Is there a “Best ureteroscope” for flexible ureteroscopy with FANS: an EAU-endourology perspective

Understanding quadrifecta principles in flexible ureteroscopy (F-URS) for kidney stone disease ¹ reveals that flexible and navigable suction access sheath (FANS) is remarkably effective and safe for adults, children, and in large stone burden and bilateral renal stones outperforming conventional and non-bendable suction ureteral access sheaths.^2–4 Evidence shows that FANS increases ablation efficacy, especially when paired with new-generation lasers,^5,6 and mitigates intrarenal pressure (IRP) deleterious effects.^7–9 Studies conclude that pre-stenting is not always necessary if caution is exercised during surgery, and it is an anatomically and physiologically safe procedure.^10–12 FANS helps achieve zero-fragment stone-free status as early as 24 h after surgery,^13,14 reducing reintervention and postoperative stenting needs. ¹⁵ Research aims to enhance sheath design and techniques, particularly for lower pole stones and IRP management.^8,16,17

Given the above, it is natural to infer that for optimal performance in a good sheath, deflection properties will directly depend on the properties of the scope used. Hence, it is imperative to identify the ideal scope for FANS in F-URS. This can improve SFR and optimize radiation exposure, costs, and environmental impact. ¹⁸ In the pre-suction era of F-URS, single-use scopes were preferred for better outcomes, while reused scopes showed inferior intra- and peri-operative results. ¹⁹ Table 1 summarizes limited evidence from studies on FANS to guide surgeons in selecting the best scope for their practice and outlines the study characteristics and mentioning the relevance of scope characteristics on FANS outcomes. While most studies specify reusable or single-use scopes, few discuss their impact, highlighting a lack of data. Single-use scope is preferred in modern endourology. ²⁰ As scope designs improve, we provide a framework for scope characteristics to consider for a better FANS surgical experience (Table 2). While there is a move toward using single-use ureteroscopes, literature concerning the environmental footprint of single-use ureteroscopy is worryingly lacking, and further research is therefore imperative given the global climate crisis and the significant contribution that healthcare services have to the environmental problem. ²¹ Similarly, the cost of reusable scopes needs to be balanced with the cost of single-use ureteroscopes.^22,23

Table 1.

Relevance of scope characteristics on FANS outcomes.

Study focus (main utility of FANS)	Scope used	Relevance of scope characteristics for FANS outcomes discussed (Y/N)	Inference of the study
Large stone burden 5	SUS	N	Excellent SFR, mainly SUS
Paediatric 3	SUS	N	Safe and excellent 30-day outcomes with SUS
Multicenter study for 30 days, 2 24 h, 15 and 3-month outcomes 12 in normal kidneys	Both	Y	Mostly SUS and tip >8 Fr best for 11 Fr; equally good SFR Scope influence on outcomes was not discussed
Intrarenal pressure and FANS9,11	SUS	N	IRP control is better Scope influence on outcomes was not discussed
Bilateral stones 4	Both	Y	SUS may be better for bilateral ZRF
Sheath size/deflection 2	Both	Y	Smaller sheath/smaller scope tip. For SUS 7.5 Fr/10 or 11 Fr sheath
Pre-stenting 13	Both	Y	No mandatory but smaller scopes and sheaths, lesser injury
Acute kidney injury 14	Both	N	No relevance to acute kidney injury
Radiation 19	Both	Y	Significantly less radiation dose and time with SUS
FANS vs traditional 5	Both	N	FANS is the winner, independent of the scope used
Lower pole stone 18	Both	Y	Only TFL matters; SUS may be useful
Lasing strategy7,8	Both	Y	TFL and SUS best
Ablation efficacy 7	SUS	N	Decreased operative times and higher ablation efficiency

FANS, flexible and navigable suction access sheath; IRP, intrarenal pressure; SFR, Stone free rate; SUS, single-use scope; TFL, thulium fiber laser; ZRF, Zero residual fragments.

Table 2.

Scope characteristics that could help improve the FANS experience.

Scope feature	Utility in FANS
Strong tip	To flex the sheath in all directions and minimize damage during repeated scope withdrawal and insertion
Strong shaft increased tip flexibility	Able to bend any sheath size into the lower pole and withstand torque in complex anatomy
Excellent vision	Especially during laser
Good torque	To prevent shaft strain and minimize breakage
Lightweight	Prevent arm strain in large stone burdens and allow ease of in and out of the sheath movement
Ergonomic handle	Better grip and prevent hand strain when managing a larger stone burden
Small tip and shaft	Best suited for pediatric cases, unstented and smaller ureter. May allow the sheath size to be further decreased.

FANS, flexible and navigable suction access sheath.

Key take-home points

• Single-use scopes are preferred as they provide optimal deflection with each use, which is crucial for procedures involving children, lower pole stones, and managing large stone burdens and same-sitting bilateral stone surgery.

• Reusable scopes may be utilized for adults with normal anatomy; however, surgeons should exercise caution regarding the deflection and vision properties of these scopes, especially when using FANS.

• Currently with FANS, IRP monitoring is best conducted using single-use sheaths and scopes exclusively.

• There is a need for evidence to determine the efficacy of the 6.3 Fr scope/9 Fr sheaths combination compared to the 7.5 Fr/10 Fr–11 Fr combinations. Studies suggest that slimmer shafts and smaller tips pair best with smaller sheaths. Current studies have minimal reference to 8 Fr scopes with 12 Fr sheaths.

• Information regarding the most suitable scope and sheath for anomalous anatomy is absent, as all studies reported normal renal anatomy.

• Single-use scopes may offer significant advantages in reducing radiation exposure and procedure time.

• Lasers and stone volume directly impact zero residual fragments and overall stone-free rate. While visibility and effective suction are crucial for any lasing strategy, single-use scopes alone may or may not have a direct effect on these factors.

• Ergonomics were not discussed and necessitate future dedicated studies.

In conclusion, single-use scopes for F-URS with FANS are the preferred choice. While reusable scopes are still in use, the potential for sheath miniaturization and advancements in integrated scopes for pressure and temperature management might eventually phase them out and seem best suited for IRP measurement with FANS. A pragmatic approach involves considering both cost and surgical experience when selecting the scope for FANS, as there is no specific evidence-based study addressing this matter.