Tip-flexible suctioning ureteral access sheath combined with flexible ureteroscope: a single-institution experience including in vitro experiments

Abstract

Background

To evaluate the clinical application value of tip-flexible suctioning ureteral access sheath (TFS-UAS), this study compares the efficacy and safety of TFS-UAS versus traditional ureteral access sheath (T-UAS) in treating unilateral renal or proximal ureteral calculi, and further summarizes the usage strategy of TFS-UAS by synthesizing vitro experiment and surgical best practices.

Methods

A retrospective analysis was conducted on 196 patients with renal or proximal ureteral calculi treated with FURS and holmium laser lithotripsy at Shuguang Hospital Affiliated to Shanghai University of Traditional Chinese Medicine. Patients were divided into TFS-UAS and T-UAS groups. Primary data included operative time, immediate SFR (iSFR), and 2-week SFR. Secondary data encompassed changes in blood parameters (leukocytes, hemoglobin, urea nitrogen, creatinine), complications, and hospital stay.

Results

This retrospective study found that urologists preferred to use TFS-UAS for larger (17.73 ± 7.79 mm vs. 12.56 ± 5.14 mm, P < 0.001), harder (1156.52 ± 420.15 vs. 778.39 ± 513.46 Hounsfield units, P < 0.001), and more complex (modified STONE score: 10.86 ± 2.51 vs. 7.37 ± 2.28, P < 0.001) upper urinary tract calculi. No significant differences in operative time or SFR were found between the TFS-UAS and T-UAS groups overall. However, for stones ≥ 15 mm, those that were larger(22.57 ± 6.35 mm vs. 18.70 ± 3.82 mm, P = 0.001), harder(1160.76 ± 382.84 vs. 896.56 ± 465.33, P = 0.007), and more complex(modified STONE score: 11.43 ± 2.40 vs. 8.63 ± 2.31, P < 0.001), TFS-UAS significantly reduced operative time (53.92 ± 21.77 vs. 65.76 ± 22.43 min, P < 0.001) and improved iSFR(91.89% vs. 73.17%, P = 0.063), 2-week SFR(81.08% vs. 56.10%, P = 0.018).

Conclusions

TFS-UAS combined with FURS significantly improves operative efficiency and SFRs for upper urinary tract calculi ≥ 15 mm, demonstrating clinical advantages.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12894-025-01922-4.

Introduction

As a common urological disorder, urolithiasis affects approximately 8.1% of the population in China [1–3]. Ureteral obstruction caused by urolithiasis may lead to flank pain, urinary tract infection(UTI), and renal impairment, thereby significantly impacting patient health [3, 4]. Current urological guidelines in China, the US, and Europe recommend retrograde intrarenal surgery (RIRS) as the first-line treatment for upper urinary tract calculi < 20 mm [5], while percutaneous nephrolithotomy (PCNL) is preferred for stones > 20 mm [3, 4]. With advancements in flexible ureteroscope (FURS) technology, upgraded ureteral access sheaths (UAS), high-power laser systems, and accumulated clinical expertise, RIRS indications have expanded [3, 6]. Multiple studies have reported comparable stone-free rates (SFR) between RIRS and minimally invasive PCNL (mPCNL) for stones > 20 mm [7–9]. Consequently, guidelines now permit experienced operators to treat renal stones up to 30 mm with RIRS [4].

