A family study and the natural history of prenatally detected unilateral multicystic dysplastic kidney

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSION

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

Screening for Renal and Urinary Tract Anomalies in Asymptomatic First Degree Relatives of Children with Congenital Anomalies of the Kidney and Urinary Tract (CAKUT)

OBJECTIVE

To estimate the frequency of renal and urinary tract anomalies in first-degree relatives of children with Congenital anomalies of kidney and urinary tract (CAKUT).

METHODS

This descriptive study was conducted on parents and siblings of 138 children with CAKUT. Renal ultrasonogram, radionuclide diuretic renogram and micturating cysturethrogram were the tools used for screening these family members.

RESULTS

Asymptomatic first-degree relatives of 138 children [total of 270 first-degree relatives (95 fathers, 97 mothers and 78 siblings)] were screened, with new anomalies detected in 11 first-degree relatives (4% out of 270 first-degree relatives screened) from 11 families (7.9% out of 138 families screened). The anomalies detected were vesicoureteric reflux (VUR) (n = 2), non-obstructive non-refluxing hydronephrosis (n = 2), pelviureteral junction obstruction (PUJO) (n = 3), Duplex collecting system (n = 1), hypodysplastic kidney (n = 1), single kidney (n = 1) and horseshoe kidney (n = 1). Most of the anomalies were discordant to the index anomaly (66.6%). Among 95 fathers screened, 5 (5.2%) had renal anomalies. Among 97 mothers screened, 2 (2.1%) had renal anomalies. Among the 78 siblings screened, 4 (5.1%) had renal anomalies.

CONCLUSIONS

Familial clustering was noted in 7.9% of the 138 families (of the index cases) screened. The anomalies detected were mostly discordant to the index anomaly.

A meta-analysis of the incidence and fate of contralateral vesicoureteral reflux in unilateral multicystic dysplastic kidney

INTRODUCTION

Multicystic dysplastic kidney (MCDK) is the most common type of renal cystic disease. It is associated with urinary tract abnormalities in the contralateral kidney in up to 30% of cases, most commonly vesicoureteral reflux (VUR).

OBJECTIVES

The objective of this study was to describe the incidence and selected issues in management and evolution for each VUR grade in the contralateral kidney of patients with unilateral MCDK, in order to strengthen the scientific basis regarding the need for voiding cystourethrography (VCUG) screening.

METHODS

A comprehensive search of standard and gray literature was performed. Full-text screening, data abstraction, and quality appraisal were conducted in duplicates. Included studies reported a primary diagnosis of unilateral MCDK with contralateral VUR determined by VCUG. Articles had to include a distribution of VUR grade to meet the eligibility criteria.

RESULTS

From 698 retrieved articles, 37 studies enrolling 2057 patients were analyzed. Of the patients, 80% were male; 50% had left unilateral MCDK; and 87% were diagnosed prenatally. A total of 1800 patients had VCUG, of whom 303 had VUR (weighted proportion: 17%; 95% confidence interval [CI]: 14-20%). Weighted proportions of VUR were 9%, 7%, and 17% for grades I-II, III-V, and I-V, respectively. Of the patients, 99% (95% CI: 97-100%) were on continuous antibiotic prophylaxis (CAP) and 18% (95% CI: 8-37%) had urinary tract infections (UTIs), with a higher rate of UTIs (23% vs 10%) in patients with dilating (grades III-V) VUR, over a mean follow-up of 40 months. In patients with dilating VUR, reflux resolved or downgraded to grade I in 52% (95% CI: 37-67%) of patients, and 32% (95% CI: 19-49%) had surgical correction of VUR.

CONCLUSIONS

Among patients with unilateral MCDK, 17% have VUR in the contralateral kidney, 41% of which is dilating VUR. Of the cases with dilating VUR, half will resolve or downgrade to grade I during follow-up; 23% will develop a UTI despite CAP; and one-third will undergo ureteral re-implantation. While many physicians may thus choose to forego routine VCUG screening of the single functional kidney, shared decision-making with the patient's caregivers is currently recommended, where the risks and benefits of the different approaches can be discussed. The data from this analysis can help inform the discussions.

