Practical Approach to Congenital Anomalies of the Kidneys: Focus on Anomalies With Insufficient or Abnormal Nephron Development: Renal Dysplasia, Renal Hypoplasia, and Renal Tubular Dysgenesis.

Congenital anomalies of the kidney and urinary tract (CAKUT) accounts for up to 30% of antenatal congenital anomalies and is the main cause of kidney failure in children worldwide. This review focuses on practical approaches to CAKUT, particularly those with insufficient or abnormal nephron development, such as renal dysplasia, renal hypoplasia, and renal tubular dysgenesis. The review provides insights into the histological features, pathogenesis, mechanisms, etiologies, antenatal and postnatal presentation, management, and prognosis of these anomalies. Differential diagnoses are discussed as several syndromes may include CAKUT as a phenotypic component and renal dysplasia may occur in some ciliopathies, tumor predisposition syndromes, and inborn errors of metabolism. Diagnosis and genetic counseling for CAKUT are challenging, due to the extensive variability in presentation, genetic and phenotypic heterogeneity, and difficulties to assess postnatal lung and renal function on prenatal imaging. The review highlights the importance of perinatal autopsy and pathological findings in surgical specimens to establish the diagnosis and prognosis of CAKUT. The indications and the type of genetic testing are discussed. The aim is to provide essential insights into the practical approaches, diagnostic processes, and genetic considerations offering valuable guidance for pediatric and perinatal pathologists.

A novel frameshift variant of GATA3 (p.Ala17ProfsTer178) responsible for HDR syndrome in a Japanese family.

HDR syndrome is an autosomal dominant disorder characterized by hypoparathyroidism (H), deafness (D), and renal dysplasia (R) caused by genetic variants of the GATA3 gene. We present the case of a 38-year-old Japanese man with HDR syndrome who exhibited hypoparathyroidism, sensorineural deafness, renal dysfunction, severe symptomatic hypocalcemia with Chvostek's and Trousseau's signs, and QT prolongation on electrocardiography. He had a family history of deafness and hypocalcemia. Genetic testing revealed a novel GATA3 gene variant at exon 2 (c.48delC), which induces a frameshift resulting in termination at codon 178, causing HDR syndrome. We summarized 45 Japanese cases of HDR syndrome with regard to the mode of onset (familial or sporadic) and the age at diagnosis. In addition, we summarized all previous cases of HDR syndrome with GATA3 gene variants. Mapping of previously reported genetic variants in HDR syndrome revealed that most missense variants were observed at exons 4 and 5 regions in the GATA3 gene. These two regions contain zinc finger domains, demonstrating their functional importance in GATA3 transcription. This review of literature provides a useful reference for diagnosing HDR syndrome and predicting the related future manifestations.

Bilateral renal dysplasia with systemic fibrous osteodystrophy in a four-toed hedgehog (Atelerixalbiventris).

A 4-month-old female four-toed hedgehog (Atelerix albiventris) presented with lethargy, anorexia, dyspnoea and weight loss. Following death, post-mortem computed tomography (CT) and an autopsy were performed. CT revealed that the external surfaces of bones, including the cranial bones and vertebrae, were rough and osteolytic lesions were present multifocally in the ribs and some appendicular bones. On gross examination, both kidneys were severely enlarged and, on cut sections, a few cysts (up to 1 mm diameter) were present in the medulla. The cervical, thoracic and lumbar vertebrae were diffusely enlarged with deformation of the intervertebral discs. Histologically, there were immature glomeruli and tubules and adenomatoid/atypical epithelium in the kidneys. These changes were interpreted as renal dysplasia. In the bones evaluated, the trabeculae were thinner than normal, decreased in number and surrounded by many osteoclasts, with abundant fibrous connective tissue between atrophied trabeculae. These changes were consistent with fibrous osteodystrophy. Although kidney diseases are common in four-toed hedgehogs, there are no reports of congenital renal diseases, including renal dysplasia. To the best of our knowledge, this is the first report of the clinical and pathological features of renal dysplasia with fibrous osteodystrophy in a four-toed hedgehog.

Preeclampsia impedes foetal kidney development by delivering placenta-derived exosomes to glomerular endothelial cells.

