Pattern of clinical presentation of congenital anomalies of the kidney and urinary tract among infants and children

Congenital anomalies of the kidney and urinary tract (CAKUT) in critically ill infants: a multicenter cohort study

BACKGROUND

The aim of the study was to determine the prevalence of congenital anomalies of the kidney and urinary tract (CAKUT) in the neonatal intensive care unit (NICU) and to evaluate risk factors associated with worse outcomes. We hypothesized that infants with CAKUT with extra-renal manifestations have higher mortality.

METHODS

This is a cohort study of all inborn infants who were diagnosed with any form of CAKUT discharged from NICUs managed by the Pediatrix Medical Group from 1997 to 2018. Logistic and linear regression models were used to analyze risk factors associated with in-hospital mortality.

RESULTS

The prevalence of CAKUT was 1.5% among infants hospitalized in 419 NICUs. Among the 13,383 infants with CAKUT analyzed, median gestational age was 35 (interquartile range [IQR] 31-38) weeks and median birth weight was 2.34 (IQR 1.54-3.08) kg. Overall in-hospital mortality for infants with CAKUT was 6.8%. Oligohydramnios (adjusted odds ratio [aOR] 4.5, 95% confidence interval [CI] 2.2-9.1, p < 0.001), extra-renal anomalies (aOR 2.5, 95% CI 2.0-3.1, p < 0.001), peak SCr (aOR 1.02, 95% CI 1.01-1.03, p < 0.001) and exposure to nephrotoxic medications (aOR 1.4, 95% CI 1.1-1.7, p = 0.01) were associated with increased mortality, while a history of urological surgery or intervention was associated with lower mortality (aOR 0.6, 95% CI 0.4-0.7, p < 0.001).

CONCLUSIONS

Infants hospitalized in the NICU who have CAKUT and the independent risk factors for mortality (e.g., oligohydramnios and presence of extra-renal anomalies) require close monitoring, minimizing of exposure to nephrotoxic drugs, and timely urological surgery or intervention. A higher resolution version of the Graphical abstract is available as Supplementary information.

Copy Number Variation Analysis Facilitates Identification of Genetic Causation in Patients with Congenital Anomalies of the Kidney and Urinary Tract

Background

Congenital anomalies of the kidneys and urinary tract (CAKUT) are the most common cause of chronic kidney disease among children and adults younger than 30 yr. In our previous study, whole-exome sequencing (WES) identified a known monogenic cause of isolated or syndromic CAKUT in 13% of families with CAKUT. However, WES has limitations and detection of copy number variations (CNV) is technically challenging, and CNVs causative of CAKUT have previously been detected in up to 16% of cases.

Objective

To detect CNVs causing CAKUT in this WES cohort and increase the diagnostic yield.

Design setting and participants

We performed a genome-wide single nucleotide polymorphism (SNP)-based CNV analysis on the same CAKUT cohort for whom WES was previously conducted.

Outcome measurements and statistical analysis

We evaluated and classified the CNVs using previously published predefined criteria.

Results and limitations

In a cohort of 170 CAKUT families, we detected a pathogenic CNV known to cause CAKUT in nine families (5.29%, 9/170). There were no competing variants on genome-wide CNV analysis or WES analysis. In addition, we identified novel likely pathogenic CNVs that may cause a CAKUT phenotype in three of the 170 families (1.76%).

Conclusions

CNV analysis in this cohort of 170 CAKUT families previously examined via WES increased the rate of diagnosis of genetic causes of CAKUT from 13% on WES to 18% on WES + CNV analysis combined. We also identified three candidate loci that may potentially cause CAKUT.

Patient summary

We conducted a genetics study on families with congenital anomalies of the kidney and urinary tract (CAKUT). We identified gene mutations that can explain CAKUT symptoms in 5.29% of the families, which increased the percentage of genetic causes of CAKUT to 18% from a previous study, so roughly one in five of our patients with CAKUT had a genetic cause. These analyses can help patients with CAKUT and their families in identifying a possible genetic cause.

Overview of pediatric kidney transplantation

Kidney transplantation is the treatment of choice for pediatric patients with end-stage kidney disease. Unlike adult recipients undergoing transplantation, special considerations must be taken when transplanting children based on the underlying etiology of kidney disease, previous surgical procedures, anatomical limitations and necessary technical adjustments. Additionally, the choice of donor must be measured to ensure optimal graft survival given a longer post-transplant life expectancy. Those topics as well as frequently encountered postoperative complications are also discussed in this publication.

