This prospective observational cohort study will develop and externally validate a human-supervised, explainable artificial-intelligence decision-support model for analysing factors associated with biliopancreatic limb length selection during one-anastomosis gastric bypass (OAGB). The study will record three prespecified factors: the percentage of the laparoscopic instrument segment J-I covered by visceral or omental fat (P\_JI = 100 × FI/JI), the measured total small-bowel length (TSBL), and the abdominal integral index (AII = (CD/AC) + (CG/EG) + (JI/FI)). The study will evaluate weight-loss effectiveness, nutritional and malabsorptive outcomes, bile/acid reflux, major complications, and technical feasibility. During model development, the AI system will not autonomously assign a BPL length. The operating bariatric surgeon will make the clinical decision, and the model will be evaluated for calibration, external validity, factor contribution, safety constraints, and abstention.
Adults aged 18 years or older at the time of consent.
Patients who meet the institution's independent clinical criteria for primary one-anastomosis gastric bypass.
Planned laparoscopic or robot-assisted OAGB at a participating centre.
Ability to undergo standardized intraoperative measurement of the J-I segment, P_JI components, and total small-bowel length when clinically and ethically appropriate.
Revisional, conversion, or non-primary gastric bypass surgery.
Operative anatomy that prevents reliable identification or measurement of the ligament of Treitz, the J-I segment, or the ileocecal junction.
Unaddressed altered gastrointestinal anatomy that is outside the development protocol.
Severe pre-existing malnutrition or another condition for which experimental variation in BPL length would be considered clinically inappropriate by the treating team.
The proposed registration is based on the current protocol design: a prospective observational cohort for model development and external validation, nested in routine one-anastomosis gastric bypass (OAGB) care. The current protocol does not prospectively assign a biliopancreatic-limb length, does not report patient-level results, and does not claim that any BPL length is optimal. The investigators not intend to assign participants prospectively to 0.5-, 1-, 2-, or 3-m BPL groups
Cohort
Prospective
One-anastomosis gastric bypass with observed biliopancreatic limb length
Procedure/SurgeryParticipants undergo primary laparoscopic or robot-assisted one-anastomosis gastric bypass as part of routine clinical care. The observed biliopancreatic limb length, operative configuration, surgical platform, centre, and surgeon are recorded. During model development, the study does not assign a BPL length and the AI system does not replace the surgeon's clinical judgment. Candidate lengths of 0.5, 1, 2, and 3 m are research-action labels used to evaluate predictions and safety constraints, not automatically assigned treatment arms. Additional exposure variables: * P\_JI (%) = 100 × FI/JI * TSBL in centimetres * AII = (CD/AC) + (CG/EG) + (JI/FI) * Residual absorptive bowel after observed BPL length * Surgical platform: laparoscopic or robot-assisted * Centre and surgeon identifier * Operative configuration and reflux-prevention technique
Percent total weight loss at 12 months after OAGB
Percent total weight loss will be calculated as 100 × (baseline body weight - body weight at 12 months) / baseline body weight. Baseline weight is measured before OAGB using the site-approved calibrated scale. The measure is continuous and will be analysed separately from nutritional harm, reflux, major complications, and technical outcomes.
Incremental out-of-sample predictive contribution of P_JI for 12-month percent total weight loss
The incremental contribution of P\_JI will be evaluated by comparing a prespecified baseline model without the three decision factors with a nested model adding P\_JI. The analysis will report out-of-sample change in Brier score, partial R² or an endpoint-appropriate explained-variation measure, calibration, discrimination, bootstrap confidence intervals, and decision-curve net benefit. P\_JI will be considered the leading factor only if its contribution is reproducibly larger than the incremental contributions of TSBL and AII under the prespecified analysis.
Percent total weight loss at 24 months after OAGB
Percent total weight loss will be calculated using baseline weight and weight at 24 months. The measure will be analysed by observed BPL length and in outcome models containing P\_JI, TSBL, AII, clinical covariates, centre, surgeon, operative configuration, and candidate-length interactions when supported by the design.
Incremental predictive contribution of total small-bowel length
The incremental contribution of measured TSBL will be evaluated by comparing the model containing P\_JI with a nested model adding TSBL. TSBL will be analysed continuously in centimetres or after prespecified standardization. Residual absorptive bowel will be calculated for each observed BPL length. Performance will be reported with out-of-sample Brier score, calibration, discrimination, partial R² or an endpoint-appropriate explained-variation measure, and confidence intervals.
Incremental predictive contribution of the abdominal integral index
The incremental contribution of AII will be evaluated by comparing the model containing P\_JI and TSBL with a nested model adding AII. AII will be calculated as (CD/AC) + (CG/EG) + (JI/FI). Cases in which FI equals zero will be handled as structural missingness for the JI/FI component and analysed using the prespecified missingness and sensitivity-analysis strategy.
Nutritional and malabsorptive safety outcomes
Nutritional and malabsorptive outcomes will be reported separately and will include protein-energy malnutrition, hypoalbuminemia, anaemia, iron or ferritin deficiency, folate deficiency, calcium or vitamin D abnormalities, vitamin B12 deficiency, fat-soluble vitamin deficiency, diarrhoea, steatorrhoea, and need for intensive or parenteral replacement therapy. Definitions, laboratory thresholds, and clinically significant-event criteria will be prespecified in the statistical analysis plan before database lock.
Map coordinates are unavailable for these locations. Locations are shown below instead.
KazakhstanClick on the lead sponsor to view all of their trials.
This trial is not recruiting at the moment. You can still explore other options:
