Renal tract malformations: perspectives for nephrologists

Congenital anomalies of the kidney and urinary tract: defining risk factors of disease progression and determinants of outcomes

Congenital anomalies of the kidney and urinary tract (CAKUT) result from disruptions in normal kidney and urinary tract development during fetal life and collectively represent the most common cause of kidney failure in children worldwide. The antenatal determinants of CAKUT are diverse and include mutations in genes responsible for normal nephrogenesis, alterations in maternal and fetal environments, and obstruction within the normal developing urinary tract. The resultant clinical phenotypes are complex and depend on the timing of the insult, the penetrance of underlying gene mutations, and the severity and timing of obstruction related to the sequence of normal kidney development. Consequently, there is a broad spectrum of outcomes for children born with CAKUT. In this review, we explore the most common forms of CAKUT and those most likely to develop long-term complications of their associated kidney malformations. We discuss the relevant outcomes for the different forms of CAKUT and what is known about clinical characteristics across the CAKUT spectrum that are risk factors of long-term kidney injury and disease progression.

Predicting outcomes in children with congenital anomalies of the kidney and urinary tract

BACKGROUND

Congenital anomalies of the kidney and urinary tract (CAKUT) are the most frequent causes of childhood chronic kidney disease (CKD). Using a large CAKUT cohort, we sought to identify the predictors of CKD and to develop a prediction model that informs a risk-stratified clinical pathway.

METHODS

This was a retrospective cohort study including cases with multicystic dysplastic kidneys (MCDK), unilateral kidney agenesis (UKA), kidney hypoplasia (KH), and posterior urethral valves (PUV). We identified risk factors for CKD (estimated glomerular filtration rate [eGFR] <60 ml/min/1.73 m2) and tested their performance in an adjusted multivariate binary regression model. Prediction probability scores for CKD were used to separate cases likely to develop complications from those not needing specialist follow-up.

RESULTS

We identified 452 eligible cases of CAKUT with 22% developing CKD. Strongest associations with CKD included primary diagnosis (OR 3.5, 95% CI 2.6-4.6), preterm delivery (OR 2.3, 95% CI 1.2-4.4), non-kidney anomalies (OR 1.8, 95% CI 1.1-3), first eGFR<90 (OR 8.9, 95% CI 4.4-18.1), small kidney size (OR 9, 95% CI 4.9-16.6), and additional kidney anomalies (OR 1.6, 95% CI 1.2-2.8). PUV (OR 4.7, 95% CI 1.5-15.3), first eGFR <90 (OR 4.4, 95% CI 2-9.7), and kidney length to body length ratio <7.9 (OR 4.2, 95% CI 1.9-9.2) were independent predictors of CKD. The regression model had a prediction accuracy of 80% and a prediction probability c-statistic of 0.81.

CONCLUSION

Using a large combined CAKUT cohort we identified risk factors for CKD. Our prediction model provides the first steps towards a risk-stratified clinical pathway. A higher resolution version of the Graphical abstract is available as Supplementary information.

Missense Variants in GFRA1 and NPNT Are Associated with Congenital Anomalies of the Kidney and Urinary Tract

The use of next-generation sequencing (NGS) has helped in identifying many genes that cause congenital anomalies of the kidney and urinary tract (CAKUT). Bilateral renal agenesis (BRA) is the most severe presentation of CAKUT, and its association with autosomal recessively inherited genes is expanding. Highly consanguineous populations can impact the detection of recessively inherited genes. Here, we report two families harboring homozygous missense variants in recently described genes, NPNT and GFRA1. Two consanguineous families with neonatal death due to CAKUT were investigated. Fetal ultrasound of probands identified BRA in the first family and severe renal cystic dysplasia in the second family. Exome sequencing coupled with homozygosity mapping was performed, and Sanger sequencing was used to confirm segregation of alleles in both families. In the first family with BRA, we identified a homozygous missense variant in GFRA1: c.362A>G; p.(Tyr121Cys), which is predicted to damage the protein structure. In the second family with renal cystic dysplasia, we identified a homozygous missense variant in NPNT: c.56C>G; p.(Ala19Gly), which is predicted to disrupt the signal peptide site. We report two Saudi Arabian consanguineous families with CAKUT phenotypes that included renal agenesis caused by missense variants in GFRA1 and NPNT, confirming the role of these two genes in human kidney development.

Nephrotic Syndrome Associated with Hydronephrosis and Unilateral Renal Agenesis

We reported a case of nephrotic syndrome in a child presenting undiagnosed hydronephrosis and unilateral renal agenesis in a 3 years and 9 months old male patient presenting features of nephrotic syndrome, with left hydronephrosis and unilateral renal agenesis. The association of nephrotic syndrome with congenital anomalies is extremely rare. The importance of this unusual combination was discussed respecting the literature.

The Prevalence of Müllerian Anomalies in Women with a Diagnosed Renal Anomaly

STUDY OBJECTIVE

To characterize the prevalence of Müllerian anomalies (MAs) among patients with renal anomalies (RAs). DESIGN, SETTING, PARTICIPANTS, INTERVENTIONS, AND MAIN OUTCOME MEASURES: A retrospective chart review of female patients with RAs who presented to an academic pediatric hospital between 2007 and 2019 was performed. Patients were identified using International Classification of Diseases 9th and 10th revision codes. Data collected included the type of RA, presence and type of MA, method of diagnosis, and associated anomalies. RA subtype analysis was performed.

RESULTS

We identified 5590 cases of RA for the years 2007 through 2019. A random, retrospective chart review was performed resulting in a study population of 363 RA patients. The prevalence of any MA in the overall RA population was 104/363 (29%) (95% confidence interval, 24% - 33%). The prevalence of MA for patients with renal agenesis was 59/182 (32%) compared with 45/181 (25%) for patients with renal dysgenesis. The most common MA were failures of Müllerian duct fusion. Only 73/352 (21%) of patients received screening for a MA at the time of RA diagnosis. Of patients without a diagnosed MA 187/259 (72%) were unscreened and either not yet menarchal or had unknown menarchal status.

CONCLUSIONS

Of all RA patients, 29% (n = 104/363) had an underlying MA. No difference was found in the prevalence of MA in patients with renal agenesis vs dysgenesis. Limitations noted are that some patients might be of an age at which assessment of the Müllerian structures is suboptimal or who might not have been screened. These results suggest the need for a prospective study to determine evidence-based guidelines for screening for MA among patients diagnosed with any RA to avoid complications from an unrecognized MA.

ROBO2-mediated RALDH2 signaling is required for common nephric duct fusion with primitive bladder

Congenital anomalies of the urinary tract are a significant cause of morbidity in infancy, and many congenital anomalies are linked to ureter development; however, the mechanism by which congenital anomalies control ureter development remains unknown. The loss of Robo2 can cause ureter defects and vesicoureteral reflux. However, how Robo2 impacts ureter development is unclear. We found that ROBO2 is expressed in the common nephric duct (CND) and primitive bladder, and impacts CND migration and fusion with the primitive bladder via its novel binding partner retinaldehyde dehydrogenase-2 (RALDH2). Delayed apoptosis that is due to the failure of CND fusion with the primitive bladder in the Robo2^-/-embryo results in an abnormal ureter connection to the CND, which is required for ureter development. We define a novel pathway in which the CND is remodeled by ROBO2 and retinoic acid rescued the ureter anomalies in the Robo2^-/-embryo. These findings may be relevant to diverse disease conditions that are associated with altered signaling in the primitive bladder.

