The resonance® metallic ureteral stent in the treatment of malignant ureteral obstruction: a prospective observational study

Establishment of an artificial urine model in vitro and rat or pig model in vivo to evaluate urinary crystal adherence

The current study aimed to establish an experimental model in vitro and in vivo of urinary crystal deposition on the surface of ureteral stents, to evaluate the ability to prevent crystal adhesion. Non-treated ureteral stents were placed in artificial urine under various conditions in vitro. In vivo, ethylene glycol and hydroxyproline were administered orally to rats and pigs, and urinary crystals and urinary Ca were investigated by Inductively Coupled Plasma-Optical Emission Spectrometer. in vitro, during the 3- and 4-week immersion periods, more crystals adhered to the ureteral stent in artificial urine model 1 than the other artificial urine models (p < 0.01). Comparing the presence or absence of urea in the composition of the artificial urine, the artificial urine without urea showed less variability in pH change and more crystal adhesion (p < 0.05). Starting the experiment at pH 6.3 resulted in the highest amount of crystal adhesion to the ureteral stent (p < 0.05). In vivo, urinary crystals and urinary Ca increased in rat and pig experimental models. This experimental model in vitro and in vivo can be used to evaluate the ability to prevent crystal adhesion and deposition in the development of new ureteral stents to reduce ureteral stent-related side effects in patients.

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.

Malignant upper urinary tract obstruction in cancer patients: A systematic review

Objective

To systematically summarise the current clinical evidence for de novo malignant upper urinary tract obstruction treatment with a focus on standards of reporting, patient outcomes and future research needs.

Methods

This review protocol was published via PROSPERO (CRD42022341588). OVID MEDLINE (R), EMBASE, Cochrane Central Register of Controlled Trials-CENTRAL were searched up to June 2022 in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-analyses. Prospective and retrospective studies were included.

Results

Of 941 articles identified, 82 with 8796 patients were eligible for inclusion.Most studies in the published literature are retrospective and investigate heterogenous malignancies. Percutaneous nephrostomy and ureteric stenting are the most studied interventions. Few studies describe the outcomes from no intervention or investigate patient perspectives. Overall reported median survival after intervention was around 11.7 months. A lack of standardised reporting of outcomes was evident.

Conclusions

Malignant upper urinary tract obstruction is an important clinical condition affecting patients globally. Overall survival after intervention appears poor however the current evidence base has significant limitations due to studies of low methodological quality and the lack of a standardised framework for reporting outcomes.We have provided a pragmatic framework for future studies based on the review to ensure a uniform methodology is utilised moving forward.

Risk factors for migration of retrievable covered expandable metallic stent in patients with persistent benign ureter strictures

PURPOSE

The purpose of this study is to evaluate the incidence, risk factors, and salvage management of retrievable covered expandable metallic stent (RCEMS) migration in patients with persistent benign ureter strictures.

MATERIALS AND METHODS

A retrospective study was performed on 117 consecutive patients who underwent implantation of RCEMS. Univariate and multivariate analyses were used to identify prognostic factors for stent migration, including stricture location and length, hydronephrosis-cortex ratio, ureteral dilation, and the diameter of the narrowest portion of the stricture.

RESULTS

Stent migration occurred in 22 (19.5%) of 113 patients who met inclusion criteria. Of the 22 patients, 16 (72.7%) had ordinary ureteral stricture, 3 (13.6%) had stricture in transplanted kidneys, and 3 patients (13.6%) had ureter stricture in orthotopic neobladders. The mean creatinine for the entire cohorts showed significant improvement (p = 0.038). Multivariate analysis identified the following prognostic factors for migration: distal ureteral stricture (p = 0.006), patients who underwent balloon dilation (p = 0.003), hydronephrosis-cortex ratio ≧10 (p = 0.017), larger diameter of wasting of RCEMS (p < 0.001), and patients with a shorter stricture length (p = 0.006). Salvage management was required in 4 of the 22 patients. The strictures in the remaining 18 patients improved with observation.

CONCLUSIONS

Stent migration is more likely to occur in patients with the five prognostic factors mentioned above. Our study developed a nomogram to predict stent migration in patients with ureteral strictures treated using RCEMS.

Canine Prostate Cancer: Current Treatments and the Role of Interventional Oncology

Prostate carcinoma is one of the most common cancers worldwide in men, with over 3 million men currently living with prostate carcinoma. In men, routine screening and successful treatment schemes, including radiation, prostatectomy, or hormone therapy, have allowed for high survivability. Dogs are recognized as one of the only mammals to spontaneously develop prostate neoplasia and are an important translational model. Within veterinary medicine, treatment options have historically been limited in efficacy or paired with high morbidity. Recently, less invasive treatment modalities have been investigated in dogs and people and demonstrated promise. Below, current treatment options available in dogs and people are reviewed, as well as a discussion of current and future trends within interventional treatment for canine PC.

