The use of internal stents in chronic ureteral obstruction

Recent developments in ureteral stent: Substrate material, coating polymer and technology, therapeutic function

The ureteral stent is an effective treatment for clinical ureteral stricture following urological surgery, and the functional coating of the stent could effectively inhibit bacterial colonization and other complications. The present review provides an analysis and description of the materials used in ureteral stents and their coatings. Emphasis is placed on the technological advancements of functional coatings, taking into consideration the characteristics of these materials and the properties of their active substances. Furthermore, recent advances in enhancing the therapeutic efficacy of functional coatings are also reviewed. It is anticipated that this article will serve as a valuable reference providing insights for future research development on new drug-loaded ureteral stents.

Retrograde Ureteral Stents Versus Percutaneous Nephrostomy in the Management of Malignant Ureteral Obstruction: A Systematic Review and Meta-analysis

OBJECTIVE

To evaluate outcomes in cancer patients with ureteral obstruction by comparison of retrograde stenting and percutaneous nephrostomy techniques.

METHODS

Systematic review of all studies up to October 2023. Studies were identified from all major databases including MEDLINE, Cochrane, and EMBASE. All comparative studies between retrograde stenting and percutaneous nephrostomy were searched; studies with paediatric populations were excluded. Primary outcomes were procedure and intervention failure rates; secondary outcomes were infection, blockage, displacement, and unplanned exchange rates along with procedure time and length of stay.

RESULTS

Eighteen studies with 1228 patients contributed to the summative outcome. Percutaneous nephrostomy was statistically superior to retrograde stenting for procedure failure rate (P <.00001) and intervention failure rate (P =.0004). Retrograde stenting was statistically superior to percutaneous nephrostomy for displacement rates (P = .003), procedure time (P <.00001), and length of stay (P <.00001). Retrograde stenting showed no difference to percutaneous nephrostomy for infection rates (P = .94), blockage rates (P = .93), unplanned exchange rates (P = .48), CONCLUSION: There is no absolute superiority for retrograde stenting or percutaneous nephrostomy for malignant ureteral obstruction. Both techniques have their advantages and disadvantages, with some comparable outcomes; patients are key when selecting the best technique. Larger studies are required to assess the outcomes of both techniques.

Comparison of the efficacy and complications of tolterodine and α-adrenergic receptor blockers in improving ureteral stent-related symptoms: A systematic review and meta-analysis

OBJECTIVE

We conducted a systematic evaluation of the therapeutic efficacy and complications of tolterodine and α-adrenergic receptor blockers in alleviating ureteral stent-related symptoms.

METHODS

Until August 2023, we conducted a comprehensive literature search on PubMed, Embase, Web of Science, and Cochrane Library to identify randomized controlled trials evaluating the efficacy and complications of tolterodine and α-adrenergic receptor blockers in treating ureteral stent-related symptoms. Two reviewers independently screened studies and extracted data. The scores from various domains of the Ureteral Stent Symptom Questionnaire (USSQ) were summarized and compared, and statistical analysis was performed using RevMan 5.4.0 software.

RESULTS

A total of 8 studies met the inclusion criteria for our analysis. These studies were conducted at different centers. All studies were randomized controlled trials, involving a total of 487 patients, with 244 patients receiving α-adrenergic receptor blockers and 243 patients receiving tolterodine. The results showed that tolterodine demonstrated significantly better improvement in body pain (MD, 1.56; 95% CI [0.46, 2.66]; p = 0.005) (MD, 0.46; 95% CI [0.12, 0.80]; p = 0.008) (MD, 3.21; 95% CI [1.89, 4.52]; p = 0.00001) among patients after ureteral stent placement compared to α-adrenergic receptor blockers at different time points. Additionally, at 4 weeks, tolterodine showed superior improvement in general health (MD, 0.15; 95% CI [0.03, 0.27]; p = 0.01) and urinary symptoms (MD, 1.62; 95% CI [0.59, 2.66]; p = 0.002) compared to α-adrenergic receptor blockers, while at 6 weeks, tolterodine showed better improvement in work performance (MD, -1.60; 95% CI [-2.73, -0.48]; p = 0.005) compared to α-adrenergic receptor blockers. Additionally, the incidence of dry mouth (RR, 4.21; 95% CI [1.38, 12.87]; p = 0.01) is higher with the use of tolterodine compared to α-adrenergic receptor blockers. However, there were no significant statistical differences between the two drugs in other outcomes.

CONCLUSION

This meta-analysis suggests that tolterodine is superior to α-adrenergic receptor blockers in improving physical pain symptoms after ureteral stent placement, while α-adrenergic receptor blockers are more effective than tolterodine in enhancing work performance. Additionally, the incidence of dry mouth is higher with the use of tolterodine compared to α-adrenergic receptor blockers. However, higher-quality randomized controlled trials are needed to further investigate this issue.

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.

Evaluation of Renal Function and Stent Durability Following Resonance Stent Placement for Benign Disease

Introduction: The metal-based Resonance stent (RS) has traditionally been placed in patients with malignant ureteral obstruction; as such, the long-term utility of RS among patients with benign ureteral obstruction (BUO) remains underinvestigated. Methods: We retrospectively reviewed our database for patients with BUO who underwent RS placement between 2010 and 2020. The impact of chronic RS placement on renal function was evaluated by estimated serum creatinine-based glomerular filtration rate (eGFR), furosemide renal scan, and CT-based renal parenchymal volume measurement. The number of and reason for RS stent exchanges during the follow-up period, incidence of encrustation, and the average indwell time were recorded. A cost analysis of placing the RS vs a polymeric stent was performed. Results: Among 43 RS patients with BUO, at a mean follow-up of 26 months, there was no change in eGFR (p = 0.99), parenchymal volume (p = 0.44), or split renal function of the stent-bearing side on renal scan (p = 0.48). The mean RS indwell time was 9.7 months. Eleven patients (26%) underwent premature stent replacement (6 cases) or removal (5 cases). Stents in 9 patients (32%) were encrusted, of which 4 (44%) required laser lithotripsy. Overall, 25 patients (58%) and 12 patients (28%) had a mean stent indwell time of ≥6 months and ≥12 months, respectively. Placing an RS resulted in a 52%, 37%, and 5.6% cost reduction compared with a regular polymeric stent placement, where it was exchanged every 6, 4, or 3 months, respectively. Conclusions: RS deployment in the patient with a BUO results in cost-effective maintenance of renal function and of renal parenchymal volume at a mean follow-up of 2 years; however, only 28% of patients fulfilled the 1-year criterion for RS indwell time.