Clinical Exome Sequencing Identifies a Novel Mutation of the GREB1L Gene in a Chinese Family with Renal Agenesis

Background: Renal agenesis (RA) is one of the most severe congenital anomalies of the kidney and urinary tract; it is known to be highly genetically heterogeneous. The purpose of this study was to explore the clinical significance of genetic diagnostics in a Chinese RA family. Methods: Five members of an RA family and 100 healthy people were recruited. Clinical exome sequencing was conducted to explore the underlying genetic cause in the affected family. Results: Exome sequencing identified a novel missense mutation (c.2333T>A, p.Val778Asp) in the GREB1L gene. This GREB1L variant was not detected in controls and was predicted to be highly damaging to the physiological function of the GREB1L protein. Conclusion: We identified a novel c.2333T>A variant in the GREB1L gene that extends the mutational spectrum associated with renal agenesis.

Overactivity or blockade of transforming growth factor-β each generate a specific ureter malformation

Transforming growth factor-β (TGFβ) has been reported to be dysregulated in malformed ureters. There exists, however, little information on whether altered TGFβ levels actually perturb ureter development. We therefore hypothesised that TGFβ has functional effects on ureter morphogenesis. Tgfb1, Tgfb2 and Tgfb3 transcripts coding for TGFβ ligands, as well as Tgfbr1 and Tgfbr2 coding for TGFβ receptors, were detected by quantitative polymerase chain reaction in embryonic mouse ureters collected over a wide range of stages. As assessed by in situ hybridisation and immunohistochemistry, the two receptors were detected in embryonic urothelia. Next, TGFβ1 was added to serum-free cultures of embryonic day 15 mouse ureters. These organs contain immature smooth muscle and urothelial layers and their in vivo potential to grow and acquire peristaltic function can be replicated in serum-free organ culture. Such organs therefore constitute a suitable developmental stage with which to define roles of factors that affect ureter growth and functional differentiation. Exogenous TGFβ1 inhibited growth of the ureter tube and generated cocoon-like dysmorphogenesis. RNA sequencing suggested that altered levels of transcripts encoding certain fibroblast growth factors (FGFs) followed exposure to TGFβ. In serum-free organ culture exogenous FGF10 but not FGF18 abrogated certain dysmorphic effects mediated by exogenous TGFβ1. To assess whether an endogenous TGFβ axis functions in developing ureters, embryonic day 15 explants were exposed to TGFβ receptor chemical blockade; growth of the ureter was enhanced, and aberrant bud-like structures arose from the urothelial tube. The muscle layer was attenuated around these buds, and peristalsis was compromised. To determine whether TGFβ effects were limited to one stage, explants of mouse embryonic day 13 ureters, more primitive organs, were exposed to exogenous TGFβ1, again generating cocoon-like structures, and to TGFβ receptor blockade, again generating ectopic buds. As for the mouse studies, immunostaining of normal embryonic human ureters detected TGFβRI and TGFβRII in urothelia. Collectively, these observations reveal unsuspected regulatory roles for endogenous TGFβ in embryonic ureters, fine-tuning morphogenesis and functional differentiation. Our results also support the hypothesis that the TGFβ up-regulation reported in ureter malformations impacts on pathobiology. Further experiments are needed to unravel the intracellular signalling mechanisms involved in these dysmorphic responses. © 2019 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of Pathological Society of Great Britain and Ireland.

Histology Atlas of the Developing Mouse Urinary System With Emphasis on Prenatal Days E10.5-E18.5

Congenital abnormalities of the urinary tract are some of the most common human developmental abnormalities. Several genetically engineered mouse models have been developed to mimic these abnormalities and aim to better understand the molecular mechanisms of disease. This atlas has been developed as an aid to pathologists and other biomedical scientists for identification of abnormalities in the developing murine urinary tract by cataloguing normal structures at each stage of development. Hematoxylin and eosin- and immunohistochemical-stained sections are provided, with a focus on E10.5-E18.5, as well as a brief discussion of postnatal events in urinary tract development. A section on abnormalities in the development of the urinary tract is also provided, and molecular mechanisms are presented as supplementary material. Additionally, overviews of the 2 key processes of kidney development, branching morphogenesis and nephrogenesis, are provided to aid in the understanding of the complex organogenesis of the kidney. One of the key findings of this atlas is the histological identification of the ureteric bud at E10.5, as previous literature has provided conflicting reports on the initial point of budding. Furthermore, attention is paid to points where murine development is significantly distinct from human development, namely, in the cessation of nephrogenesis.

The clinical characteristics of Chinese patients with unilateral renal agenesis

BACKGROUND

We aimed to investigate the clinical characteristics of Chinese patients with unilateral renal agenesis.

METHODS

We enrolled patients with unilateral renal agenesis diagnosed radiologically at the Department of Nephrology from January 2008 to January 2016. Patients with a solitary kidney due to nephrectomy or renal atrophy due to secondary factors were excluded. Clinical data were recorded and analyzed.

RESULTS

In this study, 118 Chinese patients with unilateral renal agenesis were recruited, and the gender ratio (male/female) was 1.11:1. A total of 14 (11.9%) patients had additional abnormalities, 15 (12.7%) had a family history, and 30 (25.4%) presented with renal insufficiency. Kidney length, serum creatinine level and estimated glomerular filtration rate were significantly different between patients with and without family history (P < 0.05, respectively). Gender showed a significant difference between patients with and without other abnormalities. Kidney length and the incidence of proteinuria, hematuria, hypertension, and hyperuricemia were significantly different between patients with and without renal insufficiency. Logistic regression analysis revealed that family history was associated with severe renal failure (OR = 7.11, 95% CI 1.52-33.25).

CONCLUSION

Renal insufficiency is common in patients with unilateral renal agenesis. Patients with renal insufficiency have shorter kidney lengths and a higher incidence of proteinuria, hypertension, hematuria, and hyperuricemia. Family history is considered a risk factor for severe renal failure.

Serum-Free Organ Culture of the Embryonic Mouse Ureter

The ability to explant and then maintain embryonic tissues in organ culture makes it feasible to study the growth and differentiation of whole organs, or parts or combinations of them, in three dimensions. Moreover, the possible effects of biochemical manipulations or mutations can be explored by visualizing a growing organ. The mammalian renal tract comprises the kidney, ureter, and urinary bladder, and the focus of this chapter is organ culture of the embryonic mouse ureter in serum-free defined medium. Over the culture period, rudiments grow in length, smooth muscle differentiates, and the ureters then undergo peristalsis in a proximal to distal direction.

