Embryology and anatomy of the vesicoureteric junction with special reference to the etiology of vesicoureteral reflux

Primary vesicoureteral reflux

Primary vesicoureteral reflux (VUR) is one of the most common urological abnormalities in infants and children. The association of VUR, urinary tract infection (UTI) and renal parenchymal damage is well established. The most serious complications of VUR-associated reflux nephropathy are hypertension and proteinuria with chronic kidney disease. Over the past two decades, our understanding of the natural history of VUR has improved, which has helped to identify patients at increased risk of both VUR and VUR-associated renal injury. The main goals in the treatment of paediatric patients with VUR are the prevention of recurrent UTIs and minimizing the risk of renal scarring and long-term renal impairment. Currently, there are four options for managing primary VUR in infants and children: surveillance or intermittent treatment of UTIs with management of bladder and bowel dysfunction; continuous antibiotic prophylaxis; endoscopic subureteral injection of tissue-augmenting substances; and ureteral reimplantation via open, laparoscopic or robotic-assisted surgery. Current debates regarding key aspects of management include when to perform diagnostic imaging and how to best identify the paediatric patients that will benefit from continuous antibiotic prophylaxis or surgical intervention, including endoscopic injection therapy and minimally invasive ureteral reimplantation. Evolving technologies, such as artificial intelligence, have the potential to assist clinicians in the decision-making process and in the individualization of diagnostic imaging and treatment of infants and children with VUR in the future.

Development of the Urinary Tract in Fetal Rats: A Micro-CT Study

INTRODUCTION

 Micro-computed tomography (micro-CT) is an established tool to study fetal development in rodents. This study aimed to use micro-CT imaging to visualize the development of the urinary tract in fetal rats.

MATERIALS AND METHODS

 Fetal rats from embryonic day (ED) 15, ED17, ED19, ED21, and N0 (newborn) (n = 6 per group; 3 males) were fixed and desiccated using the "critical point" technique. We utilized the micro-CT system (SkyScan) and analyzed the resulting scans with CTAn, DataViewer, and ImageJ to visualize the morphology and quantify the volumes of kidney, bladder, adrenal gland, as well as length of the ureter.

RESULTS

 High-resolution micro-CT showed continuous growth of both kidneys from ED15 to N0, with the highest increase between ED19 and ED21. The length of the ureter increased from ED15 to ED21 and remained stable until birth. The volume of the bladder steadily increased from ED15 to N0.In females, a statistically higher volume of the adrenal gland on ED21 was observed, whereas no sex-specific differences were seen for kidney, ureter, and bladder development.

CONCLUSION

 Micro-CT depicts an excellent tool to study urinary tract development in the fetal and neonatal rat. It enables the metric quantification of longitudinal anatomic changes in high definition without previous destructive tissue preparation. The present study revealed sex-specific differences of the adrenal gland development and provides comprehensive data for the understanding of fetal urinary tract development, inspiring future research on congenital urological malformations.

De Novo Vesicoureteral Reflux Following Ureterocele Decompression in Children: A Systematic Review and Meta-Analysis Comparing Laser Puncture versus Electrosurgical Incision Techniques

Background: The available endoscopic techniques for ureterocele decompression include laser puncture (LP), electrosurgical incision (ES), and cold-knife incision. This systematic review was performed to compare the efficacy of LP versus ES techniques with special emphasis on de novo VUR. Methods: Four databases were systematically searched by the authors. The inclusion criteria were all comparative studies in which ureterocele decompression was performed by either LP or ES endoscopic techniques. Outcomes including the incidence of de novo VUR, the need for endoscopic retreatment of the ureterocele, and the need for secondary surgical procedures were studied. Risk ratios (RR) were calculated for all outcomes and the Mantel-Haenszel method was utilized for the estimation of pooled RR. The methodological quality was assessed by the Downs and Black scale. Results: Five studies were considered for systematic review, while four of them were included in the meta-analysis. Out of 202 children, 67 developed de novo VUR. Significantly lower rates of reflux were observed in the LP group vis-a-vis ES group (RR = 0.17, 95% CI 0.09 to 0.32, p < 0.00001). Endoscopic retreatment rates (n = 20) demonstrated no significant difference among the two patient groups (RR = 0.66, 95% CI 0.26–1.68, p = 0.38). A total of 46 secondary procedures were performed in 170 children, mostly ureteral re-implantations, with a significantly lower need of secondary surgeries following LP versus ES (RR = 0.26, 95% CI 0.13–0.49, p < 0.0001). The risk of bias in the included studies was low-to-moderate. Conclusions: When compared to the ES technique, the LP technique is associated with a significantly low incidence of de novo VUR and requirement for secondary surgeries (particularly anti-reflux surgeries). Endoscopic retreatment rates showed no significant difference between the two techniques. However, due to the moderate risk of bias in two out of four included studies, randomized controlled trials are needed in the future.

