Management Of Primary Obstructive Megaureter Research Articles

IS THERE A CONSENSUS ON THE MANAGEMENT OF PRIMARY OBSTRUCTIVE MEGAURETER?

To analyze the results of a survey regarding the opinion of experts in diagnosis and management of primary obstructive megaureter (POM) and to determine if their current therapeutic strategy matches with the BAPU recommendations, published in 2014. From 1 February to 30th June 2023, an online-based survey was distributed through the eUROGEN network and some pediatric urology societies. The questionnaire was carried out using google forms and consisted of 14 questions. Additionally, a literature review of the most recent articles was performed. 103 medical professionals completed the survey, 98 (96.1%) were pediatric urologists. 67.3% of respondents agreed with starting continuous antibiotic prophylaxis (CAP) in all patients with POM. The diagnosis of obstruction is mostly made based on a combination of findings which include initial DRF <40%, drop of DRF of > 5% on serial scans and worsening of dilation at follow-up ultrasound (63.7%). When specifically asked if initial DRF < 40% as a solely finding without symptoms or massive dilatation was considered as an indication for early surgery, only 12 (11.9%) considered it so. Regarding ureteral reimplantation (UR) under the age of 1, 46 (45.1%) were confident in this procedure. Among temporizing interventions, high-pressure endoscopic balloon dilatation (HPBD) was the most popular. Current trends in the diagnosis and management of POM may challenge some of the BAPU recommendations, especially in regards initial DRF < 40% as a solely indication of surgery and the most popular temporizing procedures. It may be time to elaborate a new updated consensus and decide a common updated approach for all patients with POM.

Endoscopic balloon dilatation of primary obstructive megaureter: An effective first line management in children

This study evaluates outcomes of endoscopic balloon dilatation (EBD) in the management of primary obstructive megaureter (POM) in children. Retrospective data between 2013 and 2023 from two tertiary paediatric surgical centres in the UK were reviewed. Pre and post-operative clinical and imaging parameters of children managed with EBD were assessed. Failure of procedure was defined as requiring further intervention due to persistent/recurrent symptoms, upper tract dilatation and/or obstruction on MAG3 over the follow up period. 55 children with 61 renal units were evaluated. Median age at treatment was 18 months with a median follow up of 24 months. There was significant reduction in upper tract ultrasound measurements following balloon dilatation but there was no significant difference between the pre and post-operative renal function on MAG3. No significance difference was demonstrated when the outcomes of cutting and non-cutting balloons were compared. No significant difference was shown when outcomes after EBD were compared between infants vs older children as well as ureteric dilatation less than or over 25mm (p=0.841). 87% were successfully treated with a single dilatation and this increased to 95% after second dilatation. The remaining 5% had ureteric re-implantation. Although a retrospective study, the patient population is relatively large. 87% success rate shown after EBD is comparable to similar studies. It has been suggested that children less than 12months and those with severe ureteric dilatation (>25mm) may not be suitable for EBD. No significant difference was demonstrated when the outcomes of these categories of children were compared to other children with POM. All of the patients that had repeat balloon dilatation required no further intervention, a finding that has so far not been well evaluated in available literature. This study demonstrates 87% success rate after single EBD in children with POM and this outcome increased to 95% following a second dilatation. EBD is shown to be an effective definitive surgical management option of POM. It can be safely offered as first line management in all patient groups and repeated if no initial response.