Congenital Disorders of the Human Urinary Tract: Recent Insights From Genetic and Molecular Studies

The urinary tract comprises the renal pelvis, the ureter, the urinary bladder, and the urethra. The tract acts as a functional unit, first propelling urine from the kidney to the bladder, then storing it at low pressure inside the bladder which intermittently and completely voids urine through the urethra. Congenital diseases of these structures can lead to a range of diseases sometimes associated with fetal losses or kidney failure in childhood and later in life. In some of these disorders, parts of the urinary tract are severely malformed. In other cases, the organs appear grossly intact yet they have functional deficits that compromise health. Human studies are beginning to indicate monogenic causes for some of these diseases. Here, the implicated genes can encode smooth muscle, neural or urothelial molecules, or transcription factors that regulate their expression. Furthermore, certain animal models are informative about how such molecules control the development and functional differentiation of the urinary tract. In future, novel therapies, including those based on gene transfer and stem cell technologies, may be used to treat these diseases to complement conventional pharmacological and surgical clinical therapies.

Developmental pathology of congenital kidney and urinary tract anomalies

Congenital anomalies of the kidneys or lower urinary tract (CAKUT) are the most common causes of renal failure in children and account for 25% of end-stage renal disease in adults. The spectrum of anomalies includes renal agenesis; hypoplasia; dysplasia; supernumerary, ectopic or fused kidneys; duplication; ureteropelvic junction obstruction; primary megaureter or ureterovesical junction obstruction; vesicoureteral reflux; ureterocele; and posterior urethral valves. CAKUT originates from developmental defects and can occur in isolation or as part of other syndromes. In recent decades, along with better understanding of the pathological features of the human congenital urinary tract defects, researchers using animal models have provided valuable insights into the pathogenesis of these diseases. However, the genetic causes and etiology of many CAKUT cases remain unknown, presenting challenges in finding effective treatment. Here we provide an overview of the critical steps of normal development of the urinary system, followed by a description of the pathological features of major types of CAKUT with respect to developmental mechanisms of their etiology.

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.

Generation of Functioning Nephrons by Implanting Human Pluripotent Stem Cell-Derived Kidney Progenitors

Human pluripotent stem cells (hPSCs) hold great promise for understanding kidney development and disease. We reproducibly differentiated three genetically distinct wild-type hPSC lines to kidney precursors that underwent rudimentary morphogenesis in vitro. They expressed nephron and collecting duct lineage marker genes, several of which are mutated in human kidney disease. Lentiviral-transduced hPSCs expressing reporter genes differentiated similarly to controls in vitro. Kidney progenitors were subcutaneously implanted into immunodeficient mice. By 12 weeks, they formed organ-like masses detectable by bioluminescence imaging. Implants included perfused glomeruli containing human capillaries, podocytes with regions of mature basement membrane, and mesangial cells. After intravenous injection of fluorescent low-molecular-weight dextran, signal was detected in tubules, demonstrating uptake from glomerular filtrate. Thus, we have developed methods to trace hPSC-derived kidney precursors that formed functioning nephrons in vivo. These advances beyond in vitro culture are critical steps toward using hPSCs to model and treat kidney diseases.

•

Reproducible differentiation to kidney progenitors in 3 hESC lines

•

After subcutaneous implantation, kidney-like tissues detectable by bioluminescence

•

Implant nephrons contain glomeruli, proximal and distal tubules, and collecting ducts

•

Vascularized glomeruli filter intravenously injected low-molecular-weight dextran

Life with one kidney

Life with a solitary functioning kidney (SFK) may be different from that when born with two kidneys. Based on the hyperfiltration hypothesis, a SFK may lead to glomerular damage with hypertension, albuminuria and progression towards end-stage renal disease. As the prognosis of kidney donors was considered to be very good, having a SFK has been considered to be a benign condition. In contrast, our research group has demonstrated that being born with or acquiring a SFK in childhood results in renal injury before adulthood in over 50% of those affected. Most congenital cases will be detected during antenatal ultrasound screening, but up to 38% of cases of unilateral renal agenesis are missed. In about 25-50% of cases of antenatally detected SFK there will be signs of hypertrophy, which could indicate additional nephron formation and is associated with a somewhat reduced risk of renal injury. Additional renal and extrarenal anomalies are frequently detected and may denote a genetic cause for the SFK, even though for the majority of cases no explanation can (yet) be found. The ongoing glomerular hyperfiltration results in renal injury, for which early markers are lacking. Individuals with SFK should avoid obesity and excessive salt intake to limit additional hyperfiltration. As conditions like hypertension, albuminuria and a mildly reduced glomerular filtration rate generally do not result in specific complaints but may pose a threat to long-term health, screening for renal injury in any individual with a SFK would appear to be imperative, starting from infancy. With early treatment, secondary consequences may be diminished, thereby providing the optimal life for anyone born with a SFK.

Outcomes of prenatally diagnosed solitary functioning kidney during early life

OBJECTIVE

To evaluate outcomes of congenital solitary functioning kidney (SFK) in early childhood.

STUDY DESIGN

A retrospective study of 32 children diagnosed in utero with SFK owing to unilateral renal agenesis or multicystic dysplastic kidney and followed for 1 to 11.5 years.

RESULTS

SFK length was in the compensatory hypertrophy range in 45% of fetal sonographic evaluations from mid-pregnancy, and in 85% on postnatal follow-up. Glomerular filtration rate was below normal range in 44.4%, 12.5% and 0% at <1 year, age 1 to 3 years and thereafter, respectively. Hyperfiltration was detected in 18.5% and 82.6% at <1 year and >3 years, respectively. Hypertension was documented in 35% at age 1 to 3 years but in none at an older age. Proteinuria was absent in all children.

CONCLUSION

Congenital SFK is apparently associated with little or no renal damage in infancy or childhood. Compensatory enlargement of the functioning kidney begins in utero and might serve as a prognostic indicator for normal renal function after birth.

Evidence-based, ethically justified counseling for fetal bilateral renal agenesis

BACKGROUND

Not much data are available on the natural history of bilateral renal agenesis, as the medical community does not typically offer aggressive obstetric or neonatal care asbilateral renal agenesis has been accepted as a lethal condition.

AIM

To provide an evidence-based, ethically justified approach to counseling pregnant women about the obstetric management of bilateral renal agenesis.

STUDY DESIGN

A systematic literature search was performed using multiple databases. We deploy an ethical analysis of the results of the literature search on the basis of the professional responsibility model of obstetric ethics.

RESULTS

Eighteen articles met the inclusion criteria for review. With the exception of a single case study using serial amnioinfusion, there has been no other case of survival following dialysis and transplantation documented. Liveborn babies die during the neonatal period. Counseling pregnant women about management of pregnancies complicated by bilateral renal agenesis should be guided by beneficence-based judgment informed by evidence about outcomes.

