Effects of Rectal Anastomotic Configuration and Circular Stapler Diameter on Postoperative Low Anterior Resection Syndrome: A Comparative Clinical Study

Effects of Rectal Anastomotic Configuration and Circular Stapler Diameter on Postoperative Low Anterior Resection Syndrome: A Comparative Clinical Study | 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 Effects of Rectal Anastomotic Configuration and Circular Stapler Diameter on Postoperative Low Anterior Resection Syndrome: A Comparative Clinical Study Omer Kubat, Enes Aksu, Gökhan Uludağ, İmdat Eroğlu, Aybala Turan, and 8 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-8960506/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted 9 You are reading this latest preprint version Abstract Background Low Anterior Resection Syndrome (LARS) is a major determinant of long-term anorectal dysfunction after sphincter-preserving rectal cancer surgery. The mechanical properties of the anastomosis—including its configuration and circular stapler diameter—may influence neorectal compliance, sensory function, and postoperative evacuation dynamics. This study aimed to define the independent contributions of anastomotic configuration and stapler diameter to LARS development. Methods A retrospective cohort of 446 patients who underwent total mesorectal excision (TME) and low anterior resection between 2015 and 2023 was reviewed. A total of 309 patients who had at least 18 months of functional follow-up and validated LARS assessment were included. All anastomoses were created using double-row circular staplers, in either end-to-end or side-to-end configuration. Stapler diameter (28–29 mm vs 31–33 mm), anastomotic level, neoadjuvant treatment protocol, tumour morphology, and total dissected lymph node count were recorded systematically. Functional outcomes were assessed with the validated LARS score. Independent predictors of LARS were identified using backward stepwise multivariable logistic regression. Results The overall LARS incidence was 28.5%. In the end-to-end subgroup, age (OR 1.096) and metastatic lymph node count (OR 1.221) were independent predictors of LARS. In the side-to-end subgroup, a larger stapler diameter (31–33 mm) markedly increased LARS risk (OR 6.910), while age remained an independent determinant (OR 1.055). In the full cohort, advanced age (OR 1.063), long-course neoadjuvant radiotherapy (OR 2.248), and larger stapler diameter (OR 2.395) were independently associated with LARS. Conclusion Anastomotic configuration was not independently associated with postoperative LARS development, whereas larger stapler diameter was significantly and independently associated with an increased risk of LARS, particularly in side-to-end anastomoses. Advanced age and long-course neoadjuvant radiotherapy were also consistently associated with impaired long-term functional recovery. These findings underscore the importance of meticulous intraoperative stapler selection and individualised surgical planning, as technical decisions may have measurable long-term effects on anorectal function. Figures Figure 1 Introduction Rectal cancer accounts for approximately one-third of all colorectal malignancies and remains a major cause of morbidity worldwide despite improving survival rates [ 1 ]. Standardisation of TME and wider implementation of neoadjuvant chemoradiotherapy protocols have improved local disease control and expanded eligibility for sphincter-preserving surgery [ 2 – 4 ]. As a result, although the need for permanent stoma has decreased, the functional outcomes of surgical treatment have become central in contemporary clinical practice. With increasing use of sphincter-preserving procedures, postoperative defaecatory dysfunction after low anterior resection has been increasingly recognised and conceptualised as Low Anterior Resection Syndrome (LARS) [ 5 ]. LARS is characterised by multidimensional symptoms—urgency, clustering, faecal and flatus incontinence, increased stool frequency, and social restriction—that may substantially impair quality of life. Reduced rectal reservoir capacity, pelvic autonomic nerve injury, low anastomosis, and neoadjuvant radiotherapy are accepted as key determinants of LARS development [ 5 – 8 ]. In this context, as LARS has become a critical functional endpoint in rectal cancer surgery, the role of modifiable factors—particularly anastomotic configuration and circular stapler diameter—has gained increasing attention. Anastomotic technique plays an important role in shaping functional outcomes after sphincter-preserving surgery. End-to-end and side-to-end colorectal anastomoses are both widely used in clinical practice and provide comparable anatomical continuity; however, they may differ in their effects on neorectal reservoir function and intrapelvic pressure distribution [ 9 – 11 ]. Therefore, clarifying the impact of anastomotic configuration on LARS is central to efforts aimed at functional optimisation. Advances in circular stapler technology have enabled safe and reproducible anastomosis [ 9 , 12 ]. Nonetheless, stapler diameter and mechanical properties may also influence functional recovery [ 13 – 15 ]. Stapler size may affect anastomotic tension, luminal calibre, and the physiological adaptation of the distal colon, thereby contributing to LARS [ 8 ]. Although larger staplers are theoretically expected to provide a wider anastomosis, evidence suggests they may also increase tissue strain and impair sensorimotor function [ 8 , 16 ]. Defining this relationship has direct clinical relevance for intraoperative decision-making. Accordingly, this study aimed to evaluate the independent effects of anastomotic configuration (end-to-end vs side-to-end) and circular stapler diameter on LARS development, and to characterise the relationship between these technical variables and postoperative functional outcomes. Materials and Methods Study design and population This observational retrospective cohort study evaluated the effects of anastomosis type and circular stapler diameter on LARS development in patients undergoing surgery for rectal cancer. Data from 446 patients who underwent low anterior resection between 2015 and 2023 were obtained from the hospital information system. Electronic medical records, operative notes, pathology reports, and outpatient follow-up data were reviewed. All patients were evaluated for postoperative functional outcomes. Demographic, clinical, and surgical factors potentially associated with LARS were recorded. This retrospective study was approved by the Gazi University Ethics Committee (Approval No. 2024 − 1291) and was conducted in accordance with the Declaration of Helsinki. The requirement for written informed consent was waived due to the retrospective nature of the study. Functional assessment Functional outcomes were assessed using the validated LARS score, which objectively classifies post-LAR bowel dysfunction [ 5 ]. Patients meeting eligibility criteria completed the LARS questionnaire, and total scores were calculated according to the validated scoring system. Inclusion and exclusion criteria Inclusion criteria: Histologically confirmed rectal cancer or precancerous rectal lesions Tumour localisation within the first 15 cm from the anal verge confirmed by rectoscopy and pelvic MRI Age ≥ 18 years Agreement to complete the LARS questionnaire and provide written informed consent Exclusion criteria: Benign disease (e.g., rectovaginal fistula, colovesical fistula) ASA score > 3 Recurrent disease Tumour invasion from other primary organ malignancies Previous Hartmann resection Concomitant major organ resections (e.g., transverse colectomy, right colectomy) Anastomotic leak Anastomotic stricture Metastatic disease Hand-sewn anastomosis For all patients, the following were recorded in detail: primary surgical approach, anastomosis type (end-to-end or side-to-end), stapler diameter, neoadjuvant chemoradiotherapy, tumour localisation, pathological stage, and early postoperative complications. Data collection process A total of 309 patients fulfilled study criteria and underwent long-term functional assessment. All had at least 18 months of follow-up. The LARS questionnaire was administered either by telephone interview or face-to-face during outpatient follow-up. LARS categories were defined as: 0–20: No LARS 21–29: Minor LARS 30–42: Major LARS LARS Questionnaire and Scoring System [5] Question Response Score 1. Do you ever have episodes of uncontrolled flatus? No, never 0 Yes, less than once per week 4 Yes, more than once per week 7 2. Do you ever have accidental leakage of liquid stool? No, never 0 Yes, less than once per week 3 Yes, more than once per week 3 3. Bowel movement frequency per day More than 7 times/day 4 4–7 times/day 2 1–3 times/day 0 Less than once/day 5 4. Do you need to open your bowels again within 1 hour (clustering)? No, never 0 Yes, less than once per week 9 Yes, more than once per week 11 5. Do you experience urgency? No, never 0 Yes, less than once per week 11 Yes, more than once per week 16 Tumour localisation Tumour localisation was classified using pelvic MRI and/or rectoscopy according to distance from the anal verge: Lower rectum: 0–5 cm Mid rectum: 5–10 cm Upper rectum: 10–15 cm All included cases had tumour localisation within 15 cm of the anal verge. Radiotherapy protocol Short-course RT: 25 Gy total, 5 fractions (5 Gy × 5), over 5 consecutive days. Long-course RT: 45–50.4 Gy total, 25–28 fractions (1.8–2 Gy/day), over 5–6 weeks; concurrent chemotherapy when indicated. Surgical technique and study variables All procedures were performed by surgeons with at least 5 years of experience, following TME principles. Anastomoses were classified as end-to-end or side-to-end colorectal anastomosis. Stapler diameters (28, 29, 31, 33 mm) were extracted from operative records. Additional variables included neoadjuvant/adjuvant chemoradiotherapy, tumour distance from anal verge, pathological stage, and total/metastatic lymph node counts. Statistical analysis Analyses were performed using SPSS (IBM SPSS Statistics 27). Frequency