Traditional UAS (T-UAS) requires basket extraction for stone fragments, leaving residual dust for spontaneous passage. In addition, its rigid tip design presents several drawbacks, including uncontrolled intrarenal pressure (IRP); difficulty in managing small lower calyceal stones with narrow infundibulopelvic angles (IPA) or stones with a large burden; compromised visualization due to stone dust and blood clots; and an increased risk of postoperative infectious complications [3, 10, 11]. In recent years, the introduction of FURS has significantly reduced the operational and maintenance costs associated with reusable flexible ureteroscopes in clinical practice [3]. Tip-flexible suctioning UAS (TFS-UAS), featuring an 8 cm flexible distal segment capable of navigating the ureteropelvic junction (UPJ) into target calyces, enhances stone clearance, lowers IRP, and reduces complications by combining vortex flow and suction [5, 9, 12–20]. Thus, clinicians have increasingly adopted FURS with TFS-UAS for stones > 20 mm. Wang et al. demonstrated that comparable SFR between TFS-UAS + FURS and mPCNL for 20–30 mm upper urinary tract calculi, with fewer bleeding/pain complications and shorter hospitalization [9]. This retrospective study evaluated the efficacy of TFS-UAS versus T-UAS in upper urinary tract calculi management at our hospital from March 2023 to August 2024, supplemented by in vitro experiments to elucidate clinical applications.

Materials and methods

Patients

This study included 196 cases of renal calculi or upper ureteral calculi meeting inclusion criteria at Shuguang Hospital Affiliated to Shanghai University of Traditional Chinese Medicine from March 2023 to August 2024. Retrospective data collection covered: demographic parameters (age, gender, BMI), maximum stone diameter, maximum computed tomography (CT) value of stone, modified STONE score, preoperative urine culture, perioperative indicators (blood leukocytes, hemoglobin, BUN, serum creatinine, operative duration, immediate stone-free rate (iSFR), postoperative complications, etc.), SFR postoperatively at 2 weeks.

Stone burden was determined by measuring maximum stone diameter on CT urography. For multiple stones, the sum of maximum diameters was calculated. All patients underwent preoperative urine culture and CT urography. If preoperative urinalysis indicated UTI, culture-directed antibiotics were administered to treat the infection. For all other patients, routine prophylactic antibiotics were given one day prior to surgery to prevent infection. No significant hematuria or urosepsis occurred postoperatively.

Inclusion criteria

• CT-confirmed renal/upper ureteral calculi ≤ 40 mm.

• Use of TFS-UAS or UAS.

• No surgical contraindications.

• Operations performed by the same surgical team.

Exclusion criteria

• Uncontrolled UTI or surgical contraindications.

• Incomplete clinical data.

• Severe cardiopulmonary/hepatic dysfunction, coagulation disorders.

• Ureteral stricture, bilateral stones.

• Patients preoperative evaluated to proceed staged procedures or combined PCNL.

This study was conducted in accordance with the ethical standards for human subjects research established by the Institutional Review Board (IRB) of our hospital.

Description of the procedure

Operations were conducted in lithotomy position under general anesthesia. Primary lithotripsy: first, a rigid F6/7.5 ureteroscope was used to explore the ureter, followed by placement of a safety guidewire. For upper ureteral stones, holmium laser was initially applied to rapidly fragment the stones and push them into the renal pelvis. Secondary lithotripsy: First, a rigid F8/9.8 ureteroscope was employed to remove the ureteral stent. Subsequent exploration was performed, and a safety guidewire was reinserted.

TFS-UAS group: Based on intraoperative exploration, TFS-UAS (Specifications: F10-12/F11-13/F12-14; Manufacturer: Shenzhen Cooper Medical Co., Ltd., Approval No.: YXZZ20162020589) was advanced over the guidewire to UPJ or below. The guidewire was then replaced with an F8.6 disposable FURS (Manufacturer: Anhui Happiness Works Medical Equipment Co., Ltd., Approval No.: WXZZ20222060243). An irrigation pump and negative-pressure suction system were connected. Irrigation flow rate was adjusted to 100–200 ml/min. Negative pressure was set at 150–200 mmHg (approximately 0.02–0.027 MPa; 1 mmHg = 0.133 kPa). A 200-µm holmium laser fiber was inserted with the following settings: fragmentation mode 1.2 W, 30 Hz; dusting mode 0.8 W, 30 Hz.

