Endoscopic balloon dilatation in primary obstructive megaureter: Long-term results

Endoscopic Management of Adult Primary Obstructive Megaureter: Techniques and Long-term Outcomes

Background and objective

Few studies on endoscopic management of primary obstructive megaureter (POM) in adult patients have been reported. Our objective was to describe our technique and long-term outcomes for endoscopic management of adult POM.

Methods

We included 76 adult POM patients undergoing endoscopic management between September 2015 and January 2024. Under endoscopic control, the stricture was dilated to 24-30 Fr while maintaining a balloon pressure of 25-35 atm for 3 min. An additional incision of the stenotic ring using either an electrode or holmium laser was performed in 39 patients. Data for patient characteristics, intraoperative variables, surgical complications, and follow-up results were analyzed. A descriptive statistical analysis was performed. Surgical success was defined as no tubes or stents in the body, stable or improved symptoms and renal function, and the absence of reflux or obstruction during the follow-up period.

Key findings and limitations

All procedures were completed without conversion to open or laparoscopic surgery. The median operative time was 45 min (range 16-165) with median estimated blood loss of 2 ml (range 0-150). The median postoperative hospital stay was 3 d (range 1-15). No intraoperative complication occurred. At median postoperative follow-up of 42 mo (range 3-100) the overall success rate was 92.1%. Restenosis of the vesicoureteral junction (Clavien-Dindo grade III) occurred in five patients (6.6%), and high-grade vesicoureteral reflux occurred in one patient (1.3%), all of whom required secondary reconstruction surgery.

Conclusions and clinical implications

The results indicate that our endoscopic management for adult POM is safe and effective, with favorable long-term outcomes. This approach could potentially serve as a first-line treatment option for adult POM.

Patient summary

Primary obstructive megaureter (POM) occurs when the flow of urine is blocked because of a narrow segment in the tube between the kidney and bladder (ureter), which causes widening of the ureter further up. For our minimally invasive technique, a telescope is inserted through the urethra and bladder to reach the ureter for surgical treatment. Our results show that this is a safe procedure for POM in adults.

Advancements in Surgical Management of Megaureters

PURPOSE OF REVIEW

To review and describe the recent evolution of surgery for the various types of pediatric megaureter.

RECENT FINDINGS

Megaureter management first relies on determining the underlying cause, whether by obstruction, reflux, or a combination, and then setting appropriate surgical indications because many cases do not require surgery as shown by observation studies. Endoscopic balloon dilation has been on the rise as a major treatment option for obstructive megaureter, while refluxing megaureters can also be treated by laparoscopic and robotic techniques, whether extravesically or transvesicoscopically. During ureteral reimplantation, tapering is sometimes necessary to address the enlarged ureter, but there are also considerations for not tapering or for tapering alternatives. Endoscopic and minimally invasive surgeries for megaureter have been the predominant focus of recent megaureter literature. These techniques still need collaborative prospective studies to better define which surgeries are best for patients needing megaureter interventions.

Risk and protective factors for secondary procedures after endoscopic dilatation of primary obstructive megaureters

PURPOSE

High-pressure balloon dilatation (HPBD) of the ureterovesical junction with double-J stenting is a minimally invasive alternative to ureteral reimplantation or cutaneous ureterostomy for first-line surgical treatment of primary obstructive megaureter (POM). The aim of our study was to identify the risk factors associated with the need for secondary procedures due to HPBD failure.

METHODS

Prospective data were collected from patients who underwent HPBD for POM between 2007 and 2021 at a single institution. The collected data included patient demographics, diagnostic modalities, surgical details, results, and follow-up. Multivariate logistic regression analysis was performed.

RESULTS

Fifty-five ureters underwent HPBD for POM in 50 children, with a median age of 6.4 months (IQR: 4.5-13.8). Nineteen patients (37.25%) underwent secondary ureteric reimplantation, with a median of 9.8 months after primary HBPD (95% CI 6.2-9.9). The median follow-up was 29.4 months (IQR: 17.4-71). Independent risk factors for redo-surgery in a multivariate logistic regression model were: progressive ureterohydronephrosis (OR = 7.8; 95% CI 0.77-78.6) and early removal of the double-J stent. A risk reduction of 7% (95% CI 2.2%-11.4%) was observed per extra-day of catheter maintenance. The optimal cut-off point is 55 days, ROC curve area: 0.77 (95% CI 0.62-0.92). Gender, distal ureteral diameter, pelvis diameter, dilatation balloon diameter and preoperative differential renal function did not affect the need for reimplantation.