Diagnostic and therapeutic challenges of an ambiguous cystic kidney disease in a resource limited setting: a case report

Background

Unilateral renal cystic disease is a rare condition that shares morphological similarities with multicystic dysplastic kidney, the former often distinguished from the latter on some clinical and histopathological grounds. However serious diagnostic and therapeutic dilemmas set in when there is a considerable overlap in the distinguishing features between these entities.

Case presentation

A 19-year-old African female presented with a chronic severe debilitating right lower quadrant abdominal pain refractory to analgesics. Biochemical investigations and imaging studies revealed a non-functional polycystic right kidney and no identifiable pelvicalyceal system or ureter but with preserved renal function. The marked overlap in clinical presentation between unilateral renal cystic disease and multicystic dysplastic kidney in this patient necessitated further investigation to pose an appropriate diagnosis. A right nephrectomy was performed and histopathological analysis of the resected kidney done, the results of which were more consistent with unilateral renal cystic disease. The post-operative course was favorable.

Conclusion

Unilateral renal cystic disease with an ipsilateral non-functional kidney and an atretic pelvicalyceal system is a very rare condition that needs to be distinguished from multicystic dysplastic kidney in order to guide management and set prognosis. A suspicion of either of these diseases therefore warrants a thorough clinical evaluation and the appropriate combination of biochemical and imaging investigations.

Transcriptional dysregulation in the ureteric bud causes multicystic dysplastic kidney by branching morphogenesis defect

PURPOSE

The calcineurin-NFAT signaling pathway regulates the transcription of genes important for development. It is impacted by various genetic and environmental factors. We investigated the potential role of NFAT induced transcriptional dysregulation in the pathogenesis of congenital abnormalities of the kidneys and urinary tract.

MATERIALS AND METHODS

A murine model of conditional NFATc1 activation in the ureteric bud was generated and examined for histopathological changes. Metanephroi were also cultured in vitro to analyze branching morphogenesis in real time.

RESULTS

NFATc1 activation led to defects resembling multicystic dysplastic kidney. These mutants showed severe disorganization of branching morphogenesis characterized by decreased ureteric bud branching and the disconnection of ureteric bud derivatives from the main collecting system. The orphan ureteric bud derivatives may have continued to induce nephrogenesis and likely contributed to the subsequent formation of blunt ended filtration units and cysts. The ureter also showed irregularities consistent with impaired epithelial-mesenchymal interaction.

CONCLUSIONS

This study reveals the profound effects of NFAT signaling dysregulation on the ureteric bud and provides insight into the pathogenesis of multicystic dysplastic kidney. Our results suggest that the obstruction hypothesis and the bud theory may not be mutually exclusive to explain the pathogenesis of multicystic dysplastic kidney. Ureteric bud dysfunction such as that induced by NFAT activation can disrupt ureteric bud-metanephric mesenchyma interaction, causing primary defects in branching morphogenesis, subsequent dysplasia and cyst formation. Obstruction of the main collecting system can further enhance these defects, producing the pathological changes associated with multicystic dysplastic kidney.

Next-generation sequencing for research and diagnostics in kidney disease

The advent of next-generation sequencing technologies has enabled genetic nephrology research to move beyond single gene analysis to the simultaneous investigation of hundreds of genes and entire pathways. These new sequencing approaches have been used to identify and characterize causal factors that underlie inherited heterogeneous kidney diseases such as nephronophthisis and congenital anomalies of the kidney and urinary tract. In this Review, we describe the development of next-generation sequencing in basic and clinical research and discuss the implementation of this novel technology in routine patient management. Widespread use of targeted and nontargeted approaches for gene identification in clinical practice will require consistent phenotyping, appropriate disease modelling and collaborative efforts to combine and integrate data analyses. Next-generation sequencing is an exceptionally promising technique that has the potential to improve the management of patients with inherited kidney diseases. However, identifying the molecular mechanisms that lead to renal developmental disorders and ciliopathies is difficult. A major challenge in the near future will be how best to integrate data obtained using next-generation sequencing with personalized medicine, including use of high-throughput disease modelling as a tool to support the clinical diagnosis of kidney diseases.

