Gastric volumetric filling capacity before and after Sleeve Gastrectomy: An MRI and Biomechanical Study.

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François Fournier, Catherine Masson, David Ben Dahan, Lauriane Pini, and 8 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-8402831/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 01 Apr, 2026 Read the published version in Obesity Surgery → Version 1 posted 12 You are reading this latest preprint version Abstract Introduction The stomach exhibits substantial expansion capacity to accommodate food ingestion, yet regional deformation profiles (fundus, corpus, antrum) remain poorly characterised. Laparoscopic sleeve gastrectomy (LSG) drastically reduces anatomical gastric volume, but its impact on accommodation capacity and the underlying mechanical determinants are unknown. This study investigated the correlation between regional gastric tissue mechanics and MRI-measured volumetric changes before and after LSG. Methods In a prospective, single-centre study, nine patients with severe obesity (preoperative BMI 42.2 ± 4.1 kg/m²) underwent MRI-based gastric volumetry empty/full ( ad libidum , up to 500mL) before and 1–2 months after LSG. Resected fundus and corpus tissue samples were subjected to biaxial tensile testing to quantify passive mechanical properties. Correlations between regional tissue stretch capacity and volumetric expansion were analysed. Results After water ingestion, preoperative volume increased from 203 ± 68 cm³ (empty) to 604 ± 141 cm³ (full). Tissue mechanical extensibility was greater (Sign test, p = 0.02) in the fundus (2.67 ± 0.84) than corpus (2.23 ± 0.31). Fundus extensibility strongly correlated with regional volume accommodation (ρ = 0.77, p = 0.015). Post-LSG, sleeve volumes decreased to 73 ± 18 cm³ (empty) and 120 ± 44 cm³ (full), representing 62% and 81% reductions respectively. Volume loss predominantly affected the fundus. Postoperatively, no correlation was found between tissue mechanics and gastric expansion. Conclusion Pre-LSG, fundic tissue compliance strongly determines gastric accommodation capacity. LSG reduces anatomical volume by two-thirds and functional capacity by three-quarters, with early postoperative expansion independent of intrinsic tissue mechanical properties. Sleeve gastrectomy Gastric biomechanics Biaxial tensile testing Magnetic resonance imaging Gastric accommodation Tissue mechanics Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Key Points • Fundus shows higher extensibility than corpus with great inter-patient variability • Empty sleeve volumes dropped to 36% (19% at satiety) of pre-LSG capacity • Fundus tissue compliance strongly correlates with gastric accommodation pre-LSG • Mechanics-volume correlation disappears post-LSG, suggesting geometric control 1. Introduction Laparoscopic Sleeve Gastrectomy (LSG) is currently the most frequently performed bariatric procedure worldwide, valued for its reproducibility and effectiveness in inducing weight loss and associated medical problems remission [ 1 ]. While originally conceptualised as a purely restrictive procedure, its mechanisms are now understood to be multifactorial, involving accelerated gastric emptying, loss of the fundal reservoir, and significant hormonal modulation [ 2 , 3 ]. Advances in imaging have enabled detailed characterisation of these morphological and functional changes. Studies using Computed Tomography (CT) or Magnetic Resonance Imaging (MRI) have documented substantial reductions in total gastric capacity, typically reported between 75–80%, alongside resection of the fundus and corpus, sparing most of the antrum to maintain pyloric function [ 4 – 6 ] Dynamic imaging has further confirmed accelerated early-phase gastric transit kinetics post-LSG [ 4 , 7 ]. However, reported volumetric reductions vary considerably across studies, reflecting a fundamental methodological challenge, with currently no standardised reference method (upper GI contrast series, CT, or MRI) nor consensus imaging protocol for gastric volume assessment. Since the stomach is a highly compliant reservoir, measured volumes are strongly influenced by the degree of luminal distension at the time of imaging, limiting direct comparisons across studies. More critically, gastric accommodation capacity itself, defined as the stomach's ability to expand in response to filling, remains poorly characterised despite being a key determinant of post-operative food restriction, eating comfort, and potentially clinical outcomes. This accommodation capacity depends on two interrelated structural factors: the resting geometry of the gastric pouch (its fasting volume) and the intrinsic mechanical properties of the gastric wall (its extensibility and stiffness). Despite volumetric and functional insights, a critical gap remains: the relationship between intrinsic gastric wall mechanics and organ-level accommodation has never been directly investigated in humans undergoing LSG. The stomach is a complex, hyperelastic, and anisotropic organ whose accommodation reflex is dictated not only by neural control but fundamentally by the intrinsic passive mechanical properties of its wall, such as stiffness and extensibility [ 8 , 9 ]. Most existing mechanical characterisation on gastric samples relies on porcine models or preserved human tissue (cadaveric or frozen) [ 10 – 13 ], which fail to represent the in vivo behaviour of fresh tissue from patients with obesity. Crucially, no study has yet correlated the mechanical properties of the resected tissue with the same patient's functional capacity. Understanding this "structure-function" relationship is key to identifying the biomechanical determinants of gastric accommodation and explaining inter-patient variability in post-operative outcomes including weight loss, complications, and quality of life. This study therefore aims to bridge the gap between clinical volumetry and tissue biomechanics through a prospective, longitudinal, and paired design. Specifically, we quantified regional gastric volumes and emptying kinetics using a standardised MRI protocol in patients with severe obesity, both before and after LSG. In parallel, we characterised the passive mechanical properties of the fresh resected tissue (fundus and corpus) from the same patients via biaxial tensile testing immediately following surgery, to investigate the correlation between intrinsic tissue extensibility and macroscopic volumetric expansion. 2. Materials and Methods 2.1. Study Design This prospective, longitudinal, single-centre study was conducted at [institution blinded for review] following ethics committee approval [ethics approval number blinded for review]. Written informed consent was obtained from all participants. The study followed a paired design in which each patient served as their own control, undergoing MRI volumetry before and 1-2 months after surgery, with ex vivo mechanical testing of their resected gastric tissue performed on the day of surgery (Fig1). 2.2. Participants and surgery Nine patients scheduled for primary LSG were prospectively included (8 women, 1 man, mean age 37 ± 13 years, preoperative BMI 42.2 ± 4.1 kg/m²). Demographics are detailed in Table 1. One patient withdrew from post-operative follow-up but consented to retention of their preoperative data, which were included in baseline analyses (n=9) but excluded from paired comparisons (n=8). All procedures followed a standardised laparoscopic technique consisting of greater curvature mobilisation from antrum to left diaphragmatic crus, with gastric calibration over a 38-Fr bougie (MID-TUBE MID130, Médical Innovation Développement). Stapling was performed using reinforced (Seamguard, Gore) 60-mm violet cartridges (GIA stapler, Medtronic), starting 4-6 cm proximal to the pylorus and extending to within 1–2 cm of the gastro-oesophageal junction. Table 1 . Included patient demographic data with sex, preoperative BMI (kg/m²), age and associated medical problems (PCOS : Polycystic ovary syndrome, MASH : metabolic-associated steatohepatitis). $ symbol is used to denote which patient was lost in follow-up. Sex (F/M) Preoperative BMI (kg/m²) Associated medical problems Age (years) F $ 39.3 Sleep apnoea, Type 2 diabetes, MASH, PCOS 66 F 42 MASH, Sleep apnoea 35 F 42.1 Sleep apnoea 39 F 42.3 PCOS, MASH 24 F 40.5 PCOS, Sleep apnoea 26 F 37.4 Dyslipidaemia, PCOS 30 F 37.6 Type 2 diabetes, Sleep apnoea 48 M 49.2 Sleep apnoea 38 F 49 MASH 27 2.3. Imaging Protocol and post processing MRI was performed using a 3T system (MAGNETOM Vida, Siemens Healthineers) at [institution blinded for review] after 6-hour fasting. Patients first underwent baseline scanning in the empty state, then ingested water ad libitum (max 500 cm³) until satiety, followed by a second MRI acquisition at the full state . Anatomical T2-weighted images were acquired using a Half-Fourier Acquisition Single-shot Turbo spin Echo (HASTE) sequence in the axial plane, optimised for rapid abdominal imaging during breath-holds. Typical acquisition parameters were: repetition time (TR) ≈ 700 ms, echo time (TE) = 64 ms, flip angle 106°, and a slice thickness of 4 mm (with 10% gap to minimize signal cross-talk), with an in-plane resolution ranging from 0.5 × 0.5 mm² to 0.8 × 0.8 mm². This high-resolution, motion-free imaging allowed for precise delineation of the gastric wall. Post-operative MRI (1-2 months) replicated the identical protocol. DICOM images were imported into 3D Slicer (v5.8.1). Gastric segmentation combined intensity-based thresholding with manual correction, capturing total gastric volume (wall, luminal fluid, gas) as a functional measure of capacity. Three-dimensional meshes were generated for volume computation. Regional partitioning (fundus, corpus, antrum) was performed using manually positioned anatomical landmarks (gastroesophageal junction, gastroduodenal junction, and angularis incisura) following the methodology detailed in Supplementary Material S1. Two cutting planes separated the three regions, see Fig2a. Regional volumes were computed for empty and full states. The primary functional metric was expansion capacity (ΔV), defined as ΔV = V full - V empty , representing the stomach's ability to accommodate ingested fluid. 