tables and descriptive statistics were used for data summarisation. Parametric methods were used for normally distributed continuous variables; comparisons among ≥ 3 independent groups used ANOVA. Non-parametric methods were used for non-normally distributed variables; comparisons among ≥ 3 independent groups used Kruskal–Wallis H tests. Associations between categorical variables were assessed with Pearson chi-square tests. Risk factors for LARS positivity were analysed with binary logistic regression (Backward LR model). Results From 446 patients who underwent low anterior resection during the study period, 309 met inclusion criteria and had at least 18 months of functional follow-up. Of these, 60.5% (n = 187) were male. Mean age was 62.11 ± 12.07 years (median 63; range 24–101). ASA class distribution was 14.2% (n = 44) for ASA 1, 52.5% (n = 162) for ASA 2, and 33.3% (n = 103) for ASA 3. Anastomosis type was end-to-end in 125 patients (40.5%) and side-to-end in 184 patients (59.5%) (Table 1). According to LARS score, 71.5% (n = 221) had no LARS, 12.0% (n = 37) had minor LARS, and 16.5% (n = 51) had major LARS; overall LARS positivity (minor + major) was 28.5%. Mean LARS score was 14.48 ± 13.07 (median 10; range 0–42). Mean tumour diameter was 3.12 ± 2.21 cm, mean total dissected lymph node count was 22.97 ± 13.94, and mean metastatic lymph node count was 1.46 ± 3.67(Table 2). Factors associated with LARS in the full cohort Across the entire cohort, no significant associations were observed between LARS categories and sex, anastomosis type (end-to-end vs side-to-end), pathological diagnosis, diverting stoma, adjuvant chemotherapy, general CT/RT classification, or RT dose (p > 0.05, Table 9). However, ASA score, stapler diameter, tumour localisation, and neoadjuvant radiotherapy were significantly associated with LARS. LARS frequency increased with increasing ASA score (p < 0.001). While ASA 2 was most common in patients without LARS (56.6%), ASA 3 proportions increased to 45.9% in minor LARS and 54.9% in major LARS groups. Circular stapler diameter was also significantly associated with LARS (chi-square = 10.827; p = 0.004): 28–29 mm staplers were used in 79.2% of patients without LARS, whereas 31–33 mm staplers were more frequent in minor and major LARS groups (35.1% and 41.2%, respectively). Tumour localisation differed significantly across LARS categories (p = 0.048). In the major LARS group, proximal tumour localisation reached 56.9%, higher than in no-LARS and minor-LARS groups. Neoadjuvant RT also differed significantly (p = 0.041): long-course RT was more common in LARS-positive patients than in those without LARS (no LARS: 56.6%; minor: 73.0%; major: 64.7%). Among quantitative variables, age and tumour size were associated with LARS. Patients without LARS were significantly younger than both minor and major LARS groups (p < 0.001) (Table 10). For tumour size, the significant difference was between minor and major LARS groups, with larger tumours in major LARS (p = 0.030). Total and metastatic lymph node counts did not differ significantly among LARS categories (p > 0.05). In backward LR multivariable logistic regression for overall LARS positivity (minor + major), independent predictors were age, long-course neoadjuvant radiotherapy, and circular stapler diameter: Age: OR 1.063 (95% CI 1.036–1.089; p < 0.001, Table 11) Long-course neoadjuvant RT vs no RT: OR 2.248 (95% CI 1.228–4.115; p = 0.009) Stapler diameter 31–33 mm vs 28–29 mm: OR 2.395 (95% CI 1.398–4.103; p = 0.001) These findings indicate that advanced age, long-course neoadjuvant RT, and larger stapler diameter are independently and clinically meaningful predictors of LARS after sphincter-preserving rectal cancer surgery. Patients with end-to-end anastomosis Among 125 patients with end-to-end anastomosis, 85 (68.0%) had no LARS, 15 (12.0%) had minor LARS, and 25 (20.0%) had major LARS. No significant associations were found between LARS categories and sex, stapler diameter group (28–29 mm vs 31–33 mm), chemoradiotherapy classification, pathological diagnosis, stoma status, adjuvant chemotherapy, neoadjuvant RT, or RT dose (p > 0.05, Table 3), indicating comparable distribution across groups. In contrast, ASA score was significantly associated with LARS (p = 0.016). ASA 2 predominated in no-LARS patients (48.2%), whereas ASA 3 increased to 66.7% in minor LARS and 56.0% in major LARS groups. Tumour localisation was also associated with LARS (p = 0.038): tumours were more often in the mid rectum among no-LARS patients, distal in minor LARS, and proximal in major LARS. For quantitative variables, only age differed significantly among LARS groups (p < 0.001, Table 4). Bonferroni-corrected pairwise analyses showed that patients without LARS were significantly younger than both minor and major LARS groups. No significant differences were found for total lymph node count, metastatic lymph node count, tumour size, or stapler diameter (p > 0.05). In backward LR multivariable logistic regression for LARS positivity (minor + major) in the end-to-end subgroup, only age and metastatic lymph node count remained independent predictors: Age: OR 1.096 (95% CI 1.048–1.146; p < 0.001, Table 5) Metastatic lymph node count: OR 1.221 (95% CI 1.015–1.468; p = 0.034) Each one-year increase in age and each additional metastatic lymph node were associated with a significant increase in LARS risk. Patients with side-to-end anastomosis Among 184 patients with side-to-end anastomosis, 136 (73.9%) had no LARS, 22 (12.0%) had minor LARS, and 26 (14.1%) had major LARS (Table 6). In this subgroup, no significant differences were observed between LARS categories in sex, pathological diagnosis, diverting stoma, adjuvant chemotherapy, overall CT/RT classification, neoadjuvant RT, or RT dose (p > 0.05). ASA score was significantly associated with LARS (chi-square = 12.260; p = 0.016). ASA 2 predominated in no-LARS and minor-LARS groups (61.8% and 50.0%, respectively), whereas ASA 3 rose to 53.8% in major LARS. Tumour localisation was also significant (chi-square = 10.509; p = 0.033): proximal localisation was more frequent in no-LARS and major-LARS groups (44.1% and 57.7%), whereas mid-rectal localisation predominated in minor LARS (54.5%). In this subgroup, circular stapler diameter emerged as a strong discriminating factor (p < 0.001). While 92.6% of no-LARS patients received 28–29 mm staplers, the proportion of 31–33 mm stapler use was 36.4% in minor LARS and 34.6% in major LARS. Therefore, larger stapler use was significantly more frequent in LARS-positive patients. Among quantitative variables, age was the only factor associated with LARS (p = 0.018, Table 7). Post-hoc analyses indicated that the major LARS group was significantly older than the no-LARS group. Total lymph node count, metastatic lymph node count, and tumour size showed no significant differences (p > 0.05). In backward LR multivariable logistic regression for LARS positivity in the side-to-end subgroup, independent predictors were age and circular stapler diameter: Age: OR 1.055 (95% CI 1.019–1.092; p = 0.003, Table 8) Stapler diameter 31–33 mm vs 28–29 mm: OR 6.910 (95% CI 2.882–16.565; p < 0.001) Thus, in side-to-end anastomosis, larger stapler diameter was associated with nearly a sevenfold increase in LARS risk. Discussion This study systematically evaluated associations between LARS—one of the most important indicators of postoperative bowel dysfunction after sphincter-preserving rectal cancer surgery—and surgical/oncological variables in a relatively large cohort. Overall LARS positivity (minor + major) was 28.5%, and major LARS prevalence was 16.5%. Compared with previously reported LARS prevalence (often 30–60%), these findings still represent a clinically meaningful long-term functional burden, particularly for major LARS [ 5 , 17 ]. The results reinforce the need to integrate long-term anorectal function into treatment planning alongside oncological outcomes. No significant difference in LARS development was found between end-to-end and side-to-end anastomoses. The lack of independent predictive value of anastomotic type in either whole-cohort or subgroup analyses may suggest that modern TME practice has reduced technique-related functional disparities [ 18 , 19 ]. Standardised TME and careful preservation of pelvic autonomic nerves may attenuate the clinical impact of anastomotic geometry. Although some studies suggest that side-to-end anastomosis may improve reservoir function and continence [ 6 , 20 ], this theoretical advantage is not consistently reflected in patient-reported functional scores. Our findings support the view that LARS is driven more strongly by factors such as anastomotic level, associated treatments, and patient characteristics than by configuration alone. One of the most notable findings was the strong association between circular stapler diameter and LARS. In the side-to-end subgroup, use of a 31–33 mm stapler was associated with an almost sevenfold increase in LARS positivity compared with 28–29 mm staplers. In the full-cohort multivariable model, larger stapler diameter remained an independent predictor with approximately 2.4-fold increased risk. Although larger staplers are theoretically expected to reduce obstruction by providing a wider lumen, they may increase mechanical strain at the anal canal and neorectal level, with potential micro-level injury to sphincter and perianastomotic neural structures [ 8 , 15 , 16 ]. This biomechanical mechanism may contribute to dominant LARS symptoms such as urgency and clustering. Nevertheless, despite the strong observed association, causality should be confirmed in prospective studies with detailed physiological and functional evaluation. Clinically, these data indicate that stapler diameter should be considered not only for technical feasibility and lumen patency but also for long-term function. Advanced age was independently and consistently associated with LARS across both anastomotic subgroups and the full cohort. Logistic models showed that each additional year of age was