CONCLUSIONS

Based on the ethical analysis of the results from this review, without experimental obstetric intervention, neonatal mortality rates will continue to be 100%. Serial amnioinfusion therefore should not be offered as treatment, but only as approved innovation or research.

A Gene Implicated in Activation of Retinoic Acid Receptor Targets Is a Novel Renal Agenesis Gene in Humans

Renal agenesis (RA) is one of the more extreme examples of congenital anomalies of the kidney and urinary tract (CAKUT). Bilateral renal agenesis is almost invariably fatal at birth, and unilateral renal agenesis can lead to future health issues including end-stage renal disease. Genetic investigations have identified several gene variants that cause RA, including EYA1, LHX1, and WT1 However, whereas compound null mutations of genes encoding α and γ retinoic acid receptors (RARs) cause RA in mice, to date there have been no reports of variants in RAR genes causing RA in humans. In this study, we carried out whole exome sequence analysis of two families showing inheritance of an RA phenotype, and in both identified a single candidate gene, GREB1L Analysis of a zebrafish greb1l loss-of-function mutant revealed defects in the pronephric kidney just prior to death, and F0 CRISPR/Cas9 mutagenesis of Greb1l in the mouse revealed kidney agenesis phenotypes, implicating Greb1l in this disorder. GREB1L resides in a chromatin complex with RAR members, and our data implicate GREB1L as a coactivator for RARs. This study is the first to associate a component of the RAR pathway with renal agenesis in humans.

Does the serum uric acid level have any relation to arterial stiffness or blood pressure in adults with congenital renal agenesis and/or hypoplasia?

BACKGROUND

The relationship between serum uric acid and arterial stiffness or blood pressure is not clear. The serum uric acid level and its association with cardiovascular risk is not well known in patients with reduced renal mass. We aimed to investigate the relation between serum uric acid levels and arterial stiffness and also blood pressure in patients with congenital renal agenesis and/or hypoplasia.

MATERIAL AND METHODS

In this single center, cross-sectional study, a total of 55 patients (39 (% 70.9) with unilateral small kidney and 16 (%29.1) with renal agenesis) were included. The median age was 35 (21-50) years. The study population was divided into tertiles of serum uric acid (according to 2.40-3.96, 3.97-5.10, and 5.11-9.80 mg/dl cut-off values of serum uric acid levels). Official and 24-h ambulatory non-invasive blood pressures of all patients were measured. The arterial stiffness was assessed by pulse wave velocity (PWV).

RESULTS

PWV values were increased from first to third tertile (5.5 ± 0.6, 5.7 ± 0.8, 6.1 ± 0.7, respectively), but this gradual increase between tertiles did not reach significance. Linear regression analyses showed a positive correlation between serum uric acid levels and PWV (β = 0.40, p = 0.010), but no correlation was found between uric acid and daytime systolic blood pressure (β = 0.24, p = 0.345).

CONCLUSION

In congenital renal agenesis/hypoplasia, the serum uric acid level was positively correlated with arterial stiffness, but there was no correlation with blood pressure.

Severe congenital anomalies of the kidney and urinary tract: epidemiology can inform ethical decision-making

OBJECTIVE

Decision-making for pregnancies complicated by severe congenital anomalies of the kidneys and urinary tract (CAKUT) are ethically challenging, partly because the outcomes are not well studied.

STUDY DESIGN

Retrospective cohort study of severe cases of CAKUT over 14 years.

RESULTS

Seventy-one of the 108 cases could be completely analyzed. Forty-six percent (n=33) infants were live-born; one-third (n=11) survived to 12 months. Twice as many non-surviving infants received a trial of therapy vs comfort care only. Two-thirds of non-survivors who received a trial of therapy died within the first 9 h of life. Live-born infants faced morbidities such as pneumothorax and neonatal dialysis.

CONCLUSIONS

Over half of pregnancies complicated by severe CAKUT ended in termination or stillbirth, but one-third of live-born infants survived to 12 months and the majority of non-survivors died within hours. This may allay concerns about prolonged and futile intensive care for parents considering a trial of therapy.

Planar cell polarity genes Celsr1 and Vangl2 are necessary for kidney growth, differentiation, and rostrocaudal patterning

The mammalian kidney contains nephrons comprising glomeruli and tubules joined to ureteric bud-derived collecting ducts. It has a characteristic bean-like shape, with near-complete rostrocaudal symmetry around the hilum. Here we show that Celsr1, a planar cell polarity (PCP) gene implicated in neural tube morphogenesis, is required for ureteric tree growth in early development and later in gestation prevents tubule overgrowth. We also found an interaction between Celsr1 and Vangl2 (another PCP gene) in ureteric tree growth, most marked in the caudal compartment of the kidneys from compound heterozygous mutant mice with a stunted rump. Furthermore, these genes together are required for the maturation of glomeruli. Interestingly, we demonstrated patients with CELSR1 mutations and spina bifida can have significant renal malformations. Thus, PCP genes are important in mammalian kidney development and have an unexpected role in rostrocaudal patterning during organogenesis.

Eph/ephrin signaling in the kidney and lower urinary tract

Development and homeostasis of the highly specialized cell types and tissues that constitute the organs of the urinary system, the kidneys and ureters, the bladder, and the urethra, require the tightly regulated exchange of signals in and between these tissues. Eph/ephrin signaling is a bidirectional signaling pathway that has been functionally implicated in many developmental and homeostatic contexts, most prominently in the vascular and neural system. Expression and knockout analyses have now provided evidence that Eph/ephrin signaling is of crucial relevance for cell and tissue interactions in the urinary system as well. A clear requirement has emerged in the formation of the vesicoureteric junction, in urorectal septation and glomerulogenesis during embryonic development, in maintenance of medullary tubular cells and podocytes in homeostasis, and in podocyte and glomerular injury responses. Deregulation of Eph/ephrin signaling may also contribute to the formation and progression of tumors in the urinary system, most prominently bladder and renal cell carcinoma. While in the embryonic contexts Eph/ephrin signaling regulates adhesion of epithelial cells, in the adult setting, cell-shape changes and cell survival seem to be the primary cellular processes mediated by this signaling module. With progression of the genetic analyses of mice conditionally mutant for compound alleles of Eph receptor and ephrin ligand genes, additional essential functions are likely to arise in the urinary system.

MDCT and MR Urogram Spectrum of Congenital Anomalies of the Kidney and Urinary Tract Diagnosed in Adulthood

OBJECTIVE

Congenital anomalies of the kidneys and urinary tract (CAKUT) encompass a spectrum of anomalies that result from genetic, epigenetic, environmental, and molecular signal aberrations at key stages of urinary tract development. CAKUT can be seen incidentally on cross-sectional imaging of the abdomen or can be a cause for adult-onset chronic kidney disease, posing new challenges for nephrologists, urologists, and radiologists.

CONCLUSION

Awareness of CAKUT and familiarity with their imaging findings permit optimal patient management and thorough workup to prevent hypertension and progression from CAKUT to renal failure. The purpose of this article is to review the cross-sectional imaging findings of CAKUT that may present in adulthood.