2.4. Mechanical testing protocol Immediately post-resection, gastric specimens were retrieved. Custom 3D-printed guides and cork plates were used to preserve the in vivo mechanical state without pre-stretching. Square samples (20 × 20 mm) were excised from fundus and corpus regions (antrum preserved in patients). Samples were kept hydrated in PBS at 4°C and tested within 6 hours. Biaxial tensile tests were performed on a custom-built planar testing machine with 50 N load cells. Equibiaxial extension (1:1 ratio) was applied at 0.1 mm/s until rupture. Damage detection used classical bilinear fitting methods [14,15]. The primary mechanical outcome used in this study was area stretch at damage ( , with and the stretches before sample damage in each traction directions), representing tissue's capacity for two-dimensional elongation before irreversible injury. Illustration of a mounted specimen before biaxial tensile test and an example of stress-stretch curve with bilinear fitting are presented Fig2b. 2.5. Statistical Analysis Analyses were performed using Python 3.11.5 (SciPy, Pandas, Statsmodels, Matplotlib) with p < 0.05. Statistical assumptions for each test were verified prior to application. Non-parametric methods were used given the small sample size (n=9 baseline, n=8 paired). Paired comparisons used Wilcoxon signed-rank test. Regional mechanical comparisons (fundus vs. corpus) used Wilcoxon signed-rank and Sign tests (the latter to assess within-patient mechanical hierarchy). To investigate the relationship between tissue mechanical properties (area stretch at damage, λ A ) and volumetric expansion capacity (ΔV), Spearman's rank correlation coefficient (ρ) was computed at the patient level for each region. Data were visualized using box plots with individual patient trajectories (spaghetti plot). 3. Results 3.1. Preoperative gastric morphology and function Whole-organ volumetry Pre-operative total gastric volume averaged 202.6 ± 68.4 cm³ (empty) and 604.3 ± 141.3 cm³ (full), yielding an expansion capacity (ΔV) of 401.7 cm³ (198.6% increase, n=9). Box plot analysis (Fig3a) showed that patients with larger empty volumes did not systematically exhibit proportionally larger full volumes, indicating that tissue compliance, rather than baseline size alone, governs accommodation. Regional volume distribution All three gastric regions expanded significantly upon water ingestion: fundus from 58.1 ± 42.1 to 209.7 ± 89.6 cm³ (p = 0.008, 261% increase), corpus from 109.0 ± 36.7 to 317.7 ± 93.0 cm³ (p = 0.004, 191% increase), and antrum from 34.4 ± 19.8 to 74.0 ± 37.2 cm³ (p = 0.004, 115% increase) (Fig4 and Table 2). While all regions increased in absolute volume, their relative contributions to total gastric volume shifted. The fundus increased from 27.3% to 34.7% of total volume, while the corpus decreased from 56.0% to 52.7% and the antrum from 16.7% to 12.7%, confirming the fundus as the primary accommodation reservoir (Fig4). Table 2 . Gastric regional volumes in empty and full states before and after sleeve gastrectomy. Mean (± SD) volumes for fundus, corpus, and antrum are presented for both pre-operative and post-operative conditions, measured in empty and full states. ΔV indicates the absolute and relative increases in regional volume from empty to full states. Superscript asterisks denote statistically significant differences between empty and full states for each region (*p<0.05, **p<0.01, Wilcoxon signed-rank test). Region Empty (cm³) Full (cm³) ΔV (cm³) ΔV (%) Pre-Operative Fundus 58.1 ± 42.1 209.7 ± 89.6** +151.6 +261.0% Corpus 109.0 ± 36.7 317.7 ± 93.0** +208.8 +191.6% Antrum 34.4 ± 19.8 74.0 ± 37.2** +39.6 +115.4% Post-Operative Fundus 12.2 ± 11.1 23.7 ± 16.2** +11.5 +94.8% Corpus 38.4 ± 12.0 60.5 ± 21.2** +22.1 +57.5% Antrum 21.9 ± 9.7 34.9 ± 23.8* +12.9 +59.0% 3.2. Postoperative gastric morphology and function Post-operative volumetry (1–2 months, n=8) revealed substantially reduced capacity: empty volume of 73.1 ± 18.3 cm³ and full volume of 120.1 ± 44.3 cm³, with expansion capacity (ΔV) of 47.0 ± 28.7 cm³ (61.1 ± 27.4% increase) (Fig3b). Regional volume distribution Post-operatively, all regions expanded modestly: fundus from 12.2 ± 11.1 to 23.7 ± 16.2 cm³ (p = 0.0078, 94% increase), corpus from 38.4 ± 12.0 to 60.5 ± 21.2 cm³ (p = 0.0078, 58% increase), and antrum from 21.9 ± 9.7 to 34.9 ± 23.8 cm³ (p = 0.021, 59% increase) (Fig4 and Table 2). Regional proportions shifted minimally compared to pre-operative distension, with the fundus contributing ~16–20% and the corpus ~53% in both empty and full states. (Fig4). 3.3. Effect of sleeve gastrectomy on volume Sleeve gastrectomy induced a drastic reduction in total gastric volume. Mean empty gastric volume decreased from 202.6 ± 68.4 cm³ pre-LSG to 73.1 ± 18.3 cm³ post-LSG (p < 0.01), about 36% of baseline. Full gastric volume fell from 604.3 ± 141.3 cm³ to 120.1 ± 44.3 cm³ (p < 0.001), representing roughly 19% of pre-LSG capacity (Fig5). Functional expansion capacity (ΔV) dropped from 401.7 cm³ to 47.0 cm³ (61% relative expansion post-LSG vs 228% pre-LSG). 3D model visualization illustrates marked volumetric restriction (Fig5). Region-specific analysis showed uneven volume reduction: fundus and corpus reduced significantly (p 0.05). 3.4. Mechanical analysis Mechanical tissue properties Biaxial tensile testing of fresh gastric tissue revealed region-specific mechanical behaviour with notable inter-patient variability. The area stretch at damage (λ A ) was 2.67 ± 0.84 (range: 1.88-4.47) for the fundus and 2.23 ± 0.31 (range: 1.65-2.80) for the corpus (n=9). The mean difference did not reach significance (Wilcoxon, p = 0.055) due to high fundus variance, but 8 of 9 patients exhibited higher fundus λ A (Sign test, p = 0.02), indicating a preserved regional mechanical hierarchy despite substantial inter-patient variability, especially in fundus. Correlation with tissue mechanics Fundus tissue extensibility (λ A ) correlated strongly with regional expansion at the patient level (ΔV%) (ρ = 0.77, p = 0.015). The corpus showed a moderate, non-significant correlation (ρ = 0.58, p = 0.10). No significant correlation was detected between tissue extensibility (λ A ) and post-operative expansion (fundus: ρ = −0.10, p = 0.82; corpus: ρ = 0.41, p = 0.32). 4. Discussion 4.1. Summary of major findings & clinical relevance This study is, to our knowledge, the first to link gastric volumetric capacity before and after LSG to tissue mechanical properties through coupled MRI volumetry and biaxial testing on fresh specimens from the same patients. We demonstrate three key findings: (i) LSG reduces functional expansion capacity more than anatomical volume, (ii) regional differences in distension exist between fundus and corpus, with greater fundic expansion and (iii) these differences correlate with tissue extensibility in fundus preoperatively (fundus λ A vs ΔV%, ρ = 0.77). This structure-function relationship was lost postoperatively, consistent with a transition from a compliant reservoir to a geometrically-constrained conduit. 