Flexible Ureteroscopy and Laser Lithotripsy Using a Flexible and Navigable Ureteral Access Sheath Are Equally Safe and Effective whether Done in a Sitting or a Standing Position: A Multicenter Study by European Association of Urology-Endourology and the Flexible and Navigable Suction Access Sheath Collaborative Group

Abstract

Introduction:

Flexible ureteroscopy (FURS) using the flexible and navigable suction ureteral access sheath (FANS) is a novel technique for treatment of kidney stones. We aimed to compare outcomes of FURS with FANS in the sitting vs standing position.

Patients and Methods:

We analyzed adult patients from 21 centers who underwent FURS with FANS, divided according to whether the surgeon operated in a sitting or standing position. Baseline demographics, operative parameters, and 30-day outcomes were compared. Multivariable logistic regression was used to identify potential predictive factors for zero residual fragments (ZRF).

Results:

There were 457 patients in the sitting group and 247 patients in the standing group. In the sitting group, more patients had the surgical procedure under general anesthesia (p = 0.022). Disposable scopes were preferred in the standing group (p < 0.001). Median lasing and ureteroscopy time were significantly shorter in the siting group, but there was no difference in total surgical time (median 45 vs 46 minutes, p = 0.102). A larger but nonsignificant percentage of grade 1 access sheath insertion injuries were reported in the standing position. Multivariable logistic regression analysis showed that stone volume (odds ratio [OR]: 0.82, 95% confidence interval [CI]: 0.72–0.93, p = 0.003) and operative time (OR: 0.99, 95% CI 0.99–1.00, p = 0.002) but not surgeon position (OR: 1.04, 95% CI: 0.75–1.44, p = 0.82) were significant predictors of ZRF. Procedural safety was not compromised significantly.

Conclusions:

FURS with FANS is equally safe and effective in the sitting and standing positions. This study provides the impetus to improve FURS ergonomics, especially with the move toward its use in complex and large stones.

Introduction

Flexible ureteroscopy (FURS) using the flexible and navigable suction ureteral access sheath (FANS) is a novel yet effective technique for treatment of kidney stones in both adults and children.^1,2 Traditionally, FURS is performed with the surgeon in a standing position,³ whereas semirigid ureteroscopy is suggested to be performed in a sitting position.⁴ Proper surgeon positioning, systematic operating theater layout, correct monitor and pedal position, and even anesthetic considerations are important factors to decrease the musculoskeletal strain on surgeons, increase work efficiency, and improve the surgical experience.⁵ In a survey on ergonomics in FURS, one notable consideration was for surgeons to be seated during the procedure to reduce musculoskeletal pain.⁶ In fact, robotic ureteroscopy specifically addresses this concern,⁷ although it is not widely used.

Although there are different table tilting techniques that have been touted to improve stone-free rate (SFR) and ergonomics,⁸ there exists a paucity of literature that reports on outcomes of FURS with surgeons specifically in a sitting position. One such suggestion was the modified ergonomic lithotripsy position, wherein three surgeons could be seated throughout FURS, even in cases with large stone burden, with no added instruments, low patient morbidity, and good surgical outcomes in 100 cases.⁹ In FANS, it has been noted that the technique involves additional manipulation of the ureteral access sheath (UAS) within different parts of the kidney alongside movement of the scope itself. Once the stone is fragmented, aspiration of fragments is done by retrograde manual scope withdrawal through the sheath to the Y-connector. If done frequently, especially in large stone volumes, this could lead to shoulder strain or fatigue. This is particularly relevant given that FANS has proven useful for stones >2 cm in diameter¹⁰; hence, even though current guidelines accept FURS as safe for stones up to 2 cm in diameter,¹¹ its use in larger stone volumes is gaining new momentum with the advent of FANS.¹² Aside from FURS, many surgical procedures in urology have seen adaptations to improve ergonomics—ranging from transurethral resection of the prostate¹³ to supine percutaneous nephrolithotomy¹⁴ and specific platforms for laparoscopic procedures.¹⁵ All these procedures can safely be done in the sitting position to mitigate joint strain on surgeons.

Suction has been touted as a harbinger of change in the setting of FURS.^16,17 Aside from the improvement in SFR as compared with standard FURS, the adoption of FANS performed in a seated position for the surgeon could improve operator experience—but only if this is as feasible and safe as compared with the standing position. Hence, we conducted a prospective study, comparing outcomes between procedures that were performed in the sitting vs standing procedure.

