Ureteral Stricture Rates after Ho:YAG vs TFL Ureteroscopic Laser Lithotripsy: A Database Analysis

Ureteral Stricture Rates after Ho:YAG vs TFL Ureteroscopic Laser Lithotripsy: A Database Analysis | 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 Ureteral Stricture Rates after Ho:YAG vs TFL Ureteroscopic Laser Lithotripsy: A Database Analysis Amir Patel, Perry Xu, Ariel Roane, Cora Gibbs, Danit Mechlovich, and 2 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-7787439/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted 7 You are reading this latest preprint version Abstract Purpose The goal of our study is to identify the incidence of ureteral strictures after ureteroscopic laser lithotripsy (ULL) with the TFL compared to the Ho:YAG laser. Methods In a nationally representative de-identified aggregate electronic health record database (Truveta Inc.), we studied subjects ≥ 18 years of age who underwent ULL between 2020 and 2024 with at least 3 months of follow up. Subjects were split into a Ho:YAG and TFL cohort. The incidence of ureteral strictures at 6 months was the primary outcome. Results There were 5,922 subjects in the Ho:YAG cohort and 541 in the TFL cohort. 93.2% of the Ho:YAG cohort underwent ULL with a Moses™ fiber. TFL use approximately doubled the rate of stricture formation compared to the Ho:YAG laser at 6 months (5.7% vs 2.8% (p = < 0.001)). Multivariate analysis controlling for relevant variables found that TFL use had an adjusted relative risk of 2.09 (95% CI 1.41, 3.01) for ureteral stricture formation. When a sub-group of Moses Ho:YAG subjects were evaluated against TFL, the adjusted relative risk remained significant at 2.14 (95% CI 1.45, 3.07). Conclusion This large database analysis found approximately double the rate of ureteral strictures with the TFL compared to the Ho:YAG laser on multivariate analysis. Similar findings are seen in a subgroup analysis comparing Moses Ho:YAG to TFL, with the assumption that this compares lasers with similar power and settings. Ureteroscopy Laser Lithotripsy Thulium Holmium Pathologic Constriction Figures Figure 1 Figure 2 Introduction The use of the Holmium: Yttrium-Aluminum-Garnet (Ho:YAG) laser in urology was first described in 1987[ 1 ]. Its absorption in water and ability to deliver energy through a narrow fiber made it the tool of choice for endoscopic lithotripsy. However, the Ho:YAG does have its shortcomings. The generator relies on an optical cavity and mirrors to produce the laser beam, which make it loud, fragile and inefficient[ 2 ]. The Thulium fiber laser (TFL) was developed to combat some of the inefficiencies of the Ho:YAG laser, with promising early results. However, the two systems do have differences that lead to variations in how energy is delivered. The wavelength of the TFL pulse is 1940nm compared to 2120nm of the Ho:YAG laser. With the peak energy absorption of water at 1910nm, Para et al. calculated that there is 16,000 times the energy absorption over 1mm with the TFL compared to the Ho:YAG laser[ 3 ]. This leads to increased working temperatures which could lead to a greater risk of tissue damage and scar formation[ 4 ]. The goal of our study is to compare the incidence of ureteral strictures (US) after ureteroscopic laser lithotripsy (ULL) with the TFL and Ho:YAG laser using a large nationally representative database. Material and Methodology Population definition and data extraction Clinical data for this study was compiled from the Truveta database. Truveta is a nationally representative de-identified aggregate Electronic Health Record database and consists of medical records from 30 healthcare organizations in the United States. The data was accessed on September 23, 2024. De-identification is attested to through expert determination in accordance with the Health Insurance Portability and Accountability Act (HIPAA) Privacy Rule. This study used only de-identified patient records and therefore did not require Institutional Review Board (IRB) approval. Subjects were included if they had a Ho:YAG or TFL fiber associated with a ULL encounter between 2020 and 2024 and were ≥ 18 years of age. Subjects were excluded if they had a previous US, concurrent PCNL with their procedure, multiple fiber usages in their index procedure or had less than 3 months of follow-up from their index procedure. Demographic data The database allowed for extraction of baseline demographic data including age and gender. Relevant medical history was extracted with the use of International Classification of Disease (ICD)-9/ICD-10 codes and Systematized Nomenclature of Medicine – Clinical Terms (SNOMED-CT) codes. Procedural data and Cohort Creation Laser fibers used for ULL were mapped by their Unique Device Identification (UDI) code assigned by the American Food and Drug Administration. The laser fiber used during each procedure was identified and subjects were split into the Ho:YAG cohort and the TFL cohort. For the Ho:YAG group, we also identified if the fiber used is one that is compatible with the Moses technology. The use of ureteral access sheaths (UAS) was also determined through UDI mapping. Data about the location and laterality of the stone was obtained through ICD-10, Clinical Modification codes, while information about the surgery was obtained through Current Procedural Terminology (CPT), Healthcare Common Procedure Coding System (HCPCS) codes, and/or ICD-10, Procedure Coding System codes. Subjects were determined to be pre-stented if they had a stent placement procedure within 6 weeks of their index procedure. The stent was presumed to be left on a string for self-removal if they lack a CPT code for cystoscopic stent removal following their index procedure. In those that had a stent removal procedure code, we noted the length of time from index procedure to cystoscopic stent removal. Outcomes and statistical analysis Our primary outcome was the incidence of US at 6 months, which was defined using ICD-10 or SNOMED-CT codes indicating US. We also evaluated this at 3, 9 and 12 months. Supplementary document 1 shows a list of the diagnosis and procedure codes tracked. Stricture management events were defined as placement of a stent/percutaneous nephrostomy tube (PCN), endoscopic stricture dilation, reconstruction, or nephrectomy. Binary variables were analyzed with Chi-Square tests of independence with continuity corrections and continuous variables were analyzed with Kruskal-Wallis Rank Sum tests. Univariate and multivariate log-binomial regression were conducted to model the outcome of stricture events within 6 months. Variables and relevant risk factors were selected for the multivariate model based on expert clinical opinion. Relevant risk factors included age, chronic kidney disease, tobacco use, bilateral procedure, prior ULL, UAS use, placement of ureteral stent, stent removal performed at home, and diagnosis of both kidney and ureteral stones. Relative risk of US at 6 months between groups was modeled using log-binomial regression and unadjusted (univariate) and adjusted (multivariate) estimates of relative risk (RR) are given for both the overall cohort and a Moses Ho:YAG fiber subset. P-values of < 0.05 were considered significant. All statistical analyses were performed using R (version 4.4.2, R Foundation for Statistical Computing, Vienna, Austria) Results A total of 9,086 adult subjects were identified. After reviewing exclusion criteria, there were 6,463 subjects remaining: 5,922 in the