Utilization of Flexible Ureteroscopy in Conjunction with Flexible Vacuum-Assisted Ureteral Access Sheath for the Management of 1-2cm Complex Lower Calyceal Calculi

Utilization of Flexible Ureteroscopy in Conjunction with Flexible Vacuum-Assisted Ureteral Access Sheath for the Management of 1-2cm Complex Lower Calyceal Calculi | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Utilization of Flexible Ureteroscopy in Conjunction with Flexible Vacuum-Assisted Ureteral Access Sheath for the Management of 1-2cm Complex Lower Calyceal Calculi Zengjun Zhu, Wenyu Chi, Chengrong Zhang, Weihui Jia, Guobao Sun This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-6798114/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 19 Nov, 2025 Read the published version in BMC Urology → Version 1 posted 10 You are reading this latest preprint version Abstract Purpose To assess the efficacy and safety of flexible ureteroscopy (FURL) in conjunction with flexible vacuum-assisted ureteral access sheath (FV-UAS) for the treatment of 1–2 cm complex lower calyceal stones, in comparison to conventional FURL. Methods A retrospective analysis was performed on 69 patients with 1–2 cm complex lower calyceal stones treated from July 2023 to February 2025. Patients were categorized into an observation group (n = 36) administered FURL with FV-UAS and a control group (n = 33) administered standard FURL with a conventional ureteral access sheath. All surgeries were conducted by the same proficient surgeon. Preoperative characteristics, stone clearance rates, surgical duration, length of hospital stay, and postoperative complications were compared across groups. Results No notable variations were detected in baseline variables such as age, gender, BMI, stone diameter, and stone density between the two groups (P > 0.05). The stone clearance rate in the observation group was markedly superior to that of the control group (77.8% vs. 51.5%, P = 0.022). The observation group exhibited reduced surgical durations (63.25 ± 8.32 min vs. 74.33 ± 15.61 min, P < 0.001), diminished hospital stays (3.17 ± 0.46 d vs. 5.06 ± 1.42 d, P < 0.001), and decreased incidences of postoperative fever (0% vs. 12.1%, P = 0.031). Conclusions The combination of FURL and a flexible vacuum-assisted ureteral access sheath exhibited enhanced efficacy and safety in the management of 1-2cm complicated lower calyceal stones relative to conventional FURL. This method led to enhanced stone clearance rates, decreased operational durations, shortened hospitalizations, and less postoperative problems, offering a promising new alternative for addressing this difficult stone presentation. Expanded sample sizes and multicenter investigations are necessary to substantiate these results. Flexible ureteroscopy Lower calyceal stones Vacuum-assisted ureteral access sheath Stone clearance Minimally invasive surgery 1. Introduction Complex lower calyceal anatomy denotes differences in the structure of the lower calyx, encompassing calyceal neck stenosis, lengthened calyceal neck, or adverse infundibular angles[ 1 ]. These structural changes correlate with increased residual stone rates post-intervention. While percutaneous nephrolithotomy (PCNL) provides elevated stone clearance rates, it is more intrusive and associated with heightened risks of consequences, including hemorrhage and infection, rendering it more appropriate for kidney stones exceeding 2cm[ 2 , 3 ].Thus,flexible ureteroscopy lithotripsy (FURL) provides benefits in the management of 1-2cm renal calculi[ 3 ]. Nonetheless, conventional FURL depends on the spontaneous transit of stones for fragment clearance, leading to elevated residual stone rates. Moreover, increased intrarenal pressure during the surgery is a recognized risk factor for urosepsis. The flexible vacuum-assisted ureteral access sheath (FV-UAS) possesses a pliable distal end that can adeptly navigate different calyces, actively aspirate stone fragments externally via negative pressure, and concurrently diminish intrarenal pressure, thus mitigating postoperative complications and enhancing surgical efficacy. This offers a novel approach for the management of intricate lower calyceal calculi[ 4 ]. This study compared intraoperative and postoperative parameters between FURL combined with FV-UAS and traditional FURL for the treatment of 1-2cm complex lower calyceal stones to assess the efficacy and safety of the former method. 2. Methods 2.1 Clinical Data We conducted a retrospective analysis of 69 patients who received FURL for 1–2 cm difficult lower calyceal stones at our hospital from July 2023 to February 2025. The observation group consisted of 36 patients (FURL combined with FV-UAS), whereas the control group comprised 33 patients (FURL with standard ureteral access sheath). The inclusion criteria were: (i) preoperative CT diagnosis of 1–2 cm lower calyceal stones; (ii) intraoperative recognition of structural changes in the lower calyx; and (iii) surgeries conducted by the same proficient surgeon. The exclusion criteria comprised: (i) uncontrolled preoperative urinary tract infections; (ii) significant ureteral strictures obstructing successful procedure completion;(iii) severe cardiopulmonary dysfunction contraindicating anesthesia or coagulation disorders; (iv) unforeseen postoperative events unrelated to the procedure (e.g., allergic reactions);and (v) incomplete perioperative clinical data.This research received approval from the Ethics Committee of the Affiliated Hospital of Shandong Second Medical University, and all patients granted informed permission after comprehending the surgical procedure. 2.2 Surgical Methods Patients were positioned in the lithotomy stance under general anesthesia, followed by standard cleaning and draping procedures. An 8.0/9.8F semi-rigid ureteroscope was first inserted into the bladder and subsequently pushed through the ureter with the assistance of a zebra guidewire to the ureteropelvic junction. The ureter length was measured with the guidewire retained in position. Utilizing guidewire assistance, either an FV-UAS (F11/10) or a conventional access sheath was introduced to the ureteropelvic junction, with ureteral dilatation conducted if a stricture was identified. Subsequent to the extraction of the zebra guidewire, a disposable digital flexible ureteroscope (F8.4, Yingxu Life Technology Co., Ltd.) was inserted through the access sheath into the renal pelvis. All calyces were meticulously assessed, and following stone localization, a holmium laser fiber (power 0.8W, frequency 30Hz) was employed to fragment the stone. In the observation group, stone particles were systematically extracted by the FV-UAS utilizing negative pressure aspiration. In the control group, stones were entirely crushed, fragments over 2mm were extracted using a stone basket, and patients were advised to adopt a head-down attitude postoperatively to promote stone passage. Ultimately, after verifying the absence of any residual stones in any calyx, a zebra guidewire was introduced, followed by the insertion of an F4.8 ureteral stent (an F6 ureteral stent was utilized for ureteral strictures for a duration of 1–3 months). Stents were extracted four weeks after the operation. 