Patients and Methods

Patients and procedures

Patients from 21 centers with renal stones who underwent FURS with FANS from August 2023 to August 2024 were enrolled after institutional review board approval was obtained by the respective participating institutions with consent for use of anonymized data. This was registered under an ethical board-approved FANS registry curated by the Asian Institute of Nephrology and Urology, Hyderabad, India, which was the primary site (protocol number AINU-EC/28/2023). Only patients in whom FANS was employed were enrolled; hence, this study did not consider outcomes or follow-up for patients in whom FANS was unsuccessful or could not be done.

Baseline and operative characteristics were gathered. Inclusion criteria were patients aged ≥18 years with normal renal anatomy (i.e., no congenital malformations) undergoing FURS for single or multiple renal stones. One preoperative and one 30-day non-contrasted computed tomography (NCCT) scan to assess stone features and residual fragments after the index procedure was mandated. The stone volume was measured from the CT scan using the bone window applying the ellipsoid formula (length × width × depth × π × 0.167).

Positive preoperative urine cultures were treated in accordance with local antibiotic sensitivity. Anticoagulant or antiplatelet use was stopped 3 days before the operation and was restarted at the surgeon’s discretion. The scope and FANS model and sheath size and the energy source used for lithotripsy depended on local availability and the surgeon’s preference. Pre-stenting was not mandatory and exit strategies included stent placement, an overnight ureteral catheter, or no drainage tube according to the surgeon’s own preference. Children and patients with abnormal renal anatomy, ureteral stones, or incomplete data records were excluded.

For the sitting position, the chair with a lumbar support was adjusted so that the operator’s forearms are parallel to the floor when manipulating the ureteroscope and other instruments with elbows at a 90°–100° angle. The monitor was positioned at eye level and directly in front of the surgeon, approximately 1 m away. For the standing position, the height of the operating table was adjusted so that the surgeon’s elbows were flexed at approximately 90°–100° when handling instruments. The table was high enough to avoid leaning forward but low enough to prevent shoulder elevation. The monitor was directly in front of the surgeon, positioned at eye level, and at a distance of about 1 m. Surgeons typically kept their elbow close to the body, flexed at around 90°, maintaining a neutral wrist position while manipulating the ureteroscope, and their feet were hip-width apart to provide a stable base.

Follow-up and study outcomes

The primary aim of this study was to report the technical feasibility, perioperative, and 30-day outcomes of FANS for renal stones in sitting vs standing surgeon position. We specifically aimed to assess if surgeon position affects the ability to navigate FANS in the pelvicalyceal system (PCS) of normal kidneys in adults.

SFR assessment was done by asking each surgeon to visually inspect every part of the PCS before the sheath was removed.

Postoperative residual fragments (RF) and stone-free status (SFS) were evaluated with an NCCT scan within 30 days and graded as follows:

Grade A: 100% stone-free, indicating zero RF (ZRF)

Grade B: Single RF ≤2 mm in maximum diameter

Grade C: Single RF 2.1–4 mm in maximum diameter

Grade D: single or multiple RF >4 mm in maximum diameter

For Grades A, B, and C, these were expressed as cumulative data—that is, Grade B would include Grade A patients, and Grade C would include Grade B and Grade A patients.

Additionally, we defined an SFS category (Grade A + B)—these patients were not candidates for re-intervention.

Surgeons were asked to grade their experience of FANS use at the end of each case using a 5-point Likert-type scale (1 = excellent; 2 = very good; 3 = good; 4 = average; 5 = difficult). Secondary outcomes of interest included perioperative and complications within 30 days, such as bleeding, transfusion, ureteral injury, PCS injury, and sepsis defined according to the Third International Consensus (Sepsis-3). Patients’ loin pain score was measured with a standard 10-point visual analog score at day 1 post-FURS or upon discharge for day operation cases. Readmission within 30 days or definitive reintervention was also documented. Any need for conversion from the original position was to be documented.

Statistical analysis

All statistical analyses were performed using R Statistical language, version 4.3.0 (R Foundation for Statistical Computing, Vienna, Austria), with p < 0.05 indicating statistical significance. Continuous variables were described using median and interquartile range, whereas categorical variables were described using absolute numbers and percentages.

