Efficacy and Safety of a Novel, Double-Layered, Coated, Self-Expandable Metallic Mesh Stent (Uventa™) in Malignant Ureteral Obstructions

Technical Notes on Fluoroscopy-Guided Removal of Metallic Ureteral Stents

This manuscript describes various techniques for fluoroscopy-guided removal of metallic ureteral stents. Fifteen patients underwent 17 fluoroscopy-guided removal procedures of 22 metallic ureteral stents. The simple or modified snare or retrieval hook technique was primarily used for antegrade access, whereas the loop snare technique was primarily used for retrograde access. Overall 64.7% of the stents were removed using the initial retrieval technique, and 82.4% were removed using an adjunct technique. Procedure-related complications included hematuria in 41.2% of cases and resolved spontaneously in all patients. Fluoroscopy-guided removal of metallic ureteral stents is safe and effective.

Comparison of a covered metallic ureteral stent and a double-J stent for malignant ureteral obstruction in advanced gastric cancer

AIM

To compare the patency and safety of covered metallic stents (CMS) and the double-J stent (DJS) for treating malignant ureteral obstruction (MUO) in advanced gastric cancer (AGC).

MATERIALS AND METHODS

Between 2016 and 2018, the medical records of 61 patients (84 ureters; CMS, 39 patients, 54 ureters; DJS, 22 patients, 30 ureters) with MUO caused by AGC were reviewed retrospectively. The Kaplan-Meier method and log-rank test were used to evaluate differences of primary or assisted primary patency between groups. Cox regression was conducted separately for early (within 7 days) and late (after 7 days) primary patency.

RESULTS

Technical success of CMS placement was 100% (54/54) and 96.8% (29/30) for DJS (p=0.357). The cumulative stent patency rates at 1, 3, 6, and 12 months were 77%, 74%, 70%, and 70%, in the CMS group and 72%, 60%, 53%, and 26%, in the DJS group. Apart from the period within 7 days (p=0.784), primary patency was consistently higher in the CMS group when compared to the DJS group over the entire follow-up period (p=0.034). Assisted primary patency was consistently higher in the CMS group than in the DJS group over the entire follow-up period (p=0.001). The CMS group was more likely to have complications than the DJS group (48.1% versus 16.7%, p=0.004). Complications were minor, self-limiting events such as haematuria/haematoma.

CONCLUSION

CMS had better late patency and assisted primary patency than DJS. Procedure-related minor complications more frequently occurred with CMS.

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.

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.

Ureteric stents: Overview of current clinical applications and economic implications

Ureteric stents are one of the most crucial tools used for various clinical conditions in the urological field. Placement of a ureteric stent, for short- or long-term use, remains one of the commonest urological interventional procedures. In the past few decades, ureteral stents have undergone notable technological advancements. However, an ideal stent without significant side-effects is yet to be engineered. Indwelling ureteric stents are often accompanied by physical distress to the patient and clinical complications, such as bacterial adhesion, encrustation, malpositioning, stent fracture and forgotten stent syndrome, that influence patients' health-related quality of life. In the market, different stent types are available, designed to reduce infections, and improve patient symptoms and tolerance. In this review, we have emphasized the recent developments that have taken place in stent design, size, materials and coating. This overview looks at current practices and problems related to stents, along with clinical and economic considerations. Few trial studies have been enumerated in the context of utilization of a ureteral stent symptom questionnaire and various stent models to compare their effects in patients.

Long-term outcomes of two types of metal stent for chronic benign ureteral strictures

BACKGROUND

We aimed to compare the results of long-term use of two types of metal stent for chronic benign ureteral strictures.

METHODS

Our study included 46 ureter units (UUs) that underwent metal stent placement from 2010 to 2017. We included benign ureteral strictures causes by variety reasons that could not be solved by other treatment and malignant obstructions were excluded. Covered mesh stent (Uventa™) and a thermo-expandable stent (Memokath 051™) were used. Primary success was defined as maintaining patency without procedures and overall success was defined as maintaining patency with additional procedures.

