Comparison of histopathological characteristics of polyacrylate polyalcohol copolymer with dextranomer/hyaluronic acid after injection beneath the bladder mucosa layer: a rabbit model

Endoscopic injection of bulking agents in pediatric vesicoureteral reflux: a narrative review of the literature

In the last 20 years, endoscopic injection (EI) has affirmed as a valid alternative to open surgery for management of pediatric vesicoureteral reflux (VUR). This study aimed to investigate and discuss some debated aspects such as indications, bulking agents and comparison, techniques of injection and comparison, predictive factors of success, use in specific situations. EI is minimally invasive, well accepted by patients and families, with short learning curve and low-morbidity profile. It provides reflux resolution rates approaching those of open reimplantation, ranging from 69 to 100%. Obviously, the success rate may be influenced by several factors. Recently, it is adopted as first-line therapy also in high grade reflux or complex anatomy such as duplex, bladder diverticula, ectopic ureters. The two most used materials for injection are Deflux and Vantris. The first is absorbable, easier to inject, has lower risk of obstruction, but can lose efficacy over time. The second is non-absorbable, more difficult to inject, has higher risk of obstruction, but it is potentially more durable. The two main techniques are STING and HIT. To date, the ideal material and technique of injection has not yet clearly established, but the choice remains dependent on surgeon's preference and experience.

Management of Vesicoureteral Reflux: What Have We Learned Over the Last 20 Years?

Vesicoureteral reflux (VUR) is associated with increased risks of urinary tract infection, renal scarring and reflux nephropathy. We review advancements over the last two decades in our understanding and management of VUR. Over time, the condition may resolve spontaneously but it can persist for many years and bladder/bowel dysfunction is often involved. Some factors that increase the likelihood of persistence (e.g., high grade) also increase the risk of renal scarring. Voiding cystourethrography (VCUG) is generally considered the definitive method for diagnosing VUR, and helpful in determining the need for treatment. However, this procedure causes distress and radiation exposure. Therefore, strategies to reduce clinicians' reliance upon VCUG (e.g., after a VUR treatment procedure) have been developed. There are several options for managing patients with VUR. Observation is suitable only for patients at low risk of renal injury. Antibiotic prophylaxis can reduce the incidence of UTIs, but drawbacks such as antibiotic resistance and incomplete adherence mean that this option is not viable for long-term use. Long-term studies of endoscopic injection have helped us understand factors influencing use and the effectiveness of this procedure. Ureteral reimplantation is still performed commonly, and robot-assisted laparoscopic methods are gaining popularity. Over the last 20 years, there has been a shift toward more conservative management of VUR with an individualized, risk-based approach. For continued treatment improvement, better identification of children at risk of renal scarring, robust evidence regarding the available interventions, and an improved VUR grading system are needed.

Endoscopic Injection Treatment of Vesicoureteral Reflux in Children: Meeting with the Factors Involved in the Success Rate

The challenges and controversies in vesicoureteral reflux intervention guidelines resulted in a more individualized treatment planning. Endoscopic injection therapy is now widely used and is considered preferable, but still remains less successful than ureteral reimplantation. Τhe endoscopic vesicoureteral reflux approach should be risk-adapted to current knowledge, so more experience and longer-term follow-up are needed. The precise of preoperative, intraoperative, and postoperative factors that affecting endoscopic injection therapy success rates and outcome have not yet been clearly determined. The aim of this study was to investigate these associated factors. Although the reflux grade is the most well-known factor that can affect the success of the procedure, there is no agreement on which factors are the most influential for the efficacy of endoscopic reflux treatment. So, we carried out a broad review of published papers on this topic, and we presented all the potential predictive variables of endoscopic reflux resolution in children.

Local tissue reaction and histopathological characteristics of three different bulking agents: a rabbit model

Purpose:

We assessed the efficacy and safety of a single injection of three bulking agents over the short- and long-term follow-ups in rabbits. Dermal and preputial matrices were compared with Deflux (DxHA) injection.

