Evaluation of renal glomerular and tubular functional and structural integrity in neonates

Insulin-like growth factor-1 effects on kidney development in preterm piglets

BACKGROUND

Preterm birth disrupts fetal kidney development, potentially leading to postnatal acute kidney injury. Preterm infants are deficient in insulin-like growth factor 1 (IGF-1), a growth factor that stimulates organ development. By utilizing a preterm pig model, this study investigated whether IGF-1 supplementation enhances preterm kidney maturation.

METHODS

Cesarean-delivered preterm pigs were treated systemically IGF-1 or vehicle control for 5, 9 or 19 days after birth. Blood, urine, and kidney tissue were collected for biochemical, histological and gene expression analyses. Age-matched term-born pigs were sacrificed at similar postnatal ages and served as the reference group.

RESULTS

Compared with term pigs, preterm pigs exhibited impaired kidney maturation, as indicated by analyses of renal morphology, histopathology, and inflammatory and injury markers. Supplementation with IGF-1 reduced signs of kidney immaturity, particularly in the first week of life, as indicated by improved morphology, upregulated expression of key developmental genes, reduced severity and incidence of microscopic lesions, and decreased levels of inflammatory and injury markers. No association was seen between the symptoms of necrotizing enterocolitis and kidney defects.

CONCLUSION

Preterm birth in pigs impairs kidney maturation and exogenous IGF-1 treatment partially reverses this impairment. Early IGF-1 supplementation could support the development of preterm kidneys.

IMPACT

Preterm birth may disrupt kidney development in newborns, potentially leading to morphological changes, injury, and inflammation. Preterm pigs have previously been used as models for preterm infants, but not for kidney development. IGF-1 supplementation promotes kidney maturation and alleviates renal impairments in the first week of life in preterm pigs. IGF-1 may hold potential as a supportive therapy for preterm infants sensitive to acute kidney injury.

The impact of intrauterine growth restriction and prematurity on nephron endowment

In humans born at term, maximal nephron number is reached by the time nephrogenesis is completed - at approximately 36 weeks' gestation. The number of nephrons does not increase further and subsequently remains stable until loss occurs through ageing or disease. Nephron endowment is key to the functional capacity of the kidney and its resilience to disease; hence, any processes that impair kidney development in the developing fetus can have lifelong adverse consequences for renal health and, consequently, for quality and length of life. The timing of nephrogenesis underlies the vulnerability of developing human kidneys to adverse early life exposures. Indeed, exposure of the developing fetus to a suboptimal intrauterine environment during gestation - resulting in intrauterine growth restriction (IUGR) - and/or preterm birth can impede kidney development and lead to reduced nephron endowment. Furthermore, emerging research suggests that IUGR and/or preterm birth is associated with an elevated risk of chronic kidney disease in later life. The available data highlight the important role of early life development in the aetiology of kidney disease and emphasize the need to develop strategies to optimize nephron endowment in IUGR and preterm infants.

Urine podocyte mRNA loss in preterm infants and related perinatal risk factors

BACKGROUND

Preterm birth has been identified as a risk factor for development of long-term chronic kidney disease. Podocyte loss has been reported to contribute to this process in preterm animal models. However, details about podocyte loss in preterm infants and related perinatal risk factors have not been well clarified.

METHODS

Forty full-term infants and 106 preterm infants were enrolled. Urine samples were collected from full-term infants within 4-7 days of birth and preterm infants at 37-40 weeks of corrected age. Levels of urine podocin mRNA, urine protein (UP), and urine microalbumin (UMA) were measured, and the relationship between these markers was evaluated. Clinical information in these infants was collected, and potential correlates that may lead to increased podocyte loss during the perinatal period were identified using linear regression analysis.

RESULTS

Urine podocyte loss indicated by the urine podocin mRNA to creatinine ratio (UpodCR) was higher in preterm infants than in full-term infants. UpodCR was correlated with the levels of UP and UMA. Multiple linear regression analysis also showed that lower gestational age (GA) at birth and small for gestational age (SGA) were high risk factors for urine podocyte loss.

CONCLUSIONS

Increasing urine podocyte loss was identified in preterm infants. Moreover, perinatal factors were associated with podocyte loss and may be a potential direction for comprehensive research and intervention in this field. A higher resolution version of the Graphical abstract is available as Supplementary information.

Urinary protein to creatinine ratio during the first month of life in very preterm infants-a prospective cohort study (PROTIPREMA)

BACKGROUND

Preterm infants have physiological proteinuria and values of urine protein to creatinine ratio (UPr/Cr) are higher compared to full-term infants during the first week of life. Few investigations explored the changes of proteinuria in very preterm infants (VPI, ≤ 31 weeks of gestation) older than a week, and it is unclear whether high and persistent proteinuria is associated with kidney injury in this population. This study aimed to (1) observe the changes of UPr/Cr during the first month of life in VPI and (2) describe clinical and biological variables associated with the changes of UPr/Cr.