CONCLUSIONS

The use of a double-J stent for at least 55 days seems to avoid the need for a secondary procedure. Therefore, we recommend removing the double-J catheter at least 2 months after the HBPD.

Primary non-refluxing megaureter: Natural history, follow-up and treatment

Primary non-refluxing megaureter (PMU) is a congenital dilation of the ureter which is not related to vesicoureteral reflux, duplicated collecting systems, ureterocele, ectopic ureter, or posterior urethral valves and accounts for 5 to 10% of all prenatal hydronephrosis (HN) cases. The etiology is a dysfunction or stenosis of the distal ureter. Most often PMU remains asymptomatic with spontaneous resolution allowing for non-operative management. Nevertheless, in selective cases such as the development of febrile urinary tract infections, worsening of the ureteral dilatation, or reduction in relative renal function, surgery should be considered.

CONCLUSION

Ureteral replantation with excision of the dysfunctional ureteral segment and often ureteral tapering is the gold-standard procedure for PMU, although endoscopic treatment has been shown to have a fair success rate in many studies. In this review, we discuss the natural history, follow-up, and treatment of PMU.

WHAT IS KNOWN

• PMU is the result of an atonic or stenotic segment of the distal ureter, resulting in congenital dilation of the ureter, and is frequently diagnosed on routine antenatal ultrasound.

WHAT IS NEW

• Most often, PMU remains asymptomatic and clinically stable, allowing for non-operative management. • Nevertheless, since symptoms can appear even after years of observation, long-term ultrasound follow-up is recommended, even up to young adulthood, if hydroureteronephrosis persists. • Ureteral replantation is the gold standard in case surgery is needed. In selected cases, however, HPBD could be a reasonable alternative.

Spontaneous resolution and the role of endoscopic surgery in the treatment of primary obstructive megaureter: a review of the literature

The megaureter accounts for almost a quarter of all urinary tract dilations diagnosed in utero and is the second leading cause of hydronephrosis in newborns, following pyeloureteral junction obstruction. The current standard treatment for progressive or persistent, symptomatic primary obstructive megaureter is ureteral anti-reflux reimplantation, which can be associated with ureteral remodeling or plication. Due to the associated morbidity, postoperative recovery challenges, and the complications that may arise from the open surgical approach, there has been a natural inclination towards validating new minimally invasive techniques. This study reviews the literature, extracting data from three major international databases, from 1998 to 2022. Out of 1172 initially identified articles, only 52 were deemed eligible, analyzing 1764 patients and 1981 renal units. Results show that 65% of cases required surgical intervention, with minimally invasive techniques constituting 56% of these procedures. High-pressure endoscopic balloon dilation was the preferred endourologic technique. The degree of ureterohydronephrosis is considered one of the factors indicating the need for surgery. There is an inverse relationship between the diameter of the ureter and the likelihood of spontaneous resolution. Conditions such as renal hypoplasia, renal dysplasia, or ectopic ureteral insertion strongly indicate a poor prognosis. Endoscopic surgical techniques for treating primary obstructive megaureter can be definitive, firstline treatment options. In selected cases, they might be at least as effective and safe as the open approach, but with advantages like quicker recovery, fewer complications, shorter hospital stays, and reduced costs.

Endoscopic balloon dilation of primary obstructive megaureter: is fluoroscopic guidance necessary?

OBJECTIVE

To compare the long-term effectiveness, complications, and outcomes of primary obstructive megaureter (POM) treated by endoscopic balloon dilation under fluoroscopic guidance versus not using radioscopy during the procedure.

PATIENTS AND METHODS

A comparative study between POM cases treated at our institution by endoscopic balloon dilation (EBD) under fluoroscopic guidance (FG) (n = 43) vs no fluoroscopic guidance (NFG) (n = 48) between the years 2004 and 2018 was conducted. The procedure in FG consisted of performing a retrograde pyelography before dilation. Then, a guidewire is introduced to the renal pelvis, and the dilation of the vesicoureteral junction is performed using high-pressure balloon catheters under fluoroscopic vision. Finally, a double-J stent is placed between the renal pelvis and bladder. The procedure in NFG was performed exclusively under cystoscopic vision without radiological exposure. Complications, outcomes, and success rates were analyzed using Spearman's correlation test. Mean follow-up was 12.5 ± 2.2 years in FG and 6.4 ± 1.3 years in NFG.