2.3 Observation Parameters Preoperative parameters included patient demographics (age, sex, body mass index [BMI]) and stone characteristics (diameter [longest axis measured on CT] and CT value). Intraoperative and postoperative parameters included stone clearance rate (defined as clinically insignificant residual fragments < 4mm in diameter on CT without symptoms, infection, or obstruction[ 5 ]), postoperative hospital stay (patients were discharged after gross hematuria disappeared or significantly decreased, or after resolution of fever or urinary tract infection), operative time, and postoperative fever (all patients underwent immediate postoperative blood count, renal function, and urinalysis, with dynamic monitoring in cases of postoperative fever). 2.4 Statistical Method Data analysis was conducted with SPSS 28.0 software. Continuous variables were analyzed between groups utilizing independent sample t-tests and presented as mean ± standard deviation. Chi-square tests were employed to assess categorical data. A P-value of less than 0.05 was deemed statistically significant. 3. Results 3.1 Preoperative Parameters No statistically significant differences were observed between the two groups regarding age, BMI, sex, stone diameter, or CT value (P > 0.05), as shown in Table 1 . Table 1 Comparison of preoperative parameters between the two groups Parameter Observation Group (n = 36) Control Group (n = 33) t/χ 2 value P value Age 47.31 ± 8.42 46.97 ± 11.08 t = 0.142 0.887 BMI 25.21 ± 3.29 26.03 ± 3.35 t=-0.102 0.311 Sex χ 2 = 0.022 0.883 Male 19(52.8) 18(54.5) Female 17(47.2) 15(45.5) Stone diameter (cm) 1.61 ± 0.24 1.69 ± 0.23 t=-1.374 0.174 Stone CT value (HU) 980.92 ± 357.24 930.06 ± 244.45 t = 0.684 0.496 2.2 Intraoperative and Postoperative Parameters The stone clearance rate was significantly higher in the observation group compared to the control group (P < 0.05). The control group had a higher incidence of postoperative fever than the observation group (12.1% vs. 0%, P = 0.031). The operative time was longer in the control group than in the observation group (74.33 ± 15.61min vs. 63.25 ± 8.32min, P < 0.001). The hospital stay was also longer in the control group compared to the observation group (5.06 ± 1.42d vs. 3.17 ± 0.46d, P < 0.001), as shown in Table 2 . Table 2 Comparison of intraoperative and postoperative parameters between the two groups Parameter Observation Group (n = 36) Control Group (n = 33) t/χ 2 value P value Stone clearance rate 28(77.8) 17(51.5) χ 2 = 5.235 0.022 Operative time (min) 63.25 ± 8.32 74.33 ± 15.61 t=-3.723 <0.001 Hospital stay (days) 3.17 ± 0.46 5.06 ± 1.42 t=-7.549 <0.001 Postoperative fever 0(0) 4(12.1) χ 2 = 4.632 0.031 4. Discussion FURL has become one of the primary surgical approaches for treating lower calyceal stones due to its advantages of minimal trauma, reduced bleeding, fewer postoperative complications, and shorter hospital stays. However, the lower calyx, being the lowest point in the renal collecting system, presents challenges for stone fragment clearance through positional therapy, resulting in higher residual stone rates[ 6 ]. Sampaio first described the anatomical structure of the lower calyx in 1992, introducing parameters such as infundibular length, width, height, and infundibulopelvic angle to characterize lower calyceal anatomy[ 7 ]. A retrospective study by Geavlete et al. indicated that a narrow infundibulopelvic angle adversely affects surgical success rates[ 8 ], while Kilicarslan H et al. found that an elongated or stenotic infundibulum negatively impacts both stone fragmentation success and residual stone rates[ 9 ]. Research has shown that traditional FURL for 1-2cm stones requires an average of 1.45 procedures per patient to achieve a 91% stone clearance rate[ 10 ]. Moreover, normal intrarenal pressure typically remains below 30 cmH₂O[ 11 ]. During FURL, continual fluid irrigation is necessary to provide clear sight, hence modifying renal fluid dynamics. The kidney's relatively enclosed anatomical structure can lead to a rapid increase in intrarenal pressure when irrigation flow surpasses the reflux system's compensating capacity. The elevated pressure undermines the physiological barrier function of the renal parenchyma, resulting in irregular lymphatic and venous return, which permits the entry of pathogens and poisons into the circulatory system. These pathological alterations may result in complications such as urosepsis, perinephric fluid accumulations, and postoperative infectious issues, which could escalate to life-threatening diseases including renal capsule rupture or septic shock in severe instances.[ 12 ]. Therefore, traditional FURL for treating 1-2cm lower calyceal stones, particularly complex ones, has certain limitations. Yujun Chen et al. innovatively reported a flexible vacuum-assisted sheath device in the international urological field[ 13 ]. The distal flexible segment of this device facilitates accurate 130° directional adjustment, which, in conjunction with flexible ureteroscope navigation, permits seamless access to specific regions within the renal collecting system. The technical advantages encompass: firstly, the distal end design of the device stabilizes target stones to improve the efficiency of laser lithotripsy while concurrently extracting stone fragments by continuous negative pressure aspiration. The observation group (FURL paired with FV-UAS) exhibited significantly superior postoperative stone clearance rates compared to the control group (conventional FURL), P < 0.05.Secondly, intrarenal pressure can be more effectively regulated by adaptively modifying negative pressure in accordance with calyceal filling status throughout the surgery, hence decreasing postoperative infection rates.The observation group had a markedly reduced postoperative fever rate compared to the control group (P = 0.031). Moreover, clinical research indicates that this novel device decreases FURL operative time by an average of 8.5% (P < 0.05) and enhances the 72-hour stone clearance rate by 22.1% (95%CI 18.3–26.7)[ 14 ]. In our study, the observation group exhibited lower operating times and hospital stays compared to the control group (P < 0.001), thereby conserving surgical time while enhancing patient satisfaction and bed usage. Zhang Z et al. discovered that the combination of FV-UAS and FURL for the treatment of unilateral kidney stones smaller than 2 cm yielded superior immediate and one-month postoperative stone clearance rates compared to conventional FURL, along with benefits of reduced operative time, diminished bleeding, and lower infection rates, corroborating our findings[ 15 ]. A separate study indicated that FV-UAS in conjunction with FURL had much superior surgical outcomes compared to conventional FURL in the management of lower calyceal stones with a cumulative diameter of 2 cm or greater[ 16 ]. Surgeons encounter a learning curve with FV-UAS paired with FURL, mostly due to the necessity of balancing intrarenal pressure control with preserving optimal visibility, which demands substantial surgical expertise and skill. Moreover, intricate lower calyceal calculi markedly elevate surgical complexity, potentially extending operating duration and augmenting complication rates. The flexible vacuum-assisted sheath is a disposable item that increases the economic burden for patients, hence restricting its extensive use. Moreover, although the majority of studies indicate benefits for stones smaller than 2cm, the stone clearance rate, surgical efficacy, and safety for stones exceeding 2cm, particularly complex lower calyceal stones larger than 2cm, necessitate additional validation, suggesting that it cannot supplant conventional PCNL for these instances. This retrospective study, characterized by a limited sample size, possesses specific limitations. Retrospective studies depend on hospital information management systems instead of random sampling, rendering them vulnerable to confounding variables. The limited sample size diminishes statistical power and demographic representativeness, thus resulting in biased outcomes. Moreover, patients' financial circumstances may impact the choice of surgical method, thereby influencing study results. 