associated with a significant increase in LARS risk. While some studies have linked younger age and male sex to higher LARS risk—possibly due to higher functional expectations, symptom awareness, and social impact [ 17 , 21 , 22 ]—ageing-related physiological changes may also impair postoperative functional recovery: reduced pelvic floor tone, slower autonomic/somatic neural conduction, disordered colonic motility, and higher comorbidity burden. Despite heterogeneity in the literature [ 21 – 23 ], our findings support advanced age as a clinically important risk factor that should be incorporated into preoperative counselling and surgical planning. Long-course neoadjuvant radiotherapy was another key independent predictor in multivariable analysis, associated with approximately 2.2-fold increased LARS risk. This aligns with recognised effects of radiotherapy on anorectal physiology, including reduced rectal compliance, mucosal/submucosal fibrosis, reduced sensory receptor density, and altered internal sphincter tone [ 8 , 11 , 17 , 24 , 25 ]. These mechanisms may particularly drive major LARS components such as urgency, clustering, and incontinence. Our results underline the need to balance oncological benefits and functional costs of neoadjuvant treatment through multidisciplinary, patient-specific decision-making. The significant association between higher ASA score and LARS in both subgroup and whole-cohort analyses suggests that patients with limited systemic reserve and heavier comorbidity burden may have poorer functional recovery [ 23 ]. Surgical stress response, limited mobilisation, and cardiometabolic comorbidities may indirectly impair bowel motility and pelvic floor function. Tumour localisation was also associated with major LARS, with higher rates in proximally located tumours in this dataset—a finding that may reflect a more complex interaction than the classical expectation of higher LARS in distal disease [ 6 , 11 , 23 , 25 ]. Potential contributors include more intensive neoadjuvant strategies, broader resections, or differences in anastomotic level. Clarification requires future studies with standardised millimetric anastomotic height measurements. In the end-to-end subgroup, metastatic lymph node count independently predicted LARS positivity, suggesting a possible link between higher disease burden and functional morbidity. Likewise, the larger tumour size observed in major LARS (vs minor LARS) in the full cohort suggests that extent of resection may contribute to dysfunction. However, as these variables were not consistently independent across all models, their effects should be interpreted cautiously in light of potential confounding factors (e.g., intensified neoadjuvant therapy, more extensive dissection, lower anastomosis, longer operating time) [ 25 ]. This study has several strengths. First, it is among the limited studies assessing the relationship between circular stapler diameter and postoperative functional morbidity after sphincter-preserving rectal cancer surgery in a relatively large cohort, with separate analyses for end-to-end and side-to-end subgroups. Secondly, standardised TME-based surgery by experienced surgeons reduced operative heterogeneity, enabling clearer assessment of technical variables. Thirdly, multivariable evaluation of numerous clinical and oncological factors with backward logistic regression improved statistical robustness. Finally, functional assessment after at least 18 months allowed evaluation of long-term, persistent dysfunction rather than only early postoperative changes. Limitations should also be acknowledged. The retrospective design carries unavoidable risks of selection and information bias. Administration of LARS scoring by telephone or face-to-face interview may introduce response-mode variability. Lack of fully standardised objective recording of anastomotic height (e.g., intraoperative measurement or postoperative imaging) limited finer analysis of neorectal length–function relationships. Preoperative anorectal function, baseline continence status, and pelvic floor dysfunction were not systematically documented and may have acted as uncontrolled confounders. Stapler selection was surgeon-dependent, introducing potential performance bias. In addition, more granular radiotherapy parameters (e.g., dose distribution, field design, RT technique) were unavailable, restricting deeper exploration of RT–LARS relationships. Taken together, these findings indicate that modifiable factors—particularly circular stapler diameter and neoadjuvant radiotherapy intensity—significantly influence LARS risk, while patient-level factors such as advanced age and higher ASA score also remain clinically important. In sphincter-preserving rectal cancer surgery, technical choices and treatment strategies should therefore be evaluated not only through oncological endpoints but also through the lens of long-term anorectal function. Future prospective, ideally randomised studies with detailed functional profiling are needed to optimise stapler selection and neoadjuvant strategies. Conclusion This retrospective cohort study provides a detailed characterisation of factors associated with LARS after sphincter-preserving surgery for rectal cancer. LARS appears to be a multidimensional postoperative outcome influenced not only by anatomical factors but also by surgical technique, radiotherapy regimen, patient-related characteristics, and tumour-related variables. Future prospective, preferably randomised studies with long-term follow-up are required to define more precisely the functional impact of stapler diameter and neoadjuvant treatment strategies and to strengthen evidence-based clinical decision-making. Declarations Patient consent Written informed consent was obtained from the patient for publication. Conflicts of interest The authors declare no competing interests. Ethical approval Ethical approval was granted by the university ethical review board. Funding This research received no specific grant from any funding agency. Author Contribution Ö.K., E.A., G.U., A.T., I.E., A.Y. and S.A. conceived and designed the study, and analysed and interpreted the data. Ö.K.,Ç.B., K.D., H.B., O.Y. and S.L. conducted the literature review and critically appraised the relevant literature. Ö.K., Ç.B., H.G., H.B., O.Y. and S.L. provided scientific and technical support and critically revised the manuscript for important intellectual content. All authors read and approved the final manuscript. References Siegel, R.L., et al., Cancer Statistics, 2021 . CA Cancer J Clin, 2021. 71(1): p. 7–33. Boublikova, L., et al., Total neoadjuvant therapy in rectal cancer: the evidence and expectations . Crit Rev Oncol Hematol, 2023. 192: p. 104196. Nocera, F., et al., Optimising functional outcomes in rectal cancer surgery . Langenbecks Arch Surg, 2021. 406(2): p. 233–250. 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Filips, A., et al., LARS is Associated with Lower Anastomoses, but not with the Transanal Approach in Patients Undergoing Rectal Cancer Resection . World Journal of Surgery, 2021. 45(3): p. 873–879. Hernandez, M.C., P. Wong, and K. Melstrom, Low anterior resection syndrome . J Surg Oncol, 2023. 127(8): p. 1271–1276. Dulskas, A., et al., Long-term bowel dysfunction following low anterior resection . Sci Rep, 2020. 10(1): p. 11882. Tables Tables 1 to 11 are available in the Supplementary Files section. Additional Declarations No competing interests reported. Supplementary Files larstables.docx Cite Share Download PDF Status: Under Review Version 1 posted Editorial decision: Revision requested 23 Apr, 2026 Reviews received at journal 20 Apr, 2026 Reviews received at journal 18 Apr, 2026 Reviewers agreed at journal 27 Mar, 2026 Reviewers agreed at journal 27 Mar, 2026 Reviewers invited by journal 27 Mar, 2026 Editor assigned by journal 20 Mar, 2026 Submission checks completed at journal 27 Feb, 2026 First submitted to journal 24 Feb, 2026 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. 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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-8960506","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":614162349,"identity":"cda3633f-0ae4-4068-8862-38d958f7b7a4","order_by":0,"name":"Omer Kubat","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA2ElEQVRIiWNgGAWjYDACHjYGZhDFz94ApAwsiNZiICPZcwCkRYJ4LTYGNxJAXCK08PMcS5MuqPnDY3Dz+dUNPwokGPjbuxPwapHsbTsmPeOYAY/k7Zyymz1Ah0mcObsBrxaD8+xt0jxsBjx8t3PSbvAAtRhI5BKj5Z8BD8PNM2k3/xCl5SzQYbxtBjwCN9iP3SbKFsmeY8nWM/uMeSR7cthuyxhI8BD0Cz9PmuHtgm9y9vzsx5/dfPPHRo6/vRe/FiTAYwAmiVUOAuwPSFE9CkbBKBgFIwgAAC/fQh/oLnHtAAAAAElFTkSuQmCC","orcid":"","institution":"Ankara Training and Research Hospital","correspondingAuthor":true,"prefix":"","firstName":"Omer","middleName":"","lastName":"Kubat","suffix":""},{"id":614162350,"identity":"ff4ec7e4-13d5-4fa3-b5c2-21ce9c173b47","order_by":1,"name":"Enes Aksu","email":"","orcid":"","institution":"Gazi Hastanesi","correspondingAuthor":false,"prefix":"","firstName":"Enes","middleName":"","lastName":"Aksu","suffix":""},{"id":614162351,"identity":"a89d60ac-ce38-46aa-8ea6-779c2adaf756","order_by":2,"name":"Gökhan Uludağ","email":"","orcid":"","institution":"Gazi Hastanesi","correspondingAuthor":false,"prefix":"","firstName":"Gökhan","middleName":"","lastName":"Uludağ","suffix":""},{"id":614162352,"identity":"dfc940da-6114-426a-8781-808fe890d4d5","order_by":3,"name":"İmdat Eroğlu","email":"","orcid":"","institution":"Gazi Hastanesi","correspondingAuthor":false,"prefix":"","firstName":"İmdat","middleName":"","lastName":"Eroğlu","suffix":""},{"id":614162353,"identity":"c7a90fb0-d979-4078-953e-2ac78849a297","order_by":4,"name":"Aybala Turan","email":"","orcid":"","institution":"Gülhane Training and Research Hospital","correspondingAuthor":false,"prefix":"","firstName":"Aybala","middleName":"","lastName":"Turan","suffix":""},{"id":614162354,"identity":"b706237c-bbe8-4074-9edf-1f1b3a13f6fd","order_by":5,"name":"Saygın Altıner","email":"","orcid":"","institution":"Gazi