Neonatal nephrocalcinosis: long term follow up

Nephrocalcinosis in Neonates

Nephrocalcinosis occurs in as many as 40% of preterm neonates. Many causes and contributors predispose neonates to develop nephrocalcinosis, including metabolic, genetic, and iatrogenic factors. Because nephrocalcinosis can be a manifestation of an underlying genetic disorder, neonates with nephrocalcinosis must undergo an evaluation to identify and address contributors, to prevent further renal calcium deposition that can potentially lead to renal dysfunction. In this article, we review the epidemiology, pathogenesis, diagnosis, and evaluation of nephrocalcinosis in neonates. We also summarize the natural history of nephrocalcinosis of prematurity as well as the management of this condition.

Clinical outcomes of nephrocalcinosis in preschool-age children: association between nephrocalcinosis improvement and long-term kidney function

Background

We evaluated the long-term clinical outcomes of nephrocalcinosis (NC) according to etiology and grade in preschool-age children with NC.

Methods

We retrospectively analyzed the clinical outcomes and disease grade of children with NC classified into three groups according to etiology: prematurity, tubular disorders, and others.

Results

Overall, 67 children were diagnosed with NC [median age, 0.76 years; interquartile range (IQR) 0.46-2.14 years]. The etiologies of NC included prematurity (28.4%), tubular disorders (25.4%), and others (46.3%). Moreover, 56 (83.6%) children were asymptomatic and diagnosed accidentally through kidney ultrasonography. Newly diagnosed underlying diseases were greater in the tubular disorders group than in the other two groups (P = 0.001). Significantly more newly diagnosed NCs were grade 3 than grade 1 (P = 0.003). The median estimated glomerular filtration rate (eGFR) changed from 96.1 (IQR 68.8-119.2) ml/min/1.72 m2 at diagnosis to 90.9 (IQR 76.4-106.4) ml/min/1.72 m2 at the last follow-up, without a significant difference (P = 0.096). Changes in the kidney function did not differ according to etiology. However, patients without improvement in NC grade showed a decrease in eGFR from 98.1 (IQR 71.1-132.9) to 87.4 (IQR 74.0-104.1) ml/min/1.73 m2 (P = 0.023), while patients with improved NC grade did not show any change in the kidney function.

Conclusions

Early recognition, especially in NC grade 3, can help uncover further diagnoses, such as tubular disorders. Long-term kidney function depends on whether the NC grade improves.

Etiology and prognosis of nephrocalcinosis according to gestational age in Korean children

BACKGROUND

Nephrocalcinosis (NC) is defined as deposition of calcium in renal tubules and interstitium and is highly related with prematurity and monogenic diseases. Recent studies have reported that NC might be a specific finding of underlying hereditary renal diseases. This study evaluated the risk factors, underlying monogenic causes, and clinical outcomes of NC in Korean children according to gestational age (GA).

METHODS

A total of 464 patients younger than 18 years who were diagnosed with NC by ultrasonography from January 2013 to December 2022 in Samsung Medical Center were enrolled. Medical record data of sex, GA, birth weight, underlying disease, medication history, ultrasonography and genetic analysis were reviewed retrospectively.

RESULTS

The male to female ratio was 1:0.98, and the mean age at first diagnosis of NC was 385 days. Approximately 62% of patients experienced confirmed resolution of NC after about one year. In comparison of the preterm (mean GA 28 weeks and 2 days) and full-term (mean GA 38 weeks and 2 days) groups, bronchopulmonary dysplasia, patent ductus arteriosus, and use of furosemide and vitamin D were more frequent in the preterm group. In the full-term group, a larger proportion of cases showed persistent NC without resolution and chronic kidney disease (CKD). Genetic analyses were performed in 56 patients, and the monogenic mutation rate was significantly higher in full-term children (OR 10.02, 95% CI [2.464-40.786], p = 0.001).

CONCLUSION

While the overall outcomes of pediatric NC are favorable, underlying monogenic causes should be studied, especially in full-term patients without known clinical risk factors.

