Tailored One Anastomosis Gastric Bypass

Scientific Background and Rationale One-Anastomosis Gastric Bypass (OAGB) is the most common bariatric surgery in Israel, demonstrating effective and sustained weight loss, improvement in obesity-related comorbidities, and a relatively low failure rate. The procedure involves creating a long gastric pouch and an anastomosis with a segment of the small intestine, bypassing a portion of the digestive tract. The length of the biliopancreatic limb (BPL) significantly influences metabolic outcomes, with a longer BPL associated with greater weight loss and metabolic improvements. However, the optimal BPL length remains debated, as excessive length can lead to malabsorption, while insufficient length may result in weight regain.

Current standard practice uses a fixed BPL length of 150-200 cm to minimize nutritional complications, but tailoring the BPL length to the total small bowel length (TSBL) may improve individual outcomes. This study evaluates whether personalized BPL length leads to more effective weight loss compared to a standard 180 cm BPL.

Study Objectives To assess whether adjusting BPL length to 40% of the TSBL results in more effective weight loss compared to a fixed 180 cm BPL.

Endpoints BPL and TSBL lengths Weight loss over follow-up Postoperative nutritional complications Improvement in obesity-related diseases Study Design

Participants:

200 patients at a single center; 500 in a multi-center study

Centers:

Ichilov (Tel Aviv Sourasky Medical Center), Assuta Tel Aviv, Herzliya Medical Center

Inclusion Criteria:

Adults (≥18 years) undergoing OAGB

Exclusion Criteria:

Patients \<18 years, pregnant women, or those lacking decision-making capacity Prior bariatric surgery Short bowel (\<350 cm) Randomization and Surgical Intervention

Participants will be randomly assigned to one of two groups:

Study Group: BPL length is set at 40% of TSBL, ensuring at least 250-300 cm of common channel (CC).

Control Group: Standard BPL length of 180 cm. Follow-up and Data Collection

Routine post-surgical follow-ups at 2 weeks, 1, 3, 6, and 12 months, then annually. Assessments include:

Weight loss Medication adherence Symptoms of malabsorption Biochemical markers (e.g., albumin, vitamins, iron) Quality of life (BAROS questionnaire) completed at 6 and 12 months Data collected from hospital records, without external confidential sources Privacy and Data Security Data is anonymized and stored securely within hospital systems. Multi-center data is coded and transferred securely for statistical analysis. Statistical Analysis Patient characteristics analyzed using t-tests and chi-square tests. Results presented with standard deviation and p-values. Study Duration 8 years from approval. Each patient's participation extends through a standard follow-up period. This study aims to optimize BPL length in OAGB to enhance weight loss while minimizing complications.

Scientific Background and Rationale for the Study One-Anastomosis Gastric Bypass (OAGB) is the most common bariatric procedure in Israel \[1\]. Over the years, OAGB has been proven to be an effective surgery, yielding significant and sustained weight loss, improvement in obesity-related comorbidities, and a relatively low failure rate \[2\].

The procedure involves separating a long gastric pouch from the remaining stomach and creating an anastomosis between the pouch and a distant loop of the small intestine \[3\]. Since this procedure bypasses a relatively long intestinal segment (typically 150-200 cm), it results in malabsorption of carbohydrates, fats, proteins, and other nutrients. This malabsorption-related mechanism leads to greater weight loss compared to purely restrictive surgeries like sleeve gastrectomy \[4\].

The length of the bypassed segment, specifically the biliopancreatic limb (BPL), plays a critical role in determining the metabolic outcomes of OAGB. A longer BPL is associated with more significant weight loss and greater improvement in obesity-related diseases \[5\]. However, the ideal BPL length remains a topic of global debate. Some experts recommend measuring the total small bowel length (TSBL) or ensuring at least 250-300 cm of common channel (CC) to prevent pathological malabsorption in patients with a shorter bowel and to reduce the risk of weight regain in those with a longer bowel \[3,6\].

Currently, the most widely accepted approach is to standardize the BPL length at 150-200 cm, as studies have shown that this range minimizes the risk of nutritional deficiencies \[7\]. However, tailoring the BPL length to the patient's TSBL is an increasingly recognized strategy that may optimize outcomes by ensuring a more precise CC length, thereby reducing complications and improving long-term weight loss.

Study Objective To evaluate whether tailoring the BPL length to the TSBL results in more effective weight loss compared to a standard bypass length of 180 cm.

Study Endpoints BPL and TSBL lengths Weight progression during follow-up Postoperative nutritional complications Improvement in obesity-related comorbidities Study Participants Single-center cohort: 200 patients Multi-center cohort: 500 patients Participating centers: Ichilov Medical Center, Assuta Tel Aviv, Herzliya Medical Center Participant Recruitment and Informed Consent Process

Eligible participants (competent adults) will be invited to sign a digital informed consent form via the PM7 system. The process includes:

A face-to-face explanation Time for consideration An opportunity to ask questions The signed consent form will be stored digitally in PM7 and printed as needed. If digital signing is not possible, a paper form will be used. The process adheres to Regulation 169 and follows an updated consent protocol. Enrollment and consent will take place during the preoperative consultation at the bariatric clinic.

Inclusion Criteria Patients aged 18 and older scheduled for OAGB at Tel Aviv Sourasky Medical Center Exclusion Criteria Special populations - Patients under 18, pregnant women, individuals lacking decision-making capacity, etc.

Previous bariatric surgery Withdrawal Criteria TSBL \< 350 cm, as this would prevent achieving a common channel length of at least 250-300 cm, increasing the risk of severe malabsorption and nutritional deficiencies (protein, vitamins, iron).

Study Methods and Design Randomization Process After enrollment and consent, participants will be randomly assigned to either the intervention or control group.

Surgical Interventions Intervention Group: The surgeon will manually measure TSBL intraoperatively and create a BPL equal to 40% of the TSBL. This ensures a minimum CC length of 250-300 cm, in line with standard OAGB recommendations.

Control Group: The surgeon will measure the TSBL but will create a fixed BPL of 180 cm, as per the current standard.

Postoperative Follow-Up Patients will undergo routine follow-up at 2 weeks, 1, 3, 6, and 12 months, and annually thereafter.

Data Collection and Privacy Identifiable patient information will be separated from the dataset by an authorized investigator.

The principal investigator will maintain the coding key in a password-protected file within the hospital network.

Data will remain within the hospital and not be shared externally. Statistical Analysis T-tests and chi-square tests will be used to compare baseline characteristics. Results will be reported in tables with standard deviation and p-values. Study Timeline and Duration Total study duration: 8 years from approval.

Eligibility Criteria:
Inclusion Criteria:

* Adults (≥18 years) undergoing OAGB

Exclusion Criteria:

* Patients \<18 years, pregnant women, or those lacking decision-making capacity Prior bariatric surgery Short bowel (\<350 cm)