From gene discovery to new biological mechanisms: heparanases and congenital urinary bladder disease

We present a scientific investigation into the pathogenesis of a urinary bladder disease. The disease in question is called urofacial syndrome (UFS), a congenital condition inherited in an autosomal recessive manner. UFS features incomplete urinary bladder emptying and vesicoureteric reflux, with a high risk of recurrent urosepsis and end-stage renal disease. The story starts from a human genomic perspective, then proceeds through experiments that seek to determine the roles of the implicated molecules in embryonic frogs and newborn mice. A future aim would be to use such biological knowledge to intelligently choose novel therapies for UFS. We focus on heparanase proteins and the peripheral nervous system, molecules and tissues that appear to be key players in the pathogenesis of UFS and therefore must also be critical for functional differentiation of healthy bladders. These considerations allow the envisioning of novel biological treatments, although the potential difficulties of targeting the developing bladder in vivo should not be underestimated.

Genetic, environmental, and epigenetic factors involved in CAKUT

Congenital anomalies of the kidney and urinary tract (CAKUT) refer to a spectrum of structural renal malformations and are the leading cause of end-stage renal disease in children. The genetic diagnosis of CAKUT has proven to be challenging due to genetic and phenotypic heterogeneity and incomplete genetic penetrance. Monogenic causes of CAKUT have been identified using different approaches, including single gene screening, and gene panel and whole exome sequencing. The majority of the identified mutations, however, lack substantial evidence to support a pathogenic role in CAKUT. Copy number variants or single nucleotide variants that are associated with CAKUT have also been identified. Numerous studies support the influence of epigenetic and environmental factors on kidney development and the natural history of CAKUT, suggesting that the pathogenesis of this syndrome is multifactorial. In this Review we describe the current knowledge regarding the genetic susceptibility underlying CAKUT and the approaches used to investigate the genetic basis of CAKUT. We outline the associated environmental risk factors and epigenetic influences on CAKUT and discuss the challenges and strategies used to fully address the involvement and interplay of these factors in the pathogenesis of the disease.

Genetic etiology of renal agenesis: fine mapping of Renag1 and identification of Kit as the candidate functional gene

Congenital anomalies of the kidney and urogenital tract (CAKUT) occur in approximately 0.5% of live births and represent the most frequent cause of end-stage renal disease in neonates and children. The genetic basis of CAKUT is not well defined. To understand more fully the genetic basis of one type of CAKUT, unilateral renal agenesis (URA), we are studying inbred ACI rats, which spontaneously exhibit URA and associated urogenital anomalies at an incidence of approximately 10%. URA is inherited as an incompletely dominant trait with incomplete penetrance in crosses between ACI and Brown Norway (BN) rats and a single responsible genetic locus, designated Renag1, was previously mapped to rat chromosome 14 (RNO14). The goals of this study were to fine map Renag1, identify the causal genetic variant responsible for URA, confirm that the Renag1 variant is the sole determinant of URA in the ACI rat, and define the embryologic basis of URA in this rat model. Data presented herein localize Renag1 to a 379 kilobase (kb) interval that contains a single protein coding gene, Kit (v-kit Hardy-Zukerman 4 feline sarcoma viral oncogene homolog); identify an endogenous retrovirus-derived long terminal repeat located within Kit intron 1 as the probable causal variant; demonstrate aberrant development of the nephric duct in the anticipated number of ACI rat embryos; and demonstrate expression of Kit and Kit ligand (Kitlg) in the nephric duct. Congenic rats that harbor ACI alleles at Renag1 on the BN genetic background exhibit the same spectrum of urogenital anomalies as ACI rats, indicating that Renag1 is necessary and sufficient to elicit URA and associated urogenital anomalies. These data reveal the first genetic link between Kit and URA and illustrate the value of the ACI rat as a model for defining the mechanisms and cell types in which Kit functions during urogenital development.

Pediatric urology patients with megaureter may have a risk of contracting Crohn disease

Crohn disease (CD) may develop at any age, but is most typically diagnosed in late adolescence and early adulthood. To the best of our knowledge, there are no reports showing that congenital urological abnormalities may be associated to CD. We describe 5 pediatric patients who had ureteral/urethral abnormalities in their infancy and developed CD during subsequent years. The occurrence of CD in these patients constitutes a novel potential association.

Nephric duct insertion requires EphA4/EphA7 signaling from the pericloacal mesenchyme

The vesico-ureteric junction (VUJ) forms through a complex developmental program that connects the primordium of the upper urinary tract [the nephric duct (ND)] with that of the lower urinary tract (the cloaca). The signals that orchestrate the various tissue interactions in this program are poorly understood. Here, we show that two members of the EphA subfamily of receptor tyrosine kinases, EphA4 and EphA7, are specifically expressed in the mesenchyme surrounding the caudal ND and the cloaca, and that Epha4−/−;Epha7+/− and Epha4−/−;Epha7−/− (DKO) mice display distal ureter malformations including ureterocele, blind and ectopically ending ureters with associated hydroureter, megaureter and hydronephrosis. We trace these defects to a late or absent fusion of the ND with the cloaca. In DKO embryos, the ND extends normally and approaches the cloaca but the tip subsequently looses its integrity. Expression of Gata3 and Lhx1 and their downstream target Ret is severely reduced in the caudal ND. Conditional deletion of ephrin B2 from the ND largely phenocopies these changes, suggesting that EphA4/EphA7 from the pericloacal mesenchyme signal via ephrin B2 to mediate ND insertion. Disturbed activity of this signaling module may entail defects of the VUJ, which are frequent in the spectrum of congenital anomalies of the kidney and the urinary tract (CAKUT) in human newborns.

Genome-wide analysis of gestational gene-environment interactions in the developing kidney

The G protein-coupled bradykinin B2 receptor (Bdkrb2) plays an important role in regulation of blood pressure under conditions of excess salt intake. Our previous work has shown that Bdkrb2 also plays a developmental role since Bdkrb2(-/-) embryos, but not their wild-type or heterozygous littermates, are prone to renal dysgenesis in response to gestational high salt intake. Although impaired terminal differentiation and apoptosis are consistent findings in the Bdkrb2(-/-) mutant kidneys, the developmental pathways downstream of gene-environment interactions leading to the renal phenotype remain unknown. Here, we performed genome-wide transcriptional profiling on embryonic kidneys from salt-stressed Bdkrb2(+/+) and Bdkrb2(-/-) embryos. The results reveal significant alterations in key pathways regulating Wnt signaling, apoptosis, embryonic development, and cell-matrix interactions. In silico analysis reveal that nearly 12% of differentially regulated genes harbor one or more Pax2 DNA-binding sites in their promoter region. Further analysis shows that metanephric kidneys of salt-stressed Bdkrb2(-/-) have a significant downregulation of Pax2 gene expression. This was corroborated in Bdkrb2(-/-);Pax2(GFP+/tg) mice, demonstrating that Pax2 transcriptional activity is significantly repressed by gestational salt-Bdkrb2 interactions. We conclude that gestational gene (Bdkrb2) and environment (salt) interactions cooperate to impact gene expression programs in the developing kidney. Suppression of Pax2 likely contributes to the defects in epithelial survival, growth, and differentiation in salt-stressed BdkrB2(-/-) mice.

