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Ureteral Access Sheath (UAS)

A ureteral access sheath provides a temporary conduit for repeated flexible ureteroscope passage. It can improve irrigation outflow and fragment retrieval, but insertion can injure the ureter. Its benefit depends on ureteral anatomy, sheath-to-scope clearance, irrigation, suction and the planned procedure; routine use is not required for every ureteroscopy.[1][2]

Design​

A conventional sheath has two parts: a tapered inner dilator, advanced over a guidewire to dilate the ureter, and an outer sheath that stays in place as the working conduit. A hydrophilic coating eases insertion, radiopaque markers aid fluoroscopic positioning, and the wall must resist kinking while following ureteral curves. Lengths of 13 to 55 cm and diameters from 9.5/11.5 Fr to 16/18 Fr are marketed.[12][14]

A bench comparison of four commercial sheaths found the Navigator HD (11/13 Fr) the most lubricious and rigid, the Cook Flexor sheaths the least traumatic to tissue, and the Re-Trace (10/12 Fr) the longest and most flexible tip (51 mm). Single-wire designs had lower buckling force but needed more force to remove the dilator.[13]

Selection and Placement​

Conventional systems comprise a tapered inner dilator and outer sheath. Inner and outer French sizes are different dimensions: for example, 12/14 Fr describes the working lumen and external profile, not two interchangeable sizes. Guidewire compatibility, coating preparation, length, position and insertion and removal steps are product-specific.[1][2]

Choose a sheath that accepts the scope and permits useful outflow without forcing the ureter to accept a larger device. Larger sheaths may increase outflow but also increase insertion injury in an unstented ureter. No single size is the default for all adults, children, infected stones or reconstructed tracts.[1]

Size (inner/outer Fr)Typical use
9.5/11.5Smallest common profile; small or pediatric ureters
10/12 and 11/13Standard use with thin scopes
12/14The most studied size
14/16Larger stone burden or infectious stones

These assignments are common practice, not a standard; sizes and designs vary by manufacturer.[14][25]

Stop for significant resistance and reassess the wire, anatomy and size. Options include a smaller sheath, sheathless access, or drainage and a staged procedure. Prestenting for at least one week enlarges the ureter and can facilitate access.[28] The EAU 2026 text states that routine stenting before ureteroscopy is not necessary: a meta-analysis found that pre-stenting may improve the stone-free rate for renal but not ureteral stones (LE 2a), and it may increase success in sheath placement without reducing intraoperative complications. Retrospective studies link longer preoperative stent dwell to postoperative infection. If access is not possible, EAU describes a JJ stent followed by ureteroscopy after 7 to 14 days as an alternative.[1] In a randomized comparison of two 12/14 Fr sheaths (95 patients), insertion succeeded in 87.4% and did not differ by sheath; difficult placement and longer insertion time were associated with high-grade injury, so switch to a smaller sheath when resistance is felt.[21]

Intrarenal Pressure​

An outflow channel around the scope can lower pressure, but a sheath does not guarantee a safe intrarenal pressure. Pressure also depends on inflow, working-channel instruments, sheath position, ureteral compliance and suction. In a systematic review, the lowest reported mean pressure during flexible ureteroscopy without a sheath was 47.6 cmH₂O, not 47.6 mmHg; values from different experimental setups should not be merged into a universal bedside table.[1][3]

EAU describes physiologic intrarenal pressure around 0–20 cmH₂O. It links sustained pressures near or above 30 mmHg (about 41 cmH₂O) with pyelovenous backflow and infectious risk, and states that backflow can begin at lower pressures depending on papillary morphology. The text says sheaths improve outflow, lower intrarenal pressure and vision, and potentially shorten operating time, and that suction sheaths lower pressure further. Its practical advice is to pair moderated inflow with a sheath, preferably with controllable suction. These values are physiologic reference points that are not a validated patient-specific safety ceiling. Favor adequate outflow and controlled inflow; maintain attention to infection and irrigation temperature during laser use.[1]