Role of Actionable Genes in Pursuing a True Approach of Precision Medicine in Monogenic Diabetes

Monogenic diabetes is a genetic disorder caused by one or more variations in a single gene. It encompasses a broad spectrum of heterogeneous conditions, including neonatal diabetes, maturity onset diabetes of the young (MODY) and syndromic diabetes, affecting 1-5% of patients with diabetes. Some of these variants are harbored by genes whose altered function can be tackled by specific actions ("actionable genes"). In suspected patients, molecular diagnosis allows the implementation of effective approaches of precision medicine so as to allow individual interventions aimed to prevent, mitigate or delay clinical outcomes. This review will almost exclusively concentrate on the clinical strategy that can be specifically pursued in carriers of mutations in "actionable genes", including ABCC8, KCNJ11, GCK, HNF1A, HNF4A, HNF1B, PPARG, GATA4 and GATA6. For each of them we will provide a short background on what is known about gene function and dysfunction. Then, we will discuss how the identification of their mutations in individuals with this form of diabetes, can be used in daily clinical practice to implement specific monitoring and treatments. We hope this article will help clinical diabetologists carefully consider who of their patients deserves timely genetic testing for monogenic diabetes.

Influence of genetic polymorphism in renin-angiotensin system-candidate genes on urinary trefoil family factor 3 levels in children with congenital anomalies of kidney and urinary tract

BACKGROUND

This cross-sectional study aimed to determine the influence of genetic polymorphism in two renin-angiotensin system (RAS)-candidate genes on urinary trefoil family factor 3 (TFF3) levels in children with congenital anomalies of kidney and urinary tract (CAKUT).

METHODS

The study included fifty children with CAKUT (PUV, VUR, and PUJO) and twenty age-matched controls. Urinary TFF3 levels were measured by enzyme-linked immunosorbent assay. Detection of genetic polymorphisms in two genes, i.e., I/D polymorphism (SNP at rs4340) in angiotensin-converting enzyme (ACE) and A/T polymorphism in the angiotensin II receptor type-2 (AT2R) due to point mutation at rs3736556 was performed by polymerase chain reaction. Progressive deterioration in kidney function was defined as fall in GFR to < 60 ml/min/1.73 m² and/or progressive scarring.

RESULTS

In our cohort, the genotypic distribution of patients and controls showed no difference. Progressive functional deterioration was significantly associated with the presence of D allele (p = 0.0004), A allele (p = 0.005), and both (p < 0.0001) in patients. Significantly raised TFF3 levels were detected in the urine of children having D allele (D/D > I/D > I/I; p < 0.0001) and A allele (A/A > A/T > TT; p < 0.0001). Also, children with both D/D and A/A allelic genotypes had significantly elevated urinary TFF3 compared to those having either of them.

CONCLUSIONS

The presence of D allele and/or A allele is significantly associated with progressive functional deterioration and elevated urinary TFF3 levels. These findings support the role of angiotensin II-AT2R-NF-κB interaction in progressive deterioration of kidney function and subsequent TFF3 expression in CAKUT.

Egyptian pediatric clinical practice guidelines for urinary tract infections in infants and children (evidence based)

Background

National evidence-based recommendations for diagnosis, treatment, imaging, and follow-up in urinary tract infection are crucial being a major health problem in pediatrics. Every region should follow international recommendations with respect to the disease local profile and available facilities for that area.

Methods

Based on AGREE II (the assessment tool of practice guidelines), Egyptian CGLs used *American Academy Pediatrics, *European Association Urology, European Society Pediatric Urology, and *Asian Association Urinary tract infections as its evidence-based references. Health questions were listed for evidence base answers adopted from selected CGLs after their permission. Key statements were approved by all members and further approved by the Egyptian Pediatric Guidelines Committee after local and international external peer reviewing.

Results

(1) Diagnosis recommendations: Urine culture with diagnostic colony counts is essential for diagnosis. Catheter samples are important for critical cases and non-toilet-trained cases especially when they show significant bacteriuria and pyuria. (2) Treatment plan included areas of debate as choice of antibiotic, oral versus intravenous, duration, antibiotic prophylaxis considering age, disease severity, recurrence, + risk factors, and imaging reports. (3) Imaging recommendations were tailored to suit our community. Renal bladder ultrasound is important for children with febrile UTI, due to the high prevalence of congenital anomalies of the kidney and urinary tract, paucity of prenatal ultrasound, and lack of medical documentation to reflect previously diagnosed UTI or US reports. We recommend renal isotopic scan and voiding cystography for serious presentation, high-risk factors, recurrence, and abnormal US. (4) Urological consultation is recommended: in urosepsis or obstruction, male infants < 6 months. Acute basal DMSA is recommended in congenital renal hypodysplasia. Six months post-infection, US and DMSA are recommended in severe pyelonephritis and vesico-ureteric reflux, where those with abnormal US or DMSA or both should have voiding cystography. (5) Follow-up recommendations include family orientation with hazards of noncompliance and monitoring at pregnancy.

