND

Previous studies have identified preterm birth and/or small for gestational age (SGA) as risk factors for features of the metabolic syndrome, including high blood pressure, insulin sensitivity and atherosclerosis, occurring later in life, with controversial results. We conducted this population-based cohort study to investigate metabolic outcomes in those with former preterm birth and/or SGA status in Taiwan.

METHODS

Data were obtained from Taiwan's universal National Health Insurance Research Database. From 1996 to 2004, 37,119 preterm infants, 3386 SGA infants, and 162,020 matched controls were included. We investigated the risk of the metabolic disease, including hypertension, diabetes, and hyperlipidemia, which had been recorded by the end of 2008.

RESULTS

The preterm and SGA cohort, combined into one, had a significantly increased risk of developing metabolic disorders when compared with the comparison cohort (HR = 2.46, 95% CI = 2.02-3.01). We observed that children with former preterm and SGA status in Taiwan had a higher risk of developing hypertension (HR = 3.24, 95% CI = 1.58-6.67), Type 1 diabetes mellitus (HR = 1.80, 95% CI = 1.05-3.07), Type 2 diabetes mellitus (HR = 2.49, 95% CI = 1.98-3.14), and hyperlipidemia (HR = 2.14, 95% CI = 1.29-3.52).

CONCLUSION

Our study revealed the risk of metabolic disease in those with preterm birth and/or SGA. Further studies with a longer duration of follow-up are required to confirm if there is a tendency for the metabolic syndrome to develop in this study cohort.

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.

Evolution of the urinary proteome during human renal development and maturation: variations with gestational and postnatal age

BACKGROUND

Low birth weight is associated with deficits in nephron number in the infant kidney and increased risk of adulthood hypertension and renal dysfunction. Urinary biomarkers may be potential indicators of renal reserve, but little is known about the influence of gestational and postnatal age on the expression of urinary proteins. The aims of this study were to determine the relationships between selected urinary proteins and renal maturation. We hypothesized that urinary protein patterns would change over time during late nephrogenesis and renal maturation.

METHODS

Urine samples were collected at birth and over 12 mo from preterm (33-35 wk) and term (38-40 wk) infants. Candidate urinary proteins were identified by antibody array and quantified with enzyme-linked immunosorbent assay.

RESULTS

Preterm infants at birth were found to have relatively elevated levels of insulin-like growth factor binding protein-1, -2, and -6, monocyte chemotactic protein-1, CD14, and sialic acid-binding Ig-like lectin 5. These markers gradually decline to levels similar to those of full-term infants by 2-6 mo of life. In contrast, many urinary markers in healthy full-term infants remain stable over the first year of life.

CONCLUSION

Gestational and postnatal age must be considered when evaluating the utility of urinary biomarkers.

Renal function and volume of infants born with a very low birth-weight: a preliminary cross-sectional study

AIM

The aim of our study was to compare the function and volumes of kidneys of very low birth-weight (VLBW) and of extremely low birth-weight (ELBW) infants at pre-school ages.

PATIENTS AND METHODS

We did a revision of the neonatal records of infants born in our hospital that weighed < or =1500 g at birth. The children were divided into two groups according to their weight at birth: ELBW (<1000 g) and VLBW (1000-1500 g). At the age of 5.7 +/- 1.4 years, the children underwent clinical, laboratory and ultrasound renal assessments.

RESULTS

Sixty-nine children fulfilled the requirements for the study. The rate of neonatal treatment with aminoglycosides was higher in ELBW preterms. Renal function parameters, i.e. estimated glomerular filtration rate and albuminuria, did not differ between the two groups of children. Urinary alpha1-microglobulin excretion was significantly higher and kidneys were significantly smaller in the ELBW group than in the VLBW group.

CONCLUSION

No impairment or differences in renal parameters were found in pre-school children born ELBW compared with those born with VLBW, except for differences in kidney volume, renal cortical thickness and urinary alpha1-microglobulin excretion. Thus, patients born with ELBW would require a longer follow-up period.

Early detection of microalbuminuria and hypertension in children of very low birthweight

OBJECTIVE

We retrospectively investigated a cohort of very low birthweight infants (VLBWI) by comparing two methods for assessment of albuminuria: nephelometry (standard) and high performance liquid chromatography (HPLC), measuring urinary immunoreactive and non-immunoreactive albumin to evaluate if the latter is more sensitive in identifying childhood onset of albuminuria and hypertension in VLBWI individuals.

METHODS

Spot urine samples of a total of 109 subjects (5.3 +/- 2.2 years old) who were VLBWI were investigated by HPLC and nephelometry. Twenty-eight subjects were small for gestational age (SGA) and 81 were appropriate for gestational age (AGA). Blood Pressure (BP) was also recorded.

RESULTS

Twelve children (11%) with albuminuria 20 mg/g Cr by nephelometry versus 48 (44.5%) by HPLC (p < 0.001) were identified. The mean +/- SD of values in the range of normoalbuminuria was 2.9 +/- 5.81 by nephelometry versus 22.6 +/- 14 for HPLC (p < 0.001). The values were not statistically different in the two birthweight categories (<1000, 1000-1499 g), in AGA versus SGA and in high BP (>90th percentile) versus normal BP children.

CONCLUSIONS

Microalbuminuria by HPLC was more marked in VLBWI than in adults and the difference between values using the two methods was significative.

Birth weight [corrected] and elevated albumin to creatinine ratio in youth with diabetes: the SEARCH for Diabetes in Youth study

Low birth weight (BWT) may contribute to kidney disease and could explain some of the variance in the development of early diabetic kidney disease. This hypothesis was tested in the multicenter SEARCH study (3,714 youth with diabetes <20 years of age). A morning spot urine sample, laboratory and anthropometric data, and a medical history were obtained. Elevated albumin to creatinine ratio (ACR) was defined as > or =30 mcg albumin/mg creatinine, and BWT was categorized as low (<2,500 g), reference (2,500-4,000 g), or high (>4,000 g). The relationship of BWT to elevated ACR was analyzed using multiple logistic regression. In youth with diabetes, the prevalence of elevated ACR was 12.6% in those with low BWT, 9.7% in those with reference BWT, and 8.9% in those with high BWT. BWT category was not significantly associated with elevated ACR (p = 0.23). Those with diabetes duration >18 months (2,032) had the following association of BWT category with elevated ACR [odds ratio (OR) = 1.64, 95% confidence interval (CI) 1.00-2.69, p = 0.0503] for low BWT compared with reference BWT. Whereas low BWT may be a factor in kidney disease, little evidence was found of a relationship between low BWT and elevated ACR in this study population of youth with diabetes.