Endourological treatment of upper tract urinary disease in children

With advances in therapeutic interventions, endourology has become standard of care for the treatment of numerous diseases in the field of pediatric urology. However, there remains a lack of agreement and evidence on the optimal approaches and associated complications of endourological treatment of upper urinary tract conditions in children, namely ureteropelvic junction (UPJ) obstruction, primary obstructive megaureter, and nephrolithiasis. While pyeloplasty remains the first-line surgical treatment for pediatric UPJ obstruction, endoscopic retrograde balloon dilatation (ERBD) and endopyelotomy continue to gain traction as less invasive means of treating obstruction, particularly for failed repairs. Studies report success rates ranging from 76–100% although re-stenosis or need for revision surgery is not uncommon. Endourological options for the surgical management of primary obstructive megaureter include ERBD or endoureterotomy, rather than the open option of ureteroneocystotomy with or without tapering. Both have shown long-term success rates ranging from 70–90%, however, there is emerging evidence that these therapies may be associated with a risk of postoperative vesicoureteral reflux. Meanwhile, for stone disease, shock wave lithotripsy (SWL), flexible ureteroscopy (URS), and percutaneous nephrolithotomy (PCNL) are mainstays in the pediatric urologist’s armamentarium. Studies have shown that URS and PCNL have comparable stone-free rates, although PCNL can be associated with increased morbidity. Advancements in technology have led to the use of smaller access sheaths without compromising stone-free rates or increasing long-term complications. The use of mini-PCNL in the adult population holds great potential for use in our pediatric patients. The rise of endourology expertise and improved technology makes it an attractive option that could even be considered as a first-line option for the treatment of various urinary tract conditions. Nevertheless, there is a paucity of evidence on outcomes and complications following its use for treatment of upper urinary tract diseases in children. This review aims to summarize and present results of endourological treatments for pediatric UPJ obstruction, primary obstructive megaureter, and nephrolithiasis, as well as highlight advancements in the field of endourology that may increase its utilization in pediatric urology in the future.

Laparoscopic nipple invagination combined extravesical (NICE) reimplantation technique in the management of primary obstructed megaureter

Villanueva challenged Paquin's 5:1 tunnel length and showed in a computer simulation model that UVJ competence was more sensitive to a 2-mm protrusion of ureteric orifice into the bladder compared to an increase in the intravesical tunnel. Thompson later successfully applied the Shanfield technique of invaginating the spatulated primary obstructed megaureter (POM) laparoscopically, causing a nipple antireflux mechanism. In this study we have reported the outcomes of our modification: Nipple Invagination Combined Extravesical (NICE) reimplantation, in the management of POM. Patients with POM who underwent NICE reimplantation (summary figure) were followed up and outcomes were analysed. There were three modifications in this compared to Shanfield technique: 1. Detrusor myotomy was performed before opening the bladder mucosa. The detrusor edges were closed later over the invaginated ureter as an extravesical reimplantation. 2. The ureter was held invaginated inside the bladder mucosal opening by two sutures at 6 & 12 O' clock positions instead of a single suture, 3. The dilated ureter was not spatulated inferiorly, as it automatically opens out later inside the bladder to form a nipple. Eleven patients underwent laparoscopic NICE reimplantation; median age: 6 months (5-24); demographics (R: L=5:6; M:F=7:4). The mean duration of surgery was 133min (110-180) and the mean length of hospital stay was 3.6 days (3-5). There were no immediate post-operative complications in the form of leak in any patient. The median follow-up duration was 20 months (18-29). DRF improved in 7 patients while in 4 it remained static; no patient had deterioration. On follow-up VCUG, none had vesico-ureteric reflux (VUR). The nipple effect could be noticed later at follow-up ultrasonograms and at cystoscopy during stent removal. Paquin emphasised on 5:1 ureteral re-implant tunnel length while Lyon felt that the shape of the ureteral orifice was more important. Shanfield introduced a technique of creating a nipple valve effect by invaginating the ureter intravesically. However it was held by a single suture and had no detrusor backing. NICE reimpantation incorporates a short extra vesical reimplant to the Shanfield technique and literally eliminates post-operative VUR. It is simple and could easily be performed laparoscopically even in small infant bladders. The ureteric orifice kept in line enables future upper-tract access. Our preliminary data suggests that the NICE reimplantation for POM is very successful. Limitations are small numbers and short follow-up. Further larger studies are warranted to authenticate this novel technique.

High pressure baloon dilatation (HPBD) vs cutting balloon ureterotomy (CBU) in the management of primary obstructive megaureter (POM)

High pressure baloon dilatation (HPBD) vs cutting balloon ureterotomy (CBU) in the management of primary obstructive megaureter (POM)

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

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. 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. 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. 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]. 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. 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.