Conclusion

Diagnosis and treatment show strong recommendations. Imaging depends on patient assessment. Referral to a pediatric nephrologist and urologist in complicated cases is crucial. Follow-up after the age of 16 years in adult clinics is important.

A homozygous HOXA11 variation as a potential novel cause of autosomal recessive congenital anomalies of the kidney and urinary tract

Congenital anomalies of the kidney and urinary tract (CAKUT) is the leading cause of end-stage kidney disease in children. Until now, more than 50 monogenic causes for CAKUT have been described, all of which only explain 10% to 20% of all patients with CAKUT, suggesting the presence of additional genes that cause CAKUT when mutated. Herein, we report two siblings of a consanguineous family with CAKUT, both of which rapidly progressed to chronic kidney disease in early childhood. Whole-exome sequencing followed by homozygosity mapping identified a homozygous variation in HOXA11. We therefore showed for the first time an association between a homozygous HOXA11 variation with CAKUT in humans, expanding the genetic spectrum of the disease.

Urinary biomarkers as point-of-care tests for predicting progressive deterioration of kidney function in congenital anomalies of kidney and urinary tract: trefoil family factors (TFFs) as the emerging biomarkers

BACKGROUND

Children with congenital anomalies of kidney and urinary tract (CAKUT) are at high risk of progressive deterioration of kidney function and further developing stage 5 chronic kidney disease (CKD 5), even after a successful surgery. This prospective study was designed to determine whether urinary biomarkers can predict progressive deterioration of kidney function in children with CAKUT.

METHODS

The study included 50 consecutive children, aged < 14 years, who were diagnosed with congenital uropathies (PUV, VUR, and PUJO) and 20 age-matched controls. Examination of four urinary biomarkers, i.e., trefoil family factors (TFF) 1 and 3, neutrophil gelatinase-associated lipocalin (NGAL) and microalbuminuria (MALB) was done at the beginning of follow-up. Kidney function was assessed, at the beginning and after 12-months of follow-up, by technetium-99m diethylene triamine pentaacetic acid (DTPA) and technetium-99m dimercaptosuccinic acid (DMSA) scans. Progressive deterioration in the kidney function was defined as a fall in the GFR from ≥ 60 to < 60 ml/min/1.73 m² on comparing the baseline and latest DTPA scans; and/or new-onset cortical scar/scars or increase in the size of previous scar/scars on serial DMSA scans. Group 1 and group 2 included children without and with progressive functional deterioration respectively.

RESULTS

The median (IQR) age of children with CAKUT and controls was 3 (1.5-5) and 2.3 (1.2-3.6) years, respectively, and showed no significant difference (p = 0.29). Median concentrations of TFF1, TFF3, NGAL, and microalbumin in patients were 44.5, 176.5, 281.2, and 15.5 mcg/gCr, respectively, and were significantly elevated as compared to controls (p < 0.05). Children belonging to group 2 had significantly higher concentration of biomarkers as compared to those in group 1. TFF3 was found have the highest AUC (0.9198) on ROC curve for predicting progressive functional deterioration.

CONCLUSION

Urinary TFFs, NGAL, and microalbumin significantly correlate with progressive deterioration of kidney function in children harboring CAKUT. TFF3, with the strongest prediction of functional deterioration, is an emerging peptide showing sufficient potential to be included in the biomarker panel. Graphical abstract.

Screening of renal anomalies in first-degree relatives of children diagnosed with non-syndromic congenital anomalies of kidney and urinary tract

BACKGROUND

Non-syndromic congenital anomalies of kidney and urinary tract (CAKUT) are usually sporadic in nature but familial clustering of cases have been observed suggesting a genetic predisposition to this condition. We aimed to determine the frequency and pattern of renal anomalies in first-degree relatives of children with non-syndromic CAKUT.

METHODS

We screened all the first-degree relatives of children with CAKUT. A total of 149 first-degree relatives, belonging to 62 families were screened with ultrasonography.

RESULTS

A renal anomaly was detected in 9 out of the 62 families. Two of these nine families had identical anomalies (child and a parent) indicating single-gene disorders with possible autosomal dominant inheritance, while the rest of families had a non-identical anomaly. The anomalies detected in the first-degree relatives were renal hypodysplasia (n = 2), multicystic dysplastic kidney (n = 3), pelviureteric junction obstruction (n = 2) and mild hydronephrosis (n = 2). The incidence of a sonographically detected anatomic renal anomaly in first-degree relatives of children with CAKUT was found to be 6.0%. Familial cystic kidney disease was found in two out of the 4 families with cystic kidney disease.

CONCLUSION

Significant renal anomalies were identified in first-degree relatives of children with non-syndromic CAKUT and hence, attempts must be made to screen the family members of children with non-syndromic CAKUT.

