The response of the fetal kidney to obstruction

Deep learning of renal scans in children with antenatal hydronephrosis

INTRODUCTION

Antenatal hydronephrosis (ANH) is one of the most common anomalies identified on prenatal ultrasound, found in up to 4.5% of all pregnancies. Children with ANH are surveilled with repeated renal ultrasound and when there is high suspicion for a ureteropelvic junction obstruction on renal ultrasound, a mercaptuacetyltriglycerine (MAG3) Lasix renal scan is performed to evaluate for obstruction. However, the challenging interpretation of MAG3 renal scans places patients at risk of misdiagnosis.

OBJECTIVE

Our objective was to analyze MAG3 renal scans using machine learning to predict renal complications. We hypothesized that our deep learning model would extract features from MAG3 renal scans that can predict renal complications in children with ANH.

STUDY DESIGN

We performed a case-control study of MAG3 studies drawn from a population of children with ANH concerning for ureteropelvic junction obstruction evaluated at our institution from January 2009 until June of 2021. The outcome was renal complications that occur ≥6 months after an equivocal MAG-3 renal scan. We created two machine learning models: a deep learning model using the radiotracer concentration versus time data from the kidney of interest and a random forest model created using clinical data. The performance of the models was assessed using measures of diagnostic accuracy.

RESULTS

We identified 152 eligible patients with available images of which 62 were cases and 90 were controls. The deep learning model predicted future renal complications with an overall accuracy of 73% (95% confidence inteveral [CI] 68-76%) and an AUC of 0.78 (95% CI 0.7, 0.84). The random forest model had an accuracy of 62% (95% CI 60-66%) and an AUC of 0.67 (95% CI. 0 64, 0.72) DISCUSSION: Our deep learning model predicted patients at high risk of developing renal complications following an equivocal renal scan and discriminate those at low risk with moderately high accuracy (73%). The deep learning model outperformed the clinical model built from clinical features classically used by urologists for surgical decision making.

CONCLUSION

Our models have the potential to influence clinical decision making by providing supplemental analytical data from MAG3 scans that would not otherwise be available to urologists. Future multi-institutional retrospective and prospective trials are needed to validate our model.

Clues for the early loss of renal function in congenital hydronephrosis: Analysis of renal pelvis collagen ratio, diuresis renography and upper urinary tract morphology

INTRODUCTION

Diagnosing real urinary obstruction and surgical decision making for the operative correction of urinary obstruction, are still problematic in congenital hydronephrosis (CH). Compliance of the renal pelvis is one of the important defense mechanisms of renal parenchyma against urinary obstruction. We observed early loss of function in some cases of CH with low and moderate anteroposterior diameter of the renal pelvis (APDRP).

OBJECTIVE

To evaluate structural properties of the renal pelvic tissue of patients with CH and the relation of these structural properties with renal function and Anteroposterior diameter of the renal pelvis.

STUDY DESIGN

Ureteropelvic junction (UPJ) excised during UPJ obstruction operations from 2013 to 2019 were evaluated histopathologically. The patients were divided into the two groups according to initial renal function, i.e. group with initial preoperative differential renal function (DRF) less than 35% and group with initial DRF greater than 35%. The percentage of collagen to whole tissue area were analyzed using image processing program. The relationship between DRF and tissue collagen ratio, SFU and APDRP was evaluated.

RESULTS

There were 5 patients in the DRF <35% group and 16 patients in the DRF >35% group. However, APDRP's of the DRF <35% group were also significantly lower than the DRF >35% group. The collagen distribution in the muscle layer was more prominent in the DRF <35% group. Proportionally, percentage of collagen stained surface was significantly higher in DRF <35% group.

DISCUSSION

There are numerous histopathological studies evaluating the cause of UPJ obstruction. Besides these studies that are oriented to etiology, there are many studies comparing the histopathological changes at UPJ with surgical outcome and prognosis. In the present study, we found that renal pelvis collagen ratio was significantly increased in patients with lower APDRP and with severe renal function loss. This increase in the collagen content in the renal pelvis have been shown to affect the compliance negatively and decrease APDRP, which leads to a faster loss of renal function. Thus, pelvic structural changes accompanying UPJ obstruction may aggravate urinary obstructive process.

CONCLUSION

Increased renal pelvis collagen ratio negatively affects the expansion of the renal pelvis, which is one of the protective mechanisms of the renal parenchyma, and may be one of the triggering mechanisms of early loss of renal function.

Side predilection in congenital anomalies of the kidney, urinary and genital tracts

BACKGROUND

There appear to be various patterns of sidedness with relation to the common urogenital malformations observed in pediatric urology. The objective of this statistical review was to synthesize this data and to assess if these patterns are significant.

MATERIALS AND METHODS

Eighteen urogenital conditions were investigated and for each condition the five largest studies that noted laterality were included. The sidedness of each condition was then analysed for statistical significance.

RESULTS

Three conditions had a statistically significant higher proportion on the right side: palpable undescended testis (63%, p = 0.0002), inguinal hernia (59%, p = 0.0001) and hydrocele (60%, p = 0.003). Three conditions were significantly more common on the left side: impalpable undescended testis (59%, p = 0.0008), renal agenesis (54%, p = 0.02) and vesico-ureteric junction obstruction (71%, p < 0.0001) while both pelvi-ureteric junction obstruction (62%, p = 0.09) and absent vas deferens (61%, p = 0.11) were trending towards significance.

CONCLUSIONS

Various urogenital malformations display a predilection for one side. Proximal malformations tend to be more frequently seen on the left side, where as inguinoscrotal malformations are more frequently observed on the right. There is an increasing body of literature regarding aetiological factors for these conditions. However, our current understanding of the pathophysiology of these conditions does not completely explain this pattern of observation.

Managing Ureteropelvic Junction Obstruction in the Young Infant

In the last decade, management of congenital UPJ obstruction has become progressively observational despite the lack of precise predictors of outcome. While it is clear that many children will have resolution of their hydronephrosis and healthy kidneys, it is equally clear that there are those in whom renal functional development is at risk. Surgical intervention for the young infant, under 6 months, has become relatively infrequent, yet can be necessary and poses unique challenges. This review will address the clinical evaluation of UPJO in the very young infant and approaches to determining in whom surgical intervention may be preferable, as well as surgical considerations for the small infant. There are some clinical scenarios where the need for intervention is readily apparent, such as the solitary kidney or in child with infection. In others, a careful evaluation and discussion with the family must be undertaken to identify the most appropriate course of care. Further, while minimally invasive pyeloplasty has become commonly performed, it is often withheld from those under 6 months. This review will discuss the key elements of that practice and offer a perspective of where minimally invasive pyeloplasty is of value in the small infant. The modern pediatric urologist must be aware of the various possible clinical situations that may be present with UPJO and feel comfortable in their decision-making and surgical care. Simply delaying an intervention until a child is bigger may not always be the best approach.

