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Metal & Long-Term Ureteral Stents

Metallic and long-term ureteral stents are used for chronic ureteral obstruction (CUO) from malignant or benign causes. Polymer double-J stents usually need exchange every 3 to 6 months because of encrustation and loss of patency, and metallic devices aim to reduce the number of drainage procedures in selected patients. The permitted indication, insertion method and maximum dwell time belong to the specific device and local labeling.[1][2][13]

Choosing Long-Term Drainage​

Consider the cause and length of obstruction, renal function, bladder drainage, prior radiation or reconstruction, infection and stone burden, prognosis, anesthetic burden and the patient's goals. Compare a metallic stent with polymer stenting, nephrostomy and definitive repair. In malignant obstruction, the value of drainage depends on symptoms, treatment plans and expected benefit. An exchange-saving device is useful only if it continues to drain.[1][2][3] The 2026 CIRSE standards of practice recommend metal stents, when economically feasible, for palliative management of malignant ureteric obstruction; they list active ipsilateral upper-tract stone disease as a relative contraindication to semi-permanent metal stents, and many practitioners wait at least 7 days after nephrostomy for an infected obstructed system before placing one.[38]

Indications reported in the series below:

  • Malignant extrinsic obstruction in which polymer stents fail or need frequent exchange.
  • Benign CUO, including retroperitoneal fibrosis, radiation strictures, postsurgical strictures and ureteropelvic junction obstruction in patients who are not reconstruction candidates.
  • Recurrent obstruction despite polymer exchanges.
  • Patient preference to reduce the number of procedures.[12][13][14]

Situations in which failure or harm has been reported:

  • Urolithiasis. Benson and colleagues concluded that metal stents are effective in the absence of urolithiasis.[12]
  • Bulky pelvic or intravesical disease. Three of 17 Resonance stents failed from the outset in patients with bulky pelvic malignancy and high intravesical pressure.[16]
  • Prostate cancer invading the bladder. In a 25-patient malignant-obstruction cohort, this subgroup had higher Resonance failure risk (HR 6.50, 95% CI 1.45–29.20, p = 0.015). Symptomatic subcapsular hematomas occurred in 3 patients.[17]
  • Prior pelvic radiation. Covered-stent patency was lower after radiation (see Allium below).[24]
  • Long dwell of a covered Uventa stent. Placement of 24 months or more was associated with major complications on univariate analysis (OR 20.4).[5]

Published cost estimates depend on local prices, anesthesia and exchange schedules. In a retrospective Singapore series of 247 stents in 63 patients (45 metallic), mean dwell was 228.6 versus 146.1 days (p < 0.001); the metallic and polymer groups had 1.4 versus 6.3 stents placed per patient during the 4-year study, and cost per dwell day did not differ (SGD 7.82 vs 8.23, p = 0.888).[3] In 13 patients with benign obstruction, the calculated 12-month cost was $11,183 with a metallic stent and $23,999 with polymer stents.[14] These retrospective comparisons support the possibility of fewer procedures.

Device Families​

DeviceDesign and practical distinctionEvidence or labeling boundary
ResonanceFull-length coiled metal double-pigtail stent; delivered through its dedicated sheathCurrent Cook IFU: temporary drainage of extrinsic ureteral obstruction in adults, with a 12-month maximum indwell; earlier intervention may be needed.[1]
Memokath-051Segmental thermo-expandable nickel-titanium spiralNICE recommends it as an option for selected adults, with regular position monitoring and prospective outcome collection. The applicable IFU gives deployment and removal temperatures and dwell limits.[2]
Allium URSSegmental self-expanding nitinol stent with a proprietary polymer coatingCurrent manufacturer description lists 24–30 Fr expanded diameters and a 10 Fr delivery system. It states that a curative effect is not CE-approved; verify the local device indication and IFU.[4]
UventaDouble-layered PTFE membrane-covered self-expanding segmental metallic stentPublished long-term series include serious fistulas, perforation and obstruction. Available sizes, approved use and surveillance requirements need product-specific confirmation.[5]
Detour / extra-anatomic nephrovesical bypassA subcutaneous kidney-to-bladder bypass rather than a stent passing through the ureterA salvage option in selected patients when conventional drainage or reconstruction is unsuitable; infection, leakage, dislodgement and revision remain risks.[6]