RESULTS

We placed covered mesh stents in 25 UUs and thermo-expandable stents in 21 UUs. The mean follow-up duration of each stent was 41.4 ± 23.1 and 34.4 ± 16.5 months (p = 0.250). In the first year of stent insertion, primary success was achieved in 54.9 and 70.4% (p = 0.204). Overall success was achieved in 78.7 and 75.4% in same duration, respectively (p = 0.586). Longer stent placement had positive predictive value on both success rates (HR = 0.185, p = 0.047 and HR = 0.111, p = 0.018). Prior radiation therapy and non-pelvic ureter stricture both adversely affected the overall success rate (HR = 5.412, p = 0.048 and HR = 4.203, p = 0.030). Previous PCN status had negative predictive value for both success rates (HR = 4.014, p = 0.003 and HR = 3.064, p = 0.035).

CONCLUSIONS

The treatment outcomes of two types of metal stent were comparable, especially in the first year of stent insertion.

Self-Expandable Covered Metallic Stent (UVENTA) to Treat a Ureteral Stricture After Renal Transplant: A Case Report

We present the use of a self-expandable covered metallic stent (UVENTA; TaeWoong Medical, Gyeonggi-do, South Korea) to treat a ureteral stricture after kidney transplant. In this report, we describe the procedure and short-term outcomes of a patient with a recurrent distal stricture who did not respond to percutaneous balloon dilation. We decided to place this temporary stent as an alternative to complex surgery. The aim of the procedure was to get a chronic dilation of the stricture up to 7 mm to stabilize the fibrotic tissue. The procedure was easily and quickly performed by an antegrade and retrograde combined approach. The postoperative course was uneventful. The stent was left in situ for 7 months. No complications were noted, and the renal function remained stable. The stent was easily removed, and 5 months later there were no signs of recurrence. The UVENTA device was shown to be an easy, safe, and effective minimally invasive treatment for ureteral stricture in renal transplant. Proper permanence time and long-term results need to be explored.

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.

Comparison of single and tandem ureteral stenting for malignant ureteral obstruction: a prospective study of 104 patients

OBJECTIVES

The aim of this study was to compare single and tandem ureteral stenting in the management of malignant ureteral obstruction (MUO).

METHODS

Our hospital's institutional review board approved this prospective study. Between November 2014 and June 2017, single ureteral stenting was performed in 56 patients (94 renal units) and tandem ureteral stenting in 48 patients (63 renal units) for MUO. A comparative analysis of the technical success rate, patient survival, stent patency, and complications was performed.

RESULTS

Similar demographic data were observed in patients receiving either single or tandem ureteral stenting. The technical success rate was 93.6% (88/94) for single ureteral stenting and 95.2% (60/63) for tandem ureteral stenting. There was no difference in overall survival between patients receiving single or tandem ureteral stenting (p = 0.41), but the duration of stent patency in tandem ureteral stenting was significantly longer (p = 0.022). The mean patency time was 176.7 ± 21.3 days for single ureteral stenting, and 214.7 ± 21.0 days for tandem ureteral stenting. The complications of ureteral stenting were urinary tract infection (n = 18), lower urinary tract symptoms (n = 5), haematuria (n = 3), and stent migration (n = 1).

CONCLUSIONS

Tandem ureteral stenting is a safe and feasible treatment for MUO, and had better efficacy compared to single ureteral stenting.

KEY POINTS

• Ureteral stenting is an established treatment for the management of malignant ureteral obstruction (MUO) • Prospective single-centre study showed that tandem ureteral stenting is a safe and feasible treatment for MUO • Tandem ureteral stenting provides longer stent patency compared to single ureteral stenting in patient with MUO.

A Prospective Randomized Comparison of a Covered Metallic Ureteral Stent and a Double-J Stent for Malignant Ureteral Obstruction

Objective

To compare the safety and efficacy between a covered metallic ureteral stent (CMS) and a double-J ureteral stent (DJS) for the treatment of a malignant ureteral obstruction (MUO).

Materials and Methods

Nineteen patients (seven men and 12 women; mean age, 53.4 years) were randomly assigned to the CMS (n = 10) or DJS (n = 9) group. The following were compared between the two groups: technical success, i.e., successful stent placement into desired locations; stent malfunction; stent patency, i.e., no obstruction and no additional intervention; complications; and patient survival.