Malignant ureteral obstruction: comparison of metallic, 8 French and 6 French ureteric stents after failure of initial ureteric stent

PURPOSE

Malignant ureteric obstruction is a significant management challenge. The failure of ureteric stents often leads to long-term nephrostomy tubes. This is delayed for as long as possible due to its' associated morbidity. Several types of ureteric stents are available, however there is little evidence demonstrating which stents are better for preventing progression to nephrostomy tubes. This study looked to determine whether a new 6 French (Fr) polymer stent, 8Fr polymer stent or metallic stent achieved a longer functional duration once the initial polymer ureteric stent failed.

METHODS

A retrospective, longitudinal study was performed at a single tertiary institution. All patients who underwent ureteric stenting with a 6Fr polymer stent for malignancy between 2010 and 2020 were included. Patients were followed up until death with ureteric stent in situ or permanent nephrostomy tube insertion.

RESULTS

A total of 46 patients (66 ureters) had ureteric stents inserted for malignancy. From initial ureteric stent failure, 10 stents were changed to a new 6Fr polymer stent, 42 were changed to an 8Fr polymer stent and 14 were changed to a Resonance® 6Fr metallic stent. The Resonance 6Fr metallic stent had the longest median functional duration of 14 months (p = 0.012).

CONCLUSION

Resonance® 6Fr metallic stents appear to have a significantly longer functional duration than a new 6Fr polymer stent or 8Fr polymer stent, which may allow patients to enjoy a better quality of life and delay permanent nephrostomy tube insertion.

It is Possible to Reduce Ureteral Stent Clogging and Stent-Related Symptoms to Soothe the Pain of the Patient: A Case Report

Introduction

Ureteral stent obstruction hinders the management of malignant diseases. Adequate stent insertion through an obstructed ureter does not necessarily guarantee renal decompression and stent-related symptoms adversely affect patient comfort. There are two major problems associated with ureteral stents: obstruction and intolerance to the stents.

Case Presentation

A 45-year-old woman was treated for cervical cancer with metastatic lymph nodes and ureteral obstruction with chemotherapy, radiotherapy, immunotherapy, and bilateral retrograde stenting. After recurrent stent obstruction, stent replacement was attempted more than 18 times over two years. In addition, stent-related symptoms adversely affected patient comfort. The patient was finally fitted with Superglide 8-French reinforced ureteral stents. Their replacement every six months was viewed by the patient as a relief compared to the all too frequent replacement of the previous stents. Moreover, the customized changes in the shape of Superglide stents improved patient comfort.

Discussion

Recent publications tend to indicate that large-lumen ureteral stents are most likely to remain permeable over time. Various modifications of the bladder or endo-ureteral part of double-pigtail stents have been increasingly reported, with the aim of improving their tolerance while maintaining effective drainage.

Conclusion

Adaptation of the internal lumen and shape of stents to the characteristics of the tumor and patient measurements appears to be important for increasing the drainage and tolerance of ureteral stents. The top priority for future ureteral stents suitable for malignant diseases should be to integrate these characteristics based on state-of-the-art data.

Effectiveness of Double-J Metallic Mesh Ureteral Stents for Malignant Ureteral Obstruction: A Retrospective Study

BACKGROUND/AIM

Malignant ureteral obstruction is associated with high rates of failure with traditional ureteral stents. Double-J metallic mesh ureteral stent is one of the latest options for treating malignant ureteral obstruction. However, data regarding the efficacy of using this stent in this context are limited. Thus, we retrospectively investigated the efficacy of this stent.

PATIENTS AND METHODS

We retrospectively analyzed the records of all patients who required double-J metallic mesh ureteral stent placement for malignant ureteral obstruction at Ishikawa Prefectural Central Hospital (Kanazawa, Japan) between October 2018 and April 2022. Primary stent patency was defined as complete or partial resolution of hydronephrosis as shown by imaging studies or successful removal of a preexisting nephrostomy tube. Stent failure was defined as unplanned stent exchange or nephrostomy tube placement for signs or symptoms of recurrent ureteral obstruction. A competing risk model was used to estimate the cumulative incidence of stent failure.