BACKGROUND: Foetal renal dysplasia is still the main cause of adult renal disease. Placenta-derived exosomes are an important communication tool, and they may play an important role in placental (both foetal and maternal) function. We hypothesize that in women with preeclampsia, foetal renal dysplasia is impeded by delivering placenta-derived exosomes to glomerular endothelial cells. METHODS: In the present study, we established a PE trophoblast oxidative stress model to isolate exosomes from supernatants by ultracentrifugation (NO-exo and H/R-exo) and collected normal and PE umbilical cord blood plasma to isolate exosomes by ultracentrifugation combined with sucrose density gradient centrifugation (N-exo and PE-exo), then we investigated their effects on foetal kidney development by in vitro, ex vivo and in vivo models. RESULTS: The PE trophoblast oxidative stress model was established successfully. After that, in in vitro studies, we found that H/R-exo and PE-exo could adversely affect glomerular endothelial cell proliferation, tubular formation, migration, and barrier functions. In ex vivo studies, H/R-exo and PE-exo both inhibited the growth and branch formation of kidney explants, along with the decrease of VE-cadherin and Occludin. In in vivo studies, we also found that H/R-exo and PE-exo could result in renal dysplasia, reduced glomerular number, and reduced barrier function in foetal mice. CONCLUSIONS: In conclusion, we demonstrated that PE placenta-derived exosomes could lead to foetal renal dysplasia by delivering placenta-derived exosomes to foetal glomerular endothelial cells, which provides a novel understanding of the pathogenesis of foetal renal dysplasia. Video Abstract.

Hypoparathyroidism, deafness and renal dysplasia syndrome caused by a GATA3 splice site mutation leading to the activation of a cryptic splice site.

The HDR syndrome is a rare autosomal dominant disorder characterised by Hypoparathyroidism, Deafness, and Renal dysplasia, and is caused by inactivating heterozygous germline mutations in the GATA3 gene. We report an 11-year-old girl with HDR syndrome caused by a heterozygous mutation located at the splice acceptor site of exon 5 of the GATA3 gene (NM_001002295.2: c.925-1G>T). Functional studies using a minigene assay showed that this splice site mutation abolished the normal splicing of the GATA3 pre-mRNA and led to the use of a cryptic splice acceptor site, resulting in the loss of the first seven nucleotides (TCTGCAG) of exon 5 in the GATA3 mRNA. These findings increase the understanding of the mechanisms by which GATA3 splicing mutations can cause HDR syndrome.

Obstructed Hemivagina and Ipsilateral Renal Agenesis Syndrome in a Neonate.

Obstructed hemivagina with an ipsilateral renal anomaly (OHVIRA) syndrome is a congenital malformation that presents as a uterine didelphys with an obstructed hemivagina and an associated ipsilateral renal aberration. The clinical symptoms usually manifest after menarche. Unlike the typical presentation in adolescence, this case report features a neonatal presentation of OHVIRA syndrome with an unusual renal association. A female twin delivered at 35 weeks of gestation was transferred to our institution after birth from an outside hospital due to respiratory distress and for evaluation of the left multicystic dysplastic kidney identified on prenatal ultrasound. Physical examination and lab results, including a complete blood count, and a basic metabolic panel, including blood urea and serum creatinine, were within the normal range for age. Abdominal and pelvic ultrasound showed multicystic dysplastic left pelvic kidney, congenital hepatic cyst measuring 6 mm, uterine didelphys with duplication of the vaginal canal, and obstructed left hemivagina corresponding to the OHVIRA syndrome. Further testing revealed a normal chromosomal microarray, small patent foramen ovale on the echocardiogram, no vertebral or rib anomalies on the spinal x-ray, normal hearing test, and mild optic cupping on the ophthalmological evaluation. The pediatric surgeon and urologist recommended an outpatient follow-up and elective surgery in the future. This is a unique case presenting in the neonatal period with an unusual association. Timely intervention can help prevent obstetric complications.

Predictive factors for survival in patients with oligohydramnios secondary to antenatal kidney disease.

