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.

Pelvic radiation-induced urinary strictures: etiology and management of a challenging disease

Radiation is a common treatment modality for pelvic malignancies. While it can be effective at cancer control, downstream effects can manifest months to years after treatment, leaving patients with significant morbidity. Within urology, a particularly difficult post-radiation consequence is urinary tract stricture, either of the urethra, bladder neck, or ureter. In this review, we will discuss the mechanism of radiation damage and treatment options for these potentially devastating urinary sequelae.

Comparison of Ureteral Stents on Drainage Performance Under Extrinsic Compression

PURPOSE

By investigating deformation and flow velocity of three commonly used, readily accessible ureteral stents under variant compression and surface change at three time points (new, 1 month or 3 months after implantation), we share our center's experience dealing with ureteral obstruction especially the malignant ones.

MATERIALS AND METHODS

Ureteral double-J (DJ) stents including Cook Universa Soft, Kang Yi Bo (KYB) antireflux and Urovision Visiostar ESWL DJ stents went though scanning microscopic (SEM) analysis. Compression-deformation was measured using digital force gauge. Intraluminal flow velocity was tested with the stents under different compression levels.

RESULT

Urovision Visiostar demonstrated significantly better anti-compression capability. Cook Universa Soft and KYB antireflux showed favorable draining velocity without compression, but the velocity dropped heavily under compression; the velocity of KYB antireflux reduced heavily after 3 months of implantation; Urovision Visiostar achieved the best draining effect under compression at all three time points.

CONCLUSION

The Urovision Visiostar DJ stent demonstrated significantly greater resistance to compression than the other two, and better drainage under compression. Patients with benign or malignant ureteral compression might benefit from using the Urovision Visiostar stents. Large prospective clinical trials are needed for confirmation.

Analysis of Ureteral Tumour Stents for Malignant Ureteral Obstruction: Towards Reshaping an Optimal Stent

Introduction

Ureteral obstruction hinders the management of malignant diseases. Adequate stent placement does not necessarily guarantee renal decompression. The stent stiffness may play a major role to maintain patency. We carried out the present study in order to evaluate drainage efficiency by using stents with distinctive degrees of stiffness and to identify the physical factors that could prevent obstruction of the stent in patients with malignant ureteral obstruction (MUO).

Materials and Methods

We performed an analysis of 150 patients with MUO drainage at a single institution from June 2009 to June 2019. A progressive choice of stents was shaped to overcome each failure by focusing on the criterion of increasingly stiff stents.

Results

During the study period, 556 ureteral stent procedures (USP) were analysed separately. The stent failure with obstruction occurred in 23.0% (128/556) of USP at a mean of 4.4±3.6 months and depended on the type of stent. Stent failure occurred in 34.2% (70/205) of Vortek^® stents, in 42.9% (15/35) of Urosoft stents, in 15.4% (39/254) of Superglide or ureteral catheters and in 6.5% (4/62) of tandem stents. No significant differences were found between Vortek^® and Urosoft stents regarding stent failures, but there were significant differences between Superglide or Tandem stents and Vortek^® or Urosoft stents (p<10⁻⁷). The study demonstrated that ureteral stent obstruction significantly decreased with a larger lumen or a stiffer stent (p<10⁻⁷).

Conclusion

In the present study, Superglide and tandem stents were the best stents against stent failure, and the lumen and the stiffness of the stent have been shown to be critical factors in controlling patency. The results suggest that the lumen seems more important than the stiffness, and the stiffness would be the only means of keeping the lumen intact. Future stents for MUO should integrate the importance of the lumen of the stent.

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.

Metal stent for the ureteral stricture after surgery and/or radiation treatment for malignancy

BACKGROUND

To assess the efficacy and safety of self-expanding metal ureteral stent for the stricture following surgery and/or radiation for malignancy.

METHODS

We performed 36 metal ureteral stent insertion procedures (32 patients) between May 2019 and June 2020. The main inclusion criterion was the patients with ureteral stricture due to surgery and/or radiation treatment for malignancy. The diagnosis of stricture was ascertained by history and radiographic imaging. The etiologies underlying the strictures were: surgery and/or radiation therapy for cervical and rectal cancer, surgery for ovarian cancer. The primary outcome was the stent patency rate, and the secondary outcomes were the postoperative complications and glomerular filtration rate (GFR). Stent patency was defined as stent in situ without evident migration, unanticipated stent exchange or recurrent ureteral obstruction. Cost analysis was calculated from stent cost, anesthesia cost and operating room fee.