Porcine-model data illustrate the effect of sheath size and position. In one pressure-sensing ureteroscope study in pigs, mean intrarenal pressure was 64 mmHg without a sheath, 51 mmHg with an 11/13 Fr sheath, 39 to 40 mmHg with 12/14 or 13/15 Fr sheaths, 24 mmHg with the sheath tip in the renal pelvis and 61 mmHg with the tip at the ureteropelvic junction.[15] In ex vivo porcine kidneys, a 12/14 Fr conventional sheath with a 2.8 mm scope kept pressure below 35 mmHg up to 200 cc/min of irrigation, and the threshold fell to 110 to 120 cc/min with a 3.2 mm scope. With an 11/13 Fr sheath the threshold was 80 to 90 cc/min (2.8 mm scope) and 30 to 40 cc/min (3.2 mm scope).[16] A 7.5 Fr digital ureteroscope stayed within 120 cc/min without a sheath in another ex vivo model, and pyelotubular backflow became prominent at 40 mmHg.[17]

A flow rate demonstrated in an ex-vivo porcine kidney cannot certify that the same rate is safe in a patient, with a different scope, laser setting or collecting system. Suction settings likewise depend on the device and its validated workflow, and a generic “vent closed” recipe does not apply.[1][3]

Suction and Flexible-Tip Sheaths​

Suction-assisted sheaths can evacuate fragments and improve outflow. Flexible or navigable tips allow access closer to individual calyces. In ex vivo porcine kidneys, a vacuum-assisted sheath with the vent closed kept pressure below 5 mmHg at 200 cc/min irrigation with 11/13 and 12/14 Fr sheaths, whereas a conventional 12/14 Fr sheath reached 30 mmHg or more once irrigation exceeded about 100 cc/min. With the vent open the advantage over a conventional sheath was marginal. A flexible and navigable suction sheath combined with suction irrigation gave the lowest pressure (1.7 cmH₂O) in another porcine model.[18][16][19] The strongest directly checked comparative evidence in patients is a 2024 randomized multicenter trial; the 2025 Arikan study is retrospective.[4][5]

Zhu 2024 trialSuction-tip sheathTraditional sheath
Randomized patients160160
Immediate stone-free endpoint130/160 (81.3%)79/160 (49.4%)
Three-month CT stone-free endpoint140/160 (87.5%)112/160 (70.0%)
Postoperative fever9/160 (5.6%)28/160 (17.5%)

The trial enrolled adults with renal or proximal ureteral stones no larger than 30 mm at eight experienced centers. It excluded abnormal upper tracts, including ileal conduits, and uncontrolled infection. The immediate endpoint combined endoscopic inspection with early plain radiography or ultrasound; the three-month CT endpoint allowed fragments no larger than 2 mm. These are different assessments and do not prove complete absence of fragments at both time points.[4]

The suction group also used a different irrigation delivery protocol. The result therefore evaluates the trial's combined device and irrigation approach. Operating time, hospital stay and secondary interventions did not differ significantly, intrarenal pressure was not directly measured, and three months is insufficient to establish long-term stricture safety. Hematoma and urine extravasation still occurred. These findings should not be generalized automatically to transplant ureters or reconstructed upper tracts.[4]

A 2025 meta-analysis of 10 studies (2,105 patients) reported immediate stone-free rates of 79.1% versus 56.5%, 1-month stone-free rates of 92.0% versus 79.9%, total complications of 7.2% versus 19.0% and fever in 3.3% versus 10.4% with flexible suction sheaths versus traditional sheaths. It combines studies with different designs and protocols, and long-term complications were not compared. Arikan's 207-patient comparison was retrospective, so it should not be labeled a multicenter randomized trial or used to establish a special causal benefit in hydronephrosis.[5][6]

Ureteral Injury: Use the Correct Scale​

The Traxer–Thomas sheath-injury classification and Schoenthaler's Post-Ureteroscopic Lesion Scale (PULS) are separate systems. Do not interchange their grade numbers or call the Traxer classification PULS. Document the actual observed depth, circumferential extent, perforation or extravasation and the scale used.[7][8]