RESULTS

MAG-3 showed significant differences in renal drainage before and after endoscopic treatment in both groups (p < 0.001 T-test). Statistical analysis did not reveal differences between groups in initial technical failure (r: - 0.035, p = 0.74), early postoperative complications (r: - 0.029, p = 0.79), secondary VUR (r: 0.033, p = 0.76), re-stenosis (r: 0.022, p = 0.84), long-term ureteral reimplantation (r: 0.065, p = 0.55), and final outcome (r: - 0.054, p = 0.61). The endoscopic approach of POM had a long-term success rate of 86.5% in FG VS 89.6% in NFG.

CONCLUSIONS

Endoscopic balloon dilation of POM can be done with no radiation exposure with similar results, effectiveness, and outcomes.

High-pressure balloon dilatation of primary obstructive megaureter in children: a systematic review

OBJECTIVE

We aimed to evaluate the effectiveness and complication rates of endoscopic high-pressure balloon dilatation (HPBD) in treating primary obstructive megaureter (POM) in children based on current literature. Specifically, we wanted to clarify the evidence on the use of HPBD in children under one year of age.

METHODS

A systematic search of the literature was performed via several databases. The preferred reporting items for systematic reviews and meta-analyses guidelines were followed. The primary outcomes studied in this systematic review were the effectiveness of HBPD in relieving obstruction and reducing hydroureteronephrosis in children. The secondary outcome was to study the complication rate of endoscopic high-pressure balloon dilatation. Studies that reported one or both of these outcomes (n = 13) were considered eligible for inclusion in this review.

RESULTS

HPBD significantly decreased both ureteral diameter (15.8 mm [range 2-30] to 8.0 mm [0-30], p = 0.00009) and anteroposterior diameter of renal pelvis (16.7 mm [0-46] to 9.7 mm [0-36], p = 0.00107). The success rate was 71% after one HPBD and 79% after two HPBD. The median follow-up time was 3.6 years (interquartile range 2.2-6.4 years). A complication rate of 33% was observed, but no Clavien-Dindo grade IV-V complications were reported. Postoperative infections and VUR were detected in 12% and 7.8% of cases, respectively. For children under one year of age, outcomes of HPBD seem to be similar to those in older children.

CONCLUSIONS

This study indicates that HPBD appears to be safe and can be used as the first-line treatment for symptomatic POM. Further comparative studies are needed addressing the effect of treatment in infants, and also long-term outcomes of the treatment. Due to the nature of POM, identifying those patients who will benefit from HPBD remains challenging.

Endoscopic balloon dilatation for the treatment of primary obstructive megaureter <24 months of age: Does the size of the balloon influence results?

INTRODUCTION

Endoscopic balloon dilatation (EBD) can be performed with different catheters and its durability is still controversial. This study aimed to compare long-term results of EBD performed <24 months of age using balloons of 4 mm vs. 6 mm in diameter.

MATERIALS AND METHODS

Retrospective study of consecutive patients with unilateral primary obstructive megaureter (POM) undergoing EBD <24 months of age by two surgeons from 01/2009 to 12/2020. The technique was consistent, but for balloon diameter, which was 4 mm in group A vs. 6 mm in group B. End-points included peri-operative complications, success rate (improving dilatation and non-obstructive drainage on 9-month scintigraphy), and long-term outcome (need for reimplantation and diameter of retrovesical ureter at last ultrasound).

RESULTS

The procedure was completed in all planned patient. Group A included 15 patients and Group B 30 patients. Groups were not significantly different for age (p < 0.09), gender (p < 0.1), laterality (p < 0.7), and preoperative median ureteral diameter (p = 0.08). No perioperative complications occurred. Four group A patients required a cutting balloon to achieve a satisfactory dilatation of the vesicoureteral junction (p = 0.009). After a median (range) follow-up of 70 (19-155) months, success rate was 73.3% vs. 83.3% (p = 0.45), 4/15 group A and 5/30 group B patients required reimplantation within 2 years of EBD. In successful cases, median (range) ureteral diameter at last follow-up was 6 (0-17) mm vs. 5 (0-14) mm, which was significantly better than preoperative value (p = 0.003 and p < 0.001, respectively), but not significantly different (p = 0.8) between groups.

DISCUSSION

EBD is an umbrella term that encompasses many technical variations, which can be key for success. Although limited by the small numbers and the comparison of patients treated over two subsequent periods, this is the first study focusing on the role of balloon size.

