Metallic Ureteric Stents in Malignant Ureteric Obstruction: A Systematic Review

Trends and incidence of reported events associated with ureteral stents: an analysis of the food and drug administration's manufacturer and user facility device experience (MAUDE) database

PURPOSE

Aim of this study is to summarize medical device reports (MDRs) between 2012 and 2022 relating to ureteral stents within the Manufacturer and User Facility Device Experience (MAUDE) database maintained by The Food and Drug Administration (FDA).

METHODS

MAUDE was analyzed for all MDRs relating to each FDA-approved ureteral stent. Event descriptions were reviewed and characterized into specific event types. Outcome measures include specific ureteral stent and reported events as detailed by the MDRs. Data is presented as number of specific event/total events. Pooled Relative risk was used to compare data.

RESULTS

2652 reports were retrieved in 10 years and a progressive rise in reported events was recorded. 831/2652 (31%) were reported as injury while 1810/2652 (68%) as malfunction of the ureteral stent and 4 events of death. The most frequently reported adverse events (AEs) were stent break (627/2652: 23%); material problems (384/2652: 14%); calcification (222/2652: 8%); difficulty to insert, advance or remove the device (155/2652: 6%). Bard stents were associated with most material problems (19%), Resonance stents were associated with most difficulty to insert, advance or remove the device (9%) and calcification (15%) while filiform double pigtail stent set were associated with most breakage reports (56%) when compared to the other stents (PRR > 1, p < 0,05).

CONCLUSIONS

According to MAUDE database the most frequent complications related to ureteral stents are breakage, material problems, calcification and difficulty to insert/advance/remove the device. As well Resonance ureteral stents seem to be associated with a higher risk of device problems.

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.

Impact of long-term indwelling JJ stent on renal volume and renal function

BACKGROUND

Data is lacking about long-term impact of JJ stents (JJst) on renal parenchyma. The aim of the study was to assess the evolution of renal parenchyma in patients with JJst indwelling for more than two years, and to find predictive factors for the development of renal atrophy.

METHODS

Consecutive patients with JJst indwelled for more than 24 months, with a history of cancer, were retrospectively included. Replacements of JJst were scheduled every six months, or earlier in case of premature obstruction. Patient characteristics at the time of insertion of JJst, history of indwelling JJst and most recent data (serum creatinine, cancer status, definite JJst removal, renal volume (RV) with3D software) were recorded.

RESULTS

With a median follow-up of 4 years, 73 patients were included. The indication of JJst insertion was mostly external compression (65.8%). CT scans were available to assess RV evolution in 66 patients (90.4%). Median shrinkage of RV was higher when JJ stenting was unilateral versus bilateral: -40% (-63; -15) versus -16% (-36; -3), P<0.001. The duration of indwelling JJst was the only statistically significative predictive factor of renal shrinkage in multivariate analysis (OR [CI 95%]: 1.35 [1.10-1.66] P=0.004). Median relative change from baseline in eGFR was -22% (-45%; -5%.). No statistically significant predictive factors of eGFR evolution were found in univariate and multivariate analysis.

CONCLUSIONS

Unilateral JJst for more than 2 years was associated with a significant shrinkage of renal parenchyma, especially since the duration of the indwelling stent was long.

Allium® ureteral stent, a new player in the treatment of ureteral stenosis: a prospective cohort study

INTRODUCTION AND OBJECTIVES

Ureteral stricture is a chronic condition that can result in the obstruction of urinary drainage from the affected renal unit, leading to loss of renal function. Treatment methods can be categorized into two main headings: endourological and reconstructive procedures. We aimed to investigate the efficacy and safety of the self-expandable Allium® ureteral stent, which has been used in the minimally invasive treatment of ureteral stenosis in recent years.

MATERIALS AND METHODS

Twenty patients who were applied Allium® ureteral stent between 2017 and 2021 included in the study. The demographic and clinical characteristics of the patients, the details of the treatments applied to the patients, the perioperative and postoperative complications, the treatments applied for the complications and the findings in the follow-up were recorded and evaluated prospectively.