Vitamin D, bone density, and nephrocalcinosis in preterm infants: a prospective study

BACKGROUND

Vitamin D (VitD) supplementation is recommended by the American Academy of Pediatrics (AAP) for preterm infants to improve bone density. Complications of VitD supplementation include hypercalciuria and nephrocalcinosis (NC). NC has been reported in 7-64% infants < 32 weeks gestational age (GA) or < 1500 g birth weight (BW). The relationships between VitD supplementation, serum 25-hydroxy VitD levels, bone density, hypercalciuria and development of NC in preterm infants are not well established.

METHODS

Prospective, observational cohort study of 56 infants with GA ≤ 32 weeks or BW ≤ 1800 g. Demographics, dietary intakes, serum 25-hydroxy VitD levels and weekly urinalyses were collected until 40 weeks corrected GA or discharge. Bone mineral density (BMD) and content (BMC) were assessed using dual-energy X-ray absorptiometry (DEXA) scan. NC was identified by kidney ultrasound.

RESULTS

56 infants received on average 447 IU/day of VitD with average serum 25-hydoxy VitD level 39.6 ng/mL. DEXA scan showed average BMD 0.13 g/cm² and BMC 35.8 g. 23/56 (41%) infants were diagnosed with NC. Infants with NC had lower GA (p < 0.01) and BW (p < 0.01) and increased presence of calcium oxalate crystals (78% vs. 36%) (p = 0.002). There were no differences in VitD intake, urine calcium/creatinine ratios or BMD and BMC in infants with versus without NC.

CONCLUSIONS

VitD supplementation per AAP guidelines resulted in acceptable serum 25-hydroxyVitD levels, but no improvement in BMD or BMC compared to previously reported values. However, infants receiving recommended amounts born at earlier GA and lower BW are at increased risk of NC. VitD supplementation and serum levels should be closely monitored in this high-risk population. A higher resolution version of the Graphical abstract is available as Supplementary information.

Neurodevelopmental disorders and somatic diagnoses in a national cohort of children born before 24 weeks of gestation

AIM

This study investigated childhood diagnoses in children born extremely preterm before 24 weeks of gestation.

METHODS

Diagnoses of neurodevelopmental disorders and selected somatic diagnoses were retrospectively retrieved from national Swedish registries for children born before 24 weeks from 2007 to 2018. Their individual medical files were also examined.

RESULTS

We studied 383 children born at a median of 23.3 (range 21.9-23.9) weeks, with a median birthweight of 565 (range 340-874) grams. Three-quarters (75%) had neurodevelopmental disorders, including speech disorders (52%), intellectual disabilities (40%), attention deficit hyperactivity disorder (30%), autism spectrum disorders (24%), visual impairment (22%), cerebral palsy (17%), epilepsy (10%) and hearing impairment (5%). More boys than girls born at 23 weeks had intellectual disabilities (45% vs. 27%, p < 0.01) and visual impairment (25% vs. 14%, p < 0.01). Just over half of the cohort (55%) received habilitation care. The majority (88%) had somatic diagnoses, including asthma (63%) and failure to thrive/short stature (39%).

CONCLUSION

Most children born before 24 weeks had neurodevelopmental disorders and/or additional somatic diagnoses in childhood and were referred to habilitation services. Clinicians should be aware of the multiple health and developmental problems affecting these children. Resources are needed to identify their long-term support needs at an early stage.

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.

Effects of prematurity on long-term renal health: a systematic review

OBJECTIVE

To investigate the literature and determine if prematurity has an impact on long-term adverse kidney outcomes.

DESIGN

Systematic review.

DATA SOURCES

OVID Medline, PubMed, SCOPUS, CINAHL and EMBASE databases were searched for studies relating to the adverse outcomes of prematurity from 1990 to April 2021.

ELIGIBILITY CRITERIA FOR SELECTING STUDIES

All articles published between January 1990 and April 2021 that investigated whether premature infants developed long-term adverse renal outcomes were included in this review. Articles must have been human studies and written in English. Case series with less than 20 participants and case studies were excluded.

DATA EXTRACTION AND SYNTHESIS

One reviewer completed the database searches. Article selection was performed independently and in a non-blinded manner by both reviewers. Initial screening was by title and abstract. Full texts of remaining articles were reviewed. Articles for which inclusion was unclear were re-reviewed by both reviewers, and a unanimous decision was taken as to whether they should be included. The Newcastle-Ottawa Scale was used for quality assessment of the included articles.