5. Conclusion In summary, FURL when combined with a flexible vacuum-assisted ureteral access sheath exhibits elevated stone clearance rates and surgical safety in the management of 1-2cm complex lower calyceal stones, facilitating expedited postoperative recovery and reduced hospital durations, thereby offering a novel therapeutic alternative for these calculi. Due to the restricted sample size of this study, additional research with bigger cohorts and multi-center investigations is necessary to assess the efficacy and safety of this approach. Declarations Ethics approval and consent to participate This study was approved by the Ethics Committee of the Affiliated Hospital of Shandong Second Medical University(number:wyfy-2024-ky-461), and all patients provided informed consent after understanding the surgical approach. Consent for publication Not applicable Data availability : Data originates from hospital information system. You can reach out to the individual authors with any additional questions. Ethics statement : Authors contribution : W.C.: Data curation, Formal analysis, Methodology, Visualization, Writing-original draft. Z.Z: Data curation, Formal analysis, Methodology, Writing-review & editing. C.Z.: Data curation, Methodology, Validation, Visualization. W.J.: Validation, Visualization. G.S.: Conceptualization, Data curation, Supervision, Writing-review& editing. Funding: This study was funded by Weifang Science and Technology Bureau. Conflict of interest : The authors have no competing interests to declare. Statement of Non-duplication The manuscript is a unique submission and is not being considered for publication by any other source in any medium, and the manuscript has not been published. Clinical Trial Number Not applicable References Preminger GM, Tiselius HG. Urinary lithiasis: Etiology, epidemiology, and pathogenesis. In: Wein AJ, Kavoussi LR, Partin AW, Peters CA, eds. Campbell-Walsh-Wein Urology. 12th ed. Philadelphia, PA: Elsevier; 2021:chap 50. Geraghty RM, Jones P, Somani BK. Worldwide Trends of Urinary Stone Disease Treatment over the Last Two Decades: A Systematic Review. J Endourol. 2017;31(6):547-556. doi:10.1089/end.2016.0895 European Association of Urology. EAU Guidelines on Urolithiasis. European Association of Urology; 2023:Section 6.3.3. Accessed June 1, 2023. https://uroweb.org/guidelines/urolithiasis Wang DJ, Liang P, Yang TX, Liu YQ, Tang QL, Zhou XZ, Tao RZ. RIRS with FV-UAS vs. MPCNL for 2-3-cm upper urinary tract stones: a prospective study. Urolithiasis. 2024 Feb 10;52(1):31. doi: 10.1007/s00240-024-01539-6. PMID: 38340165. Türk C, Petřík A, Sarica K, et al. EAU guidelines on urolithiasis[J]. European Urology, 2022, 81(3): 234-245 Inoue T, Murota T, Okada S, Hamamoto S, Muguruma K, Kinoshita H, Matsuda T; SMART Study Group. Influence of Pelvicaliceal Anatomy on Stone Clearance After Flexible Ureteroscopy and Holmium Laser Lithotripsy for Large Renal Stones. J Endourol. 2015 Sep;29(9):998-1005. doi: 10.1089/end.2015.0071. Epub 2015 May 15. PMID: 25879676. Sampaio FJ, Aragao AH. Inferior pole collecting system anatomy: its probable role in extracorporeal shock wave lithotripsy. J Urol. 1992 Feb;147(2):322-4. doi: 10.1016/s0022-5347(17)37226-9. PMID: 1732584. Geavlete P, Multescu R, Geavlete B. Influence of pyelocaliceal anatomy on the success of flexible ureteroscopic approach. J Endourol. 2008 Oct;22(10):2235-9. doi: 10.1089/end.2008.9719. PMID: 18937587. Kilicarslan H, Kaynak Y, Kordan Y, Kaygisiz O, Coskun B, Gunseren KO, Kanat FM. Unfavorable anatomical factors influencing the success of retrograde intrarenal surgery for lower pole renal calculi. Urol J. 2015 Apr 29;12(2):2065-8. PMID: 25923149. Geraghty R, Abourmarzouk O, Rai B, Biyani CS, Rukin NJ, Somani BK. Evidence for Ureterorenoscopy and Laser Fragmentation (URSL) for Large Renal Stones in the Modern Era. Curr Urol Rep. 2015 Aug;16(8):54. doi: 10.1007/s11934-015-0529-3. PMID: 26077357. Tokas T, Skolarikos A, Herrmann TRW, Nagele U; Training and Research in Urological Surgery and Technology (T.R.U.S.T.)-Group. Pressure matters 2: intrarenal pressure ranges during upper-tract endourological procedures. World J Urol. 2019 Jan;37(1):133-142. doi: 10.1007/s00345-018-2379-3. Epub 2018 Jun 18. PMID: 29915944. Tokas T, Herrmann TRW, Skolarikos A, Nagele U; 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):125-131. doi: 10.1007/s00345-018-2378-4. Epub 2018 Jun 18. PMID: 29915945. Chen Y, Li C, Gao L, Lin L, Zheng L, Ke L, Chen J, Kuang R. Novel Flexible Vacuum-Assisted Ureteral Access Sheath Can Actively Control Intrarenal Pressure and Obtain a Complete Stone-Free Status. J Endourol. 2022 Sep;36(9):1143-1148. doi: 10.1089/end.2022.0004. Epub 2022 Mar 25. PMID: 35243899. Ding J, Su T, Zhang X, Qian S, Duan L, Huang Y, Chu J, Zhang L, Cao J, Cui X. Omnidirectional (Flexible) Ureteral Access Sheath: Safety, Efficacy, and Initial Experience Report. J Endourol. 2023 Nov;37(11):1184-1190. doi: 10.1089/end.2023.0358. Erratum in: J Endourol. 2023 Dec;37(12):1335. doi: 10.1089/end.2023.0358.correx. PMID: 37725564. Zhang Z, Xie T, Li F, Wang X, Liu F, Jiang B, Zou X, Zhang G, Yuan Y, Xiao R, Wu G, Qian B. Comparison of traditional and novel tip-flexible suctioning ureteral access sheath combined with flexible ureteroscope to treat unilateral renal calculi. World J Urol. 2023 Dec;41(12):3619-3627. doi: 10.1007/s00345-023-04648-w. Epub 2023 Oct 11. PMID: 37821778; PMCID: PMC10693513. Ying Z, Dong H, Li C, Zhang S, Chen Y, Chen M, Peng Y, Gao X. Efficacy analysis of tip-flexible suction access sheath during flexible ureteroscopic lithotripsy for unilateral upper urinary tract calculi. World J Urol. 2024 Nov 5;42(1):626. doi: 10.1007/s00345-024-05325-2. PMID: 39499350. Additional Declarations No competing interests reported. Supplementary Files intraoperativeandpostoperativeparameters.xlsx preoperativeparameters.xlsx Cite Share Download PDF Status: Published Journal Publication published 19 Nov, 2025 Read the published version in BMC Urology → Version 1 posted Editorial decision: Revision requested 08 Aug, 2025 Reviews received at journal 27 Jul, 2025 Reviewers