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

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.

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.

Metal ureteral stents for ureteral stricture: 2 years of experience with 246 cases

BACKGROUND

Metal ureteral stents (MUS) has gained popularity as an endoscopic treatment alternative for the management of ureteral strictures. The aim of this study was to evaluate the safety, efficacy, and tolerability of MUS for treating ureteral strictures and to identify any factors that could influence the success of this intervention.

METHODS

This study is a prospective analysis of the efficacy and safety of MUS for treating ureteral strictures in a single-center setting. The study enrolled 246 patients who had been diagnosed with ureteral strictures and had undergone MUS placement between January 2019 and July 2021. The patients were followed-up for a duration of 2 years.

RESULTS

The overall success rate of MUS placement was 71.7%. Furthermore, the success rate of ureteral strictures after kidney transplantation (78.2%) was significantly higher than common ureteral strictures (73.0%) or recurrent ureteral strictures (67.6%). Additionally, postsurgery, there was a considerable reduction in hydronephrosis volume (68.9±96.1 vs. 32.1±48.8 cm 3 ), blood creatinine level (103.7±49.8 vs. 94.4±47.5 mol/l) and urea nitrogen level (6.7±7.2 vs. 5.1±2.4 mmol/l). The study also reported that the rate of adverse events associated with MUS was relatively low, included hematuria (7.9%), pain (6.8%), urinary tract infection (6.4%), and lower urinary tract symptoms (5.3%).

CONCLUSIONS

MUS appear to be a safe and effective treatment option for ureteral strictures, with a high success rate and low complication rate. These results have important implications for the management of ureteral strictures and can help guide clinical decision-making in the selection of treatment options.

Outcomes following Exchange and Upsizing of Malfunctioning Small-Caliber Double-J Ureteral Stents

PURPOSE

To determine the effectiveness of exchange and upsizing of malfunctioning small-caliber double-J (JJ) ureteral stents.

MATERIALS AND METHODS

Thirty-one patients with malfunctioning cystoscopically placed small-caliber (6 or 7 F) JJ stents underwent transurethral (n = 28) or transrenal (n = 3) exchange and upsizing to a large-caliber (10 F) JJ stent from 2013 to 2022. Ureteral obstruction was malignant in 20 patients (65%) and benign in 11 (35%). Fifteen patients (48%) presented with persistent hydroureteronephrosis and 16 patients (52%) with worsening hydronephrosis. Acute kidney injury (AKI) was present in 19 patients (61%) at the time of stent malfunction. Therapeutic success was defined as resolution of hydronephrosis and AKI, if present.

RESULTS

JJ stent exchange and upsizing was technically successful in 31 patients (100%) with no immediate adverse events. Therapeutic success was achieved in 27 patients (87%). During follow-up (median, 97 days; IQR, 32-205 days), 2 patients who initially achieved therapeutic success had stent malfunction, requiring conversion to percutaneous nephrostomy drainage (2/27, 7%).

CONCLUSIONS

Exchange and upsizing to large-caliber JJ stents can relieve urinary obstruction and resolve AKI in patients with malfunctioning small-caliber JJ stents. Large-caliber JJ stents should be considered as a salvage option for patients who wish to continue internal drainage and avoid percutaneous nephrostomy.

Allium ureteral stent for the treatment of malignant ureteral obstruction: A median term study

