Hematuria and Proteinuria in Children

Assessing masked hypertension and ambulatory arterial stiffness index in children congenital kidney malformations

BACKGROUND

Patients diagnosed with congenital kidney malformations are at an increased risk of developing hypertension, proteinuria, and progressing to chronic kidney disease (CKD). The present study aimed to determine the frequency of masked hypertension and ambulatory arterial stiffness index (AASI) in patients with congenital kidney malformations.

METHODS

The study included 174 patients with congenital kidney malformations (48 patients with unilateral renal agenesis (URA), 40 patients with ectopic kidney (EK), 36 patients with horseshoe kidney (HK), 31 patients with multicystic dysplastic kidney (MCDK), 19 patients with unilateral renal hypoplasia (URH), and 45 healthy controls.

RESULTS

The mean age was 12.9 ± 2.9 years, and the male-to-female ratio was 1.5. No significant differences were observed between the congenital kidney malformations groups concerning age, sex, follow-up period, proteinuria, or estimated glomerular filtration rate (eGFR) (P > 0.05). Nevertheless, the prevalence of masked hypertension exhibited a statistically significant increase in the congenital kidney malformations groups (except the URH group) compared to the control group (P < 0.05). The AASI was significantly greater in the congenital kidney malformations groups than in the control group (P < 0.05). The nighttime diastolic blood pressure (DBP), mean arterial pressure (MAP), and DBP index were significantly different between the congenital kidney malformations groups (P < 0.05). However, there were no significant differences in nondipping pattern, proteinuria, or masked hypertension between the congenital kidney malformations groups.

CONCLUSIONS

Patients with congenital kidney malformations should be periodically evaluated throughout life for BP. Based on the present findings, we strongly recommend ABPM for the diagnosis of masked hypertension and outcomes, including AASI score.

PM2.5 constituents associated with mortality and kidney failure in childhood-onset lupus nephritis: A 19-year cohort study

BACKGROUND

Childhood-onset lupus nephritis (cLN) is a severe form of systemic lupus erythematosus (SLE) with high morbidity and mortality. The impact of long-term exposure to fine particulate matter (PM2.5) on adverse outcomes in cLN remains unclear.

METHODS

We combined a 19-years cLN cohort from seven provinces in China with high-resolution PM2.5 dataset from 2001 to 2020, investigating the association between long-term exposure to PM2.5 and its constituents (sulfate, nitrate, organic matter, black carbon, ammonium) with the risk of death and kidney failure, analyzed with multiple variables Cox models. We also evaluated the association between 3-year average PM2.5 exposure before study entry and baseline SLE disease activity index (SLEDAI) scores using linear regression models.

RESULTS

Each 10 μg/m3 increase in annual average PM2.5 exposure was associated with an increased risk of death and kidney failure (HR = 1.58, 95 % CI: 1.24-2.02). Black carbon showed the strongest association (HR = 2.14, 95 % CI: 1.47-3.12). Higher 3-year average exposures to PM2.5 and its constituents were significantly associated with higher baseline SLEDAI scores.

CONCLUSIONS

These findings highlight the significant role of environmental pollutants in cLN progression and emphasize the need for strategies to mitigate exposure to harmful PM2.5 constituents, particularly in vulnerable pediatric populations.

A case with short stature and proteinuria: atypical presentation of a family with m.3243A>G mutation

BACKGROUND

The mitochondrial DNA (mtDNA) m.3243A>G mutation is one of the most common pathogenic mtDNA variants. The phenotypes associated with this mutation range from asymptomatic induviduals to well-defined clinical syndromes, or non-syndromic mitochondrial disorders. Variable clinical features in pediatric cases may cause difficulty in diagnosis. Kidney involvement in this mutation is uncommon and reported on a case-by-case basis. Here, we report on a patient with m.3243A>G mutation, who presented with short stature and proteinuria, and his family, who share the same genotype but exhibit different heteroplasmy levels in different tissues and variable phenotypes.

