The molecular biology of pelvi-ureteric junction obstruction

Stromal vascular fraction inhibits renal fibrosis by regulating metabolism and inflammation in obstructive nephropathy

Obstructive nephropathy is one of the leading causes of kidney injury and fibrosis, which can lead to end-stage renal disease (ESRD). Stromal vascular fraction (SVF), a heterogeneous cell mixture derived from adipose tissue, has been widely used for regenerative medicine across many preclinical models and clinical applications. Recent studies have suggested that SVF can alleviate acute kidney injury in mice. However, to our knowledge, the therapeutic effects of SVF on obstructive nephropathy have not been studied before. In this study, we evaluated the therapeutic potential of SVF on obstructive nephropathy in mice with unilateral ureteral obstruction (UUO). We revealed that autologous SVF administration mitigated UUO-induced renal fibrosis. SVF treatment inhibited both the infiltration of neutrophils and CD4+ T cells, as well as the production of inflammatory cytokines. Moreover, SVF promoted metabolic reprogramming and improved mitochondrial function in the obstructed kidneys, partially through PPAR pathway activation. Mechanistically, SVF-mediated PPAR activation inhibited the epithelial-mesenchymal transition (EMT) process of tubular cells, thus alleviating renal fibrosis in UUO mice. We further confirmed that pharmacological activation of PPAR pathway significantly reduced fibrosis in UUO kidneys. Therefore, our study suggests that SVF may represent a promising therapeutic strategy for obstructive nephropathy.

Intraoperative urinary ACR as a prognostic biomarker in unilateral pelviureteric junction obstruction in paediatric population-an observational study

BACKGROUND

Many urinary biomarkers like MCP1, EGF, KIM1, CCL5/RANTES, CA19.9, NAG, TTF and micro albumin have been used as indicators of renal damage in HDN patients. Urine albumin-to-creatinine ratio (ACR) is widely used to detect renal damage in systemic diseases like diabetes and hypertension. While extensively studied in medical renal diseases, its role as an intraoperative prognostic biomarker for renal damage remains unexplored. ACR offers advantages such as low cost, easy availability, and spot testing.

AIMS

To determine the correlation between urinary ACR from obstructed pelvis in the prognostication of renal function of children with unilateral pelviureteric junction obstruction.

METHODS

This prospective observational pilot study included 30 patients with unilateral PUJO, aged over six months, undergoing Anderson-Hynes pyeloplasty. Patients underwent a standardized diagnostic protocol, including USG-KUB and technetium-99m DTPA renal scans. Preoperative urinary ACR from voided urine was measured. During surgery, urine from the obstructed pelvis was aspirated for ACR analysis. Data analysis compared preoperative and postoperative variables and intra-operative urinary ACR levels were correlated with change in differential renal function on DTPA.

DISCUSSION

Postoperative outcomes currently rely on dynamic nuclear renal scans and USG performed 3 months after surgery. Intraoperative urinary ACR from the obstructed renal pelvis shows promise as an early biomarker for predicting renal function outcomes after pyeloplasty. It provides immediate results, alleviating parental anxiety by eliminating the usual delay in postoperative assessments.

CONCLUSION

This study highlights the potential role of urinary ACR for peri-operative prognostication in children with PUJO, though larger studies are required to confirm these findings.

LEVEL OF EVIDENCE

Level 2B - Prospective observational study.

Accuracy of Sonographic Renal Pelvic Diameter in Assessment of Renal Function among Patients with Ureteropelvic Junction Obstruction using Scintigraphy as a Gold Standard

Objectives: The study aimed to assess the diagnostic accuracy of sonographic renal pelvic diameter (RPD) in pediatric patients with ureteropelvic junction obstruction (UPJO) and its potential as a solo diagnostic tool. The study also looked for a clinically meaningful cutoff point in sonographic RPD, with the goal of optimizing sensitivity and specificity for discriminating between normal and impaired renal function in UPJO cases. Materials and methods: The study, which took place at a maternity and child hospital, involved 75 children under the age of three who had been diagnosed with UPJO. Data was collected from 2020 to 2022 using both ultrasonography and renal scintigraphy, with cases diagnosed using only one modality being excluded. Results: The analysis included descriptive and t-tests. The results demonstrated a significant difference in sonographic RPD between pediatric patients with normal and impaired renal function and with large and normal renal diameters. The average renal pelvis diameter was found to be 2.2 ±1.9 cm. The sensitivity and specificity of sonographic RPD for predicting impaired renal function in UPJO vary significantly across multiple cutoff points, underlining RPD's diagnostic potential. Conclusion: The study concluded that combining two modalities (ultrasound and scintigraphy) improves results when the renal pelvic diameter surpasses 1 cm.