Comparison of Ureteral Stent Biomaterials: Encrustation Profile in Lithogenic Artificial Urine Models

Ureteral stent encrustation significantly limits indwelling time and can lead to downstream urological problems. However, no ideal polymeric biomaterials have been shown to completely resist encrustation in long-term urine exposure. Recently, 2-hydroxyethyl methacrylate (HEMA)-coated Pellethane was reported as a promising biomaterial resistant to encrustation. This study compared HEMA-coated Pellethane to commercially available stents under two different artificial urine environments. To evaluate the degree and composition of encrustation on HEMA-coated Pellethane, Boston Scientific Tria, Bard InLay Optima, Cook Universa Hydrogel, and Cook Black Silicone stents were used at various dwelling times in two different artificial urine environments. In a batch-flow model, samples of stents were suspended in an artificial urine solution (AUS) at 37 °C. Every 24 h for 11 weeks, 50% of the AUS would be replaced with fresh components using a programmable peristaltic pump system. The stent materials were removed at suitable time intervals and air-dried for 24 h under sterile conditions before follow-up analysis. SEM was used to assess the degree of encrustation, and inductively coupled plasma mass spectrometry (ICP-MS) was employed to quantify the encrusted compositions, specifically for calcium, magnesium, and phosphorus. We measured the weight gain over time due to encrusted deposits on the stents and quantified the amount of Ca, Mg, and P deposited on each encrusted stent. After the 11 week trial, HEMA-coated Pellethane showed the most average mass change. SEM showed that HEMA-coated Pellethane was fully encrusted in just 2 weeks in the AUS environments, and ICP-MS showed that Ca is the most abundant deposit. Among all the tested stents, Black Silicone performed the best. The two AUSs were formulated to encrust more rapidly than physiological conditions. HEMA-coated Pellethane is not an ideal stent material, while silicone is a promising material for advancing ureteral stents.

Hydronephrosis in patients with cervical cancer: An improved stent-change therapy for ureteral obstruction Stent-change for ureteral obstruction in cervical cancer

OBJECTIVE

Ureteral stent replacement is a routine treatment for hydronephrosis in patients with cervical cancer. We developed an improved ureteral stent-change operation for hydronephrosis in cervical cancer patients and compared its outcomes with traditional stent change procedures.

STUDY DESIGN

Clinical data of hydronephrosis in cervical cancer patients who were admitted to our hospital from August 2014 to October 2019 were analyzed. We retrospectively reviewed 131 cervical cancer patients, out of which 43 cases included patients in the improved operation group, whereas 88 patients with hydronephrosis followed the traditional ureteral stent-change operation for ureteral obstruction. The outcomes of the two procedures were compared using the propensity score matching method.

RESULTS

As opposed to the traditional ureteral stent change strategy, the patients in the improved group required shorter operation time (p = 0.001) and higher success rate (p = 0.004). The FIGO stage (p = 0.046), the level of ureteral obstruction (p = 0.027), radiotherapy history (p = 0.01), stent replacement times (≤2times or > 2times) (p = 0.001), and serum creatinine level (≤200 μmol/L or > 200 μmol/L) (p < 0.001) were significantly different between the two groups before propensity score matching. Propensity score matching analysis was used to eliminate the clinical differences of 43 patients in the traditional group; however, the span of visual hematuria during the surgical complications was not included (p = 0.026) in the results.

CONCLUSION

An improved ureteral stent change operation is an advanced treatment option for cervical cancer patients suffering from hydronephrosis. In contrast to traditional ureteral stent change techniques, our developed strategy lowers complications such as visual hematuria but improves the success.

Long-term Indwelling Tandem Polymeric Ureteral Stents for Benign Ureteral Obstruction

Objective: To assess the outcome of tandem polymeric internal stents (TIS) for benign ureteral obstruction (BUO). Material and Methods: We conducted a retrospective study that included all consecutive patients treated for BUO by means of TIS in a single tertiary center. Stents were replaced routinely every 12 months or earlier, when indicated. The primary outcome was permanent stent failure, and the secondary outcomes included temporary failure, adverse events, and renal function status. Kaplan-Meier and regression analyses were used to estimate outcomes, and logistic regression was used to assess the association between clinical variables and outcomes. Results: Between July 2007 and July 2021, 26 patients (34 renal units) underwent a total of 141 stent replacements, with median follow-up of 2.6 years (interquartile range [IQR] 0.75-5). Retroperitoneal fibrosis was the leading cause of TIS placement (46%). Permanent failures occurred in 10 (29%) renal units, and the median time to permanent failure was 728 days (IQR 242-1532). There was no association between preoperative clinical variables and permanent failure. Temporary failure occurred in four renal units (12%), which were treated by nephrostomy and eventually returned to TIS. Urinary infection and kidney injury rates were one event for every four and eight replacements, respectively. There was no significant alteration in serum creatinine levels throughout the study (p = 0.18). Conclusion: TIS provides long-term relief for patients with BUO and offers a safe and effective solution for urinary diversion, while avoiding the need for external tubes.

Cystoscopic surveillance protocol for ureteral stents used to manage malignant ureteral obstruction: reducing morbidity of frequent stent changes

PURPOSE

To evaluate a cystoscopic surveillance protocol used to mitigate morbidity associated with chronic ureteral stents for malignant ureteral obstruction (MUO).

MATERIALS AND METHODS

A retrospective cohort study was conducted at a tertiary, referral centre of consecutive MUO patients who were initially managed with a ureteral stent and subsequently followed using a cystoscopic 'MUO stent surveillance protocol'. Multivariable regression models evaluated factors associated with the following outcomes: number of stent changes, time to first stent change, and overall survival.