CASE PRESENTATION

A 15-year-old male patient was admitted to the pediatric endocrinology department with short stature. His examinations revealed nephrotic range proteinuria, hearing loss, impaired glucose tolerance, and Wolf-Parkinson-White syndrome. From family history, it was learned that diabetes mellitus (DM) and progressive sensorineural hearing loss were common in this family. The patient's mother, who had chronic kidney disease, DM, and hearing loss, had died suddenly for an unknown reason. Considering the family history, a genetic analysis was performed for mitochondrial disease. Mitochondrial DNA analysis revealed a m.3243A>G mutation with 47% heteroplasmy in blood, 62% heteroplasmy in buccal cells, and 96% heteroplasmy in urothelial cells in our patient.

CONCLUSIONS

Short stature without any other complaint and renal involvement are rare findings in m.3243A>G mutation. In patients presenting with proteinuria, in the presence of conditions affecting many systems such as endocrine system pathologies, hearing loss, and cardiac pathologies, and in the presence of individuals with a similar family history of multiple organ involvement, mitochondrial diseases should be considered, and examined from this perspective. Our case illustrates the value of a detailed medical and family history.

Clinical Characteristics of Children with Acute Post-Streptococcal Glomerulonephritis and Re-Evaluation of Patients with Artificial Intelligence

Objective

Acute post-streptococcal glomerulonephritis (APSGN) is a common cause of acute glomerulonephritis in children. The condition may present as acute nephritic and/or nephrotic syndrome and rarely as rapidly progressive glomerulonephritis. ChatGPT (OpenAI, San Francisco, California, United States of America) has been developed as a chat robot supported by artificial intelligence (AI). In this study, we evaluated whether AI can be used in the follow-up of patients with APSGN.

Methods

The clinical characteristics of patients with APSGN were noted from patient records. Twelve questions about APSGN were directed to ChatGPT 3.5. The accuracy of the answers was evaluated by the researchers. Then, the clinical features of the patients were transferred to ChatGPT 3.5 and the follow-up management of the patients was examined.

Results

The study included 11 patients with an average age of 9.08±3.96 years. Eight (72.7%) patients had elevated creatinine and 10 (90.9%) had hematuria and/or proteinuria. Anti-streptolysin O was high in all patients (955±353 IU/mL) and C3 was low in 9 (81.8%) patients (0.56±0.34 g/L). Hypertensive encephalopathy, nephrotic syndrome, and rapidly progressive glomerulonephritis were observed in three patients. Normal creatinine levels were achieved in all patients. Questions assessing the definition, epidemiologic characteristics, pathophysiologic mechanisms, diagnosis, and treatment of APSGN were answered correctly by ChatGPT 3.5. All patients were diagnosed with APSGN, and the treatment steps applied by clinicians were similarly recommended by ChatGPT 3.5.

Conclusions

The insights and recommendations offered by ChatGPT for patients with APSGN can be an asset in the care and management of patients. With AI applications, clinicians can review treatment decisions and create more effective treatment plans.

Safety of deer antler extract in children: A 12-week randomized controlled clinical trial

BACKGROUND

Deer antlers have been used as strong tonifying medicine in Asian countries, especially for the growth and development of children in pediatrics of Korean medicine. The safety of deer antler in adults cannot be applied directly to children because of their physiological characteristics. To accumulate reliable data on the safety of deer antler in pediatric populations, well-designed clinical studies are required.

METHODS

This research is a 12-week, randomized, double-blind, placebo-controlled clinical trial evaluating the safety of deer antler extract (DAE) in children. The DAE group received an intervention containing 1586 mg of DAE, whereas the control group received a placebo for 12 weeks. The safety was assessed by monitoring adverse drug reactions (ADRs) and laboratory test results.