CONCLUSIONS

The diameter of the balloon did not influence significantly long-term results, but the 6 mm balloon slightly increased the success rate of EBD to 83.3% and eliminated the need for cutting balloons to achieve a satisfactory dilatation.

Ureteral reimplantation for pediatric vesicoureteral reflux and primary obstructive megaureter: Transvesicoscopic cohen vs. Politano-Leadbetter approaches

BACKGROUND

Transvesicoscopic approaches for ureteral reimplantation (UR) are effective surgical techniques with which to resolve vesicoureteral reflux (VUR) or primary obstructive megaureter (POM) in pediatric patients. However, the effectiveness of different UR surgical methods for these two diseases is still unclear.

PURPOSE

To compare the effects of Cohen's cross-trigonal and Politano-Leadbetter techniques in children in need of UR.

METHODS

A retrospective chart review was performed for consecutive patients who underwent UR at our institution between May 2018 and November 2019, including those treated for vesicoureteral reflux (VUR) or primary obstructive megaureter (POM). Patients who underwent Cohen's technique included in Group C, and those who underwent the Politano-Leadbetter technique were included in Group P. Patient characteristics, perioperative parameters, and short-term postoperative outcomes were compared.

RESULTS

Forty-six patients who underwent unilateral UR were included in the analysis. At presentation, those in Group P (N = 22, 12 diagnosed with VUR and 10 with POM) did not differ from those in Group C (N = 24, 12 diagnosed with VUR and 12 with POM) with respect to age, sex, disease type or severity. For VUR patients, reflux was clinically resolved for all patients in both groups; however, only a 75% resolution rate was observed in Group C, with 3 patients experiencing persistent low-grade, clinically insignificant reflux, while a 100% resolution rate was found in Group P (P > 0.05). Among POM patients, the obstruction was resolved for all those in Group P and for 90% of those in Group C; this difference was also not statistically significant (P > 0.05). At the 1-year follow-up, the ureteral diameter (P < 0.05) and anterior-posterior renal pelvic diameter (APRPD) (P < 0.05) of Group P were significantly reduced, and differential renal function (DRF) (P < 0.05) was slightly improved compared with that in Group C in both VUR and POM patients.

CONCLUSIONS

Politano-Leadbetter and Cohen are both reliable techniques for UR in children with VUR or POM, and the short-term outcomes of these methods in solving reflux and obstruction are comparable. Besides traditional Cohen's technique, Politano-Leadbetter's technique maybe a potential choice for ureteral reimplantation in children.

Postoperative JJ stent is not necessary after balloon high-pressure endoscopic dilatation of primary obstructive megaureter

INTRODUCTION

A wide range of surgical interventions have been described for the management of primary obstructive megaureter (POM). Endoscopic balloon dilatation has been developed through last decades as a minimally invasive alternative to classic surgery.

OBJECTIVE

To assess the need for placement of a double J stent after endoscopic balloon dilatation procedure, by comparing the post-operative related outcomes with and without double J placement. Secondary outcome was the success rate, considering the need for further procedure after endoscopic balloon dilatation and the improvement of the ureteral diameter in the two groups.

STUDY DESIGN

Historical retrospective comparison of children treated by endoscopic dilatation for POM, with post-operative JJ stent left in place (2012-2014) or without ureteral JJ stent (since 2015). Post-operative complications were reported following Clavien-Dindo grading system and compared between the two groups. Success rate was defined as absence of need for further surgical reimplantation. Ureteral diameters on preoperative and postoperative renal ultrasounds were compared.

RESULTS

Endoscopic dilatations were performed in 42 patients for 46 renal units during the study period. There was a significantly higher rate of post-operative complications in the group with JJ stenting compared to the group without double J stenting regarding all Clavien-Dindo grades (56% vs 15%, p = 0.014) and Clavien-Dindo grade III only (31% vs 0%, p = 0,0051) (Figure). The success rate was similar in the JJ group (75%, F-up: 70 months [13-101]) and the no JJ group (81%, F-up: 26 months [12-95]). There was a significant improvement of US renal pelvis and ureter dilatation in both groups, with a median follow-up of 35.5 months [12-101].

DISCUSSION

The overall rate of complications was slightly higher than in other reports and higher in the JJ group regarding Clavien-Dindo grade III complications. The success rate was comparable to previous studies reviewing endoscopic dilatations and equivalent in the two groups.

CONCLUSION

In our study, the omission of postoperative ureteral drainage by a JJ stent after endoscopic balloon dilatation of POM did not increase post-operative complications rate without demonstrable impact on the success rate.

