Proportional Single Anastomosis Sleeve Ileal (SASI) Bypass Based on Total Small Bowel Length: Optimizing Outcomes and Reducing Malnutrition

Proportional Single Anastomosis Sleeve Ileal (SASI) Bypass Based on Total Small Bowel Length: Optimizing Outcomes and Reducing Malnutrition | 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 Proportional Single Anastomosis Sleeve Ileal (SASI) Bypass Based on Total Small Bowel Length: Optimizing Outcomes and Reducing Malnutrition Tzu-Ling Huang, Yun-Ning Chiu, Kuo-Hung Huang, Wen-Liang Fang, and 2 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-6899502/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract Introduction Single anastomosis sleeve ileal (SASI) bypass is a novel bariatric procedure typically performed with a fixed common limb of 250 cm. However, this approach may increase the risk of malnutrition. In this study, we modified the bypass length to 40% of the total small bowel length and evaluated the efficacy and safety of this proportional SASI technique. Methods In this study, patients with obesity who underwent proportional SASI between February 2023 and March 2024 were enrolled. Of 36 patients, 30 were included in the final analysis after excluding those with revisional surgery or loss to follow-up. The primary outcome was total weight loss (TWL) at 12 months. Secondary outcomes included changes in nutritional markers and postoperative complications. Results The cohort had a male-to-female ratio of 1:1, with a mean age of 40 years and mean preoperative BMI of 43.2 kg/m². The mean TWL was 30.0% at 12 months. Hemoglobin decreased slightly (14.1 to 13.7 g/dL, p = 0.121), while albumin remained stable at 4.3 g/dL. Significant improvements were observed in HbA1c (6.5% to 5.4%, p <0.001), triglycerides (207.0 to 83.3 mg/dL, p <0.001), and total cholesterol (181.8 to 153.7 mg/dL, p <0.001). The incidence of gallstone formation was 18.5%, while reflux esophagitis (grade B or higher) and marginal ulcers were both 8.7% at 1 year postoperatively. Conclusions SASI with proportional bypass appears to be an effective and safe procedure. It achieves substantial weight loss and metabolic improvement while maintaining nutritional stability. single anastomosis sleeve ileal bypass (SASI) proportional bypass bariatric surgery Figures Figure 1 Key Points Proportional SASI with bypass length of 40% of the total small bowel is an effective yet safe alternative compared to fixed-length SASI. Mean total weight loss at 12 months was 30.0%. Significant metabolic improvements were achieved, including reductions in HbA1c, triglycerides, cholesterol and the severity of fatty liver. Nutritional safety was preserved, with no hypoalbuminemia and a low anemia rate (7.4%), suggesting reduced malabsorption risk. Introduction The global obesity epidemic has escalated significantly over the past few decades. Since 1990, the prevalence of adult obesity has more than doubled. In 2022, an estimated 2.5 billion adults worldwide were classified as overweight, with approximately 890 million meeting the criteria for obesity. Taiwan mirrors these global trends, with recent reports indicating that around 16% of adults are living with obesity [ 1 ]. This surge is largely driven by shifts toward energy-dense diets, reduced physical activity, and increasing urbanization—factors that collectively contribute to a heightened risk of chronic conditions such as type 2 diabetes, cardiovascular disease, non-alcoholic fatty liver disease, and various cancers [ 2 ]. Given the serious health risks associated with obesity, treatment strategies have evolved beyond lifestyle modification and medication. Bariatric surgery has emerged as the most effective long-term solution for severe obesity. Early procedures, such as the jejunoileal bypass, were largely malabsorptive but carried high complication rates [ 3 ]. By the 1980s, safer options like Roux-en-Y gastric bypass (RYGB) became more popular [ 4 ]. The rise of laparoscopic techniques in the 1990s enabled less invasive procedures, including laparoscopic RYGB, adjustable gastric banding, and later, sleeve gastrectomy (SG), which is now widely performed due to its safety and efficacy [ 5 ]. In recent years, sleeve-plus procedures have emerged to improve both weight loss and metabolic outcomes [ 6 ]. One such innovation is the single anastomosis sleeve ileal (SASI) bypass, which evolved from the original Santoro procedure. In the commonly adopted version introduced by Dr. Mahdy, SASI combines sleeve gastrectomy with a single anastomosis to a loop of the ileum located 250 cm from the ileocecal valve. This hybrid procedure aims to harness both restrictive and hormonal mechanisms to enhance weight loss and glycemic control. SASI has demonstrated promising outcomes, particularly in the management of type 2 diabetes, and appears to reduce certain risks—such as bile reflux and severe malnutrition—associated with procedures like RYGB and one anastomosis gastric bypass (OAGB) [ 7 ]. However, a notable incidence of malnutrition—including hypoalbuminemia, iron deficiency anemia, and vitamin deficiencies—has still been reported in published SASI series [ 8 , 9 ]. This suggests that a fixed common limb length of 250 cm may be insufficient for some patients, as it does not account for individual variation in small bowel length.The total small intestine in adults measures approximately 6 meters, with a functional jejunum-to-ileum ratio of about 4:6 [ 10 , 11 ]. Therefore, we hypothesize that a proportional bypass—specifically bypassing 40% of the total small bowel length—may be a more physiologically appropriate approach. This study aims to evaluate the outcomes of this modified SASI procedure at our institution, focusing on weight loss efficacy, metabolic improvements, and nutritional impact. Methods Study Design and Patient Selection This was a retrospective study involving 36 patients with obesity who underwent the modified SASI procedure at Taipei Veterans General Hospital between February 2023 and March 2024. Patients who had undergone revisional SASI or were lost to follow-up right after the operation were excluded. Preoperative and postoperative data, regarding weight, metabolic and nutritional parameters, and complications were registered every 3 months after SASI procedure. Abdominal sonography and panendoscopy were performed 12 months after the operation for evaluation. Surgical Technique The modified SASI procedure consisted of a laparoscopic sleeve gastrectomy (LSG) followed by a proportionally determined sleeve ileal bypass, rather than using a fixed 250 cm common limb. LSG was performed using a 40 Fr bougie as a guide. Stapling began approximately 6 cm from the pylorus and ended 1 cm away from the angle of His. Following LSG, the total small bowel length was measured intraoperatively. A bypass of 40% of the total measured length was performed, corresponding approximately to the estimated junction between the jejunum and ileum. The sleeve-ileal anastomosis was 4 cm in length, created in an antecolic, isoperistaltic manner on the greater curvature side of the antrum. The anastomotic entry site was closed in two layers using a continuous barbed suture. Outcome Measurement The primary outcome was the percentage of total body weight loss (TWL%) at 12 months postoperatively. Secondary outcomes included metabolic changes—specifically glycemic control, lipid profiles, uric acid levels, and albumin levels—the incidence of anemia, changes in the degree of fatty liver, and postoperative complications. Statistical Analysis Descriptive statistics were used to summarize baseline characteristics and postoperative outcomes. Changes in continuous variables over time were analyzed using the nonparametric Wilcoxon signed-rank test. A p -value of < 0.05 was considered statistically significant. Results A total of 36 patients underwent the modified SASI bypass between February 2023 and March 2024 at Taipei Veterans General Hospital. Two patients were excluded due to prior bariatric surgery, and four were lost to follow-up. A total of 30 patients were included