RESULTS

The pre-metallic stent GFR was 22.53 ± 6.55 mL/min/1.73 m². Eight patients were on double-J stents before insertion of metallic stents. The total annual cost of per patient in our study was $10,600.2 US dollars (range $9394.4-$33,527.4 US dollars). During a median follow-up time of 16 months (range 8-21 months), 27 cases (31 sides, 84%) remained stent patency. Twelve patients died from their primary malignancy carrying a patency stent. Stent migration was observed in 4 patients within 10 months after insertion. Ectopic stents were endoscopically removed and replaced successfully. Three stents were occluded, and no encrustation was seen in our study. Three and four patients had postoperative fever and gross hematuria, respectively. Infection was observed in 2 cases, mandating antibiotics therapy. In addition, postoperative volume of hydronephrosis postoperatively was significantly reduced compared with preoperation (54.18 ± 15.42 vs 23.92 ± 8.3, P = 0.019). However, no statistically significant differences regarding GFR, creatinine levels, blood urea nitrogen and hemoglobin existed between preoperation and last follow-up.

CONCLUSIONS

The current study demonstrated that metal ureteral stent is effective and safe in the treatment of stricture following surgery and/or radiation therapy for malignant cancer. Patients hydronephrosis could be improved by the stent placement.

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.

10-Year Experience with Reinforced Ureteral Stents for Malignant Ureteral Obstruction

Introduction

Malignant ureteral obstruction (MUO) hinders the management of malignant diseases. Indwelling stent is a common method to release renal obstruction, but stent failure with obstruction is frequent. The studies conclude that stent obstruction divides survival by 2 or even 4. We carried out the present study in order to evaluate drainage efficiency and overall survival by using stents with distinctive degrees of stiffness.

Materials and Methods

We performed an analysis of 156 patients with MUO drainage at a single institution from June 2009 to June 2019.

Results

Of the 156 patients, 128 (82.1%) died with a mean survival time of 15.3 ± 14.4 months after the first ureteral stent procedure (USP). In order to study stent failure and overall survival, the patients were divided into 3 groups. Group 1 with patients died soon after only one USP (n=37). Group 2 with patients had more than one USP and no obstruction (n=41). Patients in Group 3 had more than one USP and at least one stent obstruction (n=62). During the study period, 556 USPs were analysed separately. The stent failure with obstruction occurred in 23.0% (128/556) of USP at a mean of 4.4 ± 3.6 months. In case of stent failure, a progressive choice of stents was shaped to overcome each failure by focusing on the criterion of increasingly stiff stents. Patients in Group 1 died soon at mean of 4.9 ± 4.8 months. The mean survival time of patients in Groups 2 and 3 were, respectively, 19.4 ± 11.2 and 21.5 ± 16.3 months (P = 0.19).

Conclusion

MUO is a serious disease but this study is the first to prevent survival rate from falling by choosing the stent stiffness suitable for the patient. The active detection of stent failure has been shown to be essential for preserving survival.

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.

Single-Centre Experience with Three Metallic Ureteric Stents (Allium® URS, Memokath™-051 and Resonance®) for Chronic Ureteric Obstruction

PURPOSE

Patients with chronic ureteric obstruction (CUO) are traditionally managed with polymer stents/nephrostomy. However, these are prone to failure and require regular exchange. This study evaluates efficacy of Allium® URS, Memokath™-051 and Resonance® metallic ureteric stents in managing patients with CUO.

METHOD

Following institutional approval, operating theatre records were reviewed to identify patients with CUO managed with either Allium® URS, Memokath™-051 or Resonance® metallic ureteric stents (September 2015/July 2020). Baseline patient variables (age, gender, underlying aetiology, ASA) and stricture characteristics (length, level, continuity) were extracted. Intra- and post-operative clinical and radiological assessments at 6 weeks, 3 months and then every 6 months, as well as any emergency attendances, were reviewed. The primary outcome was duration of functional stent survival. Secondary outcomes included intra-operative placement success and, as anestimate of renal function, mean serum creatinine over time.

RESULTS

129 stent insertion episodes (SIEs) (Allium® URS: 23, Memokath™-051: 48, Resonance®: 58) occurred in 76 patients (Allium® URS: 16; Memokath™-051: 31; Resonance®: 29). Kaplan-Meier estimates demonstrated that Resonance® provided superior functional stent survival. Overall median actual functional stent follow-up was 11.4 months for Allium® URS, 5.5 months for Memokath™-051 and 11.7 months for Resonance®. 47.8% of Allium® URS (11/23), 64.6% of Memokath™-051 (31/48) and 19% of Resonance® SIEs (11/58) failed. No Resonance® SIEs for benign indication ended in failure. Intra-operative placement success was high (Allium® URS: 95.7%; Memokath™-051 and Resonance®: both 100%). In the first year following SIE, creatinine ranged from +21.3% to +46.7% for Allium® URS, -7.8% to +8.9% for Memokath™-051, and -9.4% to +27.3% for Resonance®.