METHODS

Spot urine samples for UPr/Cr were collected on the first day of life (DOL1) and then on DOL2-3, DOL5-6, second week of life (WOL2), WOL3, and WOL4 in VPI cared for in a third-level NICU. We tested the relationship of UPr/Cr with perinatal variables and diseases.

RESULTS

A total of 1140 urine samples were obtained for 190 infants. UPr/Cr values (mg/mmol) (median with interquartile) at DOL1, DOL2, DOL3, WOL2, WOL3, and WOL4 were, respectively, 191 (114-399), 226 (152-319), 225 (156-350), 282 (200-488), 308 (188-576), and 325 (175-664). At the multivariate analysis, lower gestational age (GA) and increasing postnatal age were the only variables significantly associated with higher UPr/Cr values (p < 0.001). There was wide intra- and interindividual variability in UPr/Cr, especially in infants with higher GA and clinical stability.

CONCLUSIONS

In VPI, UPr/Cr is higher at lower GA and increases with advancing postnatal age. High persistent proteinuria is not associated with clinical and biological variables reflecting kidney injury during the first month of life. A higher resolution version of the Graphical abstract is available as Supplementary information.

Point-of-Care (POC) Urinary L-Type Fatty Acid-Binding Protein (u-LFABP) Use in Critically Ill, Very Preterm Neonates

Preterm neonates are born with fewer functional nephrons, rendering them vulnerable to secondary insult. These insults are associated with acute kidney injury (AKI); thus, structural damage must be detected as early as possible. Urinary L-type fatty acid-binding protein (u-LFABP) has been proposed as a highly suitable kidney injury biomarker during prematurity. We aimed to analyze the use of POC u-LFABP in critically ill, very preterm neonates. This study was conducted at the neonatal intensive care unit (NICU), Dr. Cipto Mangunkusumo General Hospital, from November to December 2020. Baseline characteristics were recorded from electronic medical records. u-LFABP examination utilized stored urine samples from a previous study and was performed using a LFABP POC test kit. The proportion of abnormal u-LFABP (83.3%) was highest at 72 hours. Neonates with older gestational age (0–48 hours; $p=0.017$ ) and higher birth weight (0–48 hours; $p=0.022$ , 72 hours; $p=0.013$ ) had normal u-LFABP levels. Neonates exposed to nephrotoxic agents showed higher proportion of abnormal u-LFABP (0–48 hours; $p=0.006$ ). Longer invasive mechanical ventilation (IMV) period was observed in neonates with abnormal u-LFABP levels at 0–48 hours (7.44 ± 7.9 vs. 1.50 ± 2.9 days; $p=0.011$ ). We found an association between complication rates and poorer disease outcome trends with abnormal u-LFABP; however, this relationship was not supported statistically. In conclusion, this study demonstrated that u-LFABP can be detected using bedside POC kit in critically ill very preterm neonates and those exposed to nephrotoxic agents may be at risk for kidney injury, confirmed by abnormal u-LFABP levels.

Distribution of proteinuria- and albuminuria-to-creatinine ratios in preterm newborns

BACKGROUND

Urine protein assessment is important when glomerular disease or injury is suspected. Normal values of proteinuria already published for preterm newborns suffer from limitation, with small cohorts of patients. This prospective study was conducted to update the urine total protein- and albumin-to-creatinine ratio values.

METHODS

Urine samples were collected from 231 preterm newborns within the first 48 h (D0-1) and/or between 72-120 h of life (D3-4). Total protein, albumin, and creatinine were measured, their distribution and upper-limit values determined.

RESULTS

At D0-1 and D3-4, respectively, the median for the total protein-to-creatinine ratio were 80 and 107 mg/mmol (upper-limit values 223 and 289 mg/mmol) in the whole studied population, 149 and 214 mg/mmol in children born before 29 weeks of gestational age, 108 and 130 mg/mmol in those born between 29 and 33 weeks, and 61 and 93 mg/mmol in those born after 33 weeks. For the albumin-to-creatinine ratio, the median were 12 and 17 mg/mmol (upper-limit values 65 and 62 mg/mmol) in the whole studied population, 22 and 50 mg/mmol in children born before 29 weeks, 21 mg/mmol in those born between 29 and 33 weeks, and 8 and 12 mg/mmol in those born after 33 weeks. The use of nephrotoxic drugs and mechanical ventilation seems to influence proteinuria and albuminuria values.

CONCLUSIONS

We report distribution of proteinuria- and albuminuria-to-creatinine in preterm newborns, including the upper-limit values. These values should be taken into account in the detection and diagnosis of glomerular disease and/or injury in daily clinical practice. Graphical abstract.

Urinary Cystatin-C, a marker to assess and monitor neonatal kidney maturation and function: validation in twins

BACKGROUND

Nephrogenesis is a complex process of nephron formation and maturation that can be compromised by preterm delivery and intrauterine growth restriction. This study aimed to evaluate and compare urinary Cys-C levels with renal volume in a cohort of preterm and term twins, adequate for gestational age or intrauterine growth restricted, to investigate their values in different conditions of nephrogenesis.