BACKGROUND: Renal oligohydramnios (ROH) is caused by bilateral congenital abnormalities, either of renal parenchymal or obstructive origin. ROH is a poor prognostic factor of neonatal survival; lung hypoplasia is reported to be the main cause of mortality. We aimed to describe the fetal morbidity and pre- and postnatal mortality in case of ROH due to renal congenital pathologies and to find predictive risk factors for morbidity and mortality. METHODS: All data were collected in Trousseau Hospital in the obstetric, neonatology, and pediatric nephrology units, from 2008 to 2020. RESULTS: We included 66 fetuses with renal parenchymal pathologies posterior urethral valves (PUV) (N = 25), bilateral kidney agenesis (N = 10), hypodysplasia (N = 16), and polycystic kidney disease (N = 10) causing oligohydramnios identified on antenatal ultrasound. Total pre- and postnatal mortality was 76% (50/66). Mortality, excepting termination of pregnancy (TOP), was 65%. The presence of pneumomediastinum and pneumothorax was not different in survivors and non-survivors. Fetuses with kidneys having features of hypodysplasia on ultrasound at T2 and those with oligohydramnios before 32 weeks GA had a higher risk of death. There was a significant difference in plasma creatinine of the surviving patients compared to the deceased patients, from day 3 onwards (183 µmol/L [88; 255] vs. 295 µmol/L [247; 326]; p = 0.038). CONCLUSIONS: The main differences between survivors and non-survivors among patients with "renal oligohydramnios" were oligohydramnios detection before 32 weeks GA, dysplasia detection on the second trimester ultrasound, and increase of serum creatinine from day 3 onwards. A higher resolution version of the Graphical abstract is available as Supplementary information.

Variants in AQP11 may result in autosomal recessive bilateral cystic renal dysgenesis.

Congenital renal cystic dysplasia is a rare disease that occurs in approximately 1 in 4000 children and is often discovered in the antenatal period by ultrasound. It is commonly associated with oligohydramnios in utero and/or renal insufficiency or failure in the postnatal period. Aquaporins are membrane proteins that serve as transport channels in the transfer of water or small solutes across cell membranes. They play a role in the development of renal cysts. Aquaporin 11 (AQP11) deficient mice develop polycystic kidney disease in utero due to disruption of polycystin-1. Here we describe a case of bilateral cystic kidney disease in a patient with novel compound heterozygous variants in AQP11: c.780G>T (p. Trp260Cys) and c.472C>T (p.Pro158Ser) (NM_173039.2) identified by whole genome sequencing. These findings suggest, for the first time, the potential role of AQP11 in congenital renal cystic dysplasia.

Potter Deformation Sequence Caused by 17q12 Deletion: A Lethal Constellation.

17q12 deletion syndrome causes developmental abnormalities of the kidneys, pancreas, genital tract, and neurodevelopment, and it has a wide range of phenotypes ranging from fetal demise to normal adulthood with minimal renal impairment. Here we describe a rare case of 17q12 deletion diagnosed prenatally, complicated by anhydramnios and Potter sequence. The baby was born but necessitated life-saving interventions due to pulmonary and renal insufficiency and ultimately succumbed to multi-organ failure. We present full autopsy results describing findings linked to 17q12 deletion, including severe bilateral multicystic renal dysplasia, pancreatic hypoplasia, and cysts adjacent to the Fallopian tubes. We also describe pulmonary hypoplasia and Potter facies as consequences of anhydramnios. We correlate these findings to our current understanding of molecular signals altered by 17q12 deletion, notably affecting HNF1B and LHX1 genes, which are known to mediate renal and genitourinary tract development.

Case report: BCL-2 and CD31 immunoexpression related to clinical and histopathological evaluation of renal dysplasia in a Welsh Corgi Puppy.

A case of renal dysplasia (RD) in the Welsh Corgi dog has been reported. Clinically, the affected 3-month-old, female, Welsh Corgi dog showed unclear symptoms of chronic kidney disease. Grossly, both left and right kidneys revealed cystic hypoplasia. Histologically, the primary lesions included immature or fetal glomeruli/tubules, proliferative arterioles, persistent metanephric ducts, persistent mesenchyme, and atypical tubular epithelium were presented. A group of degenerative and inflammatory lesions consisting of interstitial nephritis, interstitial fibrosis, and mineralization of tubules were found. Immunohistochemically, the epithelial cells of immature (fetal) tubules had BCL-2 labeling whereas CD31 (PECAM-1) was labeled in the endothelial cells of the proliferative arterioles. The immunohistochemical findings were confirmed and consolidated with the routine histopathological findings. This study was the first demonstration of the clinical, histopathological, and immunohistochemical features of RD disease in a Welsh Corgi puppy.

Unilateral macrocystic dysplasia and contralateral agenesis in a monoamniotic twin.