CONCLUSIONS

Allium® URS, Memokath™-051 and Resonance® metallic ureteric stents are all viable management options of CUO. In this cohort, Resonance® provided superior functional stent survival. Prospective large-scale comparisons with long-term follow-up are needed to help inform stent choice dependant on individual patient and stricture characteristics.

The Resonance and the Allium ureteral stents in the treatment of non-malignant refractory ureterostenosis

Background

Refractory non-malignant ureterostenosis is challenging to treat. The experience to treat the stenosis primarily cause by retroperitoneal fibrosis with the Resonance and Allium metallic stent is still limited. We aim to evaluate the efficacy and safety of these two stents and provide alternative treatment options.

Methods

A retrospective study was conducted for patients with non-malignant ureterostenosis and treated with the Resonance and Allium stents from March 2011 to September 2020 in our department. The efficacy was evaluated by the change of serum creatinine, glomerular filtration rate (GFR), the proportion of GFR of the affected side and hydronephrosis grade. The safety was evaluated by postoperative presence of moderate or severe overactive bladder (OAB), recurrent urinary infection, pain, stent displacement, encrustation and re-obstruction.

Results

33 patients were eligible for the study, including 18 cases treated by the Resonance stents and 15 patients treated by the Allium stents. The patients of two groups had similar age and gender proportion. The cause of ureterostenosis was mainly retroperitoneal fibrosis in both groups but the Resonance group had more idiopathic cases. Follow-up time was significantly longer in the Resonance group than the Allium group (36.2 ± 24.0 vs 9.4 ± 5.0 months, p < 0.001). Both groups showed improvement or maintenance of serum creatinine level, GFR, the GFR proportion of the affected side and hydronephrosis grade after treatment. The Resonance group presented significant higher incidence of moderate or severe OAB, recurrent urinary infection and pain, while the Allium group showed significant more cases of re-obstruction.

Conclusion

Both the Resonance and Allium stent can relieve the non-malignant refractory ureterostenosis effectively. The Resonance stent may cause more irritable symptoms while the Allium stent may have a higher rate of re-obstruction. The long term efficacy and safety of the Allium stent in treating non-malignant refractory ureterostenosis requires further study.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12894-021-00815-6.

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.

Use of metallic and polymeric ureteral stents in malignant ureteral obstruction

Background

Malignant ureteral obstruction (MUO) is often caused by advanced intra‐abdominal cancers. Effective management must be attempted, but the treatment policy is unclear. Metallic ureteral stents are one of the latest options in managing MUO. Metallic ureteral stents are superior to traditional polyurethane stents. The present study retrospectively reviewed our four institutions’ experiences with treating MUO using metallic ureteral stent.

Methods

A total of 45 patients who required metallic ureteral stent placement for MUO at Yokohama City University Medical Center (Yokohama, JAPAN) between January 2014 and May 2016 were analyzed. We defined stent failure as having to change the ureteral stent before the scheduled ureteral stent exchange time or having to perform percutaneous nephrostomy (PCN). Complications were defined as an unscheduled hospital visit or hospitalization caused by incompatibility, infection, and pain of the metallic ureteral stent, etc., unrelated to the primary disease. We compared stent failure and the overall survival (OS) between metallic and polymeric ureteral stents. To evaluate the workload of the medical staff, we used the NASA Task Load Index (NASA‐TLX) in a total of 11 urologists.

Results

During the observation period, 8 (17.8%) patients in the metallic ureteral stent group and 10 (27.8%) in the control group developed stent failure. Complications were noted in 14 (31.1%) patients in the metallic ureteral stent group and 15 (41.7%) patients in the control group. A Kaplan–Meier analysis and log‐rank test showed no significant differences between two groups in the overall survival (P = 0.673). One or more complications developed in 19 (32.2%) patients in the metallic ureteral stent group and 18 (38.3%) patients in the control group (P = 0.409). Renal dysfunction after the replacement of the ureteral stent developed in 9 (15.3%) patients in the metallic ureteral stent group and 14 (29.8%) patients in the control group. No patients developed a urinary tract infection (UTI) that required hospitalization in the metallic ureteral stent group, whereas 3 (6.4%) patients in the control group had a UTI that was treated with hospitalization. The average workload score in the six subscales was analyzed, and the scores for mental demand and performance were higher in the metallic ureteral stent group, although there was no significant difference between the metallic and polymeric ureteral stent groups.

Conclusions

Metallic ureteral stents showed favorable ureteral stent patency and reduced the workload for urologists.

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.

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

Background

To study the outcomes and experiences of using metallic stents in treating patients with malignant ureteral obstruction (MUO), we examined the effects of metallic ureteral stenting using the Cook Resonance® stent in the treatment of MUO.

