[Long term renal outcome of children born preterm: a regular follow-up is needed]

Small for date preterm infants and risk of higher blood pressure in later life: A systematic review and meta-analysis

BACKGROUND

Historical reports suggest that infants born small for gestational age (SGA) are at increased risk for high blood pressure (BP) at older ages after adjustment for later age body size. Such adjustment may be inappropriate since adiposity is a known cause of cardiovascular and metabolic disease.

OBJECTIVES

To assess the association between SGA births and later BP among preterm births, considering potential background confounders and over-adjustment for later body size.

METHODS

A database search of studies up to October 2022 included MEDLINE, EMBASE and CINAHL. Studies were included if they reported BP (systolic [SBP] or diastolic [DBP]) (outcomes) for participants born preterm with SGA (exposure) or non-SGA births. All screening, extraction steps, and risk of bias (using the Risk of Bias In Non-randomised Studies of Interventions [ROBINS-I] tool) were conducted in duplicate by two reviewers. Data were pooled in meta-analysis using random-effects models. We explored potential sources of heterogeneity.

RESULTS

We found no meaningful difference in later BP between preterm infants with and without SGA status at birth. Meta-analysis of 25 studies showed that preterm SGA, compared to preterm non-SGA, was not associated with higher BP at age 2 and older with mean differences for SBP 0.01 mmHg (95% CI -0.10, 0.12, I²  = 59.8%, n = 20,462) and DBP 0.01 mm Hg (95% CI -0.10, 0.12), 22 studies, (I²  = 53.0%, n = 20,182). Adjustment for current weight did not alter the results, which could be due to the lack of differences in later weight status in most of the included studies. The included studies were rated to be at risk of bias due to potential residual confounding, with a low risk of bias in other domains.

CONCLUSIONS

Evidence indicates that preterm infants born SGA are not at increased risk of developing higher BP as children or as adults as compared to non-SGA preterm infants.

Nephrocalcinosis in very low birth weight infants: incidence, associated factors, and natural course

BACKGROUND

Preterm kidney is exposed to various exogenous factors that may impact its function such as nephrotoxic drugs or nephrocalcinosis. We investigated prevalence and risk factors of nephrocalcinosis (NC) in recently born very low birth weight (VLBW) infants submitted to improved biological monitoring.

METHODS

Retrospective, case-control study in very preterm infants (< 32 + 6 weeks, ≤ 1500 g) admitted to a tertiary care unit during a 6-year period. Each case (ultrasound-diagnosed NC) was matched with two controls (no NC). Data were collected at days 15 and 30 of life and 35 weeks corrected age, with follow-up at 18 months and 3 years.

RESULTS

Of 525 eligible infants, overall prevalence of NC was 17.1% at 35 weeks corrected age. Prevalence was halved between 2012 (26.1%) and 2017 (11.8%). We included 265 infants, more than half being born before 28 weeks. Cases presented with more severe morbidity than controls, but reached statistical significance only in infants born < 28 weeks (88.2% vs. 68.3%, P = 0.01). Protein, energy, calcium, phosphorus, and vitamin D intakes were similar in the two groups and did not change significantly over the study period. Weight gain was similar in the two groups. Exposure to furosemide (OR [IC95%]: 1.26 [1.02; 1.57]) and postnatal growth (1.65 [1.04; 2.67]) were independent risk factors of NC. NC resolved 12-18 months after diagnosis in 61% of infants.

CONCLUSION

Prevalence of NC is significant but can be reduced. Furosemide should be cautiously prescribed in VLBW infants, and nutritional support must be well monitored to support postnatal growth and limit risk of nephrocalcinosis.

TRIAL REGISTRATION

ClinicalTrials.gov: NCT 04,860,583. A higher resolution version of the Graphical abstract is available as Supplementary information.

[Neonatal intoxication to vitamin D in premature babies: A series of 16 cases]

INTRODUCTION

Preterm neonates are particularly at risk of vitamin D (25-D) deficiency. To prevent rickets and osteopenia in this population, international guidelines vary between 800 and 1000IU per day of vitamin D in Europe and recommend 400IU per day in the USA. Target levels of circulating 25-D are not well identified, with the lower target level 50-75nmol/L and the upper target level probably 120nmol/L.

METHODS

Between 2013 and 2015, 16 premature infants (born<35WG) were referred to pediatric nephrology clinics because of symptoms secondary to 25-D overdose during the neonatal period. Clinical and biological data were retrospectively reviewed to better define this population. The results are presented as the median (range).

RESULTS

Gestational age was 27 (24-35)WG with a birth weight of 810 (560-2120)g. Nephrocalcinosis was the initial symptom in 37% of cases, hypercalcemia in 44%, and hypercalciuria in 19%. Daily vitamin D doses were 333 (35-676)IU. Age and body weight at initial symptom were 36.6 (27.6-47.6)WG and 2300 (640-3760)g, respectively. The 25-D level at the time of the first dosage was 210 (119-350)nmol/L and the 1-25 vitamin D level was 370 (245-718)pmol/L (local normal values for age<240). During follow-up, 12 patients displayed nephrocalcinosis, ten hypercalciuria, and three hypercalcemia. The 25-D level normalized in ten patients within 10 (3-32)months after vitamin D withdrawal. Nephrocalcinosis improved in ten of 12 patients, within 12 (3-30)months. Vitamin D could be readministered in ten patients. When searched (n=3), no CYP24A1 mutation was identified in two patients, but was identified in the heterozygous state in one.