Resonance: Label and Handling​

The alloy is nickel-cobalt-chromium-molybdenum, not a self-expanding nitinol mesh. The coiled stent has no central lumen; urine drains through and around the coils.[7] In an animal experiment, flow continued around a tightly tied constricting suture.[7]

The closed-ended stent is inserted through the supplied delivery sheath after removal of the initial catheter and wire, according to the IFU. An ordinary over-the-wire polymer-stent insertion sequence does not apply to the metal coil. Avoid excessive force, bending or stretching, and check final position and function.[1] Technical success was 100% in prospective and retrospective series, with antegrade and retrograde insertion both used.[15][8]

The IFU lists no known contraindications but warns about possible nickel-allergy reactions. It calls for regular follow-up and closer monitoring in patients prone to calcium encrustation. Twelve months is the maximum permitted indwell. MRI is conditional, with scanner, gradient, SAR and scan-time limits specified in the IFU.[1]

Reported outcomes.

  • Khoo and colleagues reported median actual functional stent follow-up of 11.7 months and failure in 11 of 58 insertion episodes (19%), with no failure for benign indications.[8]
  • In malignant extrinsic obstruction, 12 of 37 stents failed in one series, and patency was 86% at 6 months and 60% at 1 year in another (52 patients, 66 ureters).[17][18]
  • In patients whose polymer stents had failed, Resonance stents lasted a mean of 4 months longer than the polymer stents they replaced (50 stents, 42 patients, p < 0.0001).[19]
  • A prospective series of 50 patients reported patency of 100% in malignant and 44% in benign obstruction at mean 8.5 months, encrustation in 12 of 54 stents, and demanding exchange in 9 cases.[15]
  • A systematic review of metallic stents in malignant obstruction found the lowest migration rate with Resonance (1%).[20]

Reports of failure with bulky bladder disease, cancer progression or complex benign strictures should inform selection and follow-up. They are not manufacturer contraindications.[1][8]

Memokath: Current NICE Position​

NICE's 2022 recommendations, now numbered HTG651, support Memokath-051 as an option for adults with malignant obstruction and anticipated medium- or long-term survival after adjunctive therapy; benign obstruction when reconstruction is unsuitable or declined; or any obstruction when a double-J stent is unsuitable or declined, or repeat procedures are particularly high risk. NICE also requests prospective data collection and regular monitoring for migration.[2]

The device is a segmental nickel-titanium spiral that is placed in its narrow form and expanded with warm irrigation to anchor above the stricture; cold irrigation collapses it for removal. Temperatures and sizes follow the IFU.

Reported outcomes.

  • In a three-device comparison, median actual functional stent follow-up was 5.5 months and 31 of 48 insertion episodes (64.6%) failed.[8]
  • An independent review of 100 patients with 162 stents found a 72% mean 5-year stent complication rate: migration 46%, blockage 34%, nonfunctioning kidney 8% and urosepsis needing intravenous antibiotics 8%. Median time to first complication was 12.5 months.[22]
  • In a 21-patient series (11 ureteric and 10 urethral stents), the 11 ureteric stents functioned for a mean of 16.1 months; the three transplant-ureter stents functioned for a mean of 24.3 months.[23]

The evidence remains largely observational, with substantial reintervention in longer follow-up. NICE's 2018 medical-technology evaluation described Memokath-051 as likely to be cost saving in patients not indicated for reconstructive surgery who are expected to need a stent for at least 30 months, on the basis of an economic model.[2][21]