RESULTS

The literature search yielded 31 human studies, which investigated the short-term and long-term kidney outcomes of prematurity. These studies were conducted in 17 different countries. The most common outcomes measured were blood pressure (BP) and glomerular filtration rate. Other common outcomes measured included kidney size and mass, proteinuria, albuminuria, chronic kidney disease (CKD) and physical parameters such as height, weight and body mass index.

CONCLUSION

Prematurity is likely linked to increased risk of kidney dysfunction and high BP in childhood and into early adulthood. Premature birth conferred a twofold increased risk of CKD and extremely premature birth conferred a threefold increased risk of CKD. However, further larger multicentre studies are needed to draw definitive conclusions on the long-term kidney outcomes of prematurity.

[Nephrocalcinosis in children]

Nephrocalcinosis is defined by calcium phosphate or calcium oxalate deposits in the kidney parenchyma, particularly in tubular epithelial cells and interstitial tissue. It should be differentiated from urolithiasis where calcium salts deposits are located in the kidney and urinary tract. The epidemiology of nephrocalcinosis in children is unknown but the condition is not so rare, with an increased incidence in preterm infants. Often detected as an incidental finding, nephrocalcinosis may be classified according to the radiological type: medullary, cortical or diffuse. Nephrocalcinosis in children can be caused by a variety of etiology. The most common causes concern medullary nephrocalcinosis and include hereditary tubular disorders, in particular distal renal tubular acidosis and Dent disease, metabolic disorders such as idiopathic hypercalciuria and hyperoxaluria, and iatrogenic causes such as vitamin D intoxication. In the newborn, the main cause is hypercalciuria of the premature baby, whose multifactorial origin is largely iatrogenic. Primary hyperoxaluria which can lead to early onset nephrocalcinosis and usually to chronic kidney disease should always be considered and further investigated. In order to provide a specific diagnosis, it is essential to take into account the family history, the clinical context and complete laboratory data. Early initiation of an appropriate etiological treatment is recommended and may prevent or delay the progression to chronic kidney disease in some cases.

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.

Acute kidney injury in an extremely low birth weight infant with nephrolithiasis: a case report

Acute kidney injury is associated with mortality of very low birth weight infants and reduces their survival regardless of other factors. The kidneys in the extremely preterm infants are very immature and susceptible to environmental factors. Clinical conditions and medications are risk factors for acute kidney injury in these patients. Nephrolithiasis in preterm infants is an extremely rare phenomenon that usually manifests as a complication of nephrocalcinosis.

This is a case report that describes several episodes of acute kidney injury in the first two months of age in an extremely low birth weight infant with kidney stones in the background. The main causes that led to acute kidney injury in this patient were persistent ductus arteriosus, sepsis and captopril. At one month of age, ultrasound detected calcinates in the right kidney. Within two weeks a large number of linear stones formed across the collecting duct system. Small calcinates still remained in the right kidney when the girl was half a year of the corrected age.

The evaluation of a neonate who develops acute kidney injury requires a systematic approach. Early identification of the emerging risk factors and prevention of nephrolithiasis along with effective treatment can reduce the risk of developing acute kidney injury in very low birth weight infants.

Ultrasound Imaging of the Renal Parenchyma of Premature Neonates for the Assessment of Renal Growth and Glomerulomegaly