High frequency of kidney and urinary tract anomalies in asymptomatic first-degree relatives of patients with CAKUT

BACKGROUND

Congenital anomalies of the kidney and urinary tract (CAKUT) commonly cause chronic kidney disease in children. While most CAKUT cases are sporadic, observed familial clustering suggests that the pathogenesis is influenced by genetic factors.

METHODS

The purpose of the present study is to determine the frequency of the kidney and urinary tract anomalies in asymptomatic first-degree relatives of patients with CAKUT. A total of 218 index patients and their families followed at an academic hospital in Ankara, Turkey, were enrolled in the study.

RESULTS

Family histories revealed at least one other member with a known kidney or urinary tract disease in 50% and CAKUT in 22.9% of the families. All asymptomatic first-degree relatives of 180 index patients were screened for kidney and urinary tract anomalies using ultrasound. New anomalies were diagnosed in 116 asymptomatic first-degree relatives (23%) in 87 families (48.3%). When family histories and ultrasound findings of 180 index patients were evaluated together, 129 first-degree relatives in 92 families (51.1%) had CAKUT.

CONCLUSIONS

This study suggests that genetic mechanisms might be very important in the pathogenesis of apparently sporadic CAKUT. Identification of the underlying gene mutations will provide further insights into the knowledge of the kidney and urinary tract development and pathogenesis of CAKUT.

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.

Laparoscopic nephrectomy for pelvic multicystic dysplastic kidney

The management of multicystic dysplastic kidney (MCDK) is controversial. There has been a shift from routine surgical removal to nonoperative management. However, recently, an argument has emerged with regard to the management of MCDK, with several studies recommending surgical removal. We report a case of pelvic MCDK that was diagnosed and subsequently removed by a laparoscopic procedure. A laparoscopic approach to the renal and pelvic areas is a minimally invasive, safe, and effective procedure to diagnose and treat MCDK. We believe that laparoscopic nephrectomy should be offered as a management option to the families of children with unilateral MCDK.

Genetics of kidney development: pathogenesis of renal anomalies

Congenital anomalies of the kidney and urinary tract (CAKUT) account for more than 50% of abdominal masses found in neonates and involve about 0.5% of all pregnancies. CAKUT has a major role in renal failure, and increasing evidence suggests that certain abnormalities predispose to the development of hypertension and cardiovascular disease in adulthood. To understand the pathogenesis of human renal anomalies, understanding the development of kidney is important. Diverse anomalies of the kidney corresponding to defects at a particular stage of development have been documented recently; however, more research is required to understand the molecular networks underlying kidney development, and such an investigation will provide a clue to the therapeutic intervention for CAKUT.

Analysis of TSHZ2 and TSHZ3 genes in congenital pelvi-ureteric junction obstruction

BACKGROUND

Congenital pelvi-ureteric junction obstruction (PUJO) affects 0.3% of human births. It may result from aberrant smooth muscle development in the renal pelvis, resulting in hydronephrosis. Mice that are null mutant for the Teashirt3 (Tshz3) gene exhibit congenital PUJO with defective smooth muscle differentiation and absent peristalsis in the proximal ureter.

METHODS

Given the phenotype of Tshz3 mutant mice, we considered that Teashirt genes, which code for a family of transcription factors, might represent candidate genes for human PUJO. To evaluate this possibility, we used in situ hydridization to analyse the three mammalian Tshz genes in mouse embryonic ureters and determined whether TSHZ3 was expressed in the human embryonic ureter. TSHZ2 and TSHZ3 were sequenced in index cases with non-syndromic PUJO.