RESULTS

One hundred participants were included in the safety analysis. Three and 2 participants in the DAE and control groups, respectively, reported ADRs. There was no significant difference in incidence between the 2 groups. ADRs are categorized into gastrointestinal and skin-related symptoms. No serious ADR was observed throughout the study. The laboratory test results were within or outside the normal range at clinically insignificant levels.

CONCLUSION

The research discovered that the DAE is safe in terms of ADRs and laboratory parameters under the conditions studied. Further studies are required to accumulate safety data about DAE dosage adjustment and potential interactions with other medicines.

Risk Factors for Urinary Tract Infections in Children with Hematuria in the Emergency Department

INTRODUCTION

Hematuria is a worrisome symptom in children and is sometimes associated with urinary tract infections (UTIs). This study aimed to identify useful clinical factors that can predict UTIs in hematuria patients without pyuria in the pediatric emergency department (ED).

METHODS

We retrospectively recruited patients with hematuria from the pediatric ED. Clinical symptoms, urine biochemistry and microscopic examination results, and blood laboratory tests were analyzed to identify the predictors of UTIs. Patients were divided into the verbal group (age ≥ 2 years) and non-verbal group (age < 2 years) for identifying predictors of UTIs. Causes of hematuria were also investigated.

RESULTS

A total of 161 patients with hematuria without pyuria were evaluated. Among symptoms, dysuria was significantly correlated with UTIs. Regarding urine biochemistry data, urine esterase and urine protein > 30 mg/dl were found to be significant parameters for predicting UTIs, while urine esterase and urine nitrite showed significant differences in children with age < 2 years. In the urine microscopic examinations, urine red blood cells (RBC) > 373/µL in children aged ≥ 2 years and urine RBC > 8/µL in children aged < 2 years were associated with UTIs. In addition, UTIs and urinary tract stones were found to be the top two causes of hematuria.

CONCLUSIONS

Dysuria, urine esterase, urine nitrite, and urine protein may be useful parameters for predicting UTIs in pediatric patients with hematuria but no pyuria in the ED. In addition, a UTI was the most commonly identified etiology of hematuria without pyuria, followed by urinary tract stones.

An Adolescent Boy With Hypoxia, Microscopic Hematuria, and Hypertension

A 13-year-old boy presented with hypoxia, microscopic hematuria, and elevated blood pressures. Persistent microscopic hematuria and hypertension led to investigation of glomerular and non-glomerular causes of hematuria. After reviewing his clinical course, family history, and laboratory testing, an additional test was sent, revealing the diagnosis.

The Effect of a Turkey Berry (Solanum torvum)-Fortified Biscuit on the Hemoglobin Level and Cognitive Performance of Adolescent Females in the Ahafo Region of Ghana: A Pilot Study

Anemia is a public health problem that affects about 50% of adolescent females in sub-Saharan Africa. Anemia can negatively affect the overall growth, cognitive performance, and productivity of school-going adolescents. This pilot study assessed the impact of Solanum torvum-fortified biscuits on hemoglobin levels and cognitive performance of school-going adolescent females. A cluster randomized controlled, open labeled trial was undertaken among four basic schools in the Ahafo Region of Ghana. Out of the 169 participants, 151 (intervention = 83, control = 68) adolescent females completed the trial. The intervention and control groups were made up of two schools each. The participants in the intervention and control groups received a total of 30 turkey berry-fortified biscuit supplementation or 30 placebos for a period of six weeks, respectively. The hemoglobin levels and cognitive test scores were obtained before and after the intervention. The number of anemic cases and low cognitive performance among the female adolescents in the intervention group reduced by 23.8% and 8.7%, respectively. There was a positive impact on the hemoglobin levels and cognitive performance of the intervention group. For every unit of turkey berry-fortified biscuit consumed by the intervention group, there was a 0.945 unit increase in hemoglobin level (p = 0.001) and a 2.796 unit increase in cognitive performance (p = 0.005). The turkey berry-fortified biscuit significantly reduced anemia prevalence and improved cognitive performance among the adolescent girls. Therefore, its potential in the management of anemia and improvement of cognition could be explored.