The etiology of congenital obstructive uropathy: developmental and genetic perspectives

Congenital obstructive uropathy (COU) encompasses a heterogeneous group of anomalies arising during critical stages of fetal development, which are characterized by functional or structural obstruction of the urinary tract. This obstruction hampers normal urine flow, and the resulting urinary pressure build-up can damage the developing kidneys and bladder. COU pathogenesis is complex and its clinical outcomes are highly variable, ranging from asymptomatic ultrasonographic abnormalities to end-stage kidney disease. This review examines the developmental and genetic mechanisms underlying COU and the associated organ damage, with a focus on intrinsic, isolated forms. Although genetic studies have improved our understanding of the molecular pathways involved in urinary tract maldevelopment, most patients lack a genetic diagnosis. Hence, multiple etiologic factors appear at play, including (epi)genetic and environmental. Closing gaps in our knowledge of kidney and urinary tract development and their interdependency for normal function is essential for developing personalized care to ultimately improve patient outcomes.

Ultrasound and magnetic resonance imaging features of fetal urogenital anomalies: A pictorial essay

This pictorial essay focuses on ultrasound (US) and magnetic resonance imaging (MRI) features of fetal urogenital anomalies. Fetal urogenital malformations account for 30%-50% of all anomalies discovered during pregnancy or at birth. They are usually detected by fetal ultrasound exams. However, when ultrasound data on their characteristics is insufficient, MRI is the best option for detecting other associated anomalies. The prognosis highly depends on their type and whether they are associated with other fetal abnormalities.

Comparison between open and minimally invasive pyeloplasty in infants: A systematic review and meta-analysis

INTRODUCTION

Ureteropelvic junction obstruction (UPJO) is the most common cause of congenital hydronephrosis. Techniques such as laparoscopic pyeloplasty (LP) have gained in popularity over recent years. Although some retrospective studies have compared minimally invasive reconstructive techniques with open surgery for treatment of UPJO in infants, results remain controversial due to the small sample size in most of these studies.

OBJECTIVE

To verify whether the benefits of minimally invasive pyeloplasty (MIP) observed in adults and children over 2 years of age also apply to infants.

METHODS

A systematic review of the literature was performed according to PRISMA recommendations. We searched databases of MEDLINE, EMBASE, Web of Science, and Cochrane Central Register of Controlled Trials. We excluded studies in which patient cohorts were outside the age range between 1 and 23 months of age (infants). Studies should evaluate at least one of the following outcomes: average hospital stay, operative time, follow-up time, complications, post-surgical catheter use, success rate and reintervention rate. The quality of the evidence was assessed with the ROBINS-I tool.

RESULTS

In total, 13 studies were selected. 3494 patients were included in the meta-analysis, of whom 3054 underwent OP, while the remaining 440 were part of the group undergoing MIP. The mean difference in hospital days was -1.16 lower the MIP group (95 % CI; -1.78, -0.53; p = 0.0003). Also, our analysis showed a significantly shorter surgical time in the group who underwent OP, with a mean operative time of 119.92 min, compared to 137.63 min in the MIP group (95 % CI; -31.76, -6.27; p = 0.003). No statistically significant between-group differences were found respect to follow-up time, complications, post-surgical catheter use, success rate and reintervention rate.

CONCLUSION

This systematic review with meta-analysis has shown that laparoscopic/robotic pyeloplasty in infants is a safe technique with similar success rates to open surgery. Nonetheless, randomized clinical trials with longer follow-up are needed to consolidate these results with more robust scientific evidence.

Techniques in minimally invasive transperitoneal pyeloplasty: A compilation

Context

Minimally invasive management (laparoscopic/robot assisted) is currently the standard of care for managing pelvi ureteric junction obstruction (PUJO). Open techniques of management of PUJO are well described in literature. However, there appears to be relative lack of description of minimally invasive techniques in the literature.

Objective

This article is aimed at describing in detail, with images, the various techniques and modifications in laparoscopic or robot-assisted management of PUJO.

Evidence Acquisition

A review of literature on PubMed was performed and all articles which detailed any technique of minimally invasive pyeloplasty were included.

