TSBL-Based Versus BMI-Based Biliopancreatic Limb Length in One-Anastomosis Gastric Bypass

This is a single-center, prospective, randomized controlled trial comparing two methods for determining biliopancreatic limb length (BPLL) during laparoscopic one-anastomosis gastric bypass (OAGB) in patients with morbid obesity. Eligible patients aged 18-65 years with BMI ≥35 kg/m² (non-Asian) or ≥32.5 kg/m² (Asian populations) who were candidates for primary OAGB were randomized 1:1 using a computer-generated randomization sequence with sequentially numbered, opaque sealed envelopes.

In the intervention (TSBL-based) group, total small bowel length (TSBL) was measured intraoperatively from the ligament of Treitz to the ileocecal valve, and BPLL was calculated as 0.35 × TSBL. In the control (BMI-based) group, BPLL was determined using standard fixed lengths based on BMI category (150 cm, 180 cm, or 200 cm). All other surgical steps were identical between groups.

The primary outcome is percentage excess weight loss (%EWL) assessed longitudinally at baseline, 3, 6, and 12 months. Secondary outcomes include percentage total weight loss (%TWL), BMI, BMI loss, improvement of obesity-related comorbidities, and postoperative complications graded using the Clavien-Dindo classification. Statistical analysis uses linear mixed models to evaluate effects of group, time, and group-by-time interaction.

Because blinding of patients and surgeons was not feasible given the nature of the surgical intervention, outcome assessment relied on objective anthropometric and clinical measures. This record reflects a planned interim analysis conducted on the first 75 of a planned total of 100 enrolled patients, with 51 patients having completed 12-month follow-up at the time of this analysis.

Inclusion criteria

• Age between 18 and 65 years
• BMI ≥35 kg/m² in non-Asian populations or ≥32.5 kg/m² in Asian populations
• Presence or absence of metabolic comorbidities (including type 2 diabetes, hypertension, and dyslipidaemia)
• Eligibility for primary one-anastomosis gastric bypass (OAGB)
• Provision of written informed consent

Exclusion criteria

• BMI below the defined thresholds
• Severe decompensated cardiac, pulmonary, hepatic, or renal disease
• Acute inflammatory conditions
• Active gastric or duodenal ulcer
• Psychiatric disorders or substance abuse
• Pregnancy or breastfeeding
• Active malignancy
• Severe intra-abdominal adhesions due to prior surgery
• Secondary obesity related to hypothalamic-pituitary-adrenal axis disorders