4.2. Contextualization of findings within the literature Before LSG, MRI volumes averaged 203 ± 68 cm³ in the empty state and 604 ± 141 cm³ in the full state after ad libitum water ingestion (up to 500 cm³). These values are in line with functional imaging protocols aimed at physiological fullness rather than maximal distension. [16] reported higher pre-LSG lumen volumes (853 ± 337 cm³) using CT with effervescent powder and ingestion of diluted contrast up to 525 cm³ until patients felt full, whereas [17] reported substantially larger volumes (1310 ± 307 cm³, range 800–1800 cm³) using MDCT with effervescent granules designed to achieve near-maximal distension. [18] measured even larger intraoperative whole-stomach volumes (1553 cm³, range 600-2000 cm³) under controlled methylene blue instillation with pyloric clamping. Taken together, these comparisons mainly illustrate how strongly measured “capacity” depends on the distension method and the physiological versus forced nature of the protocol. Regional analysis of expansion capacity had not previously been performed. After LSG, sleeve volumes were 73 ± 18 cm³ (empty) and 120 ± 44 cm³ (full) at 1-2 months, which agrees well with previous reports despite differences in imaging modality and distension strategy. [17] reported 158 ± 9 cm³ at 6 months and 181 ± 12 cm³ at 12 months with effervescent distension,[19] reported 123 ± 60 cm³ at 1 year using 3D-CT, and [18] reported intraoperative sleeve volumes of 129 cm³ (range 90-220 cm³) under controlled distension. This overall consistency supports the representativeness of our cohort, although the variability in volume measurement highlights the need for optimized imaging protocols [20]. Mechanistically, the strong coupling between fundus extensibility and regional accommodation before LSG is coherent with the anatomical role of the fundus as a passive reservoir with limited contractility during filling [8]. The corpus showed only a moderate, non-significant correlation (ρ = 0.58), which is plausibly explained by a combination of extrinsic constraints from neighbouring organs and the influence of active motility on distension. Because LSG largely removes the fundus (79% volume reduction in empty, 89% in full state), which also appears to be the region with the greatest mechanical variability (in fundus λ A = 2.67 ± 0.84, ranging from 1.88 to 4.47), the remaining stomach is expected to behave more uniformly across patients. In that configuration, early sleeve mechanics are likely dominated by staple line rigidity and the geometric constraints of a tubular organ rather than by intrinsic regional tissue properties, consistent with computational evidence that sleeve behaviour becomes primarily geometry-driven [15]. This provides a straightforward explanation for why the correlation observed before LSG disappears after LSG. Observed mechanical variability suggests that while regional mechanical differences are generally maintained, individual gastric tissue compliance varies substantially, potentially reflecting differences in tissue microstructure, collagen content, or physiological adaptation. 4.3. Limitations This study is limited by the small sample size (n = 9), although the paired longitudinal design strengthens inference for within-patient changes. The ad libitum ingestion protocol introduces variability, but it also intentionally captures a clinically meaningful functional endpoint related to satiety rather than an artificial maximal distension target. Finally, biaxial testing characterised passive mechanics only and cannot capture active neuromuscular responses, which may be more influential outside the fundus. Longer-term follow-up studies (e.g., at one year) may be warranted to assess the durability of these adaptations 4.4. Clinical & research implications Despite these limitations, the observed inter-patient variability in fundic compliance before LSG may contribute to heterogeneous sensations of fullness and variable trajectories after surgery, because “restriction” is not purely a question of volume but also of how easily the reservoir deforms. This is compatible with the broader literature suggesting that residual gastric volume explains only a limited share of the variability in weight loss after LSG [21], implying that geometry alone is not the full story. In practical terms, future work could evaluate whether a non-invasive assessment of gastric compliance before LSG can help stratify patients or tailor surgical strategy, while separating air and water components during MRI filling could further clarify the specific contribution of fundic accommodation. It would also be logical to test whether volumetric outcomes correlate with morphological metrics such as curvature, wall thickness, or local cross-sectional area. Such correlations have been suggested by [22] who found links between suboptimal weight loss and the tube-to-antrum volume ratio or the presence of intrathoracic sleeve migration. Additionally, it would be valuable to use the paired patient-specific geometry and tissue data as inputs for finite element models designed to predict distension patterns and mechanical loads before and after LSG. 4.5. Conclusion Overall, fundic compliance appears to be a primary driver of gastric accommodation before LSG. After LSG, this relationship is lost, consistent with the stomach behaving less like a compliant reservoir and more like a conduit constrained by geometry and the staple line. These results support incorporating patient-specific mechanics, in addition to geometry, to better understand variability in outcomes after bariatric surgery. Conclusion Overall, fundic compliance appears to be a primary driver of gastric accommodation before LSG. After LSG, this relationship is lost, consistent with the stomach behaving less like a compliant reservoir and more like a conduit constrained by geometry and the staple line. These results support incorporating patient-specific mechanics, in addition to geometry, to better understand variability in outcomes after bariatric surgery. Declarations Ethical Approval All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards. Informed Consent Informed consent was obtained from all individual participants included in the study. Conflict of Interest The authors declare that they have no conflict of interest. Funding This research received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors. Author Contribution FF, WW, CM and TB conceived and designed the study. FF developed the overall methodology, performed the investigations, curated the data, conducted the formal analyses, prepared the visualizations, and wrote the original draft of the manuscript. CM contributed to study methodology and investigations and supervised the work. DBBD and LP developed the MRI protocol and performed MRI data acquisition. MG and TT contributed to MRI methodology, provided resources, and supervised MRI-related aspects. TB and PD performed the surgical procedures and led the clinical data collection. AA contributed to data curation and participated in the investigation. AR and AU contributed to methodology, investigation and data curation. FF, WW, CM and TB designed and supervised the ex vivo mechanical testing protocol. All authors critically reviewed and edited the manuscript and approved the final version. Acknowledgement We thank the patients who consented to participate in this study and the clinical teams of the Department of Digestive Surgery (University North Hospital, AP-HM, Marseille, France) for their assistance with specimen procurement. We are grateful the research teams at CEMEF, for their help in biaxial device development, and to the laboratory staff for their assistance during mechanical testing. We also thank the CRMBM team for their contributions to MRI protocol design and acquisition. Data Availability The datasets generated and analysed during the current study are not publicly available due to patient privacy considerations but are available from the corresponding author on reasonable request following appropriate anonymization. References Angrisani L, Santonicola A, Iovino P, Palma R, Kow L, Prager G, et al. IFSO Worldwide Survey 2020–2021: Current Trends for Bariatric and Metabolic Procedures. OBES SURG. 2024;34:1075–85. https://doi.org/10.1007/s11695-024-07118-3 . 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Supplementary Files S1.docx Cite Share Download PDF Status: Published Journal Publication published 01 Apr, 2026 Read the published version in Obesity Surgery → Version 1 posted Editorial decision: Revision requested 21 Jan, 2026 Reviews received at journal 15 Jan, 2026 Reviews received at journal 14 Jan, 2026 Reviews received at journal 14 Jan, 2026 Reviewers agreed at journal 08 Jan, 2026 Reviewers agreed at journal 08 Jan, 2026 Reviewers agreed at journal 08 Jan, 2026 Reviewers agreed at journal 08 Jan, 2026 Reviewers invited by journal 08 Jan, 2026 Editor assigned by journal 07 Jan, 2026 Submission checks completed at journal 07 Jan, 2026 First submitted to journal 19 Dec, 2025 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. 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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-8402831","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":571689845,"identity":"67218c33-9246-4bfe-96f9-d2ee68bbd001","order_by":0,"name":"François 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07:55:44","extension":"html","order_by":14,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":97275,"visible":true,"origin":"","legend":"","description":"","filename":"earlyproof.html","url":"https://assets-eu.researchsquare.com/files/rs-8402831/v1/9c7f0783eb5dc9554b2fdea3.html"},{"id":100366317,"identity":"18c264ed-e351-47e9-a8b0-65b39862d367","added_by":"auto","created_at":"2026-01-16 07:56:13","extension":"jpg","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":147456,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cu\u003eFlow chart of the study protocol. The paired design involved preoperative MRI, followed by sleeve gastrectomy with immediate \u003c/u\u003e\u003cu\u003e\u003cem\u003eex vivo\u003c/em\u003e\u003c/u\u003e\u003cu\u003e biaxial testing of resected tissue, and a final postoperative MRI at 1-2 months. Example of processing and results are provided for each step of the protocol.