Hastanesi","correspondingAuthor":false,"prefix":"","firstName":"Saygın","middleName":"","lastName":"Altıner","suffix":""},{"id":614162356,"identity":"214dfb84-64c2-4fc5-8738-cccc968a9b7e","order_by":6,"name":"Çağrı Büyükkasap","email":"","orcid":"","institution":"Gazi Hastanesi","correspondingAuthor":false,"prefix":"","firstName":"Çağrı","middleName":"","lastName":"Büyükkasap","suffix":""},{"id":614162358,"identity":"e23b033b-26cd-4b42-8584-b54f95800956","order_by":7,"name":"Aydın Yavuz","email":"","orcid":"","institution":"Gazi Hastanesi","correspondingAuthor":false,"prefix":"","firstName":"Aydın","middleName":"","lastName":"Yavuz","suffix":""},{"id":614162360,"identity":"b98354cb-5427-497a-b627-3cb3a3339c14","order_by":8,"name":"Hüseyin Göbüt","email":"","orcid":"","institution":"Gazi Hastanesi","correspondingAuthor":false,"prefix":"","firstName":"Hüseyin","middleName":"","lastName":"Göbüt","suffix":""},{"id":614162362,"identity":"6d4a7530-090c-4142-9608-b64b8f823685","order_by":9,"name":"Kürşat Dikmen","email":"","orcid":"","institution":"Gazi Hastanesi","correspondingAuthor":false,"prefix":"","firstName":"Kürşat","middleName":"","lastName":"Dikmen","suffix":""},{"id":614162363,"identity":"956f2657-8f52-4119-a7fc-2ef530dad349","order_by":10,"name":"Hasan Bostancı","email":"","orcid":"","institution":"Gazi Hastanesi","correspondingAuthor":false,"prefix":"","firstName":"Hasan","middleName":"","lastName":"Bostancı","suffix":""},{"id":614162364,"identity":"9415461a-95f3-4510-9b7a-50968319d489","order_by":11,"name":"Osman Yüksel","email":"","orcid":"","institution":"Gazi Hastanesi","correspondingAuthor":false,"prefix":"","firstName":"Osman","middleName":"","lastName":"Yüksel","suffix":""},{"id":614162365,"identity":"73d7f9b7-f5da-4ed8-8094-d56168d8e127","order_by":12,"name":"Sezai Leventoğlu","email":"","orcid":"","institution":"Gazi Hastanesi","correspondingAuthor":false,"prefix":"","firstName":"Sezai","middleName":"","lastName":"Leventoğlu","suffix":""}],"badges":[],"createdAt":"2026-02-24 19:08:50","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-8960506/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-8960506/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":105844645,"identity":"4695aba0-7db2-4eb0-a19e-db7bf9586f8d","added_by":"auto","created_at":"2026-03-31 17:33:44","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":129676,"visible":true,"origin":"","legend":"\u003cp\u003eUnnumbered image in the Materials and Methods section.\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-8960506/v1/a3c8ea46f4c25c55dd1a20a7.png"},{"id":105906703,"identity":"a0e1b070-fd45-451f-9924-8cb5882fe54b","added_by":"auto","created_at":"2026-04-01 10:24:13","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":850654,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-8960506/v1/ec90fffb-9277-4e96-bd52-c64bcc5305d0.pdf"},{"id":105844646,"identity":"eb3ab6c5-0ad9-4fea-8840-84f084a6981a","added_by":"auto","created_at":"2026-03-31 17:33:44","extension":"docx","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":42213,"visible":true,"origin":"","legend":"","description":"","filename":"larstables.docx","url":"https://assets-eu.researchsquare.com/files/rs-8960506/v1/2abc310ae13cf6d8ba4cc802.docx"}],"financialInterests":"No competing interests reported.","formattedTitle":"Effects of Rectal Anastomotic Configuration and Circular Stapler Diameter on Postoperative Low Anterior Resection Syndrome: A Comparative Clinical Study","fulltext":[{"header":"Introduction","content":"\u003cp\u003eRectal cancer accounts for approximately one-third of all colorectal malignancies and remains a major cause of morbidity worldwide despite improving survival rates [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]. Standardisation of TME and wider implementation of neoadjuvant chemoradiotherapy protocols have improved local disease control and expanded eligibility for sphincter-preserving surgery [\u003cspan additionalcitationids=\"CR3\" citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]. As a result, although the need for permanent stoma has decreased, the functional outcomes of surgical treatment have become central in contemporary clinical practice.\u003c/p\u003e \u003cp\u003eWith increasing use of sphincter-preserving procedures, postoperative defaecatory dysfunction after low anterior resection has been increasingly recognised and conceptualised as Low Anterior Resection Syndrome (LARS) [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]. LARS is characterised by multidimensional symptoms\u0026mdash;urgency, clustering, faecal and flatus incontinence, increased stool frequency, and social restriction\u0026mdash;that may substantially impair quality of life. Reduced rectal reservoir capacity, pelvic autonomic nerve injury, low anastomosis, and neoadjuvant radiotherapy are accepted as key determinants of LARS development [\u003cspan additionalcitationids=\"CR6 CR7\" citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e]. In this context, as LARS has become a critical functional endpoint in rectal cancer surgery, the role of modifiable factors\u0026mdash;particularly anastomotic configuration and circular stapler diameter\u0026mdash;has gained increasing attention.\u003c/p\u003e \u003cp\u003eAnastomotic technique plays an important role in shaping functional outcomes after sphincter-preserving surgery. End-to-end and side-to-end colorectal anastomoses are both widely used in clinical practice and provide comparable anatomical continuity; however, they may differ in their effects on neorectal reservoir function and intrapelvic pressure distribution [\u003cspan additionalcitationids=\"CR10\" citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e]. Therefore, clarifying the impact of anastomotic configuration on LARS is central to efforts aimed at functional optimisation.\u003c/p\u003e \u003cp\u003eAdvances in circular stapler technology have enabled safe and reproducible anastomosis [\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e, \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e]. Nonetheless, stapler diameter and mechanical properties may also influence functional recovery [\u003cspan additionalcitationids=\"CR14\" citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e]. Stapler size may affect anastomotic tension, luminal calibre, and the physiological adaptation of the distal colon, thereby contributing to LARS [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e]. Although larger staplers are theoretically expected to provide a wider anastomosis, evidence suggests they may also increase tissue strain and impair sensorimotor function [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e, \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e]. Defining this relationship has direct clinical relevance for intraoperative decision-making.\u003c/p\u003e \u003cp\u003eAccordingly, this study aimed to evaluate the independent effects of anastomotic configuration (end-to-end vs side-to-end) and circular stapler diameter on LARS development, and to characterise the relationship between these technical variables and postoperative functional outcomes.\u003c/p\u003e"},{"header":"Materials and Methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003eStudy design and population\u003c/h2\u003e \u003cp\u003eThis observational retrospective cohort study evaluated the effects of anastomosis type and circular stapler diameter on LARS development in patients undergoing surgery for rectal cancer. Data from 446 patients who underwent low anterior resection between 2015 and 2023 were obtained from the hospital information system. Electronic medical records, operative notes, pathology reports, and outpatient follow-up data were reviewed.\u003c/p\u003e \u003cp\u003eAll patients were evaluated for postoperative functional outcomes. Demographic, clinical, and surgical factors potentially associated with LARS were recorded.\u003c/p\u003e \u003cp\u003e This retrospective study was approved by the Gazi University Ethics Committee (Approval No. 2024\u0026thinsp;\u0026minus;\u0026thinsp;1291) and was conducted in accordance with the Declaration of Helsinki. The requirement for written informed consent was waived due to the retrospective nature of the study.\u003c/p\u003e \u003c/div\u003e\n\u003ch3\u003eFunctional assessment\u003c/h3\u003e\n\u003cp\u003eFunctional outcomes were assessed using the validated LARS score, which objectively classifies post-LAR bowel dysfunction [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]. Patients meeting eligibility criteria completed the LARS questionnaire, and total scores were calculated according to the validated scoring system.\u003c/p\u003e\n\u003ch3\u003eInclusion and exclusion criteria\u003c/h3\u003e\n\u003cdiv id=\"Sec6\" class=\"Section2\"\u003e \u003ch2\u003eInclusion criteria:\u003c/h2\u003e \u003cp\u003e \u003cul\u003e \u003cli\u003e \u003cp\u003eHistologically confirmed rectal cancer or precancerous rectal lesions\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003eTumour localisation within the first 15 cm from the anal verge confirmed by rectoscopy and pelvic MRI\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003eAge\u0026thinsp;\u0026ge;\u0026thinsp;18 years\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003eAgreement to complete the LARS questionnaire and provide written informed consent\u003c/p\u003e \u003c/li\u003e \u003c/ul\u003e \u003c/p\u003e \u003c/div\u003e\n\u003ch3\u003eExclusion criteria:\u003c/h3\u003e\n\u003cp\u003e \u003cul\u003e \u003cli\u003e \u003cp\u003eBenign disease (e.g., rectovaginal fistula, colovesical fistula)\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003eASA score\u0026thinsp;\u0026gt;\u0026thinsp;3\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003eRecurrent disease\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003eTumour invasion from other primary organ malignancies\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003ePrevious Hartmann resection\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003eConcomitant major organ resections (e.g., transverse colectomy, right colectomy)\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003eAnastomotic leak\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003eAnastomotic stricture\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003eMetastatic disease\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003eHand-sewn anastomosis\u003c/p\u003e \u003c/li\u003e \u003c/ul\u003e \u003c/p\u003e \u003cp\u003eFor all patients, the following were recorded in detail: primary surgical approach, anastomosis type (end-to-end or side-to-end), stapler diameter, neoadjuvant chemoradiotherapy, tumour localisation, pathological stage, and early postoperative complications.