RESULTS

A total of 120 patients from May 2009 to December 2019 were included; mean age was 63 years, majority (76.7%) were female, and median follow-up for stented patients was 184 days. Majority (72%) of patients did not require a stent change at 3-months follow-up. Only 32% (19/60) required a stent change at their 6-month stent surveillance cystoscopy. Median time to first stent change was 158 days. Of 344 total number of stent surveillance cystoscopies performed, 39.5% (136/344) involved a stent change. Patients with a history of pelvic radiation (subdistribution hazard rate [sHR] 2.12, 95% CI 1.23 to 3.67, p=0.007) and with a history of bowel resection (sHR 2.06, 95% CI 1.05 to 4.03, p=0.036) were independently associated with earlier stent changes. No patients in the MUO stent surveillance protocol required ancillary procedures to deal with encrusted stents.

CONCLUSIONS

A cystoscopic 'MUO stent surveillance protocol' can reduce the morbidity and health care expenditures associated with stent changes among MUO patients, with median time to first stent change being 158 days and only 40% of surveillance cystoscopies involving a stent change. The protocol is safe as no patients required ancillary procedures to manage an encrusted stent while on surveillance. Patients with a history of pelvic radiation or bowel resection were more likely to require a stent change during their stent surveillance visits.

Tumor stent for chronic ureteral obstruction: Which are predictors of stent failure?

PURPOSE

To identify predictors of UROSOFT® tumor stent failure. According to the manufacturer, this reinforced ureteral stent has a maximal dwell time of 6 months. Nonetheless, stent failure may reduce this maximal dwell time.

METHODS

All patients undergoing first-time UROSOFT® tumor stent insertion in our institution between 2010 and 2018 were considered for this retrospective analysis. Primary endpoint was stent failure and defined as premature stent exchange or percutaneous nephrostomy insertion.

RESULTS

182 patients were available for analysis. Median age was 68 years. Causes for tumor stent placement were extrinsic ureteral obstruction in 144 patients (79 %) and intrinsic obstruction in 38 patients (21 %). Tumor stent failure free survival estimates at 1, 2, 3, 4 and 5 months were 89%, 83%, 76%, 65% and 52%, respectively. Patients with stent failure had significantly higher grade of hydronephrosis, higher urinary culture bacterial growth, higher serum WBC, higher CRP and lower eGFR at the time of re-intervention, compared to patients who underwent regular stent exchange. Of all baseline and perioperative parameters, we found bilateral insertion, intrinsic ureteral obstruction, and urinary tract infection (UTI) at time of tumor stent insertion to be significant and independent predictors of stent failure (all p < 0.05).

CONCLUSION

Despite a theoretical maximal dwell time of 6 months, around 50% of all cases are subject to premature stent failure. Predictors of stent failure are bilateral insertion, intrinsic ureteral obstruction, and UTI at the time of tumor stent insertion. Preoperative antibiotic therapy may impact on stent failure rate.

Placement of Resonance Stent for Malignant or Benign Ureteral Obstruction

The aim of this article is to illustrate a step-by-step guide to placement of Resonance^® metallic ureteral stent (Cook Medical, Bloomington, IN) for management of malignant or benign ureteral obstruction. In this article, the steps of operating room setup, patient positioning, gaining access to the upper urinary tract, and endoscopic and fluoroscopic placement of a Resonance ureteral stent are described.

Safely increasing nephro-ureteric stent exchange intervals, resulting in significant cost savings for the interventional radiology suite, a 2-year experience in a tertiary referral centre

Aim

To evaluate the nephro-ureteric stent (NUS) insertion and exchange practice in a tertiary referral cancer centre, and determine the safety and compliance with current guidelines. We also reviewed if increasing exchange time interval from 6 to 12 weeks was safe, and if this could be adopted into our local guidelines.

Methods

A retrospective review was performed covering 24 months from January 2017 to December 2018. All NUS insertions and exchanges performed in that period were analysed, including the number of exchanges the patient underwent, the time between subsequent exchanges, and the screening time. We also reviewed the indications for stent insertion, possible causes for failed stent exchange, and factors which led to significant delays in stent exchanges for some patients. A scatterplot of screening time versus time in situ was derived and correlation analysis performed using the Pearson coefficient.

Results

Thirty-two patients underwent de novo NUS insertion during the period, and 102 NUS exchanges were performed. The interval between stent exchanges ranged from 1 to 40 weeks, with a mean of 12.3 weeks (SD = 8.96 weeks). Screening time ranged from 33 s to 17 min, with a mean of 3 min 50 s (SD = 3 min 35 s). There were 100 successful exchanges, and two failed exchanges, accounting for 1.9% of total exchanges. In both failed cases, the reason for failed exchange was due to a prolonged period between exchanges (6 months in both cases). The reason for delay for stent exchange was due to non-attendance for scheduled appointments. There was a weakly positive correlation coefficient of 0.06 (screening time versus time period between insertions); however, this was not statistically significant (p = 0.81).

Conclusion

In this retrospective review, we have demonstrated that the recommended 6-week period between stent exchanges is unnecessary in the vast majority of cases, and that a longer interval between NUS exchanges, e.g. 8–12 weeks, is safe for the patient, and reduces screening time. This reduction in procedures also provides a significant potential saving to the radiology department in both monetary expense and limited angiography suite time.

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.