RESULTS

Etiology included urolithiasis in 16 patients (80%), malignancy in 3 patients (15%), and a previous gynecological operation in 1 patient (5%). Stent obstruction was found to be the most common complication in 3 patients (15%). Stent migration was the second most common complication in 2 patients (10%). Our follow-up continues with 15 patients without stent-related complications and stent obstruction. The mean follow-up period was 28 ± 15.7 months.

CONCLUSIONS

Allium ureteral stent is an effective and reliable method in the minimally invasive treatment of ureteral stricture with complications seen at acceptable rates and ease of treatment in the management of complications.

Effect of ureteral stent length and implantation position on migration after implantation

BACKGROUND

Ureteral obstruction is a urinary system disease that causes urinary retention, renal injury, renal colic, and infection. Ureteral stents are often used for conservative treatment in clinics, and their migration usually results in ureteral stent failure. The migrations include proximal migration to the kidney side and distal migration to the bladder side, but the biomechanism of stent migration is still unknown.

METHOD

Finite element models of stents with lengths from 6-30 cm were developed. The stents were implanted into the middle of the ureter to analyze the effect of stent length on its migration, and the effect of stent implantation position on 6-cm-long stent migration was also observed. The stents' maximum axial displacement was used to assess the ease of stent migration. A time-varying pressure was applied to the ureter outer wall to simulate peristalsis. The stent and ureter adopted friction contact conditions. The two ends of the ureter were fixed. The radial displacement of the ureter was used to evaluate the effect of the stent on peristalsis.

RESULTS AND DISCUSSION

The maximum migration occurs in the positive direction for a 6-cm-long stent implanted at the proximal ureter (CD and DE), but in the negative direction at the distal ureter (FG and GH). The 6-cm-long stent demonstrated almost no effect on ureteral peristalsis. The 12-cm-long stent diminished the radial displacement of the ureter from 3-5 s. The 18-cm stent diminished the radial displacement of the ureter from 0-8 s, and the radial displacement within 2-6 s was weaker than other time. The 24-cm stent diminished the radial displacement of the ureter from 0-8 s, and the radial displacement within 1-7 s was weaker than other time.

CONCLUSION

The biomechanism of stent migration and ureteral peristalsis weakening after stent implantation was explored. Shorter stents were more likely to migrate. The implantation position had less influence on ureteral peristalsis compared with the stent length, which provided a reference for stent design aimed at reducing stent migration. Stent length was the main factor affecting ureteral peristalsis. This study provides a reference for the study of ureteral peristalsis.

Long-term maintenance treatment of recurrent ureteropelvic junction obstruction with covered metallic ureteral stent

Whether or not the covered metallic ureteral stent can be used as maintenance treatment for recurrent ureteropelvic junction obstruction (UPJO) after pyeloplasty is unknown. Therefore, this study aims to analyze its feasibility. We retrospectively analyzed the records of 20 patients with recurrent UPJO who were treated with the covered metallic ureteral stents from March 2019 to June 2021 at our institution. Then, we assessed their renal function, stent patency and stent-related quality of life by the blood creatinine, renal ultrasound (or computed tomography), and the Chinese version of the ureteral symptom score questionnaire (USSQ). The last follow-up mean blood creatinine dropped from 0.98 ± 0.22 to 0.91 ± 0.21 mg/dL (P = .04), and the median renal pelvic width was reduced from 3.25 (3.10) to 2.00 (1.67) cm (P = .03) compared with the preoperative conditions. Meanwhile, the last follow-up mean USSQ total score of the covered metallic ureteral stent among the 16 patients with preoperative indwelling double-J ureteral stent was 78.56 ± 14.75, significantly lower than the preoperative USSQ total score, which was 102.25 ± 5.57 (P < .001). During the median duration of follow-up of 27.00 (18.00) months, 85% (17/20) of patients maintained unobstructed drainage from the renal pelvis to the ureter. Stent-related complications occurred in 7 patients, 3 of which failed because of complications, including stent migration (1 patient), stent encrustation (1 patient), and stent-related infection (1 patient). The covered metallic ureteral stent is feasible for the long-term maintenance treatment of recurrent UPJO after pyeloplasty.

Magnetic resonance imaging of in vitro urine flow in single and tandem stented ureters subject to extrinsic ureteral obstruction

OBJECTIVE

To quantify the relative volumetric flows in stent and ureter lumina, as a function of stent size and configuration, in both unobstructed and externally obstructed stented ureters.