Ho:YAG arm and 541 in the TFL arm. Supplementary document 2 details the cohort selection process. Table 1 displays information about the patients, divided by laser fiber used. 93.2% of Ho:YAG subjects underwent ULL utilizing a Moses compatible laser fiber. The TFL cohort had a higher rate of radiation exposure (3.7 vs 2.0%), concurrent renal and ureteral stones (38.3 vs 28.1%), and was significantly older (60.6 vs 58.1 years). Meanwhile, a greater proportion of the Ho:YAG cohort were overweight (29.5 vs 20.7%), had prior ULL (27.8 vs 21.8%) and had a stent placed at their index procedure (85.9 vs 76.7%). At 6 months, TFL use doubled the unadjusted risk of US formation compared to the Ho:YAG laser (5.7 vs 2.8%). Prior radiation therapy, UAS use, or concurrent renal and ureteral stone treatment did not impact US outcomes. Figure 1 shows that this holds true at 3, 9 and 12 months post-procedure. The results of the multivariate analysis are shown in Table 2. The adjusted RR for US formation at 6 months was 2.14 (95% CI 1.45, 3.07) with the TFL compared to the Ho:YAG laser. Other significant covariates include: chronic kidney disease, tobacco use, prior ureteroscopy and bilateral procedures. Ureteral stenting and UAS use did not prevent US formation. A sub-group analysis of the TFL cohort compared to Moses Ho:YAG subjects shows similar findings with an adjusted RR of 2.09 (95% CI 1.41, 3.01). Many patients undergo complex management with multiple treatments, with Fig. 2 showing the final treatment noted on the database for each US patient. Overall, the frequency of US treatment did not differ between cohorts (59% Ho:YAG vs 45% TFL (p = 0.160)). Discussion Our findings show that there is an increased risk of US formation when ULL is performed with the TFL compared to Ho:YAG lasers. There are some baseline differences in treatment groups, however the increased risk of US formation persisted after multivariate analysis. Furthermore, when the Ho:YAG cohort was restricted to just Moses subjects, which was utilized as a surrogate for high-power Ho:YAG subjects, the risk of US remained higher in the TFL group. US formation is associated with ULL. Sunaryo et al. showed this in their database analysis looking at over 300,000 subjects that found a US rate of nearly 3% with ULL compared to 1.5% with shockwave lithotripsy alone[ 5 ]. The authors noted a median time from ULL to US diagnosis of 21 days, therefore, subjects that had less than 90 days of follow-up were excluded in our study. TFL gained early traction when numerous studies showed greater stone free rates with the technology[ 6 – 8 ]. However, most studies comparing Ho:YAG to TFL used low powered Ho:YAG lasers and left laser settings up to surgeon discretion[ 9 ]. When comparing similarly powered lasers, the differences in laser efficiency and stone free rates are minimal[ 10 ] − [ 11 ]. Para et al. compared the risk of US formation between TFL and Ho:YAG ULL and found a higher US rate (4.6 vs 1.7%) and longer mean US length (4.4 vs 2.7cm) with the TFL[ 3 ]. Moretto et al. performed a meta-analysis investigating US rates after ULL. They report a 1.9% overall rate of US, but this increased to 2.7% when only looking at studies over the last 5 years, thought to be due to the use of higher power lasers[ 12 ]. A potential reason for the difference in incidence of US formation is the photothermal effect each laser has on water and tissue. Wanderling et al. assessed working temperatures with TFL and Moses Ho:YAG at standardized settings in a hydrogel kidney model and found consistently higher temperatures with the TFL at all settings[ 4 ]. Other groups reported similar findings in studies performed in different models[ 13 – 15 ]. On the contrary, some studies showed no differences. Taratkin et al. attempted to calculate the actual power output of a Ho:YAG laser and a TFL by measuring the temperature rise of water in a controlled system[ 16 ]. Their study showed that at fixed laser settings, the temperature rise is consistently higher with the TFL compared to the Ho:YAG. Overall, most studies show an increased temperature rise with TFL compared to Ho:YAG. This could explain the later US diagnoses in the TFL group, as laparoscopy literature showed that iatrogenic thermal injuries to the ureter typically present in a delayed fashion[ 17 ]. Although UAS use was not found to be protective of US formation in our cohort, prior in-vitro studies show that UAS use and pressurized irrigation should adequately protect the kidney from exposure to dangerously high temperatures[ 18 – 21 ]. With regards to stricture management, May et. al studied subjects with US formation after ureteroscopy and found that the morbidity of such complications is severe; noting that over 50% of subjects require nephrectomy or surgical reconstruction[ 22 ]. Our study showed relatively low rates of treatment and could be due to the use of diagnosis codes rather than procedure codes exclusively. As such, some diagnosed US may be sub-clinical. To combat this, we compared the management of US between groups and did not note significant differences - suggesting that the US in both groups were similar in severity. There are some notable weaknesses in our study. A database does not allow for the precise assessment of relevant clinical factors that contribute to stricture formation, like the presence of stone impaction or ureteral perforation[ 22 ]. Additionally, we only adjusted for variables that were measured within the database and this may not account for additional confounders. We attempted to include as many UDIs for laser fibers as possible, but there may be fibers that were not included or tracked by the database. The differences in baseline characteristics were not adjusted for, and furthermore, the varying sample sizes of the cohorts in both groups may influence our findings. There are also demonstrated strengths to our study. To our knowledge, this is the largest study comparing US risk between the Ho:YAG laser and TFL. The database reflects outcomes from real-world practice throughout the United States. The 93% proportion of Moses use in the Ho:YAG group does appear to be higher than anticipated. However, we believe that this is a strength. Since the exact laser settings and power used in each case is not available to us, the high proportion of Moses fibers are a reasonable surrogate for a high-powered holmium laser since they are used with the Moses Ho:YAG system. Since the average TFL laser allows for higher power and frequencies than low-powered Ho:YAG systems, this may make the groups more balanced. While not a perfect surrogate for controlling the laser settings, it is the best that can be done in a database analysis. Conclusion In this large database analysis, we found double the rate of ureteral strictures at 6 months after TFL laser lithotripsy compared to that with the Ho:YAG laser. This association persisted despite controlling for known risk factors. Similar findings are seen in a subgroup analysis comparing Moses Ho:YAG to TFL, with the assumption that this compares lasers with similar power and settings. A future prospective randomized trial with controlled laser energy settings may allow for a better comparison of these two lasers. Regardless, clinicians should be aware of this potential risk and take the necessary measures to mitigate them. Declarations Competing Interests Ariel Roane, Cora Gibbs, Danit Mechlovich and Laura Stock are employed by Boston