Basket extraction was avoided for stone removal. For lower calyceal stones, basket relocation was selectively used. The sheath position was continuously adjusted to optimize stone clearance. The cloverleaf-shaped negative-pressure port on the TFS-UAS was intermittently occluded when approaching stone fragments to facilitate dust aspiration.For larger fragments entering the sheath, the scope was slowly withdrawn under continuous suction. If aspiration failed, the TFS-UAS was retracted to the renal pelvis outlet. The FURS was then inserted into the lower calyx to relocate residual stones, dusting lithotripsy was performed, and the TFS-UAS was re-guided into the calyx to assist with irrigation-mediated fragment aspiration.

T-UAS group: Based on intraoperative exploration, T-UAS (Specifications: F10-12/F11-13/F12-14; Supplier: Boston Scientific Medical Trading (Shanghai) Co., Ltd., Approval No.: GXZJ20192022305) was advanced over the guidewire to the UPJ or below. The guidewire was then replaced with the same FURS as in the TFS-UAS group, and identical holmium laser power settings were applied for lithotripsy. For stone fragments > 2 mm, basket extraction was preferentially attempted.

Postoperative Protocol: Both groups routinely received double-J stent placement after successful lithotripsy. Follow-up CT urography was performed at 2 weeks postoperatively. Ureteral stents were removed for patients with no residual stones.

Observation indicators

iSFR: The presence of residual stone fragments ≥ 3 mm identified during intraoperative endoscopic inspection of the collecting system is defined as clinically significant residual stone [21].

Residual stone rate: At 2 weeks postoperatively, stone clearance was evaluated via entire urinary tract CT. Residual fragments ≥ 3 mm in maximum diameter were defined as clinically significant residual stones [21].

Operation parameters: Duration (defined as the interval spanning from initial insertion of the rigid ureteroscope into the ureter to final placement of the indwelling urinary catheter upon procedure completion), hematologic changes (leukocytes, Hb, BUN, Cr).

Occurrence of complications: Fever, pain, urinary leakage, perinephric fluid, etc [21].

Hospital stay (Discharge criteria): Patients without postoperative complications are maintained under observation until resolution of gross hematuria, followed by catheter removal and discharge.

Patients with complications are discharged only after complete resolution of the managed complications.

Statistical methods

Statistical analysis was performed using SPSS 23.0 software. Continuous variables with normal distribution were expressed as mean ± standard deviation (SD) and compared using Student’s t-test. Categorical variables were presented as frequency (n, %) and analyzed via Chi-square test. A two-tailed P-value < 0.05 was considered statistically significant.

Results

Clinical outcomes

This study collected data from 196 patients with unilateral renal and upper ureteral calculi. Table 1 shows the baseline characteristics of patients, including 146 males and 50 females aged 20–90 years (age average: 52.0 ± 14.0). The observation group included 62 patients treated with TFS-UAS, while the control group included 134 patients treated with UAS lithotripsy. 69.4% were first-time stone patients, and approximately 5.6% had positive preoperative urine cultures. The most common stone diameter category was 10–20 mm (59.7%), followed by < 10 mm (26.0%) and > 2 0 mm (14.3%). The most commonly used UAS sizes in both T-UAS and TFS-UAS groups were 11/13 Fr (UAS: 72.4%, TFS-UAS: 50%). In this retrospective study, we found that patients in the TFS-UAS group were older on average, with higher female proportion, larger UAS size, larger maximum stone diameter, higher maximum CT value, higher modified STONE score, and a greater proportion of stage II lithotripsy (Table 1. Patient’s preoperative clinical data between the two groups).

Table 1.