METHODS

The study was performed on twins at 30-40 days of postnatal corrected age: renal volumes were measured by 3D ultrasound technology and urine samples were analyzed for Cystatin-C. A follow-up was performed by Cystatin-C.

RESULTS

Renal volumes in preterm and intrauterine growth-restricted twins showed values significantly lower than those observed in term twins and were inversely correlated to urinary Cystatin-C levels. During the follow-up, intrauterine growth-restricted twins showed amplified levels of urinary Cystatin-C; in contrast, invariable or decreased levels were observed in adequate for gestational age twins.

CONCLUSIONS

Urinary Cystatin-C, evaluated when intrauterine/extrauterine nephrogenesis could be considered completed, concurrently with renal volume assessment can improve the identification of neonates with initial kidney impairment. Its potential value as a useful marker in monitoring physiological/pathological renal conditions could be considered, mainly for neonates at elevated risk of developing long-term renal diseases.

IMPACT

Urinary Cys-C levels are inversely correlated to renal volumes and reflect nephrogenesis conditions. No data in literature are reported regarding: (a) the concurrent assessment of renal volumes and urinary levels of Cystatin-C in preterm and term twins with different conditions of gestational life, i.e., AGA and IUGR and (b) the follow-up of IUGR and preterm neonates using the urinary Cys-C determination. The variations of urinary Cys-C levels, observed in the follow-up of preterm and/or IUGR neonates, support the usefulness of monitoring those neonates with altered nephrogenesis, who are later at risk for renal impairment and for long-term renal diseases.

Changes in Serum Creatinine Levels and Natural Evolution of Acute Kidney Injury with Conservative Management of Hemodynamically Significant Patent Ductus Arteriosus in Extremely Preterm Infants at 23-26 Weeks of Gestation

Changes in kidney function in extremely preterm infants (EPT) with conservatively managed hemodynamically significant (HS) patent ductus arteriosus (PDA) are not known well. We aimed to present the postnatal course in serum creatinine levels (sCr), prevalence of acute kidney injury (AKI), then relevance between AKI and adverse outcomes in EPT with conservatively managed HS PDA. By review of medical records, we analyzed the postnatal course of sCr and prevalence of stage 3 AKI defined by the modified Kidney Disease Improving Global Outcome (KDIGO) in EPT at gestational age of 23 to 26 weeks with conservatively treated HS PDA. We investigated if the presence and/or prolonged duration of stage 3 AKI elevated the risk of adverse outcomes. The results showed that, neither factor was associated with adverse outcomes. While the average PDA closure date was at postnatal day (P) 41 and 53, sCr peaked at P 10 and 14 and the cumulative prevalence of stage 3 AKI was 57% and 72% in the EPT of 25–26 and 23–24 weeks’ gestation, respectively. The high prevalence of stage 3 AKI without adverse outcomes in EPT with conservatively managed HS PDA suggests that it might reflect renal immaturity rather than pathologic conditions.

Extra uterine development of preterm kidneys

OBJECTIVE

We carried out a study to determine the impact of prematurity on renal development. The primary outcomes measured were nephrinuria and albuminuria; renal volume and glomerular filtration rate were the secondary outcomes.

METHODS

Preterm neonates born at less than 28 weeks of gestation, with birth weight between 10th and 90th centile (appropriate for gestational age), were recruited and underwent assessments at 28, 32 and 37 weeks postmenstrual age (PMA).

RESULTS

Fifty-three premature neonates and 31 term neonates (control) were recruited. The median gestational age of the premature neonates was 26.4 [24.7-27.4] weeks, with a mean birth weight of 886 (179) g. The mean gestational age of term neonates was 39.1 (1.2) weeks and the mean birth weight was 3406 (406) g. The median age of the term neonates was 6.5 [3.0-12.5] days. The total kidney volume (TKV) almost doubled from 10.3 (2.9) cm³ at 28 weeks PMA to 19.2 (3.7) cm³ at 37 weeks PMA (P = 0.0001). TKV at 37 weeks PMA was significantly smaller compared to term neonates (19.2 (3.7) vs 26.3 (7.0) cm³; P = 0.0001). However, there was no significant difference in estimated glomerular filtration rate (eGFR) between premature neonates (at 37 weeks PMA) and term neonates (control) (43.5 [39.7-48.9] vs. 42.0 [38.2-50.0] mL/min/1.73 m²; P = 0.75). There was a statistically significant decline in nephrin-creatinine ratio and albumin-creatinine ratio from 32 to 37 weeks PMA.

CONCLUSIONS

Despite having a smaller renal volume (and fewer nephrons), extremely premature neonates achieve similar eGFRs at corrected term as term-born neonates, likely through single nephron hyperfiltration. Extremely premature neonates also show evidence of glomerular injury.