Pediatric Rhabdomyosarcomas of the Genitourinary Tract

Rhabdomyosarcoma (RMS) is the most common soft tissue sarcoma in the pediatric and adolescent population, with 350 new cases diagnosed each year. While they can develop anywhere in the body, the genitourinary tract is the second most common primary location for an RMS to develop. Overall survival has improved through the increased use of protocols and multidisciplinary approaches. However, the guidelines for management continue to change as systemic and radiation therapeutics advance. Given the relative rarity of this disease compared to other non-solid childhood malignancies, healthcare providers not directly managing RMS may not be familiar with their presentation and updated management. This review aims to provide foundational knowledge of the management of RMSs with an emphasis on specific management paradigms for those arising from the genitourinary tract. The genitourinary tract is the second most common location for an RMS to develop but varies greatly in symptomology and survival depending on the organ of origin. As the clinical understanding of these tumors advances, treatment paradigms have evolved. Herein, we describe the breadth of presentations for genitourinary RMSs with diagnostic and treatment management considerations, incorporating the most recently available guidelines and societal consensus recommendations.

Diagnostic Problems in C3 Glomerulopathy

Background: C3 glomerulopathies (C3GN) are a group of rare kidney diseases associated with impaired complement regulation. The effects of this disease include the accumulation of complement C3 in the kidneys. Based on the clinical data, as well as light, fluorescence, and electron microscopy results, the diagnoses were verified. The study group consisted of biopsy specimens, which were obtained from 332 patients who were diagnosed with C3 glomerulopathy. In all cases, histopathological examinations were performed; deposits of complement C3 and C1q components, as well as the immunoglobulins IgA, IgG, and IgM, were identified using immunofluorescence. Furthermore, electron microscopy was also performed. Results: The histopathological examination results presented cases of C3GN (n = 111) and dense deposit disease (DDD; n = 17). The non-classified (NC) group was the most numerous (n = 204). The lack of classification was due to the poor severity of the lesions, even on the electron microscopic examination or in the presence of intense sclerotic lesions. Conclusions: In cases of suspected C3 glomerulopathies, we believe an electron microscopy examination is necessary. This examination is beneficial in mild-to-extremely-severe cases of this glomerulopathy, where the lesions are barely discernible when using immunofluorescence microscopy.

Evaluation of Proteinuria and Hematuria in Ambulatory Setting

Proteinuria and/or hematuria are common findings in ambulatory settings. Proteinuria can be glomerular and/or tubular in origin and it may be transient, orthostatic, or persistent. Persistent proteinuria may be indicative of a serious kidney pathology. Hematuria, which denotes the presence of an increased number of red blood cells in the urine, can be gross or microscopic. Hematuria can originate from the glomeruli or other sites of the urinary tract. Asymptomatic microscopic hematuria or mild proteinuria in an otherwise healthy child is less likely to be of clinical significance. However, the presence of both requires further workup and careful monitoring.

