Study of renal metabolic disturbances related to renal lithiasis at school age in very-low-birth-weight children

Programmed Adult Kidney Disease: Importance of Fetal Environment

The Barker hypothesis strongly supported the influence of fetal environment on the development of chronic diseases in later life. Multiple experimental and human studies have identified that the deleterious effect of fetal programming commonly leads to alterations in renal development. The interplay between environmental insults and fetal genome can induce epigenetic changes and lead to alterations in the expression of renal phenotype. In this review, we have explored the renal development and its functions, while focusing on the epigenetic findings and functional aspects of the renin-angiotensin system and its components.

Albuminuria and sodiuria in IUGR children

OBJECTIVE

Intrauterine growth restriction (IUGR) is associated with hyperfiltration, glomerulosclerosis and albuminuria. Albuminuria may further lead to tubulointerstitial inflammation, fibrosis and tubular atrophy. The time at which this may occur is unknown. This study was designed to assess the relationship between glomerular and tubular damage in IUGR children.

METHODS

We enrolled 50 children, 25 IUGR, categorized by estimated fetal weight <10th percentile and umbilical artery pulsatility index >2 SD, and 25 appropriate for gestational age (AGA) controls at 18 months of age. We compared albuminuria among IUGR and AGA children, to assess the relationship between albuminuria and contemporary sodium and lysozyme excretion, as a measure of tubular damage.

RESULTS

The albumin-creatinine (mg/g) and sodium-creatinine (μM/L) ratios (3.12 and 441.3, versus 1.39 and 226.1 in AGA; p = 0.002 and p = 0.012, respectively) were significantly higher in the IUGR subjects compared with AGA children, and significantly correlated (rho = 0.593, p = 0.002). Conversely, urinary lysozyme was undetectable or in normal excretion range.

CONCLUSIONS

Our results show glomerulosclerosis and albuminuria in IUGR children aged 18 months. Elevated sodium excretion in the absence of abnormal lysozymuria may represent a epiphenomenon of glomerulosclerosis and of albuminuria.

Influence of birth weight on the renal development and kidney diseases in adulthood: experimental and clinical evidence

Several clinical and experimental studies support the hypothesis that foetal programming is an important determinant of nephropathy, hypertension, coronary heart disease, and type 2 diabetes during adulthood. In this paper, the renal repercussions of foetal programming are emphasised, and the physiopathological mechanisms are discussed. The programming of renal diseases is detailed based on the findings of kidney development and functional parameters.

Ambulatory blood pressure monitoring and renal functions in term small-for-gestational age children

The aim of this study was to investigate the relationship between birth weight and blood pressure (BP) by means of ambulatory BP monitoring (ABPM) and renal functions in non-obese children who were born small-for-gestational age (SGA) at term. The study group consisted of 39 (19 female, 20 male; mean age 8.8 ± 2.6 years) children born SGA. Their data were compared to those of 27 (13 female, 14 male; mean age 8.2 ± 2.9 years) children born appropriate-for-gestational age (AGA). No difference between SGA and AGA children was observed based on office BP measurements and daytime, nighttime and 24-h ABPM. Seventeen SGA (48.6%) and nine AGA (37.5%) children had a 24-h systolic BP (SBP) load over 25%, and seven of these (5 SGA, 2 AGA) were hypertensive according to mean SBP values. The prevalence of the non-dipping phenomenon in SGA and AGA children was similar. Renal functions were normal and similar in both groups. Three children (2 SGA, 1 AGA) with normal glomerular filtration rate had higher microalbumin excretion and one SGA child had systolic hypertension according to the office BP. Our findings demonstrate that the influence of intrauterine growth restriction on BP is not manifested during the childhood period, and they do not support the existence of a negative relationship between birth weight and BP in children.

GFR estimated from cystatin C versus creatinine in children born small for gestational age

BACKGROUND

Low birth weight caused by intrauterine growth restriction may be a risk factor for renal impairment in the adult life.

STUDY DESIGN

A cross-sectional study.

SETTING & PARTICIPANTS

71 children aged 8 to 13 years living in the community of São Paulo, Brazil, were included in the study. Gestational age was within the normal range.

PREDICTORS

Birth weight (range, 2,052 to 3,560 g) divided into quartiles: 2,500 g or less; 2,501 to 2,740 g; 2,741 to 3,000 g; and greater than 3,000 g. Birth weight ascertained by birth records in 43 and by recall in 28 participants.

OUTCOMES & MEASUREMENTS

Cystatin C, creatinine, and glomerular filtration rate (GFR) estimated by equations using cystatin C (eGFR(cys)) or creatinine (eGFR(cr)).

RESULTS

Overall, mean serum creatinine level was 0.8 +/- 0.01 (SE) mg/dL (range, 0.7 to 1.1 mg/dL); mean plasma cystatin C level was 0.9 +/- 0.02 mg/L (range, 0.5 to 1.6 mg/L), and eGFR(cr) and eGFR(cys) were 102.4 +/- 2.16 (range, 66 to 140) and 91.8 +/- 2.46 mL/min/1.73 m(2) (range, 49 to 139 mL/min/1.73 m(2)), respectively. No differences were found for serum creatinine or eGFR(cr) values among the birth-weight quartiles. There was a significant linear trend of increasing cystatin C levels (decreasing eGFR(cys)) in the lower birth-weight quartile groups (P = 0.002 and P = 0.02, respectively). Systolic blood pressure correlated with plasma cystatin C level (r = 0.31; P = 0.008) and eGFR(cys) (r = -0.26; P = 0.028). Covariance analysis adjusting for age, sex, body mass index for age compared with standards of the National Center for Health Statistics and expressed as a z score, and systolic blood pressure showed that cystatin C values remained greater in the lowest than highest birth-weight quartile (1.01 +/- 0.05 versus 0.83 +/- 0.05 mg/L; P = 0.02).