Scientific.Dr. Amy Krambeck is a consultant for Boston Scientific, Wolf and Storz. She is a data safety monitoring board member for Uriprene. The other authors have no disclosures. Funding Statement None Author Contribution Amir Patel: Conceptualization, Investigation, Methodology, Resources, Software, Validation, Writing – original draft, Writing – review & editingPerry Xu: Conceptualization, Methodology, Supervision, Validation, Writing – review & editingAriel Roane: Conceptualization, Data curation, Formal analysis, Methodology, Software, Validation, Visualization, Writing – original draftCora Gibbs: Conceptualization, Formal analysis, Project administration, Resources, Supervision, Validation, Writing – review & editingDanit Mechlovich: Conceptualization, Investigation, Methodology, Validation, Writing – review & editingLaura Stock: Data curation, Formal analysis, Investigation, Validation, Writing – review & editingAmy Krambeck: Conceptualization, Investigation, Methodology, Project administration, Supervision, Validation, Writing – review & editing This research is supported by Boston Scientific. Authors’ Disclosure Dr. Amy Krambeck is a consultant for Boston Scientific, Wolf and Storz. She is a data safety monitoring board member for Uriprene. References Dretler, S.P., Watson, G., Parrish, J.A. & Murray, S. Pulsed dye laser fragmentation of ureteral calculi: initial clinical experience. J Urol 137 , 386–389 (1987). Traxer, O. & Keller, E.X. Thulium fiber laser: the new player for kidney stone treatment? A comparison with Holmium:YAG laser. World J Urol 38 , 1883–1894 (2020). Ahmad Para, S. , et al. Incidence of Ureteric strictures Following Ureteroscopic Laser Lithotripsy: Holmium:YAG Versus Thulium Fiber Laser. Urol Res Pract 49 , 198–204 (2023). Wanderling, C. , et al. Getting hot in here! Comparison of Holmium vs. thulium laser in an anatomic hydrogel kidney model. Urolithiasis 52 , 49 (2024). Sunaryo, P.L. , et al. Ureteral Strictures Following Ureteroscopy for Kidney Stone Disease: A Population-based Assessment. J Urol 208 , 1268–1275 (2022). Ulvik, O., MS, A.E., Juliebo-Jones, P., Gjengsto, P. & Beisland, C. Thulium Fibre Laser versus Holmium:YAG for Ureteroscopic Lithotripsy: Outcomes from a Prospective Randomised Clinical Trial. Eur Urol 82 , 73–79 (2022). Uleri, A. , et al. Thulium Fiber Laser Versus Holmium:Yttrium Aluminum Garnet for Lithotripsy: A Systematic Review and Meta-analysis. Eur Urol 85 , 529–540 (2024). Castellani, D. , et al. Comparison Between Holmium:YAG Laser with MOSES Technology vs Thulium Fiber Laser Lithotripsy in Retrograde Intrarenal Surgery for Kidney Stones in Adults: A Propensity Score-matched Analysis From the FLEXible Ureteroscopy Outcomes Registry. J Urol 210 , 323–330 (2023). Sierra, A. , et al. A historical comparison of thulium fiber laser systems for stone lithotripsy: navigating toward safe and effective parameters. World J Urol 42 , 145 (2024). Gupta, K. , et al. Is There a Winner? Prospective Randomized Controlled Trial Comparing SuperPulse Thulium Fiber Laser vs Pulse-Modulated High-Power Holmium:YAG Laser for Retrograde Intrarenal Surgery. J Urol 213 , 274–282 (2025). Chen, R. , et al. Efficacy and safety of thulium fiber laser versus holmium: yttrium-aluminum-garnet laser in lithotripsy for urolithiasis: a systematic review and meta-analysis. Urolithiasis 53 , 33 (2025). Moretto, S. , et al. Ureteral stricture rate after endoscopic treatments for urolithiasis and related risk factors: systematic review and meta-analysis. World J Urol 42 , 234 (2024). Belle, J.D. , et al. Does the Novel Thulium Fiber Laser Have a Higher Risk of Urothelial Thermal Injury than the Conventional Holmium Laser in an In Vitro Study? J Endourol 36 , 1249–1254 (2022). Molina, W.R., Carrera, R.V., Chew, B.H. & Knudsen, B.E. Temperature rise during ureteral laser lithotripsy: comparison of super pulse thulium fiber laser (SPTF) vs high power 120 W holmium-YAG laser (Ho:YAG). World J Urol 39 , 3951–3956 (2021). Denstedt, J. & Gabrigna Berto, F.C. Thulium fiber laser lithotripsy: Is it living up to the hype? Asian J Urol 10 , 289–297 (2023). Taratkin, M. , et al. Temperature changes during laser lithotripsy with Ho:YAG laser and novel Tm-fiber laser: a comparative in-vitro study. World J Urol 38 , 3261–3266 (2020). Cebeci, O.O. Is endourological intervention a suitable treatment option in the management of iatrogenic thermal ureteral injury? A contemporary case series. BMC Urol 22 , 137 (2022). Peteinaris, A. , et al. What is the impact of pulse modulation technology, laser settings and intraoperative irrigation conditions on the irrigation fluid temperature during flexible ureteroscopy? An in vivo experiment using artificial stones. World J Urol 40 , 1853–1858 (2022). Peng, Y. , et al. Safety of a Novel Thulium Fiber Laser for Lithotripsy: An In Vitro Study on the Thermal Effect and Its Impact Factor. J Endourol 34 , 88–92 (2020). Wollin, D.A. , et al. Effect of Laser Settings and Irrigation Rates on Ureteral Temperature During Holmium Laser Lithotripsy, an In Vitro Model. J Endourol 32 , 59–63 (2018). Noureldin, Y.A. , et al. Effects of irrigation parameters and access sheath size on the intra-renal temperature during flexible ureteroscopy with a high-power laser. World J Urol 39 , 1257–1262 (2021). May, P.C. , et al. The Morbidity of Ureteral Strictures in Patients with Prior Ureteroscopic Stone Surgery: Multi-Institutional Outcomes. J Endourol 32 , 309–314 (2018). Additional Declarations Competing interest reported. Ariel Roane, Cora Gibbs, Danit Mechlovich and Laura Stock are employed by Boston Scientific. Dr. Amy Krambeck is a consultant for Boston Scientific, Wolf and Storz. She is a data safety monitoring board member for Uriprene. The other authors have no disclosures. Supplementary Files SupplementaryDocument1.docx SupplementaryDocument2.tif Cite Share Download PDF Status: Under Review Version 1 posted Editorial decision: Revision requested 03 Nov, 2025 Reviews received at journal 26 Oct, 2025 Reviewers agreed at journal 16 Oct, 2025 Reviewers invited by journal 16 Oct, 2025 Editor assigned by journal 08 Oct, 2025 Submission checks completed at journal 08 Oct, 2025 First submitted to journal 05 Oct, 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. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. 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-7787439","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":535224806,"identity":"938fe273-0f64-4f7c-8215-dfdff3dceeab","order_by":0,"name":"Amir Patel","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA4UlEQVRIiWNgGAWjYFACxgYIzc58AEhKyBCtRYKBmS0BRPMQbRdQC48BiEFYC/+0w20ff+6wq+Nn5vn86kaNBQ8D++GjG/CafjuxeTbvmWQJyWbebdY5x4AO40lLu4HXGqAWZsY2ZgmDw7zbjHPYgFokeMzwapEHamH82VYvYX+Y55lxzj8itBgAtTDwth2WMGDmYX6c20aEFkOQw3jPHJeccZjNjDm3T4KHjZBf5G6nP2b8uaOan7+9+fHnnG91cvzsh4/h9z4IQBMAmwSYJKgcSQvzB6JUj4JRMApGwYgDAJxvQmAIgiRuAAAAAElFTkSuQmCC","orcid":"","institution":"Northwestern University","correspondingAuthor":true,"prefix":"","firstName":"Amir","middleName":"","lastName":"Patel","suffix":""},{"id":535224808,"identity":"04f6b3ad-688f-430e-bfbe-c3c2013c7347","order_by":1,"name":"Perry Xu","email":"","orcid":"","institution":"Northwestern University","correspondingAuthor":false,"prefix":"","firstName":"Perry","middleName":"","lastName":"Xu","suffix":""},{"id":535224810,"identity":"8c43b5da-cd0a-4582-bdbc-ea8ad38a566c","order_by":2,"name":"Ariel Roane","email":"","orcid":"","institution":"Boston Scientific (United States)","correspondingAuthor":false,"prefix":"","firstName":"Ariel","middleName":"","lastName":"Roane","suffix":""},{"id":535224812,"identity":"a11cd7fe-e5aa-4553-a381-4134b93acd5d","order_by":3,"name":"Cora Gibbs","email":"","orcid":"","institution":"Boston Scientific (United States)","correspondingAuthor":false,"prefix":"","firstName":"Cora","middleName":"","lastName":"Gibbs","suffix":""},{"id":535224813,"identity":"081c9cef-19ad-4fdf-abfa-5fbe9f0b6ce8","order_by":4,"name":"Danit Mechlovich","email":"","orcid":"","institution":"Boston Scientific (United States)","correspondingAuthor":false,"prefix":"","firstName":"Danit","middleName":"","lastName":"Mechlovich","suffix":""},{"id":535224814,"identity":"c2e64c41-be35-40c4-a5bd-cfba76175249","order_by":5,"name":"Laura Stock","email":"","orcid":"","institution":"Boston Scientific (United States)","correspondingAuthor":false,"prefix":"","firstName":"Laura","middleName":"","lastName":"Stock","suffix":""},{"id":535224815,"identity":"5c91feb4-a44a-48e8-83b0-44d349ca0c90","order_by":6,"name":"Amy Krambeck","email":"","orcid":"","institution":"Northwestern University","correspondingAuthor":false,"prefix":"","firstName":"Amy","middleName":"","lastName":"Krambeck","suffix":""}],"badges":[],"createdAt":"2025-10-06 02:38:06","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-7787439/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-7787439/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":94852689,"identity":"b05fd78e-167a-4e89-909a-82dac873efce","added_by":"auto","created_at":"2025-10-31 11:31:28","extension":"jpg","order_by":0,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":35789,"visible":true,"origin":"","legend":"","description":"","filename":"Fig1.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7787439/v1/056d62c0453ad46fc047daa8.jpg"},{"id":94852693,"identity":"f8be445e-d09c-4039-934b-f10db753c336","added_by":"auto","created_at":"2025-10-31 11:31:28","extension":"docx","order_by":1,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":96141,"visible":true,"origin":"","legend":"","description":"","filename":"ManuscriptFinal.docx","url":"https://assets-eu.researchsquare.com/files/rs-7787439/v1/900d77616cdbe46879708917.docx"},{"id":94985529,"identity":"8581a9ce-d1a6-4da3-acc6-37b573e01080","added_by":"auto","created_at":"2025-11-03 06:58:21","extension":"jpg","order_by":2,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":117579,"visible":true,"origin":"","legend":"","description":"","filename":"Fig2.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7787439/v1/f8389590ca7d552ad3c2f347.jpg"},{"id":94984800,"identity":"31863c86-d29d-44ff-8a1f-4f2c6bea95cf","added_by":"auto","created_at":"2025-11-03 06:56:17","extension":"docx","order_by":3,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":18101,"visible":true,"origin":"","legend":"","description":"","filename":"Table1.docx","url":"https://assets-eu.researchsquare.com/files/rs-7787439/v1/237152be00f7b55dc1c3030b.docx"},{"id":94985537,"identity":"fbca1427-c847-40fc-bd24-a6a7a951e977","added_by":"auto","created_at":"2025-11-03 06:58:21","extension":"docx","order_by":4,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":15469,"visible":true,"origin":"","legend":"","description":"","filename":"Table2.docx","url":"https://assets-eu.researchsquare.com/files/rs-7787439/v1/db2dfeb85e865491496e3b3b.docx"},{"id":94852697,"identity":"f1c46b2c-d175-4dfc-8685-dbfe03eceefb","added_by":"auto","created_at":"2025-10-31 11:31:28","extension":"json","order_by":5,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":8885,"visible":true,"origin":"","legend":"","description":"","filename":"e1ccc0fd3a1543b79e29d5b9f6dbc64d.json","url":"https://assets-eu.researchsquare.com/files/rs-7787439/v1/b4366528b35b80aa14e86196.json"},{"id":94986129,"identity":"37afb3df-dffe-499f-a023-b9e4345bd9e7","added_by":"auto","created_at":"2025-11-03 06:59:51","extension":"docx","order_by":6,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":57956,"visible":true,"origin":"","legend":"","description":"","filename":"SupplementaryDocument1.docx","url":"https://assets-eu.researchsquare.com/files/rs-7787439/v1/264dce7222087c61c95a5c27.docx"},{"id":94986116,"identity":"7b6ca92f-9f5d-4d36-b1ec-701cb331402e","added_by":"auto","created_at":"2025-11-03 06:59:47","extension":"tif","order_by":7,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":467498,"visible":true,"origin":"","legend":"","description":"","filename":"SupplementaryDocument2.tif","url":"https://assets-eu.researchsquare.com/files/rs-7787439/v1/b2b88267156c28ff5b5c5d5a.tif"},{"id":94852708,"identity":"a1a22d34-c5ba-408a-93be-6f541a7dd0ad","added_by":"auto","created_at":"2025-10-31 11:31:28","extension":"xml","order_by":8,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":71500,"visible":true,"origin":"","legend":"","description":"","filename":"e1ccc0fd3a1543b79e29d5b9f6dbc64d1enriched.xml","url":"https://assets-eu.researchsquare.com/files/rs-7787439/v1/38a094d9d9280e1cad32ed5f.xml"},{"id":94852702,"identity":"817a5783-581f-40d1-9dd7-93cdd5d80f02","added_by":"auto","created_at":"2025-10-31 11:31:28","extension":"jpg","order_by":9,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":35789,"visible":true,"origin":"","legend":"","description":"","filename":"Fig1.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7787439/v1/0ad6edf515825ff2184de51c.jpg"},{"id":94852703,"identity":"f54b3ec6-9a86-4ccb-b384-c7b50ed39aca","added_by":"auto","created_at":"2025-10-31 11:31:28","extension":"jpg","order_by":10,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":117579,"visible":true,"origin":"","legend":"","description":"","filename":"Fig2.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7787439/v1/1b9f6fd24e67909825e06445.jpg"},{"id":94852705,"identity":"622a6f2a-75fc-4db5-855a-7b18995ee294","added_by":"auto","created_at":"2025-10-31 11:31:28","extension":"png","order_by":11,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":22774,"visible":true,"origin":"","legend":"","description":"","filename":"OnlineFig1.png","url":"https://assets-eu.researchsquare.com/files/rs-7787439/v1/ba5f93abacd952e1c1e82d07.png"},{"id":94852700,"identity":"08cfdce1-c63b-4b01-9d1b-abdb60680a19","added_by":"auto","created_at":"2025-10-31 11:31:28","extension":"png","order_by":12,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":105977,"visible":true,"origin":"","legend":"","description":"","filename":"OnlineFig2.png","url":"https://assets-eu.researchsquare.com/files/rs-7787439/v1/5fd3fc64321d51d7bd02a84d.png"},{"id":94852704,"identity":"ef1f0e28-c33c-4cb7-8cc2-87740c3cae5d","added_by":"auto","created_at":"2025-10-31 11:31:28","extension":"xml","order_by":13,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":66666,"visible":true,"origin":"","legend":"","description":"","filename":"e1ccc0fd3a1543b79e29d5b9f6dbc64d1structuring.xml","url":"https://assets-eu.researchsquare.com/files/rs-7787439/v1/16f231639cbff874a6097f91.xml"},{"id":94852707,"identity":"a811980e-6e70-46b1-84a9-76ec95fd767e","added_by":"auto","created_at":"2025-10-31 11:31:28","extension":"html","order_by":14,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":76289,"visible":true,"origin":"","legend":"","description":"","filename":"earlyproof.html","url":"https://assets-eu.researchsquare.com/files/rs-7787439/v1/461906391c8c9620fd18c44a.html"},{"id":94852690,"identity":"9c2655e6-daf6-4d2a-9a2a-be5c883abb7f","added_by":"auto","created_at":"2025-10-31 11:31:28","extension":"jpg","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":35789,"visible":true,"origin":"","legend":"\u003cp\u003eSee image above for figure legend\u003c/p\u003e","description":"","filename":"Fig1.