Critical analysis of the outcome of primary unilateral vesicoureteral reflux in a medium volume center

Background

Vesicoureteral reflux (VUR) is a common finding in pediatric age group. Here in we explored the possible risk factors that affect the rate of resolution in patients with primary unilateral VUR under conservative treatment.

Methods

Between 2006 and 2014, we retrospectively evaluated all VUR patients and included only patients with primary unilateral VUR. Records were reviewed for patient age at diagnosis, antenatal history, patient gender, mode of presentation, side, and grade of VUR, associated hydronephrosis (HN) on renal ultrasound, presence of scarring and split function on dimercaptosuccinic acid (DMSA) scan. Clinical and radiological outcomes were assessed. Both univariate and multivariate analysis were conducted.

Results

A total of 68 patients with primary unilateral VUR were included (32 boys and 36 girls) with a mean age of 10 months (range 1–32). Antenatal HN was detected in 50% of patients. In 15 cases (22%), VUR was of high grade (IV–V). Associated HN was evident in 39 patients (57%). DMSA scans showed renal scarring in 16 patients (23%). After a mean follow-up of 7 years, VUR resolved in 49 patients (72%). Significant predictors for VUR resolution were VUR grade, DMSA split function and associated high-grade HN. High-grade HN with VUR was the only significant independent risk factor.

Conclusions

The rate of resolution in primary unilateral VUR under conservative treatment is significantly affected by VUR grade, DMSA split renal function and the presence of associated HN. Association of high-grade HN with VUR carries a low chance for spontaneous resolution.

Study of prostate growth in prune belly syndrome and anencephalic fetuses

BACKGROUND

To compare the growth of the prostate in anencephalic, prune belly syndrome (PBS) and control fetuses.

METHODS

We studied 35 prostates from normal human fetuses aged 11-22 weeks postconception (WPC); 15 from anencephalic fetuses aged 13-19 WPC; and 6 from PBS fetuses aged 13-31WPC. After prostate dissection, we evaluated the prostate length, width and thickness with the aid of a computer program (Image Pro and Image J). The fetal prostate volume (PV) was calculated using the ellipsoid formula: PV = [length × thickness × width] × 0.523. The prostates were dissected and the PV was measured with the aid of the same computer program. Means were statistically compared using the unpaired t-test and linear regression was performed.

RESULTS

In 2 PBS fetuses we observed prostatic atresia. We did not observe significant differences in PV when comparing the control group (PV: 6.1 to 313.81 mm, mean = 70.85 mm: SD = 71.43 mm) with anencephalic fetuses: p = 0.3575 (PV: 5.1 to 159.11 mm, mean = 42.94 mm; SD = 40.11 mm) and PBS fetuses: p > 0.999 (PV: 10.89 to 148.71 mm, mean = 55.4 mm; SD = 63.64 mm). The linear regression analysis indicated that the PV in the control group (r² = 0.3096; p = 0.0004), anencephalic group (r² = 0.3778; p = 0.0148) and PBS group (r² = 0.9821; p < 0.009) increased significantly and positively with fetal age (p < 0.0001).

CONCLUSIONS

We did not observe significant differences in development of the prostate in fetuses with anencephaly and in 2/3 of fetuses with PBS during the fetal period studied. In 1/3 of the PBS fetuses, the prostate had important atresia.

LEVEL OF EVIDENCE

Level III.