Percutaneous Removal of Retained Metallic Ureteral Stent with a Looped Polytetrafluoroethylene-Coated Guidewire

Background: Ureteral stricture disease is a troubling urologic issue that can be managed with surgical reconstruction or, more conservatively, with chronic nephrostomy tubes or ureteral stents. These indwelling tubes require exchanges and are prone to complications such as encrustation or stent failure. Metallic ureteral stents are designed to be more resistant to extrinsic compression and allow for exchanges at longer intervals. However, encrustation or tissue ingrowth can occur with these stents as well. The removal of encrusted or embedded metallic ureteral stents poses a difficult clinical scenario. We present a case of an encrusted metallic stent embedded in a proximal ureteral stricture requiring percutaneous endoscopic removal with a novel looped-wire technique. Case Presentation: A 50-year-old Caucasian man with bilateral ureteral stricture disease, managed with chronic indwelling metallic stents, failed retrograde removal on the right during routine exchange. Staged procedures with percutaneous nephrostomy, followed by combined percutaneous antegrade and retrograde endoscopy were required to observe and access the embedded stent. The exposed metallic surface was unable to be grasped by available instruments through flexible endoscopy. Under endoscopic control with fluoroscopic guidance, a polytetrafluoroethylene (PTFE)-coated guidewire was looped around the metallic stent. With gentle traction on the wire loop, the embedded stent curl was delivered out of the stricture and into the renal pelvis from where it was extracted carefully with graspers inserted through a rigid nephroscope. Follow-up antegrade fluoroscopic studies with contrast showed no extravasation. Conclusion: Percutaneous removal of metallic stents retained within the ureter has unique challenges. We present a novel method of extraction of a retained metallic stent with a looped PTFE-coated guidewire, which may safely and effectively be used in complex situations.

Estimation of successful capping with complete aspiration of bladder via nephroureterostomy tube

BACKGROUND

Ureteral stent and nephroureterostomy tube (NUT) are treatments of ureteral obstruction. Ureteral stent provides better quality of life. Internalization of NUT is desired whenever possible.

AIM

To assess outcomes of capping trial among cancer patients with complete aspiration of retained contrast from bladder via NUT.

METHODS

Our Institutional Review Board approved retrospective review of all NUT placement, NUT exchange and conversion of nephrostomy catheter into NUT performed during June 2013 to June 2015 (n = 578). Cases were excluded due to lack of imaging of bladder (n = 37), incomplete aspiration of bladder (n = 324), no attempt at capping NUT (n = 166), and patients with confounding factors interfering with results of capping trial including non-compliant bladder, bladder outlet obstruction and catheter malposition (n = 14). Study group consisted of 37 procedures in 34 patients (male 19, female 15, age 2-83 years, average 58, median 61) most with cancer (prostate 8, endometrial 5, bladder 4, colorectal 4, breast 2, gastric 2, neuroblastoma 2, cervical 1, ovarian 1, renal 1, sarcoma 1, urothelial 1 and testicular 1) and one with Crohn’s disease. Medical records were reviewed to assess outcomes of capping trial. Exact 95% confidence intervals (95%CI) were calculated.

RESULTS

Among patients with complete aspiration of retained contrast, 30 (81%, 95%CI: 0.65-0.92) catheters were successfully capped (range 12-94 d, average 40, median 24.5) until planned conversion to internal stent (23), routine exchange (5), removal (1) or death unrelated to catheter (1). Seven capping trials (19%, 95%CI: 0.08-0.35) were unsuccessful (range 2-22 d, average 12, median 10) due to leakage (3), elevated creatinine (2), fever/hematuria (1) and nausea/vomiting (1).

CONCLUSION

Capping trial success among patients with complete aspiration of retained contrast/urine from bladder via NUT appears high.

Long-Term Follow-Up of Yearly Replaced Double Internal Stents for Extrinsic Malignant Ureteral Obstruction

Introduction: To assess long-term outcomes of double internal stents (DIS) for the relief of external malignant ureteral obstruction (MUO). Materials and Methods: DIS (7F each; 12-month indwelling time) were inserted under general anesthesia in 62 consecutive patients (75 renal units) with MUO during 2007-2018. Surveillance was performed every 3 months, and stents were exchanged routinely every year. The need for permanent stent retrieval was considered stent failure. Maintenance of stent patency and disease-specific survival (DSS) were estimated (Kaplan-Meier). Risk factors were also assessed (univariate and multivariable Cox regression analyses). Results: The median follow-up was 27 months (interquartile range [IQR] 20-27). The most frequent tumors causing obstruction were colorectal and ovarian cancers. Six patients (10%) had stent failure caused by sepsis, creatinine elevation, or hematuria. The average time to failure was 15 months (range 1-27). A history of radiation and an estimated glomerular filtration rate (eGFR) ≤45 mL/(min/1.73 m²) were associated with stent failure (p = 0.038 and p = 0.001, respectively). Thirty-nine patients died with a median DSS of 21 months (IQR 8.6-not reached). Multivariate analysis identified eGFR ≤60 mL/(min/1.73 m²) (hazard ratio [HR] 2.1, 95% confidence interval [CI] 1.1-4.2, p = 0.02) and need for balloon dilation (HR 2.1, 95% CI 1.1-4.1, p = 0.02) as independent predictors for disease-related mortality. Twenty-six patients (42%) had stent-related complications, for example, irritative symptoms, hematuria, and infections, of whom only two failed. Conclusions: One-year indwelling DIS provide effective long-term relief of MUO and represent a simple and effective alternative to other methods of urinary diversion. They avoid the need for external tubes and contribute to improved patient satisfaction.

Symptom and cost evaluation of ureteric stent extraction using strings versus flexible cystoscopy at a single high-volume centre

Background:

This study evaluated ureteric stent symptoms using a modified ureteric stent symptom questionnaire (USSQ) for patients undergoing stent removal by either flexible cystoscopy, or manual, healthcare worker lead string extraction.

Methods:

Patients completed a stent symptom questionnaire derived from the USSQ. Mean data were compared between groups using paired Student’s t-tests. Data are presented as mean ± SD with associated p-values. A departmental cost analysis was undertaken.

Results:

Ninety patients completed questionnaires, 30 undergoing flexible cystoscopy and 60 string extraction. Six stents with strings were removed early (days 1–5, 6.67%, four female and two male). There were no adverse events recorded for this group. Men undergoing string extraction had significantly less pain (2.47 ± 1.88) compared to men undergoing flexible cystoscopic removal (5.67 ± 2.27, p < 0.001). There was no significant difference in pain scores for women undergoing string and flexible cystoscopic stent removal (3.56 ± 2.56 versus 3.66 ± 3.14, p > 0.90). The mean duration of stents left in situ was significantly less in the string group (10.1 ± 5.3 versus 26.5 ± 14.1 days, p < 0.001). Urinary tract infection rates did not differ between the string and the cystoscopy groups (3.7% ± 0.19 versus 2.78% ± 0.46, p > 0.90). The haematuria rates were 32.14% ± 0.47 and 66.67% ± 0.5, respectively ( p < 0.001). In our study, 60 flexible cystoscopies were avoided, saving over £67,000 at the institution within our study period.