Evidence is increasingly showing that prematurity results in chronic kidney disease. We hypothesized that we could use ultrasound imaging to measure and monitor the growth of the renal parenchyma in premature neonates. We conducted a prospective, case-control study to compare renal parenchymal growth between neonates born prematurely and term neonates. The study patients underwent ultrasound assessment at 32 wk postmenstrual age (PMA) and 37 wk PMA. Term neonates (gestation >37 completed wk) admitted to the neonatal unit with minor neonatal conditions were recruited into the control group. Complete data sets were available in 91 premature neonates and during the same period, 56 term neonates were recruited as the control. The median birth weight (preterm babies) was 930 g (780-1220 g), and the mean gestational age was 27.0 wk (2.1 wk). Total renal volume (TRV) increased from 14.6 (4.3) cm³ to 20.5 (5.3) cm³ from 32 to 37 wk PMA. During the same period, the total renal parenchyma (TRP) thickness increased from 1.6 (0.3) cm to 1.8 (0.3) cm. At 37 wk PMA, ex-premature neonates have a significantly smaller total renal volume (20.5 [5.3] versus 25.9 [6.4] cm³; p < 0.001) and total renal parenchyma thickness (1.8 [0.3] versus 2.0 [0.2] cm; p = 0.015) compared with term (control) neonates. However, premature neonates at 37 wk PMA have a larger TRP:TRV ratio compared with term neonates (0.09 [0.02] versus 0.0 8 [0.02] cm^-2; p < 0.001). Reduced nephron endowment as a result of prematurity may cause the remaining nephrons to undergo compensatory glomerulomegaly and we postulate this is the reason for the observed differences. Ultrasound imaging of the renal parenchyma shows promise in assessing the effects of prematurity on the developing kidney.

A case control analysis investigating risk factors and outcomes for nephrocalcinosis and renal calculi in neonates

INTRODUCTION

Studies on outcomes and risk factors for neonatal nephrocalcinosis (NC) and renal calculi (RC) are limited, and often do not include controls for comparison. We conducted a case-control analysis to identify risk factors associated with NC and/or RC in neonates and studied the natural course of these anomalies.

STUDY DESIGN

Infants diagnosed with NC/RC on ultrasound within the first year of life and corresponding gestational age- and gender-matched controls were identified from the neonatal intensive care unit database at our institution over a 10-year period. Risk factors assessed included: low birth weight, small for gestational age, nephrotoxic drugs, respiratory support therapy, use of total parental nutrition (TPN), surgeries, history of UTIs, creatinine at presentation, and history of maternal hypertension. Unadjusted odds ratios were estimated. Chi square analysis was performed for binary variables and the Mann-Whitney U test for continuous variables. Outcomes examined include time to resolution of NC/RC, renal function, and hypertension.

RESULTS

We identified 22 cases of NC/RC with corresponding matched controls. Median follow-up was 28 months (IQR 0-122 months). History of urinary tract infections (UTI) was the only variable significantly associated with the presence of NC/RC (OR 5.62, 95% CI 1.12-31.1, p < 0.013) (Table). All other known risk factors were comparable in both groups. There was no difference in the incidence of hypertension (OR 2.94, 95% CI 0.40-33.82, p = 0.216) at diagnosis or last follow-up between the groups. Resolution of NC/RC was observed in 72.7%, during a median follow-up of 12.1 months. Mean urinary calcium/creatinine ratio for the NC/RC group was 2.3 ± 1.5 at diagnosis and 0.96 ± 0.8 at last follow-up.

DISCUSSION

Most NC/RC in infants resolve without surgical intervention but some infants require medical therapy and follow-up. Risk factors for NC/RC in neonates continue to be poorly defined because of the quality of studies available. Our study provides further adjustment for confounders but has a small sample size and is restricted to neonates from an intensive care unit.

CONCLUSION

Most cases of NC/RC resolve spontaneously without surgical intervention. The mean time to resolution is 12.1 months, without untoward consequences in terms of hypertension. A history of UTIs is the only identified risk factor identified in this study which is associated with a significant increased risk of neonatal nephrocalcinosis and/or renal calculi. Larger prospective studies are warranted to confirm these findings.

Renal consequences of preterm birth

Background

The developmental origin of health and disease concept identifies the brain, cardiovascular, liver, and kidney systems as targets of fetal adverse programming with adult consequences. As the limits of viability in premature infants have been pushed to lower gestational ages, the long-term impact of prematurity on kidneys still remains a significant burden during hospital stay and beyond.

Objectives

The purpose of this study is to summarize available evidence, mechanisms, and short- and long-term renal consequences of prematurity and identify nephroprotective strategies and areas of uncertainty.