Methods

All patients who had a Resonance metallic stent inserted between April 2015 and March 2018 at one of multiple facilities were prospectively observed with a 1-year follow-up. The primary outcome was the patency rate of the metallic ureteral stent. The secondary outcomes included the complications (e.g., infection and fever).

Results

Although stent insertion was attempted in 50 patients, the stent could not be inserted as a ureteral stent in three patients due to severe ureteral stricture, and one ureteral cancer patient was excluded from the analysis. The remaining 46 patients’ median age was 67 years (range 28–85 years) (16 males, 30 females). Twenty-four patients died during the study; their median survival time was 226 days. The median follow-up period for the censored patients was 355 days (range 16–372 days), and just seven patients were still alive without Resonance failure > 1 year later. The women’s IPSS scores tended to be lower than those of the men. Regarding the OABSS score, although the women’s total score tended to be low, the difference between the men’s and women’s scores was nonsignificant. The bacteria detected from urine culture after stent insertion were more gram-positive than gram-negative.

Conclusion

Metallic ureteric stenting using the Resonance stent is safe and effective for treating MUO. Subjective symptoms were relatively less in the female patients.

Tandem Resonance metallic double-J ureteral stents in a single ureter for salvage management of chronic ureteral obstruction

For chronic malignant and benign ureteral obstruction, the metal construction of the Resonance ureteral stent has been developed to maintain ureteral patency for up to 12 months, obviating the need for the frequent exchange required for conventional plastic ureteral stents. We report our experience placing tandem Resonance stents (TRS) in a single ureter of patients who failed management with a single Resonance stent. A retrospective review of patients who had TRS for management of ureteral obstruction between February 2014 and May 2017 was performed. Seven renal units from four patients with a median age of 62 years were managed with TRS. All but one renal unit was successfully managed with TRS initially. Hydronephrosis resolved in 80% of renal units at a median of 33 days, and creatinine reached its nadir a median of 38 days after placement, with a median improvement of 0.68 ng/mL. However, the median length of management with TRS was only 123.5 days with one exchange, and there was an overall success rate of 28.5% at 1 year. TRS placement is a feasible option for short-term management in a challenging population that would like to avoid nephrostomy and has failed other modalities.

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.

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.

Treatment outcomes of ureteral stenting for malignant extrinsic ureteral obstruction: a comparison between polymeric and metallic stents

Purpose

To compare treatment outcomes, more specifically patency rate, of polymeric and metallic stents for malignant ureteral obstruction.

Patients and methods

Between August 2007 and September 2017, we retrospectively analyzed the data of 92 patients (126 ureters) having a diagnosis of malignant extrinsic ureteral obstruction treated with indwelling ureteral stents (polymeric and full-length metallic stents). Of these patients, 35 (54 ureters) were treated with polymeric stents and 57 (72 ureters) with a Resonance® metallic stent. The observation period was censored to 1 year. Survival rate in cases of malignant ureteral obstruction was calculated, and the relationship between the causes of ureteral obstruction, the stent type, and the patency rate was evaluated.

Results

The median observation period was 145 days, with a median survival time of 258 days. The stent patency rate was 70.9% at 1 year, regardless of stent type. Stent occlusion was observed in 20 patients (33 ureters). According to stent type, occlusion of the polymeric and metallic stents was identified in 12 (22%) and 8 (11%) cases, respectively. The clinical features associated with stent failure were assessed. In univariate analysis, the patency rate was significantly better for the metallic stent than for the polymeric stent (1-year patency rate; 78.4%, 61.1%, respectively, HR, 2.15; 95% CI, 1.07-4.33; p=0.031). However, the patency rate among patients with abdominal dissemination, lymph node metastasis, and direct compression by tumor was not significantly different.

Conclusion

Indwelling ureteral stents, particularly metallic stents, are effective for the treatment of malignant ureteral obstruction.

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.

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.

Contemporary management of ureteral strictures

Ureteral stricture disease is a luminal narrowing of the ureter leading to functional obstruction of the kidney. Treatment of strictures is mandatory to preserve and protect renal function. In recent times, the surgical management of ureteral strictures has evolved from open repair to include laparoscopic, robotic and interventional techniques. Prompt diagnosis and early first line intervention to limit obstructive complications remains the cornerstone of successful treatment. In this article, we discuss minimally invasive, endo-urological and open approaches to the repair of ureteral strictures. Open surgical repair and endoscopic techniques have traditionally been employed with varying degrees of success. The advent of laparoscopic and robotic approaches has reduced morbidity, improved cosmesis and shortened recovery time, with results that are beginning to mirror and in some cases surpass more traditional approaches.

Level of evidence: Not applicable for this multicentre audit.

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.

Trans-Urethral Ureteral Stent Replacement Technique (TRUST): 10-Year Experience in 1168 Patients

OBJECTIVES

To affirm technical success, clinical success and safety of fluoroscopically guided transurethral replacement of double-J (DJ) ureteral stents.