Allium: Drainage Is Distinct From Cure​

A covered segmental stent can maintain a lumen while it is present; durable patency after removal is a different outcome. A 2026 retrospective study of balloon dilation plus Allium reported postremoval success in 64 of 101 patients with complete follow-up at a median of 22.5 months; its composite endpoint required improved hydronephrosis, symptom resolution, stable renal function and no reintervention for at least 12 months after removal. There was no randomized reconstruction comparator. Success was 74.1% for strictures of 2 cm or less and 48.8% for longer strictures; the 92.9% success in the 2 cm or shorter group with 12 to 24 months of stent retention applies to that subgroup only.[9]

The manufacturer's current page distinguishes its drainage indication from an unapproved curative effect. Its linked full IFU must be checked for the actual product before use; a website statement about possible multiyear use does not authorize a universal dwell or removal protocol.[4]

Reported outcomes.

  • A prospective multicenter cohort of 321 patients (366 renal ureter units) with Allium covered metal stents reported 3-year primary patency of 74.0% and secondary patency of 90.4%. After radiation-induced strictures the rates were 54.7% and 77.4%. Complications occurred in 26.0% of units: migration 7.7%, encrustation 8.5%, end-stent restenosis 6.6%, infection 1.9% and fistula 1.4%. Quality of life improved at 12 and 36 months.[24]
  • A separate retrospective cohort of 30 patients with 40 Allium stents reported migration in 11 (27.5%) and encrustation in 8 (20%) at median 29 months. Lower ipsilateral GFR predicted migration.[11]
  • A meta-analysis of 31 studies (1,660 cases) pooled primary success for segmental metal stents at 73% under 1 year, 66% at 1 to 2 years and 39% beyond 2 years, with substantial heterogeneity. Allium reached 81% at 1 to 2 years and 65% beyond 2 years, against 51% and 23% for Uventa and 53% and 23% for Memokath. Covered stents outperformed uncovered stents at 1 to 2 years (75% vs 53%, p = 0.01).[10]

Uventa​

Uventa is a double-layered PTFE membrane-covered self-expandable segmental metallic stent.[5]

  • In 54 patients (71 ureter units) with malignant obstruction, overall success was 81.7% and primary success 64.8% at median 308 days. Complications included persistent flank pain (15.5%), lower urinary tract symptoms (7.0%) and migration (2.8%).[26]
  • A small retrospective comparison included 17 Uventa patients (17 ureters) and 10 Memokath patients (14 ureters) with benign or malignant obstruction; clinical success was defined as improved renal function without obstruction.[21] At mean follow-up of 12.0 and 13.6 months, respectively, clinical success was 82.4% versus 42.9% (p = 0.031).[25]
  • Longer follow-up is less favorable. In 44 patients (50 units) at median 30.9 months, primary success was 30.0% and 14 units (28.0%) had major complications (Clavien-Dindo IIIb or higher): ureteroarterial fistula 6.0%, ureteroenteric fistula 6.0%, ureterovaginal fistula 2.0%, perforation 2.0%, uncontrollable bleeding 2.0% and complete obstruction 10.0%. Associated factors on univariate analysis were female sex, cervical cancer, stricture length of 6 cm or more and placement of 24 months or more.[5]

Reading Outcome Comparisons​

DeviceOutcome reportedMigrationObstruction or encrustationSource
ResonanceMedian actual functional stent follow-up 11.7 months; failure in 11/58 episodes1% (malignant systematic review)Encrustation in 12/54 stents[8][20][15]
Memokath-051Median actual functional stent follow-up 5.5 months; failure in 31/48 episodes72% complication rate at mean 5-year follow-up (100 patients), which included migration (46%)Blockage (34%) within the same complication rate[8][22]
Allium URSMedian actual functional stent follow-up 11.4 months; failure in 11/23 episodes27.5% of 40 stents (single center); 7.7% of 366 units (covered stents, multicenter)Encrustation 20% and 8.5% in the same two cohorts[8][11][24]
UventaPrimary success 64.8% at median 308 days; 30.0% at median 30.9 months2.8%Obstruction 6% (malignant systematic review)[26][5][20]