Evidence Synthesis

The various techniques of minimally invasive pyeloplasty as well as the authors' techniques are compiled and described in detail with intraoperative images.

Conclusions

Operative techniques of minimally invasive pyeloplasty are not well described in literature. We have attempted to present a comprehensive resource of different techniques of minimally invasive pyeloplasty and the clinical scenarios in which they may be appropriate. This should prove to be a useful reference to the practicing urologist.

Patient Summary

In this paper, we have compiled the various surgical techniques of treating obstruction at the PUJ of the kidney along with intraoperative photograph.

Expression and clinical implications of PARs in the stenotic tissue of ureteropelvic junction obstruction

Objective

To explore the expression and clinical implications of protease activated receptors (PARs) in the pathogenesis of children with ureteropelvic junction obstruction (UPJO).

Material and methods

Immunohistochemistry was employed to investigate the distribution of PARs in both normal human ureteropelvic junction (UPJ) and cases of UPJO. Furthermore, PAR gene expression levels were assessed using real-time PCR (RT-PCR), and the patients in the UPJO group were stratified according to the Onen grading system. Subsequently, the clinical implications of PARs in UPJO were explored through RT-PCR analysis.

Results

Immunofluorescence showed robust PAR2 expression in the control group compared with the UPJO group. The results of RT-PCR analysis revealed a significant decrease in the relative mRNA expression of PAR2 in the UPJO group compared to the control group. Notably, the relative RNA expression of PAR1 was significantly lower in the Onen-4 group compared to the control group. Furthermore, the relative mRNA expression of PAR2 exhibited a statistically significant difference among the Onen-3 group, Onen-4 group, and control group.

Conclusions

PARs are widely distributed throughout the SIP syncytium of the UPJ and play a role in maintaining smooth muscle cells (SMCs) membrane potential by interacting with interstitial cells of Cajal (ICCs), as well as platelet-derived growth factor receptor alpha-positive cells (PDGFR α+ cells). The decreased expression of PAR1 suggests a higher preoperative Onen grade in UPJO patients. Furthermore, the downregulation of PAR2 effects at the UPJ may be involved in the loss of inhibitory neuromuscular transmission, disrupting the rhythmic peristalsis of the UPJ.

Association between intraoperative anatomical variation and histopathological parameters in cases of ureteropelvic junction obstruction in children: A cross-sectional study

Introduction

The intraoperative anatomical findings (IOAF) of all ureteropelvic junction obstruction (UPJO) cases are not identical. Moreover, there is also controversy in the literature regarding histopathological (HP) findings in cases of UPJO. In the present study, we evaluated different IOAF and assessed their association with specific HP parameters.

Materials and Methods

This was a cross-sectional study set-up, which was carried out in a tertiary care centre. Children with UPJO who underwent surgery between 2017 and 2020 were enrolled. The following IOAF were noted: Type of pelvis (extrarenal or intrarenal), insertion of the ureter (high or normal), presence of lower pole crossing vessel (CV), negotiation of UPJ segment with double J stent (3 Fr) and length of internal narrowing (LIN) at UPJ. The resected segment of UPJ was assessed at three levels (pelvis, UPJ and ureter) for various HP parameters including fibrosis, oedema, inflammation and smooth muscle hypertrophy (SMH).

Results

Thirty-nine children were included in the study with a mean age of 31 months. The summary statistics of IOAF were intrarenal pelvis in 5 cases, high insertion of the ureter (HIU) in 9, CV in 6, negotiable UPJ in 23, and 16 cases showed LIN >1 cm. All cases showed SMH at the pelvis region and SMH with fibrosis at the UPJ region. At the pelvis region, there was an association between (1) HIU with oedema and chronic inflammation (CIF), (2) CV with CIF and (3) LIN with CIF and SMH. At the UPJ region, there was an association between (1) CV and negotiable UPJ with less fibrosis and (2) LIN with SMH. At the ureteric end, CV showed an association with less fibrosis and more CIF.

Conclusion

All UPJO cases have some common HP findings. Although, some particular IOAF, i.e., presence of CV, negotiable UPJ, HIU and LIN showed association with specific HP parameters.