RESULTS

Tshz2 and Tshz3 genes were detected in mouse ureters and TSHZ3 was expressed in the human embryonic renal pelvis. Direct sequencing of TSHZ2 and TSHZ3 did not identify any mutations in an initial cohort of 48 PUJO index cases, excluding these genes as a major cause of this condition. A polymorphic missense change (E469G) in TSHZ3 was identified at a residue highly conserved throughout evolution in all Teashirt proteins, although subsequently no significant difference between the E469G allele frequency in Albanian and Macedonian PUJO index cases (3.2%) versus 633 control individuals (1.7%) was found (P = 0.18).

CONCLUSIONS

Mutations in TSHZ2 and TSHZ3 are not a major cause of PUJO, at least in Albanian and Macedonian populations. Expression of these genes in the human fetal ureter emphasizes the importance of analysing these genes in other groups of patients with renal tract malformations.

Management and etiology of the unilateral multicystic dysplastic kidney: a review

In children, unilateral multicystic dysplastic kidney (MCDK) is one of the most frequently identified urinary tract abnormalities. A variety of proposed etiologies has been associated with the underlying pathogenesis of MCDK. These include genetic disturbances, teratogens, in utero infections, and urinary outflow tract obstruction. From 5-43% of the time, MCDK has associated genito-urinary anomalies, both structural and functional in nature. A review of the literature reveals that involution rates are reported to be 19-73%, compensatory hypertrophy of the contralateral kidney occurs from 24-81% of the time, and estimated glomerular filtration rates (GFRs) (by the Schwartz formula) range from 86-122 ml/min per 1.73 m(2) body surface area. Most authors suggest serial ultrasonography to monitor contralateral growth, routine blood pressure monitoring, and a serum creatinine monitoring algorithm. The risk of hypertension in those with MCDKs does not appear to be greater than that of the general population, and the rates of malignant transformation of MCDK are small, if at all increased, in comparison with those in the general population. If the patient develops a urinary tract infection or has abnormalities of the contralateral kidney, shown on ultrasound, a voiding cystourethrogram is recommended. Finally, the body of literature does not support the routine surgical removal of MCDKs.

Unilateral multicystic dysplastic kidney: a meta-analysis of observational studies on the incidence, associated urinary tract malformations and the contralateral kidney

BACKGROUND

Many papers are published on cohorts with unilateral multicystic dysplastic kidney (MCDK) patients, but show variable results as to the incidence of associated urinary tract abnormalities. The objective of this study was to describe the status of the urinary tract, including contralateral hypertrophy and malformations, in patients with unilateral MCDK based on a meta-analysis of the literature, taking into account the timing of diagnosis (pre- versus postnatal) as a possible source of bias.

METHODS

A systematic review of the scientific literature in English was conducted using PubMed and Embase. A meta-analysis was performed with the studies that were identified using our reproducible search.

RESULTS

Based on analysis of the data in 19 populations, the overall incidence of unilateral MCDK is 1 in 4300 with an increasing trend over the years. A total of 67 cohorts with over 3500 patients with unilateral MCDK were included in the meta-analysis. Fifty-nine percent of patients were male and the MCDKs were significantly more often found on the left side (53.1%). Associated anomalies in the solitary functioning kidney were found in 1 in 3 patients, mainly vesicoureteric reflux (VUR, in 19.7%). In patients with VUR, 40% have severe contralateral VUR, defined as grade III-V. Contralateral hypertrophy, present in 77% of patients after a follow-up of at least 10 years, showed a trend to be less pronounced in patients with VUR. Timing of the diagnosis of MCDK did not essentially influence the results.

CONCLUSIONS

These aggregate results provide insight into the incidence, demographic data and associated anomalies in patients with unilateral MCDK. One in three patients with unilateral MCDK show anomalies in the contralateral, solitary functioning kidney. However, studies into the long-term consequences of these anomalies are scarce.

