Metallic stents in the management of ureteric strictures

Unraveling the Complexities of Uretero-Enteric Strictures: A Modern Review

PURPOSE OF REVIEW

The purpose of this review article is to provide a contemporary overview of benign uretero-enteric anastomotic stricture (UAS) management and outcomes.

RECENT FINDINGS

In this article, we will review the most recent studies investigating UAS and evaluate etiology, potential risk factors, presentation, diagnosis, and management options, along with personal insight gained from our experience with managing this challenging reconstructive complication. Benign UAS is a relatively common long-term complication of intestinal urinary diversion, affecting approximately 1 in 10 patients. It is thought to be caused by ureteral tissue ischemia and fibrosis at the anastomotic site. Risk factors appear to include any that increase the likelihood of leak or ischemia; it is not clear if anastomotic approach impacts risk for stricture as well. Management options are varied and include endourologic, open, and robotic approaches. Endoscopic approaches may be less morbid but are considerably less effective than reconstruction performed after a period of ureteral rest.

A Forgotten Double-J Ureteric Stent as the Core of a Bladder Stone: A Case Report and Literature Review

BACKGROUND Double-J (D-J) ureteric stents are widely applied in urological operations as they play a vital role in maintaining postoperative functionality of the patient's urinary system and thereby accelerating recovery. D-J stent encrustation may occur due to prolonged retention and lead to secondary complications. We report the case of a forgotten D-J stent that gradually formed into a bladder stone. CASE REPORT A 54-year-old man was referred to the Urology Department due to intermittent hematuria, left flank pain, and lower urinary tract symptoms that persisted for 2 weeks. His history was significant for undergoing left ureterolithotripsy followed by the implantation of an ipsilateral D-J stents 2 years ago in a local hospital. The patient did not follow-up regularly or actively seek medical attention for his urinary tract symptoms. Computed tomographic urography revealed a hyperdense tubular object protruding from the left distal ureter to the bladder. The patient underwent cystolithotripsy, left ureteric stent removal, and left ureteroscopy to clear away the bladder stone and its D-J stent core. CONCLUSIONS Formation of bladder stones secondary to prolonged indwelling D-J stent and its encrustation is not uncommon in developing countries where the level of public education is low. Prompt D-J stent removal can prevent complications associated with its retention and avoid unnecessary secondary procedures. Endoscopic urologic procedures are safe and feasible management options, and doctor-to-patient communication is vital for a better prognosis.

Assessment of encrustation and physicochemical properties of poly(lactide-glycolide) - Papaverine hydrochloride coating on ureteral double-J stents after long-term flow of artificial urine

Implantation of ureteral stents is associated with inconvenience for the patient, which is related to the natural ability of the ureter to contract. The most frequently used solution is the systemic administration of a diastolic drug, which has a relaxing effect on smooth muscle cells and decreases inconvenience. Current interdisciplinary research aimed at reducing the complications after the implantation of ureteral stents used in the treatment of upper urinary tracts with regard to infection, initiation of encrustation, and fragmentation of stents, and patient pain has not been resolved. This study presents the results of research regarding the impact of a biodegradable coating with the active substance on the physical and chemical properties of ureteral stents used in the treatment of the upper urinary tract. The surface of polyurethane double-J stents was coated with poly(lactide-glycolide) (PLGA) 85/15 loaded with papaverine hydrochloride (PAP) with diastolic properties. The coating for ureteral stents has been designed for short-term implantation. The effect of the coating on the process of encrustation and PAP release by the dynamic in vitro model with artificial urine (AU) up to 30 days was evaluated. The influence of AU on the physical and chemical properties of ureteral stents was determined. As part of the study, surface structure and topography researches; chemical composition analyses using X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, and wetting; and surface roughness studies of both PUR stents and coated stents were carried out. The proposed biodegradable PLGA+PAP coating is characterized by controlled drug release, while optimal physicochemical properties does not increase the encrustation process.

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 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.

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.

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.

Engineering solutions to ureteral stents: material, coating and design

Introduction

An ideal stent would offer simple insertion and removal with no discomfort and/or migration, it would have no biofilm formation or encrustation and would also maintain the patient's quality of life.

Material and methods

In this mini-review, we outlined the engineering developments related to stent material, design and coating.

Results

There have been a wide variety of in-vitro, model-based, animal-based and clinical studies using a range of commercial and non-commercial stents. Ureteric stents have evolved since their first usage with a wider range of stent design, material and coating available for laboratory and clinical use.

Conclusions

While engineering innovations have led to the evolution of stents, more work needs to be done to address the issues relating to stent encrustation and biofilm formation.

Ureteroiliac Artery Fistula Caused by a Metallic Memokath Ureteral Stent in a Radiation-Induced Ureteral Stricture

Background: Memokath 051™ stents are increasingly used for management of benign and malignant ureteral strictures refractory to management with single or tandem polymeric Double-J ureteral stents. Migration, encrustation, and difficulty in extraction during stent exchange are the chief problems reported so far with these thermoexpandable metallic stents. We report an unusual complication of ureteroexternal iliac artery fistula (UEAF) caused by Memokath stent inserted for radiation-induced ureteral stricture.