This study aimed to assess the safety and efficacy of Allium ureteral stents for the maintenance therapy of malignant ureteral obstruction (MUO). Clinical data of 25 patients (27 sides) with ureteral obstruction caused by a malignant tumor from December 2018 to December 2021 were retrospectively analyzed. Preoperative ultrasonography and computed tomography urography indicated hydronephrosis and MUO. Allium ureteral stents were placed using a retrograde or antegrade approach. Therapeutic effects and complications were recorded. The Wilcoxon signed-rank test was used to compare continuous variables between the preoperative and the last follow-up. A total of 25 patients (27 sides) were included in this study. After a follow-up time of 18 (11-29) months, the width of hydronephrosis [1.6 (1.0-2.2) cm vs 2.6 (1.2-3.3) cm, P = .000], glomerular filtration rate [83.8 (58.1-86.4) mL/minutes/1.73 m2 vs 74.5 (56.8-79.1) mL/minutes/1.73 m2, P = .001] and score of ureteral stent symptoms questionnaire [77 (76-79) vs 100 (98-103), P = .000] was significantly improved. Stent migration occurred in 3 of the 25 patients within 3 months after surgery. All patients with complications were followed up for at least 6 months after stent adjustment or exchange, and no other complications were found. Two patients died because of malignant complications. The stent patency rate was 88.9% (24/27) after the first operation, and 100% (27/27) after complications were treated. The Allium ureteral stent is safe and effective for the maintenance therapy of MUO, which can dramatically relieve the symptoms of patients. Stent migration is a major complication that can be resolved by endoscopic adjustment.

REVIEW ON COMPLICATIONS AND ADVERSE EFFECTS OF METALLIC URINARY STENTS

Urinary stents, be it urethral or ureteral, polymeric, metallic or biodegradable, are one of the most frequently used tools in urology and they have been used for decades in prophylactic and therapeutic setting. Although relatively low invasive, they are prone to complications and adverse effects so much that complication rates up to 100% have been described. Many reviews have focused either on specific groups of patients or particular stent types, materials or designs but so far, no comprehensive review on complications has been published. To tackle this issue, a working group was set up within ENIUS (European Network of multidisciplinary research to Improve Urinary Stents) tasked with literature search in order to screen for and systematically review published stent complications in urethra (male only) and ureters (polymeric and metallic ureteral stents in both sexes) when used in obstructed systems. In this paper, we review, catalogue and summarize complications published for metallic urethral and ureteral stents.

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.

Acute kidney injury due to bilateral malignant ureteral obstruction: Is there an optimal mode of drainage?

There is a well-known relationship between malignancy and impairment of kidney functions, either in the form of acute kidney injury or chronic kidney disease. In the former, however, bilateral malignant ureteral obstruction is a surgically correctable factor of this complex pathology. It warrants urgent drainage of the kidneys in emergency settings. However, there are multiple controversies and debates about the optimal mode of drainage of the bilaterally obstructed kidneys in these patients. This review addressed most of the concerns and provided a comprehensive presentation of this topic from the recent literature. Also, we provided different perspectives on the management of the bilateral obstructed kidneys due to malignancy. Despite the frequent trials for improving the success rates and functions of ureteral stents, placement of a percutaneous nephrostomy tube remains the most recommended tool of drainage due to bilateral ureteral obstruction, especially in patients with advanced malignancy. However, the disturbance of the quality of life of those patients remains a major unresolved concern. Beside the unfavorable prognostic potential of the underlying malignancy and the various risk stratification models that have been proposed, the response of the kidney to initial drainage can be anticipated and evaluated by multiple renal prognostic factors, including increased urine output, serum creatinine trajectory, and time-to-nadir serum creatinine after drainage.

Nephrostomy tube versus double J ureteral stent in patients with malignant ureteric obstruction. A systematic review and meta-analysis of comparative studies

PURPOSE

We aimed to perform a systematic review to assess perioperative outcomes, complications, and survival in studies comparing ureteral stent and percutaneous nephrostomy in malignant ureteral obstruction.

MATERIALS AND METHODS

This review was performed according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses framework. Meta-analyses were performed on procedural data; outcomes; complications (device-related, accidental dislodgement, febrile episodes, unplanned device replacement), dislodgment, and overall survival. Continuous variables were pooled using the inverse variance of the mean difference (MD) with a fixed effect, and 95% confidence interval (CI). The incidences of complications were pooled using the Cochran-Mantel-Haenszel method with the random effect model and reported as Odds Ratio (OR), and 95% CI. Statistical significance was set two-tail p-value < 0.05 Results: Ten studies were included. Procedure time (MD -10.26 minutes 95%CI -12.40-8.02, p< 0.00001), hospital stay (MD -1.30 days 95%CI -1.69 - -0.92, p< 0.0001), number of accidental tube dislodgments (OR 0.25 95% CI 0.13 - 0.48, p< 0.0001) were significantly lower in the stent group. No difference was found in mean fluoroscopy time, decrease in creatinine level post procedure, overall number of complications, interval time between the change of tubes, number of febrile episodes after diversion, unplanned device substitution, and overall survival.