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cdiv id=\"Sec8\" class=\"Section2\"\u003e \u003ch2\u003eData collection process\u003c/h2\u003e \u003cp\u003eA total of 309 patients fulfilled study criteria and underwent long-term functional assessment. All had at least 18 months of follow-up. The LARS questionnaire was administered either by telephone interview or face-to-face during outpatient follow-up. LARS categories were defined as:\u003c/p\u003e \u003cp\u003e \u003cul\u003e \u003cli\u003e \u003cp\u003e0\u0026ndash;20: No LARS\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003e21\u0026ndash;29: Minor LARS\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003e30\u0026ndash;42: Major LARS\u003c/p\u003e \u003c/li\u003e \u003c/ul\u003e \u003c/p\u003e \u003c/div\u003e\n\u003ch3\u003eLARS Questionnaire and Scoring System [5]\u003c/h3\u003e\n\u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"No\" id=\"Taba\" border=\"1\"\u003e \u003ccolgroup cols=\"3\"\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 \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eQuestion\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eResponse\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eScore\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e1. Do you ever have episodes of uncontrolled flatus?\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eNo, never\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eYes, less than once per week\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e4\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eYes, more than once per week\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e7\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2. Do you ever have accidental leakage of liquid stool?\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eNo, never\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eYes, less than once per week\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e3\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eYes, more than once per week\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e3\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e3. Bowel movement frequency per day\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eMore than 7 times/day\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e4\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e4\u0026ndash;7 times/day\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e2\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1\u0026ndash;3 times/day\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eLess than once/day\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e5\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e4. Do you need to open your bowels again within 1 hour (clustering)?\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eNo, never\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eYes, less than once per week\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e9\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eYes, more than once per week\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e11\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e5. Do you experience urgency?\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eNo, never\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eYes, less than once per week\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e11\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eYes, more than once per week\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e16\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cdiv id=\"Sec10\" class=\"Section2\"\u003e \u003ch2\u003eTumour localisation\u003c/h2\u003e \u003cp\u003eTumour localisation was classified using pelvic MRI and/or rectoscopy according to distance from the anal verge:\u003c/p\u003e \u003cp\u003e \u003cul\u003e \u003cli\u003e \u003cp\u003eLower rectum: 0\u0026ndash;5 cm\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003eMid rectum: 5\u0026ndash;10 cm\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003eUpper rectum: 10\u0026ndash;15 cm\u003c/p\u003e \u003c/li\u003e \u003c/ul\u003e \u003c/p\u003e \u003cp\u003eAll included cases had tumour localisation within 15 cm of the anal verge.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec11\" class=\"Section2\"\u003e \u003ch2\u003eRadiotherapy protocol\u003c/h2\u003e \u003cp\u003e \u003cul\u003e \u003cli\u003e \u003cp\u003eShort-course RT: 25 Gy total, 5 fractions (5 Gy \u0026times; 5), over 5 consecutive days.\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003eLong-course RT: 45\u0026ndash;50.4 Gy total, 25\u0026ndash;28 fractions (1.8\u0026ndash;2 Gy/day), over 5\u0026ndash;6 weeks; concurrent chemotherapy when indicated.\u003c/p\u003e \u003c/li\u003e \u003c/ul\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec12\" class=\"Section2\"\u003e \u003ch2\u003eSurgical technique and study variables\u003c/h2\u003e \u003cp\u003eAll procedures were performed by surgeons with at least 5 years of experience, following TME principles. Anastomoses were classified as end-to-end or side-to-end colorectal anastomosis. Stapler diameters (28, 29, 31, 33 mm) were extracted from operative records. Additional variables included neoadjuvant/adjuvant chemoradiotherapy, tumour distance from anal verge, pathological stage, and total/metastatic lymph node counts.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec13\" class=\"Section2\"\u003e \u003ch2\u003eStatistical analysis\u003c/h2\u003e \u003cp\u003e \u003cul\u003e \u003cli\u003e \u003cp\u003eAnalyses were performed using SPSS (IBM SPSS Statistics 27). Frequency tables and descriptive statistics were used for data summarisation.\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003eParametric methods were used for normally distributed continuous variables; comparisons among \u0026ge;\u0026thinsp;3 independent groups used ANOVA.\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003eNon-parametric methods were used for non-normally distributed variables; comparisons among \u0026ge;\u0026thinsp;3 independent groups used Kruskal\u0026ndash;Wallis H tests.\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003eAssociations between categorical variables were assessed with Pearson chi-square tests.\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003eRisk factors for LARS positivity were analysed with binary logistic regression (Backward LR model).\u003c/p\u003e \u003c/li\u003e \u003c/ul\u003e \u003c/p\u003e \u003c/div\u003e"},{"header":"Results","content":"\u003cp\u003eFrom 446 patients who underwent low anterior resection during the study period, 309 met inclusion criteria and had at least 18 months of functional follow-up. Of these, 60.5% (n\u0026thinsp;=\u0026thinsp;187) were male. Mean age was 62.11\u0026thinsp;\u0026plusmn;\u0026thinsp;12.07 years (median 63; range 24\u0026ndash;101). ASA class distribution was 14.2% (n\u0026thinsp;=\u0026thinsp;44) for ASA 1, 52.5% (n\u0026thinsp;=\u0026thinsp;162) for ASA 2, and 33.3% (n\u0026thinsp;=\u0026thinsp;103) for ASA 3. Anastomosis type was end-to-end in 125 patients (40.5%) and side-to-end in 184 patients (59.5%) (Table\u0026nbsp;1).\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eAccording to LARS score, 71.5% (n\u0026thinsp;=\u0026thinsp;221) had no LARS, 12.0% (n\u0026thinsp;=\u0026thinsp;37) had minor LARS, and 16.5% (n\u0026thinsp;=\u0026thinsp;51) had major LARS; overall LARS positivity (minor\u0026thinsp;+\u0026thinsp;major) was 28.5%. Mean LARS score was 14.48\u0026thinsp;\u0026plusmn;\u0026thinsp;13.07 (median 10; range 0\u0026ndash;42). Mean tumour diameter was 3.12\u0026thinsp;\u0026plusmn;\u0026thinsp;2.21 cm, mean total dissected lymph node count was 22.97\u0026thinsp;\u0026plusmn;\u0026thinsp;13.94, and mean metastatic lymph node count was 1.46\u0026thinsp;\u0026plusmn;\u0026thinsp;3.67(Table\u0026nbsp;2).\u003c/p\u003e\n\u003cdiv\u003e\n\u003ch2\u003eFactors associated with LARS in the full cohort\u003c/h2\u003e\n\u003cp\u003eAcross the entire cohort, no significant associations were observed between LARS categories and sex, anastomosis type (end-to-end vs side-to-end), pathological diagnosis, diverting stoma, adjuvant chemotherapy, general CT/RT classification, or RT dose (p\u0026thinsp;\u0026gt;\u0026thinsp;0.05, Table\u0026nbsp;9). However, ASA score, stapler diameter, tumour localisation, and neoadjuvant radiotherapy were significantly associated with LARS.\u003c/p\u003e\n\u003cp\u003eLARS frequency increased with increasing ASA score (p\u0026thinsp;\u0026lt;\u0026thinsp;0.001). While ASA 2 was most common in patients without LARS (56.6%), ASA 3 proportions increased to 45.9% in minor LARS and 54.9% in major LARS groups. Circular stapler diameter was also significantly associated with LARS (chi-square\u0026thinsp;=\u0026thinsp;10.827; p\u0026thinsp;=\u0026thinsp;0.004): 28\u0026ndash;29 mm staplers were used in 79.2% of patients without LARS, whereas 31\u0026ndash;33 mm staplers were more frequent in minor and major LARS groups (35.1% and 41.2%, respectively).\u003c/p\u003e\n\u003cp\u003eTumour localisation differed significantly across LARS categories (p\u0026thinsp;=\u0026thinsp;0.048). In the major LARS group, proximal tumour localisation reached 56.9%, higher than in no-LARS and minor-LARS groups. Neoadjuvant RT also differed significantly (p\u0026thinsp;=\u0026thinsp;0.041): long-course RT was more common in LARS-positive patients than in those without LARS (no LARS: 56.6%; minor: 73.0%; major: 64.7%).