OBJECTIVE: We present a case report of a congenital malformation of the uropoetic tract in one of the monoamniotic twins. CASE REPORT: A 24-year-old primigravida with male monochorionic monoamniotic twins was dia-gnosed with congenital malformation in fetus A at 24 weeks of gestation. Ultrasound verified macrocystic dysplasia and contralateral renal agenesis. Planned caesarean section was performed after the observational management of the patient in the 34th gestational week. In fetus B, a physiological finding was confirmed on the postpartum ultrasonography. In fetus A, CT examination of the abdomen confirmed the finding of left kidney agenesis and polycystic degeneration of the right kidney. Exitus letalis was stated on the newborns 5th day. CONCLUSION: The occurrence of the described combination of congenital malformation in monoamniotic twins is rare. When dysplasia significantly affects the function of the parenchyma, renal agenesis with multicystic dysplasia of the other kidney is a condition incompatible with life. For the intrauterine survival of the affected fetus, the normal renal function of the twin was important and thus the normal volume of amniotic fluid was maintained. As a result, the fetus did not develop extrarenal symptoms of the Potter sequence in the described case - especially pulmonary hypoplasia and the newborn was able to ventilate spontaneously. The death was caused by the consequences of renal failure associated with anuria.

Tumor de Wilms en displasia renal multiquística

RESUMEN Introducción: La displasia renal multiquística es una anomalía congénita caracterizada por un riñón afuncional con quistes de diferentes tamaños. Es considerada como una anomalía del desarrollo, aunque se han descrito casos hereditarios. Se ha puntualizado la degeneración maligna de esta displasia, pero su asociación es muy rara. Objetivo: Describir una paciente con tumor de Wilms asociado a una displasia renal multiquística. Presentación del caso: Paciente de sexo femenino y 10 años de edad que los ultrasonidos prenatales no detectaron anomalías del tracto urinario y a los 7 años un estudio ecográfico detectó quistes en el riñón izquierdo. No cumplió el seguimiento clínico y ultrasonográfico indicado y abandonó la consulta; los 10 años asistió al médico por síntomas respiratorios agudos y al palpar el abdomen se comprobó masa en flanco izquierdo de consistencia leñosa, no dolorosa y con contacto lumbar. Se realizó biopsia renal y se diagnosticó tumor de Wilms, se impuso tratamiento citostático y se realizó nefrectomía que confirmó el diagnóstico. Entre los antecedentes familiares se informa un hermano fallecido antes de las 72 horas de nacido por displasia renal multiquística bilateral y madre con nefropatía por reflujo vesicoureteral. Conclusiones: La paciente que se describe reúne tres características raras: un tumor maligno asociado a una displasia renal multiquística, la posibilidad hereditaria por el antecedente del hermano con la displasia bilateral y un tumor de Wilms a los 10 años de edad, lo que demuestra la importancia del seguimiento en estos pacientes.

ABSTRACT Introduction: Multicystic renal dysplasia is a congenital anomaly characterized by an afunctional kidney with cysts of different sizes. It is considered a developmental abnormality, although hereditary cases have been described. The malignant degeneration of this dysplasia has been pointed out, but its association is very rare. Objective: Describe a patient with Wilms tumor associated with multicystic renal dysplasia. Case Presentation: 10-year-old female patient to whom prenatal ultrasounds did not detect urinary tract abnormalities and at age 7 an ultrasound study detected cysts in the left kidney. She did not comply with the indicated clinical and ultrasonographic follow-up and left the consultation; at 10 years old, she attended the doctor for acute respiratory symptoms and when palpating the abdomen there was a mass on the left flank of woody consistency, not painful and with lumbar contact. A renal biopsy was conducted and Wilms tumor was diagnosed; cytostatic treatment was indicated, and a nephrectomy was performed that confirmed the diagnosis. Among the family history is reported a brother who died before 72 hours of birth due to bilateral multicystic renal dysplasia and a mother with nephropathy by vesicoureteral reflux. Conclusions: The described patient has three rare characteristics: a malignant tumor associated with multicystic renal dysplasia, the hereditary possibility due to the sibling's history of bilateral dysplasia, and a Wilms tumor at 10 years of age, which demonstrates the importance of follow-up in these patients.

Renal Dysplasia with Hydronephrosis and Congenital Ureteral Stricture in Two Holstein-Friesian Calves.