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7787439/v1/ff57bdf4c96813696f34f73e.jpg"},{"id":94852692,"identity":"7d84c63e-a909-49d2-ab32-a02e22abd541","added_by":"auto","created_at":"2025-10-31 11:31:28","extension":"jpg","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":117579,"visible":true,"origin":"","legend":"\u003cp\u003eSee image above for figure legend\u003c/p\u003e","description":"","filename":"Fig2.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7787439/v1/b98735b5ddcbcc725ef1d2aa.jpg"},{"id":94990368,"identity":"d28d5a5b-b0b5-4d88-8b6f-0b52045d6be1","added_by":"auto","created_at":"2025-11-03 07:16:38","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":630495,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-7787439/v1/520561b8-a526-42e7-a210-c53e0755cda3.pdf"},{"id":94984906,"identity":"4dbd2f51-1be5-4c27-b5c7-abc861e4221e","added_by":"auto","created_at":"2025-11-03 06:56:53","extension":"docx","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":57956,"visible":true,"origin":"","legend":"","description":"","filename":"SupplementaryDocument1.docx","url":"https://assets-eu.researchsquare.com/files/rs-7787439/v1/88010b0651c0de681c5c9cd3.docx"},{"id":94985088,"identity":"0eb70d98-b23b-4ae0-a726-11fee5b1bc22","added_by":"auto","created_at":"2025-11-03 06:57:24","extension":"tif","order_by":2,"title":"","display":"","copyAsset":false,"role":"supplement","size":467498,"visible":true,"origin":"","legend":"","description":"","filename":"SupplementaryDocument2.tif","url":"https://assets-eu.researchsquare.com/files/rs-7787439/v1/e5c2a8df8b779e1c09084222.tif"}],"financialInterests":"Competing interest reported. Ariel Roane, Cora Gibbs, Danit Mechlovich and Laura Stock are employed by Boston Scientific.\n\nDr. Amy Krambeck is a consultant for Boston Scientific, Wolf and Storz. She is a data safety monitoring board member for Uriprene. \n\nThe other authors have no disclosures.","formattedTitle":"Ureteral Stricture Rates after Ho:YAG vs TFL Ureteroscopic Laser Lithotripsy: A Database Analysis","fulltext":[{"header":"Introduction","content":"\u003cp\u003eThe use of the Holmium: Yttrium-Aluminum-Garnet (Ho:YAG) laser in urology was first described in 1987[\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]. Its absorption in water and ability to deliver energy through a narrow fiber made it the tool of choice for endoscopic lithotripsy. However, the Ho:YAG does have its shortcomings. The generator relies on an optical cavity and mirrors to produce the laser beam, which make it loud, fragile and inefficient[\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eThe Thulium fiber laser (TFL) was developed to combat some of the inefficiencies of the Ho:YAG laser, with promising early results. However, the two systems do have differences that lead to variations in how energy is delivered. The wavelength of the TFL pulse is 1940nm compared to 2120nm of the Ho:YAG laser. With the peak energy absorption of water at 1910nm, Para et al. calculated that there is 16,000 times the energy absorption over 1mm with the TFL compared to the Ho:YAG laser[\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e]. This leads to increased working temperatures which could lead to a greater risk of tissue damage and scar formation[\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eThe goal of our study is to compare the incidence of ureteral strictures (US) after ureteroscopic laser lithotripsy (ULL) with the TFL and Ho:YAG laser using a large nationally representative database.\u003c/p\u003e"},{"header":"Material and Methodology","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e\u003ch2\u003ePopulation definition and data extraction\u003c/h2\u003e\u003cp\u003eClinical data for this study was compiled from the Truveta database. Truveta is a nationally representative de-identified aggregate Electronic Health Record database and consists of medical records from 30 healthcare organizations in the United States. The data was accessed on September 23, 2024. De-identification is attested to through expert determination in accordance with the Health Insurance Portability and Accountability Act (HIPAA) Privacy Rule. This study used only de-identified patient records and therefore did not require Institutional Review Board (IRB) approval.\u003c/p\u003e\u003cp\u003eSubjects were included if they had a Ho:YAG or TFL fiber associated with a ULL encounter between 2020 and 2024 and were \u0026ge;\u0026thinsp;18 years of age. Subjects were excluded if they had a previous US, concurrent PCNL with their procedure, multiple fiber usages in their index procedure or had less than 3 months of follow-up from their index procedure.\u003c/p\u003e\u003c/div\u003e\n\u003ch3\u003eDemographic data\u003c/h3\u003e\n\u003cp\u003eThe database allowed for extraction of baseline demographic data including age and gender. Relevant medical history was extracted with the use of International Classification of Disease (ICD)-9/ICD-10 codes and Systematized Nomenclature of Medicine \u0026ndash; Clinical Terms (SNOMED-CT) codes.\u003c/p\u003e\n\u003ch3\u003eProcedural data and Cohort Creation\u003c/h3\u003e\n\u003cp\u003eLaser fibers used for ULL were mapped by their Unique Device Identification (UDI) code assigned by the American Food and Drug Administration. The laser fiber used during each procedure was identified and subjects were split into the Ho:YAG cohort and the TFL cohort. For the Ho:YAG group, we also identified if the fiber used is one that is compatible with the Moses technology. The use of ureteral access sheaths (UAS) was also determined through UDI mapping.\u003c/p\u003e\u003cp\u003eData about the location and laterality of the stone was obtained through ICD-10, Clinical Modification codes, while information about the surgery was obtained through Current Procedural Terminology (CPT), Healthcare Common Procedure Coding System (HCPCS) codes, and/or ICD-10, Procedure Coding System codes.\u003c/p\u003e\u003cp\u003eSubjects were determined to be pre-stented if they had a stent placement procedure within 6 weeks of their index procedure. The stent was presumed to be left on a string for self-removal if they lack a CPT code for cystoscopic stent removal following their index procedure. In those that had a stent removal procedure code, we noted the length of time from index procedure to cystoscopic stent removal.\u003c/p\u003e\n\u003ch3\u003eOutcomes and statistical analysis\u003c/h3\u003e\n\u003cp\u003eOur primary outcome was the incidence of US at 6 months, which was defined using ICD-10 or SNOMED-CT codes indicating US. We also evaluated this at 3, 9 and 12 months. Supplementary document 1 shows a list of the diagnosis and procedure codes tracked. Stricture management events were defined as placement of a stent/percutaneous nephrostomy tube (PCN), endoscopic stricture dilation, reconstruction, or nephrectomy.\u003c/p\u003e\u003cp\u003eBinary variables were analyzed with Chi-Square tests of independence with continuity corrections and continuous variables were analyzed with Kruskal-Wallis Rank Sum tests. Univariate and multivariate log-binomial regression were conducted to model the outcome of stricture events within 6 months. Variables and relevant risk factors were selected for the multivariate model based on expert clinical opinion. Relevant risk factors included age, chronic kidney disease, tobacco use, bilateral procedure, prior ULL, UAS use, placement of ureteral stent, stent removal performed at home, and diagnosis of both kidney and ureteral stones.