Use of full-length metallic stents in malignant ureteral obstruction

Cost-effectiveness of Resonance® metallic ureteral stent compared with standard polyurethane ureteral stents in malignant ureteric obstruction: A cost-utility analysis

Background

Malignant ureteral obstruction (MUO) is a frequent challenge for urologists. Patients have poor prognoses, treatment aims to improve quality-of-life while optimising renal function. Standard practice in the United Kingdom is to use polyurethane stents, which require frequent surgical replacements for blockages and encrustation. More durable metallic stents are available, although these incur an increased initial purchase price.

Aims

We aim to assess whether the use of polyurethane double-J (JJ) or metallic stent, Resonance® is more cost-effective for managing MUO in the UK healthcare setting.

Methods

A Markov model was parameterised to 5 years with costs and health-related quality-of-life consequences for treating MUO with Resonance metallic stent (Cook Medical), versus standard JJ stents, from the UK care system perspective, with 3.5% discounting. Deterministic and probabilistic sensitivity analyses were undertaken to assess the effect of uncertainty.

Results

Over 5 years, approximately four fewer repeat surgical interventions were estimated in the metallic stent arm compared with the JJ stent, driving a 23.4% reduction in costs. The mean estimates of costs and benefits indicate that treatment of MUO with Resonance for 5 years is dominant over JJ stents. Over 5 years a cost-saving of £2164.74 and a health gain of +0.046 quality-adjusted life years (QALYs) per patient is estimated. With a maximum willingness to pay of £20 k per QALY, a net monetary benefit (NMB) of £3077.83 is estimated. Probabilistic sensitivity analysis at a willingness to pay threshold of £20 000 indicates an 89.3% probability of Resonance being cost-effective over JJ stents. Within 1-year savings of £726.53 are estimated driven by a reduction of two fewer repeat surgical interventions when using the metallic stent.

Conclusions

Resonance metallic stents for the treatment of MUO reduce the number of repeat procedures and could be a cost-effective option for the treatment, potentially offering efficiencies to the healthcare system.

Recent development and future application of biodegradable ureteral stents

Ureteral stenting is a common clinical procedure for the treatment of upper urinary tract disorders, including conditions such as urinary tract infections, tumors, stones, and inflammation. Maintaining normal renal function by preventing and treating ureteral obstruction is the primary goal of this procedure. However, the use of ureteral stents is associated with adverse effects, including surface crusting, bacterial adhesion, and lower urinary tract symptoms (LUTS) after implantation. Recognizing the need to reduce the complications associated with permanent ureteral stent placement, there is a growing interest among both physicians and patients in the use of biodegradable ureteral stents (BUS). The evolution of stent materials and the exploration of different stent coatings have given these devices different roles tailored to different clinical needs, including anticolithic, antibacterial, antitumor, antinociceptive, and others. This review examines recent advances in BUS within the last 5 years, providing an in-depth analysis of their characteristics and performance. In addition, we present prospective insights into the future applications of BUS in clinical settings.

In vivo urinary compatibility of Mg-Sr-Ag alloy in swine model

A biodegradable metallic ureteral stent with suitable mechanical properties and antibacterial activity remains a challenge. Here we reveal the scientific significance of a biodegradable Mg-Sr-Ag alloy with a favorable combination of balanced mechanical properties, adjustable indwelling time in urinary tract and evident antibacterial activity via in vivo experiments in a swine model. Attributed to the rheo-solidification process, equiaxial microstructure and significantly refined grains (average grain size: 27.1 μm) were achieved. Mg₁₇Sr₂ and Mg₄Ag were found as the primary precipitates in the matrix, due to which the alloy obtained ca. 111% increase in ultimate tensile strength in comparison to pure magnesium. Both the in vitro and in vivo results demonstrated the satisfactory biocompatibility of the alloy. Histological evaluation and bioindicators analysis suggested that there was no tissue damage, inflammation and lesions in the urinary system caused by the degradation process. The stent also improved the post-operative bladder functions viewed from the urodynamic results. Our findings highlight the potential of this alloy as antibacterial biodegradable urinary implant material.

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Innovative biodegradable antibacterial Mg-Sr-Ag alloy.

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In vivo study in pig ureter models.

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Enhanced mechanical properties and adjustable indwelling time.

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Outstanding urinary compatibility and evident antibacterial activity.

