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

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.