in the study. The mean age was 40.0 ± 8.2 years (range: 22–58), with an equal distribution of male and female participants (15 each, 50%). Five patients (16.7%) were active smokers. The mean preoperative body weight was 124.3 ± 26.3 kg, and the mean body mass index (BMI) was 43.2 ± 6.6 kg/m². Regarding comorbidities, 12 patients (40%) had type 2 diabetes mellitus, 18 (60%) had hypertension, and 17 (56.7%) had hyperlipidemia. The mean total small intestine length measured intraoperatively was 817 ± 191 cm, and the mean bypassed length was 328 ± 79 cm, corresponding to 40% of the total length. Preoperative endoscopy showed that 7 patients (23.3%) had no reflux esophagitis, 22 (73.3%) had grade A esophagitis, and 1 patient (3.3%) had grade B esophagitis. Assessment of fatty liver revealed that 23 patients (76.7%) had severe fatty liver, 5 (16.7%) had moderate fatty liver, and 1 patient each (3.3%) had mild or no fatty liver (Table 1 ). Table 1 Patient demographics Variables Value Age (years) 40.0 ± 8.2 (22–58) Sex Male 15 (50%) Female 15 (50%) Smoker 5 (16.7%) Body weight at operation (kg) 124.3 ± 26.3 BMI at operation (kg/m 2 ) 43.2 ± 6.6 Diabetes mellitus 12 (40%) Hypertension 18 (60%) Hyperlipidemia 17 (56.7%) Small intestine length (cm) Total length 817 ± 191 Bypassed length 328 ± 79 GERD Negative 7 (23.3%) Grade A 22 (73.3%) Grade B 1 (3.3%) Fatty liver Non 1 (3.3%) Mild 1 (3.3%) Moderate 5 (16.7%) Severe 23 (76.7%) GERD: gastroesophageal reflux disease The follow-up rate was 96.7% at 3 months, 93.3% at 6 months, and 90.0% at 12 months. Among the 27 patients who completed 12 months of follow-up, the mean total weight loss percentage (TWL%) was 30.0 ± 7.4%. The mean body mass index (BMI) decreased from 43.2 ± 6.6 kg/m² preoperatively to 30.5 ± 5.7 kg/m² at 12 months. Adequate weight loss (defined as TWL% > 20%) was achieved in 25 of the 27 patients (92.6%). Correlation analyses were performed to evaluate the relationship between total weight loss percentage (TWL%) and both preoperative BMI and total small bowel length. No significant linear correlation was found between preoperative BMI and TWL% (correlation coefficient R = 0.011; Fig. 1 A). Similarly, there was no significant correlation between total small bowel length and TWL% (R = 0.111; Fig. 1 B). At 12 months postoperatively, improvements in metabolic parameters were observed. Mean HbA1c decreased from 6.5 ± 1.1% preoperatively to 5.4 ± 0.4% ( p < 0.001). Among the 12 patients with type 2 diabetes, 7 (58%) achieved diabetes remission, defined as HbA1c < 6% without the need for antidiabetic medications, while the remaining 5 patients (42%) showed improved glycemic control. Serum triglyceride levels decreased markedly from 207.0 ± 131.4 mg/dL to 83.3 ± 32.6 mg/dL ( p < 0.001), and total cholesterol levels declined from 181.8 ± 36.0 mg/dL to 153.7 ± 30.1 mg/dL ( p = 0.001). High-density lipoprotein (HDL) levels increased significantly from 43.0 ± 7.9 mg/dL to 54.9 ± 9.4 mg/dL (p < 0.001), while low-density lipoprotein (LDL) levels decreased from 106.8 ± 33.4 mg/dL to 83.6 ± 27.9 mg/dL ( p = 0.001). Uric acid levels also showed a significant reduction, from 6.3 ± 1.7 mg/dL to 5.3 ± 1.3 mg/dL ( p = 0.003). In contrast, serum albumin levels remained stable, with no significant change from baseline (4.3 ± 0.3 g/dL preoperatively vs. 4.3 ± 0.2 g/dL postoperatively; p = 0.669), suggesting preserved nutritional status following surgery (Table 2 ). Table 2 Metabolic parameters at 12 months after proportional SASI Variables Preoperative Postoperative p value HbA1c (%) 6.5 ± 1.1 5.4 ± 0.4 < 0.001 Albumin (g/dL) 4.3 ± 0.3 4.3 ± 0.2 0.669 Triglyceride (mg/dL) 207.0 ± 131.4 83.3 ± 32.6 < 0.001 Cholesterol (mg/dL) 181.8 ± 36.7 153.7 ± 30.1 0.001 HDL (mg/dL) 43.0 ± 7.9 54.9 ± 9.4 < 0.001 LDL (mg/dL) 106.8 ± 33.4 83.6 ± 27.9 0.001 Uric acid (mg/dL) 6.3 ± 1.7 5.3 ± 1.3 0.003 HDL: high-density lipoproteins, LDL: low-density lipoproteins Hemoglobin levels decreased slightly from 14.0 ± 1.7 g/dL to 13.6 ± 1.8 g/dL, remaining within the normal range and without statistical significance ( p = 0.172). Vitamin B12 levels declined from 585.4 ± 154.6 pg/mL to 503.1 ± 192.5 pg/mL ( p = 0.005); however, no clinical deficiencies were observed. Folate levels showed a minor, non-significant decrease from 11.9 ± 7.8 ng/mL to 10.8 ± 4.4 ng/mL ( p = 0.819), remaining within normal limits. Ferritin levels decreased significantly from 248.5 ± 264.1 ng/mL to 155.7 ± 197.2 ng/mL ( p = 0.001), while serum iron levels remained stable (91.1 ± 46.3 µg/dL preoperatively vs. 90.1 ± 34.7 µg/dL postoperatively; p = 0.594) (Table 3 ). Table 3 Anemia-related biomarkers at 12 months after proportional SASI Variables Preoperative Postoperative p value Hemoglobin (g/dL) 14.0 ± 1.7 13.6 ± 1.8 0.172 Vitamin B12 (pg/mL) 585.4 ± 154.6 503.1 ± 192.5 0.005 Folate (ng/mL) 11.9 ± 7.8 10.8 ± 4.4 0.819 Ferritin (ng/mL) 248.5 ± 264.1 155.7 ± 197.2 0.001 Iron (ug/dL) 91.1 ± 46.3 90.1 ± 34.7 0.594 The severity of fatty liver showed marked improvement at 12 months postoperatively. Preoperatively, the majority of patients (76.7%) had severe fatty liver, whereas postoperatively, most patients (77.8%) had only mild fatty liver. The proportion of patients with moderate or severe fatty liver decreased substantially, from 93.4–14.8%. These changes indicate a significant improvement in hepatic steatosis following proportional SASI (Table 4 ). Table 4 Changes in fatty liver severity Fatty liver Preoperative Postoperative Non 1 (3.3%) 2 (7.4%) Mild 1 (3.3%) 21 (77.8%) Moderate 5 (16.7%) 2 (7.4%) Severe 23 (76.7%) 2 (7.4%) * p < 0.001 As for postoperative complications, two patients (7.4%) developed anemia following the SASI procedure, both of which were confirmed as iron deficiency anemia. The severity of anemia in both cases was mild, with hemoglobin levels remaining above 10 g/dL. Reflux esophagitis (grade B or higher) and marginal ulcers were both assessed by panendoscopy at 12 months postoperatively. Each complication was identified in 2 of the 23 patients who underwent endoscopic evaluation (8.7%). Gallstone formation, assessed via abdominal ultrasonography, was observed in 5 out of 27 patients (18.5%), likely related to rapid postoperative weight loss. (Table 5 ). Table 5 Postoperative complications at 12 months No. of patients Incidence Anemia 2/27 7.4% GERD, grade B or higher 2/23 8.7% Marginal ulcer 2/23 8.7% Gallstone formation 5/27 18.5% GERD: gastroesophageal reflux disease Discussion SASI bypass is a novel bariatric-metabolic procedure designed to enhance weight loss and glycemic control while minimizing complications associated with traditional malabsorptive operations. By combining the restrictive effect of sleeve gastrectomy with the hormonal benefits of ileal bypass, SASI stimulates the secretion of glucagon-like peptide-1 (GLP-1) and peptide YY (PYY), promoting favorable metabolic effects [ 12 ]. This study evaluated a modified, proportional SASI technique in which the bypassed segment was tailored to 40% of each patient’s total small bowel length, rather than applying a fixed length (typically 250–300 cm from the ileocecal valve). To the best of our knowledge, this is the first clinical study to evaluate the efficacy and safety of a proportional SASI bypass based on total small bowel length. Our findings demonstrate that the proportional SASI approach achieves weight loss outcomes comparable to those of fixed-length SASI, while potentially reducing the risk of nutritional complications. At 12 months, the mean percentage of total weight loss (%TWL) was 30%, aligning with previously reported %TWL values of 27.4–35.2% in fixed-length SASI cohorts [ 13 , 14 ]. Metabolic outcomes were also favorable. Among the 12 patients with type 2 diabetes, all experienced either remission or improvement, and 93% of patients with prediabetes achieved normoglycemia. These findings are consistent with the metabolic efficacy demonstrated in fixed-length SASI studies and are comparable to other bypass procedures [ 15 ]. Nutritional safety was a major focus of this study. Shorter common limb lengths in malabsorptive