Telocytes, c-Kit positive cells, Smooth muscles, and collagen in the ureter of pediatric patients with congenital primary obstructive megaureter: elucidation of etiopathology

Congenital primary obstructive megaureter (POM) is an uncommon pediatric anomaly that is due to obstructive distal ureter leading to the loss of peristalsis with consequent ureterohydronephrosis causing loss of kidney function. The objectives are to elucidate the etiology of POM by demonstrating the presence of interstitial cells of Cajal (ICC), telocytes, smooth muscles, and collage in the obstructive and dilated ureteral segments. The study was carried out on 15 surgical specimens of congenital POM in pediatric patients, age range was 4 to 24 months, they were operated upon by excision of the obstructed segment, tailoring the dilated ureter, and anastomosing it to the bladder. Specimens included the obstructed ureteral segment and part of the dilated ureter. Specimens were examined with hematoxylin and eosin (H&E) stain, Modified Gomori trichrome stain, immunohistochemistry (IHC) with α-muscle actin, and c-kit (CD117), and transmission electron microscopy (TEM). Obstructed segment showed excess collagen intervening between smooth muscles, excess c-Kit positive cells, and presence of telocytes. The dilated segment of the ureteral wall is formed of smooth muscle bundles with scanty collagen. Staining with c-Kit did not demonstrate positive cells. TEM showed myofibroblasts and close adherence of smooth muscle cells to each other with absence of telocytes. The pathophysiology of POM is multifactorial. Loss of interstitial cells and rarity of collagen result in loss of elasticity of dilated segment leading to massive dilatation. While the obstructed segment had no muscle conductivity due to excess collagen irrespective of presence of telocytes.

High-pressure balloon dilatation in children: our results in 30 patients with POM and the implications of the cystoscopic evaluation

Primary Obstructive Megaureter (POM) is a common cause of hydronephrosis in children with spontaneous resolution in most cases. High-Pressure Balloon Dilatation (HPBD) has been proposed as a minimally invasive procedure for POM correction in selected patients. The aim of the paper is to review our experience with HPBD in patients with POM. We performed a retrospective study in a single Centre collecting data on patients' demographics, diagnostic modalities, surgical details, results and follow-up. In particular, the endoscopic aspect of the orifice permitted the identification of 3 patterns: adynamic ureteral segment, stenotic ureteric ring and pseudoureterocelic orifice. We performed HPBD in 30 patients over 6 years. We had 23 patients with adynamic distal ureteral segment (type 1), 4 with stenotic ring (type 2) and 3 with ureterocelic orifice (type 3). In 3 patients (10%) the guidewire did not easily pass into the ureter requiring ureteral stenting or papillotomy. Post-operative course was uneventful. Five patients (3 pseudoureterocelic) required open surgery during follow-up. HPBD for the treatment of POM is a safe and feasible procedure and it can be a definitive treatment of POM. Complications are mainly due to double J stent and none of our patients had symptoms related to vescico-ureteral reflux. The aspect of the orifice, identified during cystoscopy, seems to correlate with the efficacy of the dilatation: type 1 and 2 are associated with good and excellent results respectively; type 3 do not permit dilatation in almost all cases requiring papillotomy. HPBD can be performed in selected patients of all paediatric ages as first therapeutic line. The presence of a pseudoureterocelic orifice or long stenosis might interfere with the ureteral stenting and seems associated with worse outcomes.

Management of Primary Obstructive Megaureter by Endoscopic High-Pressure Balloon Dilatation. IDEAL Framework Model as a New Tool for Systematic Review