Phenotype expansion of heterozygous FOXC1 pathogenic variants toward involvement of congenital anomalies of the kidneys and urinary tract (CAKUT)

PURPOSE

Congenital anomalies of the kidney and urinary tract (CAKUT) are the most common cause of chronic kidney disease in childhood and adolescence. We aim to identify novel monogenic causes of CAKUT.

METHODS

Exome sequencing was performed in 550 CAKUT-affected families.

RESULTS

We discovered seven FOXC1 heterozygous likely pathogenic variants within eight CAKUT families. These variants are either never reported, or present in <5 alleles in the gnomAD database with ~141,456 controls. FOXC1 is a causal gene for Axenfeld-Rieger syndrome type 3 and anterior segment dysgenesis 3. Pathogenic variants in FOXC1 have not been detected in patients with CAKUT yet. Interestingly, mouse models for Foxc1 show severe CAKUT phenotypes with incomplete penetrance and variable expressivity. The FOXC1 variants are enriched in the CAKUT cohort compared with the control. Genotype-phenotype correlations showed that Axenfeld-Rieger syndrome or anterior segment dysgenesis can be caused by both truncating and missense pathogenic variants, and the missense variants are located at the forkhead domain. In contrast, for CAKUT, there is no truncating pathogenic variant, and all variants except one are located outside the forkhead domain.

CONCLUSION

We thereby expanded the phenotype of FOXC1 pathogenic variants toward involvement of CAKUT, which can potentially be explained by allelism.

DCHS1 DNA copy number loss associated with pediatric urinary tract infection risk

Urinary tract infections (UTI), associated with vesicoureteral reflux (VUR), can lead to chronic kidney disease. Genetic alterations in the innate immune defenses contribute to UTI risk. We investigated a novel gene, Dachsous Cadherin-Related 1 (DCHS1), in children with UTI. We determined absolute DNA copy number (CN) of DCHS1 in children with UTI. In this case-control study, we utilized multiple complementary methods to determine the genomic CN of DCHS1. Children with (n = 370) and without (n = 71) VUR from two well-phenotyped clinical trials of UTI were copy-typed and compared to 491 healthy controls with no known history of VUR or UTI. Less than 1% of controls had a single copy of DCHS1, while 31% of children with UTI and no VUR and 7% of children with UTI and VUR had a single copy of the DCHS1 gene. Using immunostaining, we localized expression postnatally to the bladder and renal epithelia. Mice were also challenged with two uropathogenic Escherichia coli strains, and Dchs1 mRNA was quantified. This study represents the first report of DCHS1 in association with pediatric UTI. We hypothesize that its role in innate immunity is critical to lower urinary tract defense. Further investigation is required to determine the role of DCHS1 in innate immunity.

Factors Associated With the Development of Chronic Kidney Disease in Children With Congenital Anomalies of the Kidney and Urinary Tract

Congenital anomalies of the kidney and urinary tract (CAKUT) are the most common cause of end-stage renal disease in children and adolescents. The diversity of the malformations summarized by CAKUT is high and there are numerous associated syndromes. The genetic background of these malformations remains unknown in the majority of cases. The aim of this study was to evaluate factors associated with the development of chronic kidney disease (CKD) and underlying genetic aberrations in children and adolescents with CAKUT. For this purpose, data from patients with CAKUT presented at the pediatric nephrology outpatient clinic were analyzed in a cross-sectional single-center study. Among the 405 patients, the commonest findings related to CAKUT were renal hypoplasia/dysplasia (65%), followed by hydronephrosis (43%). Forty-four percent of the patients were suffering from CKD, 6% were ranked as end-stage renal disease. In the univariate analysis, male gender and premature birth were associated with higher CKD stages (p = 0.004 resp. p < 0.001). Children with an abnormal prenatal ultrasound had more often a glomerular filtration rate of <30 ml/min/1.73 m² (p = 0.004). Patients with urinary tract infections as first symptom whereas had significant lower CKD stages (p = 0,006). In the multivariate analysis, premature birth (p = 0.033) and urinary tract infection as the first symptom (p = 0.043) were significantly associated with CKD stage ≥ II. Among the 16% of the children who have undergone genetic analyses the most frequent genetic aberration was a mutation in HNF1β-gene. These results can be used for the care of patients with CAKUT subject to factors associated with developing CKD.

Mental health and psychosocial adjustment in pediatric chronic kidney disease derived from the KNOW-Ped CKD study

BACKGROUND

Psychosocial development of pediatric chronic kidney disease (CKD) patients is substantially affected due to growth retardation, frequent school absences, and difficulties engaging in normal peer relationship activities. While many studies focus on specific issues such as depression, anxiety, or neurocognitive function, few evaluate prevalence of various types of mental health and psychosocial adjustment problems among children with CKD. This study aimed to investigate these within the KoreaN cohort study for Outcomes in patients With Pediatric Chronic Kidney Disease (KNOW-Ped CKD).