Management of antenatally detected kidney malformations

Congenital anomalies of the kidneys and the urinary tract (CAKUT) are one of the most common sonographically identified antenatal malformations. Dilatation of the renal pelvis accounts for the majority of cases, but this is usually mild rather than an indicator of obstructive uropathy. Other conditions such as small through large hyperechogenic and/or cystic kidneys present a significant diagnostic dilemma on routine scanning. Accurate diagnosis and prediction of prognosis is often not possible without a positive family history, although maintenance of adequate amniotic fluid is usually a good sign. Both pre- and postnatal genetic screening is possible for multiple known CAKUT genes but less than a fifth of non-syndromic sporadic cases have detectable monogenic mutations with current technology. In utero management options are limited, with little evidence of benefit from shunting of obstructed systems or installation of artificial amniotic fluid. Often outcome hinges on associated cardiac, neurological or other abnormalities, particularly in syndromic cases. Hence, management centres on a careful assessment of all anomalies and planning for postnatal care. Early delivery is rarely indicated since this exposes the baby to the risks of prematurity in addition to their underlying CAKUT. Parents value discussions with a multidisciplinary team including fetal medicine and paediatric nephrology or urology, with neonatologists to plan perinatal care and clinical geneticists for future risks of CAKUT.

Effects of low-dose melamine exposure during pregnancy on maternal and fetal kidneys in rats

Despite the previous reports on melamine contamination in high concentrations some years ago, there were not many studies on low-level exposure in daily life, particularly in pregnancy. We investigated the effect of low-dose melamine on the kidneys of the pregnant rats and their developing embryos/fetuses during various gestational stages namely implantation, gastrulation, organogenesis, maturation and whole pregnancy. Our results showed that the repeated low level of melamine (12.5, 25, and 50 mg/kg bw/d) during pregnancy did not cause obstruction of renal tubules although more precipitating crystals were found in the early gestational periods. Simple hyperplasia in the maternal tubules and pelvic epithelium were more prominent after exposed to melamine during the whole gestational period. Neonatal kidneys significantly suffered more from congestion in glomeruli and interstitium, dilated tubules and interstitial edema after melamine administration to the mother in the late and the whole gestational periods. A trend of advance of glomerular development in fetuses was also observed. We conclude that in utero exposure of low-level melamine could post a risk on the kidneys of the pregnant mother as well as the developing fetuses, which may further increase the possibility of other health problems later in life.

Current applications of in utero intervention for lower urinary tract obstruction

PURPOSE

Since the early 1980s with the inception of fetal intervention for obstructive uropathy, there have been creative attempts to improve both perinatal and long-term outcomes. Despite advances in technology and an improved understanding of lower urinary tract obstruction (LUTO) in the fetus, the results for these therapeutic interventions remain guarded and the long-term renal morbidity among survivors remains problematic.

RECENT FINDINGS

Fetal LUTO represents a range of disorders but the most common of these is posterior urethral valves (PUVs). Selection criteria for candidates of possible intervention have improved with our understanding of fetal renal physiology. Serial urinalysis has marginally improved our ability to predict those that may ultimately respond to treatment [1,2], but the potential in the development of biomarkers for renal development or maldevelopment holds greater promise [3]. Advancements in fetal surgery may result in less fetal and maternal morbidity, but limited long-term improvement in outcomes highlights the controversial nature of the various interventions [4-10]. We must counsel families that fetal surgery offers hope but we cannot allow them to hold unrealistic expectations for cure.

SUMMARY

In appropriately selected fetuses, intervention may improve perinatal survival but not without risk to mother and fetus. Long-term renal outcomes remain problematic amongst survivors. In the case of PUV, postnatal primary valve ablation remains the cornerstone of treatment for nephron preservation; however, our ability to mimic these results in the prenatal population remains poor [11]. Disease severity has likely predetermined those that will survive through the perinatal period with or without intervention. Nonetheless, our drive to assess and manage fetal obstructive uropathy perseveres so that we may ultimately relieve obstruction and preserve renal and lung function. We must maintain optimism that continued advances will ultimately improve outcomes, but also be realistic with our current expectations. This paper reviews the status of current in utero interventions and outcomes.

A fetal sheep model for studying compensatory mechanisms in the healthy contralateral kidney after unilateral ureteral obstruction

INTRODUCTION

Fetal unilateral ureteral obstruction (UUO) triggers complex pathophysiology involving not only the affected organ but also the contralateral kidney, which undergoes evident compensatory changes.

OBJECTIVE

We hypothesized that it would be possible to characterize a transcriptomic fingerprint and selected molecular mechanisms for compensatory growth of contralateral kidneys in UUO, specifically focusing on mediators, carriers, membrane transport, and organ crosstalk in an ovine fetal UUO model.

STUDY DESIGN

A fetal ovine model of complete UUO was created on the 60th day of gestation. For transcriptomics profiling, total RNA was extracted from vital renal biopsies of contralateral (non-obstructed) kidneys harvested on the 80th day of gestation, and kidneys of untreated fetuses served as controls. Statistical analysis provided the set of differentially regulated genes further forwarded to bioinformatics analysis for identification of eventual compensatory molecular mechanisms. Histological analysis was performed with hematoxylin and eosin and periodic acid-Schiff stains.

RESULTS

Contralateral kidneys showed compensatory hypertrophic renal growth, represented on the molecular side by 324 protein coding genes differentially regulated compared with the control kidney samples. Bioinformatics analysis identified an interactome (Figure) consisting of 102 genes with 108 interactions mainly involving transporters (protein transport and protein localization as well as in protein degradation), signaling molecules, DNA/nucleotide/RNA processing, and components of catabolism and cell cycle regulation. Within the interactome, nine receptors were identified as differentially regulated on the contralateral kidney, involving potential renoprotective ligands of the prostaglandin and the bradykinin receptor, arginine vasopressin receptor 1B, and integrin beta 4. Interestingly, a broad range of molecules found differentially expressed, has been previously described in stress response, renoprotection and repair (e.g., MAPK3, MCP1, DICER1, and others).

DISCUSSION

The compensatory renal growth interactome provides a network of transcripts significantly altered in the contralateral kidney, potentially allowing novel insights into mechanisms, interactions, and signaling pathways associated with compensatory growth, and renal protection and repair. Interestingly, the finding of an embedded gene signature reflecting signaling and communication suggests a key role of these processes in CRG either by crosstalk, soluble substances, carriers, or membrane signaling.