agreed at journal 18 Jul, 2025 Reviews received at journal 16 Jul, 2025 Reviewers agreed at journal 16 Jul, 2025 Reviewers invited by journal 02 Jul, 2025 Editor invited by journal 06 Jun, 2025 Editor assigned by journal 06 Jun, 2025 Submission checks completed at journal 06 Jun, 2025 First submitted to journal 01 Jun, 2025 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-6798114","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":479936771,"identity":"06a9241f-16be-4589-8e97-30b4ca8a8078","order_by":0,"name":"Zengjun Zhu","email":"","orcid":"","institution":"Affiliated Hospital of Shandong Second Medical University","correspondingAuthor":false,"prefix":"","firstName":"Zengjun","middleName":"","lastName":"Zhu","suffix":""},{"id":479936772,"identity":"a7e9c07d-b331-4aef-b1b0-1db3c6805bbf","order_by":1,"name":"Wenyu Chi","email":"","orcid":"","institution":"Affiliated Hospital of Shandong Second Medical University","correspondingAuthor":false,"prefix":"","firstName":"Wenyu","middleName":"","lastName":"Chi","suffix":""},{"id":479936773,"identity":"6f493a0d-f3fb-4d95-8b4d-4887fb38d8c8","order_by":2,"name":"Chengrong Zhang","email":"","orcid":"","institution":"Affiliated Hospital of Shandong Second Medical University","correspondingAuthor":false,"prefix":"","firstName":"Chengrong","middleName":"","lastName":"Zhang","suffix":""},{"id":479936774,"identity":"cc71342d-150b-425a-9d30-643ea28e9f87","order_by":3,"name":"Weihui Jia","email":"","orcid":"","institution":"Weifang People's Hospital","correspondingAuthor":false,"prefix":"","firstName":"Weihui","middleName":"","lastName":"Jia","suffix":""},{"id":479936775,"identity":"4f6520d1-72db-4ada-86bd-6a31bdf5575c","order_by":4,"name":"Guobao Sun","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAAw0lEQVRIiWNgGAWjYFACHsYHif8k5NjY2w8QrYXZ4AObhTEfz5kEorWwSc5gq0icJ+FgQJwG+f61B6R5eCTS2yQYEhh+VGwjrMXgxrsEYx4Jidw26cYDjD1nbhOhReKMQTKPAVCLzIEEZsY2IrTIzzhjcJgnQSKdTSLBgDgtDOd7DBtnHJBIIF6LwQ2+ZIaPDRKGbcBAPkiUX+T7zx7/kdhQJy/f3n7wwY8KYhwmkYBgHyBCPRDwE6luFIyCUTAKRjAAAAJ8O25dEhA+AAAAAElFTkSuQmCC","orcid":"","institution":"Affiliated Hospital of Shandong Second Medical University","correspondingAuthor":true,"prefix":"","firstName":"Guobao","middleName":"","lastName":"Sun","suffix":""}],"badges":[],"createdAt":"2025-06-02 01:38:15","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-6798114/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-6798114/v1","draftVersion":[],"editorialEvents":[{"content":"https://doi.org/10.1186/s12894-025-01987-1","type":"published","date":"2025-11-19T15:57:59+00:00"}],"editorialNote":"","failedWorkflow":false,"files":[{"id":96651325,"identity":"86ba7636-befa-421e-b009-26f7fb37ddb8","added_by":"auto","created_at":"2025-11-24 16:14:19","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":590142,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-6798114/v1/963e8a9b-8a8e-4535-83fd-843478468f25.pdf"},{"id":85949346,"identity":"5c86f2b9-ac7a-484d-a702-6423c9523007","added_by":"auto","created_at":"2025-07-03 13:27:53","extension":"xlsx","order_by":0,"title":"","display":"","copyAsset":false,"role":"supplement","size":12174,"visible":true,"origin":"","legend":"","description":"","filename":"intraoperativeandpostoperativeparameters.xlsx","url":"https://assets-eu.researchsquare.com/files/rs-6798114/v1/7d1dd47779c50778a64f69dd.xlsx"},{"id":85949581,"identity":"a5b25717-18b9-41f3-acd5-95b981f47120","added_by":"auto","created_at":"2025-07-03 13:35:53","extension":"xlsx","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":12783,"visible":true,"origin":"","legend":"","description":"","filename":"preoperativeparameters.xlsx","url":"https://assets-eu.researchsquare.com/files/rs-6798114/v1/c1fce07de8bb4017ae94fcec.xlsx"}],"financialInterests":"No competing interests reported.","formattedTitle":"Utilization of Flexible Ureteroscopy in Conjunction with Flexible Vacuum-Assisted Ureteral Access Sheath for the Management of 1-2cm Complex Lower Calyceal Calculi","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eComplex lower calyceal anatomy denotes differences in the structure of the lower calyx, encompassing calyceal neck stenosis, lengthened calyceal neck, or adverse infundibular angles[\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]. These structural changes correlate with increased residual stone rates post-intervention. While percutaneous nephrolithotomy (PCNL) provides elevated stone clearance rates, it is more intrusive and associated with heightened risks of consequences, including hemorrhage and infection, rendering it more appropriate for kidney stones exceeding 2cm[\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e, \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e].Thus,flexible ureteroscopy lithotripsy (FURL) provides benefits in the management of 1-2cm renal calculi[\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e]. Nonetheless, conventional FURL depends on the spontaneous transit of stones for fragment clearance, leading to elevated residual stone rates. Moreover, increased intrarenal pressure during the surgery is a recognized risk factor for urosepsis.\u003c/p\u003e \u003cp\u003eThe flexible vacuum-assisted ureteral access sheath (FV-UAS) possesses a pliable distal end that can adeptly navigate different calyces, actively aspirate stone fragments externally via negative pressure, and concurrently diminish intrarenal pressure, thus mitigating postoperative complications and enhancing surgical efficacy. This offers a novel approach for the management of intricate lower calyceal calculi[\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]. This study compared intraoperative and postoperative parameters between FURL combined with FV-UAS and traditional FURL for the treatment of 1-2cm complex lower calyceal stones to assess the efficacy and safety of the former method.\u003c/p\u003e"},{"header":"2. Methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003e2.1 Clinical Data\u003c/h2\u003e \u003cp\u003eWe conducted a retrospective analysis of 69 patients who received FURL for 1\u0026ndash;2 cm difficult lower calyceal stones at our hospital from July 2023 to February 2025. The observation group consisted of 36 patients (FURL combined with FV-UAS), whereas the control group comprised 33 patients (FURL with standard ureteral access sheath). The inclusion criteria were: (i) preoperative CT diagnosis of 1\u0026ndash;2 cm lower calyceal stones; (ii) intraoperative recognition of structural changes in the lower calyx; and (iii) surgeries conducted by the same proficient surgeon. The exclusion criteria comprised: (i) uncontrolled preoperative urinary tract infections; (ii) significant ureteral strictures obstructing successful procedure completion;(iii) severe cardiopulmonary dysfunction contraindicating anesthesia or coagulation disorders; (iv) unforeseen postoperative events unrelated to the procedure (e.g., allergic reactions);and (v) incomplete perioperative clinical data.This research received approval from the Ethics Committee of the Affiliated Hospital of Shandong Second Medical University, and all patients granted informed permission after comprehending the surgical procedure.