METHODS

From January 2005 to December 2015, in a follow-up period ranging from 9 to 73 months, we replaced 6167 DJ ureteral stents in 3221 procedures in 1168 patients. All the procedures were performed in the angiography suite under fluoroscopic control.

RESULTS

Technical success was achieved in 97.5% of the procedures. In eighty procedures, cystoscopic approach was necessary; time from previous procedure and side were significantly associated with technical success. Clinical success was reached in 95.7% of the procedures and was significantly lower in urological and gynaecological tumours (when compared to fibrosis and other causes) and in bilateral stents. No major complications were reported. In 90 cases, self-limiting transient minor haematuria occurred and in 160 procedures urinary tract infection responding to antibiotics were registered. Overall procedure time was 27 min. Mean fluoroscopic time was 6 min and 45 s. Mean radiation dose of the procedure was 38.40 Gy cm².

CONCLUSIONS

In patients that need routine replacement of DJ ureteral stent, transurethral fluoroscopically guided method may be the first choice; only in few cases of technical failure, cystoscopy may be considered.

The resonance® metallic ureteric stent in the treatment of chronic ureteric obstruction: a safety and efficacy analysis from a contemporary clinical series

BACKGROUND

We evaluate the efficacy and safety of metallic ureteric stenting using the Cook Resonance® stent in the treatment of chronic ureteric obstruction of benign and malignant aetiology. Published experience of using this stent in this context is limited. We add to the body of literature on this topic.

METHODS

All patients who had a Resonance® metallic stent inserted between April 2009 and November 2014 in our institution were identified from a prospectively maintained stent-database. Primary outcome was relief of ureteric obstruction, defined by successful clinical and radiological treatment of hydronephrosis/hydroureter. Secondary outcome measures included operative time, radiological exposure, total stent dwell time (defined as the cumulative time in months for which a Resonance® metallic stent was in situ), and early and late complications.

RESULTS

Twenty-one patients underwent 52 stent insertion episodes (SIE). Median age was 58 years (range 39-90). Stent insertion resulted in successful treatment of hydronephrosis/hydroureter in 96% (2 SIE resulted in failure to relieve ureteric obstruction). Median operative time was 21 min (range 12-90) Median radiation exposure was 815.3 cGy/cm2 (range 192.9-5366.3). Median stent dwell time was 19.5 months (range 6-52) in non-malignant and 12 months (range 2-48) in malignant ureteric obstruction. One stent migrated proximally during insertion and had to be retrieved using an antegrade approach. 5 patients re-admitted with haematuria: all resolved without intervention or blood transfusion. 3 episodes of post-operative urinary infection were recorded; all were successfully treated with oral antibiotics.

CONCLUSION

Metallic ureteric stenting using the Resonance® stent is safe and effective for treating ureteric obstruction from both malignant and benign causes. The success rate in our series is 96%.

[The Allium ureteral stent in the management of ureteral stenoses, a retrospective, multicenter study]

OBJECTIVE

To evaluate the performance of the Allium ureteral stent in the management of patients initially treated with double J stents for the long-term treatment of stenoses.

MATERIALS AND METHODS

We performed a retrospective multicenter study involving 36 patients who received 37 Allium ureteral stents (metallic 24 Fr) between September 2011 and January 2015 in one of three French teaching hospital centers. The mean age of the patients was 63.8 years (min-max: 33-88 years) and most were women (70%). Of these patients, 5.6% had ureteral fistulae and 94.4% stenoses. Mean stenosis length was 4.15cm (min-max: 0.5-12cm). All analyses were two-tailed with an alpha risk of 0.05. Statistical significance was set at P<0.05. Results were expressed as hazard ratios (HR) with 95% confidence intervals and P-values.

RESULTS

During the follow-up period, 37% of the stents were removed due to migration (complication occurring in 18.9% of the studied population), infection (10.8%) or intolerance (8.1%). The other stents were removed after 1 year. Clinical effectiveness, defined as a lack of stenosis or fistula recurrence, was 52.8% after a mean follow-up of 7.1 months.

CONCLUSION

Clinically effective in more than 50% of cases, the Allium ureteral stent appears to be an alternative to indwelling double J stents.

LEVEL OF EVIDENCE

4.

[Management of ureteral obstruction : Value of percutaneous nephrostomy and ureteral stents]

Ureteral obstruction represents a heterogeneous disease pattern and is treated by ureteral stenting or percutaneous nephrostomy (PCN) depending on the necessity. The benefits of urinary diversion with ureteral stenting or PCN in malignant ureteral obstruction (MUO) for patient survival are only moderate. No differences have been found between ureteral stenting and PCN in MUO with regard to median patient survival and complication rates. In cases of MUO there is currently no evidence that urinary diversion improves the quality of life. Alternative concepts of ureteral stenting, such as tandem ureteral stents, metallic ureteral stents or metal mesh ureteral stents have not yet shown clear benefits. In benign ureteral obstruction, prospective randomized studies have demonstrated comparable quality of life after PCN or ureteral stenting. The method of choice for urinary diversion is influenced by the recommendations, personal experience of the clinician and the availability of the method.