Influence of Single Stent Size and Tandem Stents Subject to Extrinsic Ureteral Obstruction and Stent Occlusion on Stent Failure

Background and Purpose: Drainage of obstructed kidney due to extrinsic ureteral obstruction (EUO), required to prevent renal damage, is often achieved using double-J ureteral stents. But these stents fail frequently, and there is considerable debate regarding what stent size, type and configuration offer the best option for sustained drainage. Here, we examine the impact of stent diameter and choice of single/tandem configuration, subject to EUO and various degrees of stent occlusion, on stent failure. Methods: Computational fluid dynamics (CFD) simulations and an in vitro ureter-stent experiment enabled quantification of flow behavior in stented ureters subject to EUO and stent occlusions. Various single and tandem stents under EUO were considered. In each simulation and experiment, changes in renal pressure were monitored for different degrees of stent lumen occlusion, and onset of stent failure as well as simulated distributions of fluid flow between stent and ureter lumina were determined. Results: For an encircling EUO that completely obstructs the ureter lumen, with or without partial stent occlusion, the choice of stent size/configuration has little effect on renal pressure. The pressure increases significantly for ~90% stent lumen occlusion, with failure at >95% occlusion, independent of stent diameter or a tandem configuration, and with little influence of occlusion length along the stent. Conclusions: Stent failure rate is independent of stent diameter or single/tandem configuration, for the same percentage of stent lumen occlusion, in this model. Stent failure incidence may decrease for larger diameter stents and tandem configurations, because of the larger luminal area.

Comparative study of renal drainage with different ureteral stents subject to extrinsic ureteral obstruction using an in vitro ureter-stent model

BACKGROUND

To compare the efficacy of different ureteral stents subject to extrinsic ureteral obstruction (EUO), in a controlled in vitro stented ureter experiment.

METHODS

We employ an in vitro ureter-stent experimental set-up, with latex tubing simulating flexible ureters attached to vessels simulating renal units and bladders. The flow behavior of five ureteral stents-polymeric 8F, tandem 6F, tandem 7F, endopyelotomy and metal-was tested under a ureteral deformation configuration of 40°, with 2000 g external force over a 3.5 cm length of the ureter. A constant fluid flow was applied through the ureter-stent configurations, and pressure fluctuations in the renal unit were monitored. We considered a renal unit pressure of 10 cmH₂O or flow discontinuation in the bladder as stent failure. Urine containing debris was mimicked by use of a colloidal solution.

RESULTS

Of all assessed ureteral stents, under EUO conditions, only the single 8F stents remained patent throughout the length of the experiment. All other stents-tandem 6F and 7F, single 7F, metal and endopyelotomy-displayed limitations.

CONCLUSIONS

Tandem and metal stents show no superiority over large luminal polymeric stents for EUO treatment in this in vitro model. Larger luminal stents offer excellent resistance to external pressure and allow adequate colloidal flow. The need for frequent exchange and bladder irritation should also be considered in the choice of stent configuration for treatment of kidney drainage under EUO.

A systematic review of long-duration stents for ureteral stricture: which one to choose?

OBJECTIVE

To define which long-term stent would work best in malignant ureteral obstruction (MUO) and benign ureteral obstruction (BUO), focusing on their mechanisms of action, price and insertion approach.

METHODS

A systematic review was developed using the MEDLINE and Scopus databases and in accordance with the PRISMA checklist. There were no language restrictions for the search. Studies describing the use of metallic ureteric stents for MUO and for BUO in humans were included.

RESULTS

We analyzed five types of metallic stents (35 papers) and also the experience with the tumor and extra-anatomical stents. The Resonance, Memokath and Allium ureteral stents were found to be useful in BUO and MUO. The Uventa stent performed well in chronic ureteral obstruction. The Detour bypass stent was a recommended option in those patients who had complete obstruction of the ureter and were unfit for reconstructive surgery. There was no difference with regard to the insertion technique and both antegrade and retrograde approaches were equally successful. Although tumor stents showed a good performance, there were very few published studies on it.

CONCLUSION

Metallic stents are a suitable option for MUO and BUO. When compared to standard double J stents, although they are relatively high priced, they show a financial benefit in the long-term. The Detour bypass stent seems to be an effective alternative for complete ureteral obstruction or patients unfit for surgery. Further prospective randomized studies should be done on the effectiveness of tumor stents versus metallic stents.

Ureteroiliac artery fistula caused by full-length metallic ureteral stenting in a malignant ureteral obstruction: a case report

Background

The metallic stent is a new device for relieving the urinary tract in patients with malignant ureteral obstruction with short life expectancy and has been used frequently worldwide for its efficacy and safety. A ureteroarterial fistula with indwelling ureteral stent is rare but highly fatal, and there are several reports of ureteroarterial fistula treated by conventional polymer stents, although there are no reports on metallic stents. To our knowledge, this paper describes the first case of a ureteroiliac artery fistula caused by a full-length metallic ureteral stent in malignant ureteral obstruction.