Utilization of Robot-assisted Surgery for the Treatment of Primary Obstructed Megaureters in Children

To describe the technical aspects of robot assisted laparoscopic ureteral reimplantation (RALUR) for the management of primary obstructive megaureter (POM) and report initial outcomes, safety, and feasibility of the procedure. Using an IRB- approved robotic surgery registry, we performed a retrospective chart review of patients undergoing RALUR for POM between April 2009 and May 2019. A total of 18 patients underwent RALUR using a modified Lich-Gregoir technique for management of POM and 7 (38.9%) of these underwent intracorporeal ureteral tapering at the time of surgery. At median follow up of 27.5 (IQR 11-50) months, no patient required reoperation for recurrent obstruction and all patients had improvement in hydronephrosis postoperatively. 30-day complications were low with 1 Grade I, 2 Grade II and 1 Grade III Clavien-Dindo complication. The most common issue postoperatively was febrile urinary tract infection, occurring in 6 patients (33.3%), at an average of 3.2 months after surgery. Increased operative time was the only significant difference between the tapered verses nontapered group. We present the largest series of RALUR for POM to date. Based upon our initial experience with this technique we believe it is technically feasible and reproducible with good outcomes and low complication rates. Future studies are needed to track long-term outcomes and better understand indications for and the utility of ureteral tapering as well as how to minimize febrile UTIs postoperatively. Additional follow up is needed to determine the efficacy of RALUR as compared to open ureteral reimplantation for POM.

Laparoscopic Extravesical Reimplantation in Children with Primary Obstructive Megaureter.

Introduction: Conservative management of primary obstructive megaureter (POM) appears as the best option in patients with adequate ureteral drainage. Nevertheless, surgical intervention is indicated in cases of recurrent urinary tract Infections (UTIs), deterioration of split renal function, and significant obstruction. The gold standard includes: Ureteral reimplantation with or without tapering by open approach. Our objective is to report our results in the treatment of POM by Laparoscopic-Assisted Extracorporeal Ureteral Tapering Repair (EUTR) and Laparoscopic Ureteral Extravesical Reimplantation (LUER) and to evaluate the efficacy and security of this procedure. Materials and Methods: From January 2011 to January 2018 a retrospective study was carried out by reviewing the clinical records of 26 patients diagnosed with POM. All patients underwent laparoscopic ureteral reimplantation following Lich Gregoir technique. In cases of ureteral tapering, an EUTR was performed with Hendren technique. Results: In all patients LUER and EUTR were performed without conversion. No ureteral tapering was necessary in six patients. There were no intraoperative complications. At 3 months in postoperative, 1 patient presented a febrile UTI, and subsequently, a vesicoureteral reflux (VUR) grade III was diagnosed by voiding cystourethrogram. In this case, a redo laparoscopic surgery was performed. After long-term follow-up, all patients were asymptomatic without recurrence of POM or VUR. Conclusion: Laparoscopic-assisted EUTR and LUER following Lich Gregoir technique for POM constitutes a safe and effective option, with a success rate similar to that of open procedure. Nevertheless, larger randomized prospective trials and long-term follow-up are required to validate this technique.

Endoscopic management of primary obstructed megaureter: Is it justified? Literature review

Endoscopic management of primary obstructed megaureter: Is it justified? Literature review

Endoscopic Management of Primary Obstructive Megaureter: A Systematic Review.

The gold standard treatment for primary obstructive megaureter (POM) with declining renal function, worsening obstruction, or recurrent infections is ureteral reimplantation with or without tapering. In infants, open surgery can be technically demanding and associated with significant morbidity. We conducted a systematic review of the literature with special interest in endoscopic management of POM and its outcomes. A search was conducted of the MEDLINE/Ovid, PubMed, Embase, and Web of Science databases. Only full-text articles written in the English language and involving greater than one reported pediatric case per publication were included. Two authors independently extracted data and assessed strength of evidence for each study. We found 11 retrospective and 1 prospective, single institution case series that met selection criteria, describing 222 patients with 237 obstructed renal units. Mean age at time of surgery was 24.6 months. The most common endoscopic approaches were cystoscopy+high-pressure balloon dilation+Double-J ureteral stent placement (49.5%), cystoscopy+incisional ureterotomy+Double-J ureteral stent placement (27.8%), and cystoscopy+Double-J ureteral stent placement (18.9%). For all approaches and age groups, anatomic and functional success rates were 79.3% (146/184) and 76.7% (132/172), respectively. Anatomic success rates were highest in children ≥12 months of age (82.3%, 117/142). Endoscopic retreatment was performed in 15.1% of cases with a 36.7% overall surgical reintervention rate. Forty-one ureters progressed to ureteral reimplantation. Complications were generally mild (Clavien-Dindo Grades I-II), but 12 ureters did develop vesicoureteral reflux. Mean follow-up period was 3.2 years. Endoscopic management for persistent or progressive POM in children ≥12 months of age is a minimally invasive alternative to ureteral reimplantation with modest success rates. In infants, it may best be utilized as a temporizing procedure. Approximately one-third of patients require surgical reintervention.