Biochemical parameters of renal impairment/injury and surrogate markers of nephron number in intrauterine growth-restricted and preterm neonates at 30-40 days of postnatal corrected age

BACKGROUND

Premature and/or intrauterine growth-restricted neonates have an increased risk of developing postnatal renal injuries in later life. Studies on renal physiology in these neonates at a corrected age of 30-40 days are scarce and mostly relate to preterm infants. The data from these studies often lack the results of correlation analyses between biochemical parameters and nephron number-data which could provide additional insight and/or improve recognition of individuals at higher risk of renal failure.

METHODS

Urinary total protein and albumin levels and N-acetyl-β-D-glucosaminidase and cathepsin B activity were evaluated in preterm and intrauterine growth-restricted infants at a corrected age of 30-40 days and compared to data from a healthy control neonate population. The data were then associated with predominant susceptibility factors of renal damage related to low nephron number, such as gestational age, birth weight, total renal volume and renal cortex volume.

RESULTS

Compared to the control neonate population, we found significantly increased levels of all biochemical parameters tested in the intrauterine growth-restricted neonates, whereas in the preterm infants we observed a significant increase in cathepsin B activity, total protein level and, to a lesser extent, albumin level. Cathepsin B activity showed a significant, strong and inverse correlation with all surrogate markers of nephron number and was also strongly and positively correlated with urinary albumin level.

CONCLUSIONS

At this postnatal age, we found that lower nephron number in low birth weight neonates was associated to tubular impairment/injury that could be concurrent with a dysfunction of glomerular permeability. Urinary cathepsin B activity may be a candidate marker for the early prediction of renal susceptibility to damage in low birth weight neonates.

Effect of mercury vapour exposure on urinary excretion of calcium, zinc and copper: relationship to alterations in functional and structural integrity of the kidney

Background: The kidney has a remarkable capacity to concentrate mercury (Hg) and as such is a primary target organ when exposure to Hg occurs, and it is also an organ for Hg excretion. Objective: The present work aims to investigate the effect of occupational Hg vapour exposure on the urinary excretion of calcium (Ca), zinc (Zn) and copper (Cu), and the possible association of this excretion to work duration as well as renal alterations. Methods: 83 non-smoker participants (36 referents, age: 35.69/9.5 years; 27 Hg vapour-exposed workers with 5/10 years work duration, age: 33.09/5.1 years; and 20 Hg vapour-exposed workers with]/11 years work duration, age: 39.509/8.50 years) were included in the present study. Urinary levels of microalbumin (U-Malb) and retinol-binding protein (U-RBP) as well as cytosolic glutathione S-transferase activity (U-GST) were measured to assess the glomerular and proximal tubular reabsorption functions as well as structural integrity of proximal tubules; respectively. In addition, blood Hg (B-Hg), serum levels of Hg (S-Hg) and Ca (S-Ca), and urinary levels of Hg (U-Hg), Ca (U-Ca), Zn (U-Zn), Cu (U-Cu) and creatinine (U-cr) were estimated. Results: In comparison to referents, all investigated parameters showed significant increase (except S-Ca and U-Zn/U-Cu ratio that significantly decreased among the workers as one group, S-Ca and U-Zn/U-Cu ratio that significantly and nonsignificantly decreased; respectively among workers with 5/10 years work duration, S-Ca and U-Zn/U-Cu ratio that significantly decreased among workers with]/11 years work duration). In addition, B-Hg was nonsignificantly increased and S-Ca was significantly decreased; also, both U-Hg and U-Zn/U-Cu were nonsignificantly decreased among workers with]/11 years work duration in comparison to those with 5/10 years work duration. Also, each of U-Hg, U-Ca, U-Zn and U-Cu was related to one another, while each of U-Ca, U-Zn and U-Cu was related to each of U-Malb, U-RBP and U-GST (except U-Zn was not related to U-GST). Conclusion: Hg vapour exposure leads to renal alterations which may parallel the change in proteinuria and enzymuria as well as the increased loss in urine of each of Ca, Zn and Cu. The urinary assessment of these metals may be used as a good indicator for renal dysfunction.

Effect of vitamin A supplementation on the urinary retinol excretion in very low birth weight infants

Despite high-dose vitamin A supplementation of very low birth weight infants (VLBW, <1500 g), their vitamin A status does not improve substantially. Unknown is the impact of urinary retinol excretion on the serum retinol concentration in these infants. Therefore, the effect of high-dose vitamin A supplementation on the urinary vitamin A excretion in VLBW infants was investigated. Sixty-three VLBW infants were treated with vitamin A (5000 IU intramuscular, 3 times/week for 4 weeks); 38 untreated infants were classified as control group. On days 3 and 28 of life, retinol, retinol-binding protein 4 (RBP4), glomerular filtration rate, proteinuria, and Tamm-Horsfall protein were quantified in urine. On day 3 of life, substantial retinol and RBP4 losses were found in both groups, which significantly decreased until day 28. Notwithstanding, the retinol excretion was higher (P < 0.01) under vitamin A supplementation as compared to infants of the control group. On day 28 of life, the urinary retinol concentrations were predictive for serum retinol concentrations in the vitamin A treated (P < 0.01), but not in the control group (P = 0.570).