Radiological and surgical correlation of pelviureteric junction obstruction in positional anomalies of the kidney in children

Pelviureteric junction obstruction, also known as ureteropelvic junction obstruction, is a congenital narrowing of the urinary excretory tract at the junction between the renal pelvis and the ureter and is a common cause of congenital pelvicalyceal dilatation. The outcome is variable, from spontaneous resolution to renal parenchymal function loss in cases of untreated high-grade obstruction. Abnormalities in renal ascent, rotation and vascularity can be associated with pelviureteric junction obstruction and easily overlooked radiologically. In this pictorial review, we explore the anatomical, radiological and surgical correlations of pelviureteric junction obstruction in the context of a normal kidney and a spectrum of renal abnormalities, including hyper-rotation (also known as renal malrotation), failed renal ascent, fusion anomalies and accessory crossing renal vessels. For each scenario, we provide technical tips on how to identify the altered anatomy at the first ultrasound assessment and correlation with scintigraphic, cross-sectional and postoperative imaging where appropriate. A detailed ultrasound protocol specifically to assess and characterise pelviureteric junction obstruction in paediatric patients is also offered.

Comprehensive Proteomics Analysis Identifies CD38-Mediated NAD+ Decline Orchestrating Renal Fibrosis in Pediatric Patients With Obstructive Nephropathy

Obstructive nephropathy is one of the leading causes of kidney injury and renal fibrosis in pediatric patients. Although considerable advances have been made in understanding the pathophysiology of obstructive nephropathy, most of them were based on animal experiments and a comprehensive understanding of obstructive nephropathy in pediatric patients at the molecular level remains limited. Here, we performed a comparative proteomics analysis of obstructed kidneys from pediatric patients with ureteropelvic junction obstruction and healthy kidney tissues. Intriguingly, the proteomics revealed extensive metabolic reprogramming in kidneys from individuals with ureteropelvic junction obstruction. Moreover, we uncovered the dysregulation of NAD⁺ metabolism and NAD⁺-related metabolic pathways, including mitochondrial dysfunction, the Krebs cycle, and tryptophan metabolism, which led to decreased NAD⁺ levels in obstructed kidneys. Importantly, the major NADase CD38 was strongly induced in human and experimental obstructive nephropathy. Genetic deletion or pharmacological inhibition of CD38 as well as NAD⁺ supplementation significantly recovered NAD⁺ levels in obstructed kidneys and reduced obstruction-induced renal fibrosis, partially through the mechanisms of blunting the recruitment of immune cells and NF-κB signaling. Thus, our work not only provides an enriched resource for future investigations of obstructive nephropathy but also establishes CD38-mediated NAD⁺ decline as a potential therapeutic target for obstruction-induced renal fibrosis.

Comparing accuracy of urinary biomarkers in differentiation of ureteropelvic junction obstruction from nonobstructive dilatation in children

Multiple urinary biomarkers have been reported in differentiation of nonobstructive dilatation (NOD) from ureteropelvic junction obstruction (UPJO). In this meta-analysis, we compared the accuracy of common urinary biomarkers applicable to UPJO. A systematic literature review of electronic databases was conducted for: (UPJO) OR (NOD) AND (urinary biomarkers) AND (children) for articles published in the last decade. PRISMA guidelines were used to exclude duplicate and erroneous articles. Meta-analysis involved risk of bias analysis, heterogeneity assessment, and comparison of sensitivity/specificity by forest plot analysis using MetaXL 5.3. Among the 264 articles analyzed, 19 articles met the inclusion criteria and reported the following: neutrophil gelatinase-associated lipocalin (NGAL), monocyte chemotactic protein-1 (MCP1), carbohydrate antigen 19-9 (CA 19-9), kidney injury molecule (KIM1), epidermal growth factor (EGF), and interferon gamma induced protein-10 (IP10). There was substantial heterogeneity among articles. There was wide variation in applied cut-offs among studies. Overall sensitivity was highest at 87% for CA 19-9 while overall specificity was highest at 76% for NGAL. Overall accuracy was highest at 78% for CA 19-9 followed by 77% for NGAL and 75% for KIM1. In this meta-analysis, the overall accuracy was highest for CA 19-9 followed by NGAL and KIM1. The small number of studies for CA 19-9 and considerable heterogeneity for all should be considered while interpreting these findings. Based on the current meta-analysis, we support a panel of biomarkers combining NGAL, KIM, and CA 19-9 for the best diagnostic accuracy of UPJO in children.

A Comparative Analysis of Robot-Assisted Laparoscopic Pyeloplasty in Pediatric and Adult Patients: Does Age Matter?