Material and methods:

Twenty-four rabbits were divided into three groups. Group I (n=8) underwent the injection of a lyophilized dermal matrix (LDM) beneath the seromuscular layer of the bladder wall. Rabbits in group II (n=8) were injected with lyophilized preputial matrix (LPM). Rabbits of group III (n=8) were injected with DxHA as the control group. They were followed up for 1 and 6 months after the injection. Subcutaneous injection of all bulking agents was also performed in nude mice. Biopsies were stained with LCA (leukocyte common antibody), CD68, CD31, and CD34. Scanning electron microscopy (SEM) and MTT assay were also performed.

Results:

Immunohistochemistry staining with CD68 and LCA revealed higher inflammation grade in LDM as compared with LPM and DxHA. Fibrosis grade was also higher in LDM both in short- and long-term follow-ups. However, no significant difference was detected in CD31 and CD34 staining between control and experimental groups. SEM analysis showed that the particle size of LPM was more similar to DxHA. MTT assay revealed that cell proliferation was similar in DxHA, LDM, and LPM. In-vivo assay in nude mice model showed more promising results in LPM as compared with LDM.

Conclusion:

The long-term results demonstrated that LPM was more similar to Deflux with the least local tissue reaction, inflammation, and fibrosis grade.

New bulking agent for the treatment of vesicoureteral reflux: Polymethylmethacrylate/dextranomer

Purpose

The aim of this study was to report preliminary results of endoscopic treatment of vesicoureteral reflux in children with a single injection of a new bulking agent, cross-linked dextran and polymethylmethacrylate mixture.

Materials and Methods

We performed a single-center, single surgeon, prospective, off-label study using polymethylmethacrylate/dextranomer to treat vesicoureteral reflux. All patients underwent endoscopic injection, followed by renal ultrasound and voiding cystourethrogram at 3 months postoperatively to identify de novo or worsening hydronephrosis and vesicoureteral reflux correction (to Grade 0 or I).

Results

Eighteen patients underwent injection of polymethylmethacrylate/dextranomer at our institution between April 2013 and December 2013. Ten were males and eight were females, with a median age of 58 months (range, 6 months to 5 years). Vesicoureteral reflux was unilateral in three patients and bilateral in 15, for a total of 33 renal refluxing units. Vesicoureteral reflux was Grade I in one renal refluxing unit, Grade II in 12, Grade III in 16, and Grade IV in four. Mean injected volume was 0.86 mL. Reflux was corrected in 23 renal refluxing units (69.7%) according to the 3-month voiding cystourethrogram. Complications included urinary retention in one patient. Mild pyelectasis was noted in one patient at 3 months, which spontaneously resolved 3 months later.

Conclusions

Our short-term data show that polymethylmethacrylate/dextranomer injection can be used to treat vesicoureteral reflux with comparable efficacy to other substances currently used and a low rate of complications. Long-term follow-up is required to confirm the usefulness of this material in treating vesicoureteral reflux.

Endoscopic injection therapy

Since the U.S. Food and Drug Administration approved dextranomer/hyaluronic acid copolymer (Deflux) for the treatment of vesicoureteral reflux, endoscopic injection therapy using Deflux has become a popular alternative to open surgery and continuous antibiotic prophylaxis. Endoscopic correction with Deflux is minimally invasive, well tolerated, and provides cure rates approaching those of open surgery (i.e., approximately 80% in several studies). However, in recent years a less stringent approach to evaluating urinary tract infections (UTIs) and concerns about long-term efficacy and complications associated with endoscopic injection have limited the use of this therapy. In addition, there is little evidence supporting the efficacy of endoscopic injection therapy in preventing UTIs and vesicoureteral reflux-related renal scarring. In this report, we reviewed the current literature regarding endoscopic injection therapy and provided an updated overview of this topic.