CONCLUSION

Our meta-analysis favors stents as the preferred choice as these are easier to maintain and ureteral stent placement should be recommended whenever feasible. If the malignant obstruction precludes a stent placement, then PCN is a safe alternative.

Evaluation of glomerular filtration rate decline in patients with renal colic

PURPOSE

The aim of current study was to evaluate glomerular filtration rate (GFR) decline in patients with renal colic.

MATERIALS AND METHODS

This descriptive analytical study was conducted on patients with definitive diagnosis of renal colic in Alzahra hospital. Data including gender, age, and underlying disease were extracted from medical records. GFR and creatinine level were assessed before and 3 months after stone excretion. Hydronephrosis severity was assessed by ultrasound procedure.

RESULTS

In current study, 224 patients with renal colic and mean age 45.6±11.35 years old were selected. The mean GFR before and 3 months after urinary stone excretion were 45.89±18.84 and 61.13±22.10 ml/minute, respectively (P<0.01). The mean creatinine at the beginning and 3 months after urinary stone excretion was 1.93±0.46 and 1.59±0.43 mg/dl, respectively (P<0.01). The most frequency of patients with different hydronephrosis degrees was related to score 3 (n=92). There was significant difference between hydronephrosis severity in terms of GFR (P=0.000). No significant difference was seen between the mean GFR at the beginning of the study and at 3 months after urinary stone excretion in terms of diabetes and hypertension (P>0.05).

CONCLUSION

We observed significant difference between hydronephrosis severity in terms of GFR. This indicated that the increase of hydronephrosis degree was associated with worse renal function. Moreover, urinary stone excretion led to the increase of GFR and the decrease of creatinine level. In addition, the mean GFR was not influenced by diabetes and hypertension.

Stenting of Malignant Urinary Tract Obstructions in Humans and Companion Animals

Urine retention secondary to neoplastic obstructions of the upper and lower urinary tracts is a life-threatening condition in both humans and companion animals. Stents can be placed to temporarily or permanently open obstructed urinary tract lumens and are often able to be placed using minimally invasive techniques with guidance via ultrasonography or fluoroscopy. The literature for these techniques is vast for humans and growing for companion animals. The below review provides a discussion of the principles of stenting and types of ureteral and urethral stents, as well as the techniques for placing these stents in humans and companion animals.

New Stent Technologies

Ureteral stents are an indispensable part of any (endo-) urologic practice. Despite the widely demonstrated advantages of stents, they also carry a considerable risk of side effects and complications, such as urinary symptoms, pain, hematuria, decreased quality of life, stent-related infection, and encrustation. Multiple pathways in preventing or mitigating these side effects and complications and improving stent efficacy have been and are being investigated, including stent architecture and design, biomaterials, and coatings. This article provides an update on currently researched and available stents as well as future perspectives.

Self-expanding metal ureteral stent for ureteral stricture: Experience of a large-scale prospective study from a high-volume center - Cross-sectional study

BACKGROUND

The management of ureteral stricture is still a challenge for urologists. The aim of this prospective study was to assess the safety and effectiveness of self-expanding metal ureteral stents (URS) in ureteral strictures.

METHODS

We performed URS placement procedures for ureteral stricture from Jan 2019 to July 2020, and prospectively collect various data before and after the operation. A paired T test was used to compare continuous variables before and after surgery, binary logistic regression analysis was used to identify the independent risk predictors of surgical failure.

