Background and Objectives: Roux-en-Y gastric bypass (RYGB) is one of the most commonly performed metabolic and bariatric surgeries worldwide. Marginal ulcers (MU) are a common complication following RYGB, yet their pathophysiology and the contributing risk factors to their development are not fully understood. Materials and Methods: This retrospective cohort study examined patients who underwent RYGB between January 2008 and December 2023, with 1 to 5 years of follow-up. Data collected included patient- and procedure-related risk factors, as well as postoperative MU events. Statistical analysis methods included the independent samples t-tests, multivariate regression, and Cox regression analyses. Results: Our final cohort included 2106 patients and was predominantly female (80.5%), with a mean age of 47.8 ± 12.1 years and body mass index (BMI) of 45.5 ± 7.5 kg/m². MU occurred in 241 (11.4%) patients, with a mean time to occurrence of 4.5 ± 0.02 years. History of smoking (HR = 1.87, p < 0.001) and gastroesophageal reflux disease (HR = 2.36, p < 0.001) significantly increased hazard for MU, while proton pump inhibitor use (HR = 0.18, p < 0.001) was associated with reduced hazard. Aspirin exposure, regardless of dose and chronicity, did not impact MU. Conclusions: Our findings highlight the importance of preoperative assessment and counseling in patients planning to undergo RYGB. Patient-related factors should guide postoperative monitoring and prophylaxis of MU, as this remains a debated topic amongst experts.

Background: Obesity is associated with increased complications after solid organ transplantation (SOT). While metabolic and bariatric surgery (MBS) improves survival, metabolic, and graft outcomes in transplant patients, we aim to clarify the risk that duodenal bypass MBS (DB-MBS) has on immunosuppression and acute rejection. Methods: A single-center retrospective cohort study was conducted on patients who underwent SOT and DB-MBS between 2003 and 2025. Immunosuppressant regimens and biopsy-confirmed acute rejection details were collected for 3 years after each procedure. Immunosuppressant dosing and trough levels were normalized to individual target levels and evaluated with linear-mixed effects models. Results: The cohort included 19 patients. There were no statistically significant differences in immunosuppression outcomes when DB-MBS is performed before (dosing P =0.821, trough P =0.916) and after (dosing P =0.368, trough P =0.317) SOT. The 3-year acute rejection incidence was 21.1%. Conclusion: The presence and timing of DB-MBS did not significantly alter immunosuppression dosing and trough levels.