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

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.

Antegrade left ureterolithotripsy in a patient with previous psoas-hitch ureteral reimplantation

A standard surgical treatment of distal ureteric defects is represented by the ureteroneocystostomy-ureteric reimplantation. However, the procedure involves an anatomical alteration of the ureterovesical (neo)junction that often hinders the retrograde catheterisation of the reimplanted ureter.We describe a case of antegrade ureterolithotripsy (AULT) in a psoas-hitch reimplanted ureter. A woman with severe left hydronephrosis supported by a subcentimetric proximal ureteral stone in a psoas-hitch reimplanted ureter was referred to our unit. Retrograde ureteroscopy was unsuccessful due to impossibility in incannulating the ureteral neo-orifice. Following the placement of a percutaneous nephrostomy, percutaneous AULT through ureteral sheath was successfully performed with complete treatment of the stone.AULT may represent a viable alternative in the management of ureteral stones when the upper urinary tract is not amenable to retrograde ureteroscopy. In experienced hands, the procedure is straightforward and may avoid the adoption of transabdominal approaches.

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.

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.

The Shanfield anastomosis revisited: Its applications and early outcome

BACKGROUND

Shanfield first described a simple ureteric implantation technique involving a U-stitch anchoring the spatulated end of the transplant ureter to the interior of the intact bladder through a small stab wound. We present an extrapolation of this principle to Mitrofanoff channels and native ureteric reimplantations and further extend it to a laparoscopic approach in some.

METHODS

A retrospective case-note reviewing the Shanfield ureteric reimplantation in fifteen children between October 2014 and May 2017 was performed.

RESULTS

Fifteen children (females n = 9), median age 6 years (range 8 months-15 years), underwent a Shanfield anastomosis for ureteric (n = 3) or Mitrofanoff (n = 12) implantation into the bladder. Their diagnoses were: vesicoureteric reflux (n = 2), vesicoureteric obstruction (n = 1), neuropathic bladder (n = 4), exstrophy (n = 2, bladder and cloacal), nonneuropathic bladder (n = 3), cloaca (n = 2), and one with failed urethral reconstruction of a Y-duplication. Two ureteric reimplantations and one appendix-Mitrofanoff were undertaken entirely laparoscopically. The bladder was not opened in 9/15, with the remaining six in an ileocystoplasty and one complex cloaca. Fourteen patients were available for follow-up at a median 18.2 (5.8-43.3) months. There was no anastomotic leakage in any, and one stenosis was successfully managed with simple dilatation. One complex patient required a new Mitrofanoff channel.

CONCLUSION

Our preliminary data suggest that the Shanfield anastomosis offers a safe, robust, and simple antireflux implantation technique without the need to formally open the bladder. The technique offers several advantages as it allows overcoming the problem of inadequate tunnelling when the bladder template is deficient. Meanwhile, its simplicity permits it to be faithfully reproduced with laparoscopy in select patients.

TYPE OF STUDY

Treatment study.

LEVEL OF EVIDENCE

IV.