RESULTS

A total of 147 patients with 157 renal units received successful placement of URS. The mean operative time was 70.0 min. After a median follow-up time of 15 months, 73.2% (115/157) of stents were kept in situ. The most common complication was hematuria (13, 8.8%), followed by urinary tract infection (11, 7.5%) and pain (8, 5.4%). The volume of hydronephrosis (67.9 ± 34.9 VS 34.9 ± 51.1 cm³, P = 0.0001), serum creatinine level (103.0 ± 54.5 VS 93.8 ± 45.1 μmol/L, P = 0.034) and blood urea nitrogen level (6.6 ± 6.7 VS 5.4 ± 2.4 mmol/L, P = 0.032) decreased significantly at last follow up when compared with baseline. Stricture of the distal ureter was an independent risk factor for stent failure (HR 1.77, 95% CI 1.15, 2.73, P = 0.009).

CONCLUSIONS

URS was found to be safe and effective for ureteral strictures with a limited complications and good long-term results. For those who are not suitable for surgical reconstruction, the URS is an alternative management.

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.

Predictors for failure of endoscopic ureteric stenting in patients with malignant ureteric obstruction: systematic review and meta-analysis

OBJECTIVE

To determine the factors for failure of endoscopic ureteric stenting in patients with malignant ureteric obstruction.

METHODS

We performed a search strategy in the Medical Literature Analysis and Retrieval System Online (MEDLINE), the Excerpta Medica dataBASE (EMBASE), the Literatura Latino-Americana e do Caribe em Ciências da Saúde database (LILACS), and the Cochrane Central Register of Controlled Trials (CENTRAL) databases. We included patients with malignant ureteric obstruction, who had a JJ catheter insertion. The studies reported the percentage of failure and risk factors, e.g. bladder invasion or deformity of the trigone, hydronephrosis, renal failure, previous radiotherapy, age, obstruction aetiology, and patient's health status. We performed a meta-analysis using R software ('meta' and 'metafor' libraries).

RESULTS

We included nine studies that met the inclusion criteria, with 761 patients and an average age of 60.5 years. The studies assessed the time to failure during the first 30 days. The reported failure rate was 32% (95% confidence interval [CI] 21-45%; I² = 88%). Regarding risk factors for failure, bladder invasion or deformity of the trigone had a hazard ratio (HR) of 4.8 (95% CI 1.28-8.5; I² = 97.4%); severe hydronephrosis had a HR of 3.92 (95% CI 0.32-7.52; I² = 93.9%); and age <65 years had a HR of 0.93 (95% CI 0.8-0.9; I² = 0%).

CONCLUSIONS

We found a high probability of failure for endoscopic urinary decompression in patients with malignant ureteric obstruction. Factors such as bladder invasion or deformity of the trigone and age >65 years had an increased risk of failure.

Roles Played by Biomarkers of Kidney Injury in Patients with Upper Urinary Tract Obstruction

Partial or complete obstruction of the urinary tract is a common and challenging urological condition caused by a variety of conditions, including ureteral calculi, ureteral pelvic junction obstruction, ureteral stricture, and malignant ureteral obstruction. The condition, which may develop in patients of any age, induces tubular and interstitial injury followed by inflammatory cell infiltration and interstitial fibrosis, eventually impairing renal function. The serum creatinine level is commonly used to evaluate global renal function but is not sensitive to early changes in the glomerular filtration rate and unilateral renal damage. Biomarkers of acute kidney injury are useful for the early detection and monitoring of kidney injury induced by upper urinary tract obstruction. These markers include levels of neutrophil gelatinase-associated lipocalin (NGAL), monocyte chemotactic protein-1, kidney injury molecule 1, N-acetyl-b-D-glucosaminidase, and vanin-1 in the urine and serum NGAL and cystatin C concentrations. This review summarizes the pathophysiology of kidney injury caused by upper urinary tract obstruction, the roles played by emerging biomarkers of obstructive nephropathy, the mechanisms involved, and the clinical utility and limitations of the biomarkers.

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.