Biomarkers of sickle cell nephropathy in Senegal

Sickle cell anemia (SCA) is caused by a single point variation in the β-globin gene (HBB): c.20A> T (p.Glu7Val), in homozygous state. SCA is characterized by sickling of red blood cells in small blood vessels which leads to a range of multiorgan complications, including kidney dysfunction. This case-control study aims at identifying sickle cell nephropathy biomarkers in a group of patients living with SCA from Senegal. A total of 163 patients living with SCA and 177 ethnic matched controls were investigated. Biological phenotyping included evaluation of glycemia, glucosuria, albuminuria, proteinuria, tubular proteinuria, serum creatinine, urine creatinine, urine specific gravity and glomerular filtration rate. Descriptive statistics of biomarkers were performed using the χ2 -test, with the significance level set at p<0.05. Patients living with SCA had a median age of 20 years (range 4 to 57) with a female sex frequency of 53.21%. The median age of the control participants was 29 years (range: 4-77) with a female sex frequency of 66.09%. The following proportions of abnormal biological indices were observed in SCA patients versus (vs.) controls, as follows: hyposthenuria: 35.3%vs.5.2% (p<0.001); glomerular hyperfiltration: 47.66%vs.19.75% (p<0.001), renal insufficiency: 5.47%vs.3.82% (p = 0.182); microalbuminuria: 42.38%vs.5.78% (p<0.001); proteinuria: 39.33%vs.4.62% (p<0.001); tubular proteinuria: 40.97%vs.4.73% (p<0.001) and microglucosuria: 22.5%vs.5.1% (p<0.001). This study shows a relatively high proportion of SCA nephropathy among patients living with SCA in Senegal. Microglucosuria, proteinuria, tubular proteinuria, microalbuminuria, hyposthenuria and glomerular hyperfiltration are the most prevalent biomarkers of nephropathy in this group of Senegalese patients with SCA.

Effects of Senegal haplotype (Xmn1-rs7412844), alpha-thalassemia (3.7kb HBA1/HBA2 deletion), NPRL3-rs11248850 and BCL11A-rs4671393 variants on sickle cell nephropathy

OBJECTIVE

Sickle cell anemia (SCA) can cause substantial kidney dysfunction resulting in sickle cell nephropathy, which may be affected by the presence of modifier genes. This study evaluates the effects of some modifier genes on sickle cell nephropathy.

METHODS

Patients living with SCA were recruited. Alpha-thalassemia (3.7kb HBA1/HBA2 deletion) was genotyped using gap PCR multiplex. Senegal haplotype (Xmn1-rs7412844), BCL11A-rs4671393 and NPRL3-rs11248850 were genotyped using Mass Array. The effects of variants on kidney dysfunction were then evaluated using multivariate analysis.

RESULTS

The number of patients living with SCA included in this study was 162 with a median age of 20 years [minimum-maximum: 4-57] and a female frequency of 53.21%. Senegal haplotype, BCL11A-rs4671393 variant were protective factors against albuminuria stage A2 with an odds ratio (OR) of 0.22 (95% CI 0.05-0.90) and 0.27 (95% CI 0.08-0.96) respectively. The combination NPRL3-rs11248850 variant - 3.7kb HBA1/HBA2 deletion was a protective factor against albuminuria stage A2 (OR = 0.087, 95% Cl 0.01-0.78) but it was a risk factor for glomerular hyperfiltration (OR = 17.69, 95% CI 1.85-169.31).

CONCLUSIONS

All four variants displayed a protective effect against albuminuria stage A2. The combination alpha-thalassemia - NPRL3-rs11248850 variant is a risk factor for glomerular hyperfiltration.

Neonatal Proteinuria in Calves-A Quantitative Approach

Simple Summary

A newborn’s survival depends on the quick adaptation of the organism to new environmental conditions. Newborn calves show high somatic maturity compared to, for example, human newborns, but their body functions with a lower efficiency than that of adult cattle. Adaptation processes concern all organs, including the kidneys, which are not morphologically mature after birth. The ongoing morphological changes imply functional alterations in the kidneys. There is an increase in blood flow through the kidneys and the glomerular filtration rate, as well as an increase in the efficiency of resorption processes of primary urine components into the blood, including proteins. Protein is present in trace amounts in the urine of healthy adults of various species. It can occur in larger amounts in the urine of sick animals, as well as in certain physiological states, e.g., in newborns. The presence of protein in the urine of newborns in the quantity exceeding 300 mg/24 h/m² is called neonatal proteinuria. The causes of proteinuria in healthy newborns have not been clearly elucidated. Many studies have focused on proteinuria in newborns and sick children and sick animals, especially dogs and cats. The present study was the first to quantify the hypothesis of the occurrence of proteinuria in healthy calves in the first week of life and to assess its intensity and dynamics, based on the analysis of changes in total protein excretion in the urine and its fractions differing in molecular weight (albumin, low molecular weight proteins (LMW) and high molecular weight proteins (HMW)). It should be noted that the analysis of excreted protein fractions is a sensitive diagnostic indicator of the type of kidney disease, e.g., increased HMW protein excretion may indicate damage to the renal glomeruli, and loss of LMW proteins may indicate renal tubular disease.