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003e2.2 Surgical Methods\u003c/h2\u003e \u003cp\u003ePatients were positioned in the lithotomy stance under general anesthesia, followed by standard cleaning and draping procedures. An 8.0/9.8F semi-rigid ureteroscope was first inserted into the bladder and subsequently pushed through the ureter with the assistance of a zebra guidewire to the ureteropelvic junction. The ureter length was measured with the guidewire retained in position. Utilizing guidewire assistance, either an FV-UAS (F11/10) or a conventional access sheath was introduced to the ureteropelvic junction, with ureteral dilatation conducted if a stricture was identified. Subsequent to the extraction of the zebra guidewire, a disposable digital flexible ureteroscope (F8.4, Yingxu Life Technology Co., Ltd.) was inserted through the access sheath into the renal pelvis. All calyces were meticulously assessed, and following stone localization, a holmium laser fiber (power 0.8W, frequency 30Hz) was employed to fragment the stone.\u003c/p\u003e \u003cp\u003eIn the observation group, stone particles were systematically extracted by the FV-UAS utilizing negative pressure aspiration. In the control group, stones were entirely crushed, fragments over 2mm were extracted using a stone basket, and patients were advised to adopt a head-down attitude postoperatively to promote stone passage. Ultimately, after verifying the absence of any residual stones in any calyx, a zebra guidewire was introduced, followed by the insertion of an F4.8 ureteral stent (an F6 ureteral stent was utilized for ureteral strictures for a duration of 1\u0026ndash;3 months). Stents were extracted four weeks after the operation.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec5\" class=\"Section2\"\u003e \u003ch2\u003e2.3 Observation Parameters\u003c/h2\u003e \u003cp\u003ePreoperative parameters included patient demographics (age, sex, body mass index [BMI]) and stone characteristics (diameter [longest axis measured on CT] and CT value). Intraoperative and postoperative parameters included stone clearance rate (defined as clinically insignificant residual fragments\u0026thinsp;\u0026lt;\u0026thinsp;4mm in diameter on CT without symptoms, infection, or obstruction[\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]), postoperative hospital stay (patients were discharged after gross hematuria disappeared or significantly decreased, or after resolution of fever or urinary tract infection), operative time, and postoperative fever (all patients underwent immediate postoperative blood count, renal function, and urinalysis, with dynamic monitoring in cases of postoperative fever).\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec6\" class=\"Section2\"\u003e \u003ch2\u003e2.4 Statistical Method\u003c/h2\u003e \u003cp\u003eData analysis was conducted with SPSS 28.0 software. Continuous variables were analyzed between groups utilizing independent sample t-tests and presented as mean\u0026thinsp;\u0026plusmn;\u0026thinsp;standard deviation. Chi-square tests were employed to assess categorical data. A P-value of less than 0.05 was deemed statistically significant.\u003c/p\u003e \u003c/div\u003e"},{"header":"3. Results","content":"\u003cdiv id=\"Sec8\" class=\"Section2\"\u003e \u003ch2\u003e3.1 Preoperative Parameters\u003c/h2\u003e \u003cp\u003eNo statistically significant differences were observed between the two groups regarding age, BMI, sex, stone diameter, or CT value (P\u0026thinsp;\u0026gt;\u0026thinsp;0.05), as shown in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eComparison of preoperative parameters between the two groups\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"5\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eParameter\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eObservation Group (n\u0026thinsp;=\u0026thinsp;36)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eControl Group (n\u0026thinsp;=\u0026thinsp;33)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003et/χ\u003csup\u003e2\u003c/sup\u003e value\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eP value\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAge\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e47.31\u0026thinsp;\u0026plusmn;\u0026thinsp;8.42\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e46.97\u0026thinsp;\u0026plusmn;\u0026thinsp;11.08\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003et\u0026thinsp;=\u0026thinsp;0.142\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.887\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eBMI\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e25.21\u0026thinsp;\u0026plusmn;\u0026thinsp;3.29\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e26.03\u0026thinsp;\u0026plusmn;\u0026thinsp;3.35\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003et=-0.102\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.311\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSex\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eχ\u003csup\u003e2\u003c/sup\u003e\u0026thinsp;=\u0026thinsp;0.022\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.883\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMale\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e19(52.8)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e18(54.5)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eFemale\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e17(47.2)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e15(45.5)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eStone diameter (cm)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1.61\u0026thinsp;\u0026plusmn;\u0026thinsp;0.24\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1.69\u0026thinsp;\u0026plusmn;\u0026thinsp;0.23\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003et=-1.374\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.174\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eStone CT value (HU)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e980.92\u0026thinsp;\u0026plusmn;\u0026thinsp;357.24\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e930.06\u0026thinsp;\u0026plusmn;\u0026thinsp;244.45\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003et\u0026thinsp;=\u0026thinsp;0.684\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.496\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec9\" class=\"Section2\"\u003e \u003ch2\u003e2.2 Intraoperative and Postoperative Parameters\u003c/h2\u003e \u003cp\u003eThe stone clearance rate was significantly higher in the observation group compared to the control group (P\u0026thinsp;\u0026lt;\u0026thinsp;0.05). The control group had a higher incidence of postoperative fever than the observation group (12.1% vs. 0%, P\u0026thinsp;=\u0026thinsp;0.031). The operative time was longer in the control group than in the observation group (74.33\u0026thinsp;\u0026plusmn;\u0026thinsp;15.61min vs. 63.25\u0026thinsp;\u0026plusmn;\u0026thinsp;8.32min, P\u0026thinsp;\u0026lt;\u0026thinsp;0.001). The hospital stay was also longer in the control group compared to the observation group (5.06\u0026thinsp;\u0026plusmn;\u0026thinsp;1.42d vs. 