Outcomes of patients with ureteral obstruction who achieved stent-free state following balloon dilatation

OBJECTIVE

The aim of this study was to assess the therapeutic role of ureteral stent removal following balloon dilatation (BD) in patients with a stent implanted for unilateral ureteral obstruction and with normal contralateral renal function.

MATERIALS AND METHODS

This retrospective cohort study consisted of 37 consecutive patients with unilateral ureteral obstruction whose stents were removed after BD. All patients satisfied the following criteria: normal contralateral renal function, no evidence of malignancy, and the patient was eager to obtain a stent-free state (SFS) without invasive treatment. The relative function of the affected kidney and total renal function before and after stent removal were analyzed using renal scans and estimated glomerular filtration rate (eGFR). A successful outcome was defined as SFS without pain or febrile urinary tract infection plus maintenance of eGFR.

RESULTS

The mean age of all patients was 58.2 years. The mean follow-up periods before and after stent removals were 15.7 and 23.6 months, respectively. The most common underlying cause of ureteral obstruction was pelvic or abdominal surgery (51.4%). Of the 37 patients, 32 (86.5%) achieved successful SFS at last follow-up. Overall in the 37 patients, the eGFR (from 77.1 to 69.8 ml/min/1.73 m(2); p = 0.017) and relative renal function of the affected kidney (from 35.5 to 30.2%; p = 0.002) were significantly compromised. However, the reduction in total eGFR was not significant (p = 0.075) in the successful SFS group.

CONCLUSION

The removal of a stent with BD is a viable option for achieving a successful SFS in patients with unilateral ureteral obstruction.

Malignant Ureteral Obstruction: Functional Duration of Metallic versus Polymeric Ureteral Stents

BACKGROUND

Ureteral obstruction caused by extrinsic compression is often associated with intra-abdominal cancers. Internal drainage with ureteral stents is typically the first-line therapy to relieve such obstructions. Novel designs of ureteral stents made of different materials have been invented to achieve better drainage. In this study, we described the functional outcomes of a Resonance metallic ureteral stent (Cook Medical, Bloomington, Indiana, USA) in patients with malignant ureteral obstruction and compare the functional duration of Resonance stents with regular polymeric stents in the same cohort.

METHODS

Cancer patients who received polymeric stents and subsequent Resonance stents for ureteral obstruction between July 2009 and November 2012 were included in a chart review. Stent failure was detected by clinical symptoms, imaging studies, and renal function tests. The functional durations of each stent were calculated, and possible factors affecting stent patency were investigated.

RESULTS

A total of 50 stents were successfully inserted into 50 ureteral units in 42 patients with malignant ureteral obstruction. There were 7 antegrade stents and 43 retrograde stents. There were no major complications. Stent-related symptoms were similar in both kinds of stents. After polymeric stents were replaced with Resonance metallic stents, hydronephrosis subsided or remained stable in 90% (45/50) of the ureteral units. Serum creatinine decreased or remained stable in 90% (38/42) of these patients. The Resonance stent exhibited a mean increase in functional duration of 4 months compared with the polymeric stents (p<0.0001), and 50% (25/50) of the Resonance stents exhibited a significant increase in functional duration (more than 3 months). Pre-operative serum creatinine < 2 was associated with a substantial increase in stent duration.

CONCLUSIONS

Resonance stents are effective and safe in relieving malignant ureteral obstructions after polymeric stents failure. Resonance stents can provide a longer functional duration than polymeric stents and should be offered as an option for internal drainage.

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.

Stenting for malignant ureteral obstruction: Tandem, metal or metal-mesh stents

Extrinsic malignant compression of the ureter is not uncommon, often refractory to decompression with conventional polymeric ureteral stents, and frequently associated with limited survival. Alternative options for decompression include tandem ureteral stents, metallic stents and metal-mesh stents, though the preferred method remains controversial. We reviewed and updated our outcomes with tandem ureteral stents for malignant ureteral obstruction, and carried out a PubMed search using the terms "malignant ureteral obstruction," "tandem ureteral stents," "ipsilateral ureteral stents," "metal ureteral stent," "resonance stent," "silhouette stent" and "metal mesh stent." A comprehensive review of the literature and summary of outcomes is provided. The majority of studies encountered were retrospective with small sample sizes. The evidence is most robust for metal stents, whereas only limited data exists for tandem or metal-mesh stents. Metal and metal-mesh stents are considerably more expensive than tandem stenting, but the potential for less frequent stent exchanges makes them possibly cost-effective over time. Urinary tract infections have been associated with all stent types. A wide range of failure rates has been published for all types of stents, limiting direct comparison. Metal and metal-mesh stents show a high incidence of stent colic, migration and encrustation, whereas tandem stents appear to produce symptoms equivalent to single stents. Comparison is difficult given the limited evidence and heterogeneity of patients with malignant ureteral obstruction. It is clear that prospective, randomized studies are necessary to effectively scrutinize conventional, tandem, metallic ureteral and metal-mesh stents for their use in malignant ureteral obstruction.