Percentages in different rows come from different cohorts with different follow-up, indications and units of analysis (patients, ureters or insertion episodes). Khoo 2021 is a retrospective three-device series (76 patients, 129 insertion episodes) with different follow-up per device.[8]

Primary patency, patency after a salvage procedure, freedom from another operation and patency after removal answer different questions. Report the device, unit of analysis, follow-up and definition together.[8][10][11]

Metallic Versus Polymer Stents​

ComparisonFindingSetting
Mean dwell and exchanges228.6 vs 146.1 days (p < 0.001); 1.4 vs 6.3 stents placed per patient during the 4-year studyRetrospective, mixed etiologies, 247 stents[3]
Functional durationMean 4 months longer than the preceding polymer stent (p < 0.0001)Malignant obstruction, same patients, 50 stents[19]
Yearly cost$11,183 vs $23,99913 patients, benign obstruction, calculated 12-month cost[14]
Cumulative patency at 12 months70% (covered metallic) vs 26% (double-J); overall primary patency p = 0.034Advanced gastric cancer, 61 patients (84 ureters), retrospective[30]
ComplicationsMore frequent with the covered metallic stent (48.1% vs 16.7%, p = 0.004), mainly minor hematuria or hematomaSame gastric cancer series[30]
Complications and quality of lifeLower total complications and higher quality-of-life scores at 6 and 12 months with metallic stents (p < 0.05)Malignant obstruction, 76 patients[31]
Patency at 6 months (randomized)Occlusion risk 5.6 times higher with double-J than with a silicone-covered metallic mesh stent (95% CI 1.59–19.90); similar adverse events and discomfort; better global quality of life at 3 and 6 months with the metallic stentMalignant obstruction, single-center open-label RCT, 65 patients (76 ureters)[39]
Stent failure (pooled)RR 0.68 (95% CI 0.44–1.03) with metallic stents, not significant; stent symptoms and complications comparableChronic malignant obstruction, meta-analysis of 6 retrospective cohorts, 511 patients[40]

The two malignant-obstruction series disagree on complication frequency, which likely reflects different stent types, definitions and populations.

Follow-Up and Failure​

Before discharge, record the device, side, size, placement date, indication, planned review and exchange or removal deadline, plus the responsible service. Monitor symptoms, renal function and upper-tract drainage as appropriate. Encrustation, tissue reaction, migration, infection and progression of the underlying obstruction can require intervention before the label's maximum duration.[1][2]

Fever with obstruction, new severe flank pain, deteriorating renal function or substantial hematuria requires assessment. Recurrent or brisk hematuria in a patient with chronic ureteral instrumentation, pelvic radiation or vascular surgery warrants consideration of a vascular-urinary fistula rather than automatic attribution to stent irritation. See also Ureterocolonic Fistula.[5]

Extra-Anatomic Bypass (Detour and Subcutaneous Nephrovesical Stents)​

The Detour stent is an expanded-PTFE and silicone tube placed percutaneously in the kidney, tunneled subcutaneously and sutured into the bladder. It has been described as a salvage option for complete obstruction when conventional stenting has failed, open surgery has failed or is not feasible, and long-term nephrostomy is undesirable.[27][13]

  • In 13 patients receiving 20 stents (median follow-up 12 months), four patients required revision for leakage, two had recurrent UTI, and one died after dislodgement with intra-abdominal sepsis. All stents continued to drain after revision or treatment. Seven patients died of progressive malignancy with a functioning stent.[6]
  • Earlier series described a subcutaneous stent made of two double-J stents joined by a connector (8 patients, 10 stents, 6 weeks to 18 months) and, in 24 patients with pelvic metastases (30 stents, mean follow-up 10.6 months), a reduction in serum creatinine from 256 to 124 μmol/L and an increase in quality-of-life score from 3.4 to 7.6 (p < 0.001).[28][29]