\u003c/p\u003e\n\u003cp\u003eAmong quantitative variables, age and tumour size were associated with LARS. Patients without LARS were significantly younger than both minor and major LARS groups (p\u0026thinsp;\u0026lt;\u0026thinsp;0.001) (Table\u0026nbsp;10). For tumour size, the significant difference was between minor and major LARS groups, with larger tumours in major LARS (p\u0026thinsp;=\u0026thinsp;0.030). Total and metastatic lymph node counts did not differ significantly among LARS categories (p\u0026thinsp;\u0026gt;\u0026thinsp;0.05).\u003c/p\u003e\n\u003cp\u003eIn backward LR multivariable logistic regression for overall LARS positivity (minor\u0026thinsp;+\u0026thinsp;major), independent predictors were age, long-course neoadjuvant radiotherapy, and circular stapler diameter:\u003c/p\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cp\u003eAge: OR 1.063 (95% CI 1.036\u0026ndash;1.089; p\u0026thinsp;\u0026lt;\u0026thinsp;0.001, Table\u0026nbsp;11)\u003c/p\u003e\n\u003c/li\u003e\n\u003cli\u003e\n\u003cp\u003eLong-course neoadjuvant RT vs no RT: OR 2.248 (95% CI 1.228\u0026ndash;4.115; p\u0026thinsp;=\u0026thinsp;0.009)\u003c/p\u003e\n\u003c/li\u003e\n\u003cli\u003e\n\u003cp\u003eStapler diameter 31\u0026ndash;33 mm vs 28\u0026ndash;29 mm: OR 2.395 (95% CI 1.398\u0026ndash;4.103; p\u0026thinsp;=\u0026thinsp;0.001)\u003c/p\u003e\n\u003c/li\u003e\n\u003c/ul\u003e\n\u003cp\u003eThese findings indicate that advanced age, long-course neoadjuvant RT, and larger stapler diameter are independently and clinically meaningful predictors of LARS after sphincter-preserving rectal cancer surgery.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv\u003e\n\u003ch2\u003ePatients with end-to-end anastomosis\u003c/h2\u003e\n\u003cp\u003eAmong 125 patients with end-to-end anastomosis, 85 (68.0%) had no LARS, 15 (12.0%) had minor LARS, and 25 (20.0%) had major LARS. No significant associations were found between LARS categories and sex, stapler diameter group (28\u0026ndash;29 mm vs 31\u0026ndash;33 mm), chemoradiotherapy classification, pathological diagnosis, stoma status, adjuvant chemotherapy, neoadjuvant RT, or RT dose (p\u0026thinsp;\u0026gt;\u0026thinsp;0.05, Table\u0026nbsp;3), indicating comparable distribution across groups.\u003c/p\u003e\n\u003cp\u003eIn contrast, ASA score was significantly associated with LARS (p\u0026thinsp;=\u0026thinsp;0.016). ASA 2 predominated in no-LARS patients (48.2%), whereas ASA 3 increased to 66.7% in minor LARS and 56.0% in major LARS groups. Tumour localisation was also associated with LARS (p\u0026thinsp;=\u0026thinsp;0.038): tumours were more often in the mid rectum among no-LARS patients, distal in minor LARS, and proximal in major LARS.\u003c/p\u003e\n\u003cp\u003eFor quantitative variables, only age differed significantly among LARS groups (p\u0026thinsp;\u0026lt;\u0026thinsp;0.001, Table\u0026nbsp;4). Bonferroni-corrected pairwise analyses showed that patients without LARS were significantly younger than both minor and major LARS groups. No significant differences were found for total lymph node count, metastatic lymph node count, tumour size, or stapler diameter (p\u0026thinsp;\u0026gt;\u0026thinsp;0.05).\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eIn backward LR multivariable logistic regression for LARS positivity (minor\u0026thinsp;+\u0026thinsp;major) in the end-to-end subgroup, only age and metastatic lymph node count remained independent predictors:\u003c/p\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cp\u003eAge: OR 1.096 (95% CI 1.048\u0026ndash;1.146; p\u0026thinsp;\u0026lt;\u0026thinsp;0.001, Table\u0026nbsp;5)\u003c/p\u003e\n\u003c/li\u003e\n\u003cli\u003e\n\u003cp\u003eMetastatic lymph node count: OR 1.221 (95% CI 1.015\u0026ndash;1.468; p\u0026thinsp;=\u0026thinsp;0.034)\u003c/p\u003e\n\u003c/li\u003e\n\u003c/ul\u003e\n\u003cp\u003eEach one-year increase in age and each additional metastatic lymph node were associated with a significant increase in LARS risk.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv\u003e\n\u003ch2\u003ePatients with side-to-end anastomosis\u003c/h2\u003e\n\u003cp\u003eAmong 184 patients with side-to-end anastomosis, 136 (73.9%) had no LARS, 22 (12.0%) had minor LARS, and 26 (14.1%) had major LARS (Table\u0026nbsp;6). In this subgroup, no significant differences were observed between LARS categories in sex, pathological diagnosis, diverting stoma, adjuvant chemotherapy, overall CT/RT classification, neoadjuvant RT, or RT dose (p\u0026thinsp;\u0026gt;\u0026thinsp;0.05).\u003c/p\u003e\n\u003cdiv\u003e\u0026nbsp;\u003c/div\u003e\n\u003cp\u003eASA score was significantly associated with LARS (chi-square\u0026thinsp;=\u0026thinsp;12.260; p\u0026thinsp;=\u0026thinsp;0.016). ASA 2 predominated in no-LARS and minor-LARS groups (61.8% and 50.0%, respectively), whereas ASA 3 rose to 53.8% in major LARS. Tumour localisation was also significant (chi-square\u0026thinsp;=\u0026thinsp;10.509; p\u0026thinsp;=\u0026thinsp;0.033): proximal localisation was more frequent in no-LARS and major-LARS groups (44.1% and 57.7%), whereas mid-rectal localisation predominated in minor LARS (54.5%).\u003c/p\u003e\n\u003cp\u003eIn this subgroup, circular stapler diameter emerged as a strong discriminating factor (p\u0026thinsp;\u0026lt;\u0026thinsp;0.001). While 92.6% of no-LARS patients received 28\u0026ndash;29 mm staplers, the proportion of 31\u0026ndash;33 mm stapler use was 36.4% in minor LARS and 34.6% in major LARS. Therefore, larger stapler use was significantly more frequent in LARS-positive patients.\u003c/p\u003e\n\u003cp\u003eAmong quantitative variables, age was the only factor associated with LARS (p\u0026thinsp;=\u0026thinsp;0.018, Table\u0026nbsp;7). Post-hoc analyses indicated that the major LARS group was significantly older than the no-LARS group. Total lymph node count, metastatic lymph node count, and tumour size showed no significant differences (p\u0026thinsp;\u0026gt;\u0026thinsp;0.05).\u003c/p\u003e\n\u003cdiv\u003e\u0026nbsp;\u003c/div\u003e\n\u003cp\u003eIn backward LR multivariable logistic regression for LARS positivity in the side-to-end subgroup, independent predictors were age and circular stapler diameter:\u003c/p\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cp\u003eAge: OR 1.055 (95% CI 1.019\u0026ndash;1.092; p\u0026thinsp;=\u0026thinsp;0.003, Table\u0026nbsp;8)\u003c/p\u003e\n\u003c/li\u003e\n\u003cli\u003e\n\u003cp\u003eStapler diameter 31\u0026ndash;33 mm vs 28\u0026ndash;29 mm: OR 6.910 (95% CI 2.882\u0026ndash;16.565; p\u0026thinsp;\u0026lt;\u0026thinsp;0.001)\u003c/p\u003e\n\u003c/li\u003e\n\u003c/ul\u003e\n\u003cdiv\u003e\u0026nbsp;\u003c/div\u003e\n\u003cp\u003eThus, in side-to-end anastomosis, larger stapler diameter was associated with nearly a sevenfold increase in LARS risk.\u003c/p\u003e\n\u003c/div\u003e"},{"header":"Discussion","content":"\u003cp\u003eThis study systematically evaluated associations between LARS\u0026mdash;one of the most important indicators of postoperative bowel dysfunction after sphincter-preserving rectal cancer surgery\u0026mdash;and surgical/oncological variables in a relatively large cohort. Overall LARS positivity (minor\u0026thinsp;+\u0026thinsp;major) was 28.5%, and major LARS prevalence was 16.5%. Compared with previously reported LARS prevalence (often 30\u0026ndash;60%), these findings still represent a clinically meaningful long-term functional burden, particularly for major LARS [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e, \u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e]. The results reinforce the need to integrate long-term anorectal function into treatment planning alongside oncological outcomes.\u003c/p\u003e \u003cp\u003eNo significant difference in LARS development was found between end-to-end and side-to-end anastomoses. The lack of independent predictive value of anastomotic type in either whole-cohort or subgroup analyses may suggest that modern TME practice has reduced technique-related functional disparities [\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e, \u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e]. Standardised TME and careful preservation of pelvic autonomic nerves may attenuate the clinical impact of anastomotic geometry. Although some studies suggest that side-to-end anastomosis may improve reservoir function and continence [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e, \u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e], this theoretical advantage is not consistently reflected in patient-reported functional scores. Our findings support the view that LARS is driven more strongly by factors such as anastomotic level, associated treatments, and patient characteristics than by configuration alone.\u003c/p\u003e \u003cp\u003eOne of the most notable findings was the strong association between circular stapler diameter and LARS. In the side-to-end subgroup, use of a 31\u0026ndash;33 mm stapler was associated with an almost sevenfold increase in LARS positivity compared with 28\u0026ndash;29 mm staplers. In the full-cohort multivariable model, larger stapler diameter remained an independent predictor with approximately 2.4-fold increased risk. Although larger staplers are theoretically expected to reduce obstruction by providing a wider lumen, they may increase mechanical strain at the anal canal and neorectal level, with potential micro-level injury to sphincter and perianastomotic neural structures [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e, \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e, \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e]. This biomechanical mechanism may contribute to dominant LARS symptoms such as urgency and clustering. Nevertheless, despite the strong observed association, causality should be confirmed in prospective studies with detailed physiological and functional evaluation. Clinically, these data indicate that stapler diameter should be considered not only for technical feasibility and lumen patency but also for long-term function.