DLG1 influences distal ureter maturation via a non-epithelial cell autonomous mechanism involving reduced retinoic acid signaling, Ret expression, and apoptosis

The absence of Discs-large 1 (DLG1), the mouse ortholog of the Drosophila discs-large tumor suppressor, results in congenital hydronephrosis characterized by urinary tract abnormalities, reduced ureteric bud branching, and delayed disconnection of the ureter from the common nephric duct (CND). To define the specific cellular requirements for Dlg1 expression during urogenital development, we used a floxed Dlg1 allele and Pax2-Cre, Pax3-Cre, Six2-Cre, and HoxB7-Cre transgenes to generate cell type-restricted Dlg1 mutants. In addition, we used Ret(GFP) knockin and retinoic acid response element-lacZ transgenic mice to determine the effects of Dlg1 mutation on the respective morphogenetic signaling pathways. Mutation of Dlg1 in urothelium and collecting ducts (via HoxB7-Cre or Pax2-Cre) and in nephron precursors (via Pax2-Cre and Six2-Cre) resulted in no apparent abnormalities in ureteric bud branching or in distal ureter maturation, and no hydronephrosis. Mutation in nephrons, ureteric smooth muscle, and mesenchyme surrounding the lower urinary tract (via the Pax3-Cre transgene) resulted in congenital hydronephrosis accompanied by reduced branching, abnormal distal ureter maturation and insertion, and smooth muscle orientation defects, phenotypes very similar to those in Dlg1 null mice. Dlg1 null mice showed reduced Ret expression and apoptosis during ureter maturation and evidence of reduced retinoic acid signaling in the kidney. Taken together, these results suggest that Dlg1 expression in ureter and CND-associated mesenchymal cells is essential for ensuring distal ureter maturation by facilitating retinoic acid signaling, Ret expression, and apoptosis of the urothelium.

Genetics of human congenital urinary bladder disease

Lower urinary tract and/or kidney malformations are collectively the most common cause of end-stage renal disease in children, and they are also likely to account for a major subset of young adults requiring renal replacement therapy. Advances have been made regarding the discovery of the genetic causes of human kidney malformations. Indeed, testing for mutations of key nephrogenesis genes is now feasible for patients seen in nephrology clinics. Unfortunately, less is known about defined genetic bases of human lower urinary tract anomalies. The focus of this review is the genetic bases of congenital structural and functional disorders of the urinary bladder. Three are highlighted. First, prune belly syndrome, where mutations of CHRM3, encoding an acetylcholine receptor, HNF1B, encoding a transcription factor, and ACTA2, encoding a cytoskeletal protein, have been reported. Second, the urofacial syndrome, where mutations of LRIG2 and HPSE2, encoding proteins localised in nerves invading the fetal bladder, have been defined. Finally, we review emerging evidence that bladder exstrophy may have genetic bases, including variants in the TP63 promoter. These genetic discoveries provide a new perspective on a group of otherwise poorly understood diseases.

Genomic and epigenomic analyses of monozygotic twins discordant for congenital renal agenesis

Monozygotic twins have been widely studied to distinguish genetic and environmental factors in the pathogenesis of human diseases. For renal agenesis, the one-sided absence of renal tissue, the relative contributions of genetic and environmental factors to its pathogenesis are still unclear. In this study of a pair of monozygotic twins discordant for congenital renal agenesis, the genomic profile was analyzed from a set of blood samples using high-throughput exome-capture sequencing to detect single-nucleotide polymorphisms (SNPs), copy number variations (CNVs), and insertions and deletions (indels). Also, an epigenomic analysis used reduced-representation bisulfite sequencing to detect differentially methylated regions (DMRs). No discordant SNPs, CNVs, or indels were confirmed, but 514 DMRs were detected. KEGG analysis indicated the DMRs localized to 10 signaling pathways and 25 genes, including the mitogen-activated protein kinase pathway and 6 genes (FGF18, FGF12, PDGFRA, MAPK11, AMH, CTBP1) involved in organ development. Although methylation results from our adult patient and her sister may not represent the pattern that was present during kidney development, we could at least confirm a lack of obvious differences at the genome level, which suggests that nongenetic factors may be involved in the pathogenesis of renal agenesis.

Paediatric end-stage renal disease in a tertiary hospital in South West Nigeria

Background

Children and adolescents with end-stage renal disease (ESRD) in sub-Saharan Africa may have the worst outcomes globally. Barriers to management include late presentation, poor socioeconomic conditions, absence of medical insurance, limited diagnostic facilities and non-availability of chronic renal replacement therapy (RRT). Our study was to determine the incidence, aetiology, management and outcomes of paediatric ESRD in a tertiary hospital in Nigeria.

Methods

A retrospective case review of paediatric ESRD at the University College Hospital Ibadan, Nigeria, over 8 years, from January 2005 to December 2012.

Results

53 patients (56.6% male), median age 11 (inter quartile range 8.5-12) years were studied. Mean annual incidence of ESRD in Ibadan for children aged 14 years and below was 4 per million age related population (PMARP) while for those aged 5-14 years it was 6.0 PMARP. Glomerulonephritis was the cause in 41 (77.4%) patients amongst whom, 29 had chronic glomerulonephritis and 12 had nephrotic syndrome. Congenital anomalies of the kidneys and urinary tract (CAKUT) accounted for 11 (21.2%) cases, posterior urethral valves being the most common. Acute haemodialysis, acute peritoneal dialysis or a combination of these were performed in 33 (62.3%), 6 (11.3%) and 4 (7.5%) patients respectively. Median survival was 47 days and in-hospital mortality was 59%.

Conclusions

Incidence of paediatric ESRD in Ibadan is higher than previous reports from sub-Saharan Africa. Glomerulonephritis, and then CAKUT are the most common causes. Mortality is high, primarily due to lack of resources. Preventive nephrology and chronic RRT programmes are urgently needed.

Lower urinary tract development and disease

Congenital anomalies of the lower urinary tract (CALUT) are a family of birth defects of the ureter, the bladder, and the urethra. CALUT includes ureteral anomaliesc such as congenital abnormalities of the ureteropelvic junction (UPJ) and ureterovesical junction (UVJ), and birth defects of the bladder and the urethra such as bladder-exstrophy-epispadias complex (BEEC), prune belly syndrome (PBS), and posterior urethral valves (PUVs). CALUT is one of the most common birth defects and is often associated with antenatal hydronephrosis, vesicoureteral reflux (VUR), urinary tract obstruction, urinary tract infections (UTI), chronic kidney disease, and renal failure in children. Here, we discuss the current genetic and molecular knowledge about lower urinary tract development and genetic basis of CALUT in both human and mouse models. We provide an overview of the developmental processes leading to the formation of the ureter, the bladder, and the urethra, and different genes and signaling pathways controlling these developmental processes. Human genetic disorders that affect the ureter, the bladder and the urethra and associated gene mutations are also presented. As we are entering the postgenomic era of personalized medicine, information in this article may provide useful interpretation for the genetic and genomic test results collected from patients with lower urinary tract birth defects. With evidence-based interpretations, clinicians may provide more effective personalized therapies to patients and genetic counseling for their families.