The full metallic double-pigtail ureteral stent: Review of the clinical outcome and current status

The full metallic double-J ureteral stent (MS) was introduced as a method for providing long-term drainage in malignant ureteral obstruction. Experimental evaluation of the MS revealed that its mechanical features allow efficient drainage in difficult cases, which could not be managed by the insertion of a standard polymeric double-J stent. Clinical experience with the MS showed controversial results. Careful patient selection results in efficient long-term management of malignant ureteral obstruction. The use of the MS should also be considered in selected benign cases. Major complications are uncommon and the minor complications should not hinder its use. Experience in pediatric patients is limited and warrants additional study. The cost-effectiveness of the MS seems to be appropriate for long-term treatment. Further investigation with comparative clinical trials would document the outcome more extensively and establish the indications as well as the selection criteria for the MS.

A single-institution experience with metallic ureteral stents: a cost-effective method of managing deficiencies in ureteral drainage

INTRODUCTION

The limitations of traditional ureteral stents in patients with deficiencies in ureteral drainage have resulted in frequent stent exchanges. The implementation of metallic stents was introduced to improve the patency rates of patients with chronic upper urinary tract obstruction, obviating the need for frequent stent exchanges. We report our clinical experiences with the use of metallic ureteral stents in the management of poor ureteral drainage.

MATERIALS AND METHODS

Fifty patients underwent metallic ureteral stent placement from 2009 to 2012. Stent failure was defined as an unplanned stent exchange, need for nephrostomy tube placement, increasing hydronephrosis with stent in place, or an elevation in serum creatinine. Stent life was analyzed using the Kaplan-Meier methodology, as this was a time dependent continuous variable. A cost analysis was similarly conducted.

RESULTS

A total of 97 metallic stents were placed among our cohort of patients: 63 in cases of malignant obstruction, 33 in the setting of cutaneous ureterostomies, and 1 in an ileal conduit urinary diversion. Overall, stent failure occurred in 8.2% of the stents placed. Median stent life was 288.4 days (95% CI: 277.4-321.2 days). The estimated annual cost for traditional polymer stents (exchanged every 90 days) was $9,648-$13,128, while the estimated cost for metallic stents was $4,211-$5,313.

CONCLUSION

Our results indicate that metallic ureteral stent placement is a technically feasible procedure with minimal complications and is well tolerated among patients. Metallic stents can be left in situ for longer durations and provide a significant financial benefit when compared to traditional polymer stents.

The use of internal stents in chronic ureteral obstruction

PURPOSE

Despite the lack of a well delineated definition, chronic ureteral obstruction imposes significant quality of life loss, increased pathological morbidity and risk of mortality as well as substantial economic burden. Ureteral stenting serves as an important therapeutic option to alleviate obstruction. Thus, we assessed the recently published literature on chronic ureteral obstruction; treatment options; types, benefits and shortcomings of current ureteral stents; as well as outcomes and complications of chronic ureteral stenting, with the goal of providing concise management guidelines.

MATERIALS AND METHODS

A systemic literature review was performed on Embase™, PubMed®, Cochrane Controlled Trials Register and Google Scholar™ on ureteral obstruction and internal ureteral stents. Relevant reviews, original research articles and their cited references were examined, and a synopsis of original data was generated on a clinically oriented basis.

RESULTS

Chronic ureteral obstruction can be classified into compression that is either intrinsic or extrinsic to the ureteral wall, or obstruction that is of a benign or malignant origin. Patients with malignant ureteral obstruction generally have a poor prognosis and are often difficult to treat. The aim of stenting is to adequately drain the upper urinary tracts while minimizing hospitalization and the negative impact on quality of life. Facing the challenge of chronic ureteral obstruction, novel stents with new compositions, materials, coatings and designs have been developed. Metallic stents are emerging as efficacious and financially viable alternatives. Early stent related complications include iatrogenic injury, stent migration or patient discomfort, while late complications include infection, difficulties with stent exchange, hardware malfunction, infection and stent encrustation.

CONCLUSIONS

Stenting in chronic ureteral obstruction is a complex and challenging problem. Much work is being done in this area and many options are being explored.

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.