Patient’s preoperative clinical data between the two groups

Variables, mean ±SD or n(%)		T-UAS	TFS-UAS	P value
Total number, (n)		134	62
Age(years)		49.72±13.82	56.87±13.28	0.001
BMI(kg/m2)		24.77±3.09	24.57±3.23	0.682
Gender, n(%)	Male	107(79.85)	39(62.90)	0.011
	Female	27(20.15)	23(37.10)
Preoperative urine culture, n(%)	Negative	126(94.03)	59(95.16)	1.000
	Positive	8(5.97)	3(4.84)
Preoperative urine routines, n(%)	Negative	75(55.97)	31(50.00)	0.407
	1+	36(26.87)	15(24.19)
	2+	11(8.21)	10(16.13)
	3+	12(8.96)	6(9.68)
Maximum stone size, cm		12.56±5.14	17.73±7.79	<0.001
Maximum CT value		778.39±513.46	1156.52±420.15	<0.001
the STONE score		7.37±2.28	10.86±2.51	<0.001
Preoperative Double stent, n(%)	YES	24(17.91)	36(58.06)	<0.001
	NO	110(82.09)	26(41.94)

BMI body mass index, SD standard deviation

Analyzing all patients included, no significant differences were found between TFS-UAS and T-UAS groups in preoperative/postoperative Hemoglobin, urea nitrogen, creatinine changes, hospital stay, iSFR, or 2-week postoperative SFR. We found longer operative time in the TFS-UAS group, though not statistically significant (55.23 ± 23.53 min vs. 48.34 ± 22.81 min, P = 0.053). The TFS-UAS group had smaller postoperative WBC elevation, also not statistically significant (1.21 ± 3.15 × 10⁹/L vs. 2.08 ± 3.27 × 10⁹/L, P = 0.079) (Supplementary Table 1). In complication comparisons, the T-UAS group had 3 febrile patients and 5 requiring ketorolac tromethamine for postoperative pain; the TFS-UAS group had 1 febrile and 1 with postoperative pain, with no significant differences. No severe complications like visceral injury, septic shock, or ureteral rupture occurred in either group (Supplementary Table 1).

In the subgroup analysis of stones ≥ 15 mm, 78 eligible patients were included (62 males, 16 females; age 20–82 years old, average age 53.4 ± 14.3). The observation group included 37 TFS-UAS patients, and the control group 41 T-UAS patients. Patients in the TFS-UAS group remained older on average, with larger UAS size and maximum stone diameter, higher maximum CT value, higher modified STONE score, and greater stage II lithotripsy proportion in the TFS-UAS group (Supplementary Table 2). Notably, the TFS-UAS group had significantly shorter operative time compared to UAS (53.92 ± 21.77 min vs. 65.76 ± 22.43 min, P = 0.021), significantly higher 2-week postoperative SFR (P = 0.018), and higher iSFR (though not statistically significant, P = 0.063, Table 2). No significant differences were found in other parameters including preoperative/postoperative hemoglobin, white blood cells, urea nitrogen, creatinine changes, or hospital stay (Table 2. Comparisons of surgical outcomes and postoperative clinical characteristics). In complications, the T-UAS group had 2 febrile patients and 2 requiring ketorolac tromethamine; the TFS-UAS group had 1 febrile and 1 pain patient, with no significant differences (Table 2).

Table 2.

Comparisons of surgical outcomes and postoperative clinical characteristics between the two groups

Variables, mean±SD or n(%)		T-UAS	TFS-UAS	P value
Total number, (n)		41	37
Operative time, (min)		65.76±22.43	53.92±21.77	0.021
UAS size (Fr), n(%)	10/12	4(9.76)	0(0)	<0.001
	11/13	34(82.93)	19(51.35)
	12/14	3(7.32)	18(48.65)
Hemoglobin decrease, (g/L)		2.44±9.39	2.08±8.73	0.862
WBC increase, (*109/L)		2.42±3.05	1.59±3.32	0.258
BUN decrease, (mmol/L)		0.63±1.31	0.64±2.22	0.977
Scr decrease, (umol/L)		(−0.66)±18.17	0.07±16.25	0.851
Hospital stay, (days)		3.27±0.67	3.08±0.43	0.144
Initial SFR (Immediately after surgery)	Yes	30(73.17)	34(91.89)	0.063
	No	11(26.83)	3(8.11)
Total SFR (postoperative 2dweek)	Yes	23(56.10)	30(81.08)	0.018
	No	18(43.90)	7(18.92)
Complications
Fever		2(4.88)	1(2.70)	1.000
Pain		2(4.88)	1(2.70)	1.000