Introduction: Therapeutic management of primary obstructive megaureter (POM) requiring surgery has been under debate for the last 15 years especially regarding the outcomes of endoscopic techniques compared to most traditional approaches. This review aims to analyze endoscopic High-Pressure Balloon Dilatation (HPBD) using the IDEAL model, a five-stage framework that describes surgical innovations (Idea, Development, Exploration, Assessment, and Long-term Study) and provides recommendations for a rigorous stepwise surgical research pathway. This model has been developed and demonstrated its value in evaluating surgical innovations assessing data quality and providing relevant information for the optimal design and feasibility of research in surgery. Materials and Methods: A systematic review of the published series of endoscopic HPBD in patients with POM was done using the IDEAL model as a tool to assess evidence quality. Reported clinical outcomes are also analyzed and reviewed. Results: The analysis of the results of the systematic assessment of the reported cohort of patients treated with HPBD for POM that the technique up to date is in stage 2a and stage 2b, or development. Evidence quality among the reported cohorts of patients with POM treated with HPBD is adequate, although systematization and standardization should be improved. Clinical outcomes of HPBD in the management of POM consistently show a 87.7% success rate with a negligible operative complication rate once "learning curve" has been surpassed. Symptomatic vesicoureteral reflux (VUR) is the main reason for ureteric reimplantation, but asymptomatic VUR does not seem to influence clinical outcome. Conclusions: The IDEAL framework and recommendations have allowed a systematic analysis of the evidence quality of the reported experience in the management of children with POM with HPBD of the vesicoureteral junction. The available evidence demonstrates that HPBD is an effective treatment for patients with POM, with a long-term success rate of 87.7% with very low morbidity. Future research mandates a standardization of data reporting, "ideally" following IDEAL recommendations, that would be required for any intervention and facilitate comparative analysis.

Long-Term Outcomes in Primary Obstructive Megaureter Treated by Endoscopic Balloon Dilation. Experience After 100 Cases

Aim: To assess long-term effectiveness, complications, and outcomes of primary obstructive megaureter (POM) treated by endoscopic balloon dilation (EBD) in the largest series reported. Patients and Methods: Hundred POM in 92 consecutive patients were treated by EBD between years 2004 and 2016. A total of 79 POM (73 patients) with more than 18 months of follow-up after treatment have been analyzed. EBD of the vesicoureteral junction was performed with semicompliant high-pressure balloon catheters (2.7FG) with minimum balloon diameter of 5 mm, followed by temporary Double-J stent placement. Follow-up protocol included periodical clinical reviews, US and MAG-3 renogram scans. Results: Median age at surgery was 4 months (15 days-3.6 years), with median operating time of 20 min (10-60) and hospital stay of 1 day (1-7). Initial renal function was preserved in all patients with significant improvement in renal drainage on the MAG-3 diuretic renogram after endoscopic treatment (p < 0.001 T-test). Significant post-operative differences were observed in hydronephrosis grade and ureteral diameter that were maintained in the long-term (p < 0.001 T-test). Endoscopic approach of POM had a long-term success rate of 87.3%, with a mean follow-up of 6.4 ± 3.8 years. Secondary VUR was found in 17 cases (21.5%), being successfully treated by endoscopic subureteral injection in 13 (76.4%). Nine cases developed long-term re-stenosis (12.2%) that were successfully treated with a new EBD in 8. Endoscopic management of POM failed in 10 cases (12.7%) that required ureteral reimplantation. Five were early failures (4 intraoperative technical problems and 1 double-J stent migration with severe re-stenosis), and 5 long-term (4 persistent VUR and 1 re-stenosis recurrence). Conclusion: EBD has shown to be an effective treatment of POM with few complications and good outcomes at long-term follow up. Main complication was secondary VUR that could also be treated endoscopically with a high success rate. In our opinion, EBD may be considered first-line treatment in POM.

High Pressure Balloon Dilatation of Primary Obstructive Megaureter in Children: A Multicenter Study

Aim of the Study: We described the initial experience of four referral centers in the treatment of primary obstructive megaureter (POM) in children, by high-pressure balloon dilatation (HPBD) of the ureterovesical junction with double JJ stenting. We managed a retrospective multicenter study to assess its effectiveness in long-term. Methods: We reviewed the medical records of all children who underwent HPBD for POM that require surgical treatment from May 2012 to December 2017 in four different institutions. The primary outcome measured was ureterohydronephrosis (UHN) and its degree of improvement after the procedure. Secondary outcomes were postoperative complications and resolution of preoperative symptomatology. Main Results: Forty-two ureters underwent HPBD for POM in 33 children, with a median age of 14.7 months - (range: 3 months -15 years). Ureterohydronephrosis improves in 86% of ureters after one endoscopic treatment. Three cases required a second HPBD. Four patients required surgical treatment for worsening of UHN after endoscopic treatment. The post-operative complication rate was 50% (21 ureters). In 13 cases (61%), they were related to double J stent. The median follow-up was 24 months (2 months -5 years) and all patients were symptom-free. Conclusion: We reported the first multicenter study and the largest series of children treated with HPBD, with an overall success rate of 92%. Endoscopic treatment can be a definitive treatment of POM since it avoided reimplantation in 90% of cases. Complications are mainly due to double J stent.