RESULTS

Double-J metallic mesh ureteral stents were placed in 63 ureters of 44 patients (13 males, 31 females). The median age of patients was 67 years (range=37-92 years). There was no grade 3 or higher complications. The overall primary patency rate was 95% (60 ureters). Stent failure occurred in seven patients (11%) during follow-up. The cumulative incidence of stent failure at 12 months after placement was 17.3%.

CONCLUSION

Double-J metallic mesh ureteral stent is a safe, simple, and promising treatment option for malignant ureteral obstruction.

Clinical factors predicting ureteral stent failure in patients with external ureteral compression

Double-J stent (DJ) placement is usually the treatment of choice for relieving external compression of the ureter. However, in some cases DJ function may become impaired and a percutaneous nephrostomy (PCN) may be required. Previous studies have reported different predictive factors for choosing PCN or DJ insertion as the initial treatment. In this study, we analyzed the risk factors for DJ failure in patients with external ureteral compression. Our results showed that the patients with moderate and severe hydronephrosis (p-value = 0.0171 and 0.0249, respectively), preexisting pyuria (p-value = 0.0128), or lower ureter obstruction (p-value = 0.0305) were more prone to DJ laterality. Age was also an important predictor. Urologists should pay more attention to these patients and consider PCN as the initial treatment.

Patency period of a metallic ureteral stent and its determinants in patients with malignant ureteral obstruction: a prospective review

Background

Malignant ureteral obstruction caused by extrinsic compression of a primary malignant tumour or by metastatic disease is an indicator of poor prognosis with a median life expectancy of about one year. We examined clinical outcomes following Resonance Metallic Ureteral Stent (Cook Medical, Bloomington, IN) placement in patients with malignant ureteral obstruction.

Methods

This was a prospective study of patients with malignant ureteral obstruction who underwent Resonance Metallic Ureteral Stent placement from April 2016 to March 2021. We registered 21 patients (27 collecting systems) with malignant ureteral obstruction and observed them prospectively. The patients first underwent polymer ureteral stent placement followed by replacement with a metallic ureteral stent one month later. Primary outcome was the metallic ureteral stent patency period based on both serum creatinine and the level of hydronephrosis; secondary outcomes were factors affecting patency period and stent-related complications such as symptoms of obstruction (flank pain), bladder irritation, haematuria, and urinary tract infection (presence or absence of fever).

Results

The study comprised 21 patients (six men, 15 women) with a mean age of 72 years. The median stent patency period in days was not available (NA) (95% CI 210–NA) due to the inability to extract this value from the Kaplan–Meier curve because the event rate did not reach 50%, and the one-year patency rate was 59.2% (95% CI 23.2–82.9). A normal serum creatinine (0.65 to 1.07 mg/dL for men and 0.46 to 0.79 mg/dL for women) one week after polymer ureteral stent placement was a significant factor affecting the long-term metallic ureteral stent patency period. There were no major complications.

Conclusion

The Resonance Metallic Ureteral Stent was effective and safe for patients with malignant ureteral obstruction. A normal serum creatinine level one week after placement of a polymer ureteral stent may predict a longer patency period of metallic ureteral stents in patients with malignant ureteral obstruction.

Physical Properties of Electropolished CoCrMo Alloy Coated with Biodegradable Polymeric Coatings Releasing Heparin after Prolonged Exposure to Artificial Urine

In this study, we aimed to determine the effect of long-term exposure to artificial urine on the physical properties of CoCrMo alloy with biodegradable heparin-releasing polymeric coatings. Variants of polymer coatings of poly(L,L-lactide-ɛ-caprolactone) (P(L,L-L/CL)) and poly(D,L-lactide-ɛ-caprolactone) (P(D,L-L/CL)) constituting the base for heparin-releasing (HEP) polyvinyl alcohol (PVA) coatings were analyzed. The coatings were applied by the dip-coating method. Heparin was used to counteract the incrustation process in the artificial urine. The study included tests of wettability, resistance to pitting and crevice corrosion, determination of the mass density of metal ions penetrating into the artificial urine, and the kinetics of heparin release. In addition, microscopic observations of surface roughness and adhesion to the metal substrate were performed. Electrolytically polished CoCrMo samples (as a reference level) and samples with polymer coatings were used for the tests. The tests were conducted on samples in the initial state and after 30, 60, and 90 days of exposure to artificial urine. The analysis of the test results shows that the polymer coatings contribute by improving the resistance of the metal substrate to pitting and crevice corrosion in the initial state and reducing (as compared with the metal substrate) the mass density of metal ion release into the artificial urine. Moreover, the PVA + HEP coating, regardless of the base polymer coatings used, contributes to a reduction in the incrustation process in the first 30 days of exposure to the artificial urine.

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.