Unilateral multicystic dysplastic kidney: single-center experience

Multicystic dysplastic kidney (MCDK) is one of the most common renal abnormalities in children. The aim of our study was to evaluate the clinical course and outcome of patients with MCDK. Ninety pediatric patients with unilateral MCDK followed by the Pediatric Nephrology Department of Bakirkoy Maternity and Children's Hospital between 1990 and 2007 were included in this retrospective study. The dimercaptosuccinic acid radionuclide scan revealed no function in MCDK in all of our patients. Voiding cystourethrogram was performed in all patients. Twenty patients (22.2%) had abnormalities in the contralateral kidney. Nephrectomy was performed in 41 patients (45.5%). Twelve patients had undergone routine nephrectomy before 1996. Since then, patients have been followed up conservatively, and nephrectomy has been performed only when indicated. Indication of nephrectomy was arterial hypertension in 16 patients (23.1%), recurrent urinary tract infection (UTI) in 11 (15.9%), and severe abdominal pain in two (2.8%). Hypertension was noted within the first year of life in all patients except two. MCDK completely involuted in 39.3% within 48 months. There was no malignant transformation, proteinuria, or renal failure. In conclusion, hypertension is often noticed in infants with MCDK. Uninephrectomy leads to normalization. However, prospective studies are needed to exclude a spontaneous improvement of hypertension.

Imaging of horseshoe kidneys and their complications

Horseshoe kidney is the most common renal fusion anomaly and the patients are prone to a variety of complications, such as stone disease, pelviureteric junction (PUJ) obstruction, trauma, infections and tumours. As result of the abnormal anatomy of a horseshoe kidney, imaging and treatment pathways vary substantially from the normal kidney. In this review, we describe the role of modern imaging in depicting horseshoe kidneys and their complications, in tandem with the role the interventional radiologist plays in treating these patients.

[Multicystic dysplastic kidney disease: update and information for parents at the time of prenatal diagnosis]

Multicystic kidney disease (MCKD) is the most common form of Congenital Abnormality of Kidney and Urinary Tract (CAKUT). This anomaly of renal development is characterized by unilateral enlarged cystic formations and fibrous dysplastic parenchyma. The long-term prognosis is usually good; however because of reduced nephron mass, an early prevention of cardiovascular risk and nephrotoxicity is recommended. A lifelong follow-up of blood pressure, serum creatinine and microalbuminuria seems logical as well as in other patients with a single kidney. MCKD is usually diagnosed during pregnancy so that parents often question about long-term prognosis and follow-up. Therefore, we propose an information sheet for parents.

Renal anomalies in family members of infants with bilateral renal agenesis/adysplasia

Renal agenesis/adysplasia is the leading etiology of end stage renal disease in children. The etiology for renal agenesis/adysplasia has not been identified. The purpose of the present study was to determine if renal agenesis/adysplasia occur in a familial pattern. Twenty seven cases of bilateral renal agenesis/adysplasia were identified by review of autopsy records, and four were excluded. A male excess of 2.8:1 was noted with a mean gestation of 35 weeks. Prenatal and family histories were obtained on 11/23 families. Potential embryologic stressors were identified in 8/11 pregnancies. Thirty-four 1st and 2nd degree relatives from five families participated in a renal ultrasound exam. An increased prevalence of congenital renal anomalies was identified in the relatives of index patients with bilateral renal agenesis/adysplasia (14.7%) compared to controls (2.2%), with a recurrence risk of 6.2 for 1st degree relatives. The most frequently identified renal anomalies in the family members were solitary kidneys and duplicated collecting systems. The increased prevalence of a range of renal anomalies within affected families raises the possibility that isolated renal malformations result from unidentified gene-environment interactions.

