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Flexible Ureteroscope

Slender (7.5–8.5 Fr) actively deflectable endoscope with 270–316° two-way tip deflection — provides retrograde access to the entire upper urinary tract from distal ureter through renal pelvis into individual calyces. The dominant instrument for upper-tract urothelial carcinoma (UTUC) endoscopic management and intrarenal stone work; for the reconstructive surgeon, the operative tool for the proximal-ureteral and intrarenal portions of stricture workup and iatrogenic-injury management that the semi-rigid ureteroscope cannot reach.[1][2]

Design​

ComponentDetail
OpticsDigital chip-on-tip (CMOS) in modern scopes (superior to legacy fiberoptic); wider FoV, better color, higher resolution[3][4]
Outer diameter7.5–8.5 Fr
Active deflection270–316° in both directions — reaches lower-pole calyces
Working channel3.6 Fr — laser fiber, basket, biopsy forceps, guidewire
Trade-offInstrument insertion reduces deflection and irrigation flow — a central operative constraint
LightExternal xenon / LED via fiber-optic cable

Single-use vs reusable​

Single-use scopes launched widely in 2016 (Boston Scientific LithoVue). Belkovsky 2024 meta (12 studies) — no differences in stone-free rate, OR time, or complications.[5] Reusable scopes may retain a marginal edge in image quality and maneuverability.[6] Rege 2026 head-to-head of 9 single-use platforms rated Storz Flex-XC1, Boston Scientific LithoVue Elite, Cook Ascend as top-tier.[7]

Ureteral access sheath (UAS)​

Hydrophilic 10/12 – 14/16 Fr sheath placed retrograde over a guidewire; serves as conduit for repeated scope passage. Improves irrigation flow / reduces intrarenal pressure / facilitates fragment extraction, at the cost of 1.5–6.8% ureteric injury rate.[8][9] Newer FANS (Flexible and Navigable Suction) UAS allows active aspiration of dust and active pressure control.[10][11]

Reconstructive-Urology and Functional-Urology Uses​

The flexible ureteroscope is the operative tool when work must extend past the UPJ into the renal pelvis or calyces — work the semi-rigid scope cannot do.

Upper-tract urothelial carcinoma (UTUC) endoscopic management​

  • Diagnostic ureteroscopy + biopsy for hematuria / suspicious filling defect / positive urinary cytology — defines tumor location, grade, focality, and feasibility of kidney-sparing endoscopic ablation.
  • Endoscopic laser ablation (Ho:YAG or thulium) for low-grade, unifocal, < 2 cm tumor in patients suitable for kidney preservation — AUA/SUO 2023 UTUC guideline criteria; combined with intracavitary chemotherapy (mitomycin, Jelmyto) or BCG for CIS.[12][13][14]
  • Surveillance — repeat fURS at defined intervals after kidney-sparing management given high recurrence.[12][15]

Proximal-ureteral and intrarenal stricture work​

  • Diagnostic mapping of stricture length / location through the proximal ureter and UPJ.
  • Endoscopic laser incision + balloon dilation + stent for selected short / radiation-induced strictures; durability lower than reconstructive repair, but a valid option in the medically unfit or radiation-bed patient.

Iatrogenic ureteral injury after pelvic surgery​

  • Retrograde access for guidewire passage and stent placement through the renal pelvis when the injury extends proximally beyond the semi-rigid scope's reach.
  • Diagnostic mapping to define the level / severity of injury before deciding on endoscopic vs open reconstructive management.

Post-reconstruction surveillance​

  • After pyeloplasty, ureteroureterostomy, ureteral reimplantation, ileal-ureter reconstruction, fURS can evaluate the anastomosis for recurrence or stenosis.

Stone management (out-of-scope as primary topic; covered for completeness)​

  • The dominant indication globally. Treatment selection (fURS vs SWL vs PCNL) per EAU 2025 / AUA: lower-pole 10–20 mm and SWL-resistant stones favor fURS; > 20 mm favors PCNL with staged fURS as alternative.[16]

Laser Lithotripsy Strategies​

The intracorporeal lithotripsy strategies used with fURS apply equally to laser ablation of small UTUC lesions:

StrategySettingsMechanism
DustingLow energy / high frequency (0.2–0.5 J × 40–80 Hz)Surface ablation to ≤ 1 mm dust; relies on spontaneous passage
Fragmentation + extractionHigh energy / low frequency (0.8–1.2 J × 5–10 Hz)Larger fragments retrieved by basket
PopcorningNon-contact in confined calyxTurbulence propels fragments back into beam

Gauhar 2025 multicenter prospective (n = 704, suction sheath) — dusting outperformed popcorning at 30-day stone-free (69.4% vs 53.9%, p < 0.05); TFL outperformed Ho:YAG as the strongest predictor of complete clearance regardless of strategy.[10] See also Cabo 2025 and Matlaga 2018 for the dusting-vs-fragmentation framework.[11][17]