Results

Kidney size and nephron number are known to be reduced in surviving premature infants due to disruption of organogenesis at a crucial developmental time point. Inflammation, hyperoxia, and antiangiogenic factors play a role in epigenetic conditioning with potential life-long consequences. Additional kidney injury from hypoperfusion and nephrotoxicity results in structural and functional changes over time which are often unnoticed. Nephropathy of prematurity and acute kidney injury confound glomerular and tubular maturation of preterm kidneys. Kidney protective strategies may ameliorate growth failure and suboptimal neurodevelopmental outcomes in the short term. In later life, subclinical chronic renal disease may progress, even in asymptomatic survivors.

Conclusion

Awareness of renal implications of therapeutic interventions and renal conservation efforts may lead to a variety of short and long-term benefits. Adequate monitoring and supplementation of microelement losses, gathering improved data on renal handling, and exploration of new avenues such as reliable markers of injury and new therapeutic strategies in contemporary populations, as well as long-term follow-up of renal function, is warranted.

Proteinuria and hematuria in the neonate

PURPOSE OF REVIEW

Neonatal proteinuria and hematuria while not common can have potentially devastating consequences if left undiagnosed and untreated. It is important to distinguish between inherited and acquired causes of proteinuria to initiate appropriate and timely treatment. With regards to hematuria, it is critical to identify true hematuria from pseudo-hematuria to balance between thorough investigation and unnecessary laboratory work up. This review provides an overview of the common causes of hematuria and proteinuria in a neonate.

RECENT FINDINGS

The identification of genetic mutations in nephrotic syndrome has improved our understanding of the role of various proteins that play an important role in maintaining the glomerular filtration barrier. With the advancement in our ability to provide care for extreme premature neonates, the incidence of acute kidney injury has increased in these neonates along with proteinuria and hematuria.

SUMMARY

Persistent proteinuria after neonatal acute kidney injury would be of interest in regards to the risk of developing future chronic kidney disease and hypertension.

The effects of low and high dose oral calcium and phosphor supplementation on nephrocalcinosis diagnosed by sonography in premature and low birth weight neonates

Nephrocalcinosis is defined as calcium deposition in the renal interstitium. One of the major causes of neonatal nephrocalcinosis is the use of calcium and phosphor supplements for premature neonates. This study aims at assessing the effects of calcium and phosphor supplementation in neonatal nephrocalcinosis by renal ultrasonography. In this randomized controlled trial, 37 premature neonates with birth weights <1500 g or a gestational age of <34 weeks were considered. Two different doses of calcium 75 vs. 230 mg/kg/day and phosphor 50 vs. 110 mg/kg/day were prescribed and laboratory and sonographic data were then documented and evaluated. The incidence of nephrocalcinosis was 47.8% in group 1 and 28.6% in group 2. There was a significant association between NC and positive family history of renal stones, shorter duration of TPN and NICU stay. The amount of calcium dosage, gestational age, birth weight, sex, use of surfactants, and mechanical ventilation did not have any significant association with NC. In this study, the neonates with NC were mostly the white flake type (8 cases) and the majority of the lesions were 1-2 mm. All the lesions were located in the pyramid and papilla areas, acoustic shadows were not prevalent and stones were not observed in any of the patients.

TRIAL REGISTRATION NUMBER

IRCT2013060810441N3.

Early postnatal calcium and phosphorus metabolism in preterm infants

OBJECTIVES

Bone mineralisation in preterm infants is related to the supply of calcium (Ca) and phosphorus (P). We increased the amount of minerals in parenteral nutrition (PN) for preterm infants and evaluated postnatal Ca and P metabolism in relation to mineral and vitamin D (vitD) intake.

METHODS

Preterm infants, included on their first day of life, received standard PN, providing a maximum Ca/P intake of 3/1.92 mmol · kg(-1) · day(-1) on day 3. Ca/P content of formula was 2.5/1.6 mmol/dL, and fortified human milk was 2.4/1.95 mmol/dL. PN supplied 80 IU · kg(-1) · day(-1) vitD. Formula and fortified human milk contained 200 IU/dL of vitD. During a 5-week period, serum concentrations and urinary excretion of Ca/P were registered and related to the intake of minerals and vitD.