CONCLUSION

High urinary retinol excretion may limit the vitamin A supplementation efficacy in VLBW infants. Advanced age and thus postnatal kidney maturation seems to be an important contributor in the prevention of urinary retinol losses.

Assessment of renal functional maturation and injury in preterm neonates during the first month of life

Worldwide, approximately 10% of neonates are born preterm. The majority of preterm neonates are born when the kidneys are still developing; therefore, during the early postnatal period renal function is likely reflective of renal immaturity and/or injury. This study evaluated glomerular and tubular function and urinary neutrophil gelatinase-associated lipocalin (NGAL; a marker of renal injury) in preterm neonates during the first month of life. Preterm and term infants were recruited from Monash Newborn (neonatal intensive care unit at Monash Medical Centre) and Jesse McPherson Private Hospital, respectively. Infants were grouped according to gestational age at birth: ≤28 wk (n = 33), 29-31 wk (n = 44), 32-36 wk (n = 32), and term (≥37 wk (n = 22)). Measures of glomerular and tubular function were assessed on postnatal days 3-7, 14, 21, and 28. Glomerular and tubular function was significantly affected by gestational age at birth, as well as by postnatal age. By postnatal day 28, creatinine clearance remained significantly lower among preterm neonates compared with term infants; however, sodium excretion was not significantly different. Pathological proteinuria and high urinary NGAL levels were observed in a number of neonates, which may be indicative of renal injury; however, there was no correlation between the two markers. Findings suggest that neonatal renal function is predominantly influenced by renal maturity, and there was high capacity for postnatal tubular maturation among preterm neonates. There is insufficient evidence to suggest that urinary NGAL is a useful marker of renal injury in the preterm neonate.

Clinical pharmacology of furosemide in neonates: a review

Furosemide is the diuretic most used in newborn infants. It blocks the Na⁺-K⁺-2Cl⁻ symporter in the thick ascending limb of the loop of Henle increasing urinary excretion of Na⁺ and Cl⁻. This article aimed to review the published data on the clinical pharmacology of furosemide in neonates to provide a critical, comprehensive, authoritative and, updated survey on the metabolism, pharmacokinetics, pharmacodynamics and side-effects of furosemide in neonates. The bibliographic search was performed using PubMed and EMBASE databases as search engines; January 2013 was the cutoff point. Furosemide half-life (t_1/2) is 6 to 20-fold longer, clearance (Cl) is 1.2 to 14-fold smaller and volume of distribution (Vd) is 1.3 to 6-fold larger than the adult values. t_1/2 shortens and Cl increases as the neonatal maturation proceeds. Continuous intravenous infusion of furosemide yields more controlled diuresis than the intermittent intravenous infusion. Furosemide may be administered by inhalation to infants with chronic lung disease to improve pulmonary mechanics. Furosemide stimulates prostaglandin E2 synthesis, a potent dilator of the patent ductus arteriosus, and the administration of furosemide to any preterm infants should be carefully weighed against the risk of precipitation of a symptomatic patent ductus arteriosus. Infants with low birthweight treated with chronic furosemide are at risk for the development of intra-renal calcifications.

Cyclosporin A may cause injury to undifferentiated glomeruli persisting in patients with Alport syndrome

BACKGROUND/AIMS

Alport syndrome (AS) is a renal disorder caused by a genetic abnormality of type IV collagen α3 and α4, or α5 genes and shows a poor prognosis. Since the defect of type IV collagen synthesis disturbs the maturation process of the glomerular capillary loop, residual immature glomeruli persist after birth. The therapeutic efficacy of cyclosporin A (CyA) for AS patients seems to be controversial. We recently noted that renal specimens obtained from a child with AS who was treated with CyA and then developed CyA nephropathy included an increased number of undifferentiated embryonic-type glomeruli.

METHODS

We analyzed renal histologic and immunohistologic findings in children with AS who did (n = 3) or did not (n = 2) develop CyA-induced nephropathy despite appropriately low serum CyA concentrations (<100 ng/mL) being maintained over a period of 2 years. To discriminate embryonic-type from mature glomeruli, staining for type IV collagen α1, laminin β1, and laminin β2 accompanied by light microscopic observation were employed. Staining patterns were used to semiquantitatively assess glomerular immaturity (glomerular immaturity index, or GII).

RESULTS

In initial biopsy specimens, residual embryonic-type glomeruli were observed in each patient. Patients with early-onset CyA nephropathy had a high GII (median value 2.91 vs 1.23 ± 0.62 normal kidney tissues). In the follow-up biopsy after CyA treatment, surviving embryonic-type, collapsing embryonic-type, and sclerotic glomeruli that had failed to differentiate were observed. Taken together, the number of these glomeruli essentially equaled the total number of embryonic-type glomeruli in specimens obtained before CyA treatment.