METHODS

One hundred sixty-six subjects who completed the Korean-Child Behavioral Checklist (K-CBCL) were included. The clinical group comprised subjects with scores indicating psychosocial adjustment or mental health problems using the T scores for the 14 subscales of the K-CBCL. We analyzed associations between mental health or adjustment problems in pediatric CKD and each variable.

RESULTS

Mean age was 11.1 (± 3.9) years, number of males was 117 (70.5%), and 20.5% and 22.3% of children had significant mental health problems and psychosocial adjustment problems, respectively. Overall, 33.1% were assigned to the clinical group, and exhibited short stature and higher rates of preterm birth history compared to the non-clinical group. Subjects with adjustment problems had higher comorbidities such as CNS disease, developmental delay, cardiovascular disease, and multi-organ involvement. Logistic regression analysis revealed preterm birth and developmental delay correlated highly with clinical group.

CONCLUSIONS

A significant proportion of children and adolescents with CKD experience mental health and adjustment problems. In particular, patients with developmental delay or preterm birth history require screening and targeted follow-up.

COL4A1 mutations as a potential novel cause of autosomal dominant CAKUT in humans

Congenital anomalies of the kidney and urinary tract (CAKUT) are the most common cause of chronic kidney disease (~ 45%) that manifests before 30 years of age. The genetic locus containing COL4A1 (13q33-34) has been implicated in vesicoureteral reflux (VUR), but mutations in COL4A1 have not been reported in CAKUT. We hypothesized that COL4A1 mutations cause CAKUT in humans. We performed whole exome sequencing (WES) in 550 families with CAKUT. As negative control cohorts we used WES sequencing data from patients with nephronophthisis (NPHP) with no genetic cause identified (n = 257) and with nephrotic syndrome (NS) due to monogenic causes (n = 100). We identified a not previously reported heterozygous missense variant in COL4A1 in three siblings with isolated VUR. When examining 549 families with CAKUT, we identified nine additional different heterozygous missense mutations in COL4A1 in 11 individuals from 11 unrelated families with CAKUT, while no COL4A1 mutations were identified in a control cohort with NPHP and only one in the cohort with NS. Most individuals (12/14) had isolated CAKUT with no extrarenal features. The predominant phenotype was VUR (9/14). There were no clinical features of the COL4A1-related disorders (e.g., HANAC syndrome, porencephaly, tortuosity of retinal arteries). Whereas COL4A1-related disorders are typically caused by glycine substitutions in the collagenous domain (84.4% of variants), only one variant in our cohort is a glycine substitution within the collagenous domain (1/10). We identified heterozygous COL4A1 mutations as a potential novel autosomal dominant cause of CAKUT that is allelic to the established COL4A1-related disorders and predominantly caused by non-glycine substitutions.

Clinico-Biochemical Profile of Children with Congenital Anomalies of the Kidney and Urinary Tract: A Cross-Sectional Study

Background

Congenital anomalies of the kidney and urinary tract (CAKUT) are a group of disorders responsible for the majority of pediatric end-stage renal disease cases. There are only a few studies on CAKUT.

Objectives

A study was conducted to determine the clinical and biochemical profile of children with CAKUT and to estimate the prevalence and the factors associated with hypertension in CAKUT.

Methods

A cross-sectional study was conducted in a tertiary center for 18 months from March 2014 to August 2015. Demographic data were recorded, and clinical examination including blood pressure measurement was performed. Various biochemical parameters including plasma renin activity (PRA), urinary beta-2-microglobulin (B2M), and microalbuminuria were evaluated.

Results

A total of 81 patients with CAKUT were studied. Twenty-two (27%) patients were underweight, 4 (5%) patients were stunted, and 26 (32%) were both underweight and stunted. Children with bilateral disease had a higher incidence of underweight (21/44 vs. 8/37; p = 0.04; 95% CI; Fisher exact test), and both underweight and stunted (25/44 vs. 10/37; p = 0.006; 95% CI; Fisher exact test) compared to children with unilateral disease. Hypertension was found in 27% cases. No association was found between hypertension and PRA, BM2, or microalbuminuria in our study. PRA was inversely proportional to the estimated glomerular filtration rate (eGFR) (Pearson test; 95% CI; p = 0.006).

Conclusions

Bilateral disease in CAKUT was significantly associated with poor somatic growth. PRA was inversely proportional to eGFR. The prevalence of hypertension was higher in children with CAKUT than in normal children and is possibly multifactorial as it was not associated with elevated PRA, B2M, or microalbuminuria.