Conclusions:

In our small study, stents removed with strings reduced pain scores in men, the duration of an indwelling ureteric stent, and cost to the health service.

Level of evidence:

2b

Antegrade insertion of a double J catheter in the treatment of malignant ureteral obstruction: a retrospective analysis of the results obtained with a modified technique at a university hospital

Objective

To analyze the results obtained with a modified antegrade double J catheter insertion (JJ stenting) technique in patients with urinary tract obstruction due to malignancy.

Materials and Methods

This was a retrospective analysis of data collected from patients undergoing antegrade JJ stenting for malignant ureteral obstruction in the interventional radiology department of our institution between March 1, 2017 and May 31, 2019.

Results

Antegrade JJ stenting was performed in 32 patients (20 women and 12 men). The mean age was 66.2 years among the females and 61.5 years among the males. A total of 53 antegrade JJ stenting procedures were performed. The procedure was successful in 50 cases and failed in 3 (due to migration of the double J catheter in 2 and due to technical failure in 1). Complications occurred in 3 patients (low back pain, in 1, subcapsular hematoma, in 1, and pyelonephritis, in 1). The procedure time ranged from 14 min to 55 min.

Conclusion

In patients with ureteral obstruction due to malignancy, antegrade JJ stenting is safe and effective. The technique selected in our study is easily reproduced and can be performed by a trained professional.

A Microfluidic-Based Investigation of Bacterial Attachment in Ureteral Stents

Obstructions of the ureter lumen can originate from intrinsic or extrinsic factors, such as kidney stones, tumours, or strictures. These can affect the physiological flow of urine from the kidneys to the bladder, potentially causing infection, pain, and kidney failure. To overcome these complications, ureteral stents are often deployed clinically in order to temporarily re-establish urinary flow. Despite their clinical benefits, stents are prone to encrustation and biofilm formation that lead to reduced quality of life for patients; however, the mechanisms underlying the formation of crystalline biofilms in stents are not yet fully understood. In this study, we developed microfluidic-based devices replicating the urodynamic field within different configurations of an occluded and stented ureter. We employed computational fluid dynamic simulations to characterise the flow dynamic field within these models and investigated bacterial attachment (Pseudomonas fluorescens) by means of crystal violet staining and fluorescence microscopy. We identified the presence of hydrodynamic cavities in the vicinity of a ureteric occlusion, which were characterised by low levels of wall shear stress (WSS < 40 mPa), and observed that initiation of bacterial attachment occurred in these specific regions of the stented ureter. Notably, the bacterial coverage area was directly proportional to the number of cavities present in the model. Fluorescence microscopy confirmed that the number density of bacteria was greater within cavities (3 bacteria·mm^-2) when compared to side-holes of the stent (1 bacterium·mm^-2) or its luminal surface (0.12·bacteria mm^-2). These findings informed the design of a novel technological solution against bacterial attachment, which reduces the extent of cavity flow and increases wall shear stress over the stent's surface.

Encrusted Ureteral Stent in a Spanish Speaking Female: A Case of a Forgotten Stent Lost in Translation

Ureteral stents are used to establish patency in a non-draining ureter, as they are commonly placed in etiologies such as ureteral obstruction and urological surgery. One complication that occurs with stent placement is the absence of follow-up to remove the device. This may be due to a myriad of reasons, including non-compliance and lack of patient education. Forgotten stents can pose a dangerous scenario, as a retained stent can lead to urinary tract obstruction, urosepsis, and even kidney failure. In this study, we present a case of a Spanish-speaking patient with a retained ureteral stent who presented with left flank pain due to not understanding the need for stent follow-up.

Symptoms Associated With Long-term Double-J Ureteral Stenting and Influence of Biofilms

OBJECTIVE

To assess the symptoms associated with long-term Double-J ureteral stenting including the influence of biofilms on ureteral stents.

METHODS

Patients with long-term (>8 weeks) uni- or bilateral ureteral stents completed the Ureteral Stent Symptoms Questionnaire (USSQ) at the day of stent exchange. Repeated assessment of patients was possible to allow for analysis of intraindividual changes. Assessment of biofilm mass on the stents was performed according to a validated method, its correlation with the USSQ total score was defined as primary outcome. Secondary outcomes included further analyses of stent-associated symptoms and their temporal course.

RESULTS

A total of 87 stent indwelling periods in 35 patients were investigated. Median USSQ total score did not differ significantly between unilateral and bilateral stenting (42 vs 39 points; P = .17). An increasing total stent treatment time up to study inclusion did not correlate with the USSQ total score, but was significantly correlated with less urinary symptoms and a better quality of life. USSQ total score and subscores within individual patients did not significantly increase or decrease over the sequence of stent indwelling periods. Higher total biofilm masses were not associated with higher USSQ total scores or subscores.

CONCLUSION

Long-term Double-J stenting provides a valuable treatment option, if stent-associated symptoms are low during the initial indwelling period. Thus, symptoms remain stable over the long-term course and the majority of patients are satisfied with the treatment. Furthermore, biofilm formation on ureteral stents does not seem to be the relevant driver of symptoms.

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.

A Comparison of Clinical Outcomes of Operating Room Versus Office-based Ureteral Stenting With the Novel Use of Nitrous Oxide Sedation

OBJECTIVES

To examine the safety and effectiveness of placing ureteral stents in an office-based setting vs in the operating room (OR).

METHODS

A retrospective chart review was performed to examine outcomes, specifically complication rate, unanticipated hospitalizations, and stent failures, when patients received JJ stents in the clinic procedure suite, using local analgesia and/or nitrous oxide gas analgesia, compared to patients who had ureteral stents placed in the OR, typically with general anesthesia. Additionally, multivariable analysis was performed to determine predictors of complications.