Abstract

Urine testing is a convenient, non-invasive method of obtaining information about body functions. Depending on the intended purpose, urine testing may be qualitative and/or quantitative. Urine analysis can also include proteins. There are no data in the literature on the occurrence of proteinuria in healthy neonatal calves. The present study was the first that aimed to quantify the hypothesis of proteinuria occurrence in these animals in the first week of life, to assess its intensity and dynamics and to understand the underlying causes of proteinuria in healthy calves. The research was carried out on 15 healthy calves in the first seven days of life. Calves were catheterized to determine minute diuresis. Total protein concentration was determined in blood plasma and urine. Urine proteins were separated by electrophoresis (SDSPAGE) and their concentration and percentage were determined by densitometry using an image archiving and analysis software. The separated proteins were divided into three groups according to molecular weight for albumin, LMW and HMW proteins. The results were standardized per 1 m² of body surface area and statistically analyzed. Neonatal proteinuria was demonstrated in healthy calves, mainly resulting from the high concentration of LMW proteins in the urine. Their percentages decreased significantly from 84.46% on the first day of calves’ life to 64.02% on day 7. At the same time, a statistically significant increase was observed in the proportion of albumin and high molecular weight proteins in urine total protein. Albumin percentage increased from 9.54% (on day 1) to almost 20% (on day 7), while the proportion of HMW proteins increased from 6.68% to 18.13%, respectively. The concentration of total protein in the urine of newborn calves amounted to 14.64 g/L and decreased statistically significantly during the first 72 h of postnatal life, stabilizing at the level of 3–4 g/L. The mean value of total protein excretion in the first week of life was 4.81 mg/min/m² (i.e., 6.93 g/24 h/m²). The analysis of protein concentration in the urine and its excretion, as well as changes in urinary excretion of the tested protein fractions, indicated that neonatal proteinuria in healthy neonatal calves was tubular (i.e., main reason is the reduced absorption of proteins in nephrons). In addition, research showed that there was a rapid improvement in resorptive mechanisms in tubular cells. It should be assumed that the filtration barrier in the kidneys of these animals after birth is morphologically prepared to retain high molecular weight proteins. It seems that the increased permeability of the filtration barrier in the glomeruli does not necessarily indicate the immaturity of the kidneys, but may indicate the kidneys’ adaptation to excess protein removal from the body during feeding with high-protein food (colostrum), with an open intestinal barrier enabling protein absorption from the gastrointestinal tract to the blood.

Renal function in children with a congenital solitary functioning kidney: A systematic review

INTRODUCTION

Abnormal renal development that results in lack of function or development of one of two kidneys is known as congenital solitary functioning kidney (CSFK). Two well characterized sub-categories of CFSK are unilateral renal agenesis (URA) and multicystic dysplastic kidney (MCDK). This systematic review sought to evaluate the change in renal function in children ≤18 years old with a CSFK as a result of URA or MCDK.

METHODS

A literature search in MEDLINE and Embase was conducted (1946 to July 13, 2020). All relevant articles were retrieved and evaluated based on pre-selected criteria by two independent researchers. Data was then extracted from variables of interest and conflicts were resolved by a third researcher. The primary outcome was renal function, and the secondary outcomes were proteinuria and hypertension.