Whole-Exome Sequencing Identifies Causative Mutations in Families with Congenital Anomalies of the Kidney and Urinary Tract

BACKGROUND

Congenital anomalies of the kidney and urinary tract (CAKUT) are the most prevalent cause of kidney disease in the first three decades of life. Previous gene panel studies showed monogenic causation in up to 12% of patients with CAKUT.

METHODS

We applied whole-exome sequencing to analyze the genotypes of individuals from 232 families with CAKUT, evaluating for mutations in single genes known to cause human CAKUT and genes known to cause CAKUT in mice. In consanguineous or multiplex families, we additionally performed a search for novel monogenic causes of CAKUT.

RESULTS

In 29 families (13%), we detected a causative mutation in a known gene for isolated or syndromic CAKUT that sufficiently explained the patient's CAKUT phenotype. In three families (1%), we detected a mutation in a gene reported to cause a phenocopy of CAKUT. In 15 of 155 families with isolated CAKUT, we detected deleterious mutations in syndromic CAKUT genes. Our additional search for novel monogenic causes of CAKUT in consanguineous and multiplex families revealed a potential single, novel monogenic CAKUT gene in 19 of 232 families (8%).

CONCLUSIONS

We identified monogenic mutations in a known human CAKUT gene or CAKUT phenocopy gene as the cause of disease in 14% of the CAKUT families in this study. Whole-exome sequencing provides an etiologic diagnosis in a high fraction of patients with CAKUT and will provide a new basis for the mechanistic understanding of CAKUT.

Current evidence on the use of anti-RAAS agents in congenital or acquired solitary kidney

RATIONAL

The inhibition of renin-angiotensin-aldosterone system (RAAS) is a major strategy for slowing the progression of chronic kidney disease (CKD). The utility of anti-RAAS agents in patients with congenital or acquired solitary kidney is still controversial.

OBJECTIVE

A systematic literature review was conducted.

MAIN FINDINGS

The conclusions of the few available studies on the topic are homogeneously in agreement with a long-term reno-protective activity of anti-RAAS drugs in patients with solitary kidney, especially if patients are hypertensive or proteinuric. However, angiotensin 2 (ANG2) levels permit a functional adaptation to a reduced renal mass in adults and is crucial for sustaining complete kidney development and maturation in children. A hormonal interference on ANG2 levels has been supposed in women. Consequently, at least in children and women, the use of ARBs appears more appropriate. Principle conclusions: Available data on this topic are limited; however, by their overall assessment, it would appear that anti-RAAS drugs might also be reno-protective in patients with solitary kidney. The use of ARBs, especially in children and in women, seems to be more appropriate. However, more experimental data would be strictly necessary to confirm this hypothesis.

16p11.2 transcription factor MAZ is a dosage-sensitive regulator of genitourinary development

Genitourinary (GU) birth defects are among the most common yet least studied congenital malformations. Congenital anomalies of the kidney and urinary tract (CAKUTs) have high morbidity and mortality rates and account for ∼30% of structural birth defects. Copy number variation (CNV) mapping revealed that 16p11.2 is a hotspot for GU development. The only gene covered collectively by all of the mapped GU-patient CNVs was MYC-associated zinc finger transcription factor (MAZ), and MAZ CNV frequency is enriched in nonsyndromic GU-abnormal patients. Knockdown of MAZ in HEK293 cells results in differential expression of several WNT morphogens required for normal GU development, including Wnt11 and Wnt4. MAZ knockdown also prevents efficient transition into S phase, affects transcription of cell-cycle regulators, and abrogates growth of human embryonic kidney cells. Murine Maz is ubiquitously expressed, and a CRISPR-Cas9 mouse model of Maz deletion results in perinatal lethality with survival rates dependent on Maz copy number. Homozygous loss of Maz results in high penetrance of CAKUTs, and Maz is haploinsufficient for normal bladder development. MAZ, once thought to be a simple housekeeping gene, encodes a dosage-sensitive transcription factor that regulates urogenital development and contributes to both nonsyndromic congenital malformations of the GU tract as well as the 16p11.2 phenotype.

A homozygous missense variant in VWA2, encoding an interactor of the Fraser-complex, in a patient with vesicoureteral reflux