In Traxer and Thomas's prospective 359-patient series, 167 patients (46.5%) had some ureteral-wall injury and 48 (13.3%) had injury involving smooth muscle. Prestenting was associated with a sevenfold lower risk of severe injury, and male sex and older age were also associated with severe injury. These observations identify a real insertion hazard; they do not require routine prestenting or predict an individual's later stricture risk.[7] In 68 patients with 12 to 14 Fr sheaths placed without prestenting, high-grade injury occurred in 26.1% and a narrower proximal ureteral diameter was associated with it (mean 3.29 vs 4.5 mm; OR 2.8), which is why preoperative CT measurement of ureteral diameter has been proposed.[20]

A 2026 force-sensor study included 238 patients and 250 renal units. A 16 Fr outer-diameter sheath was placed in 145 units (58%); two PULS grade-3 injuries occurred, both with forces of at least 8 N. The absence of grade-3 injuries at or below 6 N in this series does not guarantee that no injury occurred, and tactile judgment without a calibrated sensor cannot reproduce an instrumented threshold.[9]

EAU 2026 summarizes the risk as follows: insertion can damage the ureter, the risk is lowest in a pre-stented system, larger sheaths give higher injury grades in patients who were not stented, long-term stricture rates do not differ by sheath size, and larger cohorts show a stricture rate of about 1.8% with fewer postoperative infections. It calls a correctly applied sheath safe and useful for large or multiple stones or long procedures.[1]

Inspect the ureter during withdrawal when feasible and base drainage and follow-up on the actual injury and clinical setting. Difficult or traumatic access, perforation and concerns about drainage warrant reassessment rather than continuing solely because the sheath has passed.[1][7]

Longer-Term Outcomes and Infection​

A prospective follow-up series of 56 patients with high-grade sheath injuries found one stricture at a median 35.8 months. Its uncontrolled design does not prove equivalence to an uninjured ureter. In a retrospective study of 1,332 ureteroscopies, postoperative hydronephrosis at about 8 weeks (12.0%) was not associated with sheath use, but was associated with postoperative stenting, longer operative time and larger stone size.[11] Follow-up completeness and the reason for sheath use limit interpretation.[10][11]

A sheath also does not guarantee infection prevention. Culture-directed management, treatment of infection before elective intervention, appropriate perioperative prophylaxis, controlled pressure and sensible procedural duration remain important. An infected obstructed system needs drainage and infection treatment before definitive stone surgery.[1]

Stone-Free Rate and Infection Outcomes​

  • CROES global study (2,239 flexible ureteroscopies, 67% with a sheath): after inverse-probability weighting, stone-free rate was not significantly different with or without a sheath (0.753 vs 0.504, p = 0.604), and postoperative infectious complications were reduced with a sheath.[22]
  • Meta-analysis of 8 studies (3,099 patients): no difference in stone-free rate (OR 0.83, p = 0.45), but postoperative complications were more frequent with a sheath (OR 1.46).[23]
  • Multicenter retrospective cohort (1,177 patients): similar 3-month stone-free rate after weighting, with a sheath associated with longer operative time and more postoperative stenting.[24]
  • Larger sheath. A single-surgeon retrospective study (257 patients) found 14/16 Fr sheaths treated more than 30% more stone burden per operative minute than 12/14 Fr, with similar stone-free and complication rates. A separate retrospective case-control study (1,139 patients) reported fewer postoperative infectious complications with 14/16 Fr (1.6% vs 6.4%).[25][14]
  • Septic shock. In a single-center series of 451 procedures, ureteroscopy without a sheath was associated with septic shock (OR 14.6, 95% CI 1.08–197.1, from 6 events), with no clear effect on fever or sepsis.[26]
  • Ureteroscope durability. Scope lifetime correlated with the frequency of lower-pole stones, not with the proportion of sheathless cases.[27]

Facilitating Placement​

  • Prestent for at least one week when access is anticipated to be difficult.[7][28]
  • Downsize when resistance is felt or insertion is prolonged.[21]
  • Consider force-controlled insertion where the equipment is available (see the 2026 force-sensor study above).[9]
  • The value of preoperative alpha-blockers is unclear.[28]