RESULTS

Forty-five studies were included, of which 49% (n = 22) were retrospective and/or 58% (n = 26) were cohort studies. A combined total of 2148 and 885 patients were diagnosed with MCDK or URA, respectively. The proportion of children with worsened renal function at follow-up was found to be 8.4% (95% CI: 5.2%-13.4%). Among the studies reporting renal function as a group mean or median at follow-up, 84% (21/25) had a GFR/CrCl above 90 (mL/min/1.73  m²/ml/min). In terms of secondary outcomes, the proportion of children with proteinuria and hypertension was found to be 10.1% (95% CI: 6.9%-14.6%) and 7.4% (95% CI: 5.0%-10.9%), respectively.

CONCLUSION

The risk of developing proteinuria (10.1%), hypertension (7.4%), and/or worsened renal function (8.4%) for children with CFSK as a result of MCDK or URA is low. However, the level of evidence in the literature is weak. Further research is needed to identify the predisposing factors that may differentiate the small subset of children with CSFK at a higher risk of developing adverse renal outcomes.

Acute kidney injury and mortality in pediatric Lassa fever versus question of access to dialysis

OBJECTIVES

To assess the prevalence of acute kidney injury (AKI), and its impact on outcome in hospitalized pediatric patients with Lassa fever (LF).

METHODS

We reviewed the presenting clinical and laboratory features and outcomes of 40 successive hospitalized children with PCR-confirmed LF. The diagnosis and staging of AKI was based on KDIGO criteria. We compared groups of patients using t- or χ2 tests as necessary, and took p-values <0.05 as indicative of the presence of significant differences.

RESULTS

Sixteen (40%) children had AKI. Case fatality rate (CFR) was 9/16 (56%) in children with and 1/24 (4%) in those without AKI (OR [95% CI] of CFR associated with AKI = 29.57 [3.17, 275.7]). Presentation with abnormal bleeding (p = 0.008), encephalopathy (p = 0.004), hematuria plus proteinuria (p = 0.013), and elevated serum transaminase levels (p <0.02) were significantly associated with an increased prevalence of AKI.

CONCLUSION

AKI prevalence in hospitalized pediatric patients with Lassa fever is high, and correlated with illness severity/CFR. The high prevalence underscores the need for access to hemodialysis, and clinical presentation and/or presence of hematuria plus proteinuria could serve as a ready prompt for referral for such specialized care.

Orthostatic proteinuria: an overestimated phenomenon?

BACKGROUND

Although orthostatic proteinuria (OP) is the most common cause of childhood proteinuria, excluding transient proteinuria, data regarding prevalence and long-term prognosis are limited. We aimed to determine prevalence of OP in healthy schoolchildren evaluating relationships with age, gender and body mass index, and determine follow-up.

METHODS

A total of 1701 healthy children aged 6-15 years were selected using a population-based, stratified, cluster-sampling method; and random urine samples were taken. For proteinuria ≥ 1+ in first urine samples, second and third random samples were taken at least 2 weeks apart to exclude transient proteinuria. For continuing proteinuria after third samples, first morning urine samples were collected. Cases where proteinuria was not detected in first morning urine samples were diagnosed as OP.

RESULTS

Sixty-four of 1701 children (3.7%) had proteinuria on first random urine samples. After second and third urine samples, proteinuria persisted in only 16 (0.94%). OP was detected in 11 (0.65%). Prevalence of OP tended to decrease with increasing BMI, though not statistically significant. All 7 cases with OP who were re-evaluated later, had no proteinuria 3 years after diagnosis.

CONCLUSIONS

Prevalence of OP in our study was lower than the literature. At least three random urine samples should be taken to exclude transient proteinuria in an asymptomatic child/adolescent before making a diagnosis of OP using first morning urine samples. OP is a benign condition and resolves spontaneously in most cases. Underweight children had a tendency for OP compared with overweight and obese children; however, further studies with larger number of patients are needed.