\u003c/u\u003e\u003c/p\u003e","description":"","filename":"1.jpg","url":"https://assets-eu.researchsquare.com/files/rs-8402831/v1/19632fe26512ce20405c05ef.jpg"},{"id":100124407,"identity":"a464440a-ec33-40f2-85c7-407413c1ef0b","added_by":"auto","created_at":"2026-01-13 09:10:59","extension":"jpg","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":75366,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cu\u003eRegion separation on a full pre-LSG stomach, with anatomical landmarks visible, and cutting plane (a.). Stress and stretch curves from a biaxial tensile test, with bilinear fitting and extracted stretch area(λ\u003c/u\u003e\u003csub\u003e\u003cu\u003eA\u003c/u\u003e\u003c/sub\u003e\u003cu\u003e)before damage (b.)\u003c/u\u003e\u003c/p\u003e","description":"","filename":"2.jpg","url":"https://assets-eu.researchsquare.com/files/rs-8402831/v1/9695cbf171f1b2a1566a555d.jpg"},{"id":100367753,"identity":"cb6db8d7-dc20-4604-9ee2-dcf15af4848c","added_by":"auto","created_at":"2026-01-16 07:57:16","extension":"jpg","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":96525,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cu\u003eGastric volume changes in sleeve gastrectomy patients shown as paired comparisons with boxplots and individual patient trajectories (dashed lines). Empty-to-full stomach distension for pre-operative (a,) and post-operative (b,) conditions. Pre-operative to post-operative volume reduction for empty (c,) and full (d,) stomach states.\u003c/u\u003e\u003c/p\u003e","description":"","filename":"3.jpg","url":"https://assets-eu.researchsquare.com/files/rs-8402831/v1/30809c1279dc7b7d7b37f965.jpg"},{"id":100124413,"identity":"61734569-3404-4ab8-b06d-9d1f34023514","added_by":"auto","created_at":"2026-01-13 09:11:00","extension":"jpg","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":75201,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cu\u003eRegional gastric volumes in empty and full states before and after sleeve gastrectomy. Stacked bar chart showing the absolute volumes (cm³) of the three gastric regions (antrum in red, corpus in green, fundus in blue) in empty and full states, measured pre-operatively and post-operatively. Percentages above the post-operative bars indicate the reduction in total gastric volume compared to the pre-operative state, with statistical significance denoted by asterisks (**p\u0026lt;0.01, Wilcoxon signed-rank test).\u003c/u\u003e\u003c/p\u003e","description":"","filename":"4.jpg","url":"https://assets-eu.researchsquare.com/files/rs-8402831/v1/2d501ee6a05ede74aba0e000.jpg"},{"id":100366121,"identity":"a41b8873-e7d6-48b0-b305-97ef4213cad9","added_by":"auto","created_at":"2026-01-16 07:55:59","extension":"jpg","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":87679,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cu\u003ePaired comparison of total gastric volume before and after LSG with 3D reconstructions for the entire paired cohort (n=8), illustrating the volume reduction and morphological changes in both empty and full states\u003c/u\u003e\u003c/p\u003e","description":"","filename":"5.jpg","url":"https://assets-eu.researchsquare.com/files/rs-8402831/v1/b264e067186d6a42f8f6f11f.jpg"},{"id":106344413,"identity":"bccdb93a-3f7b-4659-9622-2bbe67c790b9","added_by":"auto","created_at":"2026-04-07 16:14:17","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1337464,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-8402831/v1/2558a91b-ac1e-4d4d-876f-809b50b411e7.pdf"},{"id":100124408,"identity":"ebc7c2cb-7bb1-4d23-a2e3-d171d354bd65","added_by":"auto","created_at":"2026-01-13 09:11:00","extension":"docx","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":16767,"visible":true,"origin":"","legend":"","description":"","filename":"S1.docx","url":"https://assets-eu.researchsquare.com/files/rs-8402831/v1/c5cd7df0aebecfad7a06165a.docx"}],"financialInterests":"No competing interests reported.","formattedTitle":"Gastric volumetric filling capacity before and after Sleeve Gastrectomy: An MRI and Biomechanical Study.","fulltext":[{"header":"Key Points","content":"\u003cp\u003e\u0026bull; Fundus shows higher extensibility than corpus with great inter-patient variability\u003c/p\u003e\u003cp\u003e\u0026bull; Empty sleeve volumes dropped to 36% (19% at satiety) of pre-LSG capacity\u003c/p\u003e\u003cp\u003e\u0026bull; Fundus tissue compliance strongly correlates with gastric accommodation pre-LSG\u003c/p\u003e\u003cp\u003e\u0026bull; Mechanics-volume correlation disappears post-LSG, suggesting geometric control\u003c/p\u003e"},{"header":"1. Introduction","content":"\u003cp\u003eLaparoscopic Sleeve Gastrectomy (LSG) is currently the most frequently performed bariatric procedure worldwide, valued for its reproducibility and effectiveness in inducing weight loss and associated medical problems remission [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]. While originally conceptualised as a purely restrictive procedure, its mechanisms are now understood to be multifactorial, involving accelerated gastric emptying, loss of the fundal reservoir, and significant hormonal modulation [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e, \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eAdvances in imaging have enabled detailed characterisation of these morphological and functional changes. Studies using Computed Tomography (CT) or Magnetic Resonance Imaging (MRI) have documented substantial reductions in total gastric capacity, typically reported between 75\u0026ndash;80%, alongside resection of the fundus and corpus, sparing most of the antrum to maintain pyloric function [\u003cspan additionalcitationids=\"CR5\" citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e] Dynamic imaging has further confirmed accelerated early-phase gastric transit kinetics post-LSG [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e, \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e]. However, reported volumetric reductions vary considerably across studies, reflecting a fundamental methodological challenge, with currently no standardised reference method (upper GI contrast series, CT, or MRI) nor consensus imaging protocol for gastric volume assessment. Since the stomach is a highly compliant reservoir, measured volumes are strongly influenced by the degree of luminal distension at the time of imaging, limiting direct comparisons across studies. More critically, gastric accommodation capacity itself, defined as the stomach's ability to expand in response to filling, remains poorly characterised despite being a key determinant of post-operative food restriction, eating comfort, and potentially clinical outcomes. This accommodation capacity depends on two interrelated structural factors: the resting geometry of the gastric pouch (its fasting volume) and the intrinsic mechanical properties of the gastric wall (its extensibility and stiffness).\u003c/p\u003e \u003cp\u003eDespite volumetric and functional insights, a critical gap remains: the relationship between intrinsic gastric wall mechanics and organ-level accommodation has never been directly investigated in humans undergoing LSG. The stomach is a complex, hyperelastic, and anisotropic organ whose accommodation reflex is dictated not only by neural control but fundamentally by the intrinsic passive mechanical properties of its wall, such as stiffness and extensibility [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e, \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e]. Most existing mechanical characterisation on gastric samples relies on porcine models or preserved human tissue (cadaveric or frozen) [\u003cspan additionalcitationids=\"CR11 CR12\" citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e], which fail to represent the \u003cem\u003ein vivo\u003c/em\u003e behaviour of fresh tissue from patients with obesity. Crucially, no study has yet correlated the mechanical properties of the resected tissue with the same patient's functional capacity.\u003c/p\u003e \u003cp\u003eUnderstanding this \"structure-function\" relationship is key to identifying the biomechanical determinants of gastric accommodation and explaining inter-patient variability in post-operative outcomes including weight loss, complications, and quality of life. This study therefore aims to bridge the gap between clinical volumetry and tissue biomechanics through a prospective, longitudinal, and paired design. Specifically, we quantified regional gastric volumes and emptying kinetics using a standardised MRI protocol in patients with severe obesity, both before and after LSG. In parallel, we characterised the passive mechanical properties of the fresh resected tissue (fundus and corpus) from the same patients via biaxial tensile testing immediately following surgery, to investigate the correlation between intrinsic tissue extensibility and macroscopic volumetric expansion.\u003c/p\u003e"},{"header":"2. Materials and Methods","content":"\u003ch2\u003e2.1. Study Design\u003c/h2\u003e\n\u003cp\u003eThis prospective, longitudinal, single-centre study was conducted at [institution blinded for review] following ethics committee approval [ethics approval number blinded for review]. Written informed consent was obtained from all participants. The study followed a paired design in which each patient served as their own control, undergoing MRI volumetry before and 1-2 months after surgery, with \u003cem\u003eex vivo\u003c/em\u003e mechanical testing of their resected gastric tissue performed on the day of surgery (Fig1).