Emerging Technologies​

  • Biodegradable stents. A polyurethane and magnesium-alloy stent degraded completely within 4 weeks in pigs, a biodegradable mesh stent degraded over 3 to 5 months in animals with less infection and encrustation than a double-J stent, and a third-generation biodegradable stent (Uriprene) degraded within 4 weeks in 9 of 10 pigs. These are animal studies.[33][32][37]
  • Drug-eluting and surface-modified stents. Reviews describe antimicrobial, antispasmodic, anti-encrustation and antitumor drug delivery from biodegradable or coated stents.[34][35][36]
  • The stated aim of biodegradable designs is to avoid the forgotten-stent problem.[37]

See also: Double-J Stent, Nephrostomy Tube, Nephroureteral Catheter.

References​

1. Cook Medical. Resonance Metallic Ureteral Stent Set. Current product-linked instructions for use, IFU0020-18; English pp. 3–5. Instructions. Accessed September 12, 2026.

2. National Institute for Health and Care Excellence. Memokath-051 ureter stent for ureteric obstruction. HTG651, published December 7, 2022; guidance number migrated in 2025 without a change to recommendations. Current guidance.

3. Law YXT, Zhou A, Consigliere DT, Goh BYS, Tiong HY. Use of Metallic Ureteric Stents for Chronic Ureteric Obstruction and Its Association With Value-Based Care. Singapore Medical Journal. 2025;66(1):28-32. doi:10.4103/singaporemedj.SMJ-2021-418

4. Allium Medical. Ureteric stents: current product description and regulatory notice. Manufacturer page. Accessed September 12, 2026.

5. Kim M, Hong B, Park HK. Long-Term Outcomes of Double-Layered Polytetrafluoroethylene Membrane-Covered Self-Expandable Segmental Metallic Stents (Uventa) in Patients With Chronic Ureteral Obstructions: Is It Really Safe? Journal of Endourology. 2016;30(12):1339-1346. doi:10.1089/end.2016.0462

6. Chong JJY, Kum F, Hadjipavlou M, et al. Extra-Anatomic Stents in Ureteric Obstruction: Our Experience. Journal of Endourology. 2019;33(3):242-247. doi:10.1089/end.2018.0610

7. Blaschko SD, Deane LA, Krebs A, et al. In-Vivo Evaluation of Flow Characteristics of Novel Metal Ureteral Stent. Journal of Endourology. 2007;21(7):780-783. doi:10.1089/end.2006.0315

8. Khoo CC, Ho C, Palaniappan V, et al. Single-Center Experience With Three Metallic Ureteral Stents (Allium URS, Memokath-051, and Resonance) for Chronic Ureteral Obstruction. Journal of Endourology. 2021;35(12):1829-1837. doi:10.1089/end.2021.0208

9. Tian C, Wang Y, Bian X, et al. Therapeutic Efficacy of Allium Stent Combined With Balloon Dilation as a Curative Modality for Benign Ureteral Strictures. International Journal of Surgery. 2026. doi:10.1097/JS9.0000000000003899

10. Bian X, Hu H, Tian C, et al. Comparison of Different Segmental Metal Ureteral Stents as Maintenance Therapy Across Different Years in Ureteral Stricture Management: A Systematic Review and Meta-Analysis. International Journal of Surgery. 2025. doi:10.1097/JS9.0000000000002384

11. Su B, Hu W, Xiao B, et al. Long-Term Outcomes of Allium Ureteral Stent as a Treatment for Ureteral Obstruction. Scientific Reports. 2024;14(1):21958. doi:10.1038/s41598-024-73125-0

12. Benson AD, Taylor ER, Schwartz BF. Metal Ureteral Stent for Benign and Malignant Ureteral Obstruction. The Journal of Urology. 2011;185(6):2217-2222. doi:10.1016/j.juro.2011.02.008

13. Corrales M, Doizi S, Barghouthy Y, Kamkoum H, Somani B, Traxer O. A Systematic Review of Long-Duration Stents for Ureteral Stricture: Which One to Choose? World Journal of Urology. 2021;39(9):3197-3205. doi:10.1007/s00345-020-03544-x