We investigated the pathological characteristics of renal dysplasia with hydronephrosis and congenital ureteral stricture in two calves. Macroscopically, the affected kidneys were enlarged and the renal calyces were dilated and associated with ureteral strictures. Histopathologically, multifocal regions of mesenchyme were observed in the renal medulla. This mesenchyme was weakly eosinophilic with haematoxylin and eosin, blue with Alcian blue and pale blue with Masson's trichrome, and was immunopositive for vimentin and smooth muscle actin, consistent with persistent mesenchyme. There was asynchronous differentiation of the renal cortex characterized by immature glomeruli, immature tubules and arteriolar proliferation. Similar persistent mesenchyme was observed in the ureteral walls with ureteral stricture, and the ureteral musculature or smooth muscle bundles had a disorganized arrangement. Congenital ureteral stricture appeared to have caused ureteral obstruction and hydronephrosis. The lesions may represent a new phenotype of renal dysplasia with concomitant congenital ureteral stricture in Holstein-Friesian calves.

Multiple vas deferens with polyorchidism and many congenital malformations in a symptomatic 11-year-old male patient: a rare case report.

BACKGROUND: Ductus deferens may manifest in a variety of anomalies such as its absence, duplication, ectopy, or diverticulum. Ectopic seminal tract opening has two main types, ectopic ejaculatory duct opening, and ectopic vas deferens opening. Generally, ductus deferens anomalies affect approximately 0.05% of the population. Patients may be asymptomatic or complaining of urinary tract infections and/or epididymitis. Most of these cases are associated with renal dysplasia. To confirm the diagnosis Cystourethroscopy catheterization and retrograde urethrogram should be performed, but the definitive diagnosis is done by vasography. The definitive treatment is complete surgical resection of the pathological urogenital connection. This case is commonly discovered while exploring other findings such as testicular torsion and inguinal hernia. CASE PRESENTATION: We report a rare case of an 11-year-old male who presented with gross hematuria and numerous congenital malformations including a left polydactyly clubfoot, polyorchidism, with several surgical procedures, and left kidney dysgenesis. Surgery was performed for a left inguinal hernia, during which a third undescended testicle was discovered incidentally and was eradicated. A retrograde urethrogram was performed to establish the diagnosis. A fistula- that is connected with the left ureter- was resected. The histopathologic findings confirmed the diagnosis of true duplication of the Vas deferens, with communication between the ureter and the vas deferens. By follow-up, the kidney function tests were within normal limits. CONCLUSIONS: This case report aims to highlight the early diagnosis and management of the duplicated vas deferens and the associated congenital malformations to improve the prognosis and kidney function and to avoid long-term complications.

Bainbridge-Ropers Syndrome in a Texan Boy: A Case Report and Review of the Literature.

Bainbridge-Ropers syndrome (BRPS) or additional sex combs-like 3 (ASXL3)-related disorder is a neurodevelopmental disorder caused by a de novo missense mutation in the ASXL3 gene found on chromosome 18. The number of BRPS cases recorded to date is less than 100. In this report, a six-year-old Texan boy with global developmental delay, aggressive behavior, insomnia, microcephaly, strabismus, facial dysmorphic features, vesicoureteral reflux (VUR), bilateral congenital renal dysplasia, gastroesophageal reflux disease (GERD), hypotonia, failure to thrive, dysphagia, and status post-gastrostomy tube was referred to Children's Health in Dallas for evaluation. The patient shares a chromosomal abnormality with his father that did not explain his clinical findings. Therefore, further tests were indicated and a whole-exome gene sequencing revealed a de novo pathogenic heterozygous mutation in the ASXL3 gene in chromosome 18q12.1 associated with autosomal dominant BRPS. To our knowledge, this is the first case of BRPS with bilateral congenital renal dysplasia and may be correlated to the presence of the ASXL3 gene in renal tissue. This discovery provides significant new information about this condition that might be essential for comprehending it.

Pathological and sonographic review of early isolated severe lower urinary tract obstruction and implications for prenatal treatment.