Urolithiasis secondary to primary obstructive megaureter in an adult: a case report

BackgroundPrimary obstructive megaureter is relatively uncommon in adults. This condition usually regresses spontaneously or is treated during infancy. It can remain asymptomatic for decades until adulthood when symptoms may manifest in the event of complications or during a routine radiologic imaging. Primary obstructive megaureter has been reported to favor stone formation in the upper urinary tract.Case presentationWe present the case of a 35-year-old Moroccan man who had a 10-year history of intermittent left flank pain and hematuria. A computed tomography urogram revealed a left megaureter with giant ureteral and renal calculi.ConclusionsPrimary obstructive megaureter should be a differential diagnosis in an adult with hydroureteronephrosis associated with urolithiasis especially when there is kidney impairment. Through this case report we will discuss the diagnosis and management of primary obstructive megaureter associated with urolithiasis in adults.

741 - The megasurvey: International survey on the current practices in surgical management of primary obstructed megaureter

741 - The megasurvey: International survey on the current practices in surgical management of primary obstructed megaureter

Three-Dimensional Laparoscopic Management of Primary Obstructive Megaureter

Abstract Introduction and Objective: Megaureter (MGU) is a disease including variable anomalies. It may be caused by either a primary cause or secondary to specific pathologic origin. The cause of primary obstructive MGU typically is an aperistaltic juxtavesical segment 2 or 3 cm long that is unable to propagate urine at acceptable rates of flow. The result of lower ureteral obstruction can lead to renal failure due to silent obstruction of the ureter and can be complicated by potential loss of renal function. We present a video demonstration of three-dimensional (3D) laparoscopic management of primary obstructive megaureter. Materials and Methods: Case 1: A 7-year-old male with h/o right dull loin pain and recurrent urinary-tract infection (UTI) on and off for 1 year. Imaging protocol included ultrasound (USG), micturating cystourethrogram, and MRI, which revealed grossly dilated tortuous ureter with obstruction at the right vesicouretral junction (VUJ). Laparoscopic tailored reimplantation was performed...

‘Mini reimplantation’ for the management of primary obstructed megaureter

The management of primary obstructed megaureter (POM) ranges from temporary double-J stenting to conventional ureteric reimplantation with tapering. Of late, several authors have favored refluxing reimplantation. In the present study the outcomes of 'mini reimplantation', where no tapering or advancement of the ureter was performed, have been analyzed. Records of all children (n = 28) who underwent reimplantation for POM from 2004 to 2014 were retrospectively analyzed. During the initial 5 years, a Cohen's reimplantation with excisional tapering was performed (Group 1, n = 15). Due to complications, the technique was modified in the second 5 years (Group 2, n = 13). In this group, after opening the bladder, the distal narrow segment and grossly dilated POM (around 3-5 cm) were excised (Figure). After closing the detrusor behind the ureter, the ureter was reimplanted again at the original position without tapering or advancement. Bladder mucosa was closed cranial to the new ureteric orifice, providing a ureter:tunnel ratio of 1:2 (mini reimplantation). All patients underwent repeat ultrasonogram and MAG3 renogram, with indirect at 6 months and 1 year after stent removal to exclude obstruction/vesicoureteral reflux (VUR). In Group 1, a significantly higher proportion (P = 0.04) of patients (5/15) had to undergo repeat procedures for complications, compared with none in Group 2. In Group 1, there were two redo reimplants for recurrent obstructions; two nephrectomies for non-functioning kidneys; and one ureterostomy for pyonephrosis. Postoperative Grade 2-3 VUR was encountered in 3/15 patients in Group 1, and 2/13 patients in Group 2. These patients could be managed with antibiotic prophylaxis and no intervention was required. Conventional management of POM involved initial cutaneous ureterostomy, followed by reimplantation with tapering of the ureter. Megaureter reimplantation with and without tapering has been reported to have no significant difference in outcomes between them. To avoid a potentially difficult operation in a small infant bladder, a refluxing reimplantation has been proposed; however, there is a high re-operation rate following this technique. The author feels that the reported technique is superior to the refluxing reimplantation, as there is no need for re-operation. The limitations of this study were the small numbers and short follow-up. However, the proposed 'mini reimplantation' with no tapering or advancement had good success rates in this small series. Further larger studies are required to support or negate the usefulness of this technique.