14. López-Huertas HL, Polcari AJ, Acosta-Miranda A, Turk TM. Metallic Ureteral Stents: A Cost-Effective Method of Managing Benign Upper Tract Obstruction. Journal of Endourology. 2010;24(3):483-485. doi:10.1089/end.2009.0192

15. Liatsikos E, Kallidonis P, Kyriazis I, et al. Ureteral Obstruction: Is the Full Metallic Double-Pigtail Stent the Way to Go? European Urology. 2010;57(3):480-486. doi:10.1016/j.eururo.2009.02.004

16. Wah TM, Irving HC, Cartledge J. Initial Experience With the Resonance Metallic Stent for Antegrade Ureteric Stenting. Cardiovascular and Interventional Radiology. 2007;30(4):705-710. doi:10.1007/s00270-007-9043-4

17. Goldsmith ZG, Wang AJ, Bañez LL, et al. Outcomes of Metallic Stents for Malignant Ureteral Obstruction. The Journal of Urology. 2012;188(3):851-855. doi:10.1016/j.juro.2012.04.113

18. Asakawa J, Iguchi T, Tamada S, et al. Outcomes of Indwelling Metallic Stents for Malignant Extrinsic Ureteral Obstruction. International Journal of Urology. 2018;25(3):258-262. doi:10.1111/iju.13500

19. Chow PM, Chiang IN, Chen CY, et al. Malignant Ureteral Obstruction: Functional Duration of Metallic Versus Polymeric Ureteral Stents. PLoS One. 2015;10(8):e0135566. doi:10.1371/journal.pone.0135566

20. Khoo CC, Abboudi H, Cartwright R, El-Husseiny T, Dasgupta R. Metallic Ureteric Stents in Malignant Ureteric Obstruction: A Systematic Review. Urology. 2018;118:12-20. doi:10.1016/j.urology.2018.01.019

21. Eaton Turner E, Jenks M, McCool R, et al. The Memokath-051 Stent for the Treatment of Ureteric Obstruction: A NICE Medical Technology Guidance. Applied Health Economics and Health Policy. 2018;16(4):445-464. doi:10.1007/s40258-018-0389-3

22. Forster LR, Watson L, Breeze CE, et al. The Fate of Ureteral Memokath Stent(s) in a High-Volume Referral Center: An Independent Long-Term Outcomes Review. Journal of Endourology. 2021;35(2):180-186. doi:10.1089/end.2020.0542

23. Buksh O, Jar A, Khogeer A, et al. Thermoexpandable Memokath Stent: Usage and Efficacy in Ureteral and Urethral Strictures in Saudi Arabia. Urology Annals. 2024;16(1):98-103. doi:10.4103/ua.ua_160_22

24. Wang M, Zhu R, Lai S, et al. Covered Metal Ureteral Stents in the Maintenance Treatment of Refractory Ureteral Stricture: A Prospective, Multi-Center, Large-Scale Cohort Study With 3-Year Outcomes. Journal of Endourology. 2025. doi:10.1177/08927790251378453

25. Kim KS, Choi S, Choi YS, et al. Comparison of Efficacy and Safety Between a Segmental Thermo-Expandable Metal Alloy Spiral Stent (Memokath 051) and a Self-Expandable Covered Metallic Stent (Uventa) in the Management of Ureteral Obstructions. Journal of Laparoendoscopic & Advanced Surgical Techniques. 2014;24(8):550-555. doi:10.1089/lap.2014.0056

26. Chung KJ, Park BH, Park B, et al. Efficacy and Safety of a Novel, Double-Layered, Coated, Self-Expandable Metallic Mesh Stent (Uventa) in Malignant Ureteral Obstructions. Journal of Endourology. 2013;27(7):930-935. doi:10.1089/end.2013.0087