Semi-Rigid vs Flexible Ureteroscope​

FeatureSemi-rigidFlexible
Tip4.5–8 Fr, passive flex only7.5–8.5 Fr, 270–316° active deflection
Renal-pelvis / calyceal accessNot possibleFull intrarenal access
Working channel1.8–5.5 Fr (straight, accepts rigid probes)3.6 Fr
Rigid lithotripsy probesYes (offset-lens)No
Distal-ureter stone SFR94.2% (CROES)Similar
Proximal-ureter stone SFR77% (standard) / 81.9% (ultrathin)87%
Durability / costMore durable, lowerFragile; single-use commonly used
Typical roleFirst entry, distal / mid ureterProximal ureter, pelvis, calyces, UTUC ablation

Typical workflow: semi-rigid first to establish access and treat distal pathology, then flexible through the now-dilated ureter for proximal / intrarenal work.

Outcomes​

SeriesnSettingStone-free / outcome
CROES URS Global[18]11,885Global registrySFR 85.6%, complication 3.5% (Clavien I–II)
Skolarikos 2015 CROES solitary[19]SubgroupSolitary renal90% (< 20 mm); falls > 20 mm
Giusti 2016 single-center[2]316Mean 16.5 mmPrimary SFR 79.1%, 91.5% after staged; OR ~ 73 min
Huang 2020[20]Renal ≥ 2 cmSingle-institutionStaged ~ 83–90% after 1.4 procedures; ~ 58% if > 4 cm
Fankhauser 2018 propensity-matched fURS vs SWL[21]—Untreated renal84% (fURS) vs 71% (SWL) SFR with fewer reinterventions
FLEXOR registry[22]6,669RIRS practice patternsOverall complications 8.0%; UAS-related ureteric injury 1.8%; sepsis-ICU 1.3%

Safety Profile​

  • Postoperative fever — most common complication (~ 1.8–9.6%).[22]
  • Sepsis / ICU admission — ~ 1.3%.[22]
  • Ureteric injury from UAS — 1.5–6.8% range (1.8% in FLEXOR).[8][9][22]
  • Ureteral perforation — uncommon; FANS suction sheaths reduce intrarenal pressure and may reduce sepsis.[10]
  • Ureteral stricture — late event; risk factors include perforation, prolonged operative time, and UAS use; PULS grade 3 transmural injury carries up to 13.3% stricture rate (see semi-rigid ureteroscope page for the Sunaryo / Cumpanas data).

Practical Pearls​

  • Pre-stenting for ≥ 1 week facilitates UAS passage and subsequent fURS — particularly valuable in the previously instrumented or radiation-bed ureter.
  • Smallest-effective UAS to minimize ischemic injury; consider FANS-suction sheaths in stone cases for intrarenal-pressure control.
  • Sequential approach — semi-rigid first for distal pathology and to dilate the ureter, then flexible for proximal / intrarenal work.
  • TFL when available — the strongest single predictor of complete stone clearance in the Gauhar 2025 dataset.[10]
  • For UTUC — biopsy first, ablate at the same setting only if the lesion clearly meets kidney-sparing criteria; otherwise stage to allow grade review before definitive management.[13]

Limitations​

  • Cost — reusable scopes incur substantial repair cost; single-use scopes have higher per-case cost.
  • Working-channel trade-off — every instrument inserted reduces deflection and irrigation; choose the smallest adequate fiber / basket.
  • Stone size ceiling — > 20–40 mm increasingly favors PCNL even with FANS-suction adjuncts.
  • Not for the very-tight or impacted ureter without pre-stenting or a smaller-caliber semi-rigid first pass.

See also: Semi-Rigid Ureteroscope, Rigid Cystoscope, Flexible Cystoscope, Guidewires, Open-Ended Ureteral Catheters, Double-J Stent, Nephrostomy Tube.

References​

1. Doizi S, Traxer O. "Flexible ureteroscopy: technique, tips and tricks." Urolithiasis. 2018;46(1):47–58. doi:10.1007/s00240-017-1030-x

2. Giusti G, Proietti S, Villa L, et al. "Current standard technique for modern flexible ureteroscopy: tips and tricks." Eur Urol. 2016;70(1):188–94. doi:10.1016/j.eururo.2016.03.035

3. Dale J, Kaplan AG, Radvak D, et al. "Evaluation of a novel single-use flexible ureteroscope." J Endourol. 2021;35(6):903–7. doi:10.1089/end.2016.0237