LIMITATIONS

Ascertainment of birth weight by recall in some participants. Lack of measurement of microalbuminuria, absence of direct GFR measurement, and small sample size.

CONCLUSIONS

Lower birth weight is associated with higher levels of cystatin C but not creatinine in 8-13 yr. old children born full-term.

Aetiological factors in paediatric urolithiasis

The aetiology of stones in children differs from that in adults. Young children, especially boys, are prone to infective stones, although this type of calculi is decreasing in frequency over time in prosperous countries. Two monogenic causes, cystinuria and hyperoxaluria, each account for 5-15% of paediatric stones. Increased factors for stone formation in children include prematurity, neurological problems, ketogenic diet and reconstructed or augmented bladders. Hypercalciuria is commonly found in paediatric stone formers, is usually idiopathic and is only rarely associated with hypercalcaemia. All children with stones should undergo a metabolic evaluation.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSION

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

Long-term renal follow-up of extremely low birth weight infants

There is evidence that low birth weight caused by intrauterine growth retardation adversely affects normal renal development. Very little information on this issue is available on children born very prematurely. This investigation examined clinical and functional renal parameters in 40 children (23 boys, 17 girls) ranging in age between 6.1 and 12.4 years and weighing less than 1000 g at birth. Results were compared to those obtained in 43 healthy children of similar age and gender. Study subjects were significantly smaller and thinner than control subjects (mean height SDS: -0.36 vs. +0.70; and mean BMI SDS: -0.56 vs. +1.18). Systolic, diastolic, and mean blood pressures did not differ from those of controls. Renal sonography revealed no abnormality, and mean percentiles for renal length and volume appeared normal. In comparison with controls, plasma creatinine concentration (0.62+/-0.1 vs. 0.53+/-0.1 mg/dl) and estimated creatinine clearance (117+/-17 vs. 131+/-17 ml min(-1) 1.73 m(-2)) differed significantly. No significant differences were observed in microalbuminuria values, but five study subjects (12.5%) presented values above the upper limit of normality. A defect in tubular phosphate transport was also evident: TmP/GFR (3.6+/-0.4 vs. 4.2+/-0.8 mg/dl) and TRP (83+/-5% vs. 90+/-4%) were significantly lower, and urinary P excretion, estimated by the ratio UP/UCr, was significantly higher (1.2+/-0.4 vs. 0.9+/-0.4 mg/mg) than controls. Urinary calcium excretion, estimated by the UCa/UCr ratio, was also significantly higher (0.15+/-0.07 vs. 0.12+/-0.09 mg/mg). These data clearly demonstrate that both GFR and tubular phosphate transport are significantly diminished in school-age children born with extreme prematurity, probably as a consequence of impaired postnatal nephrogenesis.

Birth weight and renal function

Low birth weight due to premature birth or to intrauterine growth retardation adversely affects normal renal development. In the period immediately after birth, the short-term renal-related consequences of low birth weight are an increased risk of acute renal failure as well as transient imbalance of fluid and electrolyte homeostasis. Epidemiological studies show that low birth weight adults are at risk of developing chronic renal disease. There are thought to be several causes for this phenomenon. Adult low birth weight subjects have an increased incidence of hypertension and type 2 diabetes, both of which are well-established risk factors for chronic renal injury. Moreover, interference with normal kidney development, as seen in low birth weight babies, results in a lower than normal number of nephrons, which might also play a role in the renal disturbances.

A new dimension to the Barker hypothesis: low birthweight and susceptibility to renal disease

BACKGROUND

There is an epidemic of renal failure among Aborigines in the Australia's Northern Territory. The incidence is more than 1000 per million, and is doubling every three to four years. We evaluated the relationship of birthweight to renal disease in adults in one high-risk community.

METHODS

We screened more than 80% of people in the community for renal disease, using the urine albumin/creatinine ratio (ACR, g/mol) as the marker, and reviewed records for birthweights.

RESULTS

Birthweights were available with increasing frequency for people born after 1956. In 317 adults aged 20 to 38 years at screening, the mean birthweight (SD) was 2.712+/-0.4 kg, and 35% had been low birthweight (LBW, less than 2.5 kg). Birthweight was positively correlated with body mass index (BMI), blood pressure, and diabetes rates, but was inversely correlated with ACR. The odds ratio for overt albuminuria in LBW persons compared with those of higher birthweights was 2.82 (CI, 1.26 to 6.31) after adjusting for other factors, and LBW contributed to an estimated 27% (CI, 3 to 45%) of the population-based prevalence of overt albuminuria. Multivariate models suggest that increasing BMI and blood pressure and decreasing birthweight act in concert to amplify the increases in ACR that accompany increasing age.

CONCLUSIONS

LBW contributes to renal disease in this high-risk population. The association might be mediated through impaired nephrogenesis caused by intrauterine malnutrition. The renal disease epidemic in Aborigines may partly be the legacy of greatly improved survival of LBW babies over the last four decades. Disease rates should eventually plateau as birthweights continue to improve, if postnatal risk factors can also be contained.