Primary Obstructive Megaureter in Infants: Our Experience with Endoscopic Balloon Dilation and Cutting Balloon Ureterotomy

The management of primary obstructive megaureter (POM) is usually conservative, at least in the first year of life. Nevertheless, in high-grade POMs with increasing dilation, obstructive patterns found at renography, or cases involving decreased renal function, there is a clear indication for surgery. From January 2009 to March 2013, 12 patients, aged 6 to 12 months (mean 8 months), were treated endoscopically for POM. At the procedure, a clear stenotic ring was identified in 10 of the 12 patients, and a simple endoscopic high-pressure balloon dilation (EHPBD) was well performed in 7 patients. In the three cases with persistent ring, a cutting balloon ureterotomy (CBU) was then performed, resulting in the immediate and complete disappearance of the stenosis. In two cases, no ring could be seen at the procedure, and they showed no improvement at the follow-up. The mean follow-up was 21 months. Considering the whole series of patients treated endoscopically, the overall success rate of EHPBD+CBU was 83%. Patients with POM can be treated endoscopically. In the case of a persistent ring that is unresponsive to EHPBD, CBU seems to provide a valid definitive treatment of POM.

Result of Endoureterotomy in the Management of Primary Obstructive Megaureter in the First Year of Life: Preliminary Report

The present study aimed to investigate the efficacy of endoureterotomy in patients who were less than 1-year-old with primary obstructive megaureter (POMU). Three of 10 patients with POMU aged between 2 and 12 months for whom conservative management was not applicable had recurrent urinary tract infection (UTI) and urosepsis, while the rest had decreased renal function. After obtaining the clinical history and performing physical examinations and imaging studies (ultrasonography, voiding cystourethrography (VCUG), radionuclide renal scan), the patients underwent endoureterotomy using a neonatal ureteroscope (4.5F) and Bugbee electrode with pure cutting current at the 6 o'clock position. A Double-J stent was inserted and removed 1 week later. This was followed by serial physical examination, renal function test, urine analysis, urine culture, and imaging studies in the 1st month and every 3 months after Double-J stent removal. Hydroureteronephrosis was significantly decreased in nine patients. Postoperative VCUG revealed no sign of iatrogenic vesicoureteral reflux. In addition, a follow-up renal scan showed remarkable improvement in the renal function in the patients who had decreased renal function, except for one patient in whom uncontrolled urosepsis developed in the follow-up; the patient underwent cutaneous ureterostomy. No UTI was detected in the group who presented with recurrent UTI and urosepsis. According to the results of our study, endoureterotomy may be an alternative in management of POMU. Of course, further studies with longer follow-up periods are needed to confirm the applicability of this method in patients younger than 1 year.