Podocytes Produce and Secrete Functional Complement C3 and Complement Factor H

Podocytes are an important part of the glomerular filtration barrier and the key player in the development of proteinuria, which is an early feature of complement mediated renal diseases. Complement factors are mainly liver-born and present in circulation. Nevertheless, there is a growing body of evidence for additional sites of complement protein synthesis, including various cell types in the kidney. We hypothesized that podocytes are able to produce complement components and contribute to the local balance of complement activation and regulation. To investigate the relevant balance between inhibiting and activating sides, our studies focused on complement factor H (CFH), an important complement regulator, and on C3, the early key component for complement activation. We characterized human cultured podocytes for the expression and secretion of activating and regulating complement factors, and analyzed the secretion pathway and functional activity. We studied glomerular CFH and C3 expression in puromycin aminonucleoside (PAN) -treated rats, a model for proteinuria, and the physiological mRNA-expression of both factors in murine kidneys. We found, that C3 and CFH were expressed in cultured podocytes and expression levels differed from those in cultivated glomerular endothelial cells. The process of secretion in podocytes was stimulated with interferon gamma and located in the Golgi apparatus. Cultured podocytes could initiate the complement cascade by the splitting of C3, which can be shown by the generation of C3a, a functional C3 split product. C3 contributed to external complement activation. Podocyte-secreted CFH, in conjunction with factor I, was able to split C3b. Podocytes derived from a patient with a CFH mutation displayed impaired cell surface complement regulation. CFH and C3 were synthesized in podocytes of healthy C57Bl/6-mice and were upregulated in podocytes of PAN treated rats. These data show that podocytes produce functionally active complement components, and could therefore influence the local glomerular complement activation and regulation. This modulating effect should therefore be considered in all diseases where glomerular complement activation occurs. Furthermore, our data indicate a potential novel role of podocytes in the innate immune system.

Correlation of urine protein/creatinine ratios to 24-h urinary protein for quantitating proteinuria in children

BACKGROUND

The purpose of this study was to evaluate the correlation and consistency between urine protein/creatinine ratio (UPCR) and 24-h urine protein (24HUPr) in children, and to determine cutoff values of UPCR relative to 24HUPr at 100 mg/m²/d (≥ 100 mg/m²/d as pathological proteinuria) and 1000 mg/m²/d (≥ 1000 mg/m²/d as nephrotic-range proteinuria).

METHODS

Three hundred sixty-six children were enrolled, including 81 controls, 109 with Henoch-Schönlein purpura nephritis, 167 with nephrotic syndrome, 5 with IgA nephropathy, and 4 with lupus nephritis. Patients were divided into three groups: normal group; non-nephrotic-range proteinuria group; nephrotic-range proteinuria group. The cutoff values of UPCR in predicting the different levels of proteinuria were determined using ROC curve analysis.

RESULTS

UPCR was positively correlated with 24HUPr (r = 0.915, p < 0.01). Bland-Altman diagrams showed that UPCR and 24HUPr had good consistency, and > 95% spots of UPCR and 24HUPr were within 95% confidence intervals. Relative to 24HUPr at 100 mg/m²/d, the cutoff value of UPCR (0.18 g/g Cr) had the highest sensitivity (94%) and specificity (98.8%) which is close to 0.2 g/g Cr as proposed by the American College of Rheumatology. Relative to 24HUPr at 1000 mg/m²/d, the cutoff value of UPCR (2.09 g/g Cr) had the highest sensitivity (92.1%) and specificity (92.1%) which is close to the 2.0 g/g Cr proposed in KDIGO guidelines.

CONCLUSIONS

UPCR showed strong correlation and consistency with 24HUPr for evaluating levels of proteinuria in children. UPCR < 0.2 g/g Cr can be considered a criterion for normal-range proteinuria. Instead of 24HUPr ≥ 1000 mg/m²/d, UPCR ≥ 2.0 g/g Cr can be considered a criterion for nephrotic-range proteinuria or nephrotic syndrome in children.