Intravesical tunnel length to ureteral diameter ratio insufficiently explains ureterovesical junction competence: A parametric simulation study

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.

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

AIMS

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.

METHODS

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.

RESULTS

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 133 min (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.

DISCUSSION

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.

Fluid mechanical modeling of the upper urinary tract

The upper urinary tract (UUT) consists of kidneys and ureters, and is an integral part of the human urogenital system. Yet malfunctioning and complications of the UUT can happen at all stages of life, attributed to reasons such as congenital anomalies, urinary tract infections, urolithiasis and urothelial cancers, all of which require urological interventions and significantly compromise patients' quality of life. Therefore, many models have been developed to address the relevant scientific and clinical challenges of the UUT. Of all approaches, fluid mechanical modeling serves a pivotal role and various methods have been employed to develop physiologically meaningful models. In this article, we provide an overview on the historical evolution of fluid mechanical models of UUT that utilize theoretical, computational, and experimental approaches. Descriptions of the physiological functionality of each component are also given and the mechanical characterizations associated with the UUT are provided. As such, it is our aim to offer a brief summary of the current knowledge of the subject, and provide a comprehensive introduction for engineers, scientists, and clinicians who are interested in the field of fluid mechanical modeling of UUT. This article is categorized under: Cancer > Biomedical Engineering Infectious Diseases > Biomedical Engineering Reproductive System Diseases > Biomedical Engineering.

Ureteroneocystostomy without ureteral remodeling for grade III-V vesicoureteral reflux treatment

BACKGROUND

Ureteral remodeling (tapering or tailoring) is often performed alongside ureteroneocystostomy (ureteric reimplantation) procedures despite limited evidence on its role in promoting reflux resolution.

OBJECTIVES

To investigate the efficacy of ureteroneocystostomy in the absence of adjuvant ureteral remodeling for promoting reflux resolution in grade III-V vesicoureteral reflux.

STUDY DESIGN

A retrospective analysis identified pediatric patients who underwent open or robotic assisted ureteroneocystostomy (OUN and RAUN, respectively) without ureteral remodeling (tailoring or tapering) at a single tertiary care center. The primary endpoint of reflux resolution was defined as no reflux on latest follow up postoperative voiding cystourethrogram (VCUG). Ureteral dilation was analyzed using the ureteral diameter ratio (UDR), which normalized for image characteristics. Inclusion criteria was as follows: grade III-V reflux, accessible postoperative VCUG scan, RAUN after June 2013 following technique optimization, and no other structural urologic abnormality or associated neurogenic bladder.

RESULTS

A total of 68 ureters were analyzed (Grade III = 28, Grade IV = 27, Grade V = 13, OUN = 23, RAUN = 45). Complete reflux resolution was achieved postoperatively in 96% (27/28) of grade III, 100% (27/27) of grade IV and 100% (13/13) grade V cases, for a combined resolution rate of 99%. In the one failed case, the preoperative UDR was in the second quartile and postoperatively, reflux diminished from grade III to grade I. Notably, no cases with UDRs in the largest quartile required tapering/tailoring for complete reflux resolution.

DISCUSSION

Ureteral tapering and tailoring were unnecessary to achieve reflux resolution in grade III-V VUR by both OUN and RAUN. Additionally, the unsuccessful case was classified as grade III with a UDR value in the second quartile, suggesting that high grade reflux (IV-V) can be repaired without tapering with equal success rates to that of grade III VUR repair, which is classically not tapered. Tapering was unnecessary for complete reflux resolution in the cases with the largest ureteral diameter ratios (UDR). These findings are limited by the single center retrospective nature of the study.

CONCLUSIONS

This study demonstrates that vesicoureteral reimplantation for resolution of grade III-V reflux is successful in the absence of ureteral remodeling techniques.

The 5:1 rule overestimates the needed tunnel length during ureteral reimplantation

AIMS

Paquin asserts that in order for ureterovesical junctions (UVJs) to prevent reflux, the ureteral tunnel length-to-diameter ratio needs to be 5:1. We hypothesize that the surgical implementation of this observation results in an overestimation of the needed length-to-diameter ratio to prevent vesicoureteral reflux.

METHODS

With finite elements, we model the urine storage phase of the bladder under nonlinear conditions. In the reference state, the bladder is assumed to be a sphere with an oblique straight elliptical hole as the UVJ. Broad parametric studies on different length-to-diameter ratios are performed as the bladder volume increases from 10% to 110% capacity.