\u003c/p\u003e\n\u003ch2\u003e2.2. Participants and surgery\u003c/h2\u003e\n\u003cp\u003eNine patients scheduled for primary LSG were prospectively included (8 women, 1 man, mean age 37 ± 13 years, preoperative BMI 42.2 ± 4.1 kg/m²). Demographics are detailed in Table 1. One patient withdrew from post-operative follow-up but consented to retention of their preoperative data, which were included in baseline analyses (n=9) but excluded from paired comparisons (n=8).\u003c/p\u003e\n\u003cp\u003eAll procedures followed a standardised laparoscopic technique consisting of greater curvature mobilisation from antrum to left diaphragmatic crus, with gastric calibration over a 38-Fr bougie (MID-TUBE MID130, Médical Innovation Développement). Stapling was performed using reinforced (Seamguard, Gore) 60-mm violet cartridges (GIA stapler, Medtronic), starting 4-6 cm proximal to the pylorus and extending to within 1–2 cm of the gastro-oesophageal junction.\u003c/p\u003e\n\u003cp\u003e\u003cu\u003eTable\u0026nbsp;\u003c/u\u003e\u003cu\u003e1\u003c/u\u003e\u003cu\u003e. Included patient demographic data with sex, preoperative BMI (kg/m²), age and associated medical problems (PCOS : Polycystic ovary syndrome, MASH : metabolic-associated steatohepatitis). $ symbol is used to denote which patient was lost in follow-up.\u003c/u\u003e\u003c/p\u003e\n\u003ctable border=\"0\" cellspacing=\"0\" cellpadding=\"0\" width=\"576\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd rowspan=\"3\"\u003e\n \u003cp\u003e\u003cstrong\u003eSex (F/M)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd rowspan=\"3\"\u003e\n \u003cp\u003e\u003cstrong\u003ePreoperative BMI (kg/m²)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd rowspan=\"3\"\u003e\n \u003cp\u003e\u003cstrong\u003eAssociated medical problems\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd rowspan=\"3\"\u003e\n \u003cp\u003e\u003cstrong\u003eAge (years)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd height=\"46\"\u003e\u003cbr\u003e\u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd height=\"30\"\u003e\u003cbr\u003e\u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd height=\"28\"\u003e\u003cbr\u003e\u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd\u003e\n \u003cp\u003eF\u003csup\u003e$\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e39.3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003eSleep apnoea, Type 2 diabetes, MASH, PCOS\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e66\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd height=\"41\"\u003e\u003cbr\u003e\u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd\u003e\n \u003cp\u003eF\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e42\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003eMASH, Sleep apnoea\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e35\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd height=\"14\"\u003e\u003cbr\u003e\u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd\u003e\n \u003cp\u003eF\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e42.1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003eSleep apnoea\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e39\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd height=\"7\"\u003e\u003cbr\u003e\u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd\u003e\n \u003cp\u003eF\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e42.3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003ePCOS, MASH\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e24\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd height=\"7\"\u003e\u003cbr\u003e\u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd\u003e\n \u003cp\u003eF\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e40.5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003ePCOS, Sleep apnoea\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e26\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd height=\"7\"\u003e\u003cbr\u003e\u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd\u003e\n \u003cp\u003eF\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e37.4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003eDyslipidaemia, PCOS\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e30\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd height=\"7\"\u003e\u003cbr\u003e\u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd\u003e\n \u003cp\u003eF\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e37.6\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003eType 2 diabetes, Sleep apnoea\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e48\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd height=\"30\"\u003e\u003cbr\u003e\u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd\u003e\n \u003cp\u003eM\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e49.2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003eSleep apnoea\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e38\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd height=\"7\"\u003e\u003cbr\u003e\u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd\u003e\n \u003cp\u003eF\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e49\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003eMASH\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd\u003e\n \u003cp\u003e27\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd height=\"7\"\u003e\u003cbr\u003e\u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003ch2\u003e2.3. Imaging Protocol and post processing\u003c/h2\u003e\n\u003cp\u003eMRI was performed using a 3T system (MAGNETOM Vida, Siemens Healthineers) at [institution blinded for review] after 6-hour fasting. Patients first underwent baseline scanning in the empty state, then ingested water \u003cem\u003ead libitum\u003c/em\u003e (max 500 cm³) until satiety, followed by a second MRI acquisition at the full state .\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eAnatomical T2-weighted images were acquired using a Half-Fourier Acquisition Single-shot Turbo spin Echo (HASTE) sequence in the axial plane, optimised for rapid abdominal imaging during breath-holds. Typical acquisition parameters were: repetition time (TR) ≈ 700 ms, echo time (TE) = 64 ms, flip angle 106°, and a slice thickness of 4 mm (with 10% gap to minimize signal cross-talk), with an in-plane resolution ranging from 0.5 × 0.5 mm² to 0.8 × 0.8 mm². This high-resolution, motion-free imaging allowed for precise delineation of the gastric wall. Post-operative MRI (1-2 months) replicated the identical protocol.\u003c/p\u003e\n\u003cp\u003eDICOM images were imported into 3D Slicer (v5.8.1). Gastric segmentation combined intensity-based thresholding with manual correction, capturing total gastric volume (wall, luminal fluid, gas) as a functional measure of capacity. Three-dimensional meshes were generated for volume computation.\u003c/p\u003e\n\u003cp\u003eRegional partitioning (fundus, corpus, antrum) was performed using manually positioned anatomical landmarks (gastroesophageal junction, gastroduodenal junction, and angularis incisura) following the methodology detailed in Supplementary Material S1. Two cutting planes separated the three regions, see Fig2a. Regional volumes were computed for empty and full states. The primary functional metric was expansion capacity (ΔV), defined as ΔV = V\u003csub\u003efull\u003c/sub\u003e - V\u003csub\u003eempty\u003c/sub\u003e, representing the stomach's ability to accommodate ingested fluid.\u003c/p\u003e\n\u003ch2\u003e2.4. Mechanical testing protocol\u003c/h2\u003e\n\u003cp\u003eImmediately post-resection, gastric specimens were retrieved. Custom 3D-printed guides and cork plates were used to preserve the \u003cem\u003ein vivo\u003c/em\u003e mechanical state without pre-stretching. Square samples (20 × 20 mm) were excised from fundus and corpus regions (antrum preserved in patients). Samples were kept hydrated in PBS at 4°C and tested within 6 hours. Biaxial tensile tests were performed on a custom-built planar testing machine with 50 N load cells. Equibiaxial extension (1:1 ratio) was applied at 0.1 mm/s until rupture.\u003c/p\u003e\n\u003cp\u003eDamage detection used classical bilinear fitting methods [14,15]. The primary mechanical outcome used in this study was area stretch at damage (\u0026nbsp;\u0026nbsp;, with\u0026nbsp;\u0026nbsp;\u0026nbsp;and\u0026nbsp;\u0026nbsp;\u0026nbsp;the stretches before sample damage in each traction directions), representing tissue's capacity for two-dimensional elongation before irreversible injury. Illustration of a mounted specimen before biaxial tensile test and an example of stress-stretch curve with bilinear fitting are presented\u0026nbsp;Fig2b.