METHODS

Magnetic resonance imaging was used to measure flow in stented ureters using a phantom kidney model. Volumetric flow in the stent and ureter lumina were determined along the stented ureters, for each of four single stent sizes (4.8F, 6F, 7F, and 8F), and for tandem (6F and 7F) configurations. Measurements were made in the presence of a fully encircling extrinsic ureteral obstruction as well as in benchmark cases with no extrinsic ureteral obstruction.

RESULTS

Under no obstruction, the relative contribution of urine flow in single stents is 1-10%, while the relative contributions to flow are ~6 and ~28% for tandem 6F and 7F, respectively. In the presence of an extrinsic ureteral obstruction and single stents, all urine passes within the stent lumen near the extrinsic ureteral obstruction. For tandem 6F and 7F stents under extrinsic ureteral obstruction, relative volumetric flows in the two stent lumina are ~73% and ~81%, respectively, with the remainder passing through the ureter lumen.

CONCLUSIONS

Magnetic resonance imaging demonstrates that with no extrinsic ureteral obstruction, minimal urine flow occurs within a stent. Stent lumen flow is significant in the presence of extrinsic ureteral obstruction, in the vicinity of the extrinsic ureteral obstruction. For tandem stents subjected to extrinsic ureteral obstruction, urine flow also occurs in the ureter lumen between the stents, which can reduce the likelihood of kidney failure even in the case of both stent lumina being occluded.

Fluid mechanical modeling of the upper urinary tract

The upper urinary tract (UUT) consists of kidneys and ureters, and is an integral part of the human urogenital system. Yet malfunctioning and complications of the UUT can happen at all stages of life, attributed to reasons such as congenital anomalies, urinary tract infections, urolithiasis and urothelial cancers, all of which require urological interventions and significantly compromise patients' quality of life. Therefore, many models have been developed to address the relevant scientific and clinical challenges of the UUT. Of all approaches, fluid mechanical modeling serves a pivotal role and various methods have been employed to develop physiologically meaningful models. In this article, we provide an overview on the historical evolution of fluid mechanical models of UUT that utilize theoretical, computational, and experimental approaches. Descriptions of the physiological functionality of each component are also given and the mechanical characterizations associated with the UUT are provided. As such, it is our aim to offer a brief summary of the current knowledge of the subject, and provide a comprehensive introduction for engineers, scientists, and clinicians who are interested in the field of fluid mechanical modeling of UUT. This article is categorized under: Cancer > Biomedical Engineering Infectious Diseases > Biomedical Engineering Reproductive System Diseases > Biomedical Engineering.

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

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

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Innovative biodegradable antibacterial Mg-Sr-Ag alloy.

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In vivo study in pig ureter models.

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Enhanced mechanical properties and adjustable indwelling time.

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Outstanding urinary compatibility and evident antibacterial activity.

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

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

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

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.

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.

The Fate of Ureteral Memokath Stent(s) in a High-Volume Referral Center: An Independent Long-Term Outcomes Review

Purpose: To independently assess upper urinary tract Memokath (MMK-051) stent outcomes in a national tertiary referral center. Materials and Methods: Two researchers, completely independent to the treating team, reviewed electronic MMK-051 stent(s) patient management records. Outcomes included time to first complication, complication(s)-severity, MMK-051 stent lifespan and change incidence, salvage therapy, further surgical intervention, and mortality. Results and Limitations: One hundred patients received 162 MMK-051 stent(s) (59% with malignant and 63% with distal ureteral obstruction [UO]) with only three lost to follow-up (FU). At 5-year mean FU, only 25 patients had complication-free original MMK-051 stents (14 alive, 11 dead). Of the remaining 75 patients, 22 had other stents, 12 had major surgery (e.g., nephrectomy), 3 became dialysis dependent, and 14 stabilized without ureteral stenting after original MMK-051 removal. Malignant obstruction patients had greater original MMK-051 stent longevity (p < 0.02), but also 20 of the 21 deaths (95%). The 72% mean 5-year stent complication rate included migration (46%), blockage (34%), nonfunctioning kidney (8%), urosepsis needing intravenous antibiotics (8%), and others (6%), including one postoperative death, one ureteral injury, and two with intractable pain. Median time to first complication was 12.5 months. Conclusions: MMK-051 stents had optimal utility in managing malignant UO and in those unfit for corrective surgery. Longer independently assessed mean 5-year outcomes review revealed much higher complication rates (72%) than previously reported. Future international metallic ureteral stent guidelines should encourage clinicians to adopt patient-centered multidisciplinary assessment and selection, with counseling plus goal-setting, and harmonized long-term protocol-based reporting, for optimized future patient safety and outcomes.