CONCLUSION

A 25-D overdose should be systematically ruled out in the presence of nephrocalcinosis, hypercalcemia, and/or hypercalciuria during infancy in children born preterm. Studies are required to assess the exact frequency of 25-D deficiency and overdose in this population, as well as to evaluate the potential deleterious effects of this imbalance on bone, kidney, and brain development.

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.

Maternal determinants of renal mass and function in the fetus and neonate

The impact of adverse maternal and early gestational issues, ranging from maternal-fetal interactions all the way through to premature birth, are recognized as having influence on the subsequent development of chronic diseases later in life. The development of chronic kidney disease (CKD) as a direct result of early life renal injury or a sequela of diseases such as hypertension or diabetes is a good model example of the potential impact that early life events may have on renal development and lifelong function. The global monetary and human resource cost of CKD is exorbitant. Socio-economic factors, along with other factors (genetic and environmental) may significantly influence the timing and display of phenotypic expression in fetuses and neonates at risk for developing CKD, yet very few of these factors are studied or well understood. In general our focus has been directed at treatment once CKD is established. This strategy has been and remains short-sighted and costly. Earlier understanding of the intrauterine determinants of renal mass development (i.e. environmental "biomes", poor maternal-fetal health, socio-economic factors impacting early life events, diet, access to value based health care and educational opportunities on disease evolution) may allow us an opportunity for earlier intervention. This article aims to provide some foundation for improved understanding of the maternal determinants of renal mass and function in the fetus and neonate.

Early-life course socioeconomic factors and chronic kidney disease

Kidney failure or ESRD affects approximately 650,000 Americans, whereas the number with earlier stages of CKD is much higher. Although CKD and ESRD are usually associated with adulthood, it is likely that the initial stages of CKD begin early in life. Many of these pathways are associated with low birth weight and disadvantaged socioeconomic status (SES) in childhood, translating childhood risk into later-life CKD and kidney failure. Social factors are thought to be fundamental causes of disease. Although the relationship between adult SES and CKD has been well established, the role of early childhood SES for CKD risk remains obscure. This review provides a rationale for examining the association between early-life SES and CKD. By collecting data on early-life SES and CKD, the interaction with other periods in the life course could also be studied, allowing for examination of whether SES trajectories (eg, poverty followed by affluence) or cumulative burden (eg, poverty at multiple time points) are more relevant to lifetime CKD risk.

A case of Fabry nephropathy with histological features of oligonephropathy

Newborn screening studies indicate the expected high incidence of later-onset Fabry disease with silent Fabry nephropathy while, with recent improved clinical care of premature infants, children with congenital oligonephropathy caused by premature embryonal development of the kidney are thought to be increasing. However, the coexistence of Fabry nephropathy and oligonephropathy has not been reported previously. We present the case of a 13-year-old boy who was diagnosed with Fabry nephropathy accompanied with histological features of oligonephropathy. He was born as a preterm baby, and a renal biopsy was performed because of mild renal dysfunction and mild proteinuria. He had neither characteristic early symptoms nor a family history of Fabry disease. Histologic findings demonstrated diffuse global enlargement and foamy change of podocytes with markedly decreased number and enlargement of the glomeruli. Both his plasma and leukocyte α-galactosidase A (GLA) activities were markedly decreased, and the plasma globotriaosylsphingosine and urine globotriaosylceramide levels were increased. Gene analysis revealed a missense mutation, R112H, in the GLA gene, which had been reported in the later-onset phenotype of Fabry patients. He is now under treatment with enzyme replacement therapy and an angiotensin-converting enzyme inhibitor.

CONCLUSION

This case indicated the possible co-occurrence of Fabry nephropathy and oligonephropathy. For early diagnosis and timely management, careful examinations for proteinuria and renal function, in addition to establishing an effective screening system for Fabry disease, will be necessary.

Ultrasonographic study of initial size and postnatal growth of kidneys in preterm infants

BACKGROUND

Preterm birth is known to be associated with risks of impaired nephrogenesis.

OBJECTIVES

To determine the normal range of renal sizes at birth in preterm infants as well as their short-term postnatal renal growth, to assess the correlation between initial renal size and growth parameters at birth and to compare the initial and serial renal sizes between appropriate-for-gestational-age (AGA) and small-for-gestational-age (SGA) preterm infants.

METHODS

Initial ultrasonography (US) was prospectively performed in 125 preterm infants within the first 72 h of life and every 2 weeks thereafter until a postmenstrual age (PMA) of 37 weeks was reached. Correlation between renal size and growth parameters was investigated. Renal lengths of AGA and SGA preterm infants were compared with those of age-matched fetuses described in the literature.