RESULTS

The capability of the UVJ to prevent reflux during storage depends on its length-to-diameter ratio. UVJs with larger length-to-diameter ratios lengthen and narrow as the bladder volume increases, causing the closure of the UVJ and rise in its flow resistance. Our model shows that the UVJ length-to-diameter ratio decreases as the bladder volume increases. The 5:1 ratio implemented at 80% capacity-approximate volume or bladder wall stretch during ureteroneocystostomy (UNC)-corresponds to 7:1 at the reference state-used by Paquin. The 5:1 ratio implemented at the reference state corresponds to 3:1 at 80% capacity.

CONCLUSIONS

Our modeling results are consistent with Paquin's original observation on the significance of the UVJ length-to-diameter ratio in preventing reflux. They, however, indicate that the surgical implementation of this rule during UNC results in an overestimation of the requisite tunnel length-to-diameter ratio to prevent reflux. They also suggest that the UVJ closure is due to the bladder wall deformation rather than the pressure.

Laparoscopic extravesical ureteral reimplantation for correction of primary and secondary megaureters: Preliminary report of a new simplified technique

PURPOSE

To describe a simplified surgical technique for the treatment of primary and secondary obstructed megaureters in children by laparoscopic extravesical ureteral reimplantation (LEUR) and evaluate the short-term outcomes.

METHODS

Prospective study of children with primary and secondary megaureters treated at our institution between 2016 and 2018 by LEUR. A transperitoneal approach was used in all cases. The distal ureter was transected at the level of the stenosis. Detrusor muscle fibers were divided to expose bladder mucosa. The distal ureter was introduced into the bladder to create a valve-like mechanism. The ureter was fixed to the bladder mucosa by four stitches. We analyzed indications for surgery, complications and outcomes. Definition of success was relieved of obstruction and absence of VUR.

RESULTS

Six patients with a mean age of 28.83 months (SD: 21.4) underwent LEUR. Indications for surgery were: infection [2], obstruction [2], decrease in renal differential function [1] and increase in hydronephrosis [1]. There were no intraoperative complications. Resolution of hydronephrosis, obstruction and VUR was achieved in all cases. Mean follow-up was 13 months (SD: 6.67).

CONCLUSION

LEUR for the correction of primary and secondary megaureters by this new technique is safe. The most important advantage is that this technique is simpler and more easily reproducible than conventional LEUR. However, long-term follow-up is required.

TYPE OF STUDY

Prospective, observational.

LEVEL OF EVIDENCE

Level III.

Laparoscopic posterior appendix Mitrofanoff using the modified Shanfield anastomosis

Laparoscopic transperitoneal technique for appendicovesicostomy was performed in a 5-year-old boy with a non-neurogenic neuropathic bladder using a transumbilical 5-mm port, two 3-mm working ports and a modified Shanfield anastomosis. Posterior extramucosal detrusorotomy and submucosal dissection was performed. The proximal appendix was spatulated and advanced into the bladder through a mucosal window using a U-stitch and fixed. The detrusor was then approximated creating an antirefluxing extramucosal tunnel. VQ plasty was fashioned for stoma formation. The procedure and postoperative period were uneventful. Clean intermittent catheterisation (CIC) was established subsequently and continued for the last 6 months. Our experience shows that appendix Mitrofanoff can be performed with minimal number and size of ports, resulting in a good cosmetic outcome. A simplified anastomosis makes it less cumbersome, and catheterisation is reliable as there is no mucosa-mucosa junction to negotiate.

Ureteral tunnel length versus ureteral orifice configuration in the determination of ureterovesical junction competence: A computer simulation model

INTRODUCTION

The long-held belief that a ureteral re-implant tunnel should be five times the diameter of the ureter, as proposed by Paquin in 1959, ignores the effect of the orifice on the occurrence of reflux. In 1969, Lyon proposed that the shape of the ureteral orifice (UO) is more important than the intravesical tunnel. However, both theories missed quantitative evidence from principles of physics. The goal of the current study was to test Lyon's theory through numerical models (i.e. to quantify the sensitivity of ureterovesical junction (UVJ) competence to intravesical tunnel length and to the UO).

MATERIALS AND METHODS

The closure of a three-dimensional spatial configuration of ureter, constrained within a bladder, was simulated. Two common UO shapes (i.e. golf type vs 2-mm volcano type (Summary Fig.)), and two different intravesical ureteral tunnel length/diameter ratios (3:1 and 5:1) were examined. The required closure pressures were then compared.

RESULTS

The UO was a significant factor in determining closure pressure. Given the same intravesical ureteral tunnel length/diameter ratio, the required closure pressure for the volcanic orifice was 78% less than that for the golf orifice. On the other hand, the intravesical ureteral tunnel length/diameter ratio had minimal effect on the required closure pressure. As the intravesical ureteral tunnel length/diameter ratio changed from 3:1 to 5:1, the required closure pressure was reduced by less than 7%, regardless of the orifice shape.