\u003c/p\u003e\n\u003ch2\u003e2.5. Statistical Analysis\u003c/h2\u003e\n\u003cp\u003eAnalyses were performed using Python 3.11.5 (SciPy, Pandas, Statsmodels, Matplotlib) with p \u0026lt; 0.05. Statistical assumptions for each test were verified prior to application. Non-parametric methods were used given the small sample size (n=9 baseline, n=8 paired). Paired comparisons used Wilcoxon signed-rank test. Regional mechanical comparisons (fundus vs. corpus) used Wilcoxon signed-rank and Sign tests (the latter to assess within-patient mechanical hierarchy). To investigate the relationship between tissue mechanical properties (area stretch at damage, λ\u003csub\u003eA\u003c/sub\u003e) and volumetric expansion capacity (ΔV), Spearman's rank correlation coefficient (ρ) was computed at the patient level for each region. Data were visualized using box plots with individual patient trajectories (spaghetti plot).\u003c/p\u003e"},{"header":"3. Results","content":"\u003ch2\u003e3.1. Preoperative gastric morphology and function\u003c/h2\u003e\n\u003cp\u003e\u003cstrong\u003e\u003cem\u003eWhole-organ volumetry\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003ePre-operative total gastric volume averaged 202.6 \u0026plusmn; 68.4 cm\u0026sup3; (empty) and 604.3 \u0026plusmn; 141.3 cm\u0026sup3; (full), yielding an expansion capacity (\u0026Delta;V) of 401.7 cm\u0026sup3; (198.6% increase, n=9). Box plot analysis (Fig3a) showed that patients with larger empty volumes did not systematically exhibit proportionally larger full volumes, indicating that tissue compliance, rather than baseline size alone, governs accommodation.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e\u003cem\u003eRegional volume distribution\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAll three gastric regions expanded significantly upon water ingestion: fundus from 58.1 \u0026plusmn; 42.1 to 209.7 \u0026plusmn; 89.6 cm\u0026sup3; (p = 0.008, 261% increase), corpus from 109.0 \u0026plusmn; 36.7 to 317.7 \u0026plusmn; 93.0 cm\u0026sup3; (p = 0.004, 191% increase), and antrum from 34.4 \u0026plusmn; 19.8 to 74.0 \u0026plusmn; 37.2 cm\u0026sup3; (p = 0.004, 115% increase) (Fig4 and Table 2). While all regions increased in absolute volume, their relative contributions to total gastric volume shifted. The fundus increased from 27.3% to 34.7% of total volume, while the corpus decreased from 56.0% to 52.7% and the antrum from 16.7% to 12.7%, confirming the fundus as the primary accommodation reservoir (Fig4).\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cu\u003eTable\u0026nbsp;\u003c/u\u003e\u003cu\u003e2\u003c/u\u003e\u003cu\u003e. Gastric regional volumes in empty and full states before and after sleeve gastrectomy. Mean (\u0026plusmn; SD) volumes for fundus, corpus, and antrum are presented for both pre-operative and post-operative conditions, measured in empty and full states. \u0026Delta;V indicates the absolute and relative increases in regional volume from empty to full states. Superscript asterisks denote statistically significant differences between empty and full states for each region (*p\u0026lt;0.05, **p\u0026lt;0.01, Wilcoxon signed-rank test).\u003c/u\u003e\u003c/p\u003e\n\u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\" width=\"100%\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 16px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 16px;\"\u003e\n \u003cp\u003eRegion\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 16px;\"\u003e\n \u003cp\u003eEmpty (cm\u0026sup3;)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 16px;\"\u003e\n \u003cp\u003eFull (cm\u0026sup3;)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 16px;\"\u003e\n \u003cp\u003e\u0026Delta;V (cm\u0026sup3;)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 16px;\"\u003e\n \u003cp\u003e\u0026Delta;V (%)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd rowspan=\"3\" style=\"width: 16px;\"\u003e\n \u003cp\u003ePre-Operative\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 16px;\"\u003e\n \u003cp\u003eFundus\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 16px;\"\u003e\n \u003cp\u003e58.1 \u0026plusmn; 42.1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 16px;\"\u003e\n \u003cp\u003e209.7 \u0026plusmn; 89.6**\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 16px;\"\u003e\n \u003cp\u003e+151.6\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 16px;\"\u003e\n \u003cp\u003e+261.0%\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 16px;\"\u003e\n \u003cp\u003eCorpus\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 16px;\"\u003e\n \u003cp\u003e109.0 \u0026plusmn; 36.7\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 16px;\"\u003e\n \u003cp\u003e317.7 \u0026plusmn; 93.0**\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 16px;\"\u003e\n \u003cp\u003e+208.8\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 16px;\"\u003e\n \u003cp\u003e+191.6%\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 16px;\"\u003e\n \u003cp\u003eAntrum\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 16px;\"\u003e\n \u003cp\u003e34.4 \u0026plusmn; 19.8\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 16px;\"\u003e\n \u003cp\u003e74.0 \u0026plusmn; 37.2**\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 16px;\"\u003e\n \u003cp\u003e+39.6\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 16px;\"\u003e\n \u003cp\u003e+115.4%\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd rowspan=\"3\" style=\"width: 16px;\"\u003e\n \u003cp\u003ePost-Operative\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 16px;\"\u003e\n \u003cp\u003eFundus\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 16px;\"\u003e\n \u003cp\u003e12.2 \u0026plusmn; 11.1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 16px;\"\u003e\n \u003cp\u003e23.7 \u0026plusmn; 16.2**\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 16px;\"\u003e\n \u003cp\u003e+11.5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 16px;\"\u003e\n \u003cp\u003e+94.8%\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 16px;\"\u003e\n \u003cp\u003eCorpus\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 16px;\"\u003e\n \u003cp\u003e38.4 \u0026plusmn; 12.0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 16px;\"\u003e\n \u003cp\u003e60.5 \u0026plusmn; 21.2**\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 16px;\"\u003e\n \u003cp\u003e+22.1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 16px;\"\u003e\n \u003cp\u003e+57.5%\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 16px;\"\u003e\n \u003cp\u003eAntrum\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 16px;\"\u003e\n \u003cp\u003e21.9 \u0026plusmn; 9.7\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 16px;\"\u003e\n \u003cp\u003e34.9 \u0026plusmn; 23.8*\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 16px;\"\u003e\n \u003cp\u003e+12.9\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 16px;\"\u003e\n \u003cp\u003e+59.0%\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003e3.2. Postoperative gastric morphology and function\u003c/p\u003e\n\u003cp\u003ePost-operative volumetry (1\u0026ndash;2 months, n=8) revealed substantially reduced capacity: empty volume of 73.1 \u0026plusmn; 18.3 cm\u0026sup3; and full volume of 120.1 \u0026plusmn; 44.3 cm\u0026sup3;, with expansion capacity (\u0026Delta;V) of 47.0 \u0026plusmn; 28.7 cm\u0026sup3; (61.1 \u0026plusmn; 27.4% increase) (Fig3b).\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e\u003cem\u003eRegional volume distribution\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003ePost-operatively, all regions expanded modestly: fundus from 12.2 \u0026plusmn; 11.1 to 23.7 \u0026plusmn; 16.2 cm\u0026sup3; (p = 0.0078, 94% increase), corpus from 38.4 \u0026plusmn; 12.0 to 60.5 \u0026plusmn; 21.2 cm\u0026sup3; (p = 0.0078, 58% increase), and antrum from 21.9 \u0026plusmn; 9.7 to 34.9 \u0026plusmn; 23.8 cm\u0026sup3; (p = 0.021, 59% increase) (Fig4 and Table 2). Regional proportions shifted minimally compared to pre-operative distension, with the fundus contributing ~16\u0026ndash;20% and the corpus ~53% in both empty and full states. (Fig4).\u003c/p\u003e\n\u003ch2\u003e3.3. Effect of sleeve gastrectomy on volume\u003c/h2\u003e\n\u003cp\u003eSleeve gastrectomy induced a drastic reduction in total gastric volume. Mean empty gastric volume decreased from 202.6 \u0026plusmn; 68.4 cm\u0026sup3; pre-LSG to 73.1 \u0026plusmn; 18.3 cm\u0026sup3; post-LSG (p \u0026lt; 0.01), about 36% of baseline. Full gastric volume fell from 604.3 \u0026plusmn; 141.3 cm\u0026sup3; to 120.1 \u0026plusmn; 44.3 cm\u0026sup3; (p \u0026lt; 0.001), representing roughly 19% of pre-LSG capacity (Fig5). Functional expansion capacity (\u0026Delta;V) dropped from 401.7 cm\u0026sup3; to 47.0 cm\u0026sup3; (61% relative expansion post-LSG vs 228% pre-LSG). 3D model visualization illustrates marked volumetric restriction (Fig5).\u003c/p\u003e\n\u003cp\u003eRegion-specific analysis showed uneven volume reduction: fundus and corpus reduced significantly (p \u0026lt; 0.01), with fundus losing its role as main reservoir. Antrum volume was conserved (p \u0026gt; 0.05).