Case presentation

Our patient was a 57-year-old Asian woman with a history of locally advanced cervical cancer who underwent abdominal total hysterectomy and chemoradiotherapy. She was diagnosed with right hydronephrosis and hydroureter secondary to upper ureteral obstruction because of retroperitoneal lymph node metastasis. A urinary tract obstruction after placement of 12 months of polymer stent followed by 18 months of metallic stent was relieved, consequently resulting in intermittent gross hematuria with bladder tamponade and anemia. Contrast-enhanced computed tomography could not reveal a ureteroarterial fistula; however, retrograde pyelography emphasized the existence of a ureteroiliac artery fistula. The patient underwent successful endovascular heparin-bonded stent graft placement, and her gross hematuria disappeared thereafter.

Conclusion

The metallic stent is a useful device for patients with malignant ureteral obstruction with a short life expectancy, although it may impose a higher pressure on the extraureteral tissue than conventional polymer stents due to its properties and may cause a ureteroarterial fistula. The narrowing of the external iliac artery diameter visualized by computed tomography may be helpful for predicting ureteroarterial fistulas.

Risk factors in the prediction of long-term patency of Resonance metallic ureteric stent in malignant ureteric obstruction

Objectives

Cancer is the second leading cause of death globally in 2018 with an estimated 9.6 million deaths. The costs of managing malignant ureteric obstruction (MUO) is a significant burden to any healthcare system. However, the management of MUO has long been a challenge for urologists. The standard options of percutaneous nephrostomy or polymer double J stents are fraught with problems. We report a large patient series with long-term follow-up in the use of Resonance metallic ureteric stents to relieve MUO, and identification of risk factors associated with stent failure.

Patients and methods

All patients with MUO who were arranged to have Resonance metallic ureteric stent insertion at two university hospitals were included in this cohort study, starting from June 2011 to July 2016. Data were retrieved retrospectively. The primary outcome was the total duration of stent patency before stent failure due to malignant disease progression. Stent failure was defined as ureteric obstruction identified on imaging (functional radioisotope scan or antegrade pyelogram), acute renal failure resolved by subsequent percutaneous nephrostomy, or any other cause requiring stent removal prematurely. Secondary outcomes were identification of factors associated with stent failure, grade III or above complication, and development of a risk-adopted model to predict metallic ureteric stent patency rates in MUO patients. Median duration of functioning metallic ureteric stent was determined with Kaplan-Meier survival curve.

Results

A total of 124 renal units in 95 patients with MUO were eligible for the study, with a median follow-up period of 22.9 months. About 106 (85.5%) renal units had successful metallic stent insertion, of whom 41 (33.1%) renal units ultimately progressed to ureteric obstruction despite the metallic stents, and required subsequent insertion of nephrostomies. Median duration of functioning metallic ureteric stents was 25 months. Female gender (HR 3.0, 95% CI: 1.3-7.2, P = .014) and suspicious bladder lesion (HR 2.9, 95% CI: 1.4-6.2, P = .005) were independent risk factors for stent failure, respectively. Stratifying patients into low (0 risk factor), intermediate (1 risk factor), and high (2 risk factors) risk groups, we found that this could predict the duration of stent patency in MUO with the metallic stents. (Low risk: 30.3 months vs intermediate group: 17.8 months vs high risk: 4.9 months, P < .001).

Conclusion

Resonance metallic ureteral stents are able provide a median of 25 months of ureteric drainage in patients with MUO. Determining whether a patient has one or both risks factors (female gender and bladder lesion) will allow one to estimate the duration of metallic stent patency, which in turn may aid in determining cost-effectiveness in individual patients.

Management and treatment options when facing malignant ureteral obstruction

Malignant ureteral obstruction is an unfortunate finding that can be caused by a wide-ranging number of malignancies with a prognosis of limited survival. Given its presentation and progression, it can be refractory to treatment by traditional single polymeric ureteral stents. With a higher failure rate than causes of benign ureteral obstruction, a number of other options are available for initial management, as well as in cases of first-line therapy failure, including tandem stents, metallic stents, percutaneous nephrostomies and extra-anatomic stents. We reviewed the literature and carried out a PubMed search including the following keywords and phrases: "malignant ureteral obstruction," "tandem ureteral stents," "metallic ureteral stents," "resonance stent," "metal mesh ureteral stents" and "extra-anatomic stents." The vast majority of studies were small and retrospective, with a large number of studies related to metallic stents. Given the heterogenous patient population and diversity of practice, it is difficult to truly assess the efficacy of each method. As there are no guidelines or major head-to-head prospective trials involving these techniques, it makes practicing up to the specific provider. However, this article attempts to provide a framework with which the urologist who is presented with malignant ureteral obstruction can plan in order to provide the individualized care on a case-by-case basis. What is clear is that prospective, randomized clinical trials are necessary to help bring evidence-based medicine and guidelines for patients with malignant ureteral obstruction.