procedures are associated with increased risk of protein malnutrition and hypoalbuminemia [ 16 ]. Previous studies on fixed-length SASI have reported hypoalbuminemia in up to 23% of patients and malnutrition rates as high as 63%, with some requiring parenteral nutrition or surgical reversal [ 9 , 17 , 18 ]. In contrast, no patients in our study developed hypoalbuminemia, and no surgical reversals were required, suggesting that the proportional approach better preserves nutritional integrity. Iron and folate, primarily absorbed in the duodenum and proximal jejunum—segments bypassed in SASI—raise concerns for anemia. Parkitna et al. reported an anemia rate of 25% in SASI patients with a 250 cm common limb, with most anemic patients presenting with normocytic anemia, likely due to combined iron and folate deficiencies [ 8 ]. In our study, the anemia incidence was substantially lower (7.4%), and the cases were mild and effectively managed with oral iron supplementation. Accurate measurement and handling of the small bowel is a critical step during bariatric surgery. However, studies have demonstrated that laparoscopic small bowel length measurement is neither accurate nor precise, with considerable inter-individual differences between the surgeons and trainees [ 19 , 20 ]. A nominal length of 250 cm may therefore differ substantially in actual length and may represent vastly different proportions of total small bowel length across patients. This inconsistency could contribute to the wide variability in malnutrition and anemia rates reported in fixed-length SASI literatures [ 9 , 17 , 18 , 21 – 25 ]. By adopting a proportional approach, we eliminate errors associated with fixed absolute measurements. Although total small bowel length varies between individuals, tailoring the bypass to 40% of the measured length places the anastomosis near the estimated jejunoileal junction. This strategy offers a physiologically rational, individualized solution that balances efficacy with nutritional safety. The incidence of postoperative gallstone formation at 12 months in our study was 18.5%. This is likely attributable to rapid weight loss, a well-established risk factor for cholelithiasis following bariatric surgery [ 26 ]. rior studies have demonstrated that ursodeoxycholic acid (UDCA) significantly reduces the incidence of gallstones in bariatric patients [ 27 , 28 ]. Considering these findings, we plan to revise our clinical protocol to include routine postoperative UDCA prophylaxis to mitigate the risk of gallstone formation. Postoperative gastroesophageal reflux disease (GERD) (grade B or higher) and marginal ulceration each occurred in 8.7% of our cohort at 12 months. Reflux esophagitis was identified by routine endoscopy, despite the absence of symptoms, highlighting the value of surveillance beyond symptom reporting. While sleeve-ileal anastomosis may reduce intragastric pressure and theoretically lower GERD risk, it also exposes the anastomosis to unbuffered gastric acid, potentially increasing marginal ulcer risk. Our ulcer rate was higher than the < 1% reported in literature [ 29 ], though manageable with proton pump inhibitors. This suggests the need for further endoscopic follow-up and consideration of prophylactic acid suppression in select patients. Still, this study has limitations. It was conducted at a single center with a small sample size and a 12-month follow-up. Larger multicenter studies with longer follow-up are needed to evaluate long-term outcomes. A randomized comparison between proportional and fixed-length SASI would also provide stronger evidence. Nonetheless, our findings suggest that the proportional SASI approach offers a favorable balance between efficacy and nutritional safety. Conclusion Proportional SASI, using a bypass length of 40% of the total small bowel, appears to be an effective and safe modification of the standard technique. It provides substantial weight loss and metabolic improvement while maintaining a low incidence of malnutrition, making it a physiologically sound and clinically reasonable alternative to fixed-length SASI. Declarations Ethical approval The study was approved by the Institutional Review Board of Taipei Veterans General Hospital. Informed Consent For this type of study formal consent is not required. Conflict of Interest The authors declare that they have no conflict of interest. Funding The study was funded by Taipei Veterans General Hospital. The sources of funding played no role in the study design, data collection, analysis or interpretation, the writing of the manuscript or the decision to submit for publication. Author Contribution The concept of this study was designed by W.F. and C.W.T.H. and Y.C. collected and analyzed the data.The manuscript was written by T.H. and revised by C.K., K.H. and W.F.All authors reviewed the manuscript. Acknowledgement We thank Miss L.J. Dai (Department of Surgery, Taipei Veterans General Hospital) for assistance with statistics. Data Availability The dataset used and analysed in this study is available from the corresponding author on reasonable request. References Hwang LC, Bai CH, Chen CJ. Prevalence of obesity and metabolic syndrome in Taiwan. J Formos Med Assoc. 2006;105(8):626–35. doi: 10.1016/s0929-6646(09)60161-3 . PubMed PMID: 16935763. Bray GA, Kim KK, Wilding JPH. Obesity: a chronic relapsing progressive disease process. A position statement of the World Obesity Federation. 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Obes Surg. 2003;13(4):625–8. doi: 10.1381/096089203322190862 . PubMed PMID: 12935366. Adams LB, Chang C, Pope J, et al. Randomized, Prospective Comparison of Ursodeoxycholic Acid for the Prevention of Gallstones after Sleeve Gastrectomy. Obes Surg. 2016;26(5):990–4. doi: 10.1007/s11695-015-1858-5 . PubMed PMID: 26342481. Han ML, Lee MH, Lee WJ, et al. Probiotics for gallstone prevention in patients with bariatric surgery: A prospective randomized trial. Asian J Surg. 2022;45(12):2664–9. Epub 20220226. doi: 10.1016/j.asjsur.2022.01.120 . PubMed PMID: 35232647. Emile SH, Mahdy T, Schou C, et al. Systematic review of the outcome of single-anastomosis sleeve ileal (SASI) bypass in treatment of morbid obesity with proportion meta-analysis of improvement in diabetes mellitus. Int J Surg. 2021;92:106024. Epub 20210709. doi: 10.1016/j.ijsu.2021.106024 . PubMed PMID: 34252597. Additional Declarations No competing interests reported. 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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-6899502","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":477068925,"identity":"66fa30cb-b6a8-4324-b571-e59b9518ba29","order_by":0,"name":"Tzu-Ling Huang","email":"","orcid":"","institution":"Taipei Veterans General Hospital","correspondingAuthor":false,"prefix":"","firstName":"Tzu-Ling","middleName":"","lastName":"Huang","suffix":""},{"id":477068926,"identity":"c29eafbc-4d80-4897-8b8d-67d7bd930162","order_by":1,"name":"Yun-Ning Chiu","email":"","orcid":"","institution":"Taipei Medical University-Shuang Ho Hospital","correspondingAuthor":false,"prefix":"","firstName":"Yun-Ning","middleName":"","lastName":"Chiu","suffix":""},{"id":477068927,"identity":"e1c1756d-9afa-4c50-90d9-8734108c8477","order_by":2,"name":"Kuo-Hung Huang","email":"","orcid":"","institution":"Taipei Veterans General Hospital","correspondingAuthor":false,"prefix":"","firstName":"Kuo-Hung","middleName":"","lastName":"Huang","suffix":""},{"id":477068928,"identity":"3940be15-8a81-4ed5-b724-5af627ef9948","order_by":3,"name":"Wen-Liang Fang","email":"","orcid":"","institution":"Taipei Veterans General Hospital","correspondingAuthor":false,"prefix":"","firstName":"Wen-Liang","middleName":"","lastName":"Fang","suffix":""},{"id":477068929,"identity":"84a1cbc7-c662-4050-b4ca-fe9fb8cae1cf","order_by":4,"name":"Chew-Wen Wu","email":"","orcid":"","institution":"Taipei Veterans General Hospital","correspondingAuthor":false,"prefix":"","firstName":"Chew-Wen","middleName":"","lastName":"Wu","suffix":""},{"id":477068930,"identity":"e79757e7-a49e-4945-b33e-82cb5ebe38b4","order_by":5,"name":"Ching-Yun