RESULTS

During 12 months, 79 infants (mean gestational age 29.8 ± 2.2 weeks, mean birth weight 1248 ± 371 g) were included. The recommended intake for minerals was achieved by day 5 and for vitD by 4 weeks. Infants developed hypercalcaemia, hypercalciuria, and hypophosphataemia during the first postnatal week, leading to the additional P supplementation in 49 infants. The renal tubular reabsorption of P was >95% until day 9 but decreased <70% after the second week. Alkaline phosphatase was normal at birth, increased to a maximum of 450 IU/L by day 14, and remained above the normal range for the remaining period.

CONCLUSIONS

Parenteral intake of P appeared to be too low, leading to mineral imbalances in the early postnatal period, and vitD intake was also below recommendations.

Detection of novel LAMA3 mutation in Herlitz junctional epidermolysis bullosa in a Jordanian family

The Herlitz junctional epidermolysis bullosa (H-JEB) subtype usually presents as a severe lethal inherited variant of epidermolysis bullosa (EB) caused by a homozygous mutation in the genes LAMA3, LMAB3, or LAMAC3. Each gene encodes one of the three chains of heterotrimer laminin-332 proteins (including the alpha-3 chain, beta-3 chain and gamma-2-chain) responsible for the adherence of the epidermis to the underlying dermis. The aim of this report is to add to the existing knowledge about EB by describing a novel mutation in a gene responsible for genodermatosis. A case of a Jordanian male neonate, born to healthy, first cousin consanguineous parents, who developed nonhealing blistering skin and mucous membrane lesions, crusted erosions with significant granulation tissue and dystrophic nails immediately after birth is described. The patient was diagnosed as having a novel LAMA3 mutation causing (H-JEB) by immunofluorescence mapping and molecular analysis. Both parents and this baby's sibling were shown to be heterozygous carriers of the same mutation. Pre-implantation diagnosis using molecular analysis for subsequent pregnancies in this family is crucial for managing any new pregnancy.

Renal function and kidney length in preterm infants with nephrocalcinosis: a longitudinal study

Renal injury in early life may lead to hypertension and renal disease in adulthood. In this prospective study, we estimated renal glomerular and tubular function and kidney length (KL) during the first 2 years of life of preterm infants with nephrocalcinosis (NC) associated with prematurity. The study cohort comprised 107 preterm children, 63 with NC and 44 control subjects without NC who were matched for gender, gestational age and birth weight. Kidney function was estimated based on measurements of serum creatinine (Scr), estimated glomerular filtration rate (eGFR), fractional excretion (FE) of sodium (Na), potassium (K), phosphate (P), magnesium (Mg) and uric acid (UA) and on the ratios of urinary Ca, oxalate (UOx) and citrate (UCit) to urinary creatinine (UCa/Ucr, UOx/Ucr and UCit/Ucr, respectively) calculated from morning urine collections. KL was measured by ultrasonography. Measurements were made at 40 weeks postmenstrual age and at 3, 6, 12 and 24 months of age. At 3 and 6 months, the NC group had higher UCa/Ucr, FEK and FEUA than the control group; at 12 months, only the UCa/Ucr and FEUA was still higher. The UCa/UCit ratio was higher in the NC group. Scr and eGFR did not differ between the groups at any time point. The NC group had a shorter KL up to 12 months of life (left kidney) or 24 months (right kidney). Based on these results, we conclude that NC in the preterm infants enrolled in our study was associated with impaired renal tubular function and a shorter KL in the first year of life.

Nephrocalcinosis and urolithiasis in children

The incidence of adult urolithiasis has increased significantly in industrialized countries over the past decades. Sound incidence rates are not available for children, nor are they known for nephrocalcinosis, which can appear as a single entity or together with urolithiasis. In contrast to the adult kidney stone patient, where environmental factors are the main cause, genetic and/or metabolic disorders are the main reason for childhood nephrocalcinosis and urolithiasis. While hypercalciuria is considered to be the most frequent risk factor, several other metabolic disorders such as hypocitraturia or hyperoxaluria, as well as a variety of renal tubular diseases, e.g., Dent's disease or renal tubular acidosis, have to be ruled out by urine and/or blood analysis. Associated symptoms such as growth retardation, intestinal absorption, or bone demineralization should be evaluated for diagnostic and therapeutic purposes. Preterm infants are a special risk population with a high incidence of nephrocalcinosis arising from immature kidney, medication, and hypocitraturia. In children, concise evaluation will reveal an underlying pathomechanism in >75% of patients. Early treatment reducing urinary saturation of the soluble by increasing fluid intake and by providing crystallization inhibitors, as well as disease-specific medication, are mandatory to prevent recurrent kidney stones and/or progressive nephrocalcinosis, and consequently deterioration of renal function.