\u003c/p\u003e \u003cp\u003eAdvanced age was independently and consistently associated with LARS across both anastomotic subgroups and the full cohort. Logistic models showed that each additional year of age was associated with a significant increase in LARS risk. While some studies have linked younger age and male sex to higher LARS risk\u0026mdash;possibly due to higher functional expectations, symptom awareness, and social impact [\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e, \u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e, \u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e]\u0026mdash;ageing-related physiological changes may also impair postoperative functional recovery: reduced pelvic floor tone, slower autonomic/somatic neural conduction, disordered colonic motility, and higher comorbidity burden. Despite heterogeneity in the literature [\u003cspan additionalcitationids=\"CR22\" citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e], our findings support advanced age as a clinically important risk factor that should be incorporated into preoperative counselling and surgical planning.\u003c/p\u003e \u003cp\u003eLong-course neoadjuvant radiotherapy was another key independent predictor in multivariable analysis, associated with approximately 2.2-fold increased LARS risk. This aligns with recognised effects of radiotherapy on anorectal physiology, including reduced rectal compliance, mucosal/submucosal fibrosis, reduced sensory receptor density, and altered internal sphincter tone [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e, \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e, \u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e, \u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e, \u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e]. These mechanisms may particularly drive major LARS components such as urgency, clustering, and incontinence. Our results underline the need to balance oncological benefits and functional costs of neoadjuvant treatment through multidisciplinary, patient-specific decision-making.\u003c/p\u003e \u003cp\u003eThe significant association between higher ASA score and LARS in both subgroup and whole-cohort analyses suggests that patients with limited systemic reserve and heavier comorbidity burden may have poorer functional recovery [\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e]. Surgical stress response, limited mobilisation, and cardiometabolic comorbidities may indirectly impair bowel motility and pelvic floor function. Tumour localisation was also associated with major LARS, with higher rates in proximally located tumours in this dataset\u0026mdash;a finding that may reflect a more complex interaction than the classical expectation of higher LARS in distal disease [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e, \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e, \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e, \u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e]. Potential contributors include more intensive neoadjuvant strategies, broader resections, or differences in anastomotic level. Clarification requires future studies with standardised millimetric anastomotic height measurements.\u003c/p\u003e \u003cp\u003eIn the end-to-end subgroup, metastatic lymph node count independently predicted LARS positivity, suggesting a possible link between higher disease burden and functional morbidity. Likewise, the larger tumour size observed in major LARS (vs minor LARS) in the full cohort suggests that extent of resection may contribute to dysfunction. However, as these variables were not consistently independent across all models, their effects should be interpreted cautiously in light of potential confounding factors (e.g., intensified neoadjuvant therapy, more extensive dissection, lower anastomosis, longer operating time) [\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eThis study has several strengths. First, it is among the limited studies assessing the relationship between circular stapler diameter and postoperative functional morbidity after sphincter-preserving rectal cancer surgery in a relatively large cohort, with separate analyses for end-to-end and side-to-end subgroups. Secondly, standardised TME-based surgery by experienced surgeons reduced operative heterogeneity, enabling clearer assessment of technical variables. Thirdly, multivariable evaluation of numerous clinical and oncological factors with backward logistic regression improved statistical robustness. Finally, functional assessment after at least 18 months allowed evaluation of long-term, persistent dysfunction rather than only early postoperative changes.\u003c/p\u003e \u003cp\u003eLimitations should also be acknowledged. The retrospective design carries unavoidable risks of selection and information bias. Administration of LARS scoring by telephone or face-to-face interview may introduce response-mode variability. Lack of fully standardised objective recording of anastomotic height (e.g., intraoperative measurement or postoperative imaging) limited finer analysis of neorectal length\u0026ndash;function relationships. Preoperative anorectal function, baseline continence status, and pelvic floor dysfunction were not systematically documented and may have acted as uncontrolled confounders. Stapler selection was surgeon-dependent, introducing potential performance bias. In addition, more granular radiotherapy parameters (e.g., dose distribution, field design, RT technique) were unavailable, restricting deeper exploration of RT\u0026ndash;LARS relationships.\u003c/p\u003e \u003cp\u003eTaken together, these findings indicate that modifiable factors\u0026mdash;particularly circular stapler diameter and neoadjuvant radiotherapy intensity\u0026mdash;significantly influence LARS risk, while patient-level factors such as advanced age and higher ASA score also remain clinically important. In sphincter-preserving rectal cancer surgery, technical choices and treatment strategies should therefore be evaluated not only through oncological endpoints but also through the lens of long-term anorectal function. Future prospective, ideally randomised studies with detailed functional profiling are needed to optimise stapler selection and neoadjuvant strategies.\u003c/p\u003e"},{"header":"Conclusion","content":"\u003cp\u003eThis retrospective cohort study provides a detailed characterisation of factors associated with LARS after sphincter-preserving surgery for rectal cancer. LARS appears to be a multidimensional postoperative outcome influenced not only by anatomical factors but also by surgical technique, radiotherapy regimen, patient-related characteristics, and tumour-related variables. Future prospective, preferably randomised studies with long-term follow-up are required to define more precisely the functional impact of stapler diameter and neoadjuvant treatment strategies and to strengthen evidence-based clinical decision-making.\u003c/p\u003e"},{"header":"Declarations","content":"\u003ch3\u003ePatient consent\u003c/h3\u003e\n\u003cp\u003eWritten informed consent was obtained from the patient for publication.\u003c/p\u003e\u003cp\u003e \u003ch2\u003eConflicts of interest\u003c/h2\u003e \u003cp\u003eThe authors declare no competing interests.\u003c/p\u003e \u003c/p\u003e \u003cp\u003e \u003cstrong\u003eEthical approval\u003c/strong\u003e \u003cp\u003e Ethical approval was granted by the university ethical review board.\u003c/p\u003e \u003c/p\u003e\u003ch2\u003eFunding\u003c/h2\u003e \u003cp\u003eThis research received no specific grant from any funding agency.\u003c/p\u003e\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003e\u0026Ouml;.K., E.A., G.U., A.T., I.E., A.Y. and S.A. conceived and designed the study, and analysed and interpreted the data. \u0026Ouml;.K.,\u0026Ccedil;.B., K.D., H.B., O.Y. and S.L. conducted the literature review and critically appraised the relevant literature. \u0026Ouml;.K., \u0026Ccedil;.B., H.G., H.B., O.Y. and S.L. provided scientific and technical support and critically revised the manuscript for important intellectual content. All authors read and approved the final manuscript.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eSiegel, R.L., et al., \u003cem\u003eCancer Statistics, 2021\u003c/em\u003e. CA Cancer J Clin, 2021. 71(1): p. 7\u0026ndash;33.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eBoublikova, L., et al., \u003cem\u003eTotal neoadjuvant therapy in rectal cancer: the evidence and expectations\u003c/em\u003e. Crit Rev Oncol Hematol, 2023. 192: p. 104196.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eNocera, F., et al., \u003cem\u003eOptimising functional outcomes in rectal cancer surgery\u003c/em\u003e. Langenbecks Arch Surg, 2021. 406(2): p. 233\u0026ndash;250.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLeibold, T. and J.G. Guillem, \u003cem\u003eThe role of neoadjuvant therapy in sphincter-saving surgery for mid and distal rectal cancer\u003c/em\u003e. Cancer Invest, 2010. 28(3): p. 259\u0026ndash;67.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eEmmertsen, K.J. and S. Laurberg, \u003cem\u003eLow anterior resection syndrome score: development and validation of a symptom-based scoring system for bowel dysfunction after low anterior resection for rectal cancer\u003c/em\u003e. Ann Surg, 2012. 255(5): p. 922\u0026ndash;8.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eRosen, H., C.G. Sebesta, and C. Sebesta, \u003cem\u003eManagement of Low Anterior Resection Syndrome (LARS) Following Resection for Rectal Cancer\u003c/em\u003e. Cancers (Basel), 2023. 15(3).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eZhang, R., et al., \u003cem\u003eClinical Management of Low Anterior Resection Syndrome: Review of the Current Diagnosis and Treatment\u003c/em\u003e. Cancers (Basel), 2023. 15(20).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eYeo, S.M. and G.M. Son, \u003cem\u003eLow Anterior Resection Syndrome: Pathophysiology, Risk Factors, and Current Management\u003c/em\u003e. Ewha Med J, 2022. 