27. Lloyd SN, Tirukonda P, Biyani CS, Wah TM, Irving HC. The Detour Extra-Anatomic Stent: A Permanent Solution for Benign and Malignant Ureteric Obstruction? European Urology. 2007;52(1):193-198. doi:10.1016/j.eururo.2006.11.008

28. Nissenkorn I, Gdor Y. Nephrovesical Subcutaneous Stent: An Alternative to Permanent Nephrostomy. The Journal of Urology. 2000;163(2):528-530. doi:10.1016/s0022-5347(05)67917-7

29. Wang Y, Wang G, Hou P, et al. Subcutaneous Nephrovesical Bypass: Treatment for Ureteral Obstruction in Advanced Metastatic Disease. Oncology Letters. 2015;9(1):387-390. doi:10.3892/ol.2014.2679

30. Kim ET, Yang WJ, Shin JH, et al. Comparison of a Covered Metallic Ureteral Stent and a Double-J Stent for Malignant Ureteral Obstruction in Advanced Gastric Cancer. Clinical Radiology. 2021;76(7):519-525. doi:10.1016/j.crad.2021.02.016

31. Chen Y, Liu CY, Zhang ZH, et al. Malignant Ureteral Obstruction: Experience and Comparative Analysis of Metallic Versus Ordinary Polymer Ureteral Stents. World Journal of Surgical Oncology. 2019;17(1):74. doi:10.1186/s12957-019-1608-6

32. Wang Y, Ren X, Ji C, et al. A Modified Biodegradable Mesh Ureteral Stent for Treating Ureteral Stricture Disease. Acta Biomaterialia. 2023;155:347-358. doi:10.1016/j.actbio.2022.11.022

33. Jin L, Yao L, Yuan F, Dai G, Xue B. Evaluation of a Novel Biodegradable Ureteral Stent Produced From Polyurethane and Magnesium Alloys. Journal of Biomedical Materials Research Part B. 2021;109(5):665-672. doi:10.1002/jbm.b.34730

34. Hu K, Hou Z, Huang Y, et al. Recent Development and Future Application of Biodegradable Ureteral Stents. Frontiers in Bioengineering and Biotechnology. 2024;12:1373130. doi:10.3389/fbioe.2024.1373130

35. Shan H, Cao Z, Chi C, et al. Advances in Drug Delivery via Biodegradable Ureteral Stent for the Treatment of Upper Tract Urothelial Carcinoma. Frontiers in Pharmacology. 2020;11:224. doi:10.3389/fphar.2020.00224

36. Xia K, Shen X, Ang X, et al. Surface Modification of Ureteral Stents: Development History, Classification, Function, and Future Developments. Expert Review of Medical Devices. 2023;20(5):401-416. doi:10.1080/17434440.2023.2198702

37. Chew BH, Paterson RF, Clinkscales KW, et al. In Vivo Evaluation of the Third Generation Biodegradable Stent: A Novel Approach to Avoiding the Forgotten Stent Syndrome. The Journal of Urology. 2013;189(2):719-725. doi:10.1016/j.juro.2012.08.202

38. Ryan AG, Irvine I, Bardgett H, et al. "CIRSE Standards of Practice on Nephrostomy and Ureteric Stent Placement and Exchange." Cardiovasc Intervent Radiol. 2026;49(3):464-479. doi:10.1007/s00270-025-04328-9

39. Han DH, Lee CU, Chung JH. "Randomized Controlled Trial to Evaluate the Efficacy and Safety of Silicone-Covered Metallic Mesh Stent Compared to Conventional Polymeric Stent in Malignant Ureteral Obstruction Patients." J Endourol. 2026;40(9):1032-1040. doi:10.1177/08927790261451821

40. Lim QY, Kyaw L, Ong CSH, Law YXT, Tiong HY. "Metallic versus polymeric ureteric stents for chronic malignant ureteric obstruction: a systematic review and meta-analysis." World J Urol. 2026;44(1):604. doi:10.1007/s00345-026-06718-1