We investigated factors that affect the surgical outcomes of robotic pyeloplasty by comparing the surgical results of pediatric and adult patients with ureteropelvic junction stricture (UPJO). We retrospectively reviewed patients who underwent robotic pyeloplasty for UPJO between January 2013 and February 2022. The patients were categorized into two groups: the pediatric (≤18 years) and adult (>18 years) groups. The perioperative and postoperative outcomes and surgical complications were comparatively analyzed. Prognostic factors for predicting surgical failure were analyzed with multivariable logistic regression analysis. The pediatric group showed longer total operation and console times. The mean pain score was lower in the pediatric group than in the adult group on days 1 and 2 after surgery. The average amount of morphine used in the pediatric group was lower during postoperative days 0−2. No differences in the length of hospital stay, incidence of surgical failure, and incidence of urolithiasis requiring treatment after robotic pyeloplasty were observed between the groups. The only factor that predicted surgical failure was a history of urolithiasis before surgery. The results showed that age did not affect the surgical outcome.

Chronic Kidney Disease in Boys with Posterior Urethral Valves-Pathogenesis, Prognosis and Management

Posterior urethral valves (PUV) are the most common form of lower urinary tract obstructions (LUTO). The valves can be surgically corrected postnatally; however, the impairment of kidney and bladder development is irreversible and has lifelong implications. Chronic kidney disease (CKD) and bladder dysfunction are frequent problems. Approximately 20% of PUV patients will reach end-stage kidney disease (ESKD). The subvesical obstruction in PUV leads to muscular hypertrophy and fibrotic remodelling in the bladder, which both impair its function. Kidney development is disturbed and results in dysplasia, hypoplasia, inflammation and renal fibrosis, which are hallmarks of CKD. The prognoses of PUV patients are based on prenatal and postnatal parameters. Prenatal parameters include signs of renal hypodysplasia in the analysis of fetal urine. Postnatally, the most robust predictor of PUV is the nadir serum creatinine after valve ablation. A value that is below 0.4 mg/dl implies a very low risk for ESKD, whereas a value above 0.85 mg/dl indicates a high risk for ESKD. In addition, bladder dysfunction and renal dysplasia point towards an unbeneficial kidney outcome. Experimental urinary markers such as MCP-1 and TGF-β, as well as microalbuminuria, indicate progression to CKD. Until now, prenatal intervention may improve survival but yields no renal benefit. The management of PUV patients includes control of bladder dysfunction and CKD treatment to slow down progression by controlling hypertension, proteinuria and infections. In kidney transplantation, aggressive bladder management is essential to ensure optimal graft survival.

Exosomal proteomics in kidney disease: From technical approaches to clinical applications

Exosomes are small extracellular vesicles (sEVs) secreted from cells and have a general diameter ranging from 30-150 nm. It was reported that exosomes have essential roles in intercellular communication and can be targeted as biomarkers of disease or as therapeutic agents. Among the different techniques used for exosome investigation, the mass spectrometry-based proteomics approach has accelerated the unraveling of the molecular composition of exosomes and has contributed to improved knowledge of molecular processes in various diseases. In this review, we focused on proteomics-based studies of exosomes and clinical applications in kidney diseases. A general introduction of exosomes, isolation and characterization techniques, and proteomics-based study workflows are included in this article. We also categorized applications in acute kidney injury, chronic kidney disease, renal transplantation, congenital kidney disease, and malignant kidney disorder to show the important findings from proteomics-based exosomal investigations.

Evaluation of PGP 9.5, NGFR, TGFβ1, FGFR1, MMP-2, AT2R2, SHH, and TUNEL in Primary Obstructive Megaureter Tissue

Primary obstructive megaureter (POM) morphogenesis is not fully known. The aim of the study was to evaluate the appearance of different factors that might take part in the pathogenesis of POM. Megaureter tissues of 14 children were stained with hematoxylin and eosin as well as with immunohistochemistry for protein gene product 9.5, nerve growth factor receptor, transforming growth factor beta 1 (TGFβ1), fibroblast growth factor receptor 1 (FGFR1), matrix metalloproteinase 2 (MMP-2), angiotensin 2 receptor type 2, and sonic hedgehog (SHH) protein. Apoptosis was detected by terminal dUTP nick-end labeling reaction. POM tissues revealed transitional epithelium with scattered vacuolization, submucosa with inflammatory cells, and focally vacuolized and chaotically organized muscle layers. Apoptosis, appearance of MMP-2, FGFR1, and SHH prevailed, but TGFβ1 positive cell number was lower in patients. Correlation between MMP-2 in epithelium and endothelium, FGFR1 and MMP-2 in epithelium, and TGFβ1 in epithelium and connective tissue in patients was detected. POM morphopathogenesis involves an apoptotic cell death of epithelium and smooth muscle as well as tissue degradation in epithelium and connective tissue of the ureter wall. The decrease of tissue growth through diminished TGFβ1 expression and stimulation of FGFR1 and MMP-2 suggests a disbalance of tissue remodelation in the megaureter wall.