\u003c/p\u003e\u003cp\u003eRelative risk of US at 6 months between groups was modeled using log-binomial regression and unadjusted (univariate) and adjusted (multivariate) estimates of relative risk (RR) are given for both the overall cohort and a Moses Ho:YAG fiber subset. P-values of \u0026lt;\u0026thinsp;0.05 were considered significant. All statistical analyses were performed using R (version 4.4.2, R Foundation for Statistical Computing, Vienna, Austria)\u003c/p\u003e"},{"header":"Results","content":"\u003cp\u003eA total of 9,086 adult subjects were identified. After reviewing exclusion criteria, there were 6,463 subjects remaining: 5,922 in the Ho:YAG arm and 541 in the TFL arm. Supplementary document 2 details the cohort selection process.\u003c/p\u003e\u003cp\u003eTable\u0026nbsp;1 displays information about the patients, divided by laser fiber used. 93.2% of Ho:YAG subjects underwent ULL utilizing a Moses compatible laser fiber. The TFL cohort had a higher rate of radiation exposure (3.7 vs 2.0%), concurrent renal and ureteral stones (38.3 vs 28.1%), and was significantly older (60.6 vs 58.1 years). Meanwhile, a greater proportion of the Ho:YAG cohort were overweight (29.5 vs 20.7%), had prior ULL (27.8 vs 21.8%) and had a stent placed at their index procedure (85.9 vs 76.7%).\u003c/p\u003e\u003cp\u003eAt 6 months, TFL use doubled the unadjusted risk of US formation compared to the Ho:YAG laser (5.7 vs 2.8%). Prior radiation therapy, UAS use, or concurrent renal and ureteral stone treatment did not impact US outcomes. Figure\u0026nbsp;1 shows that this holds true at 3, 9 and 12 months post-procedure.\u003c/p\u003e\u003cp\u003eThe results of the multivariate analysis are shown in Table\u0026nbsp;2. The adjusted RR for US formation at 6 months was 2.14 (95% CI 1.45, 3.07) with the TFL compared to the Ho:YAG laser. Other significant covariates include: chronic kidney disease, tobacco use, prior ureteroscopy and bilateral procedures. Ureteral stenting and UAS use did not prevent US formation. A sub-group analysis of the TFL cohort compared to Moses Ho:YAG subjects shows similar findings with an adjusted RR of 2.09 (95% CI 1.41, 3.01).\u003c/p\u003e\u003cp\u003eMany patients undergo complex management with multiple treatments, with Fig.\u0026nbsp;2 showing the final treatment noted on the database for each US patient. Overall, the frequency of US treatment did not differ between cohorts (59% Ho:YAG vs 45% TFL (p\u0026thinsp;=\u0026thinsp;0.160)).\u003c/p\u003e"},{"header":"Discussion","content":"\u003cp\u003eOur findings show that there is an increased risk of US formation when ULL is performed with the TFL compared to Ho:YAG lasers. There are some baseline differences in treatment groups, however the increased risk of US formation persisted after multivariate analysis. Furthermore, when the Ho:YAG cohort was restricted to just Moses subjects, which was utilized as a surrogate for high-power Ho:YAG subjects, the risk of US remained higher in the TFL group.\u003c/p\u003e\u003cp\u003eUS formation is associated with ULL. Sunaryo et al. showed this in their database analysis looking at over 300,000 subjects that found a US rate of nearly 3% with ULL compared to 1.5% with shockwave lithotripsy alone[\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]. The authors noted a median time from ULL to US diagnosis of 21 days, therefore, subjects that had less than 90 days of follow-up were excluded in our study.\u003c/p\u003e\u003cp\u003eTFL gained early traction when numerous studies showed greater stone free rates with the technology[\u003cspan additionalcitationids=\"CR7\" citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e]. However, most studies comparing Ho:YAG to TFL used low powered Ho:YAG lasers and left laser settings up to surgeon discretion[\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e]. When comparing similarly powered lasers, the differences in laser efficiency and stone free rates are minimal[\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e]\u003csup\u003e\u0026minus;\u003c/sup\u003e[\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e].\u003c/p\u003e\u003cp\u003ePara et al. compared the risk of US formation between TFL and Ho:YAG ULL and found a higher US rate (4.6 vs 1.7%) and longer mean US length (4.4 vs 2.7cm) with the TFL[\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e]. Moretto et al. performed a meta-analysis investigating US rates after ULL. They report a 1.9% overall rate of US, but this increased to 2.7% when only looking at studies over the last 5 years, thought to be due to the use of higher power lasers[\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eA potential reason for the difference in incidence of US formation is the photothermal effect each laser has on water and tissue. Wanderling et al. assessed working temperatures with TFL and Moses Ho:YAG at standardized settings in a hydrogel kidney model and found consistently higher temperatures with the TFL at all settings[\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]. Other groups reported similar findings in studies performed in different models[\u003cspan additionalcitationids=\"CR14\" citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eOn the contrary, some studies showed no differences. Taratkin et al. attempted to calculate the actual power output of a Ho:YAG laser and a TFL by measuring the temperature rise of water in a controlled system[\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e]. Their study showed that at fixed laser settings, the temperature rise is consistently higher with the TFL compared to the Ho:YAG.\u003c/p\u003e\u003cp\u003eOverall, most studies show an increased temperature rise with TFL compared to Ho:YAG. This could explain the later US diagnoses in the TFL group, as laparoscopy literature showed that iatrogenic thermal injuries to the ureter typically present in a delayed fashion[\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e]. Although UAS use was not found to be protective of US formation in our cohort, prior in-vitro studies show that UAS use and pressurized irrigation should adequately protect the kidney from exposure to dangerously high temperatures[\u003cspan additionalcitationids=\"CR19 CR20\" citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eWith regards to stricture management, May et. al studied subjects with US formation after ureteroscopy and found that the morbidity of such complications is severe; noting that over 50% of subjects require nephrectomy or surgical reconstruction[\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e]. Our study showed relatively low rates of treatment and could be due to the use of diagnosis codes rather than procedure codes exclusively. As such, some diagnosed US may be sub-clinical. To combat this, we compared the management of US between groups and did not note significant differences - suggesting that the US in both groups were similar in severity.