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Evolving Trends Lead to Unmet Needs in Flexible Ureteroscopy

Editorial commentary by: Oliver Wiseman, MA, FRCS (Urol), Consultant Urologist, Cambridge, United Kingdom

With recent advancements in technology, flexible ureteroscopy (URS) has become an increasingly favored option to treat kidney stones.1 In fact, the use of URS is increasing in the U.S., the U.K. and across Europe.1-3 In the U.S., for instance, URS increased from 46.3% of stone procedures in 2007 to 60% in 2017.4 However, recent trends associated with URS have had a mixed effect on the goal to increase stone-free rates while decreasing complications rates. 

Let’s take a closer look at some of these trends:

Variable use of access sheaths

Ureteral access sheaths may provide a variety of potential benefits including: 

  • Improved irrigation flow5,6
  • Better visibility7,8
  • Potential reduced risk of infection8,9
  • Instrument protection7,8
  • Allowing passive egress of fragments5,10
  • Assisting with multiple entries and exits from the kidney10
  • Decreased intrarenal pressure (IRP),5,6 which is important because high IRP may lead to complications such as increased risk of infection,11-14 sepsis11-14 and systemic inflammatory response syndrome (SIRS)12,13

However, the practice of using access sheaths is variable and, from my perspective, may have declined in recent years. A 2021 multivariate logistical regression found access sheaths were used in 37.7% of cases, with a surprising degree of variation in the frequency of UAS use depending upon the practice.8 This may be because, as with many surgical techniques, there are risks associated with the way access sheaths are currently used, including bleeding and ureteric injury.15 Additionally, guidelines from the European Association of Urology and the American Urological Association do not offer clear recommendations for using access sheaths during URS procedures.15

Given the purported benefits that access sheaths provide, it’s surprising that use is not more widespread. Concerns regarding the risks of use may account for this, but there are ways to reduce these risks, including care not to use excessive force during placement. Their use may be safer in pre-stented patients. Additionally, the ratio of the size of the access sheath to the outer scope diameter should be considered. It’s important to provide sufficient space between the outer contours of the ureteroscope and the inner wall of the access sheath, in an effort to improve irrigation flow and potentially reduce IRP.9,16

More powerful lasers have led to higher use of dusting

Dusting of kidney stones is now possible with newer high-power lasers that are used to break kidney stones into tiny fragments or “dust” that can be passed out of the kidney. Although high-power lasers can dust more quickly and efficiently, they can also result in more dust and reduced visibility. A 2018 prospective multi-center non-randomized study found that dusting procedures resulted in shorter mean operative time (67.4 vs 35.9 minutes, p <0.001), but stone-free rate was significantly higher in the basketing group on univariate analysis (74.3% vs. 58.2%, p=.04).17 Additionally, a porcine in vivo model showed high-power lasers may cause temperatures to increase enough to damage tissue unless optimal irrigation flow is provided.18

Changes or improvements in pulse modulation can also create a large amount of tiny stone dust fragments — the “snow globe effect.” In vitro stone displacement experiments showed that this technology resulted in significantly higher stone ablation volume (160% higher) and less stone movement (50 times less retropulsion) than the regular mode.19

According to a worldwide survey, 66% and 73% of U.S./Canada and European endourologists, respectively, reported using the laser dusting technique.20 Stone management strategy during URS may have changed to less or no stone basketing,21 and in doing so has negated some of the previously mentioned benefits of using an access sheath.


URS trends lead to unmet needs

The above trends are juxtaposed to two significant unmet needs in URS: increasing stone-free rates and decreasing complication rates.

The need to increase stone-free rates

The reality is that stone-free rates after ureteroscopy, especially for larger stones, are lower than we would like. When a CT scan is used to assess stone status within three months of URS and laser stone fragmentation, one observational study showed that the stone-free rate, defined as absence of any stone fragments, is only 50%.22 The residual fragments seen may be significant,22,23 and the potential complications are not negligible.24

Trends that may contribute to the problem include:

  • Higher use of laser dusting 
  • Increased URS treatment of large stones

Potential solutions include: 

  • Increase stone basketing — A 2018 prospective multicenter trial concluded that short-term stone-free rate was higher with active basket retrieval of fragments vs. dusting at short-term follow-up in a univariate analysis (74.3% vs. 58.2%, p=.04).17
  • Consideration of the size of stone to be treated by URS, with an understanding that stone-free rates will be much higher the smaller the stone treated — A 2015 prospective data study found that when performing flexible URS, stone-free rate negatively correlated with stone size when adjusted for body mass index.25