Association of vesicoureteral reflux and gastroesophageal reflux disease in children: A population-based study

INTRODUCTION

Practitioners have anecdotally hinted at a possible association between gastroesophageal reflux disease (GERD) and vesicoureteral reflux (VUR). We sought to identify an association in diagnosis between GERD and VUR using a population-based dataset in a well-defined geographic area covered by a single-payer healthcare system.

METHODS

A retrospective review of individuals aged 0-16 years registered in the Nova Scotia Medical Service Insurance database from January 1997 to December 2012 was completed. Presence of GERD and VUR were ascertained based on billing codes. The baseline prevalence of GERD and VUR was calculated for this population for the same time period. Proportions of VUR patients with and without GERD were compared. The risk of being diagnosed with VUR in patients with GERD controlling for sex was calculated.

RESULTS

Of 404 300 patients identified, 6.6% had a diagnosis of GERD (n=27 092), 0.33% had a diagnosis of VUR (n=1348), and 0.08% were diagnosed with both (n=327). Among patients with VUR, the prevalence of GERD was 24.3% compared to 6.6% in patients without VUR (p<0.0001). Among patients with GERD, the prevalence of VUR was 1.2% compared to 0.27% in patients without (p<0.0001). The risk of being diagnosed with VUR was higher in the presence of GERD (odds ratio [OR] 4.49; 95% confidence interval [CI] 3.96-5.09; p<0.0001), irrespective of sex.

CONCLUSIONS

The odds of being diagnosed with VUR is more than 4.5 times higher in an individual with GERD. The clinical significance of this association remains to be explored.

Morphological study of the ureterovesical junction in children

Morphological and morphometric assessment of the elements of the ureterovesical junction in children was performed in the present study in different age groups ranging from 24 weeks of gestation to 16 years old. We tried to answer the question whether, in human ontogenesis, there is a period of anatomical predisposition to primary vesicoureteral reflux. The study included 210 urinary bladders with juxtavesical parts of the ureters that had been obtained from routine autopsies. As a result of the study, we showed that provided the pregnancy is uncomplicated there is no inherited susceptibility that would account for reducing or disturbing the development of ureterovesical junction elements. Based on the analysis of our results concerning the anatomy and morphological changes taking place in the elements of the ureterovesical junction in different age groups, one could put forward a hypothesis that anatomical predisposition to primary vesicoureteral reflux occurs in age group II, i.e. between 28 and 37 weeks of gestation. The parameters that define interrelations between elements of the ureterovesical junction and that are considered essential for normal functioning of antireflux mechanism were still observed in age group VI in our study. This suggests that these relations are not unambiguous in children with normally structured and functionally competent vesicoureteral junction.

The sheath of Waldeyer is not a specific anatomical trait of the ureterovesical junction

The function of the ureterovesical junction depends upon a peculiar structure, the adventitial fibromuscular sheath of Waldeyer, which coats the distal end of the ureter. The origin of the smooth muscle of Waldeyer's sheath (WS) is disputed. Evidence points more likely to an ureteral one. In this regard we hypothesized the WS is not specific to the distal ureter but is rather a common trait. We therefore aimed at exploring whether or not the proximal ureter is provided with a similar adventitial fibromuscular coat. We performed an immunohistochemical study on human samples of proximal ureter resulted after nephrectomies in ten patients. We applied myoid immunohistochemical markers: α-smooth muscle actin (α-SMA), desmin, and heavy chain of smooth muscle myosin (SMM) which labeled additional adventitial smooth muscle bundles, a discontinuous inner circular one applied on the muscular coat, and outer longitudinal cords specifically located on one side of the ureter, as is the case for WS. Moreover, the lamina propria myoid deep layer showed isolated smooth muscle fibers and spindle-shaped stromal cells with telocyte morphology. Our results support the idea that WS may not be a specific structure of the distal ureter, instead being just a common anatomical characteristic of the ureter.