Metallic ureteral stents in malignant ureteral obstruction: clinical factors predicting stent failure

PURPOSE

To provide clinical outcomes of the Resonance metallic ureteral stent in patients with malignant ureteral obstruction, as well as clinical factors predicting stent failure.

METHODS

Cancer patients who have received Resonance stents from July 2009 to March 2012 for ureteral obstruction were included for chart review. Stent failure was detected by clinical symptoms, image studies, and renal function tests. Survival analysis for stent duration was used to estimate patency rate and factors predicting stent failure.

RESULTS

A total of 117 stents were inserted successfully into 94 ureteral units in 79 patients. There were no major complications. These stents underwent survival analysis and proportional hazard regression. The median duration for the stents was 5.77 months. In multivariate analysis, age (P=0.043), preoperative serum creatinine level (P=0.0174), and cancer type (P=0.0494) were significant factors associated with stent failure. Cancer treatment before and after stent insertion had no effect on stent duration.

CONCLUSIONS

Resonance stents are effective and safe in relieving malignant ureteral obstructions. Old age and high serum creatinine level are predictors for stent failure. Stents in patients with lower gastrointestinal cancers have longer functional duration.

Current status of minimally invasive endoscopic management of ureteric strictures

Endourological techniques are used more often nowadays in the treatment of ureteric strictures of various etiologies. Advances in technology have provided new tools to the armamentarium of the endoscopic urological surgeon. Numerous studies exist that investigate the efficiency and safety of each of the therapeutic modalities available. In this review, we attempt to demonstrate the available and contemporary evidence supporting each minimally invasive modality in the management of ureteric strictures.

Tandem ureteral stents for the decompression of malignant and benign obstructive uropathy

PURPOSE

To evaluate the utility of two ipsilateral ureteral stents placed for benign and malignant ureteral obstruction.

METHODS

We performed a retrospective analysis of all cases of tandem ureteral stent (TUS) insertion at our institution from July 2007 through January 2013. Student t, Fisher exact, and log-rank test were used.

RESULTS

TUS insertion or exchange was performed in 187 cases. There were 66 patients (75 renal units) who underwent successful TUS insertion. Malignant ureteral obstruction (MUO) was the cause for obstruction in 39 renal units (34 patients) vs benign ureteral obstruction (BUO) in 36 renal units (32 patients). Four patients with BUO and 15 patients with MUO underwent stent exchanges at a mean 145 and 128 days, respectively. Serum creatinine levels were stable poststent placement (P=0.4). Degree of hydronephrosis improved (paired t test P<0.03) after stent placement for both benign and malignant cohorts. TUS placement was noted to fail (flank pain with worsening hydronephrosis or increasing creatinine level) in five renal units with MUO (12.8%) and none with BUO. Stent failure (either conventional or TUS) suggested worsening survival in those with MUO. Median survival for those with MUO and a history of stent failure (10 of 14 died, 71%) was 66 days compared with 432 days for those without a history of stent failure (8 of 20 died, 40%) (log-rank test P=0.007).

CONCLUSION

Our experience with the TUS, the largest to date, demonstrated that they are highly successful in both benign and malignant causes of obstruction, comparing favorably with metallic ureteral stents. Stent failure may be predictive for shorter survival.

Metallic ureteral stents in malignant ureteral obstruction: short-term results and radiological features predicting stent failure in patients with non-urological malignancies

PURPOSE

To provide short-term result of the metallic ureteral stent in patients with malignant ureteral obstruction and identify radiological findings predicting stent failure.

MATERIALS AND METHODS

The records of all patients with non-urological malignant diseases who have received metallic ureteral stents from July 2009 to March 2012 for ureteral obstruction were reviewed. Stent failure was detected by clinical symptoms and imaging studies. Survival analysis was used to estimate patency rates and factors predicting stent failure.

RESULTS

A total of 74 patients with 130 attempts of stent insertion were included. A total of 113 (86.9 %) stents were inserted successfully and 103 (91.2 %) achieved primary patency. After excluding cases without sufficient imaging data, 94 stents were included in the survival analysis. The median functional duration of the 94 stents was 6.2 months (range 3-476 days). Obstruction in abdominal ureter (p = 0.0279) and lymphatic metastasis around ureter (p = 0.0398) were risk factors for stent failure. The median functional durations of the stents for abdominal and pelvic obstructions were 4.5 months (range 3-263 days) and 6.5 months (range 4-476 days), respectively. The median durations of the stents with and without lymphatic metastasis were 5.3 months (range 4-398 days) and 7.8 months (range 31-476 days), respectively.

CONCLUSION

Metallic ureteral stents are effective and safe in relieving ureteral obstructions resulting from non-urological malignancies, and abdominal ureteral obstruction and lymphatic metastasis around ureter were associated with shorter functional duration.