\u003c/p\u003e\u003cp\u003eThere are some notable weaknesses in our study. A database does not allow for the precise assessment of relevant clinical factors that contribute to stricture formation, like the presence of stone impaction or ureteral perforation[\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e]. Additionally, we only adjusted for variables that were measured within the database and this may not account for additional confounders. We attempted to include as many UDIs for laser fibers as possible, but there may be fibers that were not included or tracked by the database. The differences in baseline characteristics were not adjusted for, and furthermore, the varying sample sizes of the cohorts in both groups may influence our findings.\u003c/p\u003e\u003cp\u003eThere are also demonstrated strengths to our study. To our knowledge, this is the largest study comparing US risk between the Ho:YAG laser and TFL. The database reflects outcomes from real-world practice throughout the United States. The 93% proportion of Moses use in the Ho:YAG group does appear to be higher than anticipated. However, we believe that this is a strength. Since the exact laser settings and power used in each case is not available to us, the high proportion of Moses fibers are a reasonable surrogate for a high-powered holmium laser since they are used with the Moses Ho:YAG system. Since the average TFL laser allows for higher power and frequencies than low-powered Ho:YAG systems, this may make the groups more balanced. While not a perfect surrogate for controlling the laser settings, it is the best that can be done in a database analysis.\u003c/p\u003e"},{"header":"Conclusion","content":"\u003cp\u003eIn this large database analysis, we found double the rate of ureteral strictures at 6 months after TFL laser lithotripsy compared to that with the Ho:YAG laser. This association persisted despite controlling for known risk factors. Similar findings are seen in a subgroup analysis comparing Moses Ho:YAG to TFL, with the assumption that this compares lasers with similar power and settings. A future prospective randomized trial with controlled laser energy settings may allow for a better comparison of these two lasers. Regardless, clinicians should be aware of this potential risk and take the necessary measures to mitigate them.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eCompeting Interests\u003c/strong\u003e\u003cp\u003eAriel Roane, Cora Gibbs, Danit Mechlovich and Laura Stock are employed by Boston Scientific.Dr. Amy Krambeck is a consultant for Boston Scientific, Wolf and Storz. She is a data safety monitoring board member for Uriprene. The other authors have no disclosures.\u003c/p\u003e\u003c/p\u003e\u003ch2\u003eFunding Statement\u003c/h2\u003e\u003cp\u003eNone\u003c/p\u003e\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eAmir Patel: Conceptualization, Investigation, Methodology, Resources, Software, Validation, Writing \u0026ndash; original draft, Writing \u0026ndash; review \u0026amp; editingPerry Xu: Conceptualization, Methodology, Supervision, Validation, Writing \u0026ndash; review \u0026amp; editingAriel Roane: Conceptualization, Data curation, Formal analysis, Methodology, Software, Validation, Visualization, Writing \u0026ndash; original draftCora Gibbs: Conceptualization, Formal analysis, Project administration, Resources, Supervision, Validation, Writing \u0026ndash; review \u0026amp; editingDanit Mechlovich: Conceptualization, Investigation, Methodology, Validation, Writing \u0026ndash; review \u0026amp; editingLaura Stock: Data curation, Formal analysis, Investigation, Validation, Writing \u0026ndash; review \u0026amp; editingAmy Krambeck: Conceptualization, Investigation, Methodology, Project administration, Supervision, Validation, Writing \u0026ndash; review \u0026amp; editing\u003c/p\u003e\u003cp\u003eThis research is supported by Boston Scientific.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthors\u0026rsquo; Disclosure\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eDr. Amy Krambeck is a consultant for Boston Scientific, Wolf and Storz. She is a data safety monitoring board member for Uriprene.\u0026nbsp;\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eDretler, S.P., Watson, G., Parrish, J.A. \u0026amp; Murray, S. Pulsed dye laser fragmentation of ureteral calculi: initial clinical experience. \u003cem\u003eJ Urol\u003c/em\u003e \u003cstrong\u003e137\u003c/strong\u003e, 386\u0026ndash;389 (1987).\u003c/li\u003e\n\u003cli\u003eTraxer, O. \u0026amp; Keller, E.X. Thulium fiber laser: the new player for kidney stone treatment? A comparison with Holmium:YAG laser. \u003cem\u003eWorld J Urol\u003c/em\u003e \u003cstrong\u003e38\u003c/strong\u003e, 1883\u0026ndash;1894 (2020).\u003c/li\u003e\n\u003cli\u003eAhmad Para, S.\u003cem\u003e, et al.\u003c/em\u003e Incidence of Ureteric strictures Following Ureteroscopic Laser Lithotripsy: Holmium:YAG Versus Thulium Fiber Laser. \u003cem\u003eUrol Res Pract\u003c/em\u003e \u003cstrong\u003e49\u003c/strong\u003e, 198\u0026ndash;204 (2023).\u003c/li\u003e\n\u003cli\u003eWanderling, C.\u003cem\u003e, et al.\u003c/em\u003e Getting hot in here! Comparison of Holmium vs. thulium laser in an anatomic hydrogel kidney model. \u003cem\u003eUrolithiasis\u003c/em\u003e \u003cstrong\u003e52\u003c/strong\u003e, 49 (2024).\u003c/li\u003e\n\u003cli\u003eSunaryo, P.L.\u003cem\u003e, et al.\u003c/em\u003e Ureteral Strictures Following Ureteroscopy for Kidney Stone Disease: A Population-based Assessment. \u003cem\u003eJ Urol\u003c/em\u003e \u003cstrong\u003e208\u003c/strong\u003e, 1268\u0026ndash;1275 (2022).\u003c/li\u003e\n\u003cli\u003eUlvik, O., MS, A.E., Juliebo-Jones, P., Gjengsto, P. \u0026amp; Beisland, C. Thulium Fibre Laser versus Holmium:YAG for Ureteroscopic Lithotripsy: Outcomes from a Prospective Randomised Clinical Trial. \u003cem\u003eEur Urol\u003c/em\u003e \u003cstrong\u003e82\u003c/strong\u003e, 73\u0026ndash;79 (2022).\u003c/li\u003e\n\u003cli\u003eUleri, A.\u003cem\u003e, et al.\u003c/em\u003e Thulium Fiber Laser Versus Holmium:Yttrium Aluminum Garnet for Lithotripsy: A Systematic Review and Meta-analysis. \u003cem\u003eEur Urol\u003c/em\u003e \u003cstrong\u003e85\u003c/strong\u003e, 529\u0026ndash;540 (2024).\u003c/li\u003e\n\u003cli\u003eCastellani, D.\u003cem\u003e, et al.\u003c/em\u003e Comparison Between Holmium:YAG Laser with MOSES Technology vs Thulium Fiber Laser Lithotripsy in Retrograde Intrarenal Surgery for Kidney Stones in Adults: A Propensity Score-matched Analysis From the FLEXible Ureteroscopy Outcomes Registry. \u003cem\u003eJ Urol\u003c/em\u003e \u003cstrong\u003e210\u003c/strong\u003e, 323\u0026ndash;330 (2023).\u003c/li\u003e\n\u003cli\u003eSierra, A.\u003cem\u003e, et al.\u003c/em\u003e A historical comparison of thulium fiber laser systems for stone lithotripsy: navigating toward safe and effective parameters. \u003cem\u003eWorld J Urol\u003c/em\u003e \u003cstrong\u003e42\u003c/strong\u003e, 145 (2024).\u003c/li\u003e\n\u003cli\u003eGupta, K.\u003cem\u003e, et al.\u003c/em\u003e Is There a Winner? Prospective Randomized Controlled Trial Comparing SuperPulse Thulium Fiber Laser vs Pulse-Modulated High-Power Holmium:YAG Laser for Retrograde Intrarenal Surgery. \u003cem\u003eJ Urol\u003c/em\u003e \u003cstrong\u003e213\u003c/strong\u003e, 274\u0026ndash;282 (2025).\u003c/li\u003e\n\u003cli\u003eChen, R.\u003cem\u003e, et al.\u003c/em\u003e Efficacy and safety of thulium fiber laser versus holmium: yttrium-aluminum-garnet laser in lithotripsy for urolithiasis: a systematic review and meta-analysis. \u003cem\u003eUrolithiasis\u003c/em\u003e \u003cstrong\u003e53\u003c/strong\u003e, 33 (2025).\u003c/li\u003e\n\u003cli\u003eMoretto, S.