CONCLUSIONS

Using a transcriptomics approach, it was possible to identify a gene expression fingerprint of contralateral renal growth in a fetal UUO model. Further studies are warranted to validate those processes and to allow incorporation of this knowledge in new fetal diagnostic or even therapeutic strategies.

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.

Effect of ipsilateral ureteric obstruction on contralateral kidney and role of renin angiotensin system blockade on renal recovery in experimentally induced unilateral ureteric obstruction

Aims:

To study, the effects of ipsilateral ureteric obstruction on contralateral kidney and the role of renin angiotensin system (RAS) blockade on renal recovery in experimentally induced unilateral ureteric obstruction.

Materials and Methods:

Unilateral upper ureteric obstruction was created in 96 adult Wistar rats that were reversed after pre-determined intervals. Losartan and Enalapril were given to different subgroups of rats following relief of obstruction.

Results:

The severity of dilatation on the contralateral kidney varied with duration of ipsilateral obstruction longer the duration more severe the dilatation. There is direct correlation between renal parenchymal damage, pelvi-ureteric junction (PUJ) fibrosis, inflammation and severity of pelvi-calyceal system dilatation of contralateral kidney with duration of ipsilateral PUJ obstruction.

Conclusions:

Considerable injury is also inflicted to the contralateral normal kidney while ipsilateral kidney remains obstructed. Use of RAS blocking drugs has been found to significantly improve renal recovery on the contralateral kidney. It can, thus, be postulated that contralateral renal parenchymal injury was mediated through activation of RAS.

Congenital urinary tract obstruction: defining markers of developmental kidney injury

Congenital urinary tract obstruction (diagnosed antenatally by ultrasound screening) is one of the main causes of end-stage kidney disease in children. The extent of kidney injury in early gestation and the resultant abnormality in kidney development determine fetal outcome and postnatal renal function. Unfortunately, the current approach to diagnostic evaluation of the severity of injury has inherently poor diagnostic and prognostic value because it is based on the assessment of fetal tubular function from fetal urine samples rather than on estimates of the dysplastic changes in the injured developing kidney. To improve the outcome in children with congenital urinary tract obstruction, new biomarkers reflecting these structural changes are needed. Genomic and proteomic techniques that have emerged in the past decade can help identify the key genes and proteins from biological fluids, including amniotic fluid, that might reflect the extent of injury to the developing kidney.

Pediatric hydronephrotic segmental renal dysplasia with ipsilateral ureterovesical obstruction--rare coincidence or a consequence?

Obstruction in the developing urinary tract during embryonic life is one of the factors promoting disordered metanephric development in renal dysplasia. Dysplastic kidneys usually undergo involution during the first 5 years of life. Herein, we narrate a rare case of hydronephrotic segmental dysplasia co-existing with ipsilateral ureterovesical obstruction, in a 7-year-old male child, masquerading as hydronephrosis. Etiopathogenesis of segmental dysplasia presenting at this age is not clearly understood, and could be a consequence of intrauterine obstructive uropathy. Histologic evidence of dysplasia in a hydronephrotic kidney should warrant a close follow-up for pathologic changes in the contralateral kidney or urinary tract.

Posterior urethral valves: renal failure and prenatal treatment

Posterior urethral valves occur in 1 : 5000 live births. Despite the high prevalence, the few children that survive do poorly, with over 50% progressing to ESRD in 10 years. The gold standard for post-natal diagnosis is voiding cystourethrography, while pre-natal diagnosis is dependent on routine screening ultrasonography. Despite the ability to identify features of bladder outlet obstruction early in fetal development, there is no consensus on how to incorporate early detection into current screening protocols. There has yet to be a marker that allows prediction of obstruction in the absence of or prior to radiographic evidence of obstruction. With our current screening strategy, the majority of interventions are performed well after irreversible damage has occurred. Improved mortality and long term morbidity from posterior urethral valves and congenital bladder outlet obstruction will likely remain unchanged until it is possible to intervene prior to the onset of irreversible renal damage. New biologic markers and improved instrumentation will allow for more effective diagnosis and intervention at earlier stages of fetal development.

The optimal dose of Adriamycin to create a viable rat model potentially applicable to congenital obstructive uropathy

PURPOSE

The Adriamycin rat model is an established model for different organ anomalies including congenital obstructive uropathy. In the current study, we carried out a dose-response analysis to find out the optimal dose of Adriamycin to create a viable rat model of obstructive uropathy.

METHODS

Thirty time-mated Sprague-Dawley rats were divided into 5 groups including 1 control group and 4 different treatment groups. The 4 Adriamycin dosage regimens investigated in this study were 1.25, 1.5, 1.75, and 2 mg/(kg d). Experimental rats (n = 24) were injected intraperitoneally with different doses of Adriamycin on gestational days 7 to 9 (6 rats in each group). Control rats (n = 6) were injected with an equivalent volume of saline on the same days. Viable term fetuses were harvested on gestational day 21 by cesarean delivery and dissected under a dissecting microscope. Serial transverse sections from urinary tract system were obtained for histological examination.

RESULTS

One hundred thirty-three viable fetuses were recovered from Adriamycin-treated rats, and 50 were from rats in the control group. There were no resorptions in the control group; however, 52 resorptions were recorded in Adriamycin groups. The rates of hydronephrosis and resorptions were 60% and 0%, 80.5% and 5.8%, 100% and 17.3%, and 100% and 76.9% at doses of 1.25, 1.50, 1.75, and 2 mg/(kg d), respectively. Histologic examination of the kidneys in the treated groups showed a significant decrease in renal parenchyma compared with the control group.

CONCLUSIONS

The dosage of 1.5 mg/(kg d) of Adriamycin yielded the highest number of viable hydronephrotic fetuses. At this dose, urinary abnormalities are milder; but the highest number of viable fetuses is provided, which is necessary to create a reproducible and viable animal model.

Multicystic dysplastic kidney disease presenting with a single large cyst in a fetus-anatomical basis and radiological aspects

Multicystic dysplastic kidney (MCDK) is a congenital maldevelopment in which the renal cortex is characteristically replaced by numerous cysts of multiple sizes. MCDK presenting as a single predominant large cyst in morphology is less common. We report on the prenatal imaging findings and perinatal management of a fetus with MCDK unusually presenting as a single predominant large cyst, erroneously interpreted as a severe fetal hydronephrosis. Details of the perinatal history, radiological evaluation, morphological characteristic, and clinical aspect of this case are presented. We also discuss a few studies addressing the sensitivity of magnetic resonance urography for the prenatal diagnosis of MCDK.

The classification of renal cystic diseases and other congenital malformations of the kidney and urinary tract

CONTEXT

Renal cystic diseases and congenital abnormalities of the kidney and urinary tract comprise a heterogeneous group of lesions whose pathogenesis has eluded physicians for centuries. Recent advances in molecular and genetic understanding of these diseases may provide the solution to this riddle.