In vitro experiments with TFS-UAS

Bending angle comparison

For simple stone localization, we recommend positioning the endoscope > 4 cm outside the TFS-UAS; the most vulnerable positions are when the endoscope tip is + 2 cm or −2 cm relative to the TFS-UAS tip; during lithotripsy, positioning the endoscope ± 0.5 cm from the TFS-UAS tip drives the maximum bending angle of the sheath and allows better simultaneous lithotripsy and stone aspiration (Supplementary Video 1 A-D).

In vitro lithotripsy and stone aspiration experiments

Sufficient space and water flow facilitate stone aspiration;

Supplementary Video 2 A shows excessive endoscope protrusion beyond the TFS-UAS leading to significant stone displacement during lithotripsy;

Supplementary Video 2B demonstrates difficult simultaneous stone aspiration when the TFS-UAS is not properly positioned, requiring the TFS-UAS to be sufficiently close to the stone for immediate dust aspiration;

Supplementary Video 2 C shows that for large stones, the TFS-UAS must fully cover the stone for effective aspiration;

Supplementary Video 2D shows reduced aspiration efficiency when the endoscope tip aligns with the TFS-UAS edge;

Discussion

The incidence of urolithiasis is increasing annually. According to urological guidelines in China, the US, and Europe, PCNL remains the preferred treatment for upper urinary tract stones > 20 mm. However, PCNL requires establishing a renal parenchymal access tract, especially for non-dilated renal calculi, which demands extensive surgical experience and advanced technical skills from the operator. Additionally, intraoperative/postoperative complications like massive hemorrhage and severe infections may occur, with a longer recovery period [22]. Traditional flexible ureteroscopy for large stones faces bottlenecks including prolonged operative time, “snowstorm” effect impairing visibility, accumulated stone fragments affecting lithotripsy assessment, and postoperative stone fragments potentially forming ureteral steinstrasse. During lithotripsy, renal pelvic/calyceal mucosal and capillary damage causes blood to enter irrigation fluid, blurring the field of view. Blood clots may also obscure larger stone fragments, increasing residual stone risk. Continuous irrigation to maintain visibility, if poorly drained, can elevate IRP. IRP > 30 mmHg sustained over 45 s may lead to systemic absorption of bacterial/toxic irrigation fluid, causing postoperative fever, urosepsis, or septic shock [10]. Prolonged RIRS in a relatively closed renal pelvic environment can also elevate irrigation fluid temperature, causing thermal injury to urothelium [23]. Studies show thermal injury risk inversely correlates with IRP and irrigation flow rate [23]. Thus, reducing IRP or increasing flow rate can mitigate thermal injury.

Negative pressure ureteral access sheath (NP-UAS) is widely used clinically [8, 24–26]. Studies show combining RIRS with NP-UAS allows simultaneous lithotripsy and aspiration. Irrigation fluid refluxes through gaps between the FURS and sheath, with active negative pressure increasing reflux velocity. This maintains visibility, reduces lithotripsy temperature and IRP, improves SFR, and decreases infection/fever risks [8, 24–26]. However, traditional NP-UAS often struggles to pass the UPJ into the renal pelvis/calyces, leading to long turbulent flow paths and reduced aspiration efficiency. RIRS generates great amount powdered/granular fragments, with larger pieces requiring postoperative basket extraction, which is cumbersome and time-consuming. Most fragments rely on spontaneous passage, a lengthy process prone to steinstrasse or re-aggregation [11].