Strategies to Improve Patient Outcomes and QOL: Current Complications of the Design and Placements of Ureteric Stents

Ureteric stents have played a vital role in relieving urinary obstruction in many urological conditions. Although they are extremely successful, stents have been associated with complications and reduced patients' health-related quality of life (HRQoL). There are many factors that may affect the quality and longevity of stents. In this review, we have highlighted the journey and innovation of ureteric stents through the modern day. A literature review was conducted to identify relevant articles over the last 20 years. There is a plethora of evidence with various indications for the use of ureteral stents and how they affect QoL. There is still ongoing research to develop the ideal stent with reduced encrustation, one that resists infection and is also comfortable for the patients. Stents made from metal alloys, polymers and biodegradable materials have unique properties in their own right but also have certain deficiencies. These have been discussed along with an overview of newly developed stents. Certain pharmacological adjuncts have also been highlighted that may be useful to improve patient's tolerance to stents. In summary, this paper describes the features of the different types of stents and the problems that are frequently encountered, including effect on patients' HRQoL and financial burden to healthcare providers.

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.

Clinical outcomes and prognostic factors associated with internal ureteral stent placement for malignant extrinsic ureteral obstruction

PURPOSE

The optimal management of malignant extrinsic ureteral obstruction (MUO) remains unclear. It is necessary to assess the patient prognosis in deciding the adaptation of drainage of renal pelvis. In this study, we investigated the clinical outcomes after ureteral stenting for MUO and the predictive factors for overall survival in order to create a risk-stratification model.

METHODS

We retrospectively analyzed the clinical and laboratory data of 93 patients with radiologically significant hydronephrosis associated with MUO who underwent successful stent placement between May 2005 and May 2018.

RESULTS

The median survival duration after the initial stent insertion was 266 days. Of the 93 patients, 70 died, and the median interval from the first stent insertion to death was 160 days. Multivariate analysis showed that gastric cancer as the primary disease, poor performance status before stenting, and treatment after stent insertion were significant predictors of survival. According to these three factors, we stratified patients into the following four prognostic groups: no-factor (43 patients), one-factor (23 patients), two-factor (23 patients), and three-factor (4 patients) groups. This classification was effective for predicting survival, and the median survival durations in these groups were 807, 269, 44, and 12 days, respectively (p < 0.001).

CONCLUSIONS

Our stratification model of patients with a poor prognosis after ureteral stent placement for MUO may allow urologists and clinicians to identify patients who will benefit from ureteral stenting.

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.

Clinical application of fluoroscopic guided percutaneous antegrade ureteral stents placement for the treatment of malignant ureteral obstruction

OBJECTIVE

To investigate the clinical efficacy and safety of fluoroscopic guided percutaneous antegrade ureteral stents placement used for treatment of malignant ureteral obstruction.

METHODS

Between April 2016 and March 2018, fluoroscopic guided percutaneous ureteral stents was performed in 25 patients, including 7 patients (28%) with bilateral obstruction. The most common cancer diagnoses were cervical cancer (28%), rectal cancer (24%) and colon cancer (16%) among these patients. Clinical data were retrospectively analyzed with respect to the efficacy, safety and outcome of this treatment method.

RESULTS

Percutaneous antegrade placement of ureteral stents was performed in all cases, including 12 ureters that failed in the initial retrograde ureteral stents placement. The median stent patency time for the antegrade ureteral stents were 10.4 (95% CI: 8.3-12.6) months. The primary complications included mild flank pain and discomfort (44%), hematuria (44%), urinary tract infection (8%), bladder irritation symptoms (4%), and arterial bleeding (4%).

CONCLUSION

Fluoroscopic guided percutaneous ureteral stents placement is a safe, efficient procedure and has a high success rate in patients with malignant ureteral obstruction.

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

OBJECTIVES

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

KEY POINTS

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