OBJECTIVE

The formulation of an effective classification system for these disorders has been elusive but is needed to introduce order while providing a conceptual framework for diagnosis.

DATA SOURCES

This review discusses the evolution, beginning in the 19th century, of postulates regarding the pathogenesis of cystic and developmental renal diseases. Selected classification systems proffered during this period are discussed in pursuit of an ideal classification schema that would account for morphologic features and their clinical importance, with logical links to pathogenesis and treatment. Although this remains an elusive target, its general outline is becoming clearer. A classification approach favored by the author is presented, which incorporates many of the strengths contained in several previous classifications.

CONCLUSIONS

Genetic-and molecular-based postulates regarding the pathogenesis of the renal cystic and developmental diseases have implicated mutated master genes and the modification of genes that are crucial in renal development and genes that are central to the sensory effects of the renal tubular primary cilium on cell physiology. These scientific advances provide pathogenetic links between morphologically and genetically distinct entities and certain cystic and neoplastic entities, associations that seemed implausible not long ago. These advances may eventually provide the basis for future classification systems while suggesting targets for therapeutic approaches in the prevention and treatment of these diseases.

Mechanisms of renal injury and progression of renal disease in congenital obstructive nephropathy

Congenital obstructive nephropathy accounts for the greatest fraction of chronic kidney disease in children. Genetic and nongenetic factors responsible for the lesions are largely unidentified, and attention has been focused on minimizing obstructive renal injury and optimizing long-term outcomes. The cellular and molecular events responsible for obstructive injury to the developing kidney have been elucidated from animal models. These have revealed nephron loss through cellular phenotypic transition and cell death, leading to the formation of atubular glomeruli and tubular atrophy. Altered renal expression of growth factors and cytokines, including angiotensin, transforming growth factor-beta, and adhesion molecules, modulate cell death by apoptosis or phenotypic transition of glomerular, tubular, and vascular cells. Mediators of cellular injury include hypoxia, ischemia, and reactive oxygen species, while fibroblasts undergo myofibroblast transformation with increased deposition of extracellular matrix. Progression of the lesions involves interstitial inflammation and interstitial fibrosis, both of which impair growth of the obstructed kidney and result in compensatory growth of the contralateral kidney. The long-term outcome depends on timing and severity of the obstruction and its relief, minimizing ongoing injury, and enhancing remodeling. Advances will depend on new biomarkers to evaluate the severity of obstruction, to determine therapy, and to follow the evolution of lesions.

CONGENITAL URINARY BLADDER OUTLET OBSTRUCTION

The term congenital ‘bladder outlet obstruction (BOO)’ describes the collection of conditions in which the normal, urethral egress of urine from the fetal bladder is impaired. The term is interchangeable with fetal ‘lower urinary tract obstruction’, as used by other authors. After considering normal urinary tract embryology, we describe the epidemiology of congenital BOO and the primary anatomical disorders associated with it. We then proceed to describe its fetal and postnatal clinical manifestations and then consider therapies and interventions which have been used to manage the condition. We not only focus on urethral and bladder disease with constitutes BOO itself, but also describe associated kidney disorders which, via chronic renal excretory failure, are important causes of morbidity. Rather than provide an exhaustive review, we emphasise studies published in the last decade, and therefore readers are referred to other reviews citing numerous earlier references.

Laparoscopic removal of a pelvic cyst associated with obstructed megaureter and dysplastic renal remnant

We report a case of a 41-year-old man with a solitary functioning left kidney and history of chronic pelvic discomfort associated with lower urinary tract symptoms. Imaging revealed a large cystic structure in the pelvis attached to a dilated tortuous ureter on the right with congenital absence of the right kidney. The patient underwent laparoscopic removal of the pelvic cyst and dilated right ureter. Pathological assessment revealed mesonephric remnants representing dysplastic renal tissue attached to a dilated and obstructed megaureter, extending into the bladder wall and forming a large pelvic cyst. The patient's symptoms resolved. A laparoscopic approach represents an excellent surgical option for pelvic pathology.

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.

Magnetic resonance urography in children

Magnetic resonance (MR) urography is a powerful tool that fuses anatomic information with functional data in a single test without the use of ionizing radiation. This article provides an overview of the technical aspects of MR urography and common clinical applications, such as the evaluation of hydronephrosis, reflux nephropathy, and renal dysplasia.

Investigation of histopathologic changes in the ureter walls in experimental congenital obstructive uropathy

BACKGROUND/PURPOSE

The aim of this study is to determine the histopathologic changes in the ureter wall in experimental urinary bladder hypoplasia and agenesis.

METHODS

Timed pregnant rats were randomly divided and received intraperitoneal Adriamycin (ADR) at 2 mg/kg on gestational days (GD) 6 to 9 (ADR group) and saline at 2 mL/kg on GD 6 to 9 (SF group). The control (C) group did not receive any medication in their pregnancy. Fetuses were harvested near term on GD 21 and dissected under a dissecting microscope and examined for urinary system abnormalities.

RESULTS

Diameter of ureter lumen was significantly increased, but wall thickness, tunica muscularis, and epithelial thickness of the ureter were decreased in the ADR group as compared with the C and SF groups.

CONCLUSIONS

Diameter of the ureter lumen was increased, but wall thickness, tunica muscularis, and uroepithelium of the ureter were decreased in the ADR group in the intrauterine period. The diameter of the ureter lumen and wall thickness of ureter (tunica muscularis of ureter and uroepithelium) were increased following obstructive uropathy after the birth.

Upper urinary tract dilatation: prenatal diagnosis, management and outcome

Upper urinary tract dilatation is one of the most common abnormalities detected on prenatal ultrasound scanning. It is commonly due to transient urine flow impairment (UFI) at the level of the pelvi-ureteric and vesico-ureteric junctions, which improves with time in most cases. It is usually in the neonatal period that the diagnosis is confirmed and during the first 18 months of life that the prognosis of the dilatation is defined.

Vesicoureteral reflux

Vesicoureteral reflux (VUR), the retrograde flow of urine from the bladder toward the kidney, is common in young children. About 30% of children with urinary tract infections will be diagnosed with VUR after a voiding cystourethrogram. For most, VUR will resolve spontaneously; 20% to 30% will have further infections, but few will experience long-term renal sequelae. Developmentally, VUR arises from disruption of complex signaling pathways and cellular differentiation. These mechanisms are probably genetically programmed but may be influenced by environmental exposures. Phenotypic expression of VUR is variable, ranging from asymptomatic forms to severe renal parenchymal disease and end-stage disease. VUR is often familial but is genetically heterogeneous with variability in mode of inheritance and in which gene, or the number of genes, that are involved. Numerous genetic studies that explore associations with VUR are available. The relative utility of these for understanding the genetics of VUR is often limited because of small sample size, poor methodology, and a diverse spectrum of patients. Much, if not all, of the renal parenchymal damage associated with end-stage disease is likely to be congenital, which limits the opportunity for intervention to familial cases where risk prediction may be available. Management of children with VUR remains controversial because there is no strong supportive evidence that prophylactic antibiotics or surgical intervention improve outcomes. Furthermore, well-designed genetic epidemiological studies focusing on the severe end of the VUR phenotype may help define the causal pathway and identify modifiable or disease predictive factors.