Renal calcification in very low birth weight infants

BACKGROUND

Renal calcification in preterm infants has been described frequently. The etiologic factors have not yet been fully clarified. The objective of this study was to evaluate the incidence of and risk factors for renal calcification in our population.

METHODS

We retrospectively reviewed the charts of very low birth weight preterm infants during a 1-year period. Renal ultrasound scans were performed at term or before discharge and at a corrected age of 1 year.

RESULTS

Six infants (6%) had renal calcification at term or before discharge compared with 96 who did not. Factors significantly associated with renal calcification included gestational age (26 weeks vs. 29 weeks, p=0.006), birth weight (851 g vs. 1141 g, p=0.004), duration of mechanical ventilation (69 days vs. 29 days, p=0.002), length of intensive care (72 days vs. 41 days, p=0.013), furosemide therapy (33% vs. 3%, p=0.027), and dexamethasone therapy (50% vs. 2% p=0.001). Birth weight and dexamethasone therapy had significant independent association after stepwise logistic regression analysis. Sex, oliguria, acidosis, duration of oxygen therapy, length of hospital stay, nutrition status, and nephrotoxic drugs did not differ between the two groups. Three of the six infants had spontaneous remission of renal calcification, whereas two patients without the finding in neonatal stage had renal calcification at a corrected age of 1 year.

CONCLUSION

The incidence of renal calcification in very low birth weight infants in this study was relatively low, and the calcification was transient in one-half of the infants. Extremely premature, sick infants requiring long-term ventilation, and those receiving furosemide or dexamethasone were more likely to have renal calcification. Clinicians should be aware that renal calcification may develop beyond the neonatal stage.

Renal pyramids: focused sonography of normal and pathologic processes

In neonates and children, sonographic examinations of the renal pyramids may depict a spectrum of unique changes in echogenicity due to the effects of physiologic processes or a wide variety of pathologic processes that may affect the collecting ducts or interstitium of the pyramids. Focused sonographic evaluation of the pyramids with high-frequency transducers produces the most detailed images of the pyramids, revealing some appearances not previously reported, to the authors' knowledge. The authors highlight the clinical settings in which they have documented detailed changes in the echogenicity of the pyramids. The patterns of altered echogenicity alone may reflect a specific cause but in many instances are nonspecific, with clinical and biochemical correlation required to establish a more precise diagnosis. However, there is a lack of histologic data to completely explain the mechanism of many of these changes in echogenicity in all of the processes. As the authors have expanded their use of the focused sonographic technique, they have been able to depict altered echogenicity in the pyramids in greater numbers of children in whom an explanation for the changes is not always immediately apparent; for now, the cause must be considered idiopathic. More work is required to expand the use of this focused technique together with clinical, biochemical, and histologic correlation in an attempt to offer more complete explanations for the changes in echogenicity of the pyramids.

Nephrocalcinosis in preterm neonates

The prevalence of nephrocalcinosis (NC) in preterm neonates in recent reports is 7-41%. The wide range in prevalence is a consequence of different study populations and ultrasound equipment and criteria, in addition to a moderate interobserver variation. NC in preterm neonates has a multifactorial aetiology, consisting of low gestational age and birth weight, often in combination with severe respiratory disease, and occurs as a result of an imbalance between stone-promoting and stone-inhibiting factors. A limited number of histological studies suggest that calcium oxalate crystals play an important role in NC in premature neonates. In 85% of children resolution of NC occurs in the first years of life. Prematurity, per se, is associated with high blood pressure, relatively small kidneys, and (distal) tubular dysfunction. In addition, NC in preterm neonates can have long-term sequelae for glomerular and tubular function. Long-term follow-up of blood pressure and renal function of prematurely born children, especially with neonatal NC, is recommended. Prevention of NC with (low) oral doses of citrate has not resulted in a significant decrease in the prevalence of NC; a higher citrate dosage deserves further study. Future research pertaining to prevention of NC in preterm neonates is crucial.