Ureterovesical junction obstruction causes increment in smooth muscle contractility, and cholinergic and adrenergic activity in distal ureter of rabbits

Background/PurposeThe controversy in management of primary obstructed megaureter necessitates further elucidation of the underlying pathophysiology. We evaluated smooth muscle contractility, and cholinergic, adrenergic and serotonergic activity of rabbit distal ureters after ureterovesical junction (UVJ) obstruction. MethodsSham (SH) operation, partial obstruction (PO) and complete obstruction (CO) of the right UVJ were performed in rabbits. Three weeks later, distal ureters were isolated; spontaneous contractions (SC), contractile responses to electrical field stimulation (EFS), high KCl, carbachol, phenylephrine and serotonin were recorded. ResultsSC amplitudes increased in CO compared to PO and SH (p<0.001). SC frequency was higher in CO (p<0.05). EFS-induced contraction amplitudes were greater in CO than other groups (p<0.05). High KCl-induced contractions were greater in CO (p<0.001) and PO (p<0.01). Carbachol-induced contractility was enhanced in CO and PO (p<0.05). Contractile response to phenylephrine was greater in CO than other groups (p<0.05). Serotonin induced contractile responses in CO and PO, greater in CO (p<0.05). UVJ obstruction also increased spontaneous contractility in contralateral PO and CO ureters. ConclusionsUVJ obstruction increased spontaneous and neurotransmitter-induced contractions in an obstruction grade-dependent manner. Obstruction also altered contractility of the contralateral ureters. Our findings may serve to provide further understanding of the pathophysiology of megaureter.

LONG-TERM OUTCOME ANALYSIS OF STARR PLICATION FOR PRIMARY OBSTRUCTIVE MEGAURETERS

The Starr technique of tapering megaureters was first reported in 1979. Although this method of ureteral plication is well known, to our knowledge there are no clinical studies regarding outcomes. We report the first long-term outcome results with the Starr technique for primary obstructive megaureters. Three girls and 10 boys with a total of 16 primary obstructive megaureters (3 bilateral) underwent reimplantation with Starr plication between 1988 and 2000. Baseline and followup renal function (average followup 6.2 years) was determined with renal scan and/or 24-hour urinary creatinine clearance. Average age at operation was 5.6 years (range 2 months to 13 years). All ureters were plicated using the Starr technique with interrupted polydioxanone sutures performed by a single surgeon (CEH). Reimplantation methods were the Hendren technique in 7 and Politano-Leadbetter in 9. No ureter demonstrated obstruction postoperatively. One ureter refluxed, which resolved with subureteral collagen injection. Seven patients had mean preoperative and postoperative creatinine clearance +/- SD 72.9 +/- 14.8 and 102.1 +/- 10.9 cc per minute, respectively (p <0.05). Six patients underwent preoperative and postoperative renal scans. Average preoperative relative renal function on renal scan in the kidney with a megaureter was 53.0% +/- 6.7% (range 37% to 84%). Long-term followup (average 4.1 years) renal scan revealed a relative function of 53.3% +/- 9.2% (range 37% to 100%). Our data demonstrate that Starr plication is a safe procedure that provides long-term stabilization of renal function in the management of primary obstructive megaureter.

Changing concepts in management of primary obstructive megaureter : M.A. Keating, J. Escala, H.M. Snyder III, et al. J Urol 142:636–640, (August), 1989

Changing concepts in management of primary obstructive megaureter : M.A. Keating, J. Escala, H.M. Snyder III, et al. J Urol 142:636–640, (August), 1989

Changing Concepts in Management of Primary Obstructive Megaureter

The management of neonatal urinary tract dilatations represents one of the most challenging dilemmas in pediatric urology today. We have been confronted with 44 renal units in 35 neonates diagnosed as having primary obstructive megaureter during the last 6 years. Of these units 23 in 17 infants were diagnosed antenatally and 20 (87 per cent) have been managed without surgical intervention. Notably, 16 renal units were graded as moderate to severe megaureters by an excretory urogram. The decision to manage conservatively was based on the initial extraction of the 99mdiethylenetriaminepentaacetic acid renal scan (the extraction factor). This estimate of absolute renal function has been used to differentiate dilatations with obstructive implications for the renal parenchyma from those without. Significantly, expectant treatment has resulted in improvement of dilatation on sequential excretory urograms in 15 megaureters and none has shown a deterioration of function by renal scan. Similar diagnostic criterion also has resulted in conservative management for 12 of 21 additional neonatal megaureters seen during this period with symptoms or they were discovered serendipitously. Only 2 of these 12 megaureters required surgical correction. The neonatal primary megaureter appears in many cases to represent a different entity than those that commonly presented before the advent of antenatal and perinatal diagnosis.