Congenital urinary tract obstruction

Congenital urinary tract obstruction is a heterogenous condition with a varying natural history. Accurate diagnosis within the late-first and second trimesters allows for counselling of the parents and planning of multi-disciplinary care for the pregnancy and newborn. Antenatal investigations to predict postnatal renal function are of varying accuracy. However, some factors have been shown to be predictive of poor outcome in terms of renal function at birth and infancy. There is the possibility of in-utero intervention in these fetuses.

Evaluation of reflux nephropathy, pyelonephritis and renal dysplasia

MR urography has the potential to significantly improve our understanding of the relationship between reflux nephropathy, pyelonephritis, vesicoureteric reflux and renal dysplasia. MR urography utilizes multiple parameters to assess both renal anatomy and function and provides a more complete characterization of acquired and congenital disease. Pyelonephritis and renal scarring can be distinguished by assessing the parenchymal contours and signal intensity. Characteristic imaging features of renal dysplasia include small size, subcortical cysts, disorganized architecture, decreased and patchy contrast enhancement as well as a dysmorphic pelvicalyceal system. Because of its ability to subdivide and categorize this heterogeneous group of disorders, it seems inevitable that MR urography will replace DMSA renal scintigraphy as the gold standard for assessment of pyelonephritis and renal scarring. MR urography will contribute to our understanding of renal dysplasia and its relationship to reflux nephropathy.

Renal dysplasia and MRI: a clinician's perspective

Renal dysplasia is a common abnormality in children. The role of MRI in evaluating children with renal dysplasia is evolving. More information is clearly necessary before MRI replaces conventional imaging modalities. In order to appropriately use MRI, the radiologist must have an understanding of the clinical questions that are important in the management of children with renal dysplasia. This review provides background information on renal dysplasia for the pediatric radiologist. The focus is on unilateral disease, especially multicystic dysplastic kidneys, and bilateral dysplasia, which is the most common cause of kidney failure in children. The emphasis is on the important clinical issues, and the potential of MRI as a methodology for providing clinically useful information not otherwise available from other imaging modalities.

Fetal Sheep Development on Ultrasound and Magnetic Resonance Imaging: A Standard for the in utero Assessment of Models of Congenital Abnormalities

OBJECTIVE

To establish normative data for the size, conspicuity, and imaging characteristics of normal developing fetal sheep organs on ultrasound (US) and magnetic resonance (MR) imaging.

METHODS

US and MR images of ten normal pregnant sheep, at 40, 65, 90, 115, and 140 gestational days (term = 145 days), were scored for organ conspicuity and imaging characteristics. Imaging biometry was correlated with specimens. Gestational age-based growth parameters were modeled using regression.

RESULTS

Imaging biometry showed excellent correlation with specimens. Kidney, bladder, stomach, lung, liver, and spine were seen well from 65 days to term by US. More organs were consistently visible from 90 days to term by MR than by US. Most organ imaging characteristics tended not to change throughout gestation.

CONCLUSION

Normal fetal sheep biometry, organ conspicuity, and imaging characteristics are established for US and MR and have potential use for the in utero assessment of sheep models of congenital abnormalities.

Experimental short-term fetal bladder outflow obstruction: I. Morphology and cell biology associated with urinary flow impairment

PURPOSE

In fetal sheep, combined urethral and urachal obstruction initiated at 75 days' gestation and maintained for 30 days led to dysmorphic bladders, similar to those found in humans with prune belly syndrome, and uniformly disrupted kidney development. We aimed to create a less severe model of fetal bladder outlet obstruction, more closely resembling infants with posterior urethral valves, and additionally to further our understanding on the role of the urachus. We hypothesized that milder morphological renal tract changes would occur after shorter term experimental obstruction.

MATERIALS AND METHODS

Male fetal lambs were assigned to urachal and urethral ligation, urachal ligation only or sham operations. Analyses were performed after 9 days.

RESULTS

Concurrent urachal and urethral obstruction resulted in increased bladder weight, and protein and DNA content. Detrusor smooth muscle was well maintained, as assessed by light and electron microscopy, although urothelia showed basal apoptosis. Bladder obstruction led to hydronephrosis but failed to produce significant perturbations in urine osmolality. The nephrogenic cortex was either well preserved or was replaced by glomerular cysts; the latter group tended to have heavier bladders. Urachal obstruction alone produced similar changes suggesting that the male sheep fetal urethra is a high-resistance conduit in mid-gestation.

CONCLUSIONS

Concurrent urachal and urethral obstruction, or urachal obstruction alone, initiated in mid-gestation and maintained for 9 days leads to bladder overgrowth but preserved renal tubular function. In future, it will be interesting to determine whether bladder decompression around this stage leads to reversal of bladder overgrowth and/or ameliorates severe renal tract damage described after longer term fetal bladder outflow obstruction.

Timing of morphologic and apoptotic changes in the sheep fetal kidney in response to bladder outflow obstruction

PURPOSE

Posterior urethral valves are the main cause of bladder outflow obstruction in human fetuses. Thirty per cent of boys with valves develop end-stage renal disease, despite intervention in the postnatal period. The timing and mechanisms of renal damage in bladder outflow obstruction are unknown. We investigated the timing of changes in morphology and apoptosis in the fetal sheep kidney in response to obstruction.

MATERIALS AND METHODS

Thirty-three fetal lambs at day 70 of gestation underwent surgical creation of bladder outflow obstruction. Twenty-nine fetal lambs had sham surgery. Fetal kidneys were collected 2, 5, 10, 20 and 30 days after surgery. Renal histology was examined. Real-time PCR was used to quantify the renal cortical expression of the pro-apoptotic gene Bax and anti-apoptotic gene Bcl-X. The TUNEL technique was used to assess regional renal apoptosis in response to obstruction.

RESULTS

Changes in renal morphology were evident as early as 2 days after surgery in fetuses with bladder outflow obstruction, and progressed over 20-30 days to cystic renal dysplasia. Bladder outflow obstruction increased the renal cortical expression of Bax relative to Bcl-X. Tubular apoptosis peaked after 2 days of obstruction. Blastemal apoptosis peaked after 5 days of obstruction.

