What Is SASI Bypass?

SASI stands for single-anastomosis sleeve ileal bypass and is also described as sleeve ileal bipartition or loop bipartition. The surgeon first creates a sleeve-shaped stomach. A second route is then made by joining part of the lower stomach to the ileum. Food can continue through the duodenum and normal small-bowel pathway, while some passes through the new connection.

The exact limb length, sleeve construction and anastomosis position matter. They affect absorption, bile exposure, weight response and nutritional risk. Patients should receive a diagram and operation note rather than relying on the name “SASI”, because terminology and technique can vary between centres.

SASI Is Not the Same as SADI-S

SASI and single-anastomosis duodeno-ileal bypass with sleeve gastrectomy (SADI-S) are different operations. SASI creates a stomach-to-ileum connection while retaining the natural route; SADI-S divides the duodenum and connects it to ileum. Evidence or guideline statements for one procedure should not be presented as proof for the other.

What Does the Evidence Show?

Published studies suggest SASI may support weight loss and improvement in some obesity-related conditions, but much of the evidence is observational, follow-up length varies and techniques are not fully standardised. Some comparative studies and recent evidence syntheses are encouraging, yet they do not establish that SASI is superior for every patient or that long-term nutritional risks are lower than classic bypass.

Claims of “powerful metabolic control”, permanent appetite reduction, guaranteed diabetes remission or prevention of reflux are therefore inappropriate. A surgeon should explain the quality and limits of the evidence, centre-specific outcomes and why a more established operation is or is not preferred.

Who May Be Considered?

Suitability cannot be decided from a BMI list on a webpage. NICE recommends multidisciplinary bariatric assessment that considers obesity-related conditions, previous treatment, anaesthetic and surgical risk, eating behaviour, mental health, medicines, reflux, gastrointestinal disease, nutritional status and the person’s ability to take supplements and attend long-term follow-up.

SASI may be discussed in selected people when an experienced specialist team believes its risk-benefit profile is appropriate. The assessment should compare sleeve, Roux-en-Y gastric bypass, one-anastomosis gastric bypass and non-surgical options. Diabetes, carbohydrate cravings or a wish to avoid a different operation do not automatically make someone suitable.

How Is the Operation Performed?

SASI is usually performed laparoscopically under general anaesthesia. A sleeve gastrectomy removes part of the stomach, then a single anastomosis joins the lower stomach to a measured point of ileum. Leak testing, port placement, bowel measurement and other technical decisions vary by surgeon and clinical need.

“Single anastomosis” does not mean minor surgery. The patient has both a stomach resection and an intestinal bypass/bipartition. Operation time, hospital stay and return to activity depend on health, procedure details and recovery; fixed promises such as discharge in 24–48 hours or normal activity in 5–7 days should not replace a personal plan.

Possible Benefits and Their Limits

• Weight loss may be greater than after sleeve alone in some study populations, but individual response varies.
• Blood glucose and other obesity-related conditions may improve, but remission is not guaranteed and diabetes medicines need supervised adjustment.
• Two food routes may preserve some normal passage, but this does not eliminate malabsorption or nutritional deficiency.
• Some patients may experience reflux improvement while others can develop or continue reflux, bile exposure or upper gastrointestinal symptoms.

Risks and Complications

Risks include those of sleeve gastrectomy and intestinal anastomosis. They can occur early or years later and may require endoscopy, radiology, medicines, hospital admission or revision surgery.

• Bleeding, leak, infection, blood clots, breathing or anaesthetic complications
• Narrowing, ulcer, obstruction, internal hernia or anastomotic problems
• Reflux, bile reflux, nausea, vomiting, dumping symptoms or post-meal hypoglycaemia
• Diarrhoea, troublesome bowel changes, dehydration or excess malabsorption
• Protein-calorie malnutrition and iron, B12, folate, calcium, vitamin D or other micronutrient deficiencies
• Insufficient weight response, weight regain or need for further surgery

Ask the clinic for its own audited outcomes, definitions of complications, readmission and revision rates, and what happens financially if additional treatment is required.

Nutrition and Lifelong Monitoring

Diet progression is individual. Do not move from fluids to purées, soft foods or solids only because a fixed week has arrived. The surgical and dietetic teams should provide a written hydration, protein, texture and supplement plan with warning signs.

Long-term monitoring should include weight and symptoms, dietary review, prescribed supplements and blood tests. NICE recommends at least two years of specialist bariatric follow-up after surgery and lifelong annual monitoring under shared care. UK patients should confirm before travel whether their GP or local bariatric service can support the proposed SASI monitoring plan.

UK Return and Urgent Help

Carry the operation note, bowel measurements, implant or medicine information, discharge summary, blood results, supplement plan and direct clinical contact details. Agree when it is safe to fly and how suspected complications will be assessed in Turkey and the UK.

Call 999 or attend A&E for severe or rapidly worsening abdominal or chest pain, breathing difficulty, collapse, vomiting blood or another emergency. Use NHS 111 or urgent GP care for persistent vomiting, inability to keep fluids down, fever, increasing wound problems, very little urine or other prompt concerns. Remote clinic messaging is not an emergency service.

Can SASI Anatomy Be Revised?

Revision does not restore the original anatomy. The sleeve component removes stomach tissue and is not reversed. The intestinal connection may sometimes be revised or taken down, but that is another operation with adhesions, anaesthetic and surgical risks. Anatomy and symptoms must be assessed before any revision plan.

Frequently Asked Questions

Does SASI cure type 2 diabetes?

No cure or remission can be guaranteed. Glucose may improve quickly after bariatric surgery, so diabetes medicines must be reviewed to reduce the risk of hypoglycaemia. Ongoing monitoring remains necessary.

Does preserving the natural route prevent deficiencies?

No. It may change the pattern of absorption compared with other bypass operations, but protein and micronutrient deficiencies can still occur and require lifelong prevention and monitoring.

How much weight will I lose?

Results vary with anatomy, health, follow-up and many other factors. Study averages are not a personal prediction, and before-and-after photos cannot show complication or nutritional outcomes.

UK and Research Sources

• NICE: bariatric surgery assessment and follow-up
• NICE: lifelong annual monitoring after bariatric discharge
• Case-matched multicentre SASI versus sleeve study
• Comparative one-year SASI plus sleeve versus sleeve study
• 2026 SASI outcomes and complications evidence synthesis

Last clinically reviewed for UK source alignment: 10 August 2026. This page provides general information and cannot confirm treatment suitability.