CONCLUSIONS

Our findings indicate a need for caution in CyA therapy for patients with AS, even for a relatively short course of administration, because some patients may have an unexpected number of embryonic-type glomeruli that predispose to CyA nephropathy.

Urine erythropoietin level is associated with kidney and brain injury in critically ill neonates

BACKGROUND

Erythropoietin (EPO) is a glycoprotein hormone produced predominantly in the kidneys. The protective effect of exogenous EPO in hypoxic-ischemic brain injury has been thoroughly examined in neonates. However, the metabolism of endogenous EPO in neonates remains unclear.

OBJECTIVES

We aimed to evaluate the concentration of urinary EPO (uEPO) in critically ill neonates and to identify possible clinical and laboratory variables that may be associated with uEPO levels.

METHODS

The concentrations of EPO, cystatin-C, microalbumin, and α1-microglobulin in the first available urine sample during the initial 72 h of life were measured in 103 critically ill neonates. Clinical and laboratory data were collected for each neonate.

RESULTS

There was a positive correlation between uEPO levels and urinary levels of cystatin-C (r = 0.265, p = 0.008), microalbumin (r = 0.422, p < 0.001), and α1-microglobulin (r = 0.421, p < 0.001). The concentration of uEPO was elevated in neonates who developed acute kidney injury (AKI) during the first week of life compared with those without AKI (p = 0.002) and was also elevated in neonates with brain injury, as demonstrated by ultrasound or magnetic resonance imaging, compared to neonates without brain injury (p = 0.008). An increased log10 uEPO level was associated with the occurrence of AKI (OR 2.70, p = 0.007) and brain injury (OR 2.33, p = 0.016).

CONCLUSIONS

An increased urinary EPO level in the early postnatal period is significantly associated with kidney and brain injury in critically ill neonates.

Preterm birth and the kidney: implications for long-term renal health

Although the majority of preterm neonates now survive infancy, there is emerging epidemiological evidence to demonstrate that individuals born preterm exhibit an elevated risk for the development of hypertension and renal impairment later in life, thus supporting the developmental origins of health and disease hypothesis. The increased risk may potentially be attributed to a negative impact of preterm birth on nephron endowment. Indeed, at the time when most preterm neonates are delivered, nephrogenesis in the kidney is still ongoing with the majority of nephrons normally formed during the third trimester of pregnancy. A number of clinical studies have provided evidence of altered renal function during the neonatal period, but to date there have been limited studies describing the consequences of preterm birth on kidney structure. Importantly, studies in the preterm baboon have shown that nephrogenesis is clearly ongoing following preterm birth; however, the presence of abnormal glomeruli (up to 18% in some cases) is of concern. Similar glomerular abnormalities have been described in autopsied preterm infants. Prenatal and postnatal factors such as exposure to certain medications, hyperoxia and intrauterine and/or extrauterine growth restriction are likely to have a significant influence on nephrogenesis and final nephron endowment. Further studies are required to determine the factors contributing to renal maldevelopment and to identify potential interventional strategies to maximize nephron endowment at the start of life, thereby optimizing long-term renal health for preterm individuals.

The efficacy and toxicity of two dosing-regimens of amikacin in neonates with sepsis

WHAT IS KNOWN AND OBJECTIVE

Neonatal sepsis is one of the most common reasons for admission to neonatal units in developing countries. Aminoglycosides widely used in its treatment are usually administered two or three times a day. Less frequent doing may be more convenient and as effective. We aim to compare the efficacy and safety (nephrotoxicity) of once daily vs. twice daily dosing of amikacin in neonates with suspected or proven sepsis and report on the drug's pharmacokinetics in these subjects.

METHODS

Thirty neonates of gestational age ≥ 36 weeks and body weight ≥ 2500 g with suspected or proven sepsis were randomized to receive amikacin either at a dose of 15 mg/kg once per day; group I (n = 15), or a dose of 7.5 mg/kg twice per day, group II (n = 15). All neonates received classical treatment of sepsis including antibiotics, hemodynamic support, inotropic support based on blood pressure levels and size of the heart in chest X-ray, if needed. Amikacin was infused over 1 h. Peak and trough serum samples for amikacin were measured for all infants at steady state. Nephrotoxicity was assessed by serum creatinine and urinary N-acetyl β-D-glucosaminidase before and 7 days after therapy. Clinical efficacy was compared using both observation of clinical status and normalization of laboratory tests.

RESULTS

All the patients in group I had achieved a trough level < 10 μg/mL and two patients had trough concentration > 10 μg/mL in group II. No significant difference between group I and group II in either baseline or day 7 serum creatinine was demonstrated (P >0.05). No significant difference was found between the two groups in clinical efficacy or renal toxicity. The calculated pharmacokinetic parameters were in group I and II, respectively: clearance = 63.8 ± 15.9 mL/kg/h and 73.5 ± 18.1 mL/kg/h; volume of distribution = 0.54 ± 0.09 L/kg and 0.61 ± 0.13 L/kg, half-life =6.1 ± 1.0 h and 5.95 ± 1.1 h.