Evaluation of Interstitial Cells of Cajal-Like Cells at the Pelviureteric Junction in Children with Pelviureteric Junction Obstruction: A Prospective Study and Review of Literature

INTRODUCTION

The etiopathogenesis of pelviureteric junction obstruction (PUJO) has been debated. Recently, the role of interstitial cells of Cajal-like cells (ICC-LC)has been studied and reported to be the cause of this functional obstruction. We studied the histopathology and ICC-LC density at PUJ and compared it with that of PUJ of the control group and distal ureteric margin of the study group.

METHODS

A prospective study was conducted which included PUJO patients in the study group and the renal tumor patients in the control group. Histopathological examination (muscle hypertrophy and fibrosis) and immunohistochemistry (ICC-LC density) were done. The muscle hypertrophy, fibrosis, and ICC-LC density at the PUJ in both the groups were compared. A similar comparison was performed between the findings at the PUJ and the distal margin in the study group.

RESULTS

The study and control groups included 37 PUJO patients and 13 Wilms tumor patients. The ICC-LC density at PUJ in the study group was significantly lower than that in the control group (P < 0.001) and that at the distal resected margin of the study group (P < 0.001). Significantly increased muscle hypertrophy (P < 0.001) and fibrosis (P = 0.002) were seen at PUJ in the study group compared to the control group. No significant association was noted between the ICC-LC density and muscle hypertrophy at PUJ and the distal resected margin in the study group.

CONCLUSION

A significant decrease in the density of ICC-LC and increased fibrosis and muscle hypertrophy at PUJ in children with PUJO play a role in the etiopathogenesis of the disease.

Renal Cortical Thickness After Pyeloplasty in Pediatric Ureteropelvic Junction Obstruction

Purpose

The main goal of pyeloplasty is to maintain or improve renal function. Diuretic renography is the gold standard for evaluating renal function after pyeloplasty. Renal ultrasonography (RUS) is commonly used to determine hydronephrosis in pediatric patients. We hypothesized that the change in the renal parenchymal cortex would predict pyeloplasty success. In this study, we aim to measure renal cortical thickness change after pyeloplasty in ureteropelvic junction obstruction patients.

Materials and Methods

We retrospectively reviewed 38 patients who underwent pyeloplasty between 2005 and 2019. We divided patients into three age groups and compared the difference of renal parenchymal thickness change by using generalized estimating equations to identify associated factors for renal cortical thickness change after pyeloplasty.

Results

Thirty-nine kidney units were identified. The median age at the time of surgery was 41.61±40.99 months. Generalized estimating equations showed significant change of renal parenchymal thickness over the period of follow-up (p=0.02). The estimate of thickness change was 0.0373 mm/month. Age at the time of surgery was not associated with significant renal cortical thickness over the period of follow-up. The positive predictive factors for renal cortical thickness were creatinine clearance, pre-operative anteroposterior diameter and pre-operative renal differential function. The negative factors for decrease of renal cortical thickness were body weight, presentation with abdominal mass, and history of infection.

Conclusion

Renal cortical thickness after pyeloplasty was improved over the period of follow-up. Age at surgery was not associated with improvement of renal parenchymal thickness.

Minimal Invasive Treatment in Pelvic-Ureteric Junction Obstruction: A Comprehensive Review

Pelvic-ureteric junction obstruction (PUJO) is a common condition, and one of the lead causes of hydronephrosis in children. Currently, the gold standard treatment of PUJO is open surgery using the Anderson–Hynes-modified dismembered pyeloplasty technique. However, with the advancement of medical technology, several minimal invasive approaches were developed, including endoscopic, laparoscopic, and robotic approach, from which the best choice of surgical technique was yet to be determined. Considering the advantages and disadvantages of these methods, the recommended option is to tailor the best surgical approach to each individual patient, and to the surgeons’ preference and experience. Considering these recent advances, a new algorithm is proposed to choose the best minimal invasive modalities invasive treatment to treat PUJO.