4. Vaccaro C, Lorusso V, Palmisano F, et al. "Single-use flexible ureteroscopes: how difficult is it today to stay up to date? A pictorial review of instruments available in Europe in 2023." J Clin Med. 2023;12(24):7648. doi:10.3390/jcm12247648

5. Belkovsky M, Passerotti CC, Maia RS, et al. "Comparing outcomes of single-use vs reusable ureteroscopes: a systematic review and meta-analysis." Urolithiasis. 2024;52(1):37. doi:10.1007/s00240-024-01537-8

6. Bragaru M, Multescu R, Geavlete P, Popescu R, Geavlete B. "Comparison of flexible ureteroscope performance between reusable and single-use models." J Clin Med. 2023;12(3):1093. doi:10.3390/jcm12031093

7. Rege R, Hassig S, Patel S, et al. "A comparison of real-world utility and video quality in commercially available single-use ureteroscopes." J Endourol. 2026;40(1):9–16. doi:10.1177/08927790251390908

8. Kaplan AG, Lipkin ME, Scales CD, Preminger GM. "Use of ureteral access sheaths in ureteroscopy." Nat Rev Urol. 2016;13(3):135–40. doi:10.1038/nrurol.2015.271

9. De Coninck V, Keller EX, Rodríguez-Monsalve M, et al. "Systematic review of ureteral access sheaths: facts and myths." BJU Int. 2018;122(6):959–69. doi:10.1111/bju.14389

10. Gauhar V, Giulioni C, Falsetti F, et al. "Lasing strategy and its influence on 30-day operative outcomes in flexible ureteroscopy with FANS: inferences from a real-world prospective multicenter study by EAU-Endourology and AUSET." World J Urol. 2025;43(1):633. doi:10.1007/s00345-025-06012-6

11. Cabo J, Ballantyne C, Edmonds V, Stern KL. "Laser lithotripsy strategies: fragmenting, popcorning, dusting, and how intrarenal pressure should be considered." Urol Clin North Am. 2025;52(3):375–89. doi:10.1016/j.ucl.2025.04.004

12. National Comprehensive Cancer Network. "Bladder Cancer (Upper Tract Urothelial Carcinoma sections)." Updated 2026.

13. Coleman JA, Clark PE, Bixler BR, et al. "Diagnosis and management of non-metastatic upper tract urothelial carcinoma: AUA/SUO guideline." J Urol. 2023;209(6):1071–81. doi:10.1097/JU.0000000000003480

14. Inamoto T, Watanabe S, Tsuchiya Y, et al. "Current kidney-preserving strategies for upper tract urothelial carcinoma." Int J Urol. 2025. doi:10.1111/iju.70243

15. Sydén F, Baard J, Bultitude M, et al. "Consultation on UTUC II Stockholm 2022: diagnostics, prognostication, and follow-up — where are we today?" World J Urol. 2023;41(12):3395–403. doi:10.1007/s00345-023-04530-9

16. Skolarikos A, Geraghty R, Somani B, et al. "European Association of Urology guidelines on the diagnosis and treatment of urolithiasis." Eur Urol. 2025;88(1):64–75. doi:10.1016/j.eururo.2025.03.011

17. Matlaga BR, Chew B, Eisner B, et al. "Ureteroscopic laser lithotripsy: a review of dusting vs fragmentation with extraction." J Endourol. 2018;32(1):1–6. doi:10.1089/end.2017.0641

18. de la Rosette J, Denstedt J, Geavlete P, et al. "The Clinical Research Office of the Endourological Society Ureteroscopy Global Study: indications, complications, and outcomes in 11,885 patients." J Endourol. 2014;28(2):131–9. doi:10.1089/end.2013.0436

19. Skolarikos A, Gross AJ, Krebs A, et al. "Outcomes of flexible ureterorenoscopy for solitary renal stones in the CROES URS Global Study." J Urol. 2015;194(1):137–43. doi:10.1016/j.juro.2015.01.112

20. Huang JS, Xie J, Huang XJ, et al. "Flexible ureteroscopy and laser lithotripsy for renal stones 2 cm or greater: a single institutional experience." Medicine. 2020;99(43):e22704. doi:10.1097/MD.0000000000022704

21. Fankhauser CD, Hermanns T, Lieger L, et al. "Extracorporeal shock wave lithotripsy versus flexible ureterorenoscopy in the treatment of untreated renal calculi." Clin Kidney J. 2018;11(3):364–9. doi:10.1093/ckj/sfx151

22. Gauhar V, Chew BH, Traxer O, et al. "Indications, preferences, global practice patterns and outcomes in retrograde intrarenal surgery (RIRS) for renal stones in adults: results from a multicenter database of 6669 patients of the Global FLEXible Ureteroscopy Outcomes Registry (FLEXOR)." World J Urol. 2023;41(2):567–74. doi:10.1007/s00345-022-04257-z