WHAT IS NEW AND CONCLUSION

As expected, amikacin given once every 24 h to septic neonates of ≥ 36 weeks of gestation achieved higher peak levels and lower trough concentrations than the twice daily regimen. Treatment with once daily regimen did not lead to more nephrotoxicity than with a twice-daily regimen, and showed comparable efficacy.

Renal programming: cause for concern?

Development of the kidney can be altered in utero in response to a suboptimal environment. The intrarenal factors that have been most well characterized as being sensitive to programming events are kidney mass/nephron endowment, the renin-angiotensin system, tubular sodium handling, and the renal sympathetic nerves. Newborns that have been subjected to an adverse intrauterine environment may thus begin life at a distinct disadvantage, in terms of renal function, at a time when the kidney must take over the primary role for extracellular fluid homeostasis from the placenta. A poor beginning, causing renal programming, has been linked to increased risk of hypertension and renal disease in adulthood. However, although a cause for concern, increasingly, evidence demonstrates that renal programming is not a fait accompli in terms of future cardiovascular and renal disease. A greater understanding of postnatal renal maturation and the impact of secondary factors (genes, sex, diet, stress, and disease) on this process is required to predict which babies are at risk of increased cardiovascular and renal disease as adults and to be able to devise preventative measures.

Fluid and electrolyte management in the premature infant

Caring for the premature infant in the NICU requires knowledge and understanding of the physiologic adaptation to extrauterine life and how prematurity affects that transition. Nurses play an integral role in managing fluid and electrolyte balance in these infants. This article addresses postnatal adaptation and all aspects of fluid and electrolyte management of the preterm infant.

Diuretics in pediatrics : current knowledge and future prospects

This review summarizes current knowledge on the pharmacology, pharmacokinetics, pharmacodynamics, and clinical application of the most commonly used diuretics in children. Diuretics are frequently prescribed drugs in children. Their main indication is to reduce fluid overload in acute and chronic disease states such as congestive heart failure and renal failure. As with most drugs used in children, optimal dosing schedules are largely unknown and empirical. This is undesirable as it can potentially result in either under- or over-treatment with the possibility of unwanted effects. The pharmacokinetics of diuretics vary in the different pediatric age groups as well as in different disease states. To exert their action, all diuretics, except spironolactone, have to reach the tubular lumen by glomerular filtration and/or proximal tubular secretion. Therefore, renal maturation and function influence drug delivery and consequently pharmacodynamics. Currently advised doses for diuretics are largely based on adult pharmacokinetic and pharmacodynamic studies. Therefore, additional pharmacokinetic and pharmacodynamic studies for the different pediatric age groups are necessary to develop dosing regimens based on pharmacokinetic and pharmacodynamic models for all routes of administration.

Imaging of the neonatal genito-urinary tract

OBJECTIVE

To describe imaging of typical conditions and diseases in the neonatal genito-urinary (GU) tract.

METHOD

The use, the applications, and typical findings using standard imaging techniques (e.g., ultrasound, US, voiding cystourethrography, VCUG) are described, with emphasis on technical aspects, indications, and restrictions in neonatal queries. Only basic applications as used in routine clinical work are included, other more sophisticated and advanced imaging techniques such as scintigraphy, MR-urography, genitography or image-guided interventional procedures will only briefly be mentioned.

SUMMARY AND CONCLUSION

Conventional imaging methods are valuable and - particularly in the neonatal GU tract - sometimes irreplaceable. Skillfully used basic imaging techniques, particularly of US (including modern methods such as Doppler sonography, Harmonic imaging or contrast enhanced US), supplemented by fluoroscopy for VCUG can answer most acutely treatment relevant queries. Rarely early scintigraphic studies, genitography, or MRI may become indicated, usually not for establishing the diagnosis, but to collect additional (functional or anatomical) information necessary for deciding on further treatment, or even image guided interventional procedures may become necessary.

Tubular proteinuria in pre-term and full-term infants

Predictors of tubular proteinuria (alpha 1-M/crea ratio >10 mg/mmol) were sought in 100 infants of 24-32 weeks' (group 1) and 69 of 34-42 weeks' gestation (group 2). Random spot urine samples were obtained in the former group at the ages of 0-3 days, at 1-2 weeks and thereafter at 2-week intervals until the disappearance of tubular proteinuria, and in the latter one sample at a mean (SD) of 3.0 days' (1.3) age. In group 1, gestational age correlated negatively with the first urinary alpha 1-M/crea ratio. The highest urinary alpha 1-M/crea ratios [median (range) 39.1 mg/mmol (9.5-268.9)] occurred at a median (range) of 5 days' (1-42) age. Low gestational age and the need for inotropes predicted tubular proteinuria early after birth, whereas low gestation and long duration of ventilator treatment predicted the highest alpha 1-M/crea ratios. Prolonged vancomycin treatment and low gestational age were associated with delayed normalization of tubular proteinuria. In group 2 no significant risk factors for tubular proteinuria were found. The urinary alpha 1-M/crea ratio seems to be a sensitive indicator of renal tubular function in neonates, with low gestational age, the need for inotropes and prolonged assisted ventilation being predictors of increased tubular proteinuria. Long vancomycin courses should be avoided in pre-term infants in view of the prolonged adverse renal effects.