3.17\u0026thinsp;\u0026plusmn;\u0026thinsp;0.46d, P\u0026thinsp;\u0026lt;\u0026thinsp;0.001), as shown in Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eComparison of intraoperative and postoperative parameters between the two groups\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"5\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eParameter\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eObservation Group (n\u0026thinsp;=\u0026thinsp;36)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eControl Group (n\u0026thinsp;=\u0026thinsp;33)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003et/χ\u003csup\u003e2\u003c/sup\u003e value\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eP value\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eStone clearance rate\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e28(77.8)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e17(51.5)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eχ\u003csup\u003e2\u003c/sup\u003e\u0026thinsp;=\u0026thinsp;5.235\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.022\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eOperative time (min)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e63.25\u0026thinsp;\u0026plusmn;\u0026thinsp;8.32\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e74.33\u0026thinsp;\u0026plusmn;\u0026thinsp;15.61\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003et=-3.723\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e\u0026lt;0.001\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eHospital stay (days)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e3.17\u0026thinsp;\u0026plusmn;\u0026thinsp;0.46\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e5.06\u0026thinsp;\u0026plusmn;\u0026thinsp;1.42\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003et=-7.549\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e\u0026lt;0.001\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePostoperative fever\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0(0)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e4(12.1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eχ\u003csup\u003e2\u003c/sup\u003e\u0026thinsp;=\u0026thinsp;4.632\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.031\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e"},{"header":"4. Discussion","content":"\u003cp\u003eFURL has become one of the primary surgical approaches for treating lower calyceal stones due to its advantages of minimal trauma, reduced bleeding, fewer postoperative complications, and shorter hospital stays. However, the lower calyx, being the lowest point in the renal collecting system, presents challenges for stone fragment clearance through positional therapy, resulting in higher residual stone rates[\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]. Sampaio first described the anatomical structure of the lower calyx in 1992, introducing parameters such as infundibular length, width, height, and infundibulopelvic angle to characterize lower calyceal anatomy[\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e]. A retrospective study by Geavlete et al. indicated that a narrow infundibulopelvic angle adversely affects surgical success rates[\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e], while Kilicarslan H et al. found that an elongated or stenotic infundibulum negatively impacts both stone fragmentation success and residual stone rates[\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e]. Research has shown that traditional FURL for 1-2cm stones requires an average of 1.45 procedures per patient to achieve a 91% stone clearance rate[\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eMoreover, normal intrarenal pressure typically remains below 30 cmH₂O[\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e]. During FURL, continual fluid irrigation is necessary to provide clear sight, hence modifying renal fluid dynamics. The kidney's relatively enclosed anatomical structure can lead to a rapid increase in intrarenal pressure when irrigation flow surpasses the reflux system's compensating capacity. The elevated pressure undermines the physiological barrier function of the renal parenchyma, resulting in irregular lymphatic and venous return, which permits the entry of pathogens and poisons into the circulatory system. These pathological alterations may result in complications such as urosepsis, perinephric fluid accumulations, and postoperative infectious issues, which could escalate to life-threatening diseases including renal capsule rupture or septic shock in severe instances.[\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e]. Therefore, traditional FURL for treating 1-2cm lower calyceal stones, particularly complex ones, has certain limitations.\u003c/p\u003e \u003cp\u003eYujun Chen et al. innovatively reported a flexible vacuum-assisted sheath device in the international urological field[\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e]. The distal flexible segment of this device facilitates accurate 130\u0026deg; directional adjustment, which, in conjunction with flexible ureteroscope navigation, permits seamless access to specific regions within the renal collecting system. The technical advantages encompass: firstly, the distal end design of the device stabilizes target stones to improve the efficiency of laser lithotripsy while concurrently extracting stone fragments by continuous negative pressure aspiration. The observation group (FURL paired with FV-UAS) exhibited significantly superior postoperative stone clearance rates compared to the control group (conventional FURL), P\u0026thinsp;\u0026lt;\u0026thinsp;0.05.Secondly, intrarenal pressure can be more effectively regulated by adaptively modifying negative pressure in accordance with calyceal filling status throughout the surgery, hence decreasing postoperative infection rates.The observation group had a markedly reduced postoperative fever rate compared to the control group (P\u0026thinsp;=\u0026thinsp;0.031). Moreover, clinical research indicates that this novel device decreases FURL operative time by an average of 8.5% (P\u0026thinsp;\u0026lt;\u0026thinsp;0.05) and enhances the 72-hour stone clearance rate by 22.1% (95%CI 18.3\u0026ndash;26.7)[\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e]. In our study, the observation group exhibited lower operating times and hospital stays compared to the control group (P\u0026thinsp;\u0026lt;\u0026thinsp;0.001), thereby conserving surgical time while enhancing patient satisfaction and bed usage. Zhang Z et al. discovered that the combination of FV-UAS and FURL for the treatment of unilateral kidney stones smaller than 2 cm yielded superior immediate and one-month postoperative stone clearance rates compared to conventional FURL, along with benefits of reduced operative time, diminished bleeding, and lower infection rates, corroborating our findings[\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e]. A separate study indicated that FV-UAS in conjunction with FURL had much superior surgical outcomes compared to conventional FURL in the management of lower calyceal stones with a cumulative diameter of 2 cm or greater[\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eSurgeons encounter a learning curve with FV-UAS paired with FURL, mostly due to the necessity of balancing intrarenal pressure control with preserving optimal visibility, which demands substantial surgical expertise and skill. Moreover, intricate lower calyceal calculi markedly elevate surgical complexity, potentially extending operating duration and augmenting complication rates. The flexible vacuum-assisted sheath is a disposable item that increases the economic burden for patients, hence restricting its extensive use. Moreover, although the majority of studies indicate benefits for stones smaller than 2cm, the stone clearance rate, surgical efficacy, and safety for stones exceeding 2cm, particularly complex lower calyceal stones larger than 2cm, necessitate additional validation, suggesting that it cannot supplant conventional PCNL for these instances.