Kung","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA6klEQVRIiWNgGAWjYFACNhBhw8AgQaKWNKAWZpgIM27FSFoOk6CFf0ZamnTBr/OJ86P7jz34wFArZ3CA/xheR0rcSDsmPbPvduLGO4fZDWcwHDc2OMDMhleLgUR6mzRvz21jwxnJbNI8DMcSZzYws90gQss5iJY/xGkBOoznxwE5eQmgFgaGmsR+BgJaJM48S7bmbUiWM5BINjfsMThgzM/MbP4Dnxb+9jTD2zx/7HjkZyQ+e/Cjok6Ojb3xsQE+LQwCCQwMjG1AFx4AxZDBYSJikv8AkPjDwCDfAI7UOkLqR8EoGAWjYAQCAEg/Q8Cgq0mmAAAAAElFTkSuQmCC","orcid":"","institution":"Taipei Veterans General Hospital","correspondingAuthor":true,"prefix":"","firstName":"Ching-Yun","middleName":"","lastName":"Kung","suffix":""}],"badges":[],"createdAt":"2025-06-15 16:53:16","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-6899502/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-6899502/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":85735844,"identity":"d551f5d9-e61b-4d06-b125-ce1d250c078d","added_by":"auto","created_at":"2025-07-01 08:02:53","extension":"jpeg","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":64423,"visible":true,"origin":"","legend":"\u003cp\u003eCorrelation of total weight loss percentage (TWL%) at 12 months with preoperative BMI and total small bowel length\u003cbr\u003e\n \u003cstrong\u003e(A)\u003c/strong\u003e No significant correlation was observed between TWL% and preoperative BMI (R = 0.011).\u003cbr\u003e\n \u003cstrong\u003e(B)\u003c/strong\u003e No significant correlation was observed between TWL% and total small bowel length (R = 0.111).\u003c/p\u003e","description":"","filename":"floatimage1.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-6899502/v1/26a6f114014127cca9366852.jpeg"},{"id":86773571,"identity":"6ff6a39c-eb53-4a79-94be-cbff3a9c237d","added_by":"auto","created_at":"2025-07-15 12:17:08","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":658500,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-6899502/v1/774f9744-b5d2-493d-b176-101c812ffd72.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Proportional Single Anastomosis Sleeve Ileal (SASI) Bypass Based on Total Small Bowel Length: Optimizing Outcomes and Reducing Malnutrition","fulltext":[{"header":"Key Points","content":"\u003col\u003e\n \u003cli\u003eProportional SASI with bypass length of 40% of the total small bowel is an effective yet safe alternative compared to fixed-length SASI.\u003c/li\u003e\n \u003cli\u003eMean total weight loss at 12 months was 30.0%.\u003c/li\u003e\n \u003cli\u003eSignificant metabolic improvements were achieved, including reductions in HbA1c, triglycerides, cholesterol and the severity of fatty liver.\u003c/li\u003e\n \u003cli\u003eNutritional safety was preserved, with no hypoalbuminemia and a low anemia rate (7.4%), suggesting reduced malabsorption risk.\u003c/li\u003e\n\u003c/ol\u003e"},{"header":"Introduction","content":"\u003cp\u003eThe global obesity epidemic has escalated significantly over the past few decades. Since 1990, the prevalence of adult obesity has more than doubled. In 2022, an estimated 2.5\u0026nbsp;billion adults worldwide were classified as overweight, with approximately 890\u0026nbsp;million meeting the criteria for obesity. Taiwan mirrors these global trends, with recent reports indicating that around 16% of adults are living with obesity [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]. This surge is largely driven by shifts toward energy-dense diets, reduced physical activity, and increasing urbanization\u0026mdash;factors that collectively contribute to a heightened risk of chronic conditions such as type 2 diabetes, cardiovascular disease, non-alcoholic fatty liver disease, and various cancers [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eGiven the serious health risks associated with obesity, treatment strategies have evolved beyond lifestyle modification and medication. Bariatric surgery has emerged as the most effective long-term solution for severe obesity. Early procedures, such as the jejunoileal bypass, were largely malabsorptive but carried high complication rates [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e]. By the 1980s, safer options like Roux-en-Y gastric bypass (RYGB) became more popular [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]. The rise of laparoscopic techniques in the 1990s enabled less invasive procedures, including laparoscopic RYGB, adjustable gastric banding, and later, sleeve gastrectomy (SG), which is now widely performed due to its safety and efficacy [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eIn recent years, sleeve-plus procedures have emerged to improve both weight loss and metabolic outcomes [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]. One such innovation is the single anastomosis sleeve ileal (SASI) bypass, which evolved from the original Santoro procedure. In the commonly adopted version introduced by Dr. Mahdy, SASI combines sleeve gastrectomy with a single anastomosis to a loop of the ileum located 250 cm from the ileocecal valve. This hybrid procedure aims to harness both restrictive and hormonal mechanisms to enhance weight loss and glycemic control. SASI has demonstrated promising outcomes, particularly in the management of type 2 diabetes, and appears to reduce certain risks\u0026mdash;such as bile reflux and severe malnutrition\u0026mdash;associated with procedures like RYGB and one anastomosis gastric bypass (OAGB) [\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eHowever, a notable incidence of malnutrition\u0026mdash;including hypoalbuminemia, iron deficiency anemia, and vitamin deficiencies\u0026mdash;has still been reported in published SASI series [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e, \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e]. This suggests that a fixed common limb length of 250 cm may be insufficient for some patients, as it does not account for individual variation in small bowel length.The total small intestine in adults measures approximately 6 meters, with a functional jejunum-to-ileum ratio of about 4:6 [\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e, \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e]. Therefore, we hypothesize that a proportional bypass\u0026mdash;specifically bypassing 40% of the total small bowel length\u0026mdash;may be a more physiologically appropriate approach. This study aims to evaluate the outcomes of this modified SASI procedure at our institution, focusing on weight loss efficacy, metabolic improvements, and nutritional impact.\u003c/p\u003e"},{"header":"Methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003eStudy Design and Patient Selection\u003c/h2\u003e \u003cp\u003eThis was a retrospective study involving 36 patients with obesity who underwent the modified SASI procedure at Taipei Veterans General Hospital between February 2023 and March 2024. Patients who had undergone revisional SASI or were lost to follow-up right after the operation were excluded. Preoperative and postoperative data, regarding weight, metabolic and nutritional parameters, and complications were registered every 3 months after SASI procedure. Abdominal sonography and panendoscopy were performed 12 months after the operation for evaluation.\u003c/p\u003e \u003c/div\u003e\n\u003ch3\u003eSurgical Technique\u003c/h3\u003e\n\u003cp\u003eThe modified SASI procedure consisted of a laparoscopic sleeve gastrectomy (LSG) followed by a proportionally determined sleeve ileal bypass, rather than using a fixed 250 cm common limb. LSG was performed using a 40 Fr bougie as a guide. Stapling began approximately 6 cm from the pylorus and ended 1 cm away from the angle of His. Following LSG, the total small bowel length was measured intraoperatively. A bypass of 40% of the total measured length was performed, corresponding approximately to the estimated junction between the jejunum and ileum. The sleeve-ileal anastomosis was 4 cm in length, created in an antecolic, isoperistaltic manner on the greater curvature side of the antrum. The anastomotic entry site was closed in two layers using a continuous barbed suture.