Renal hypodysplasia associates with a WNT4 variant that causes aberrant canonical WNT signaling

Abnormal differentiation of the renal stem/progenitor pool into kidney tissue can lead to renal hypodysplasia (RHD), but the underlying causes of RHD are not well understood. In this multicenter study, we identified 20 Israeli pedigrees with isolated familial, nonsyndromic RHD and screened for mutations in candidate genes involved in kidney development, including PAX2, HNF1B, EYA1, SIX1, SIX2, SALL1, GDNF, WNT4, and WT1. In addition to previously reported RHD-causing genes, we found that two affected brothers were heterozygous for a missense variant in the WNT4 gene. Functional analysis of this variant revealed both antagonistic and agonistic canonical WNT stimuli, dependent on cell type. In HEK293 cells, WNT4 inhibited WNT3A induced canonical activation, and the WNT4 variant significantly enhanced this inhibition of the canonical WNT pathway. In contrast, in primary cultures of human fetal kidney cells, which maintain WNT activation and more closely represent WNT signaling in renal progenitors during nephrogenesis, this mutation caused significant loss of function, resulting in diminished canonical WNT/β-catenin signaling. In conclusion, heterozygous WNT4 variants are likely to play a causative role in renal hypodysplasia.

Genome-wide ENU mutagenesis in combination with high density SNP analysis and exome sequencing provides rapid identification of novel mouse models of developmental disease

BACKGROUND

Mice harbouring gene mutations that cause phenotypic abnormalities during organogenesis are invaluable tools for linking gene function to normal development and human disorders. To generate mouse models harbouring novel alleles that are involved in organogenesis we conducted a phenotype-driven, genome-wide mutagenesis screen in mice using the mutagen N-ethyl-N-nitrosourea (ENU).

METHODOLOGY/PRINCIPAL FINDINGS

ENU was injected into male C57BL/6 mice and the mutations transmitted through the germ-line. ENU-induced mutations were bred to homozygosity and G3 embryos screened at embryonic day (E) 13.5 and E18.5 for abnormalities in limb and craniofacial structures, skin, blood, vasculature, lungs, gut, kidneys, ureters and gonads. From 52 pedigrees screened 15 were detected with anomalies in one or more of the structures/organs screened. Using single nucleotide polymorphism (SNP)-based linkage analysis in conjunction with candidate gene or next-generation sequencing (NGS) we identified novel recessive alleles for Fras1, Ift140 and Lig1.

CONCLUSIONS/SIGNIFICANCE

In this study we have generated mouse models in which the anomalies closely mimic those seen in human disorders. The association between novel mutant alleles and phenotypes will lead to a better understanding of gene function in normal development and establish how their dysfunction causes human anomalies and disease.

Unilateral renal agenesis: a systematic review on associated anomalies and renal injury

BACKGROUND

Unilateral renal agenesis (URA) is associated with other congenital anomalies of the kidney and urinary tract (CAKUT) and extra-renal anomalies. However, the reported prevalences of these anomalies are highly variable. We estimated the prevalence of associated CAKUT and extra-renal anomalies in patients with URA. Furthermore, we determined the prevalence of renal injury in URA patients.

METHODS

We conducted a systematic review of English and non-English articles using PubMed and Embase.com. Included studies reported at least one of the following items: incidence of URA, gender, side of URA, prenatal diagnosis, performance of micturating cystourethrogram, associated CAKUT, urinary tract infection or extra-renal anomalies. Studies that described a mean/median glomerular filtration rate (GFR) and proportions of patients with hypertension, micro-albuminuria or a decreased GFR were also included.

RESULTS

Analyses were based on 43 included studies (total number of patients: 2684, 63% male). The general incidence of URA was 1 in ∼2000. Associated CAKUT were identified in 32% of patients, of which vesicoureteral reflux was most frequently identified (24% of patients). Extra-renal anomalies were found in 31% of patients. Hypertension could be identified in 16% of patients, whereas 21% of patients had micro-albuminuria. Ten per cent of patients had a GFR<60 mL/min/1.73 m2;.

CONCLUSIONS

These aggregate results provide insight in the prevalence of associated anomalies and renal injury in patients with URA. Our systematic review implicates that URA is not a harmless malformation by definition. Therefore, we emphasize the need for clinical follow-up in URA patients starting at birth.

LRIG2 mutations cause urofacial syndrome

Urofacial syndrome (UFS) (or Ochoa syndrome) is an autosomal-recessive disease characterized by congenital urinary bladder dysfunction, associated with a significant risk of kidney failure, and an abnormal facial expression upon smiling, laughing, and crying. We report that a subset of UFS-affected individuals have biallelic mutations in LRIG2, encoding leucine-rich repeats and immunoglobulin-like domains 2, a protein implicated in neural cell signaling and tumorigenesis. Importantly, we have demonstrated that rare variants in LRIG2 might be relevant to nonsyndromic bladder disease. We have previously shown that UFS is also caused by mutations in HPSE2, encoding heparanase-2. LRIG2 and heparanase-2 were immunodetected in nerve fascicles growing between muscle bundles within the human fetal bladder, directly implicating both molecules in neural development in the lower urinary tract.

Congenital anomalies of kidney and hand: a review

‘Acro-renal syndrome’ refers to co-occurrence of congenital renal and limb anomalies. The term acro-renal syndrome was coined by Curran et al. in 1972 though Dieker and Opitz were the first to report this phenomenon in three male patients in 1969. The common limb defects include oligodactyly, ectrodactyly, syndactyly or brachydactyly anomalies of the carpal and tarsal bones and the common renal anomalies observed are unilateral renal agenesis (URA), bilateral renal hypoplasia, ureteric hypoplasia, hydroureteronephrosis and duplication abnormalities. The acro-renal syndrome as originally described is rare, reported only in ∼20 patients in the international literature. We report a 23-year-old male patient with renal anomalies in the form of absent right kidney, left-sided vesicoureteric reflux (VUR) and skeletal anomalies viz short radius, absent first metacarpal ray in left hand and left undescended testis, consistent with Dieker's type acro-renal syndrome. Apart from the classical acro-renal syndrome, several anomalies of acro-renal patterns and the abnormal gene loci involved are described in the literature. This article is a comprehensive review of the development of kidneys, types of acro-renal syndromes, congenital anomalies of the kidney and urinary tract (CAKUT), syndromes associated with combined limb and renal anomalies, and anomalies associated with URA.