\u003c/p\u003e \u003cp\u003eThis retrospective study, characterized by a limited sample size, possesses specific limitations. Retrospective studies depend on hospital information management systems instead of random sampling, rendering them vulnerable to confounding variables. The limited sample size diminishes statistical power and demographic representativeness, thus resulting in biased outcomes. Moreover, patients' financial circumstances may impact the choice of surgical method, thereby influencing study results.\u003c/p\u003e"},{"header":"5. Conclusion","content":"\u003cp\u003e In summary, FURL when combined with a flexible vacuum-assisted ureteral access sheath exhibits elevated stone clearance rates and surgical safety in the management of 1-2cm complex lower calyceal stones, facilitating expedited postoperative recovery and reduced hospital durations, thereby offering a novel therapeutic alternative for these calculi. Due to the restricted sample size of this study, additional research with bigger cohorts and multi-center investigations is necessary to assess the efficacy and safety of this approach.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eEthics approval and consent to participate\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis study was approved by the Ethics Committee of the Affiliated Hospital of Shandong Second Medical University(number:wyfy-2024-ky-461), and all patients provided informed consent after understanding the surgical approach.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent for publication\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNot applicable\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eData availability\u003c/strong\u003e:\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eData originates from hospital information system. You can reach out to the individual authors with any additional questions.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eEthics statement\u003c/strong\u003e:\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthors contribution\u003c/strong\u003e:\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eW.C.: Data curation, Formal analysis, Methodology, Visualization, Writing-original draft. Z.Z: Data curation, Formal analysis, Methodology, Writing-review \u0026amp; editing. C.Z.: Data curation, Methodology, Validation, Visualization. W.J.: Validation, Visualization. G.S.: Conceptualization, Data curation, Supervision, Writing-review\u0026amp; editing.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding:\u003c/strong\u003e\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eThis study was funded by Weifang Science and Technology Bureau.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConflict of interest\u003c/strong\u003e:\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eThe authors have no competing interests to declare.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eStatement of Non-duplication\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe manuscript is a unique submission and is not being considered for publication by any other source in any medium, and the manuscript has not been published.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eClinical Trial Number\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNot applicable\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003ePreminger GM, Tiselius HG. Urinary lithiasis: Etiology, epidemiology, and pathogenesis. In: Wein AJ, Kavoussi LR, Partin AW, Peters CA, eds. Campbell-Walsh-Wein Urology. 12th ed. Philadelphia, PA: Elsevier; 2021:chap 50.\u003c/li\u003e\n\u003cli\u003eGeraghty RM, Jones P, Somani BK. Worldwide Trends of Urinary Stone Disease Treatment over the Last Two Decades: A Systematic Review. J Endourol. 2017;31(6):547-556. doi:10.1089/end.2016.0895\u003c/li\u003e\n\u003cli\u003eEuropean Association of Urology. EAU Guidelines on Urolithiasis. European Association of Urology; 2023:Section 6.3.3. Accessed June 1, 2023. https://uroweb.org/guidelines/urolithiasis\u003c/li\u003e\n\u003cli\u003eWang DJ, Liang P, Yang TX, Liu YQ, Tang QL, Zhou XZ, Tao RZ. RIRS with FV-UAS vs. MPCNL for 2-3-cm upper urinary tract stones: a prospective study. Urolithiasis. 2024 Feb 10;52(1):31. doi: 10.1007/s00240-024-01539-6. PMID: 38340165.\u003c/li\u003e\n\u003cli\u003eT\u0026uuml;rk C, Petř\u0026iacute;k A, Sarica K, et al. EAU guidelines on urolithiasis[J]. European Urology, 2022, 81(3): 234-245\u003c/li\u003e\n\u003cli\u003eInoue T, Murota T, Okada S, Hamamoto S, Muguruma K, Kinoshita H, Matsuda T; SMART Study Group. Influence of Pelvicaliceal Anatomy on Stone Clearance After Flexible Ureteroscopy and Holmium Laser Lithotripsy for Large Renal Stones. J Endourol. 2015 Sep;29(9):998-1005. doi: 10.1089/end.2015.0071. Epub 2015 May 15. PMID: 25879676.\u003c/li\u003e\n\u003cli\u003eSampaio FJ, Aragao AH. Inferior pole collecting system anatomy: its probable role in extracorporeal shock wave lithotripsy. J Urol. 1992 Feb;147(2):322-4. doi: 10.1016/s0022-5347(17)37226-9. PMID: 1732584.\u003c/li\u003e\n\u003cli\u003eGeavlete P, Multescu R, Geavlete B. Influence of pyelocaliceal anatomy on the success of flexible ureteroscopic approach. J Endourol. 2008 Oct;22(10):2235-9. doi: 10.1089/end.2008.9719. PMID: 18937587.\u003c/li\u003e\n\u003cli\u003eKilicarslan H, Kaynak Y, Kordan Y, Kaygisiz O, Coskun B, Gunseren KO, Kanat FM. Unfavorable anatomical factors influencing the success of retrograde intrarenal surgery for lower pole renal calculi. Urol J. 2015 Apr 29;12(2):2065-8. PMID: 25923149.\u003c/li\u003e\n\u003cli\u003eGeraghty R, Abourmarzouk O, Rai B, Biyani CS, Rukin NJ, Somani BK. Evidence for Ureterorenoscopy and Laser Fragmentation (URSL) for Large Renal Stones in the Modern Era. Curr Urol Rep. 2015 Aug;16(8):54. doi: 10.1007/s11934-015-0529-3. PMID: 26077357.\u003c/li\u003e\n\u003cli\u003eTokas T, Skolarikos A, Herrmann TRW, Nagele U; Training and Research in Urological Surgery and Technology (T.R.U.S.T.)-Group. Pressure matters 2: intrarenal pressure ranges during upper-tract endourological procedures. World J Urol. 2019 Jan;37(1):133-142. doi: 10.1007/s00345-018-2379-3. Epub 2018 Jun 18. PMID: 29915944.