Results

The technical success rate was 100% in all 10 and 12 ureteral units in the CMS and DJS groups, respectively. During the mean follow-up period of 253.9 days (range, 63–655 days), stent malfunction was observed in 40.0% (4/10) and 66.7% (8/12) in the CMS and DJS groups, respectively. In the per-ureteral analysis, the median patency time was 239.0 days and 80.0 days in the CMS and DJS groups, respectively. The CMS group yielded higher patency rates compared with the DJS group at three months (90% vs. 35%) and at six months (57% vs. 21%). The overall patency rates were significantly higher in the CMS group (p = 0.041). Complications included the migration of two metallic stents in one patient in the CMS group, which were removed in a retrograde manner. The two patient groups did not differ significantly regarding their overall survival rates (p = 0.286).

Conclusion

Covered metallic ureteral stent may be effective for MUO.

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.

The effectiveness of ureteric metal stents in malignant ureteric obstructions: A systematic review

Objective

To review the literature on the effectiveness, safety and long-term patency of ureteric metal mesh stents (MSs), as a variety of MSs have been used for managing malignant ureteric obstruction over the last three decades.

Materials and methods

A systematic review using the search string; Ureter∗ AND (stent OR endoprosthesis) AND metal∗ was conducted on PubMed, Scopus, Web of science and Cochrane Library online databases in May 2016. Prospective, retrospective, and comparative studies including MSs were included. The primary endpoint was the patency rate and the secondary endpoint was complications.

Results

In all, 324 publications were screened and 31 articles were included in the systematic review; 21 prospective and 10 retrospective studies. These studies reported the effectiveness of specific MSs in population studies, in comparative studies among different MSs, as well as among MSs and JJ stents. It should be noted that all comparative studies were retrospective.

Conclusion

The experiences with vascular MSs, such as the Wallstent™ (Boston Scientific/Microvasive, Natick, MA, USA), were related to high occlusion rates, due to endoluminal hyperplasia, and long-term disappointing patency. The use of covered MSs designed for the vascular system was also unfavourable. The Memokath 051™ (PNN Medical A/S, Kvistgaard, Denmark) had better patency rates, but also higher migration rates. The long-term results were acceptable and rendered the Memokath 051 as a viable option for the management of malignant ureteric obstruction. The Uventa™ (Taewoong Medical, Seoul, Korea) and Allium™ (Allium Medical Solutions Ltd, Caesarea, Israel) MSs, specifically designed for ureteric placement, provided promising results. Nevertheless, the wide acceptance of these MSs would require well-designed clinical studies and long-term follow-up.

The thermoexpandable nitinol stent: a long-term alternative in patients without nephropathy or malignancy

OBJECTIVE

The aim of this study was to investigate the long-term outcome of a thermoexpandable nickel-titanium nitinol ureteral stent (Memokath 051™) and to identify individual risk factors for failure.

MATERIALS AND METHODS

This retrospective single-centre study included 125 patients who underwent implantation of the self-expandable Memokath 051 stent. Complications, indwelling time and reason for explantation were recorded. Analyses were stratified by gender, age, body mass index, American Society of Anesthesiologists score, estimated glomerular filtration rate (eGFR), side, localization and cause of the stricture.

RESULTS

In total, 91 out of 125 patients (73%) were available for analysis. Median indwelling time was 355 days (range 7-2125 days). Most stents were removed because of dislocation (42%) or occlusion (40%). Stent removal was rarely performed because of infection (3%). Patients with sufficient renal function (eGFR ≥60 ml/min/1.73 m²) showed increased indwelling times compared with those with nephropathy (386 vs 317 days; p < 0.01). Patients with active malignant disease showed reduced patency time compared with strictures of benign origin (455 vs 190 days; p < 0.01).

CONCLUSIONS

This thermoexpandable nitinol stent offers safe mid-term treatment of ureteric strictures, especially in patients without active malignancy and with good renal function.

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.

Early Application of Permanent Metallic Mesh Stent in Substitution for Temporary Polymeric Ureteral Stent Reduces Unnecessary Ureteral Procedures in Patients With Malignant Ureteral Obstruction

OBJECTIVE

To identify risk factors for metal stent failure in patients who received polymeric double J (PDJ) ureteral stents for malignant ureteral obstructions (MUOs) and review our clinical experiences using a ureteral metallic stent.