Patients were divided into two groups, according to whether the surgeon performed the procedure sitting or standing. Patient demographics, perioperative parameters, and 30-day outcomes were compared between the groups using the χ² test or Fisher exact test for categorical parameters and the Kruskal-Wallis test for continuous variables. Potential predictive factors for Grade A SFS on 30-day NCCT were entered into an a priori multivariable logistic regression model.

Results

A total of 704 patients were included for analysis. Nine surgeons reported doing cases in sitting position and 12 surgeons performed FURS in the standing position There were 457 patients in the sitting group and 247 in the standing group. Table 1 shows baseline characteristics of patients. There was no significant difference in gender (p = 0.123), median age (51 vs 50, p = 0.644), proportion of pre-stented patients (p = 0.591), stone volume (1440 vs 1407 mm³, p = 0.659), and Hounsfield units (1100 vs 1100, p = 0.576). Significantly, more patients had a middle pole/interpolar or upper pole stone in the standing group (p = 0.005).

Table 1.

Baseline Characteristics

	Sitting (N = 457)	Standing (N = 247)	p-Value
Age	51 (35, 61)	50 (36, 62.5)	0.644
Male sex	241 (52.7)	146 (59.1)	0.123
ASA score			0.077
1	249 (55.5)	119 (46.7)
2	162 (36.1)	112 (43.9)
3	38 (8.5)	24 (9.4)
BMI, kg/m²	26 (25, 30)	26 (24, 29)	0.327
Preoperative antibiotics	319 (77.6)	119 (81.5)	0.385
Pre-stented	289 (63.2)	162 (65.6)	0.591
Hounsfield units	1100 (978, 1213)	1100 (900, 1291)	0.576
Stone diameter			0.519
<1 cm	86 (20.9)	36 (24.7)
1.1–2 cm	258 (62.8)	84 (57.5)
>2 cm	67 (16.3)	26 (17.8)
Stone volume, mm³	1440 (829, 2112)	1407 (853, 2166)	0.659
Stone location			0.005
Multiple locations	19 (4.2)	6 (2.4)
Upper pole	102 (22.3)	65 (26.3)
Middle pole/interpolar	186 (40.7)	123 (49.8)
Lower pole	150 (32.8)	53 (21.5)

All values are reported as N (%) or median (interquartile range).

Bolded cells are significant p < 0.05.

ASA = American Society of Anesthesiologists; BMI = body mass index.

Table 2 shows intraoperative characteristics. In the sitting group, a significantly higher proportion of patients had operation under general anesthesia (82.5% vs 74.9%, p = 0.022) and disposable scopes were less frequently used (28.4% vs 53.8%, p < 0.001); 10/12 Fr FANS was the most common sheath employed in the standing group (47.0%) as opposed to 11/13 Fr in the sitting group (47.8%). Regarding the type of laser, pulsed Thulium:YAG was the most used in standing group patients (64.4%) and Thulium fiber laser in sitting group patients (35.1%). Median lasing and ureteroscopy time were significantly shorter in the siting group, but there was no difference in total surgical time (median 45 vs 46 minutes, p = 0.102). Access to all parts of kidney by FANS was greater in the sitting group (91.0% vs 85.4%, p = 0.032). Ease of performing suction-aspiration and maneuverability of sheath and scope in PCS were better in the standing group, whereas visibility during lasing was reportedly better in the sitting group.

Table 2.