Urological anomalies in children with renal agenesis or multicystic dysplastic kidney

This study aimed to determine the frequency of associated urological abnormalities in children with unilateral renal agenesis (RA) or multicystic dysplastic kidney (MCDK). In total, 38 children (10 girls, 28 boys) were studied: 21 with RA and 17 with MCDK. In 14 children (37%) anomalies of the urinary tract were suspected prenatally in ultrasound studies. In the remaining 24 children the diagnosis of RA/MCDK was made postnatally: in 13 (34%) in the first 7 days of life, in 11 (29%) at the age of 8 days to 34 months, mean 10.6+/-8.05 months. Voiding cystourethrography was done in 36 (95%) children, the isotopic 99mTc-EC/DMSA scan of the kidney in 29 (67%), and urography in 8. Urological anomalies were present in 11 (29%) children: in 7 (33%) with RA and in 4 (24%) with MCDK. Vesicoureteral reflux was diagnosed in 8 children: grade II in 4, III in 3, and IV in 1 (in 1 child to duplicated, in 1 to ectopic kidney); ureterovesical junction obstruction in 2 (9.5%); and ureteropelvic junction obstruction in 1 (4.8%). Among them, 2 children demanded surgery on the contralateral urinary tract: pyeloplasty in 1, antireflux procedure in 1; while 9 children were treated conservatively. Compensatory hypertrophy of the contralateral kidney was found in 90% of children. Thus due to an increased risk of pathological changes in the single functioning kidney, lifelong nephrological care is recommended in patients with unilateral RA/MCDK.

A familial case of multicystic dysplastic kidney

A familial case of multicystic dysplastic kidney (MCDK) is described. The proband is a one-year-old boy with left MCDK, and his father was also revealed to have unilateral MCDK. The mother had two abortions; the second pregnancy was terminated because of bilateral MCDK of the fetus (Potter anomaly). The two patients and the aborted male fetus did not have any malformations except for MCDK. Thus in this family MCDK occurs as an isolated phenomenon in three individuals within two generations, presumably as a result of autosomal dominant inheritance.

Multicystic dysplastic kidney and variable phenotype in a family with a novel deletion mutation of PAX2

The renal coloboma syndrome (OMIM 120330) is caused by mutations in the PAX2 gene. Typical findings in these patients include renal hypoplasia, renal insufficiency, vesicoureteric reflux, and optic disc coloboma. A family with a novel heterozygous 10-bp deletion in exon 2 of the PAX2 gene leading to a truncating mutation and variable phenotype across three generations is reported. The first presentation of multicystic dysplastic kidney in this syndrome is reported. The possibility that abnormal PAX2 protein in this case may cause a dominant negative effect also is discussed. The finding of multicystic dysplastic kidney in renal coloboma syndrome could suggest that PAX2 may play a role in early ureteric obstruction and subsequent renal maldevelopment.

Laparoscopic nephrectomy for unilateral multicystic dysplastic kidney in children

The contemporary management of children with unilateral multicystic dysplastic kidney remains controversial. With the potential risks of hypertension, infection, and malignant transformation of the dysplastic kidney, conservative management necessitates long-term review with frequent ultrasound scans, urine analyses, and blood pressure checks. Operative management has traditionally used open nephrectomy with its associated patient morbidity. The introduction of laparoscopic procedures has allowed the development of techniques that reduce patient morbidity, hospital stay, and analgesia requirement. This article reports a series of 13 children who underwent elective laparoscopic nephrectomy for unilateral multicystic dysplastic kidney and discusses the advantages this procedure has to offer for their management.

De novo Uroplakin IIIa heterozygous mutations cause human renal adysplasia leading to severe kidney failure