PATIENTS AND METHODS

Patients who underwent metallic stent placement to replace a double J ureteral stent for nonurological MUO between January 2011 and February 2014 were included. The collected data included gender, age, laterality, cause of obstruction, PDJ ureteral stenting duration, immediate success of the metal stent, and additional procedures to relieve obstruction after metal stenting (eg, additional metal stenting or percutaneous nephrostomy (PCN) indwelling catheter placement). Cox regression tests were used for the statistical analyses.

RESULTS

In this analysis 40 ureteral units were included. There was no initial technical failure. However, 9 (22.5%) units required additional procedures due to de novo ureteral obstruction, including additional indwelling metal stents (7.5%), additional PDJ stenting (10%), or indwelling percutaneous nephrostomy (5%). Univariate and multivariate analyses revealed that the duration of previous PDJ ureteral stenting was an independent prognostic factor for predicting ureteral metal stent failure (hazard ratio = 1.063, 95% confidence interval = 1.004-1.125; P = .037).

CONCLUSION

Long-term indwelling of a PDJ ureteral stent increases the risk of additional management for de novo ureteral stricture after ureteral metal stent replacement for nonurological MUO. Our data suggest that careful patient selection and counseling for those at high risk are needed when metal stent replacement is considered for patients with long-term PDJ ureteral stents for MUO.

Comparison of efficacy and safety between a segmental thermo-expandable metal alloy spiral stent (Memokath 051) and a self-expandable covered metallic stent (UVENTA) in the management of ureteral obstructions

OBJECTIVE

To determine the efficacy and safety of the Memokath 051™ (PNN Medical, Glostrup, Denmark) and UVENTA™ (Taewoong Medical, Seoul, Korea) metal stents, we reviewed our experience with these two metallic ureteral stents for treating benign and malignant ureteral obstructions.

SUBJECTS AND METHODS

Twenty-seven patients who received treatment with metallic ureteral stents (Memokath 051, 10 patients; UVENTA, 17 patients) from November 2011 to May 2013 at our institution were identified and analyzed. We conducted a comparative analysis of the causes of obstruction, technical/clinical success rate, cause of failure, and complications.

RESULTS

No difference was observed between the two metallic stents for the causes of benign and malignant ureteral obstructions (P=.073). The Memokath 051 and the UVENTA were inserted successfully in all ureters using a retrograde technique. The mean follow-up was 13.6 months for Memokath 051 and 12 months for UVENTA (P=.244). The clinical success rate of the UVENTA was higher than that of Memokath 051 (82.4% versus 42.9%; P=.031). The causes of failure were obstruction by tumor progression (n=2) and stent migration (n=6) in cases that received Memokath 051 and stent migration (n=1) and obstruction by mucosal hyperplasia (n=2) in UVENTA. The complications caused by Memokath 051 were intermittent flank pain (n=1) and acute pyelonephritis (n=1), whereas those of UVENTA were intermittent flank pain (n=1), gross hematuria (n=1), and acute pyelonephritis (n=1).

CONCLUSIONS

The UVENTA achieved a higher clinical success rate than the Memokath 051. Our study demonstrated that the UVENTA is safe and effective in the management of benign and malignant ureteral obstruction. The complications were similar between the two metallic stents.

Surgical emergencies in oncology

An oncologic emergency is defined as an acute, potentially life threatening condition in a cancer patient that has developed as a result of the malignant disease or its treatment. Many oncologic emergencies are signs of advanced, end-stage malignant disease. Oncologic emergencies can be divided into medical or surgical. The literature was reviewed to construct a summary of potential surgical emergencies in oncology that any surgeon can be confronted with in daily practice, and to offer insight into the current approach for these wide ranged emergencies. Cancer patients can experience symptoms of obstruction of different structures and various causes. Obstruction of the gastrointestinal tract is the most frequent condition seen in surgical practice. Further surgical emergencies include infections due to immune deficiency, perforation of the gastrointestinal tract, bleeding events, and pathological fractures. For the institution of the appropriate treatment for any emergency, it is important to determine the underlying cause, since emergencies can be either benign or malignant of origin. Some emergencies are well managed with conservative or non-invasive treatment, whereas others require emergency surgery. The patient's performance status, cancer stage and prognosis, type and severity of the emergency, and the patient's wishes regarding invasiveness of treatment are essential during the decision making process for optimal management.