\u003c/p\u003e\n\u003ch3\u003eOutcome Measurement\u003c/h3\u003e\n\u003cp\u003eThe primary outcome was the percentage of total body weight loss (TWL%) at 12 months postoperatively. Secondary outcomes included metabolic changes\u0026mdash;specifically glycemic control, lipid profiles, uric acid levels, and albumin levels\u0026mdash;the incidence of anemia, changes in the degree of fatty liver, and postoperative complications.\u003c/p\u003e \u003cdiv id=\"Sec6\" class=\"Section2\"\u003e \u003ch2\u003eStatistical Analysis\u003c/h2\u003e \u003cp\u003eDescriptive statistics were used to summarize baseline characteristics and postoperative outcomes. Changes in continuous variables over time were analyzed using the nonparametric Wilcoxon signed-rank test. A \u003cem\u003ep\u003c/em\u003e-value of \u0026lt;\u0026thinsp;0.05 was considered statistically significant.\u003c/p\u003e \u003c/div\u003e"},{"header":"Results","content":"\u003cp\u003eA total of 36 patients underwent the modified SASI bypass between February 2023 and March 2024 at Taipei Veterans General Hospital. Two patients were excluded due to prior bariatric surgery, and four were lost to follow-up. A total of 30 patients were included in the study. The mean age was 40.0\u0026thinsp;\u0026plusmn;\u0026thinsp;8.2 years (range: 22\u0026ndash;58), with an equal distribution of male and female participants (15 each, 50%). Five patients (16.7%) were active smokers. The mean preoperative body weight was 124.3\u0026thinsp;\u0026plusmn;\u0026thinsp;26.3 kg, and the mean body mass index (BMI) was 43.2\u0026thinsp;\u0026plusmn;\u0026thinsp;6.6 kg/m\u0026sup2;. Regarding comorbidities, 12 patients (40%) had type 2 diabetes mellitus, 18 (60%) had hypertension, and 17 (56.7%) had hyperlipidemia. The mean total small intestine length measured intraoperatively was 817\u0026thinsp;\u0026plusmn;\u0026thinsp;191 cm, and the mean bypassed length was 328\u0026thinsp;\u0026plusmn;\u0026thinsp;79 cm, corresponding to 40% of the total length. Preoperative endoscopy showed that 7 patients (23.3%) had no reflux esophagitis, 22 (73.3%) had grade A esophagitis, and 1 patient (3.3%) had grade B esophagitis. Assessment of fatty liver revealed that 23 patients (76.7%) had severe fatty liver, 5 (16.7%) had moderate fatty liver, and 1 patient each (3.3%) had mild or no fatty liver (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003ePatient demographics\u003c/p\u003e \u003c/div\u003e \u003c/caption\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=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eVariables\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"2\" nameend=\"c3\" namest=\"c2\"\u003e \u003cp\u003eValue\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c2\" namest=\"c1\"\u003e \u003cp\u003eAge (years)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e40.0\u0026thinsp;\u0026plusmn;\u0026thinsp;8.2 (22\u0026ndash;58)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c2\" namest=\"c1\"\u003e \u003cp\u003eSex\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c2\" namest=\"c1\"\u003e \u003cp\u003eMale\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e15 (50%)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c2\" namest=\"c1\"\u003e \u003cp\u003eFemale\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e15 (50%)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c2\" namest=\"c1\"\u003e \u003cp\u003eSmoker\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e5 (16.7%)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c2\" namest=\"c1\"\u003e \u003cp\u003eBody weight at operation (kg)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e124.3\u0026thinsp;\u0026plusmn;\u0026thinsp;26.3\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c2\" namest=\"c1\"\u003e \u003cp\u003eBMI at operation (kg/m\u003csup\u003e2\u003c/sup\u003e)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e43.2\u0026thinsp;\u0026plusmn;\u0026thinsp;6.6\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c2\" namest=\"c1\"\u003e \u003cp\u003eDiabetes mellitus\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e12 (40%)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c2\" namest=\"c1\"\u003e \u003cp\u003eHypertension\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e18 (60%)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c2\" namest=\"c1\"\u003e \u003cp\u003eHyperlipidemia\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e17 (56.7%)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c2\" namest=\"c1\"\u003e \u003cp\u003eSmall intestine length (cm)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c2\" namest=\"c1\"\u003e \u003cp\u003eTotal length\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e817\u0026thinsp;\u0026plusmn;\u0026thinsp;191\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c2\" namest=\"c1\"\u003e \u003cp\u003eBypassed length\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e328\u0026thinsp;\u0026plusmn;\u0026thinsp;79\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c2\" namest=\"c1\"\u003e \u003cp\u003eGERD\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c2\" namest=\"c1\"\u003e \u003cp\u003eNegative\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e7 (23.3%)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c2\" namest=\"c1\"\u003e \u003cp\u003eGrade A\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e22 (73.3%)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c2\" namest=\"c1\"\u003e \u003cp\u003eGrade B\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1 (3.3%)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c2\" namest=\"c1\"\u003e \u003cp\u003eFatty liver\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c2\" namest=\"c1\"\u003e \u003cp\u003eNon\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1 (3.3%)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c2\" namest=\"c1\"\u003e \u003cp\u003eMild\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1 (3.3%)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c2\" namest=\"c1\"\u003e \u003cp\u003eModerate\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e5 (16.7%)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c2\" namest=\"c1\"\u003e \u003cp\u003eSevere\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e23 (76.7%)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"3\" nameend=\"c3\" namest=\"c1\"\u003e \u003cp\u003eGERD: gastroesophageal reflux disease\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eThe follow-up rate was 96.7% at 3 months, 93.3% at 6 months, and 90.0% at 12 months. Among the 27 patients who completed 12 months of follow-up, the mean total weight loss percentage (TWL%) was 30.0\u0026thinsp;\u0026plusmn;\u0026thinsp;7.4%. The mean body mass index (BMI) decreased from 43.2\u0026thinsp;\u0026plusmn;\u0026thinsp;6.6 kg/m\u0026sup2; preoperatively to 30.5\u0026thinsp;\u0026plusmn;\u0026thinsp;5.7 kg/m\u0026sup2; at 12 months. Adequate weight loss (defined as TWL% \u0026gt; 20%) was achieved in 25 of the 27 patients (92.6%). Correlation analyses were performed to evaluate the relationship between total weight loss percentage (TWL%) and both preoperative BMI and total small bowel length. No significant linear correlation was found between preoperative BMI and TWL% (correlation coefficient R\u0026thinsp;=\u0026thinsp;0.011; Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eA). Similarly, there was no significant correlation between total small bowel length and TWL% (R\u0026thinsp;=\u0026thinsp;0.111; Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eB).