Human renal adysplasia usually occurs sporadically, and bilateral disease is the most common cause of childhood end-stage renal failure, a condition that is lethal without intervention using dialysis or transplantation. De novo heterozygous mutations in Uroplakin IIIa (UPIIIa) are reported in four of 17 children with kidney failure caused by renal adysplasia in the absence of an overt urinary tract obstruction. One girl and one boy in unrelated kindreds had a missense mutation at a CpG dinucleotide in the cytoplasmic domain of UPIIIa (Pro273Leu), both of whom had severe vesicoureteric reflux, and the girl had persistent cloaca; two other patients had de novo mutations in the 3' UTR (963 T-->G; 1003 T-->C), and they had renal adysplasia in the absence of any other anomaly. The mutations were absent in all sets of parents and in siblings, none of whom had radiologic evidence of renal adysplasia, and mutations were absent in two panels of 192 ethnically matched control chromosomes. UPIIIa was expressed in nascent urothelia in ureter and renal pelvis of human embryos, and it is suggested that perturbed urothelial differentiation may generate human kidney malformations, perhaps by altering differentiation of adjacent smooth muscle cells such that the metanephros is exposed to a functional obstruction of urine flow. With advances in renal replacement therapy, children with renal failure, who would otherwise have died, are surviving to adulthood. Therefore, although the mechanisms of action of the UPIIIa mutations have yet to be determined, these findings have important implications regarding genetic counseling of affected individuals who reach reproductive age.

Implication of Wt1 in the pathogenesis of nephrogenic failure in a mouse model of retinoic acid-induced caudal regression syndrome

Renal malformations are common human birth defects that sometimes occur in the context of the caudal regression syndrome. Here, we found that exposure of pregnant mice to all-trans retinoic acid, at a time when the metanephros has yet to form, causes a failure of kidney development along with caudal regression. Maternal treatment with Am580 (retinoic acid receptor alpha agonist) also induced similar patterns of kidney maldevelopment in the fetus. In metanephroi from retinoic acid-treated pregnancies, renal mesenchyme condensed around the ureteric bud but then failed to differentiate into nephrons, instead undergoing involution by fulminant apoptosis to produce a renal agenesis phenotype. Results of whole organ cultures in serum-free medium, and also tissue recombination experiments, showed that the nephrogenic defect was intrinsic to the kidney and that it resided in the metanephric mesenchyme and not the ureteric bud. Renal mesenchyme from control embryos expressed Wilms' tumor 1 (Wt1), but this transcription factor, which is indispensable for kidney development, failed to express in metanephroi of retinoic acid-exposed embryos. Wt1 expression and organogenesis were both restored, however, when metanephroi from retinoic acid-treated pregnancies were grown in serum-containing media. Our data illuminate the pathobiology of a severe, teratogen-induced kidney malformation.

Complementary Role of MRI After Sonography in Assessing Bilateral Urinary Tract Anomalies in the Fetus

OBJECTIVE

The objectives of our study were to evaluate the contribution of adding MRI findings to inconclusive sonographic data when assessing fetal urinary tract anomalies and to determine how this addition may affect the management of pregnancy. SUBJECTS AND METHODS. We prospectively used MRI to study 16 third-trimester fetuses in whom sonography suggested bilateral urinary tract anomalies but failed to provide a definite diagnosis. These anomalies included enlarged hyperechoic kidneys (n = 6), bilateral pelvicaliceal dilatation (n = 6), renal cystic lesions (n = 2), and renal agenesis associated with severe oligohydramnios (n = 2).

RESULTS

The addition of MRI to sonography modified the diagnosis in five fetuses. In a fetus with suspected bilateral ureteropelvic obstruction, the diagnosis of bilateral ureterohydronephrosis associated with reflux or ureterovesical junction obstruction was made. In a fetus with an enlarged bladder at 32 weeks' gestational age, a possible diagnosis of megacystic microcolon was excluded on the basis of the normal appearance of the colon. In two fetuses with enlarged hyperechoic kidneys, MRI showed localized medullary hyperintense lesions suggesting autosomal recessive polycystic kidney disease in one fetus and medullary cystic dysplasia in another fetus with Jeune's syndrome. In a patient with suspected unilateral renal agenesis, MRI showed bilateral agenesis. In four fetuses, the addition of MRI to sonography led to a diagnosis that modified the decision to continue or terminate the pregnancy.

CONCLUSION

MRI can accurately show many urinary tract anomalies in third-trimester fetuses. It may be a useful complementary tool in the assessment of bilateral urinary tract anomalies of fetuses, particularly in cases with inconclusive sonographic findings.