\u003c/p\u003e\n\u003ch2\u003e3.4. Mechanical analysis\u0026nbsp;\u003c/h2\u003e\n\u003cp\u003e\u003cstrong\u003e\u003cem\u003eMechanical tissue properties\u0026nbsp;\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eBiaxial tensile testing of fresh gastric tissue revealed region-specific mechanical behaviour with notable inter-patient variability. The area stretch at damage (\u0026lambda;\u003csub\u003eA\u003c/sub\u003e) was 2.67 \u0026plusmn; 0.84 (range: 1.88-4.47) for the fundus and 2.23 \u0026plusmn; 0.31 (range: 1.65-2.80) for the corpus (n=9). The mean difference did not reach significance (Wilcoxon, p = 0.055) due to high fundus variance, but 8 of 9 patients exhibited higher fundus \u0026lambda;\u003csub\u003eA\u003c/sub\u003e (Sign test, p = 0.02), indicating a preserved regional mechanical hierarchy despite substantial inter-patient variability, especially in fundus.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e\u003cem\u003eCorrelation with tissue mechanics\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eFundus tissue extensibility (\u0026lambda;\u003csub\u003eA\u003c/sub\u003e) correlated strongly with regional expansion at the patient level (\u0026Delta;V%) (\u0026rho; = 0.77, p = 0.015). The corpus showed a moderate, non-significant correlation (\u0026rho; = 0.58, p = 0.10).\u003c/p\u003e\n\u003cp\u003eNo significant correlation was detected between tissue extensibility (\u0026lambda;\u003csub\u003eA\u003c/sub\u003e) and post-operative expansion (fundus: \u0026rho; = \u0026minus;0.10, p = 0.82; corpus: \u0026rho; = 0.41, p = 0.32).\u003c/p\u003e"},{"header":"4. Discussion","content":"\u003ch2\u003e4.1. Summary of major findings \u0026amp; clinical relevance\u003c/h2\u003e\n\u003cp\u003eThis study is, to our knowledge, the first to link gastric volumetric capacity before and after LSG to tissue mechanical properties through coupled MRI volumetry and biaxial testing on fresh specimens from the same patients. We demonstrate three key findings: (i) LSG reduces functional expansion capacity more than anatomical volume, (ii) regional differences in distension exist between fundus and corpus, with greater fundic expansion and (iii) these differences correlate with tissue extensibility in fundus preoperatively (fundus λ\u003csub\u003eA\u003c/sub\u003e vs ΔV%, ρ = 0.77). This structure-function relationship was lost postoperatively, consistent with a transition from a compliant reservoir to a geometrically-constrained conduit.\u003c/p\u003e\n\u003ch2\u003e4.2. Contextualization of findings within the literature\u003c/h2\u003e\n\u003cp\u003eBefore LSG, MRI volumes averaged 203 ± 68 cm³ in the empty state and 604 ± 141 cm³ in the full state after \u003cem\u003ead libitum\u003c/em\u003e water ingestion (up to 500 cm³). These values are in line with functional imaging protocols aimed at physiological fullness rather than maximal distension. [16] reported higher pre-LSG lumen volumes (853 ± 337 cm³) using CT with effervescent powder and ingestion of diluted contrast up to 525 cm³ until patients felt full, whereas [17] reported substantially larger volumes (1310 ± 307 cm³, range 800–1800 cm³) using MDCT with effervescent granules designed to achieve near-maximal distension. [18] measured even larger intraoperative whole-stomach volumes (1553 cm³, range 600-2000 cm³) under controlled methylene blue instillation with pyloric clamping. Taken together, these comparisons mainly illustrate how strongly measured “capacity” depends on the distension method and the physiological versus forced nature of the protocol. Regional analysis of expansion capacity had not previously been performed.\u003c/p\u003e\n\u003cp\u003eAfter LSG, sleeve volumes were 73 ± 18 cm³ (empty) and 120 ± 44 cm³ (full) at 1-2 months, which agrees well with previous reports despite differences in imaging modality and distension strategy. [17] reported 158 ± 9 cm³ at 6 months and 181 ± 12 cm³ at 12 months with effervescent distension,[19] reported 123 ± 60 cm³ at 1 year using 3D-CT, and [18] reported intraoperative sleeve volumes of 129 cm³ (range 90-220 cm³) under controlled distension. This overall consistency supports the representativeness of our cohort, although the variability in volume measurement highlights the need for optimized imaging protocols [20].\u003c/p\u003e\n\u003cp\u003eMechanistically, the strong coupling between fundus extensibility and regional accommodation before LSG is coherent with the anatomical role of the fundus as a passive reservoir with limited contractility during filling [8]. The corpus showed only a moderate, non-significant correlation (ρ = 0.58), which is plausibly explained by a combination of extrinsic constraints from neighbouring organs and the influence of active motility on distension. Because LSG largely removes the fundus (79% volume reduction in empty, 89% in full state), which also appears to be the region with the greatest mechanical variability (in fundus λ\u003csub\u003eA\u003c/sub\u003e = 2.67 ± 0.84, ranging from 1.88 to 4.47), the remaining stomach is expected to behave more uniformly across patients. In that configuration, early sleeve mechanics are likely dominated by staple line rigidity and the geometric constraints of a tubular organ rather than by intrinsic regional tissue properties, consistent with computational evidence that sleeve behaviour becomes primarily geometry-driven [15]. This provides a straightforward explanation for why the correlation observed before LSG disappears after LSG.\u003c/p\u003e\n\u003cp\u003eObserved mechanical variability suggests that while regional mechanical differences are generally maintained, individual gastric tissue compliance varies substantially, potentially reflecting differences in tissue microstructure, collagen content, or physiological adaptation.\u003c/p\u003e\n\u003ch2\u003e4.3. Limitations\u003c/h2\u003e\n\u003cp\u003eThis study is limited by the small sample size (n = 9), although the paired longitudinal design strengthens inference for within-patient changes. The \u003cem\u003ead libitum\u003c/em\u003e ingestion protocol introduces variability, but it also intentionally captures a clinically meaningful functional endpoint related to satiety rather than an artificial maximal distension target. Finally, biaxial testing characterised passive mechanics only and cannot capture active neuromuscular responses, which may be more influential outside the fundus. Longer-term follow-up studies (e.g., at one year) may be warranted to assess the durability of these adaptations\u003c/p\u003e\n\u003ch2\u003e4.4. Clinical \u0026amp; research implications\u003c/h2\u003e\n\u003cp\u003eDespite these limitations, the observed inter-patient variability in fundic compliance before LSG may contribute to heterogeneous sensations of fullness and variable trajectories after surgery, because “restriction” is not purely a question of volume but also of how easily the reservoir deforms. This is compatible with the broader literature suggesting that residual gastric volume explains only a limited share of the variability in weight loss after LSG [21], implying that geometry alone is not the full story. In practical terms, future work could evaluate whether a non-invasive assessment of gastric compliance before LSG can help stratify patients or tailor surgical strategy, while separating air and water components during MRI filling could further clarify the specific contribution of fundic accommodation. It would also be logical to test whether volumetric outcomes correlate with morphological metrics such as curvature, wall thickness, or local cross-sectional area. Such correlations have been suggested by [22] who found links between suboptimal weight loss and the tube-to-antrum volume ratio or the presence of intrathoracic sleeve migration. Additionally, it would be valuable to use the paired patient-specific geometry and tissue data as inputs for finite element models designed to predict distension patterns and mechanical loads before and after LSG.\u003c/p\u003e\n\u003ch2\u003e4.5. Conclusion\u003c/h2\u003e\n\u003cp\u003eOverall, fundic compliance appears to be a primary driver of gastric accommodation before LSG. After LSG, this relationship is lost, consistent with the stomach behaving less like a compliant reservoir and more like a conduit constrained by geometry and the staple line. These results support incorporating patient-specific mechanics, in addition to geometry, to better understand variability in outcomes after bariatric surgery.\u003c/p\u003e"},{"header":"Conclusion","content":"\u003cp\u003eOverall, fundic compliance appears to be a primary driver of gastric accommodation before LSG. After LSG, this relationship is lost, consistent with the stomach behaving less like a compliant reservoir and more like a conduit constrained by geometry and the staple line. These results support incorporating patient-specific mechanics, in addition to geometry, to better understand variability in outcomes after bariatric surgery.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e \u003ch2\u003eEthical Approval\u003c/h2\u003e \u003cp\u003e All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards.\u003c/p\u003e \u003c/p\u003e \u003cp\u003e \u003cstrong\u003eInformed Consent\u003c/strong\u003e \u003cp\u003e Informed consent was obtained from all individual participants included in the study.\u003c/p\u003e \u003c/p\u003e \u003cp\u003e \u003cstrong\u003eConflict of Interest\u003c/strong\u003e \u003cp\u003eThe authors declare that they have no conflict of interest.\u003c/p\u003e \u003c/p\u003e\u003ch2\u003eFunding\u003c/h2\u003e \u003cp\u003eThis research received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors.\u003c/p\u003e\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eFF, WW, CM and TB conceived and designed the study. FF developed the overall methodology, performed the investigations, curated the data, conducted the formal analyses, prepared the visualizations, and wrote the original draft of the manuscript. CM contributed to study methodology and investigations and supervised the work. DBBD and LP developed the MRI protocol and performed MRI data acquisition. MG and TT contributed to MRI methodology, provided resources, and supervised MRI-related aspects. TB and PD performed the surgical procedures and led the clinical data collection. AA contributed to data curation and participated in the investigation. AR and AU contributed to methodology, investigation and data curation. FF, WW, CM and TB designed and supervised the ex vivo mechanical testing protocol. All authors critically reviewed and edited the manuscript and approved the final version.\u003c/p\u003e\u003ch2\u003eAcknowledgement\u003c/h2\u003e\u003cp\u003eWe thank the patients who consented to participate in this study and the clinical teams of the Department of Digestive Surgery (University North Hospital, AP-HM, Marseille, France) for their assistance with specimen procurement. We are grateful the research teams at CEMEF, for their help in biaxial device development, and to the laboratory staff for their assistance during mechanical testing. We also thank the CRMBM team for their contributions to MRI protocol design and acquisition.\u003c/p\u003e\u003ch2\u003eData Availability\u003c/h2\u003e\u003cp\u003eThe datasets generated and analysed during the current study are not publicly available due to patient privacy considerations but are available from the corresponding author on reasonable request following appropriate anonymization.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eAngrisani L, Santonicola A, Iovino P, Palma R, Kow L, Prager G, et al. IFSO Worldwide Survey 2020\u0026ndash;2021: Current Trends for Bariatric and Metabolic Procedures. 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Geometry of Sleeve Gastrectomy Measured by 3D CT Versus Weight Loss: Preliminary Analysis. World j surg. 2021;45:235\u0026ndash;42. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1007/s00268-020-05807-5\u003c/span\u003e\u003cspan address=\"10.1007/s00268-020-05807-5\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eDeręgowska-Cylke M, Palczewski P, Cylke R, Ziemiański P, Lisik W, Gołębiowski M. Imaging after laparoscopic sleeve gastrectomy \u0026ndash; literature review with practical recommendations. Pol J Radiol. 2021;86:325\u0026ndash;34. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.5114/pjr.2021.106795\u003c/span\u003e\u003cspan address=\"10.5114/pjr.2021.106795\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSingla V, Aggarwal S, Aggarwal S, Gupta M, Singh D. Correlation of weight loss with residual gastric volume on computerized tomography in patients undergoing sleeve gastrectomy: A systematic review. Clin Obes. 2020;10:e12394. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1111/cob.12394\u003c/span\u003e\u003cspan address=\"10.1111/cob.12394\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eNam KH, Choi SJ, Kim SM. Morphologic Study of Gastric Sleeves by CT Volumetry at One Year after Laparoscopic Sleeve Gastrectomy. J Metab Bariatr Surg. 2020;9:42. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.17476/jmbs.2020.9.2.42\u003c/span\u003e\u003cspan address=\"10.17476/jmbs.2020.9.2.42\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"obesity-surgery","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"obsu","sideBox":"Learn more about [Obesity Surgery](https://link.springer.com/journal/11695)","snPcode":"11695","submissionUrl":"https://submission.springernature.com/new-submission/11695/3","title":"Obesity Surgery","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"Sleeve gastrectomy, Gastric biomechanics, Biaxial tensile testing, Magnetic resonance imaging, Gastric accommodation, Tissue mechanics","lastPublishedDoi":"10.21203/rs.3.rs-8402831/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-8402831/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003ch2\u003eIntroduction\u003c/h2\u003e \u003cp\u003eThe stomach exhibits substantial expansion capacity to accommodate food ingestion, yet regional deformation profiles (fundus, corpus, antrum) remain poorly characterised. Laparoscopic sleeve gastrectomy (LSG) drastically reduces anatomical gastric volume, but its impact on accommodation capacity and the underlying mechanical determinants are unknown. This study investigated the correlation between regional gastric tissue mechanics and MRI-measured volumetric changes before and after LSG.\u003c/p\u003e\u003ch2\u003eMethods\u003c/h2\u003e \u003cp\u003eIn a prospective, single-centre study, nine patients with severe obesity (preoperative BMI 42.2\u0026thinsp;\u0026plusmn;\u0026thinsp;4.1 kg/m\u0026sup2;) underwent MRI-based gastric volumetry empty/full (\u003cem\u003ead libidum\u003c/em\u003e, up to 500mL) before and 1\u0026ndash;2 months after LSG. Resected fundus and corpus tissue samples were subjected to biaxial tensile testing to quantify passive mechanical properties. Correlations between regional tissue stretch capacity and volumetric expansion were analysed.\u003c/p\u003e\u003ch2\u003eResults\u003c/h2\u003e \u003cp\u003eAfter water ingestion, preoperative volume increased from 203\u0026thinsp;\u0026plusmn;\u0026thinsp;68 cm\u0026sup3; (empty) to 604\u0026thinsp;\u0026plusmn;\u0026thinsp;141 cm\u0026sup3; (full). Tissue mechanical extensibility was greater (Sign test, p\u0026thinsp;=\u0026thinsp;0.02) in the fundus (2.67\u0026thinsp;\u0026plusmn;\u0026thinsp;0.84) than corpus (2.23\u0026thinsp;\u0026plusmn;\u0026thinsp;0.31). Fundus extensibility strongly correlated with regional volume accommodation (ρ\u0026thinsp;=\u0026thinsp;0.77, p\u0026thinsp;=\u0026thinsp;0.015). Post-LSG, sleeve volumes decreased to 73\u0026thinsp;\u0026plusmn;\u0026thinsp;18 cm\u0026sup3; (empty) and 120\u0026thinsp;\u0026plusmn;\u0026thinsp;44 cm\u0026sup3; (full), representing 62% and 81% reductions respectively. Volume loss predominantly affected the fundus. Postoperatively, no correlation was found between tissue mechanics and gastric expansion.\u003c/p\u003e\u003ch2\u003eConclusion\u003c/h2\u003e \u003cp\u003ePre-LSG, fundic tissue compliance strongly determines gastric accommodation capacity. LSG reduces anatomical volume by two-thirds and functional capacity by three-quarters, with early postoperative expansion independent of intrinsic tissue mechanical properties.\u003c/p\u003e","manuscriptTitle":"Gastric volumetric filling capacity before and after Sleeve Gastrectomy: An MRI and Biomechanical Study.","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2026-01-13 09:10:50","doi":"10.21203/rs.3.rs-8402831/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2026-01-21T23:01:33+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-01-15T17:54:21+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-01-14T20:23:34+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-01-14T10:00:38+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"112639722671976862235047919759284056794","date":"2026-01-08T19:42:56+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"115304153330477381712138637518358121510","date":"2026-01-08T18:25:42+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"78941085720301985833967421794721342694","date":"2026-01-08T07:59:37+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"169310732402629063530513634193981857758","date":"2026-01-08T06:12:48+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2026-01-08T05:54:49+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2026-01-08T00:43:53+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2026-01-07T12:59:19+00:00","index":"","fulltext":""},{"type":"submitted","content":"Obesity Surgery","date":"2025-12-19T08:53:14+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"obesity-surgery","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"obsu","sideBox":"Learn more about [Obesity Surgery](https://link.springer.com/journal/11695)","snPcode":"11695","submissionUrl":"https://submission.springernature.com/new-submission/11695/3","title":"Obesity Surgery","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"769612c6-8687-4f8b-b35b-0de3d86d31db","owner":[],"postedDate":"January 13th, 2026","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[],"tags":[],"updatedAt":"2026-04-07T16:11:19+00:00","versionOfRecord":{"articleIdentity":"rs-8402831","link":"https://doi.org/10.1007/s11695-026-08613-5","journal":{"identity":"obesity-surgery","isVorOnly":false,"title":"Obesity Surgery"},"publishedOn":"2026-04-01 15:58:12","publishedOnDateReadable":"April 1st, 2026"},"versionCreatedAt":"2026-01-13 09:10:50","video":"","vorDoi":"10.1007/s11695-026-08613-5","vorDoiUrl":"https://doi.org/10.1007/s11695-026-08613-5","workflowStages":[]},"version":"v1","identity":"rs-8402831","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-8402831","identity":"rs-8402831","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}