Application of data mining techniques to explore predictors of upper urinary tract damage in patients with neurogenic bladder

This study proposed a decision tree model to screen upper urinary tract damage (UUTD) for patients with neurogenic bladder (NGB). Thirty-four NGB patients with UUTD were recruited in the case group, while 78 without UUTD were included in the control group. A decision tree method, classification and regression tree (CART), was then applied to develop the model in which UUTD was used as a dependent variable and history of urinary tract infections, bladder management, conservative treatment, and urodynamic findings were used as independent variables. The urethra function factor was found to be the primary screening information of patients and treated as the root node of the tree; Pabd max (maximum abdominal pressure, >14 cmH₂O), Pves max (maximum intravesical pressure, ≤89 cmH₂O), and gender (female) were also variables associated with UUTD. The accuracy of the proposed model was 84.8%, and the area under curve was 0.901 (95%CI=0.844-0.958), suggesting that the decision tree model might provide a new and convenient way to screen UUTD for NGB patients in both undeveloped and developing areas.

Vesicoureteral reflux and the extracellular matrix connection

Primary vesicoureteral reflux (VUR) is a common pediatric condition due to a developmental defect in the ureterovesical junction. The prevalence of VUR among individuals with connective tissue disorders, as well as the importance of the ureter and bladder wall musculature for the anti-reflux mechanism, suggest that defects in the extracellular matrix (ECM) within the ureterovesical junction may result in VUR. This review will discuss the function of the smooth muscle and its supporting ECM microenvironment with respect to VUR, and explore the association of VUR with mutations in ECM-related genes.

Estimation of the relationship between the polymorphisms of selected genes: ACE, AGTR1, TGFβ1 and GNB3 with the occurrence of primary vesicoureteral reflux

PURPOSE

Etiopathogenesis of VUR is composite and not fully understood. Many data indicate the importance of genetic predisposition. The aim of this study was to establish the relationship of selected polymorphisms: 14094 polymorphism of the ACE, polymorphism rs1800469 of TGFβ-1, rs5443 gene polymorphism of the GNB3 and receptor gene polymorphism rs5186 type 1 AGTR1 with the occurrence of the primary vesicoureteral reflux.

MATERIAL

The study included 190 children: 90 with the primary VUR confirmed with the voiding cystourethrogram and excluded secondary VUR and a control group of 100 children without a history of the diseases of the genitourinary tract.

METHODS

The study was planned in the scheme: "tested case versus control." Genomic DNA was isolated from the leukocytes of peripheral blood samples. The results were statistically analyzed in the Statistica 10 using χ ² test and analysis of the variance Anova.

RESULTS

Any of the four studied polymorphisms showed no difference in the distribution of genotypes between patients with primary vesicoureteral reflux and the control group. In patients with VUR and TT genotype polymorphism rs5443 GNB3 gene, the glomerular filtration rate was significantly higher than in patients with genotype CC or CT.

CONCLUSIONS

(1) No relationship was found between the studied polymorphisms (14094 ACE gene, rs1800469 gene TGFβ1, GNB3 gene rs5443, rs5186 AGTR1 gene) and the occurrence of primary vesicoureteral reflux. (2) TT genotype polymorphism rs5443 GNB3 gene may be a protective factor for the improved renal function in patients with primary vesicoureteral reflux in patients with genotype CC or CT.

Copy-number variation associated with congenital anomalies of the kidney and urinary tract

BACKGROUND

The most common cause of end-stage renal disease in children can be attributed to congenital anomalies of the kidney and urinary tract (CAKUT). Despite this high incidence of disease, the genetic mutations responsible for the majority of CAKUT cases remain unknown.

METHODS

To identify novel genomic regions associated with CAKUT, we screened 178 children presenting with the entire spectrum of structural anomalies associated with CAKUT for submicroscopic chromosomal imbalances (deletions or duplications) using single-nucleotide polymorphism (SNP) microarrays.

RESULTS

Copy-number variation (CNV) was detected in 10.1 % (18/178) of the patients; in 6.2 % of the total cohort, novel duplications or deletions of unknown significance were identified, and the remaining 3.9 % harboured CNV of known pathogenicity. CNVs were inherited in 90 % (9/10) of the families tested. In this cohort, patients diagnosed with multicystic dysplastic kidney (30 %) and posterior urethral valves (24 %) had a higher incidence of CNV.

CONCLUSIONS

The genes contained in the altered genomic regions represent novel candidates for CAKUT. This study has demonstrated that a significant proportion of patients with CAKUT harbour submicroscopic chromosomal imbalances, warranting screening in clinics for CNV.