Where Sheaths May Become Less Necessary​

Thulium fiber laser (finer dust), smaller single-use digital ureteroscopes and integrated pressure-measuring and aspiration systems may reduce routine sheath use. A sheath still fits large stone burden, infectious stones, planned repeated scope passes and any setting where sustained low pressure is the priority.[28][17]

Reconstructive-Urology Use​

Use ureteroscopy when it answers a specific diagnostic or therapeutic question. A sheath may help when repeated access is necessary (upper-tract urothelial biopsy or ablation, proximal stricture mapping, evaluation of iatrogenic injury), but a reconstructed, irradiated or narrowed ureter requires particular care with caliber and instrumentation, and prestenting is most valuable there because the next operation may be an open repair. Stone-trial results do not establish routine ureteroscopy or sheath placement for surveillance after pyeloplasty, reimplantation or ileal ureter replacement. Choose follow-up and imaging for the repair and clinical question.[1][2][4]

See also: Flexible Ureteroscope, Guidewires, Open-Ended Ureteral Catheters, Double-J Stent.

References​

1. European Association of Urology. EAU Guidelines on Urolithiasis. 2026 (limited update, March 2026). Section 3.4.6, ureteroscopy: access sheaths, intrarenal pressure, stenting before and after URS. Guideline.

2. 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

3. Croghan SM, Skolarikos A, Jack GS, et al. "Upper urinary tract pressures in endourology: a systematic review of range, variables and implications." BJU Int. 2023;131(3):267–79. doi:10.1111/bju.15764

4. Zhu W, Liu S, Cao J, et al. Tip bendable suction ureteral access sheath versus traditional sheath in retrograde intrarenal stone surgery: an international multicentre, randomised, parallel group, superiority study. EClinicalMedicine. 2024;74:102724. doi:10.1016/j.eclinm.2024.102724.

5. Arikan O, Erdogan E, Aydin ME, et al. "A comparative study of flexible navigable vacuum-assisted ureteral access sheath and traditional ureteral access sheath in retrograde intrarenal surgery: evaluating the impact of hydronephrosis on stone-free rate and complications." J Endourol. 2025;39(7):646–51. doi:10.1089/end.2024.0921

6. Xie Y, Gong H, Zheng Q, et al. "Efficacy and safety of flexible and navigable suction access sheaths versus traditional access sheath in flexible ureteroscopic lithotripsy: a systematic review and meta-analysis." World J Urol. 2025;43(1):487. doi:10.1007/s00345-025-05856-2

7. Traxer O, Thomas A. "Prospective evaluation and classification of ureteral wall injuries resulting from insertion of a ureteral access sheath during retrograde intrarenal surgery." J Urol. 2013;189(2):580–4. doi:10.1016/j.juro.2012.08.197

8. Schoenthaler M, Wilhelm K, Kuehhas FE, et al. Postureteroscopic lesion scale: a new management modified organ injury scale—evaluation in 435 ureteroscopic patients. J Endourol. 2012;26(11):1425–1430. doi:10.1089/end.2012.0227.

9. Ali SN, McCormac A, Saadat S, et al. "Ureteral access sheath deployment: understanding the force tolerance of the human ureter and the development of ureteral injury during endoscopic surgery." J Endourol. 2026;40(3):296–302. doi:10.1177/08927790251400350

10. Stern KL, Loftus CJ, Doizi S, Traxer O, Monga M. "A prospective study analyzing the association between high-grade ureteral access sheath injuries and the formation of ureteral strictures." Urology. 2019;128:38–41. doi:10.1016/j.urology.2019.02.032

11. Cooper JL, François N, Sourial MW, et al. "The impact of ureteral access sheath use on the development of abnormal postoperative upper tract imaging after ureteroscopy." J Urol. 2020;204(5):976–81. doi:10.1097/JU.0000000000001147

12. 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

13. De S, Sarkissian C, Torricelli FC, Brown R, Monga M. "New ureteral access sheaths: a double standard." Urology. 2015;85(4):757–63. doi:10.1016/j.urology.2014.07.009

14. Chen Y, Liao B, Feng S, et al. "Comparison of safety and efficacy in preventing postoperative infectious complications of a 14/16 F ureteral access sheath with a 12/14 F ureteral access sheath in flexible ureteroscopic lithotripsy." J Endourol. 2018;32(10):923–7. doi:10.1089/end.2018.0222