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eAt 12 months postoperatively, improvements in metabolic parameters were observed. Mean HbA1c decreased from 6.5\u0026thinsp;\u0026plusmn;\u0026thinsp;1.1% preoperatively to 5.4\u0026thinsp;\u0026plusmn;\u0026thinsp;0.4% (\u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.001). Among the 12 patients with type 2 diabetes, 7 (58%) achieved diabetes remission, defined as HbA1c\u0026thinsp;\u0026lt;\u0026thinsp;6% without the need for antidiabetic medications, while the remaining 5 patients (42%) showed improved glycemic control. Serum triglyceride levels decreased markedly from 207.0\u0026thinsp;\u0026plusmn;\u0026thinsp;131.4 mg/dL to 83.3\u0026thinsp;\u0026plusmn;\u0026thinsp;32.6 mg/dL (\u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.001), and total cholesterol levels declined from 181.8\u0026thinsp;\u0026plusmn;\u0026thinsp;36.0 mg/dL to 153.7\u0026thinsp;\u0026plusmn;\u0026thinsp;30.1 mg/dL (\u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.001). High-density lipoprotein (HDL) levels increased significantly from 43.0\u0026thinsp;\u0026plusmn;\u0026thinsp;7.9 mg/dL to 54.9\u0026thinsp;\u0026plusmn;\u0026thinsp;9.4 mg/dL (p\u0026thinsp;\u0026lt;\u0026thinsp;0.001), while low-density lipoprotein (LDL) levels decreased from 106.8\u0026thinsp;\u0026plusmn;\u0026thinsp;33.4 mg/dL to 83.6\u0026thinsp;\u0026plusmn;\u0026thinsp;27.9 mg/dL (\u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.001). Uric acid levels also showed a significant reduction, from 6.3\u0026thinsp;\u0026plusmn;\u0026thinsp;1.7 mg/dL to 5.3\u0026thinsp;\u0026plusmn;\u0026thinsp;1.3 mg/dL (\u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.003). In contrast, serum albumin levels remained stable, with no significant change from baseline (4.3\u0026thinsp;\u0026plusmn;\u0026thinsp;0.3 g/dL preoperatively vs. 4.3\u0026thinsp;\u0026plusmn;\u0026thinsp;0.2 g/dL postoperatively; \u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.669), suggesting preserved nutritional status following surgery (Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eMetabolic parameters at 12 months after proportional SASI\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"4\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eVariables\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003ePreoperative\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003ePostoperative\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cem\u003ep\u003c/em\u003e value\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eHbA1c (%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e6.5\u0026thinsp;\u0026plusmn;\u0026thinsp;1.1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e5.4\u0026thinsp;\u0026plusmn;\u0026thinsp;0.4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAlbumin (g/dL)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e4.3\u0026thinsp;\u0026plusmn;\u0026thinsp;0.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e4.3\u0026thinsp;\u0026plusmn;\u0026thinsp;0.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.669\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eTriglyceride (mg/dL)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e207.0\u0026thinsp;\u0026plusmn;\u0026thinsp;131.4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e83.3\u0026thinsp;\u0026plusmn;\u0026thinsp;32.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCholesterol (mg/dL)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e181.8\u0026thinsp;\u0026plusmn;\u0026thinsp;36.7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e153.7\u0026thinsp;\u0026plusmn;\u0026thinsp;30.1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.001\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eHDL (mg/dL)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e43.0\u0026thinsp;\u0026plusmn;\u0026thinsp;7.9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e54.9\u0026thinsp;\u0026plusmn;\u0026thinsp;9.4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eLDL (mg/dL)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e106.8\u0026thinsp;\u0026plusmn;\u0026thinsp;33.4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e83.6\u0026thinsp;\u0026plusmn;\u0026thinsp;27.9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.001\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eUric acid (mg/dL)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e6.3\u0026thinsp;\u0026plusmn;\u0026thinsp;1.7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e5.3\u0026thinsp;\u0026plusmn;\u0026thinsp;1.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.003\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"4\" nameend=\"c4\" namest=\"c1\"\u003e \u003cp\u003eHDL: high-density lipoproteins, LDL: low-density lipoproteins\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eHemoglobin levels decreased slightly from 14.0\u0026thinsp;\u0026plusmn;\u0026thinsp;1.7 g/dL to 13.6\u0026thinsp;\u0026plusmn;\u0026thinsp;1.8 g/dL, remaining within the normal range and without statistical significance (\u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.172). Vitamin B12 levels declined from 585.4\u0026thinsp;\u0026plusmn;\u0026thinsp;154.6 pg/mL to 503.1\u0026thinsp;\u0026plusmn;\u0026thinsp;192.5 pg/mL (\u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.005); however, no clinical deficiencies were observed. Folate levels showed a minor, non-significant decrease from 11.9\u0026thinsp;\u0026plusmn;\u0026thinsp;7.8 ng/mL to 10.8\u0026thinsp;\u0026plusmn;\u0026thinsp;4.4 ng/mL (\u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.819), remaining within normal limits. Ferritin levels decreased significantly from 248.5\u0026thinsp;\u0026plusmn;\u0026thinsp;264.1 ng/mL to 155.7\u0026thinsp;\u0026plusmn;\u0026thinsp;197.2 ng/mL (\u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.001), while serum iron levels remained stable (91.1\u0026thinsp;\u0026plusmn;\u0026thinsp;46.3 \u0026micro;g/dL preoperatively vs. 90.1\u0026thinsp;\u0026plusmn;\u0026thinsp;34.7 \u0026micro;g/dL postoperatively; \u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.594) (Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab3\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 3\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eAnemia-related biomarkers at 12 months after proportional SASI\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"4\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eVariables\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003ePreoperative\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003ePostoperative\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cem\u003ep\u003c/em\u003e value\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eHemoglobin (g/dL)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e14.0\u0026thinsp;\u0026plusmn;\u0026thinsp;1.7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e13.6\u0026thinsp;\u0026plusmn;\u0026thinsp;1.8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.172\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eVitamin B12 (pg/mL)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e585.4\u0026thinsp;\u0026plusmn;\u0026thinsp;154.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e503.1\u0026thinsp;\u0026plusmn;\u0026thinsp;192.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.005\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eFolate (ng/mL)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e11.9\u0026thinsp;\u0026plusmn;\u0026thinsp;7.8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e10.8\u0026thinsp;\u0026plusmn;\u0026thinsp;4.4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.819\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eFerritin (ng/mL)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e248.5\u0026thinsp;\u0026plusmn;\u0026thinsp;264.1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e155.7\u0026thinsp;\u0026plusmn;\u0026thinsp;197.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.001\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eIron (ug/dL)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e91.1\u0026thinsp;\u0026plusmn;\u0026thinsp;46.