Ultrastructural and immunohistopathological evaluation of intravesical ureters via electron and light microscopy in children with vesicoureteral reflux

PURPOSE

We used immunohistochemical methods and transmission electron microscopy to investigate the cytokine profiles and ultrastructural changes in the ureterovesical junction of children with primary vesicoureteral reflux.

MATERIALS AND METHODS

A total of 39 distal intravesical ureters were obtained from 23 children who underwent ureteroneocystostomy for primary vesicoureteral reflux. Ureteral wall smooth muscle organization and transforming growth factor-β1, vascular endothelial growth factor and CD34 were evaluated immunohistochemically and compared to controls, which consisted of 10 age matched autopsy specimens. Ultrastructural evaluations and morphological descriptions were performed semiquantitatively and compared to the published data.

RESULTS

Of the patients 6 (26%) were male and 17 (74%) were female, and mean ± SD age was 73.2 ± 34.3 months (range 12 to 168). There was no correlation between reflux grade and age (p = 0.39). Smooth muscle disorganization score differed significantly between patients with intravesical ureters and controls (p = 0.01). Transforming growth factor-β1 levels were significantly higher (p = 0.001) and vascular endothelial growth factor levels and microvessel densities were significantly lower in the patients with reflux compared to controls (both p <0.001). Vascular endothelial growth factor, CD34 and transforming growth factor-β1 levels did not correlate with reflux grades (p = 0.84, p = 0.76 and p = 0.10, respectively). Urothelium, lamina propria and tunica adventitia appeared normal in the specimens for all grades of vesicoureteral reflux using transmission electron microscopy. Damage was observed in the muscular layers of the ureterovesical junction, especially in patients with grade IV or V reflux.

CONCLUSIONS

Primary refluxing ureters exhibit immunohistopathological abnormalities compared to normal ureters irrespective of reflux grade, and ultrastructural changes are especially severe in cases of high grade reflux. These abnormalities can hinder the normal ureteral valve mechanism, and may lead to reflux due to smooth muscle dysfunction and microvascular alterations.

3-Dimensional morphometric analysis of murine bladder development and dysmorphogenesis

BACKGROUND

Disorders of the urinary tract represent a major cause of morbidity and impaired quality of life. To better understand the morphological events responsible for normal urinary tract development, we performed 3-D reconstructive analysis of developing mouse bladders in control, mgb-/-, and Fgfr2(Mes-/-) mice.

RESULTS

Detrusor smooth muscle differentiation initiated in the bladder dome and progressed caudally with the leading edge extending down the right posterior surface of the bladder. Gender-specific differences in detrusor smooth muscle development were observed during early embryonic development. Bladder trigone morphology transitioned from an isosceles to equilateral triangle during development due to the preferential lengthening of the urethra to ureter distance. The primary defect observed in mgb-/- bladders was a significant reduction in detrusor smooth muscle differentiation throughout development. Deviations from normal trigone morphology correlated best with VUR development in Fgfr2(Mes-/-) mice, while alterations in intravesicular tunnel length did not.

CONCLUSIONS

Multivariate morphometric analysis provides a powerful tool to quantify and assess urinary tract development.

Hypothesis - a congenitally lax pubourethral ligament may be a contributing cause of vesicoureteral reflux

INTRODUCTION

The hypothesis derives from the field of female stress incontinence. Application of pressure on the anterior vaginal wall at midurethra with a hemostat restores the geometry of the vesicoureteral junction and continence.

METHODS

We applied unilateral midurethral pressure during a radiological investigation of a 15-year-old female patient who had undergone 2 surgeries for ureteric reflux.

RESULTS

On injection of the dye into the bladder, reflux was noted in the left ureter, and this disappeared within 2-3 seconds after pressure was applied on 2 successive occasions in the midurethral area of the vagina.

CONCLUSION

The hypothesis that a musculoelastic mechanism dependent on a competent pubourethral ligament may play a role in vesicoureteral valve closure appears to have been confirmed, at least in one case. Hopefully this observation will lead to further studies, and perhaps, new directions for therapy.