The Genomic Response to TGF-β1 Dictates Failed Repair and Progression of Fibrotic Disease in the Obstructed Kidney

Tubulointerstitial fibrosis is a common and diagnostic hallmark of a spectrum of chronic renal disorders. While the etiology varies as to the causative nature of the underlying pathology, persistent TGF-β1 signaling drives the relentless progression of renal fibrotic disease. TGF-β1 orchestrates the multifaceted program of kidney fibrogenesis involving proximal tubular dysfunction, failed epithelial recovery or re-differentiation, capillary collapse and subsequent interstitial fibrosis eventually leading to chronic and ultimately end-stage disease. An increasing complement of non-canonical elements function as co-factors in TGF-β1 signaling. p53 is a particularly prominent transcriptional co-regulator of several TGF-β1 fibrotic-response genes by complexing with TGF-β1 receptor-activated SMADs. This cooperative p53/TGF-β1 genomic cluster includes genes involved in cellular proliferative control, survival, apoptosis, senescence, and ECM remodeling. While the molecular basis for this co-dependency remains to be determined, a subset of TGF-β1-regulated genes possess both p53- and SMAD-binding motifs. Increases in p53 expression and phosphorylation, moreover, are evident in various forms of renal injury as well as kidney allograft rejection. Targeted reduction of p53 levels by pharmacologic and genetic approaches attenuates expression of the involved genes and mitigates the fibrotic response confirming a key role for p53 in renal disorders. This review focuses on mechanisms underlying TGF-β1-induced renal fibrosis largely in the context of ureteral obstruction, which mimics the pathophysiology of pediatric unilateral ureteropelvic junction obstruction, and the role of p53 as a transcriptional regulator within the TGF-β1 repertoire of fibrosis-promoting genes.

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.

Roles Played by Biomarkers of Kidney Injury in Patients with Upper Urinary Tract Obstruction

Partial or complete obstruction of the urinary tract is a common and challenging urological condition caused by a variety of conditions, including ureteral calculi, ureteral pelvic junction obstruction, ureteral stricture, and malignant ureteral obstruction. The condition, which may develop in patients of any age, induces tubular and interstitial injury followed by inflammatory cell infiltration and interstitial fibrosis, eventually impairing renal function. The serum creatinine level is commonly used to evaluate global renal function but is not sensitive to early changes in the glomerular filtration rate and unilateral renal damage. Biomarkers of acute kidney injury are useful for the early detection and monitoring of kidney injury induced by upper urinary tract obstruction. These markers include levels of neutrophil gelatinase-associated lipocalin (NGAL), monocyte chemotactic protein-1, kidney injury molecule 1, N-acetyl-b-D-glucosaminidase, and vanin-1 in the urine and serum NGAL and cystatin C concentrations. This review summarizes the pathophysiology of kidney injury caused by upper urinary tract obstruction, the roles played by emerging biomarkers of obstructive nephropathy, the mechanisms involved, and the clinical utility and limitations of the biomarkers.

The effect of intravenous human adipose-derived stem cells (hADSC) on transforming growth factor β1 (TGF-β1), collagen type 1, and kidney histopathological features in the unilateral ureteropelvic junction obstruction model of wistar rats

OBJECTIVE

The fibrotic process of kidney resulting in glomerulosclerosis was found in patients with ureteropelvic junction obstruction (UPJO) who underwent renal biopsy during pyeloplasty. Transforming growth factor β1 (TGF-β1) plays a role in collagen accumulation, resulting in fibrosis. Adipose tissue-derived stem cells (ADSCs) have an anti-apoptotic effect on target cells and enhance the kidney function recovery. We will further investigate the use of ADSC in the prevention of kidney fibrosis in the unilateral UPJO model of Wistar rats.

MATERIAL AND METHODS

A total of twenty-two 12-week-old Wistar rats were divided into three groups. We made the UPJO models using nylon 6-0 inside the left ureter and tied the ureter with nylon 6-0, creating partial ureteral obstruction. The treatment group was then injected with 1.0 × 10⁶ cells of human ADSC via the tail vein of rats. All rats were euthanized after 2 and 4 weeks of treatment. The left kidney used hematoxylin-eosin for histopathological examination. Statistical analysis using one-way analysis of variance (ANOVA) was done with SPSS version 21.0.