CONCLUSIONS

Changes in pro- and anti-apoptotic gene expression in the fetal renal cortex, and alterations in the number of apoptotic cells and renal morphology are evident soon after the onset of bladder outflow obstruction. These findings suggest that damage to the developing fetal kidney begins to occur at the onset of obstruction. Attempts to preserve renal function by antenatal interventions may best be achieved by early treatment.

Complete unilateral ureteral obstruction in the fetal lamb. Part I: long-term outcomes of renal hemodynamics and anatomy

PURPOSE

We evaluated the long-term consequences of complete fetal UUO on renal hemodynamics and anatomy.

MATERIALS AND METHODS

A total of 26 fetal lambs underwent surgical UUO at 90 days of gestation and 14 twin matched animals served as controls. Synchronous bilateral ARBF was measured using mean transit time technology. Standard anatomical analysis, including evaluation of RPV, was performed in the kidneys. Measurements were done 10, 20 and 40 days following UUO in groups 1 to 3, respectively and in 1-month-old lambs in group 4.

RESULTS

All obstructed kidneys underwent typical hydronephrotic transformations with a progressive decrease in parenchymal volume compared to that of contralateral and control kidneys. ARBF in obstructed kidneys was significantly decreased compared to their contralateral counterparts in all groups (p <0.01). Comparing ARBF to RPV showed that the decrease in ARBF was proportional to the loss of parenchymal volume in fetal obstructed kidneys but it remained significant in lambs (p <0.05).

CONCLUSIONS

Complete UUO alters ARBF, while vascularization of the remaining renal parenchyma is maintained in fetuses. Profound impairment of the renal arterial supply observed in lambs may be due to physiological changes linked to birth.

Complete Unilateral Ureteral Obstruction in the Fetal Lamb. Part II: Long-Term Outcomes of Renal Tissue Development

PURPOSE

We analyzed the dynamics of the renal tissue response to experimental fetal urinary flow impairment concerning renal morphology, extracellular matrix composition, regulators of connective tissue degradation and PAX2 protein expression.

MATERIALS AND METHODS

A total of 26 fetal lambs underwent surgical unilateral ureteral obstruction at 90 days of gestation and 14 twin matched animals served as controls. Kidneys were harvested 10, 20 and 40 days after the prior procedure in groups 1 to 3, respectively and in 1-month-old lambs (group 4). Morphological analysis was done using light microscopy. Picrosirius red staining was used to evaluate the area occupied by extracellular matrix components. Collagen I, III and IV, alpha-smooth muscle actin, MMP-1, 2 and 9, TIMP-1 and 2 and PAX2 protein were assessed using immunochemistry.

RESULTS

All obstructed kidneys were hydronephrotic without dysplasia. Hypoplasia resulting from a decreased NGG was observed. The inflammatory response to obstruction was poor in fetal obstructed kidneys. From 10 days after obstruction interstitial fibrosis was noted and confirmed by an increase in picrosirius red staining. In obstructed kidneys immunochemistry showed an increase in collagen deposition beginning from the papillae and extending through the whole parenchyma. Aberrant interstitial collagen IV deposition was observed. The increase in alpha-smooth muscle actin staining was mainly localized in the blastema and interstitial cells in obstructed kidneys. MMP and TIMP immunostaining was mainly present in tubules throughout the whole nephrogenic period and persisted in mature kidneys. Beginning from 20 days after obstruction a progressive increase in MMP and TIMP expression was noted. This was associated with ectopic expression in the medullary tubules. PAX2 protein was highly expressed in the nephrogenic zone, decreasing progressively to being markedly decreased in control lamb kidneys. No difference was found in PAX2 expression during the fetal period when comparing unobstructed and obstructed kidneys, it but remained strongly expressed in the dilated collecting ducts of obstructed lambs.

CONCLUSIONS

Complete unilateral ureteral obstruction performed in fetal lambs at 90 days of gestation led to pure hydronephrotic transformation, hypoplasia and a marked increase in connective tissue deposition. Inflammatory infiltrates and PAX2 dysregulation were not seen as having a decisive role in these modifications.

Supranormal renal function in unilateral hydronephrosis: does it represent true hyperfunction?

The existence of supranormal differential renal function in unilateral hydronephrosis remains controversial. While some authors consider it as fact, others believe that it is just a technical artifact. Within our department, chromium-51 ethylene diamine tetra-acetic acid (Cr-EDTA) renal clearance is systematically performed in conjunction with technetium-99m mercaptoacetyltriglycine (MAG3) renograms to derive an absolute single kidney glomerular filtration rate (SKGFR). Our data allows us to ascertain whether supranormal differential renal function in unilateral hydronephrosis might be due to hypofunction of the contralateral kidney. Children with marked unilateral hydronephrosis were selected from a large database of MAG3 diuretic(s) renograms. We excluded patients with posterior urethral valves, duplex anomalies, neurogenic bladder, solitary kidney, and those who underwent any previous urological surgery. We also excluded children who had an early furosemide injection (F0 procedure), selecting only those having received furosemide at the end of the renogram (F+20 test). Seventy-three patients (92 renograms) fulfilled these criteria. Differential renal function was calculated using the integral method. Hydronephrotic kidney with a relative uptake > or =55% was defined as supranormal. Six renograms (four patients) demonstrated supranormal relative function on the hydronephrotic side. However, the SKGFR of these kidneys was in all cases within the range of normal values, while the contralateral side demonstrated borderline low SKGFR. Increased relative function on the side of the hydronephrotic kidney is relatively infrequent. When it occurs, it may be related to a borderline hypofunction of the contralateral kidney.

Gene locus ambiguity in posterior urethral valves/prune-belly syndrome

Lower urinary tract obstruction by posterior urethral valves (PUV) is an important cause of congenital renal failure in male infants. Though population-based studies point to a role of genetic factors in the etiology of PUV, no clear evidence for a specific gene defect for PUV has been observed so far. Here we present a consanguineous family with four male descendants affected by PUV and a healthy girl, suggestive of autosomal recessive inheritance. One boy presented with prune-belly syndrome (PBS) in addition to PUV. Using a DNA chip-based genome-wide linkage analysis, we identified a region of homozygosity for the affected boys in an interval of 35 cM on chromosome 1q41-44 with a maximum multipoint LOD score of Z(max) = 3.134 at theta = 0 for single nucleotide polymorphisms (SNPs) rs158724-rs720163. By applying a second genetic model based on the assumption of a male-limited phenotype and the girl being carrier of the genetic defect without expressing the phenotype, a second alternative locus of 9 cM on chromosome 11p11 was identified with a LOD score of Z(max) = 3.61 at theta = 0. Equal significance for both loci with a LOD score of Z(max) = 3.01 at theta = 0 was obtained after the affection status of the female descendant was set "unknown". We suppose that most probably, only one of the two identified loci harbours the disease-causing gene. As the interpretation of the girl's status remains uncertain, we are not able to exclude one of the two loci. Analyses of additional informative families will be important to exclude one of the two loci and to restrict the critical interval.