15. Chew BH, Shalabi N, Herout R, et al. "Intrarenal pressure measured using a novel flexible ureteroscope with pressure-sensing capabilities: a study of the effects of ureteral access sheath, irrigation, and working channel accessories." J Endourol. 2023;37(11):1200–8. doi:10.1089/end.2022.0841

16. Guan W, Liang J, Wang D, et al. "The effect of irrigation rate on intrarenal pressure in an ex vivo porcine kidney model: preliminary study with different flexible ureteroscopes and ureteral access sheaths." World J Urol. 2023;41(3):865–72. doi:10.1007/s00345-023-04295-1

17. Han Z, Wang B, Liu X, et al. "Intrarenal pressure study using 7.5 French flexible ureteroscope with or without ureteral access sheath in an ex-vivo porcine kidney model." World J Urol. 2023;41(11):3129–34. doi:10.1007/s00345-023-04598-3

18. Wang D, Han Z, Bi Y, et al. "Comparison of intrarenal pressure between conventional and vacuum-assisted ureteral access sheath using an ex vivo porcine kidney model." World J Urol. 2022;40(12):3055–60. doi:10.1007/s00345-022-04149-2

19. Gadzhiev N, Aloyan A, Yuen SKK, et al. "Intrarenal pressure variations during flexible ureteroscopy in a porcine kidney model: impact of ureteral access sheath types and irrigation methods." World J Urol. 2025;43(1):501. doi:10.1007/s00345-025-05857-1

20. Fulla J, Prasanchaimontri P, Rizk A, et al. "Ureteral diameter as predictor of ureteral injury during ureteral access sheath placement." J Urol. 2021;205(1):159–64. doi:10.1097/JU.0000000000001299

21. Loftus CJ, Ganesan V, Traxer O, et al. "Ureteral wall injury with ureteral access sheaths: a randomized prospective trial." J Endourol. 2020;34(9):932–6. doi:10.1089/end.2018.0603

22. Traxer O, Wendt-Nordahl G, Sodha H, et al. "Differences in renal stone treatment and outcomes for patients treated either with or without the support of a ureteral access sheath: the CROES ureteroscopy global study." World J Urol. 2015;33(12):2137–44. doi:10.1007/s00345-015-1582-8

23. Huang J, Zhao Z, AlSmadi JK, et al. "Use of the ureteral access sheath during ureteroscopy: a systematic review and meta-analysis." PLoS One. 2018;13(2):e0193600. doi:10.1371/journal.pone.0193600

24. Bakayoko A, Mardelli C, Dupuis H, et al. "Does the use of a ureteral access sheath improve perioperative outcomes in ureteroscopy? A real-world multi-institutional study." Urolithiasis. 2025;53(1):182. doi:10.1007/s00240-025-01865-3

25. Tracy CR, Ghareeb GM, Paul CJ, Brooks NA. "Increasing the size of ureteral access sheath during retrograde intrarenal surgery improves surgical efficiency without increasing complications." World J Urol. 2018;36(6):971–8. doi:10.1007/s00345-018-2204-z

26. Villa L, Dioni P, Candela L, et al. "Understanding the role of ureteral access sheath in preventing postoperative infectious complications in stone patients treated with ureteroscopy and Ho:YAG laser lithotripsy: results from a tertiary care referral center." J Clin Med. 2023;12(4):1457. doi:10.3390/jcm12041457

27. Özman O, Başataç C, Akgül M, et al. "The effect of ureteral access sheath use / caliber change on outcomes of retrograde intrarenal surgery, short-term kidney functions, radiation exposure, ureteroscope lifetime, and factors predicting insertion failure: a RIRSearch study." J Laparoendosc Adv Surg Tech A. 2024;34(1):33–8. doi:10.1089/lap.2023.0358

28. De Coninck V, Somani B, Sener ET, et al. "Ureteral access sheaths and its use in the future: a comprehensive update based on a literature review." J Clin Med. 2022;11(17):5128. doi:10.3390/jcm11175128