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e90.1\u0026thinsp;\u0026plusmn;\u0026thinsp;34.7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.594\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eThe severity of fatty liver showed marked improvement at 12 months postoperatively. Preoperatively, the majority of patients (76.7%) had severe fatty liver, whereas postoperatively, most patients (77.8%) had only mild fatty liver. The proportion of patients with moderate or severe fatty liver decreased substantially, from 93.4\u0026ndash;14.8%. These changes indicate a significant improvement in hepatic steatosis following proportional SASI (Table\u0026nbsp;\u003cspan refid=\"Tab4\" class=\"InternalRef\"\u003e4\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab4\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 4\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eChanges in fatty liver severity\u003c/p\u003e \u003c/div\u003e \u003c/caption\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=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eFatty liver\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003ePreoperative\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003ePostoperative\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eNon\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1 (3.3%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e2 (7.4%)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMild\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1 (3.3%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e21 (77.8%)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eModerate\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e5 (16.7%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e2 (7.4%)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSevere\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e23 (76.7%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e2 (7.4%)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"3\" nameend=\"c3\" namest=\"c1\"\u003e \u003cp\u003e*\u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.001\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eAs for postoperative complications, two patients (7.4%) developed anemia following the SASI procedure, both of which were confirmed as iron deficiency anemia. The severity of anemia in both cases was mild, with hemoglobin levels remaining above 10 g/dL. Reflux esophagitis (grade B or higher) and marginal ulcers were both assessed by panendoscopy at 12 months postoperatively. Each complication was identified in 2 of the 23 patients who underwent endoscopic evaluation (8.7%). Gallstone formation, assessed via abdominal ultrasonography, was observed in 5 out of 27 patients (18.5%), likely related to rapid postoperative weight loss. (Table\u0026nbsp;\u003cspan refid=\"Tab5\" class=\"InternalRef\"\u003e5\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab5\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 5\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003ePostoperative complications at 12 months\u003c/p\u003e \u003c/div\u003e \u003c/caption\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=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eNo. of patients\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eIncidence\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAnemia\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e2/27\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e7.4%\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eGERD, grade B or higher\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e2/23\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e8.7%\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMarginal ulcer\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e2/23\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e8.7%\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eGallstone formation\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e5/27\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e18.5%\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"3\" nameend=\"c3\" namest=\"c1\"\u003e \u003cp\u003eGERD: gastroesophageal reflux disease\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e"},{"header":"Discussion","content":"\u003cp\u003eSASI bypass is a novel bariatric-metabolic procedure designed to enhance weight loss and glycemic control while minimizing complications associated with traditional malabsorptive operations. By combining the restrictive effect of sleeve gastrectomy with the hormonal benefits of ileal bypass, SASI stimulates the secretion of glucagon-like peptide-1 (GLP-1) and peptide YY (PYY), promoting favorable metabolic effects [\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eThis study evaluated a modified, proportional SASI technique in which the bypassed segment was tailored to 40% of each patient\u0026rsquo;s total small bowel length, rather than applying a fixed length (typically 250\u0026ndash;300 cm from the ileocecal valve). To the best of our knowledge, this is the first clinical study to evaluate the efficacy and safety of a proportional SASI bypass based on total small bowel length.\u003c/p\u003e \u003cp\u003eOur findings demonstrate that the proportional SASI approach achieves weight loss outcomes comparable to those of fixed-length SASI, while potentially reducing the risk of nutritional complications. At 12 months, the mean percentage of total weight loss (%TWL) was 30%, aligning with previously reported %TWL values of 27.4\u0026ndash;35.2% in fixed-length SASI cohorts [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e, \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eMetabolic outcomes were also favorable. Among the 12 patients with type 2 diabetes, all experienced either remission or improvement, and 93% of patients with prediabetes achieved normoglycemia. These findings are consistent with the metabolic efficacy demonstrated in fixed-length SASI studies and are comparable to other bypass procedures [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eNutritional safety was a major focus of this study. Shorter common limb lengths in malabsorptive procedures are associated with increased risk of protein malnutrition and hypoalbuminemia [\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e]. Previous studies on fixed-length SASI have reported hypoalbuminemia in up to 23% of patients and malnutrition rates as high as 63%, with some requiring parenteral nutrition or surgical reversal [\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e, \u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e, \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e]. In contrast, no patients in our study developed hypoalbuminemia, and no surgical reversals were required, suggesting that the proportional approach better preserves nutritional integrity.\u003c/p\u003e \u003cp\u003eIron and folate, primarily absorbed in the duodenum and proximal jejunum\u0026mdash;segments bypassed in SASI\u0026mdash;raise concerns for anemia. Parkitna et al. reported an anemia rate of 25% in SASI patients with a 250 cm common limb, with most anemic patients presenting with normocytic anemia, likely due to combined iron and folate deficiencies [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e]. In our study, the anemia incidence was substantially lower (7.4%), and the cases were mild and effectively managed with oral iron supplementation.\u003c/p\u003e \u003cp\u003eAccurate measurement and handling of the small bowel is a critical step during bariatric surgery. However, studies have demonstrated that laparoscopic small bowel length measurement is neither accurate nor precise, with considerable inter-individual differences between the surgeons and trainees [\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e, \u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e]. A nominal length of 250 cm may therefore differ substantially in actual length and may represent vastly different proportions of total small bowel length across patients. This inconsistency could contribute to the wide variability in malnutrition and anemia rates reported in fixed-length SASI literatures [\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e, \u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e, \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e, \u003cspan additionalcitationids=\"CR22 CR23 CR24\" citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e]. By adopting a proportional approach, we eliminate errors associated with fixed absolute measurements. Although total small bowel length varies between individuals, tailoring the bypass to 40% of the measured length places the anastomosis near the estimated jejunoileal junction. This strategy offers a physiologically rational, individualized solution that balances efficacy with nutritional safety.