Intraoperative Characteristics

	Sitting (N = 457)	Standing (N = 247)	p-Value
Procedure under general anesthesia	377 (82.5)	185 (74.9)	0.022
Procedure under spinal anesthesia	80 (17.5)	62 (25.1)
Sheath size, Fr			<0.001
12/14	98 (21.5)	53 (21.5)
11/13	218 (47.8)	78 (31.6)
10/12	140 (30.7)	116 (47.0)
Disposable scope	130 (28.4)	133 (53.8)	<0.001
Laser			<0.001
LPHL	89 (20.0)	57 (23.1)
HPHL/HLM	114 (25.6)	1 (0.4)
TFL	156 (35.1)	30 (12.1)
p-Tm:YAG	86 (19.3)	159 (64.4)
Median dusting settings, J/Hz	0.4/30	0.4/25
Lasing time	15 (11, 22)	17 (12, 30)	0.001
Ureteroscopy time (actual time spent handling the scope intraoperatively)	31 (23, 40)	34 (25, 55)	0.002
Total operation time (from start of cystoscopy, to exit strategy)	45 (37, 55)	46 (37, 69)	0.102
Preferentially used Stone clearance technique			<0.001
Dusting with aspiration	174 (38.1)	107 (43.3)
Fragmentation with aspiration	76 (16.6)	1 (0.4)
Combination with aspiration	207 (45.3)	139 (56.3)
Need for basketing to aid stone repositioning	36 (7.9)	30 (12.1)	0.086
Sheath able to access all of kidney	416 (91.0)	211 (85.4)	0.032
Exit strategy			<0.001
Stent	310 (67.8)	200 (81.0)
Overnight ureteral catheter only	125 (27.4)	32 (13.0)
Nil stent/catheter	22 (4.8)	15 (6.1)
Likert scale rating by surgeon in ease of handling the sheath
Ease of suction	2 (1, 2)	1 (1, 2)	<0.001
Ease of maneuverability of sheath and scope in PCS	2 (2, 2)	2 (1, 2)	0.001
Visibility during lasing	1 (1, 2)	1 (1, 3)	0.028

All values are reported as N (%) or median (interquartile range).

Bolded cells are significant p < 0.05.

HPHL/HLM = high-power Holmium laser/Holmium laser with MOSES technology; LPHL = low-power Holmium laser; PCS = pelvicalyceal system; p-Tm:YAG = pulsed Thulium-YAG laser; TFL = Thulium fiber laser.

Table 3 shows postoperative outcomes. Overall, the incidence of perioperative complications was low in both groups. The incidence of mild oozing resulting from sheath manipulation in the PCS was higher in sitting group patients (7.2% vs 2.4%, p = 0.013). There were no cases of sepsis. No surgeon had to abandon the procedure or change their position. Day 1 loin pain score did not differ significantly. Regarding 30-day SFR, there was a significantly higher proportion of Grade A + B status in the sitting group (97.2%) compared with the standing group (88.3%, p < 0.001).

Table 3.

Postoperative Outcomes

	Group 1 sitting (N = 457)	Group 2 standing (N = 247)	p-Value
Mild oozing^a resulting from sheath manipulation in the PCS	33 (7.2)	6 (2.4)	0.013
Case abandoned	0	0	NA
Need for surgeon to change position	0	0	NA
Postoperative transfusion	1 (0.2)	0	>0.99
Ureteral injury owing to UAS placement (Traxer grade A)	11 (2.4)	8 (3.2)	0.684
PCS injury caused by sheath placement needing stenting	2 (0.4)	3 (1.2)	0.483
30-day stone-free status on NCCT scan			NA
A (zero residual fragments)	277 (60.6)	146 (59.1)
B (cumulative)	444 (97.1)	218 (88.2)
C (cumulative)	452 (98.9)	243 (98.3)
D (non-stone-free)	5 (1.1)	4 (1.6)
Stone free status (A + B)	444 (97.2)	218 (88.3)	<0.001
Fever requiring antibiotics (CD1)	6 (2.7)	3 (3.6)	0.963
Sepsis (CD4)	0	0	NA
Loin pain score	1 (1, 2)	1 (1, 2)	0.989
Reintervention for stone	8 (1.8)	22 (8.9)	<0.001
FURS/SWL/unknown	5/0/3	18/1/3

All values are reported as N (%) or median (interquartile range).

Bolded cells are significant p < 0.05.

Mild oozing defined as minimal, self-limiting bleeding observed from the renal collecting system, and/or calyceal mucosa, typically characterized by light discoloration of irrigation fluid and no significant obstruction of vision caused by bleeding.

CD = Clavien–Dindo; FURS = flexible ureteroscopy; NCCT = non-contrast computed tomography; PCS = pelvicalyceal system; SWL = extracorporeal shockwave lithotripsy; UAS = ureteral access sheath.

Multivariable logistic regression analysis (Table 4) showed that stone volume (odds ratio [OR]: 0.82, 95% confidence interval [CI]: 0.72–0.93, p = 0.003) and operative time (OR: 0.99, 95% CI: 0.99–1.00, p = 0.002) were associated with lower odds of ZRF. Notably, surgeon position did not influence the outcome (OR: 1.04, 95% CI: 0.75–1.44, p = 0.82).