RESULTS

Around 565 procedures were performed in the clinic and 179 were performed in the OR. The complication rate for the clinic group was 4.1%, compared to 7.8% in the OR group. Unplanned admissions to the hospital occurred after 3.0% of clinic procedures and 9.5% of OR procedures. Stent placements failed in 1.1% of clinic procedures and 0.56% of OR procedures. Clinic procedure time was 10 minutes vs 12 minutes in the OR (P <0.01). Clinic vs OR setting was not predictive of complications (P = 0.99). We did not identify factors that impacted complication rate in ureteral stent placement in the clinic vs OR setting. Notably, the procedure time for a clinic stent placement was significantly shorter than the OR stent placement.

CONCLUSIONS

This study demonstrates excellent outcomes with a novel approach to a standard procedure, with shorter procedure time and no difference in complication rates.

Macrophage-secreted TGF-β1 contributes to fibroblast activation and ureteral stricture after ablation injury

Iatrogenic injury to the healthy ureter during ureteroscope-guided ablation of malignant or nonmalignant disease can result in ureteral stricture. Transforming growth factor (TGF)-β1-mediated scar formation is considered to underlie ureteral stricture, but the cellular sources of this cytokine and the sequelae preceding iatrogenic stricture formation are unknown. Using a swine model of ureteral injury with irreversible electroporation (IRE), we evaluated the cellular sources of TGF-β1 and scar formation at the site of injury and examined in vitro whether the effects of TGF-β1 could be attenuated by pirfenidone. We observed that proliferation and α-smooth muscle actin expression by fibroblasts were restricted to injured tissue and coincided with proliferation of macrophages. Collagen deposition and scarring of the ureter were associated with increased TGF-β1 expression in both fibroblasts and macrophages. Using in vitro experiments, we demonstrated that macrophages stimulated by cells that were killed with IRE, but not LPS, secreted TGF-β1, consistent with a wound healing phenotype. Furthermore, using 3T3 fibroblasts, we demonstrated that stimulation with paracrine TGF-β1 is necessary and sufficient to promote differentiation of fibroblasts and increase collagen secretion. In vitro, we also showed that treatment with pirfenidone, which modulates TGF-β1 activity, limits proliferation and TGF-β1 secretion in macrophages and scar formation-related activity by fibroblasts. In conclusion, we identified wound healing-related macrophages to be an important source of TGF-β1 in the injured ureter, which may be a paracrine source of TGF-β1 driving scar formation by fibroblasts, resulting in stricture formation.

Percutaneous antegrade ureteral stent placement: single center experience

PURPOSE

We aimed to present our clinical experience with percutaneous antegrade ureteral stent placement in a single center.

METHODS

Electronic records of patients who underwent percutaneous image-guided ureteral stent placement between September 2005 and April 2017 were reviewed. A total of 461 patients (322 males, 139 females; age range, 19-94 years; mean age, 61.4±15 years) were included in the study. Patients were classified into two main groups: those with neoplastic disease and those with non-neoplastic disease. Failure was defined as persistence of high level of serum creatinine or an inability to place stents percutaneously. Postprocedural complications were grouped as percutaneous nephrostomy and stent placement related complications.

RESULTS

A total of 727 procedures in 461 patients were included in the study: 654 procedures (90%) in 407 patients (88.3%) were in the neoplastic group and 73 procedures (10%) in 54 patients (11.7%) were in the non-neoplastic group. Our technical success rates were 97.7% and 100% and complication rates were 3.1% and 4.1% in neoplastic and non-neoplastic groups, respectively. Seven stents retrievals and 112 balloon dilatations were performed successfully.

CONCLUSION

Percutaneous antegrade ureteral stent placement is a safe and effective method for management of ureteral injuries and obstructions due to both malignant and benign causes when the retrograde approach has failed.

Ureteral stents for malignant extrinsic ureteral obstruction: outcomes and factors predicting stent failure

BACKGROUND

This study investigated the clinical outcomes of stent placement for malignant extrinsic ureteral obstruction (MUO) and predictive factors for stent failure.

METHODS

We retrospectively analyzed clinical data for 91 patients with radiologically significant hydronephrosis due to MUO who underwent successful stent placement. In total, 132 ureters were stented for the decompression. Factors related to stent failure were analyzed with a Cox proportional hazards model.

RESULTS

Stent failure occurred in 25 ureters in 20 patients. The median interval to failure was 63 days. The multivariate analysis showed that the significant predictors of stent failure were bladder invasion and severe hydronephrosis before the stent insertion. The patients were divided into three groups based on these two factors: low-risk (neither factor; 85 patients), intermediate-risk (one factor; 37), and high-risk (both factors; 10). The median stent failure-free survival rate at 3 months was 94.8% in the low-risk, 71.8% in the intermediate-risk and 55.6% in the high-risk group, respectively. Of the ureters with stent failure, there was successful re-replacement of internal stents in 3 low-risk, 6 intermediate-risk and no high-risk ureters. Replacement by nephrostomy was done in 2 low-risk, 5 intermediate-risk and 7 high-risk ureters.

CONCLUSION

The patients considered at low-risk could be managed without stent failure by internal stenting. However, the patients at high-risk may require the consideration of nephrostomy or other alternatives as the initial treatment. Our stratification model may allow better risk stratification for patients with regard to ureteral stenting, helping to identify patients for whom ureteral stenting is indicated.

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.

Quarter Century Management of Chronic Ureteropelvic Junction Obstruction in a Solitary Kidney with a Ureteral Stent

Background: The ureteral stent provides a conduit for urinary drainage from the kidney to the bladder and is integral to contemporary urologic practice. A ureteral stent is often utilized in acute conditions to prevent or overcome obstruction; however, in nonsurgical patients, because of disease or preference, a ureteral stent may be used as a last resort for long-term management of a stricture in lieu of a nephrostomy tube. This case highlights a patient whose chronic ureteral obstruction has been managed with an indwelling ureteral stent for 25 years; remarkably, stent exchanges are currently required only every 2 years.