OBJECTIVE: To identify favorable renal histology in fetuses with early severe lower urinary tract obstruction (LUTO) and determine the best timing and selection criteria for prenatal surgery. METHODS: This multicenter, retrospective study included male fetuses with severe LUTO which died before 24 weeks of gestation during the period January 2000 to December 2018. Age-matched controls were used as reference standard for renal histology. Prenatal ultrasound features and fetal serum and/or urine ß2microglobulin level were retrieved and kidney histology slides (hematein-eosin-safran and α-smooth-muscle-actin (αSMA) immunostaining) were prepared and reviewed. αSMA-positive staining of the blastema is due to its aberrant differentiation into myofibroblastic cells. Cases were sorted into histopathologic groups (favorable or unfavorable) according to the blastema's morphology and αSMA labeling and the data of these groups were compared. RESULTS: Included in the study were 74 fetuses with a median gestational age at outcome of 17 + 6 (range, 13 + 0 to 23 + 5) weeks. Parenchymal organization was preserved in 48% of the kidneys. A blastema was present in 90% of the kidneys, but it was morphologically normal in only 9% and αSMA-negative in only 1% of them. Most (82%) fetuses had an unfavorable prognosis, and 36% of fetuses died ≤ 18 weeks and had severe renal lesions detected on histology (early unfavorable prognosis). A favorable renal prognosis was associated with an earlier gestational age (P = 0.001). Fetuses with LUTO had a significantly lower number of mature glomeruli (P < 0.001) compared with controls. However, there was no significant difference in the number of glomeruli generations between the early-unfavorable-prognosis group (≤ 18 weeks) and the group with a favorable prognosis (P = 0.19). A comparison of prenatal ultrasound features and biochemical markers between groups could not identify any prenatal selection criteria. CONCLUSIONS: Before 18 weeks, around 30% of fetuses with severe LUTO still have potential for kidney development. Identification of these cases would enable them to be targeted for prenatal therapy. © 2021 International Society of Ultrasound in Obstetrics and Gynecology.

A novel ITGA3 homozygous splice mutation in an ILNEB syndrome child with slow progression.

BACKGROUND AND AIMS: ILNEB (interstitial lung disease, nephrotic syndrome, epidermolysis bullosa) syndrome is caused by ITGA3 mutations. Demises usually happened at infancy. This study reports a complete ILNEB syndrome child with slow disease progression. MATERIALS AND METHODS: Clinical data and related specimens were collected. Genomic DNA was extracted for genetic sequencing. Integrin α3 expression was detected by western blotting and immunofluorescence staining. RESULTS: The patient was male. He experienced recurrent rashes shortly after birth. His sparse eyebrows and eyelashes gradually lost. The patient was vulnerable to respiratory infections and had recurrent fever after vaccine immunization after 4 years. He was found with nephrotic syndrome and polycystic renal dysplasia at 8 years and progressed to end-stage renal disease at 12 years. A chest Computed Tomography revealed intestinal lung disease at 8 years. Continuous oxygen supplementation was needed at 13 years. Counts of lymphocyte subsets revealed elevated percentage of double-negative T cells and activated T cells. Next-generation sequencing revealed a novel homozygous splice mutation c.2219 + 4A > Cin ITGA3 that was predicted to be deleterious. The mutation resulted in exon17 skipping with the loss of 80 bp in the mRNA. The aberrant integrin α3 mRNA level was lower compared to the healthy control. Integrin α3 protein was not detected in urine epithelial cells and skin of the patient. CONCLUSIONS: We report a patient harboring a novel ITGA3 homozygous splice mutation who presented with complete ILNEB syndrome but slow disease progression. Immune disorders were suspected.

Comprehensive Metabolic Signature of Renal Dysplasia in Children. A Multiplatform Metabolomics Concept.

Renal dysplasia is a severe congenital abnormality of the kidney parenchyma, which is an important cause of end-stage renal failure in childhood and early adulthood. The diagnosis of renal dysplasia relies on prenatal or postnatal ultrasounds as children show no specific clinical symptoms before chronic kidney disease develops. Prompt diagnosis is important in terms of early introduction of nephroprotection therapy and improved long-term prognosis. Metabolomics was applied to study children with renal dysplasia to provide insight into the changes in biochemical pathways underlying its pathology and in search of early indicators for facilitated diagnosis. The studied cohort consisted of 72 children, 39 with dysplastic kidneys and 33 healthy controls. All subjects underwent comprehensive urine metabolic profiling with the use of gas chromatography and liquid chromatography coupled to mass spectrometry, with two complementary separation modes of the latter. Univariate and multivariate statistical calculations identified a total of nineteen metabolites, differentiating the compared cohorts, independent of their estimated glomerular filtration rate. Seven acylcarnitines, xanthine, and glutamine were downregulated in the urine of renal dysplasia patients. Conversely, renal dysplasia was associated with higher urinary levels of dimethylguanosine, threonic acid or glyceric acid. This is the first metabolomic study of subjects with renal dysplasia. The authors define a characteristic urine metabolic signature in children with dysplastic kidneys, irrespective of renal function, linking the condition with altered fatty acid oxidation, amino acid and purine metabolisms.