Malignant ureteral obstruction: experience and comparative analysis of metallic versus ordinary polymer ureteral stents

BACKGROUND

To study the outcome and experience of using metallic stents in treating patients with malignant ureteral obstruction (MUO).

METHODS

Seventy-six patients with MUO were assigned to the metallic stent group (MSG) or the ordinary polymer stent group (OPSG) according to the different materials. The success rate of the operation, duration of operation, patency rate serum creatinine values ,postoperative complications and QOL scores were compared between the two groups.

RESULTS

In the OPSG and MSG, the success rates of the operation were 95.5% and 96.9%, respectively, and the durations of the operation were 20.6 ± 2.2 min and 50.9 ± 10.3 min (P < 0.01), respectively. There was no significant difference between the groups in serum creatinine values at 3 days after the operation (P > 0.05); however, the creatinine values at 3 days after the operation decreased significantly compared with those before the operation (P < 0.01). In the OPSG, there was no significant difference in creatinine values between 3 days and 6 months after operation, while the creatinine values 1 year after operation were increased significantly compared to those at 3 days after the operation (P < 0.05). In the MSG, there was no significant difference among creatinine values at different intervals (P > 0.05). The total rate of post-procedural complication was lower in the MSG than that in the OPSG(P < 0.05). There was no significant difference in the QOL score between the two groups before the operation (P > 0.05); however, the QOL scores at 6 months and 1 year after the operation were higher in the MSG than that in the OPSG(P < 0.05). In the MSG, there was no significant difference in the QOL score between preoperation and 6 months after surgery. Similarly, there was also no difference in the QOL score between 6 months after surgery and 1 year after surgery(P > 0.05). On the contrary, the differences of QOL score in the OPSG group were much significant between disparate time intervals (P < 0.05).

CONCLUSIONS

For patients with MUO who require long-term retention of the stent, metallic stents with longer indwelling time are superior to ordinary polymeric stents.

Application of metallic ureteral stents in gynecological malignancies: a literature review

Ureteral obstruction caused by extrinsic compression from advanced pelvic malignancies are not unusual in urology, with gynecological origin being the most common. As minimally invasive treatments for malignant ureteral obstruction (MUO), metallic ureteral stents have been promoted to provide long-lasting urinary patency and overcome the inherent limits of traditional double-J stents. In this review, we demonstrated three types of frequently used metal stents, including coiled stents, self-expendable stents and thermo-expendable stents. The Wallstent presented discrepant patency rates ranging from 6% to 100%, along with a high occlusion rate. The Memokath 051 stent showed satisfactory patency rates, often > 90%, but also a specific higher migration rate. The Resonance stent provided overall promising results with published success rates ranging from 20% to 100%, which on the whole remains relatively high. The long-term effectiveness rendered metal stents as viable options for managing MUO.

Metallic Ureteric Stents in Malignant Ureteric Obstruction: A Systematic Review

The effectiveness of metallic stents in the management of malignant ureteric obstruction is unclear. This systematic review evaluates the use of 4 commercially available metallic stents (Resonance, Memokath 051, Uventa, and Allium URS). Twenty-one studies met eligibility criteria. Overall success rates ranged from 88% for the Allium stent to 65% for Memokath 051. Resonance demonstrated the lowest migration rate (1%). Uventa had the lowest obstruction rate (6%). Metallic ureteric stents offer a viable alternative in the management of malignant ureteric obstruction. Further high quality studies are required to assess cost effectiveness and refine specific indications based on etiology and level of the ureteric obstruction.