RESULTS

TGF-β1 concentration in the treatment group was significantly lower in the 4^th week of observation (p4=0.0001), as well as collagen type 1, which was also significantly lower in the 4^th week (p4=0.0001). There was a significant difference in the glomerulus count between the control group and the human ADSC (hADSC) group therapy in week 2 and week 4 (p2=0.0001 and p4=0.026).

CONCLUSION

Administration of hADSC therapy reduces TGF-β1 and collagen type 1 levels and then improves the histopathological features in the process of renal fibrosis in the UPJO model.

Serum-Targeted HILIC-MS Metabolomics-Based Analysis in Infants with Ureteropelvic Junction Obstruction

Ureteropelvic junction obstruction (UPJO) constitutes the predominant cause of obstructive nephropathy in both neonates and infants. Fundamental questions regarding UPJO's mechanism, assessment, and treatment still remain unanswered. The aim of the present study was to elucidate potential differences through serum metabolic profiling of surgical cases of infants with UPJO compared to both nonsurgical cases and healthy age-matched controls. Early diagnosis of renal dysfunction in this cohort based on highlighted biomarkers was the ultimate goal. Thus, serum samples were collected from 20 patients preoperatively, 19 patients with mild stenosis treated conservatively, and 17 healthy controls. All samples were subjected to targeted metabolomics analysis by hydrophilic interaction liquid chromatography coupled to mass spectrometry (HILIC LC-MS/MS). Both univariate and multivariate statistical analyses were performed. Principal component analysis (PCA) and orthogonal partial least squares-discriminant analysis (OPLS-DA) score plots showed that the studied groups differed significantly, with a panel of metabolites, including creatinine, tryptophan, choline, and aspartate, distinguishing patients who required surgery from those followed by systematical monitoring as well as from healthy controls, showing high performance as indicators of UPJO disease.

Pathological changes in ureterovesical and ureteropelvic junction obstruction explained by fetal ureter histology

The etiology of ureterovesical junction obstruction (UVJO) and ureteropelvic junction obstruction (UPJO) is obscure with an adynamic narrow segment causing the obstruction. In this study, the authors compared interstitial cells of Cajal (ICC) and collagen-to-muscle ratio (CM ratio) between UVJO, UPJO, and fetal ureters to investigate whether a maturational arrest of the fetal ureter could explain both clinical pathologies.

METHODS

Group 1 (control) involved specimens of the normal ureter (nephrectomy for trauma/tumor; n = 20), while group 2, specimens of UVJO (n = 14); group 2 was further divided into group 2a, the dilated megaureter above UVJO, and group 2b, UVJO narrow segment; group 3, UPJO narrow segment excised during pyeloplasty (n = 31); and group 4, normal fetal ureters (n = 12). The specimens were analyzed for ICC using immunohistochemistry and CM ratio on Masson's trichrome (stains collagen in blue and muscle in red).

RESULTS

The median ICC/10 high-power field was 16.1 (8.3) in the normal and 17.3 (7.9) in the dilated segment of the megaureter, with no significant difference, but was significantly less in the narrow segment of UVJO at 4.5 (2.0), narrow segment of UPJO at 5.1 (2.3), and fetal ureter at 5.0 (2.3). The median CM ratio was 0.75 (0.29) in the normal and 0.65 (0.2) in the dilated segment of the megaureter, with no significant difference between them (figure), but was significantly higher in the narrow segment of UVJO at 3.0 (0.8), narrow segment of UPJO at 2.5 (0.71), and fetal ureter at 3.1 (0.61). Overall UVJO, UPJO, and fetal ureter segment had significantly less ICC density and more collagen compared with the normal ureter (P < 0.001 by Mann-Whitney U test).

DISCUSSION

There are conflicting reports on the etiopathogenesis of UVJO and UPJO, with several authors showing decreased ICC and increased collagen in the narrow segment. In this study, the authors found that the pathological changes at UVJ and UPJ segments resemble fetal ureter morphology. We also found that in fetal ureters, as the gestation progressed, there was an increase in the ICC density/smooth muscle, whereas the collagen content decreased. While the entire ureter has uniform embryological origin, it essentially remains an epithelial tube until the late gestation. The maturational process involves differentiation of smooth muscles cells/ICC to establish the peristaltic machinery required to functionally connect the ureter at both ends. This process, probably, starts at the mid ureter during fetal life and extends toward the UPJ and UVJ, and its failure, probably, results in UPJO or UVJO. The study's limitations are small numbers, and further larger studies are required to validate this hypothesis.