45(4): p. e12.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eScardino, A., et al., \u003cem\u003eEffect of powered circular stapler in colorectal anastomosis after left-sided colic resection: systematic review and meta-analysis\u003c/em\u003e. Int J Colorectal Dis, 2024. 39(1): p. 152.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eBrisinda, G., et al., \u003cem\u003eEnd-to-end versus end-to-side stapled anastomoses after anterior resection for rectal cancer\u003c/em\u003e. J Surg Oncol, 2009. 99(1): p. 75\u0026ndash;9.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eBondeven, P., et al., \u003cem\u003eNeoadjuvant therapy abolishes the functional benefits of a larger rectal remnant, as measured by magnetic resonance imaging after restorative rectal cancer surgery\u003c/em\u003e. European Journal of Surgical Oncology (EJSO), 2015. 41(11): p. 1493\u0026ndash;1499.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eShibutani, M., et al., \u003cem\u003eImpact of a circular powered stapler on preventing anastomotic leakage in patients with left-sided colorectal cancer: a retrospective study\u003c/em\u003e. BMC Surg, 2023. 23(1): p. 205.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eHerzig, D.O., et al., \u003cem\u003eAssessment of a circular powered stapler for creation of anastomosis in left-sided colorectal surgery: A prospective cohort study\u003c/em\u003e. International Journal of Surgery, 2020. 84: p. 140\u0026ndash;146.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eOhtani, H., et al., \u003cem\u003eA Meta-analysis of Powered Circular Stapler Versus Manual Circular Stapler for Colorectal Anastomosis\u003c/em\u003e. In Vivo, 2025. 39(4): p. 2165\u0026ndash;2175.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eReif de Paula, T., et al., \u003cem\u003eAnalysis of the impact of EEA stapler size on risk of anastomotic complications in colorectal anastomosis: does size matter?\u003c/em\u003e Tech Coloproctol, 2020. 24(4): p. 283\u0026ndash;290.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSarcher, T., et al., \u003cem\u003eAnterior resection syndrome: What should we tell practitioners and patients in 2018?\u003c/em\u003e Journal of Visceral Surgery, 2018. 155(5): p. 383\u0026ndash;391.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSun, R., et al., \u003cem\u003eThe incidence and risk factors of low anterior resection syndrome (LARS) after sphincter-preserving surgery of rectal cancer: a systematic review and meta-analysis\u003c/em\u003e. Supportive Care in Cancer, 2021. 29(12): p. 7249\u0026ndash;7258.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eMcKechnie, T., et al., \u003cem\u003eEnd-to-end versus end-to-side anastomosis for low anterior resection: A systematic review and meta-analysis of randomized controlled trials\u003c/em\u003e. Surgery, 2021. 170(2): p. 397\u0026ndash;404.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003ePlanellas, P., et al., \u003cem\u003eRandomized clinical trial comparing side to end vs end to end techniques for colorectal anastomosis\u003c/em\u003e. Int J Surg, 2020. 83: p. 220\u0026ndash;229.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eHaque AA, O.M., Jalal MT., \u003cem\u003eComparison of incidence of anastomotic leak \u0026amp; low anterior resection syndrome between end \u0026amp; side to end colorectal anastomosis after low anterior resection for Rectal cancer\u003c/em\u003e. Journal of Surgery and Research., 2025(8): p. 42\u0026ndash;48.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLunca, S., et al., \u003cem\u003ePredictive Risk Factors for Low Anterior Resection Syndrome (LARS) in Rectal Cancer\u0026mdash;An Observational Cohort Study\u003c/em\u003e. Journal of Clinical Medicine, 2025. 14(8): p. 2831.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eBattersby, N.J., et al., \u003cem\u003eDevelopment and external validation of a nomogram and online tool to predict bowel dysfunction following restorative rectal cancer resection: the POLARS score\u003c/em\u003e. Gut, 2018. 67(4): p. 688\u0026ndash;696.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eFilips, A., et al., \u003cem\u003eLARS is Associated with Lower Anastomoses, but not with the Transanal Approach in Patients Undergoing Rectal Cancer Resection\u003c/em\u003e. World Journal of Surgery, 2021. 45(3): p. 873\u0026ndash;879.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eHernandez, M.C., P. Wong, and K. Melstrom, \u003cem\u003eLow anterior resection syndrome\u003c/em\u003e. J Surg Oncol, 2023. 127(8): p. 1271\u0026ndash;1276.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eDulskas, A., et al., \u003cem\u003eLong-term bowel dysfunction following low anterior resection\u003c/em\u003e. Sci Rep, 2020. 10(1): p. 11882.\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"},{"header":"Tables","content":"\u003cp\u003eTables 1 to 11 are available in the Supplementary Files section.\u003c/p\u003e\n"}],"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":"techniques-in-coloproctology","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"tcol","sideBox":"Learn more about [Techniques in Coloproctology](http://link.springer.com/journal/10151)","snPcode":"10151","submissionUrl":"https://submission.nature.com/new-submission/10151/3","title":"Techniques in Coloproctology","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"","lastPublishedDoi":"10.21203/rs.3.rs-8960506/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-8960506/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003ch2\u003eBackground\u003c/h2\u003e \u003cp\u003eLow Anterior Resection Syndrome (LARS) is a major determinant of long-term anorectal dysfunction after sphincter-preserving rectal cancer surgery. The mechanical properties of the anastomosis\u0026mdash;including its configuration and circular stapler diameter\u0026mdash;may influence neorectal compliance, sensory function, and postoperative evacuation dynamics. This study aimed to define the independent contributions of anastomotic configuration and stapler diameter to LARS development.\u003c/p\u003e\u003ch2\u003eMethods\u003c/h2\u003e \u003cp\u003eA retrospective cohort of 446 patients who underwent total mesorectal excision (TME) and low anterior resection between 2015 and 2023 was reviewed. A total of 309 patients who had at least 18 months of functional follow-up and validated LARS assessment were included. All anastomoses were created using double-row circular staplers, in either end-to-end or side-to-end configuration. Stapler diameter (28\u0026ndash;29 mm vs 31\u0026ndash;33 mm), anastomotic level, neoadjuvant treatment protocol, tumour morphology, and total dissected lymph node count were recorded systematically. Functional outcomes were assessed with the validated LARS score. Independent predictors of LARS were identified using backward stepwise multivariable logistic regression.\u003c/p\u003e\u003ch2\u003eResults\u003c/h2\u003e \u003cp\u003eThe overall LARS incidence was 28.5%. In the end-to-end subgroup, age (OR 1.096) and metastatic lymph node count (OR 1.221) were independent predictors of LARS. In the side-to-end subgroup, a larger stapler diameter (31\u0026ndash;33 mm) markedly increased LARS risk (OR 6.910), while age remained an independent determinant (OR 1.055). In the full cohort, advanced age (OR 1.063), long-course neoadjuvant radiotherapy (OR 2.248), and larger stapler diameter (OR 2.395) were independently associated with LARS.\u003c/p\u003e\u003ch2\u003eConclusion\u003c/h2\u003e \u003cp\u003eAnastomotic configuration was not independently associated with postoperative LARS development, whereas larger stapler diameter was significantly and independently associated with an increased risk of LARS, particularly in side-to-end anastomoses. Advanced age and long-course neoadjuvant radiotherapy were also consistently associated with impaired long-term functional recovery. These findings underscore the importance of meticulous intraoperative stapler selection and individualised surgical planning, as technical decisions may have measurable long-term effects on anorectal function.\u003c/p\u003e","manuscriptTitle":"Effects of Rectal Anastomotic Configuration and Circular Stapler Diameter on Postoperative Low Anterior Resection Syndrome: A Comparative Clinical Study","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2026-03-31 17:33:40","doi":"10.21203/rs.3.rs-8960506/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2026-04-23T13:33:30+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-04-20T09:57:24+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-04-18T17:02:19+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"171058199323499223702167881207969958442","date":"2026-03-27T22:18:24+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"335773366230770568706923464242708683645","date":"2026-03-27T11:50:02+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2026-03-27T11:43:44+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2026-03-20T05:08:28+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2026-02-27T06:01:11+00:00","index":"","fulltext":""},{"type":"submitted","content":"Techniques in Coloproctology","date":"2026-02-24T18:55:58+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"techniques-in-coloproctology","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"tcol","sideBox":"Learn more about [Techniques in Coloproctology](http://link.springer.com/journal/10151)","snPcode":"10151","submissionUrl":"https://submission.nature.com/new-submission/10151/3","title":"Techniques in Coloproctology","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"5a3e2152-70ae-4069-99a1-120ebcf093db","owner":[],"postedDate":"March 31st, 2026","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[],"tags":[],"updatedAt":"2026-05-06T17:53:12+00:00","versionOfRecord":[],"versionCreatedAt":"2026-03-31 17:33:40","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-8960506","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-8960506","identity":"rs-8960506","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}