Outcome of fetal renal pelvic dilatation diagnosed during the third trimester

OBJECTIVES

The aim of this study was to evaluate renal function and the need for postnatal treatment--antibiotic therapy and/or surgery--in relation to the grade of fetal renal pelvic dilatation (RPD) found on third-trimester ultrasound examination.

METHODS

The retrospective study included 78 children, born between 1995 and 2000, with 115 dilated fetal renal pelvic units. The children were allocated to three groups based on pelvic anteroposterior diameter (APD) detected on third-trimester ultrasound: APDs of 7-9.9 mm, 10-14.9 mm and > or = 15 mm were classified as mild dilatation, moderate hydronephrosis and severe hydronephrosis, respectively. Renal function was assessed by scintigraphy.

RESULTS

None of the 20 children with mild dilatation experienced a urinary tract infection (UTI) or underwent surgery; two had associated renal or urinary tract abnormalities. In contrast, five out of 22 (23%) children with moderate hydronephrosis and 23 out of 36 (64%) with severe hydronephrosis had either a UTI or required surgery (P < 0.001); associated abnormalities were also more common (6 out of 22 and 15 out of 36, respectively). There was no significant correlation between the grade of antenatal RPD and postnatal ipsilateral renal function.

CONCLUSIONS

The need for postnatal treatment increased significantly with the grade of antenatal RPD. Children with antenatal mild dilatation were discharged early from follow-up whereas those with moderate and severe fetal hydronephrosis needed close follow-up by a multidisciplinary team.

Concomitant anomalies in 100 children with unilateral multicystic kidney

OBJECTIVES

To determine the incidence and type of associated urogenital anomalies in children with a unilateral multicystic kidney and to assess in children with nephrectomy the additional diagnostic value of cystoscopy and, in girls, of colposcopy.

METHODS

This was a follow-up study of 100 fetuses with antenatally detected unilateral multicystic kidneys. After ultrasound confirmation of the diagnosis within a few days after birth voiding cystourethrography and isotope scan were performed in 83 of the surviving children to exclude vesicoureteral reflux and to establish renal function. Eighty-one children underwent nephrectomy and, prior to surgery, all underwent cystoscopy and girls also underwent colposcopy.

RESULTS

Seventy-five children had one or more additional urogenital anomalies: 39 had anomalies of the contralateral kidney, 40 had anomalies of the ipsilateral kidney and 30 had one or more anomalies of the lower urogenital tract. With cystoscopy 54 anomalies of the genitourinary tract were detected in 48 children and with colposcopy three anomalies were detected in 35 girls. Eighty-one children had a nephrectomy or heminephrectomy and 33 of them needed other urological intervention. Thirteen fetuses died (mostly from agenesis of the contralateral kidney) and six infants had no surgery at all.

CONCLUSION

Children with a unilateral multicystic kidney are at considerable risk of having other urogenital anomalies. When cystoscopy and colposcopy are added to routine investigations the rate of detection of anomalies is 75%, twice that reported in the literature.

Ontogeny of the VATER kidney in a rat model

By exposing rat fetuses to adriamycin prenatally, a rat model of VATER association has been created. Absence of the fetal bladder is prominent and the kidneys show features of chronic obstruction with hydronephrosis/hydroureter, loss of parenchyma, fewer glomeruli, and less differentiation. The aim of this study was to elucidate this rat model, to determine exactly when the changes in the kidneys develop, hopefully thereby to expand our understanding of congenital obstructive uropathy. Timed-pregnant Sprague-Dawley rats were injected intraperitoneally with adriamycin on days 6-9 of gestation. The control group received saline. Fetuses were recovered on gestational days (GDs) 20, 19, 18, 17, 16, 15, 14, 12, and 10 (total, 120 control, 121 treated). Macroscopic features were determined. Serial sections were then taken and stained with hematoxylin and eosin. Comparisons were made under light microscopy. The metanephric kidney first became apparent at GD12. The development of the control and treated kidneys appeared similar till GD18. Beyond this day, the treated kidneys exhibited increasing degrees of distension of Bowman's capsule, ducts, and subsequently pelvis and ureter. There were fewer levels of glomeruli, which were also less differentiated. Less differentiation was also noted in the medulla, and with time this became thin in comparison to the control kidneys. By GD20, the renal pelvis was grossly dilated with a blunted papilla, and the renal parenchyma was thin. Prenatal exposure of rat fetuses to adriamycin results in kidneys that are chronically obstructed, as the majority of the fetuses show absence of the bladder. Absence of renal dysmorphology until GD18, when urine is first produced, suggests strongly that the effect of adriamycin on the kidney is indirect, via agenesis of the bladder and secondary to backpressure from early urine production. This is a unique, simple, and reliable model of fetal obstructive uropathy and will be very useful to facilitate further investigation into its pathophysiology and to explore new treatment options.

Angiotensin-converting enzyme and angiotensin type 2 receptor gene genotype distributions in Italian children with congenital uropathies

Angiotensin I-converting enzyme (ACE) and angiotensin type 2 receptor (AT2R) gene polymorphisms have been associated with an increased incidence of congenital anomalies of the kidney and urinary tract (CAKUT). We investigated the genotype distribution of these polymorphisms in Italian children with CAKUT. We also evaluated the association between the ACE insertion/deletion and the AT2R gene polymorphisms with the progression of renal damage in subgroups of CAKUT patients. We recruited 102 Italian children with CAKUT; 27 with vesicoureteral reflux; 12 with hypoplastic kidneys; 20 with multicystic dysplastic kidneys; 13 with ureteropelvic junctions stenosis/atresia; 18 with nonobstructed, nonrefluxing primary megaureters; and 12 with posterior urethral valves and compared them with 92 healthy control subjects. ACE and AT2R gene polymorphisms were analyzed by PCR. The identification of AT2R gene polymorphisms in intron 1 and in exon 3 was revealed by enzymatic digestion. ACE genotype distribution in children with CAKUT was no different from that of the control subjects, but the subgroup of patients with radiographic renal parenchymal abnormalities showed an increased occurrence of the D/D genotype. The frequency of the G allele of AT2R gene in children with CAKUT was increased in respect to that of the control subjects. By contrast, no significant difference in the frequency of the C and A alleles of the AT2R gene was found. Our findings indicate that the ACE gene can be a risk factor in the progression of renal parenchymal damage in CAKUT patients. Moreover, a major role of the AT2R gene in the development of CAKUT has been found, at least in Italian children.