\u003c/p\u003e \u003cp\u003eThe incidence of postoperative gallstone formation at 12 months in our study was 18.5%. This is likely attributable to rapid weight loss, a well-established risk factor for cholelithiasis following bariatric surgery [\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e]. rior studies have demonstrated that ursodeoxycholic acid (UDCA) significantly reduces the incidence of gallstones in bariatric patients [\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e, \u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e]. Considering these findings, we plan to revise our clinical protocol to include routine postoperative UDCA prophylaxis to mitigate the risk of gallstone formation.\u003c/p\u003e \u003cp\u003ePostoperative gastroesophageal reflux disease (GERD) (grade B or higher) and marginal ulceration each occurred in 8.7% of our cohort at 12 months. Reflux esophagitis was identified by routine endoscopy, despite the absence of symptoms, highlighting the value of surveillance beyond symptom reporting. While sleeve-ileal anastomosis may reduce intragastric pressure and theoretically lower GERD risk, it also exposes the anastomosis to unbuffered gastric acid, potentially increasing marginal ulcer risk. Our ulcer rate was higher than the \u0026lt;\u0026thinsp;1% reported in literature [\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e], though manageable with proton pump inhibitors. This suggests the need for further endoscopic follow-up and consideration of prophylactic acid suppression in select patients.\u003c/p\u003e \u003cp\u003eStill, this study has limitations. It was conducted at a single center with a small sample size and a 12-month follow-up. Larger multicenter studies with longer follow-up are needed to evaluate long-term outcomes. A randomized comparison between proportional and fixed-length SASI would also provide stronger evidence. Nonetheless, our findings suggest that the proportional SASI approach offers a favorable balance between efficacy and nutritional safety.\u003c/p\u003e"},{"header":"Conclusion","content":"\u003cp\u003eProportional SASI, using a bypass length of 40% of the total small bowel, appears to be an effective and safe modification of the standard technique. It provides substantial weight loss and metabolic improvement while maintaining a low incidence of malnutrition, making it a physiologically sound and clinically reasonable alternative to fixed-length SASI.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e \u003cstrong\u003eEthical approval\u003c/strong\u003e \u003cp\u003e The study was approved by the Institutional Review Board of Taipei Veterans General Hospital.\u003c/p\u003e \u003c/p\u003e \u003cp\u003e \u003cstrong\u003eInformed Consent\u003c/strong\u003e \u003cp\u003eFor this type of study formal consent is not required.\u003c/p\u003e \u003c/p\u003e\u003cp\u003e \u003ch2\u003eConflict of Interest\u003c/h2\u003e \u003cp\u003eThe authors declare that they have no conflict of interest.\u003c/p\u003e \u003c/p\u003e\u003ch2\u003eFunding\u003c/h2\u003e \u003cp\u003eThe study was funded by Taipei Veterans General Hospital. The sources of funding played no role in the study design, data collection, analysis or interpretation, the writing of the manuscript or the decision to submit for publication.\u003c/p\u003e\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eThe concept of this study was designed by W.F. and C.W.T.H. and Y.C. collected and analyzed the data.The manuscript was written by T.H. and revised by C.K., K.H. and W.F.All authors reviewed the manuscript.\u003c/p\u003e\u003ch2\u003eAcknowledgement\u003c/h2\u003e\u003cp\u003eWe thank Miss L.J. Dai (Department of Surgery, Taipei Veterans General Hospital) for assistance with statistics.\u003c/p\u003e\u003ch2\u003eData Availability\u003c/h2\u003e\u003cp\u003eThe dataset used and analysed in this study is available from the corresponding author on reasonable request.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eHwang LC, Bai CH, Chen CJ. Prevalence of obesity and metabolic syndrome in Taiwan. 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Systematic review of the outcome of single-anastomosis sleeve ileal (SASI) bypass in treatment of morbid obesity with proportion meta-analysis of improvement in diabetes mellitus. Int J Surg. 2021;92:106024. Epub 20210709. doi: \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1016/j.ijsu.2021.106024\u003c/span\u003e\u003cspan address=\"10.1016/j.ijsu.2021.106024\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e. PubMed PMID: 34252597.\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"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":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"single anastomosis sleeve ileal bypass (SASI), proportional bypass, bariatric surgery","lastPublishedDoi":"10.21203/rs.3.rs-6899502/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-6899502/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003e\u003cem\u003eIntroduction\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003eSingle anastomosis sleeve ileal (SASI) bypass is a novel bariatric procedure typically performed with a fixed common limb of 250 cm. However, this approach may increase the risk of malnutrition. In this study, we modified the bypass length to 40% of the total small bowel length and evaluated the efficacy and safety of this proportional SASI technique.\u003c/p\u003e\n\u003cp\u003e\u003cem\u003eMethods\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003eIn this study, patients with obesity who underwent proportional SASI between February 2023 and March 2024 were enrolled. Of 36 patients, 30 were included in the final analysis after excluding those with revisional surgery or loss to follow-up. The primary outcome was total weight loss (TWL) at 12 months. Secondary outcomes included changes in nutritional markers and postoperative complications.\u003c/p\u003e\n\u003cp\u003e\u003cem\u003eResults\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003eThe cohort had a male-to-female ratio of 1:1, with a mean age of 40 years and mean preoperative BMI of 43.2 kg/m². The mean TWL was 30.0% at 12 months. Hemoglobin decreased slightly (14.1 to 13.7 g/dL, \u003cem\u003ep\u003c/em\u003e = 0.121), while albumin remained stable at 4.3 g/dL. Significant improvements were observed in HbA1c (6.5% to 5.4%, \u003cem\u003ep \u003c/em\u003e\u0026lt;0.001), triglycerides (207.0 to 83.3 mg/dL, \u003cem\u003ep \u003c/em\u003e\u0026lt;0.001), and total cholesterol (181.8 to 153.7 mg/dL, \u003cem\u003ep\u003c/em\u003e\u0026lt;0.001). The incidence of gallstone formation was 18.5%, while reflux esophagitis (grade B or higher) and marginal ulcers were both 8.7% at 1 year postoperatively.\u003c/p\u003e\n\u003cp\u003e\u003cem\u003eConclusions\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003eSASI with proportional bypass appears to be an effective and safe procedure. It achieves substantial weight loss and metabolic improvement while maintaining nutritional stability.\u003c/p\u003e","manuscriptTitle":"Proportional Single Anastomosis Sleeve Ileal (SASI) Bypass Based on Total Small Bowel Length: Optimizing Outcomes and Reducing Malnutrition","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-07-01 08:02:48","doi":"10.21203/rs.3.rs-6899502/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"a05f6cc4-2380-4f9a-b9ba-ae573a3dfdf1","owner":[],"postedDate":"July 1st, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2025-07-15T12:08:52+00:00","versionOfRecord":[],"versionCreatedAt":"2025-07-01 08:02:48","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-6899502","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-6899502","identity":"rs-6899502","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}