\u003cem\u003e, et al.\u003c/em\u003e Ureteral stricture rate after endoscopic treatments for urolithiasis and related risk factors: systematic review and meta-analysis. \u003cem\u003eWorld J Urol\u003c/em\u003e \u003cstrong\u003e42\u003c/strong\u003e, 234 (2024).\u003c/li\u003e\n\u003cli\u003eBelle, J.D.\u003cem\u003e, et al.\u003c/em\u003e Does the Novel Thulium Fiber Laser Have a Higher Risk of Urothelial Thermal Injury than the Conventional Holmium Laser in an In Vitro Study? \u003cem\u003eJ Endourol\u003c/em\u003e \u003cstrong\u003e36\u003c/strong\u003e, 1249\u0026ndash;1254 (2022).\u003c/li\u003e\n\u003cli\u003eMolina, W.R., Carrera, R.V., Chew, B.H. \u0026amp; Knudsen, B.E. Temperature rise during ureteral laser lithotripsy: comparison of super pulse thulium fiber laser (SPTF) vs high power 120 W holmium-YAG laser (Ho:YAG). \u003cem\u003eWorld J Urol\u003c/em\u003e \u003cstrong\u003e39\u003c/strong\u003e, 3951\u0026ndash;3956 (2021).\u003c/li\u003e\n\u003cli\u003eDenstedt, J. \u0026amp; Gabrigna Berto, F.C. Thulium fiber laser lithotripsy: Is it living up to the hype? \u003cem\u003eAsian J Urol\u003c/em\u003e \u003cstrong\u003e10\u003c/strong\u003e, 289\u0026ndash;297 (2023).\u003c/li\u003e\n\u003cli\u003eTaratkin, M.\u003cem\u003e, et al.\u003c/em\u003e Temperature changes during laser lithotripsy with Ho:YAG laser and novel Tm-fiber laser: a comparative in-vitro study. \u003cem\u003eWorld J Urol\u003c/em\u003e \u003cstrong\u003e38\u003c/strong\u003e, 3261\u0026ndash;3266 (2020).\u003c/li\u003e\n\u003cli\u003eCebeci, O.O. Is endourological intervention a suitable treatment option in the management of iatrogenic thermal ureteral injury? A contemporary case series. \u003cem\u003eBMC Urol\u003c/em\u003e \u003cstrong\u003e22\u003c/strong\u003e, 137 (2022).\u003c/li\u003e\n\u003cli\u003ePeteinaris, A.\u003cem\u003e, et al.\u003c/em\u003e What is the impact of pulse modulation technology, laser settings and intraoperative irrigation conditions on the irrigation fluid temperature during flexible ureteroscopy? An in vivo experiment using artificial stones. \u003cem\u003eWorld J Urol\u003c/em\u003e \u003cstrong\u003e40\u003c/strong\u003e, 1853\u0026ndash;1858 (2022).\u003c/li\u003e\n\u003cli\u003ePeng, Y.\u003cem\u003e, et al.\u003c/em\u003e Safety of a Novel Thulium Fiber Laser for Lithotripsy: An In Vitro Study on the Thermal Effect and Its Impact Factor. \u003cem\u003eJ Endourol\u003c/em\u003e \u003cstrong\u003e34\u003c/strong\u003e, 88\u0026ndash;92 (2020).\u003c/li\u003e\n\u003cli\u003eWollin, D.A.\u003cem\u003e, et al.\u003c/em\u003e Effect of Laser Settings and Irrigation Rates on Ureteral Temperature During Holmium Laser Lithotripsy, an In Vitro Model. \u003cem\u003eJ Endourol\u003c/em\u003e \u003cstrong\u003e32\u003c/strong\u003e, 59\u0026ndash;63 (2018).\u003c/li\u003e\n\u003cli\u003eNoureldin, Y.A.\u003cem\u003e, et al.\u003c/em\u003e Effects of irrigation parameters and access sheath size on the intra-renal temperature during flexible ureteroscopy with a high-power laser. \u003cem\u003eWorld J Urol\u003c/em\u003e \u003cstrong\u003e39\u003c/strong\u003e, 1257\u0026ndash;1262 (2021).\u003c/li\u003e\n\u003cli\u003eMay, P.C.\u003cem\u003e, et al.\u003c/em\u003e The Morbidity of Ureteral Strictures in Patients with Prior Ureteroscopic Stone Surgery: Multi-Institutional Outcomes. \u003cem\u003eJ Endourol\u003c/em\u003e\u003cstrong\u003e32\u003c/strong\u003e, 309\u0026ndash;314 (2018).\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"world-journal-of-urology","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"wjur","sideBox":"Learn more about [World Journal of Urology](https://link.springer.com/journal/345)","snPcode":"345","submissionUrl":"https://submission.nature.com/new-submission/345/3","title":"World Journal of Urology","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"Ureteroscopy, Laser Lithotripsy, Thulium, Holmium, Pathologic Constriction","lastPublishedDoi":"10.21203/rs.3.rs-7787439/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-7787439/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003ch2\u003ePurpose\u003c/h2\u003e\u003cp\u003eThe goal of our study is to identify the incidence of ureteral strictures after ureteroscopic laser lithotripsy (ULL) with the TFL compared to the Ho:YAG laser.\u003c/p\u003e\u003ch2\u003eMethods\u003c/h2\u003e\u003cp\u003eIn a nationally representative de-identified aggregate electronic health record database (Truveta Inc.), we studied subjects\u0026thinsp;\u0026ge;\u0026thinsp;18 years of age who underwent ULL between 2020 and 2024 with at least 3 months of follow up. Subjects were split into a Ho:YAG and TFL cohort. The incidence of ureteral strictures at 6 months was the primary outcome.\u003c/p\u003e\u003ch2\u003eResults\u003c/h2\u003e\u003cp\u003eThere were 5,922 subjects in the Ho:YAG cohort and 541 in the TFL cohort. 93.2% of the Ho:YAG cohort underwent ULL with a Moses\u0026trade; fiber. TFL use approximately doubled the rate of stricture formation compared to the Ho:YAG laser at 6 months (5.7% vs 2.8% (p\u0026thinsp;=\u0026thinsp;\u0026lt;\u0026thinsp;0.001)). Multivariate analysis controlling for relevant variables found that TFL use had an adjusted relative risk of 2.09 (95% CI 1.41, 3.01) for ureteral stricture formation. When a sub-group of Moses Ho:YAG subjects were evaluated against TFL, the adjusted relative risk remained significant at 2.14 (95% CI 1.45, 3.07).\u003c/p\u003e\u003ch2\u003eConclusion\u003c/h2\u003e\u003cp\u003eThis large database analysis found approximately double the rate of ureteral strictures with the TFL compared to the Ho:YAG laser on multivariate analysis. Similar findings are seen in a subgroup analysis comparing Moses Ho:YAG to TFL, with the assumption that this compares lasers with similar power and settings.\u003c/p\u003e","manuscriptTitle":"Ureteral Stricture Rates after Ho:YAG vs TFL Ureteroscopic Laser Lithotripsy: A Database Analysis","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-10-31 11:31:23","doi":"10.21203/rs.3.rs-7787439/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2025-11-03T15:42:01+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-10-26T04:21:59+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"144008808130096572262004807020472070425","date":"2025-10-17T03:05:31+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2025-10-16T23:54:51+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2025-10-08T16:48:38+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2025-10-08T05:46:29+00:00","index":"","fulltext":""},{"type":"submitted","content":"World Journal of Urology","date":"2025-10-06T02:22:03+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"world-journal-of-urology","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"wjur","sideBox":"Learn more about [World Journal of Urology](https://link.springer.com/journal/345)","snPcode":"345","submissionUrl":"https://submission.nature.com/new-submission/345/3","title":"World Journal of Urology","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"b5fbfacf-d953-4bed-893a-edc1d71672e8","owner":[],"postedDate":"October 31st, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[],"tags":[],"updatedAt":"2026-01-03T15:38:29+00:00","versionOfRecord":[],"versionCreatedAt":"2025-10-31 11:31:23","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-7787439","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-7787439","identity":"rs-7787439","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}