Congenital anomalies of the kidney and urinary tract (CAKUT) are the most common cause (40-50%) of chronic kidney disease (CKD) in children. About 40 monogenic causes of CAKUT have so far been discovered. To date less than 20% of CAKUT cases can be explained by mutations in these 40 genes. To identify additional monogenic causes of CAKUT, we performed whole exome sequencing (WES) and homozygosity mapping (HM) in a patient with CAKUT from Indian origin and consanguineous descent. We identified a homozygous missense mutation (c.1336C>T, p.Arg446Cys) in the gene Von Willebrand factor A domain containing 2 (VWA2). With immunohistochemistry studies on kidneys of newborn (P1) mice, we show that Vwa2 and Fraser extracellular matrix complex subunit 1 (Fras1) co-localize in the nephrogenic zone of the renal cortex. We identified a pronounced expression of Vwa2 in the basement membrane of the ureteric bud (UB) and derivatives of the metanephric mesenchyme (MM). By applying in vitro assays, we demonstrate that the Arg446Cys mutation decreases translocation of monomeric VWA2 protein and increases translocation of aggregated VWA2 protein into the extracellular space. This is potentially due to the additional, unpaired cysteine residue in the mutated protein that is used for intermolecular disulfide bond formation. VWA2 is a known, direct interactor of FRAS1 of the Fraser-Complex (FC). FC-encoding genes and interacting proteins have previously been implicated in the pathogenesis of syndromic and/or isolated CAKUT phenotypes in humans. VWA2 therefore constitutes a very strong candidate in the search for novel CAKUT-causing genes. Our results from in vitro experiments indicate a dose-dependent neomorphic effect of the Arg446Cys homozygous mutation in VWA2.

PBX1 haploinsufficiency leads to syndromic congenital anomalies of the kidney and urinary tract (CAKUT) in humans

BACKGROUND

Congenital anomalies of the kidney and urinary tract (CAKUT) represent a significant healthcare burden since it is the primary cause of chronic kidney in children. CNVs represent a recurrent molecular cause of CAKUT but the culprit gene remains often elusive. Our study aimed to define the gene responsible for CAKUT in patients with an 1q23.3q24.1 microdeletion.

METHODS

We describe eight patients presenting with CAKUT carrying an 1q23.3q24.1 microdeletion as identified by chromosomal microarray analysis (CMA). Clinical features were collected, especially the renal and urinary tract phenotype, and extrarenal features. We characterised PBX1 expression and localisation in fetal and adult kidneys using quantitative RT-PCR and immunohistochemistry.

RESULTS

We defined a 276-kb minimal common region (MCR) that only overlaps with the PBX1 gene. All eight patients presented with syndromic CAKUT. CAKUT were mostly bilateral renal hypoplasia (75%). The most frequent extrarenal symptoms were developmental delay and ear malformations. We demonstrate that PBX1 is strongly expressed in fetal kidneys and brain and expression levels decreased in adult samples. In control fetal kidneys, PBX1 was localised in nuclei of medullary, interstitial and mesenchymal cells, whereas it was present in endothelial cells in adult kidneys.

CONCLUSIONS

Our results indicate that PBX1 haploinsufficiency leads to syndromic CAKUT as supported by the Pbx1-null mice model. Correct PBX1 dosage appears to be critical for normal nephrogenesis and seems important for brain development in humans. CMA should be recommended in cases of fetal renal anomalies to improve genetic counselling and pregnancy management.

Exome Sequencing Discerns Syndromes in Patients from Consanguineous Families with Congenital Anomalies of the Kidneys and Urinary Tract

Congenital anomalies of the kidneys and urinary tract (CAKUT) are the leading cause of CKD in children, featuring a broad variety of malformations. A monogenic cause can be detected in around 12% of patients. However, the morphologic clinical phenotype of CAKUT frequently does not indicate specific genes to be examined. To determine the likelihood of detecting causative recessive mutations by whole-exome sequencing (WES), we analyzed individuals with CAKUT from 33 different consanguineous families. Using homozygosity mapping and WES, we identified the causative mutations in nine of the 33 families studied (27%). We detected recessive mutations in nine known disease-causing genes: ZBTB24, WFS1, HPSE2, ATRX, ASPH, AGXT, AQP2, CTNS, and PKHD1 Notably, when mutated, these genes cause multiorgan syndromes that may include CAKUT as a feature (syndromic CAKUT) or cause renal diseases that may manifest as phenocopies of CAKUT. None of the above monogenic disease-causing genes were suspected on clinical grounds before this study. Follow-up clinical characterization of those patients allowed us to revise and detect relevant new clinical features in a more appropriate pathogenetic context. Thus, applying WES to the diagnostic approach in CAKUT provides opportunities for an accurate and early etiology-based diagnosis and improved clinical management.

Signs and symptoms of developmental abnormalities of the genitourinary tract

OBJECTIVE

The abnormalities of the genitourinary tract development are the leading cause of chronic kidney disease (CKD) in children. The diagnosis of this disease in Brazil is late and incomplete, which results in increased morbidity and mortality in this age group. Early diagnosis of this condition is the prerogative of generalist pediatricians, and the aim of this study was to review the clinical signs and symptoms associated with developmental abnormalities of the genitourinary tract.

DATA SOURCES

Based on the description of a symbolic clinical case, the authors conducted a non-systematic review of medical literature.