RESULTS

The renal sizes at birth in preterm infants are presented. Multiple regression analysis showed the strongest correlation between initial renal size and birth weight (p < 0.0001). Initial renal lengths of AGA infants were not significantly different from those of age-matched fetuses at ≥30 weeks' gestational age (GA), whereas those of SGA infants were significantly smaller at ≥28 weeks' GA. Serial renal lengths of SGA infants were significantly smaller than fetal renal lengths at ≥30 weeks' GA.

CONCLUSION

With US, the normal range of initial renal sizes of AGA preterm infants was defined according to GA. In contrast to AGA infants, SGA infants showed smaller initial renal sizes and no significant catch-up growth until a PMA of 37 weeks.

Proteinuria and progression of glomerular diseases

One of the major challenges of nephrology is to develop therapeutic strategies to halt the progression of kidney diseases. In clinical settings, nephrotic-range proteinuria correlates with the rate of progression, particularly in glomerular diseases. Hence, the degree of proteinuria has been utilized to monitor the response to treatment as well as to predict outcome. However, the pathophysiology of proteinuria-induced progression remains unknown. Albumin accounts for the majority of the protein in nephrotic urine and as a result of this clinical observation studies have focused on understanding the adverse effects of albumin overload in the kidney. Albumin is internalized by receptor-mediated endocytosis in proximal tubule cells via low density lipoprotein (LDL) type receptor, megalin. Albumin at high concentrations mimicking nephrotic milieu has resulted in the upregulation of pro-inflammatory/fibrogenic genes and apoptosis in proximal tubule cells in in vivo and in vitro models of albumin overload. These properties of albumin on proximal tubule cells may explain extensive tubulointerstitial fibrosis and tubular atrophy observed in end-stage kidney disease. In addition to tubular toxicity, podocytes respond to proteinuric states by cytoskeletal alterations and loss of the differentiation marker synaptopodin. Identifying the molecular network of proteins involved in albumin handling will enable us to manipulate the specific signaling pathways and prevent damage caused by proteinuria.

Extra-uterine renal growth in preterm infants: oligonephropathy and prematurity

BACKGROUND

Nephron number in humans is determined during fetal life. The objective of this study was to investigate the effects of preterm birth on nephron number using renal volume as a surrogate for nephron number.

METHODS

This observational study was conducted over 12 months in a tertiary perinatal center. Preterm babies less than 32 weeks of gestation were recruited and followed until discharge. Term infants were recruited for comparison. The babies underwent renal sonography and renal function measurements at 32 and 38 weeks corrected age. The primary outcome measurement was total kidney volume at 38 weeks and the secondary outcome was estimated glomerular filtration rate (eGFR).

RESULTS

Forty-four preterm infants and 24 term infants were recruited. At 38 weeks corrected age, premature infants had lower total kidney volume than term infants (21.6 ± 5.7 vs. 25.2 ± 5.7 ml; p = 0.02) and a significantly lower eGFR (73.6 [IQR 68.1-77.6] vs. 79.3 [IQR 72.5-86.6] ml·min(-1)·1.73 m(-2); p = 0.03). There was a significant correlation between total kidney volume and eGFR in premature and term babies.

CONCLUSIONS

Premature infants have smaller kidney volume and likely decreased nephron number and lower estimated glomerulofiltration rate relative to infants born at term.

[Idiopathic nephrotic syndrome in children: Incidence, clinical presentation, and outcome in the county of Gironde, France]

AIMS

To estimate the incidence and describe the clinical presentation and outcome (steroid responsiveness, clinical course, complications) of idiopathic nephrotic syndrome in children in a population-based retrospective study.

METHODS

Using local registries and the hospital discharge diagnosis system from two centers, all new cases of idiopathic nephrotic syndrome were identified in Gironde (France) between January 1992 and May 2008. To estimate incidence, population-based denominators were obtained from the National Institute for Statistics and Economic Studies (INSEE). Clinical data were collected from medical charts.

RESULTS

Ninety-nine cases of idiopathic nephrotic syndrome were reported (66 boys, 18 non-Caucasians) with an incidence of 2.3/100,000 (CI, 1.8-3.0) children less than 15 years. Ninety patients (91%) had steroid-sensitive nephrotic syndrome (SSNS) and nine (9%) were steroid-resistant (SRNS). The median time to remission in SSNS was 11 days. Relapses occurred in 75 (83%) children with SSNS with a median of four relapses (range, 1-32). The cumulative relapse-free incidence was 60% at 10 years after diagnosis in SSNS and 13% of patients aged 18 years old or over still had active disease. In SSNS, the only significant factor associated with steroid dependency or use of non steroid drugs was the time to initial response to steroids greater than 14 days. Nineteen children (19%) experienced severe complications of nephrotic syndrome including 11 bacterial infections and two thromboembolic complications. Two children with SRNS, of whom one was initially steroid-responsive, developed end-stage renal failure.

CONCLUSION

The incidence and outcome of idiopathic nephrotic syndrome in Gironde are comparable to the rates found in other studies. The disease may have a long course and the time for response to steroids at disease onset is the main predictor of steroid dependency and of use of non steroid agents.