Nephrocalcinosis in a preterm infant

Bilateral medullary echogenic foci are not uncommonly seen in renal ultrasounds of sick, preterm neonates. Often, the likely diagnosis is nephrocalcinosis. We present one such case. The long term outcome in this population is unknown, but is generally thought to be essentially good.

Effectiveness of pamidronate in severe neonatal hypercalcemia caused by subcutaneous fat necrosis: a case report

Subcutaneous fat necrosis of the newborn (SCFN) is a panniculitis that develops in fatty areas during the first weeks of life after foetal distress or perinatal complications. Prognosis is generally good with complete regression, but it can be complicated by metabolic abnormalities like hypoglycemia, hypertriglyceridemia, thrombocytopenia, and also potentially life-threatening hypercalcemia. We report a case of severe hypercalcemia complicating SCFN in a newborn who was treated with hyperhydration, furosemide, prednisone, and pamidronate.

An active renal crystal clearance mechanism in rat and man

The kidney has several defense mechanisms to avert nephrocalcinosis by preventing intratubular crystal formation and adherence. Little is known about the fate of luminally adhered crystals. In order to study post-crystal adhesion defense mechanisms we quantified the number and morphology of crystal-containing tubules in rats at various time points following ethylene glycol administration as well as in renal biopsies of patients diagnosed with nephrocalcinosis of different etiology. In rats, nephrocalcinosis was completely cleared by epithelial overgrowth of adherent crystals, which were then translocated to the interstitium and subsequently disintegrated. These processes correlated with a low to moderate infiltration of inflammatory cells. Patients with nephrocalcinosis due either to acute phosphate nephropathy, primary hyperoxaluria, preterm birth, or transplantation also showed epithelial crystal overgrowth independent of the underlying disorder or the nature of the crystals. Our study found a quantitative association between changes in tubular and crystalline morphology and crystal clearance, demonstrating the presence of an important and active nephrocalcinosis-clearing mechanism in both rat and man.

Is nephrocalcinosis in preterm neonates harmful for long-term blood pressure and renal function?

OBJECTIVE

The aim of our study was to examine long-term effects of nephrocalcinosis in prematurely born children.

PATIENTS AND METHODS

Preterm neonates (gestational age <32 weeks) with (n = 42) and without (n = 32) nephrocalcinosis were prospectively studied at a mean age of 7.5 (+/-1.0) years.

RESULTS

Blood pressure did not differ in ex-preterm infants with and without nephrocalcinosis but was significantly higher than expected for healthy children. In comparison to healthy children, more ex-preterm infants with neonatal nephrocalcinosis had (mild) chronic renal insufficiency (glomerular filtration rate: <85 mL/min per 1.73 m2; 6 of 40); this is in contrast to ex-preterm infants without neonatal nephrocalcinosis (2 of 32). Tubular phosphate reabsorption and plasma bicarbonate were significantly lower in children with nephrocalcinosis compared with children without nephrocalcinosis. In addition, more ex-preterm infants with and without nephrocalcinosis than expected had low values for plasma bicarbonate and early-morning urine osmolality compared with healthy children. Kidney length of ex-preterm infants with and without nephrocalcinosis was significantly smaller than expected in healthy children of the same height. Nephrocalcinosis persisted long-term in 4 of 42 children but was not related to blood pressure, kidney length, or renal function.

CONCLUSIONS

Nephrocalcinosis in preterm neonates can have long-term sequelae for glomerular and tubular function. Furthermore, prematurity per se is associated with high blood pressure, relatively small kidneys, and (distal) tubular dysfunction. Long-term follow-up of blood pressure and renal glomerular and tubular function of preterm neonates, especially with neonatal nephrocalcinosis, seems warranted.