Cell biology of ureter development

The mammalian ureter contains two main cell types: a multilayered water-tight epithelium called the urothelium, surrounded by smooth muscle layers that, by generating proximal to distal peristaltic waves, pump urine from the renal pelvis toward the urinary bladder. Here, we review the cellular mechanisms involved in the development of these tissues, and the molecules that control the process. We consider the relevance of these biologic findings for understanding the pathogenesis of human ureter malformations.

Novel perspectives for investigating congenital anomalies of the kidney and urinary tract (CAKUT)

Congenital anomalies of the kidney and urinary tract (CAKUT) are the commonest cause of chronic kidney disease in children. Structural anomalies within the CAKUT spectrum include renal agenesis, kidney hypo-/dysplasia, multicystic kidney dysplasia, duplex collecting system, posterior urethral valves and ureter abnormalities. While most CAKUT cases are sporadic, familial clustering of CAKUT is common, emphasizing a strong genetic contribution to CAKUT origin. Animal experiments demonstrate that alterations in genes crucial for kidney development can cause experimental CAKUT, while expression studies implicate mislocalization and/or aberrant levels of the encoded proteins in human CAKUT. Further insight into the pathogenesis of CAKUT will improve strategies for early diagnosis, follow-up and treatment. Here, we outline a collaborative approach to identify and characterize novel factors underlying human CAKUT. This European consortium will share the largest collection of CAKUT patients available worldwide and undertake multidisciplinary research into molecular and genetic pathogenesis, with extension into translational studies to improve long-term patient outcomes.

Malformations in a cohort of 284 women with Mayer-Rokitansky-Küster-Hauser syndrome (MRKH)

BACKGROUND

The aim of this retrospective study was to describe the spectrum of genital and associated malformations in women with Mayer-Rokitansky-Küster-Hauser syndrome using evaluated diagnostic procedures and the Vagina Cervix Uterus Adnex - associated Malformation classification system (VCUAM).

METHODS

290 women with MRKH syndrome were clinically evaluated with using clinical examinations, abdominal and perineal/rectal ultrasound, MRI, and laparoscopy.

RESULTS

Classification of female genital malformation according to the Vagina Cervix Uterus Adnex - associated Malformation classification system was possible in 284 women (97.9%). Complete atresia of Vagina (V5b) and bilateral atresia of Cervix (C2b) were found in 284 patients (100%). Uterus: bilateral rudimentary or a plastic uterine horns were found in 239 women (84.2%). Adnexa: normal Adnexa were found in 248 women (87.3%). Malformations: associated malformations were found in 126 of 282 evaluable women (44.7%), 84 women (29.6%) had malformations of the renal system. Of 284 women with Mayer-Rokitansky-Küster-Hauser syndrome 212 women (74.7%) could be classified as V5bC2bU4bA0. The most frequent classification was V5bC2bU4bA0M0 (46.8%) diagnosed in 133 of 284 women.

CONCLUSIONS

Complete atresia of vagina and cervix were found in all patients, variable malformations were found with uterus and adnexa. A variety of associated malformations were present, predominantly of the renal system. It is therefore recommended that all patients with genital malformations should be evaluated for renal abnormalities.

Prenatal ultrasound and urological anomalies

Prenatal ultrasound is an integral part of caring for pregnant women in the United States. Although surprisingly few data exist to support the clinical benefit of screening ultrasound during pregnancy, its use continues to rise. Urologic anomalies are among the most commonly identified, with overall detection sensitivity approaching 90%. Prenatal hydronephrosis is the most frequently identified finding and predicting postnatal pathology based on its presence can be difficult. As the degree of fetal hydronephrosis increases so does the risk of true urinary tract pathology. Diagnoses that require more urgent care include causes of lower urinary tract obstruction and bladder and cloacal exstrophy.

Renal stem cells: fact or science fiction?

The kidney is widely regarded as an organ without regenerative abilities. However, in recent years this dogma has been challenged on the basis of observations of kidney recovery following acute injury, and the identification of renal populations that demonstrate stem cell characteristics in various species. It is currently speculated that the human kidney can regenerate in some contexts, but the mechanisms of renal regeneration remain poorly understood. Numerous controversies surround the potency, behaviour and origins of the cell types that are proposed to perform kidney regeneration. The present review explores the current understanding of renal stem cells and kidney regeneration events, and examines the future challenges in using these insights to create new clinical treatments for kidney disease.

Ultrasound mass screening for congenital anomalies of the kidney and urinary tract

BACKGROUND

There is a high incidence of congenital anomalies of the kidneys and urinary tract (CAKUT). Early diagnosis of these defects may allow the best medical and/or surgical treatment to be implemented as rapidly as possible, preventing or at least slowing down an evolution toward chronic kidney disease.

METHODS

Ultrasound mass screening for kidney and urinary tract abnormalities in infants at 2 months of age was carried out in Salento, Italy. The centers involved in the study examined a total of 17,783 infants between January 1992 and December 2010.

RESULTS

A total of 171 CAKUT were identified in the course of the mass screening. The frequency of CAKUT was 0.96%. Vesicoureteral reflux (n = 39) was the most frequent renal abnormality found, followed by ureteropelvic junction obstruction (n = 33), ectopic kidney (n = 26), and renal dysplasia (n = 19). In addition, nephrogenic rests (n = 2), as well as several extra-renal pathologies, including abdominal neuroblastoma (n = 3), were diagnosed incidentally.

CONCLUSION

Ultrasound has been effective for early detection of renal and urinary tract anomalies. In addition, this screening has proved to be very useful for the early identification and management of both renal and extra-renal precancerous as well as cancerous lesions. However, most patients requiring surgery in this study (0.24%) would probably have been symptomatic and come to medical attention without routine screening. On the basis of our results screening is not justified.

Early risk factors for neonatal mortality in CAKUT: analysis of 524 affected newborns

BACKGROUND

Congenital abnormalities of the kidney and urinary tract (CAKUT) are significant causes of morbidity. The aim of the study was to determine predictive factors of mortality in newborns with CAKUT.

METHODS

All 29,653 consecutive newborns hospitalized in a tertiary neonatal unit between 1996 and 2006 were evaluated. The main outcome was neonatal mortality. The variables analyzed as risk factors were maternal age, first pregnancy, low birth weight (LBW), prematurity, oligohydramnios, and CAKUT associated with other malformations (Associated CAKUT).

RESULTS

CAKUT was detected in 524 newborns, with an overall prevalence of 17.7 per 1,000 live births. A total of 325 (62%) cases were classified as urinary tract dilatation, 79 (15.1%) as renal cystic disease, and 120 (22.9%) as other subgroups. In the urinary tract dilatation subgroup, independent risk factors for early mortality were Associated CAKUT [odds ratio (OR) 20.7], prematurity (OR 4.5) LBW (OR 3.8), oligohydramnios (OR 3.0), and renal involvement (OR 3.0). In the renal cystic disease subgroup, two variables remained associated with neonatal mortality: LBW (OR 12.3) and Associated CAKUT (OR 21.4).

CONCLUSION

The presence of extrarenal anomalies was a strong predictor of poor outcome in a larger series of infants with CAKUT.