DATA SYNTHESIS

The results suggest that the following data should be used as a warning for early diagnosis of affected children: (a) combined urinary tract abnormalities (chromosomal abnormalities; sequence of malformations [VACTERLand Prune-Belly]; and musculoskeletal, digestive tract, heart, and nervous system malformations); (b) previous history (congenital anomalies of the kidney and urinary tract [CAKUT] in the family, low birth weight, and oligoamnios); (c) clinical signs (polyuria/nocturia, urinary tract infection, systemic arterial hypertension, failure to thrive, weak urinary stream, difficulty to start urination, distended bladder, non-monosymptomatic enuresis, urinary/urge incontinence, and bowel and bladder dysfunction); and (d) pre- and postnatal ultrasonographic alterations (increased anteroposterior diameter of the renal pelvis, mainly in the third trimester of pregnancy; single kidney; hydronephrosis associated with other abnormalities; and hydronephrosis with parenchymal involvement in the post-neonatal assessment).

CONCLUSION

The suggestions shown here can help the pediatrician to establish clinical hypotheses for the early diagnosis of developmental abnormalities of the genitourinary tract without resorting to expensive and invasive procedures.

Update on Multicystic Dysplastic Kidney

Multicystic dysplastic kidney (MCDK) is the most common cause of cystic disease in children. It is characterized by multiple non-communicating cysts of varying sizes with no identifiable normal renal parenchyma. The incidence ranges from 1 in 1000 to 4300 live births, and it is one of the most commonly detected anomalies on prenatal ultrasound. MCDK has been shown to follow a benign course with relatively few sequelae and therefore should be managed conservatively. Currently, the key clinical questions revolve around the detection of anomalies in the contralateral kidney and follow-up imaging. The recent literature suggests that very limited radiographic evaluation of the MCDK is needed. The use of voiding cystourethrogram or nuclear medicine renal scans should be directed by any abnormalities on renal ultrasound or the development of urinary tract infections.

Multi-modality imaging review of congenital abnormalities of kidney and upper urinary tract

Congenital abnormalities of the kidney and urinary tract (CAKUT) include a wide range of abnormalities ranging from asymptomatic ectopic kidneys to life threatening renal agenesis (bilateral). Many of them are detected in the antenatal or immediate postnatal with a significant proportion identified in the adult population with varying degree of severity. CAKUT can be classified on embryological basis in to abnormalities in the renal parenchymal development, aberrant embryonic migration and abnormalities of the collecting system. Renal parenchymal abnormalities include multi cystic dysplastic kidneys, renal hypoplasia, number (agenesis or supernumerary), shape and cystic renal diseases. Aberrant embryonic migration encompasses abnormal location and fusion anomalies. Collecting system abnormalities include duplex kidneys and Pelvi ureteric junction obstruction. Ultrasonography (US) is typically the first imaging performed as it is easily available, non-invasive and radiation free used both antenatally and postnatally. Computed tomography (CT) and magnetic resonance imaging (MRI) are useful to confirm the ultrasound detected abnormality, detection of complex malformations, demonstration of collecting system and vascular anatomy and more importantly for early detection of complications like renal calculi, infection and malignancies. As CAKUT are one of the leading causes of end stage renal disease, it is important for the radiologists to be familiar with the varying imaging appearances of CAKUT on US, CT and MRI, thereby helping in prompt diagnosis and optimal management.

Hepatocyte Nuclear Factor 1β-Associated Kidney Disease: More than Renal Cysts and Diabetes

Hepatocyte nuclear factor 1β (HNF1β)-associated disease is a recently recognized clinical entity with a variable multisystem phenotype. Early reports described an association between HNF1B mutations and maturity-onset diabetes of the young. These patients often presented with renal cysts and renal function decline that preceded the diabetes, hence it was initially referred to as renal cysts and diabetes syndrome. However, it is now evident that many more symptoms occur, and diabetes and renal cysts are not always present. The multisystem phenotype is probably attributable to functional promiscuity of the HNF1β transcription factor, involved in the development of the kidney, urogenital tract, pancreas, liver, brain, and parathyroid gland. Nephrologists might diagnose HNF1β-associated kidney disease in patients referred with a suspected diagnosis of autosomal dominant polycystic kidney disease, medullary cystic kidney disease, diabetic nephropathy, or CKD of unknown cause. Associated renal or extrarenal symptoms should alert the nephrologist to HNF1β-associated kidney disease. A considerable proportion of these patients display hypomagnesemia, which sometimes mimics Gitelman syndrome. Other signs include early onset diabetes, gout and hyperparathyroidism, elevated liver enzymes, and congenital anomalies of the urogenital tract. Because many cases of this disease are probably undiagnosed, this review emphasizes the clinical manifestations of HNF1β-associated disease for the nephrologist.