TFS-UAS largly overcomes these limitations [5, 9, 12–20]. In addition to all the feature of T-UAS, TFS-UAS is more advanced during RIRS, for: ① Continuous low renal pressure: The negative pressure handle mimics nephroscope sheath principles. F8.6 disposable FURS with F11/13 sheath achieves ideal scope-sheath ratio (0.75). Combined with central suction (150-200mmHg) and continuous pump irrigation (150–200 mL/min), high flow rates dissipate holmium laser heat, reducing thermal injury [23]. ② Flexible tip design enabling close access to renal pelvis/calyces, especially lower pole stones. Simultaneous water flow and negative pressure aspirate powder through scope-sheath gaps, while larger fragments are extracted during scope withdrawal. Prompt removal of blood/pus improves visibility, reduces clot formation and urosepsis risk, shortens operative time, and enhances stone clearance. ③ Cost reduction: Similar pricing to conventional sheaths avoids extra costs. Reduced basket usage (only for unreachable calyces) lowers hospitalization expenses. Limitations include potential mucosal injury from repeated sheath manipulation requiring relaxed ureters, and temporary pressure reduction/pause during hemorrhage to maintain visibility.

This retrospective study found urologists prefer TFS-UAS + FURS for older patients, females, larger ureteral diameter and double-J stent recipients. Previous studies showed reduced ureteral insertion forces in these demographics, indicating preference for better ureteral conditions [27]. Although the preoperative ureteral stent was not significantly related to improved SFRs [28, 29], a more rigorous study design would control for baseline interventions such as prestenting. Although overall TFS-UAS and T-UAS groups showed no significant differences in operative time or SFRs, TFS-UAS demonstrated superior outcomes for ≥ 15 mm stones: shorter operative time and higher SFRs despite larger, harder, more complex stones. For smaller stones, setup time for TFS-UAS equipment and experienced operators’ ability to compensate T-UAS limitations with high-power laser + basket negated significant differences. In conclusion, TFS-UAS + FURS offers higher SFRs and shorter operative times for ≥ 15 mm upper urinary tract stones.

Operation Best-practice with TFS-UAS + FURS

TFS-UAS differs technically from T-UAS. We concluded the following operation best-practice based on in vitro experiments, our experience, and previous studies:

• ① TFS-UAS requires deeper placement into the renal pelvis compared to T-UAS (typically at/below UPJ). The 5–10 cm longer sheath and protruding inner core allow depth assessment via guidewire manipulation (Video). If initial placement fails, FURS should first visualize the pelvis before sheath adjustment.

• ② The fragile flexible tip and tapered design necessitate avoiding laser damage to maintain outflow/aspiration efficiency.

• ③ Disposable FURS maintains ~ 270° bidirectional bending with 200 μm laser fiber, enabling TFS-UAS to achieve 180° angulation. TFS-UAS reaches most renal calyces without positional adjustments. Passive bending at the sheath tip combined with active FURS bending provides triple articulation for complex anatomies.

• ④ For fragile stones, use TFS-UAS to enclose and aspirate fragments during lithotripsy. For large/hard stones, fragment first then aspirate, reserving powderization for remaining pieces. Keep sheath tip ~ 0.5 cm from calyceal walls during withdrawal. Direct water flow perpendicular to gravity (upward for larger fragments, downward for flakes) to enhance aspiration. Systematically search calyces after fragmenting stones to 2–3 mm, similar to PCNL. Prioritize pelvic/upper calyx fragments first to avoid lower calyx re-accumulation.

• ⑤ Optimal application of a motorized irrigation system is recommended to maintain continuous irrigation. This approach ensures stable flow dynamics and controlled negative pressure, thereby enhancing procedural safety and efficiency. Set minimum negative pressure based on real-time assessment of renal pelvic distension. Determine maximum irrigation pressure according to the degree of pelvicalyceal expansion. Elevated IRP may rapidly lead to severe complications. Inadequate irrigation combined with excessive negative pressure can induce renal pelvic collapse and calyceal neck constriction, significantly compromising procedural maneuverability. The optimal intraoperative state is characterized by a mildly corrugated appearance of the renal pelvic wall under endoscopic visualization. This can be achieved by modulating irrigation flow rate and intermittent suction activation to maintain low IRP, thereby ensuring procedural safety while minimizing risks of sepsis and perinephric hematoma. Despite advancements in IRP regulation, current guidelines recommend limiting FURL duration to < 90 min to mitigate infection risks [4].