Table 4.

Predictors of Zero Residual Fragments (Residual Fragment Grade A)

	OR	95% CI	p-Value
Standing (vs sitting)	1.04	0.75–1.44	0.82
Stone location (vs multiple locations)
Upper pole	1.71	0.69–4.24	0.246
Middle pole/interpolar	1.14	0.47–2.73	0.767
Lower pole	1.06	0.44–2.56	0.896
Stone volume	0.82	0.72–0.93	0.003
Prestented	0.86	0.61–1.19	0.353
Total operation time	0.99	0.99–1.00	0.002

All values are reported as N (%) or median (interquartile range).

Bolded cells are significant p < 0.05.

CI = confidence interval; OR = odds ratio.

Discussion

Adopting novel technologies into daily practice requires that they are efficacious, economically viable, and easy to use.¹⁸ From a user perspective, ergonomics is a key determinant for surgeons to ensure sustainable use of equipment. Efficacy and safety of using FANS in FURS and its global adoption in adults and children have been well established.^1,2 As more surgeons use FANS, it is important to study the different parameters that may contribute to improving efficacy without compromising safety. In the initially published papers on FANS, there was no reference to surgeon position while performing this procedure.¹ In fact, this is a less alluded-to topic in literature and has not been studied deeply for FURS. Ergonomically, FURS in a sitting posture should be more comfortable and may have less strain on the surgeon. Although this may certainly be more comfortable, it remains to be seen if this impacts operative outcomes. In our study, albeit the lack of randomization, the large number of included procedures allowed for a real-world comparison of the practices of experienced surgeons. The high number of cases also suggests that many surgeons have easily adapted to performing FANS in a sitting position and hence allowing meaningful comparisons between both techniques.

Surgeons accustomed to sitting and performing FURS made a natural transition to FANS in sitting with relative ease. As these data are from urologists who have prior experience with FURS and FANS, perhaps this is reflective of their expertise. As all steps of the operation were seamlessly replicated in the sitting position as per the original step-by-step video on FANS¹⁹ described with the surgeon in a standing position, this can indeed be perceived as a positive step forward with respect to feasibility. In our series, there was no case abandoned between or surgeons having to change position; no grievous intraoperative injuries or postoperative sepsis was reported; and similar perioperative safety profiles were seen. This highlights the utility of this option especially in large stones where fatigue has been reported and ergonomics play a significant role in improving the surgeon experience in FURS.⁵ In fact, a recent multicenter study has shown that flexible suction sheaths are feasible with a favorable safety profile for 2–4 cm stones, albeit the need for longer operative times and an increased number of scope withdrawals to suction out fragments.¹² Both these may cause a physical strain on surgeons, yet this needs to be determined by defined ergonomic questionnaires, which can subjectively determine which position is ergonomically better for FURS in large stone burden.

Indeed, with respect to usage of equipment, similar lasing strategies were noted in both groups, with the combination approach of dusting plus fragmentation plus aspiration being equally used in both groups. Notably, laser usage differed between groups, but this is likely reflective of availability at respective institutions rather than a selective preference for a particular laser type as reported by surgeons involved in this study. A significantly higher percentage of single-use disposable scopes was used in standing positions. This may be because of their ergonomic lightweight design, for which standing surgeons are not too bothered by the weight; conversely, sitting surgeons are able to handle the heavier reusable scope more efficiently. It is, however, also possible that this is attributable to availability rather than preference. Scope weight is an interesting future consideration as a variable to choose the seated position for complex FANS procedures.

Subjective assessment of surgeons’ perceptions of FANS was done using a 5-point Likert score. Even though some differences in ease of use and ease of maneuverability were seen, these may not necessarily be key factors to decide what position a surgeon adopts. These may also be because of different sizes, types, and brands of scopes and sheaths used.

Importantly, the FANS is after all an access sheath and injuries will occur if not used carefully. This has also been reported in other series as well.^20,21 The numerically higher percentage of UAS injuries in the standing group does beg the question whether surgeons’ position has any impact on buckling force insertion experienced during sheath insertion.²² It is well researched that UAS design itself has a significant impact on insertion force²³; it still remains to be seen if a seated position allows use of lesser force for a smoother insertion and manipulation of the sheath.