Evaluation of urinary proteins in healty full-term neonates by SDS-PAGE

The pattern of urinary proteins in healthy full-term neonates was examined by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE), coupled with determination of few parameters related to urinary protein excretion. Twenty healthy full-term neonates were included in the investigation. Five urine samples from each subject were collected on days 3, 7, 14, 21 and 28 after birth. Determination of total proteins was performed using turbidimetric method with sulfosalicylic acid. Urinary creatinine concentration was determined by Jaffe method. Urinary proteins were separated by horizontal gradient SDS-PAGE according to Görg. The highest values for total urinary proteins and for protein/creatinine ratio were detected in urine samples excreted on days 3 and 7 after birth. Three types of SDS-PAG electrophoretic profiles were observed. The first type of electrophoretic profile was characterized by the presence of proteins of mixed glomerular and tubular origin with molecular weights from 10 to 160 kDa. Typical for the second type of electrophoretic profile was the presence of two faint fractions with molecular weights of 78 and 90 kDa and several intensive low molecular weight fractions (14-67 kDa). In the third type of electrophoretic profile only low molecular weight proteins (10-67 kDa) were detected in all five urine samples. These findings express the transitory immaturity of the glomerular filter and tubular protein reabsorbing system of the newborn kidney. Apparently, the tubular protein handling normalizes later than the glomerular filtration of proteins.

Non-iatrogenic pathology of the preterm infant

Non-iatrogenic anatomical findings at autopsy provide insight into preterm infant physiology. The different patterns of lipid accumulation in the adrenal may correspond to long-term differences in stress response. Cardiac papillary muscle infarction occurs with asphyxia or shock and can explain myocardial dysfunction. Underdevelopment of preterm kidneys may correlate with susceptibility to renal disease and hypertension in adult life. Immaturity of the lung or immature responses to inflammation, rather than high oxygen concentrations or high ventilation pressures, may underlie chronic lung disease in premature infants. Hepatic extramedullary haematopoiesis is normal but, if excessive or abnormally persistent, can be an indicator of fetal disease. Hypertrophic somatostatin islet cells found with intra-uterine growth retardation may correlate with low serum insulin. Thymic involution may mark the degree of stress. Small thyroglobulin stores may limit the premature neonate's initiation of thermogenesis.

High incidence of nephrocalcinosis in extremely preterm infants treated with dexamethasone

BACKGROUND

The use of postnatal corticosteroids to treat or prevent chronic lung disease is common in very preterm infants. Medullary nephrocalcinosis has been noted as a possible side effect.

OBJECTIVE

This prospective study was designed to assess the incidence of nephrocalcinosis in extremely preterm infants exposed to dexamethasone.

PATIENTS AND METHODS

A prospective study of extremely preterm infants, recruited to a randomized trial of dexamethasone treatment for chronic lung disease, was initiated. Infants had US of the renal tract scheduled on entry into the study, at day 28 and at discharge or at the corrected gestational age of 36 weeks.

RESULTS

Thirty-three infants were enrolled in the study. Birth weight ranged between 440 and 990 g and gestation between 24 and 28 weeks. Nine infants died and six had incomplete data. Because there was no difference in incidence of calcification between those on the short course and those on the long course of dexamethasone, analysis was made on the entire cohort. One infant had nephrocalcinosis at the time of the initial US examination on day 26 of life. By day 28, nephrocalcinosis was present in 31% of those with complete data. By discharge, or corrected gestational age of 36 weeks, US evidence of nephrocalcinosis was present in 15 (83%) of 18 infants. All infants had at least one course of an aminoglycoside antibiotic during the study. All infants had parenteral nutrition. Only four infants received furosemide more regularly than single doses. The longest course was 10 days, received by an infant who did not develop nephrocalcinosis.

CONCLUSION

The incidence of nephrocalcinosis is high in this group of sick, extremely preterm infants. Dexamethasone may be a factor in the development of nephrocalcinosis. Future research should focus on the natural history of nephrocalcinosis in extremely preterm infants.

Investigating the newborn kidney: update on imaging techniques

Advances in imaging have resulted in higher-quality resolution. Techniques formerly considered to give pure anatomic information are now providing functional data, but the functions provided are not those typically measured in pathophysiologic terms. Instead, the data provided demand that we incorporate this new information into the understanding of the pathologic processes that confront us in clinical practice. Ultrasound provides information about kidney volume, blood flow velocity and blood flow volume. Radioisotopes can show the ability of the proximal tubules to extract the tracer from the blood as well as the ability of the kidney to clear the tracer into the bladder. Magnetic resonance imaging provides information about water content of the kidney.