Increased nephron volume is not a cause of supranormal renographic differential renal function in patients with ureteropelvic junction obstruction

PURPOSE

Increasing clinical importance is being placed on the role of differential renal function (DRF) in the management of congenital ureteropelvic junction obstruction. Supranormal DRF of the hydronephrotic kidney on renal scan is a puzzling phenomenon and is hypothesized to be due to an increase in single nephron filtration or nephron volume without sound evidence. We studied the histopathological changes of hydronephrotic kidneys to determine whether glomerular hypertrophy underlies supranormal DRF.

MATERIALS AND METHODS

We retrospectively evaluated the records of 3 females and 32 males with unilateral congenital hydronephrosis who underwent pyeloplasty. Mean patient age at operation was 12.6 months (range 0.1 to 144). Needle biopsies from 3 different sites at the lower pole of the kidney were performed during surgery. To evaluate the presence of glomerular hypertrophy, the maximal planar area of glomeruli was measured under light microscopy using an image analyzer. Tissue samples obtained from kidneys without a history of urinary tract disease at autopsy were used as controls. The mean glomerular areas of the patient and control groups were evaluated according to DRF and age.

RESULTS

The mean glomerular area values of the patient group were smaller than those of the control group, except for 4 patients. The glomerular areas of the hydronephrotic kidneys with supranormal DRF were not significantly different from those of the control group. Instead, the probability of larger renal glomeruli increased with decreasing DRF (p = 0.1155).

CONCLUSIONS

Increased nephron volume can be discounted as a cause of supranormal DRF.

Ontogeny of congenital anomalies of the kidney and urinary tract, CAKUT

Ectopic budding of the initial ureter from the Wolffian duct is the first ontogenic misstep that leads to many congenital anomalies of the kidney and urinary tract (CAKUT). The ectopia results in hypoplastic kidney, ectopia of ureterovesical orifice, urinary outflow obstruction and/or reflux. Recent studies on several mutant mouse models verified that ectopic ureteric budding indeed occurs prior to the formation of CAKUT. Often, the genes involved in navigating the site of ureteric budding also regulate later ontogenic processes of the kidney and other urinary tract systems. These additional functions of the genes underlie the wide spectrum of CAKUT, for example multicystic dysplastic kidney, megaureter and atretic ureter, because the genes regulate the morphogenesis of the many portions of the excretory system through their distinctive cellular functions.

Urinary outflow obstruction increases apoptosis and deregulates Bcl-2 and Bax expression in the fetal ovine bladder

During organogenesis, net growth of tissues is determined by a balance between proliferation, hypertrophy, and apoptotic death. Human fetal bladder outflow obstruction is a major cause of end-stage renal failure in children and is associated with complex pathology in the kidney and lower urinary tract. Experimental manipulation of the fetal sheep urinary tract has proved informative in understanding the pathobiology of congenital obstructive uropathy. In this study we used an ovine model of fetal bladder outflow obstruction to examine effects on apoptotic cell death in the developing urinary bladder. While 30 days of obstruction in utero between 75 and 105 days gestation resulted in overall growth of the fetal bladder as assessed by weight, protein, and DNA measurements, we found that apoptosis, as assessed by in situ end-labeling, was up-regulated in fetal bladder detrusor muscle and lamina propria cells and that this was accompanied by a down-regulation of the anti-death protein Bcl-2 and an up-regulation of the pro-death protein Bax. Moreover, activated caspase-3, an effector of apoptotic death, was increased in obstructed bladders. This is the first study to define altered death in an experimental fetal model of bladder dysmorphogenesis. We speculate that enhanced apoptosis in detrusor smooth muscle cells is part of a remodeling response during compensatory hyperplasia and hypertrophy. Conversely, in the lamina propria, an imbalance between death and proliferation leads to a relative depletion of cells.

Poor predictability of prenatal ultrasonography for a nonfunctional kidney

We present 2 cases in which the diagnosis of a unilateral nonfunctioning kidney was not anticipated. The first case appeared to be simple, antenatally diagnosed, unilateral hydronephrosis with adequate parenchyma. However, at 3 months postnatally, it was found to be nonfunctional, most likely secondary to early high-grade obstruction. The second case presented prenatally as a left hydronephrotic kidney with parenchymal cysts, and the right kidney showed only mild parenchymal cystic changes. By 6 months, however, the right kidney was nonfunctional. These cases emphasize the need for coordinated prenatal and postnatal care. The sonographic appearance of renal dysplasia is variable (in size, number of cysts, and degree of hydronephrosis), depending on the point at which it is evaluated during the disease course. Subtle signs of dysplasia, such as increased echogenicity, may be the only warning sign of a nonfunctioning kidney, for which one should have a high index of suspicion.

Recovery from release of ureteral obstruction in the rat: relationship to nephrogenesis

BACKGROUND

Obstructive nephropathy is a major cause of renal insufficiency in infants and children. Despite release of unilateral ureteral obstruction (UUO) in the first five days of life in the rat, renal growth is impaired, while glomerular filtration rate (GFR) is preserved at one month, but decreases markedly by one year. To test the hypothesis that renal recovery from UUO depends on the stage of nephrogenesis at the time of relief of obstruction, renal recovery from relief of five days UUO following completion of nephrogenesis (days 14 to 19) was compared with UUO during nephrogenesis (days 1 to 5).

METHODS

Rats underwent UUO or sham operation at one day of age, with relief five days later. In additional groups of neonatal rats, the operation was at 14 days, with relief at 19 days. Three months later, blood pressure, GFR, urine flow, sodium and potassium excretion, and kidney weight were measured. In addition, the number of glomeruli, glomerular maturation, glomerular diameter, tubular atrophy, and interstitial fibrosis were determined in each kidney. The effects of five-day UUO on number of glomeruli was determined also in adult rats one month following relief of obstruction.

RESULTS

Three months following relief of UUO during days 14 to 19, renal growth was decreased by 50%, compared to a 30% reduction following relief of UUO during days 1 to 5 (P < 0.05). The number of glomeruli was reduced by approximately 50% regardless of the timing of UUO, but glomerular size was reduced only in rats with UUO from days 14 to 19. Blood pressure and tubular atrophy were increased, and GFR, urine flow, sodium and potassium excretion were decreased in the postobstructed kidney of both neonatal groups. In the adult rat, the five-day UUO did not result in a decrease in the number of glomeruli.

CONCLUSIONS

In the period immediately following nephrogenesis, the kidney is particularly susceptible to long-term injury from temporary UUO. This suggests that a delay in relief of significant ureteral obstruction should be avoided if diagnosed in the perinatal or neonatal period.