The need to decrease complications

Infection is the most common post-op complication in URS26 and can be fatal.27

Trends that may contribute to the problem include:

  • Variable access sheath use 
  • Increased treatment of large stones, longer operative times and higher IRPs

Potential solutions include:

  • Limiting the intrarenal pressure during surgery28,29
  • Ensuring that the urine is sterile pre-operatively27
  • Limiting surgical time as much as possible25,27,28
  • Exercising particular caution in elderly, diabetic patients30, and those who have had a pre-existing stent, especially if it has been indwelling for a long time28,31
  • Increase the use of access sheaths — According to a 2010 study, this may help reduce IRP, improve irrigation and decrease operative time and costs16
  • Considering the size of the access sheath to the outer scope diameter — providing sufficient space between the outer contours of the ureteroscope and the inner wall of the access sheath, which may improve irrigation flow, reduce IRP and decrease operative times and cost9,16

Despite uncertainties, three things are clear

Recent trends in URS create uncertainties as we work to find solutions for these unmet needs. Here are my current recommendations to increase stone-free rates and decrease complications:  

  1. Maintain irrigation fluid flow to enable visualization and help clear dust or fragments, especially when using high-power laser lithotripsy
  2. Keep IRP as low as possible, as higher IRPs may lead to higher complication rates
  3. Be especially wary in high-risk patients: elderly patients, those with a history of urinary infection and pre-operative stents, those with a history of diabetes, those with large stone burdens, and those whose operations are long

Related content


1. Oberlin DT, Flum AS, Bachrach L, et al. Contemporary surgical trends in the management of upper tract calculi. J Urol. 2015 Mar;193(3):880-4.

2. Turney B, Demaire C, Klocker S, et al. Upper Urinary Tract Stones: Evolution of Surgical Management Trends in Germany, France and England over the Past Decade. Paper presented at: 38th World Congress of Endourology; September 23–25, 2021; Hamburg, Germany. Abstract MP04–06.

3. Aboumarzouk OM, Monga M, Kata SG, et al. Flexible ureteroscopy and laser lithotripsy for stones >2 cm: A systematic review and meta-analysis. J Endourol. 2012 Oct;26(1):1257–63.

4. Metzler IS, Holt S, Harper J. Surgical trends in nephrolithiasis: increasing de novo renal access by urologists for percutaneous nephrolithotomy. J Endourol. 2021 Jn;35(6):769–74.

5. Auge BK, Pietrow PK, Lallas CD, et al. Ureteral access sheath provides protection against elevated renal pressures during routine flexible ureteroscopic stone manipulation. J Endourol. 2004 Feb;18(1):33–6.

6. Rehman J, Monga M, Landman J, et al. Characterization of intrapelvic pressure during ureteropyeloscopy with ureteral access sheaths. Urology 2003 Apr;61(4):713–8.

7. Patel N, Monga M. Ureteral access sheaths: a comprehensive comparison of physical and mechanical properties. Int Braz J Urol. 2018 May-Jun;44(3):524–35.

8. Meier K, Hiller S, Dauw C, et al. Understanding ureteral access sheath use within a statewide collaborative and its effect on surgical and clinical outcomes. J Endourol. 2021 Sep;35(9):1340–7.

9. De Coninck V, Keller EX, Rodriguez-Monsalve M, et al. Systematic review of ureteral access sheaths: facts and myths. BJU Int. 2018 Dec;122(6):959–69.

10. Traxer O, et al. Differences in renal stone treatment and outcomes for patients treated either with or without the support of a ureteral access sheath: The Clinical Research Office of the Endourological Society Ureteroscopy Global Study. World J Urol. 2015 Dec;33(12):2137–44.

11. Osther PJS, Pedersen KV, Lildal SK, et al. Pathophysiological aspects of ureterorenoscopic management of upper urinary tract calculi. Curr Opin Urol. 2016 Jan;26(1):63–9. 

12. Tokas T, Herrmann TRW, Skolarikos A, et al. Training and Research in Urological Surgery and Technology (T.R.U.S.T.) Group. Pressure matters: Intrarenal pressures during normal and pathological conditions, and impact of increased values to renal physiology. World J Urol. 2019 Jan;37(1):125–31.