Suction in general,¹⁷ and especially FANS, has shown that all aspects of FURS are significantly better for the patient, especially SFR.^2,12,20,21 In our study, this was also clearly demonstrated with only stone volume and surgical time—but not surgeon position—significantly impacting the RF Grade A outcome. Yet, lasing and ureteroscopy time were significantly shorter in the sitting group. We may postulate that surgeons were more ergonomically relaxed and focused during a sitting procedure, an established key factor for surgical success.⁵

This study was not without limitations. Although it reflects the real-world practice of surgeons using FANS, it is not a randomized trial and hence cannot objectively favor either position over the other. This study also did not account for surgeons alternating between the sitting and standing position throughout the operation. Yet, the large dataset spanning several centers ascertains that FANS can safely be done in the sitting position with equal efficacy as the standing position. A lack of objective ergonomic questionnaires precludes categorically declaring the sitting position an ergonomically superior position. Logically, however, a sitting posture is the preferred way to do transurethral procedures, and this study opens up the possibility of sitting during FURS as well. Importantly, this decision can be made without the surgeon being concerned of increased operative morbidity or worse SFR outcomes. Akin to the first global FANS study, we too can say that FURS with FANS in sitting position is safe and feasible and leads to a high SFR. The surgeon position itself does not significantly influence this effectiveness.

Our study reports real-world experiences of performing FANS in sitting and standing positions with regard to ease of use, manipulation, and navigation of the scope and sheath. Yet, for an impactful study on ergonomics and surgeon quality of life, dedicated questionnaires are needed to address kinesiology and muscle fatigue as one needs to insert and withdraw the FANS using different sheath and scope sizes. Considerations include fluid management systems, sheath design, presence of an assistant to hold the sheath, and laser, which were beyond the scope of this study.

Looking forward, a randomized controlled trial with appropriate ergonomic questionnaires to ascertain the usefulness of converting to the sitting position would be desired. This is especially relevant to surgeons who perform FURS with FANS on large or complex stones, wherein the increased operative time may further highlight ergonomic differences.

Conclusion

Urologists performing FURS with FANS in sitting positions have shown that this is definitely feasible and adaptable into real-world practice as compared with the standing position. Akin to previous studies, high ZRF status and overall SFR are achievable with no added morbidity. This study provides the driving force to further improve FURS ergonomics, especially with the move toward its use in complex and large stones.

Footnotes

Authors’ Contributions

K.Y.F.: Methodology, software, formal analysis, investigation, data curation, writing—original draft, and visualization. B. Somani: Conceptualization, methodology, investigation, writing—original draft, writing—review and editing, and project administration. P.J.-J.: Conceptualization, methodology, investigation, writing—original draft, writing—review and editing, and project administration. D.C.: Conceptualization, methodology, investigation, writing—original draft, writing—review and editing, and project administration. C.T.H.: Methodology, investigation, and writing—review and editing. J.-L.K.: Methodology, investigation, and writing—review and editing. C.-A.C.: Methodology, investigation, and writing—review and editing. W.K.: Methodology, investigation, and writing—review and editing. C.K.: Methodology, investigation, and writing—review and editing. K.P.: Methodology, investigation, and writing—review and editing. B. Soebhali: Methodology, investigation, and writing—review and editing. M.Z.: Methodology, investigation, and writing—review and editing. S.B.H.: Methodology, investigation, and writing—review and editing. M.E.: Methodology, investigation, and writing—review and editing. Y.Q.T.: Methodology, investigation, and writing—review and editing. P.N.C.: Methodology, investigation, and writing—review and editing. L.T.: Methodology, investigation, and writing—review and editing. A.S.: Methodology, investigation, and writing—review and editing. S.Y.: Conceptualization, methodology, investigation, writing—original draft, writing—review and editing, and project administration. O.T.: Conceptualization, methodology, investigation, writing—original draft, writing—review and editing, and project administration. V.G.: Conceptualization, methodology, investigation, writing—original draft, writing—review and editing, and project administration.

Author Disclosure Statement

The authors declare no conflicts of interest.

Funding Information

No external funding was received for the conduct of this research.

Abbreviations Used

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