• ⑥ Suspend suction during hemorrhage; temporary pressure elevation reduces bleeding while suction exacerbates clot formation.

• ⑦ For lower-pole calyceal stones, the endoscope and sheath should be advanced into the calyx simultaneously to avoid sequential insertion (scope-first followed by sheath advancement). In cases with acute IPA or elongated narrow calyceal necks where sheath-endoscope co-entry is unachievable, and the sheath’s presence restricts endoscope deflection, stone relocation using retrieval baskets becomes necessary. If basket extraction fails, position the TFS-UAS at the lower calyx entrance, insert the FURS to pulverize stones into dust, and utilize irrigation flow to flush particles into the TFS-UAS for aspiration. For deeply inaccessible lower calyces, combine novel actively deflectable negative-pressure sheaths with the passive bending capability of FURS to achieve calyceal access for lithotripsy.

• ⑧ For medullary sponge stones, TFS-UAS + FURS efficiently aspirates intramucosal fragments. PCNL remains preferred for staghorn/hard stones.

Limitations

Retrospective design with potential selection bias, small sample size, lack of standardized outcome criteria and semi-quantitative evaluation of procedural parameters such as surgeon maneuverability, visual clarity, and instrumental stability, short 2-week follow-up without long-term quality of life/complication/recurrence data.

Conclusion

In this study, TFS-UAS + FURS offered shorter operative times and higher immediate/short-term SFR for ≥ 15 mm upper urinary tract stones. While requiring good ureteral conditions and experienced operators to manage sheath positioning and pressure balance, it provides clinical advantages over conventional approaches.

Abbreviations

CT

Computed tomography

FURS

Flexible ureteroscope

IPA

Infundibulopelvic angle

IRP

Intrarenal pressure

iSFR

immediate stone-free rate

NP-UAS

Negative pressure ureteral access sheath

PCNL

Percutaneous nephrolithotomy

RIRS

Retrograde intrarenal surgery

SD

Standard deviation

SFR

Stone-free rates

T-UAS

Traditional ureteral access sheath

TFS-UAS

Tip-flexible suctioning ureteral access sheath

UAS

Ureteral access sheaths

UPJ

Ureteropelvic junction

UTI

Urinary tract infection

Authors’ contributions

Conceptualization, C.C., and D.X.; methodology, T.W., J.Z., and X.Z.; software, X.S., Y.W., and C.M.; validation, T.W., J.Z., and X.Z.; formal analysis, X.S., Y.W., and C.M.; investigation, D.X.; resources, T.W., and C.C.; data curation, D.X.; writing-original draft preparation, T.W., J.Z., and X.Z.; writing-review and editing, C.C., and D.X.; visualization, T.W., and J.Z.; supervision, C.C., and D.X.; project administration, C.C.; funding acquisition, T.W., and D.X. All authors read and approved the final manuscript.

Funding

This study was funded by grants from National Natural Science Foundation of China (82174122), National Natural Science Foundation for Young Scholars of China (82303746), the Health Discipline Leader Program of Shanghai Health Commission(2022XD011), and the Promotion and Optimization Management of Diagnosis and treatment technology in Municipal Hospitals of Shanghai Shenkang Hospital Development Center (SHDC12023113).

Data availability

The data that support the findings of this study are available from the corresponding author upon reasonable request.

Declarations

Ethics approval and consent to participate

This study was approved by the Ethics Committee of Shuguang Hospital Affiliated to Shanghai University of Traditional Chinese Medicine. Written informed consent was obtained from each of the patients or their guardians. The study followed the principles of the Helsinki Declaration.

Consent for publication

All authors provide their consent for publication of the manuscript. All participants gave written informed consent for their personal or clinical details along with any identifying images to be published in this study.

Competing interests

The authors declare no competing interests.