Case Presentation: A 33-year-old man initially presented with a solitary left kidney and a ureteropelvic junction obstruction. The patient's right kidney was nonfunctioning since childhood because of a presumed ureteropelvic junction obstruction with grade IV hydronephrosis. The patient underwent two failed open repairs of the left kidney in the 1980s, resulting in a totally intrarenal, constricted renal pelvis; an endopyelotomy in 1992 also failed and required angioembolizaton of a segmental renal vessel. The patient refused any further surgical procedures and thus has been managed exclusively with a 7/14F × 28 cm endopyelotomy stent (Boston Scientific^®) for 25 years; the interval between stent changes was slowly expanded until they are now being done at 2-year intervals. The patient has not developed recurrent urinary tract infections, stent colic, or stent encrustation.

Conclusion: Patients who require chronic indwelling ureteral stents are rare. In this situation, with careful monitoring, the interval between stent exchanges was extended to 2 years, thereby precluding a chronic nephrostomy tube.

The burden of chronic ureteral stenting in cervical cancer survivors

PURPOSE

Ureteral obstruction in cervical cancer occurs in up to 11% of patients, many of whom undergo ureteral stenting. Our aim was to describe the patient burden of chronic ureteral stenting in a population-based cohort by detailing two objectives: (1) the frequency of repeat procedures for ureteral obstruction; and, (2) the frequency of urinary adverse effects (UAEs) (e.g., lower urinary tract symptoms, flank pain).

MATERIALS AND METHODS

From SEER-Medicare, we identified 202 women who underwent ureteral stent placement prior to or following cervical cancer treatment. The frequency of repeat procedures and rate ratios were compared between treatment modalities. The rates and rate ratios of UAEs were compared between our primary cohort (stent + cervical cancer) and the following groups: no stent + cervical cancer, stent + no cancer, and no stent + no cancer. The "no cancer" group was drawn from the 5% Medicare sample.

RESULTS

117/202 women (58%) underwent >1 stent procedure. The frequency of additional procedures was significantly higher in patients who received radiation as part of their treatment. UAEs were very common in women with stent + cancer. The rate of UTI was 190 (per 100 person-years), 67 for LUTS, 42 for stones, and 6 for flank pain. These rates were 3-10 fold higher than in the no stent + no cancer control group; rates were also higher than in the no stent + cancer and the stent + no cancer women.

CONCLUSIONS

The burden of disease associated with ureteral stents is higher than expected and urologists should be actively involved in stent management, screening for associated symptoms and offering definitive reconstruction when appropriate.

Outcomes of Ureteral Stent Placement for Hydronephrosis in Patients with Gynecological Malignancies

OBJECTIVE

We examined the outcomes of patients undergoing ureteral stent placement for hydronephrosis that occurred during treatment for gynecological malignancies.

MATERIALS AND METHODS

From January 2004 to December 2009, we enrolled 33 patients with 45 ureters undergoing ureteral stent placement for hydronephrosis which occurred during treatment for gynecological malignancies. We examined the outcomes of the patients after stent placement.

RESULTS

The causes of hydronephrosis were obstruction of the urinary tract by a tumor (n = 22), obstruction due to lymph node swelling (n = 6), ureteral stenosis after radiation therapy (n = 4), and others (n = 1). The ureteral stent was inserted into both ureters in 12 cases, and into one ureter in 21 cases. Ureteral stents were replaced 1-26 times during the observation period (median 3 times). Eighteen (40%) ureteral stents were removed. The reasons for ureteral stent removal were hydronephrosis improvement (11 ureters, 24.4%), a change to nephrostomy (cystectomy: 1 ureter, progression of ureteral stenosis: 2 ureters), renal atrophy (3 ureters), and ureteral dilatation (1 ureter). All of the cases in which ureteral stent withdrawal due to hydronephrosis improvement were cases in which the ureter was compressed by a tumor and were lower ureteral obstructions. Twenty-one patients (64%) died due to cancer after stent placement. The periods from the first stent placement to death ranged from 1 to 58 months (median 18 months).

CONCLUSION

Ureteral stent placement was associated with a poor prognosis in patients with gynecological malignancies. There were a few cases in which stent withdrawal became possible due to the improvement of hydronephrosis. In such cases, the withdrawal rate varied according to the cause and obstructive level.

Change of Renal Parenchymal Width in Patients with Unilateral Ureteral Stent: A Bicenter Retrospective Study

PURPOSE

To determine whether kidney sizes were changed after ureteral stents were instilled, and if so, what parameters were significant.

METHODS

Parenchymal width (PW) of 98 patients with unilateral ureteral stents was measured from the coronal view of CT scans for both stented and unstented contralateral kidney. The mean PW and % change of mean PW were calculated before stenting and at the time of last stent change. Estimated glomerular filtrate rate (eGFR) was recorded as well.

RESULTS

The mean duration of ureteral stent indwelled was 15.6 ± 10.2 (mean ± SD) months. The change of mean PW of stented kidneys and unstented contralateral kidneys was -16.9 ± 16.4 (mean ± SD)% and 3.6 ± 10.7%, respectively. eGFR before and at the time of the last stent change did not show significant difference (p = 0.294). Duration of ureteral stent indwelled was found to be inversely related to the % change of mean PW (Spearman's correlation coefficient = -0.291, p < 0.001).

CONCLUSIONS

For unilateral ureteral obstruction, kidney size was decreased over time in spite of indwelling ureteral stent. This finding can be overlooked by clinicians due to compensatory growth of contralateral kidney and resultant normal eGFR.

The thermoexpandable nitinol stent: a long-term alternative in patients without nephropathy or malignancy

OBJECTIVE

The aim of this study was to investigate the long-term outcome of a thermoexpandable nickel-titanium nitinol ureteral stent (Memokath 051™) and to identify individual risk factors for failure.

MATERIALS AND METHODS

This retrospective single-centre study included 125 patients who underwent implantation of the self-expandable Memokath 051 stent. Complications, indwelling time and reason for explantation were recorded. Analyses were stratified by gender, age, body mass index, American Society of Anesthesiologists score, estimated glomerular filtration rate (eGFR), side, localization and cause of the stricture.

RESULTS

In total, 91 out of 125 patients (73%) were available for analysis. Median indwelling time was 355 days (range 7-2125 days). Most stents were removed because of dislocation (42%) or occlusion (40%). Stent removal was rarely performed because of infection (3%). Patients with sufficient renal function (eGFR ≥60 ml/min/1.73 m²) showed increased indwelling times compared with those with nephropathy (386 vs 317 days; p < 0.01). Patients with active malignant disease showed reduced patency time compared with strictures of benign origin (455 vs 190 days; p < 0.01).