13. Zhong W, Leto G, Wang L, et al. Systemic inflammatory response syndrome after flexible ureteroscopic lithotripsy: A study of risk factors. J Endourol. 2015 Jan;29(1):25–8.

14. Gutierrez-Aceves J, Negrete-Pulido O, Avila-Herrera P. Preoperative Antibiotics and Prevention of Sepsis in Genitourinary Surgery. In Smith AD, Badlani GH, Preminger GM, Kavoussi LR (Eds.), Smith’s Textbook of Endourology. New York, NY: Blackwell Publishing Ltd., 2012:38–52.

15. Wong VK, Aminoltejari K, Almutairi K, et al. Controversies associated with ureteral access sheath placement during ureteroscopy. Investig Clin Urol. 2020 Sep;61(5):455–63.

16. Ng YH, Somani BK, Dennison A, et al. Irrigant flow and intrarenal pressure during flexible ureteroscopy: The effect of different access sheaths, working channel instruments, and hydrostatic pressure. J Endourol. 2010 Dec;24(12):1915–20.

17. Humphreys MR, Shah OD, Monga M, et al. Dusting versus basketing during ureteroscopy- which technique is more efficacious? A prospective multicenter trial from the EDGE research consortium. J Urol. 2018 May;199(5):1272–6.

18. Aldoukhi AH, Hall TL, Ghani KR, et al. Caliceal fluid temperature during high-power holmium laser lithotripsy in an in vivo porcine model. J Endourol. 2018 Aug;32(8):724–9.

19. Elhilali MM, Badaan S, Ibrahim A, et al. Use of the Moses technology to improve holmium laser lithotripsy outcomes: a preclinical study. J Endourol. 2017 Jun;31(6):598–604.

20. Dauw CA, Simeon L, Alruwaily AF, et al. Contemporary practice patterns of flexible ureteroscopy for treating renal stones: results of a worldwide survey. J Endourol. 2015 Nov;29(11):1221–30.

21. Inoue T, Okada S, Hamamoto S, Fujisawa M. Retrograde intrarenal surgery: past, present, and future. Investig Clin Urol. 2021 Mar;62(2):121–35.

22. Macejko A, Okotie OT, Zhao LC, et al. Computed tomography-determined stone-free rates for ureteroscopy of upper-tract stones. J Endourol. 2009 Mar;23(3):379-82.

23. Rippel CA, Nikkel L, Lin YK, et al. Residual fragments following ureteroscopic lithotripsy: incidence and predictors on postoperative computerized tomography. J Urol. 2012 Dec;188(6):2246–51.

24. Pearle MS. Is ureteroscopy as good as we think? J Urol. 2016 Apr;195(4 Pt 1):823–4.

25. 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 Jul;194(1):137–43.

26. Somani BK, Giusti G, Sun Y, et al. Complications associated with ureterorenoscopy (URS) related to treatment of urolithiasis: the Clinical Research Office of Endourological Society URS Global study. World J Urol. 2017;35(4):675–681.

27. Cindolo L, Castellan P, Scoffone CM, et al. Mortality and flexible ureteroscopy: analysis of six cases. World J Urol. 2016 Mar;34(3):305–10.

28. Bhanot R, Pietropaolo A, Tokas T, et al. Predictors and strategies to avoid mortality following ureteroscopy for stone disease: A systematic review from European Association of Urologists Sections of Urolithiasis (EULIS) and Uro-technology (ESUT). Eur Urol Focus. 2022;8(2):598–607.

29. Zeng G, Zhao Z, Mazzon G. European Association of Urology Section of Urolithiasis and International Alliance of Urolithiasis Joint Consensus on Retrograde Intrarenal Surgery for the Management of Renal Stones. European Urology Focus. 2020 Oct.

30. Bhojani NB, Miller LE, Bhattacharyya S, et al. Risk factors for urosepsis after ureteroscopy for stone disease: a systematic review with meta-analysis. J Endourol. 2021 Jul;35(7):991–1000.

31. Geraghty RM, Pietropaolo A, Villa L, et al. Post-ureteroscopy infections are linked to pre-operative stent dwell time over two months: Outcomes of three European endourology centres. J Clin Med. 2022;11(2):310.


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Oliver Wiseman, MD, is a Boston Scientific consultant and was compensated for his contribution to this article. This information presented does not constitute medical or legal advice, and Boston Scientific makes no representation regarding the medical benefits included in this information. 

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