\u003c/li\u003e\n\u003cli\u003eTokas T, Herrmann TRW, Skolarikos A, Nagele U; 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):125-131. doi: 10.1007/s00345-018-2378-4. Epub 2018 Jun 18. PMID: 29915945.\u003c/li\u003e\n\u003cli\u003eChen Y, Li C, Gao L, Lin L, Zheng L, Ke L, Chen J, Kuang R. Novel Flexible Vacuum-Assisted Ureteral Access Sheath Can Actively Control Intrarenal Pressure and Obtain a Complete Stone-Free Status. J Endourol. 2022 Sep;36(9):1143-1148. doi: 10.1089/end.2022.0004. Epub 2022 Mar 25. PMID: 35243899.\u003c/li\u003e\n\u003cli\u003eDing J, Su T, Zhang X, Qian S, Duan L, Huang Y, Chu J, Zhang L, Cao J, Cui X. Omnidirectional (Flexible) Ureteral Access Sheath: Safety, Efficacy, and Initial Experience Report. J Endourol. 2023 Nov;37(11):1184-1190. doi: 10.1089/end.2023.0358. Erratum in: J Endourol. 2023 Dec;37(12):1335. doi: 10.1089/end.2023.0358.correx. PMID: 37725564.\u003c/li\u003e\n\u003cli\u003eZhang Z, Xie T, Li F, Wang X, Liu F, Jiang B, Zou X, Zhang G, Yuan Y, Xiao R, Wu G, Qian B. Comparison of traditional and novel tip-flexible suctioning ureteral access sheath combined with flexible ureteroscope to treat unilateral renal calculi. World J Urol. 2023 Dec;41(12):3619-3627. doi: 10.1007/s00345-023-04648-w. Epub 2023 Oct 11. PMID: 37821778; PMCID: PMC10693513.\u003c/li\u003e\n\u003cli\u003eYing Z, Dong H, Li C, Zhang S, Chen Y, Chen M, Peng Y, Gao X. Efficacy analysis of tip-flexible suction access sheath during flexible ureteroscopic lithotripsy for unilateral upper urinary tract calculi. World J Urol. 2024 Nov 5;42(1):626. doi: 10.1007/s00345-024-05325-2. PMID: 39499350.\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"bmc-urology","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"buro","sideBox":"Learn more about [BMC Urology](http://bmcurol.biomedcentral.com/)","snPcode":"","submissionUrl":"https://www.editorialmanager.com/buro/default.aspx","title":"BMC Urology","twitterHandle":"BMC_series","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"em","reportingPortfolio":"BMC Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"Flexible ureteroscopy, Lower calyceal stones, Vacuum-assisted ureteral access sheath, Stone clearance, Minimally invasive surgery","lastPublishedDoi":"10.21203/rs.3.rs-6798114/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-6798114/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003ch2\u003ePurpose\u003c/h2\u003e \u003cp\u003eTo assess the efficacy and safety of flexible ureteroscopy (FURL) in conjunction with flexible vacuum-assisted ureteral access sheath (FV-UAS) for the treatment of 1\u0026ndash;2 cm complex lower calyceal stones, in comparison to conventional FURL.\u003c/p\u003e\u003ch2\u003eMethods\u003c/h2\u003e \u003cp\u003eA retrospective analysis was performed on 69 patients with 1\u0026ndash;2 cm complex lower calyceal stones treated from July 2023 to February 2025. Patients were categorized into an observation group (n\u0026thinsp;=\u0026thinsp;36) administered FURL with FV-UAS and a control group (n\u0026thinsp;=\u0026thinsp;33) administered standard FURL with a conventional ureteral access sheath. All surgeries were conducted by the same proficient surgeon. Preoperative characteristics, stone clearance rates, surgical duration, length of hospital stay, and postoperative complications were compared across groups.\u003c/p\u003e\u003ch2\u003eResults\u003c/h2\u003e \u003cp\u003eNo notable variations were detected in baseline variables such as age, gender, BMI, stone diameter, and stone density between the two groups (P\u0026thinsp;\u0026gt;\u0026thinsp;0.05). The stone clearance rate in the observation group was markedly superior to that of the control group (77.8% vs. 51.5%, P\u0026thinsp;=\u0026thinsp;0.022). The observation group exhibited reduced surgical durations (63.25\u0026thinsp;\u0026plusmn;\u0026thinsp;8.32 min vs. 74.33\u0026thinsp;\u0026plusmn;\u0026thinsp;15.61 min, P\u0026thinsp;\u0026lt;\u0026thinsp;0.001), diminished hospital stays (3.17\u0026thinsp;\u0026plusmn;\u0026thinsp;0.46 d vs. 5.06\u0026thinsp;\u0026plusmn;\u0026thinsp;1.42 d, P\u0026thinsp;\u0026lt;\u0026thinsp;0.001), and decreased incidences of postoperative fever (0% vs. 12.1%, P\u0026thinsp;=\u0026thinsp;0.031).\u003c/p\u003e\u003ch2\u003eConclusions\u003c/h2\u003e \u003cp\u003eThe combination of FURL and a flexible vacuum-assisted ureteral access sheath exhibited enhanced efficacy and safety in the management of 1-2cm complicated lower calyceal stones relative to conventional FURL. This method led to enhanced stone clearance rates, decreased operational durations, shortened hospitalizations, and less postoperative problems, offering a promising new alternative for addressing this difficult stone presentation. Expanded sample sizes and multicenter investigations are necessary to substantiate these results.\u003c/p\u003e","manuscriptTitle":"Utilization of Flexible Ureteroscopy in Conjunction with Flexible Vacuum-Assisted Ureteral Access Sheath for the Management of 1-2cm Complex Lower Calyceal Calculi","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-07-03 13:27:48","doi":"10.21203/rs.3.rs-6798114/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2025-08-08T04:12:28+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-07-27T13:38:01+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"25246525805452610683747481816965103489","date":"2025-07-18T11:05:25+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-07-16T11:37:16+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"75184151064013977980358428046583486302","date":"2025-07-16T11:04:29+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2025-07-02T06:15:38+00:00","index":"","fulltext":""},{"type":"editorInvited","content":"","date":"2025-06-06T12:05:21+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2025-06-06T07:07:55+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2025-06-06T07:05:37+00:00","index":"","fulltext":""},{"type":"submitted","content":"BMC Urology","date":"2025-06-02T01:29:46+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"bmc-urology","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"buro","sideBox":"Learn more about [BMC Urology](http://bmcurol.biomedcentral.com/)","snPcode":"","submissionUrl":"https://www.editorialmanager.com/buro/default.aspx","title":"BMC Urology","twitterHandle":"BMC_series","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"em","reportingPortfolio":"BMC Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"c1bf7f3c-6163-4781-8a17-422cea2decdd","owner":[],"postedDate":"July 3rd, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[],"tags":[],"updatedAt":"2025-11-24T16:13:38+00:00","versionOfRecord":{"articleIdentity":"rs-6798114","link":"https://doi.org/10.1186/s12894-025-01987-1","journal":{"identity":"bmc-urology","isVorOnly":false,"title":"BMC Urology"},"publishedOn":"2025-11-19 15:57:59","publishedOnDateReadable":"November 19th, 2025"},"versionCreatedAt":"2025-07-03 13:27:48","video":"","vorDoi":"10.1186/s12894-025-01987-1","vorDoiUrl":"https://doi.org/10.1186/s12894-025-01987-1","workflowStages":[]},"version":"v1","identity":"rs-6798114","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-6798114","identity":"rs-6798114","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}