Application of resonance metallic stents for malignant ureteral obstruction

Purpose: To determine the effectiveness of the Resonance metallic stent in treating malignant ureteral obstruction (MUO) and clarify the risk factors that lead to stent failure. Material and methods: We retrospectively identified and analyzed the records of patients who had MUO and underwent placement of Resonance metallic stents from November 2014 to June 2017 in our hospital. Stent failure was defined as unexpected interventions including stent exchange, need of percutaneous nephrostomies (PCN) or ureterocutaneostomy. Results: A total of 22 stents were placed in 14 patients with MUO. The median follow-up was 145 days (4.8 months) and the maximum duration of stenting was 21.3 months. The technique success rate was 100%. Two patients experienced early postoperative increasing creatinine with oliguria but only one of them failed to achieve primary patency. The overall success rate was 90% (9/10). Conclusion: Resonance metallic stent is a safe and effective treatment for MUO and can maintain durable patency over 12 months. Preoperative urinary tract infection (UTI) and tumor invasion into the bladder are considered as risk factors of stent blockage and failure. Early postoperative elevated creatinine oliguria, suggestive with intrarenal and prerenal disease, should not be deemed to be stent failure.

Risk Factors for Primary Failure of Metallic Ureteral Stents: Experience from a Tertiary Center

Introduction: We provide primary patency rate of metallic ureteral stents in cancer patients and investigate the factors affecting primary patency. Methods: All cancer patients who had received metallic stents for malignant ureteral obstruction between July 2009 and November 2012 in our institute were included. No patients were excluded. Patient profiles, imaging studies, and laboratory data were collected. Patient profiles included age, gender, body height, body weight, body mass index, cancer types, treatment for cancer, response to cancer treatment, methods of stent insertion, and prior ordinary stents. Imaging studies included renal ultrasonography, antegrade pyelography, CT, and MRI. Laboratory data included urinalysis, urine culture, and serum creatinine. Complications were defined according to the Clavien-Dindo classification. Primary patency was defined as a complete resolution or downgrading of hydronephrosis shown by imaging studies or success in the removal of a preexisting nephrostomy tube; otherwise the procedure was considered a primary failure. The primary endpoint was the primary patency rate of the stents. The secondary endpoints were risk factors for primary stent failure. Results: A total of 124 stents were inserted into 96 patients with malignant ureteral obstruction. There were no grade 3/4 complications. The overall primary patency rate was 87.9% (109/124). In univariate analysis, antegrade insertion (OR = 24.15, p-value = 0.0086) and urinary tract cancer (OR = 4.18, p-value = 0.0164) were significantly associated with primary failure. Those with prior ordinary stents (OR = 0.20, p-value = 0.0158) or response to cancer treatment (OR = 0.25, p-value = 0.0228) were associated with stent patency. In multivariate analysis, antegrade insertion (OR = 22.04, p-value = 0.0041) and response to cancer treatment (OR = 0.15, p-value = 0.01081) remained significant factors. Conclusions: In this large cohort of cancer patients requiring urinary diversion to preserve renal function, several factors were associated with the success rate of metallic stents.

Stents for malignant ureteral obstruction

Malignant ureteral obstruction can result in renal dysfunction or urosepsis and can limit the physician's ability to treat the underlying cancer. There are multiple methods to deal with ureteral obstruction including regular polymeric double J stents (DJS), tandem DJS, nephrostomy tubes, and then more specialized products such as solid metal stents (e.g., Resonance Stent, Cook Medical) and polyurethane stents reinforced with nickel-titanium (e.g., UVENTA stents, TaeWoong Medical). In patients who require long-term stenting, a nephrostomy tube could be transformed subcutaneously into an extra-anatomic stent that is then inserted into the bladder subcutaneously. We outline the most recent developments published since 2012 and report on identifiable risk factors that predict for failure of urinary drainage. These failures are typically a sign of cancer progression and the natural history of the disease rather than the individual type of drainage device. Factors that were identified to predict drainage failure included low serum albumin, bilateral hydronephrosis, elevated C-reactive protein, and the presence of pleural effusion. Head-to-head studies show that metal stents are superior to polymeric DJS in terms of maintaining patency. Discussions with the patient should take into consideration the frequency that exchanges will be needed, the need for externalized hardware (with nephrostomy tubes), or severe urinary symptoms in the case of internal DJS. This review will highlight the current state of diversions in the setting of malignant ureteral obstruction.

Metallic stents in the management of ureteric strictures

Management of ureteric strictures is a challenging task. Subtle presentation, silent progression and complex aetiology may delay diagnosis. A wide range of available treatment options combined with the lack of adequate randomised trials has led to the introduction of personal bias in the management of this difficult group of patients. Metallic ureteric stents offer an alternative to the conventional treatment modalities. A review of the currently available metallic stents and their role in the long-term management of ureteric strictures is presented. Materials used in the manufacture of indwelling urological devices are evolving all the time. Improved endo-urological techniques combined with new devices made from better compounds will continue to improve patient experience.