Case Presentation: A 71-year-old male with history of colorectal cancer (underwent extirpative surgery + chemoradiotherapy) and subsequently radiation-induced ureteral stricture had bilateral Memokath ureteral stents inserted. Three months later, he presented with sepsis and hemodynamic instability secondary to UEAF, confirmed on angiography. A covered vascular stent was inserted as an immediate management.

Conclusion: Memokath stent insertion in radiation-induced ureteral strictures may be associated with an increased risk of erosion and the rare potential complication of UEAF. This potential risk needs to be considered in the overall setting of such strictures and the difficulty in treating them. Prompt imaging (angiography) and placement of an endovascular stent are the ideal immediate options in such cases.

Stents for malignant ureteral obstruction

Malignant ureteral obstruction can result in renal dysfunction or urosepsis and can limit the physician's ability to treat the underlying cancer. There are multiple methods to deal with ureteral obstruction including regular polymeric double J stents (DJS), tandem DJS, nephrostomy tubes, and then more specialized products such as solid metal stents (e.g., Resonance Stent, Cook Medical) and polyurethane stents reinforced with nickel-titanium (e.g., UVENTA stents, TaeWoong Medical). In patients who require long-term stenting, a nephrostomy tube could be transformed subcutaneously into an extra-anatomic stent that is then inserted into the bladder subcutaneously. We outline the most recent developments published since 2012 and report on identifiable risk factors that predict for failure of urinary drainage. These failures are typically a sign of cancer progression and the natural history of the disease rather than the individual type of drainage device. Factors that were identified to predict drainage failure included low serum albumin, bilateral hydronephrosis, elevated C-reactive protein, and the presence of pleural effusion. Head-to-head studies show that metal stents are superior to polymeric DJS in terms of maintaining patency. Discussions with the patient should take into consideration the frequency that exchanges will be needed, the need for externalized hardware (with nephrostomy tubes), or severe urinary symptoms in the case of internal DJS. This review will highlight the current state of diversions in the setting of malignant ureteral obstruction.

Advances in ureteral stents

Ureteral stents are commonly used in urology. Every urologist is familiar with the problems that are associated with stents including infection, encrustation, and bothersome symptoms. These problems limit and affect the use of ureteral stents which are necessary, even in light of the problems they can cause. New designs such as a helically cut ureteral stent which is designed to stretch and conform to the ureter is designed to improve comfort. Drug-eluting designs with an antimicrobial (triclosan) are designed to reduce bacterial adherence to ureteral stents. Chlorhexidine, an antiseptic, has been incorporated into a stent and held in place by a slow release varnish to prevent biofilm formation. Combinations of antibiotics coated directly on the stent and administered systemically have been shown to reduce stent colonization both in vitro and in vivo. Gel-based ureteral stents were also showed to reduce bacterial infection and colonization. Bioabsorbable materials have also been designed to reduce infection, symptoms and prevent the forgotten stent syndrome. Newer designs including stents based on guidewire technology, gels, and a combination of self-expanding wire stents with polymer films are reviewed. There is hope on the horizon that new stents will be able to effectively tackle problems that are often seen with ureteral stents.

The Role of Tandem Double-J Ureteral Stents in the Management of Malignant Ureteral Obstruction

AIM

The management of malignant ureteral obstruction (MUO) is a challenging but common problem for urologists. The different techniques currently used to address this complicated issue include percutaneous nephrostomy, extra-anatomical stents, retrograde (single) stent insertion, and metallic stents. In those situations where single ureteral stent insertion has failed, retrograde tandem or twin ureteral stent (TUS) insertion can be completed. The aim of this study was to report our clinical experience and also assess the efficacy of TUS insertion within our tertiary referral center.

METHODS

Data were prospectively collected from patients requiring TUSs over an 8-year period between January 1, 2006, and December 31, 2014. A number of variables, including the improvement in renal function following TUS insertion, were recorded.

RESULTS

Twenty-two TUS insertion procedures were performed on 15 patients between the period of January 1, 2006, and December 31, 2014. The mean patient age was 68.0 years (39-85 years). There were 15 primary insertions as well as 7 subsequent stent changes. The average prenephrostomy creatinine was 428 μmol/L; an average improvement of 196 μmol/L was observed after percutaneous drainage. Serum creatinine after TUS remained stable on discharge, 214 μmol/L vs 227 μmol/L preoperatively, p = 0.34. Eleven patients died at a median 131 days post-TUS insertion. TUS failure occurred in three patients; this was characterized by rising creatinine and worsening hydronephrosis. Patients with failing TUS had a median life expectancy of 45.6 days compared with 162.5 days for those with functioning TUS (p < 0.05). Overall, the patency rate at 3 months was 80%.

CONCLUSION

TUS insertion is a technically efficient and effective procedure in the management of MUO, with the majority of patients treated dying of the underlying condition with functioning stents in situ.

Minimal invasive treatment of benign anastomotic uretero-ileal stricture in Hautmann neobladder with thermoexpandable ureteral metal stent

Technical challenges and increased morbidity of open reconstruction for uretero-ileal strictures have led to a search for minimal invasive treatments as an alternative solution. The insertion of a thermo-expandable ureteral Memokath 051^® metal stent across benign uretero-ileal anastomotic stricture in orthotopic neobladder has not been described in the English literature. Herein, we describe a case of a woman with a Hautmann neobladder and a 3.5 cm benign stricture of the right uretero-ileal anastomosis that was treated with insertion of a thermo-expandable ureteral Memokath 051^® metal stent.