CONCLUSIONS

This thermoexpandable nitinol stent offers safe mid-term treatment of ureteric strictures, especially in patients without active malignancy and with good renal function.

Biodegradation behavior of magnesium and ZK60 alloy in artificial urine and rat models

In this work, the biodegradable and histocompatibility properties of pure Mg and ZK60 alloy were investigated as new temporary implants for urinary applications. The corrosion mechanism in artificial urine was proposed using electrochemical impedance spectroscopy and potentiodynamic polarization tests. The corrosion potential of pure magnesium and ZK60 alloy were −1820 and −1561 mV, respectively, and the corrosion current densities were 59.66 ± 6.41 and 41.94 ± 0.53 μA cm⁻², respectively. The in vitro degradation rates for pure Mg and ZK60 alloy in artificial urine were 0.382 and 1.023 mm/y, respectively, determined from immersion tests. The ZK60 alloy degraded faster than the pure Mg in both artificial urine and in rat bladders (the implants of both samples are ø 3 mm × 5 mm). Histocompatibility evaluations showed good histocompatibility for the pure Mg and ZK60 alloy during the 3 weeks post-implantation in rat bladders, and no harm was observed in the bladder, liver and kidney tissues. The results provide key information on the degradation properties and corrosion mechanism of pure Mg and ZK60 alloy in the urinary system.

•

ZK60 obtained loose corrosion product layer with poor corrosion resistance in AU.

•

ZK60 showed a faster degradation rate than Mg in artificial urine and bladder of rat.

•

Mg and ZK60 alloy showed good histocompatibility for the bladder model of rat.

Magnetically Controlled Endourethral Artificial Urinary Sphincter

Urinary incontinence is a largely spread disfunction that affects more than 300 million people worldwide. At present, no technological solutions are able to restore continence in a minimally invasive and effective way. In this article the authors report the design, fabrication, and testing of a novel artificial endourethral urinary sphincter able to fully restore continence. The device can be inserted/retracted in a minimally invasive fashion without hospital admission, does not alter the body scheme and can be applied to both women and men. The device core is a unidirectional polymeric valve and a magnetically activated system able to modulate its opening pressure. Bench tests and ex vivo tests on a human cadaver demonstrated that the device is able to fully restore continence and to allow urination when desired. Overall, the proposed system shows a high potential as a technological solution able to restore a normal daily life in patients affected by urinary incontinence.

[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.

Use of cystourethroscopy to remove an indwelling double-J ureteral stent 6 years following simultaneous radical sigmoid colon cancer and partial bladder resection: A case report

Ureteral stents are widely used to ensure good urinary drainage and to relieve obstruction, pain and infection during urologic procedures. However, long-term indwelling ureteral stents can cause various complications, such as encrustation, hematuria and infection. Here, the case of an 88-year-old man who had undergone simultaneous radical resection of sigmoid colon cancer and partial resection of the bladder 6 years prior is presented. The patient complained of urinary frequency and urgency, dysuria and intermittent fever. A kidney ureter bladder X-ray examination revealed the presence of an entire coiled double-J stent with calculi from the kidney to the bladder. A computed tomography scan revealed mild hydronephrosis of the left kidney and one J end of the stent in the bladder. The stent was removed successfully by cystourethroscopy and holmium laser lithotripsy. This report describes the clinical experience of the removal of a long-term stent by endoscopic manipulation.

In vitro and in vivo corrosion and histocompatibility of pure Mg and a Mg-6Zn alloy as urinary implants in rat model

Pure Mg and a Mg-6wt.% Zn alloy were investigated as potential candidates for biodegradable implants for the urinary system. The in vitro corrosion behavior was studied by potentiodynamic polarization and immersion tests in simulated body fluid (SBF) at 37°C. The in vivo degradation and histocompatibility were examined through implantation into the bladders of Wistar rats. The alloying element Zn elevated the passivation potential and increased the cathodic current density. Both in vitro and in vivo degradation tests showed a faster corrosion rate for the Mg-6Zn alloy. Tissues stained with hematoxylin and eosin (HE) suggested that both pure Mg and Mg-6Zn alloy exhibited good histocompatibility in the bladder indwelling implantation and no differences between pure Mg and Mg-6Zn groups were found in bladder, liver and kidney tissues during the 2weeks implantation. Overall, this work presented instructive information on the degradation properties and histocompatibility of pure Mg and the Mg-6Zn alloy in the urinary system.

Urinary Drainage Procedures in Interventional Radiology

Urinary drainage procedures are used to treat a wide range of clinical situations including pyonephrosis, preservation of renal function in patients with ureteral obstruction, as a means to access the collecting system for stone retrieval or lithotripsy and to divert urine from a distal leak or fistula. Several different drainage devices are available and include those that provide obligatory external drainage (nephrostomy), both internal and external drainage (nephroureteral stent) and internal drainage (double-J stent). Each device requires some maintenance and effort on the patient's part-from having to undergo routine exchange of double-J stents every 3-6 months to the daily management of an external catheter and drainage bag. Ideally, the desired outcome can be attained with minimal effect on patient lifestyle. In this article, we present our approach to patients who require urinary drainage, with a focus on choosing and placing the most appropriate device in a variety of clinical scenarios.

Use of percutaneous nephrostomy and ureteral stenting in management of ureteral obstruction

The management options for ureteral obstruction are diverse, including retrograde ureteral stent insertion or antegrade nephrostomy placement, with or without eventual antegrade stent insertion. There is currently no consensus on the ideal treatment or treatment pathway for ureteral obstruction owing, in part, to the varied etiologies of obstruction and diversity of institutional practices. Additionally, different clinicians such as internists, urologists, oncologists and radiologists are often involved in the care of patients with ureteral obstruction and may have differing opinions concerning the best management strategy. The purpose of this manuscript was to review available literature that compares percutaneous nephrostomy placement vs ureteral stenting in the management of ureteral obstruction from both benign and malignant etiologies.