CONCLUSIONS

The simulation results showed that UVJ competence was more sensitive to a 2-mm protrusion of the UO compared to an increase in the intravesical tunnel length from 3:1 to 5:1. This agrees with Lyon's theory, and at the same time challenges Paquin's 5:1 rule. Researchers could use this information to consider the UO configuration in further animal, human, computer or material models.

Evaluation of Mathisen's technique for ureteral reimplantation in children with primary vesicoureteral reflux

INTRODUCTION

Although cross-trigonal ureteral reimplantation (Cohen) is a commonly used technique in children, it represents a non-physiological transfer of the ureteral orifices and may prove challenging with regard to endoscopic ureteral operations in later life. In 1964, Mathisen described an alternative method of ureteral reimplantation with lateralization of the neohiatus, creating an orthotopic course of the submucosal ureter. We have evaluated success and complication rates of both techniques that were applied sequentially at our departments.

METHODS

Forty-eight consecutive patients (83 ureters, 24 males/24 females) following Mathisen reimplantation were compared with 53 consecutive patients (98 ureters, 30 males/23 females) following Cohen reimplantation. Inclusion criteria were primary vesicoureteral reflux (VUR) and no previous intervention. Reflux grades (Mathisen 58 ureters/69.9% VUR ≥ III; Cohen 66 ureters/66.7% VUR ≥ III) and the occurence of other complicating factors (ureteroceles, megaureters, posterior urethral valves) in both groups were comparable.

RESULTS

After Cohen's reimplantation there were no immediate complications requiring intervention; during follow-up (mean 28.2 months) three patients (5.6%) suffered febrile urinary tract infections (UTIs), of which one (1.8%) was diagnosed with a persisting VUR. Persistent hydronephroses (≥II SFU) were recorded in six patients (13.2%). After reimplantation using Mathisen's technique, two patients (4.1%) suffered significant intravesical bleeding; during follow-up (mean 23.06 months) four patients (8.3%) suffered febrile UTIs, and seven patients (14.5%) were diagnosed with persisting VUR after a mean follow-up of 10.8 months. The patients with persistent VUR had more commonly high-grade (IV and V) VUR initially, compared to the whole group. Two patients (4.1%) had persistent hydronephroses (≥II SFU). Mathisen's technique for ureteral reimplantation yielded a significantly (p = 0.0256 patients, p = 0.006 ureterorenal units) lower success rate (85.5% patients, 89.2% ureterorenal units) in comparison with Cohen's technique (98.2% patients, 99% ureterorenal units). Although there was no intervention for obstruction, persistent hydronephrosis was more common in the Cohen group (13.2% vs. 4.1%, n.s.).

CONCLUSIONS

Despite the advantages of an orthotopic ureteral orifice close to the bladder neck, as achieved by Mathisen's reimplantation, cross-trigonal ureteral reimplantation proved more reliable for VUR correction. As regards optimizing the results, patient selection for either technique could prove essential. Nevertheless, as regards the difficulties with ectopic ureteral orifices in the Cohen technique in the long-term follow-up, the concept of anatomic, orthotopic ureteral reimplantation should be pursued and the technique should be further refined.

Modified ureteral orthotopic reimplantation method for managing infant primary obstructive megaureter: a preliminary study

PURPOSE

To describe a modified ureteral orthotopic reimplantation method in infant with primary obstructive megaureter (POM) and report our initial experience.

METHODS

Thirteen children with POM (range 1-7 months) underwent modified transvesical ureteral implantation surgery. Treatment consists of transecting the ureter proximal to the obstruction and performing orthotopic reimplantation in end freely fashion with distal ureter protruding into the bladder, providing dilated ureteral diameter: ureteral exposure length in bladder ratio of 1:1.5-2. All patients underwent repeat ultrasound, radionuclide imaging and voiding cystourethrography. Cystoscopy was conducted in patients at 6 months after surgery.

RESULTS

The mean operating time was 40 min. There were one redo this procedure for recurrent obstruction and one Cohen reimplantation for Grade 5 vesico-ureteral reflux in one bilateral POM. Hydroureteronephrosis improved in other 11 patients, and the ureter diameter was significantly reduced from preoperative measurements. At the time of cystoscopy, thick and large volcanic-shaped ureteral orifice was found and urine ejected intermittently.

CONCLUSIONS

The proposed 'modified ureteral orthotopic reimplantation' with no tapering or advancement for POM in infants is a simple, feasible and less invasive procedure that had good success rates in this small series. Further, larger studies are required to support or negate the usefulness of this technique.