SADI-S Surgery

Introduction

If you are reading this, you have likely already had detailed conversations about weight loss surgery and are now looking specifically at SADI-S — either as a first operation or as a revision after a previous sleeve gastrectomy. SADI-S is one of the newer bariatric procedures, designed to give strong, durable weight loss and powerful improvement in type 2 diabetes, while being technically simpler than the older duodenal switch operation it evolved from.

This article walks through what SADI-S surgery is, how it works, who it tends to suit, what the operation involves, what recovery looks like, the risks involved, and the lifelong follow-up it requires. The aim is to help you have a more informed conversation with your bariatric team about whether this is the right operation for your situation.

What Is SADI-S Surgery?

SADI-S stands for Single Anastomosis Duodeno-Ileal bypass with Sleeve gastrectomy. It is a bariatric and metabolic surgery that combines two effects in one operation:

• A sleeve gastrectomy, where most of the stomach is removed and what remains is shaped into a narrow tube. This restricts how much you can eat at one time and reduces the hunger hormone ghrelin.
• A single intestinal bypass, where the first part of the small intestine (the duodenum, just past the stomach) is divided and connected directly to a loop of the lower small intestine (the ileum). Food then skips a long section of intestine, which reduces how much fat and how many calories the body absorbs.

SADI-S was developed as a simpler version of the traditional biliopancreatic diversion with duodenal switch (BPD/DS). The classic duodenal switch uses two intestinal joins (anastomoses). SADI-S uses only one. Fewer joins means a shorter operation, fewer places that could leak, and a slightly lower risk of severe long-term malabsorption — while keeping much of the metabolic power of the older procedure.

You may also see SADI-S referred to as:

• SIPS — Stomach Intestinal Pylorus-Sparing surgery
• Loop duodenal switch
• Single anastomosis duodenal switch (SADS)

The two parts of SADI-S work together. Understanding each helps explain why this operation produces both significant weight loss and strong improvement in metabolic disease.

The sleeve gastrectomy component

Surgeons remove roughly 70 to 80 percent of the stomach — mainly the outer, stretchy portion called the fundus. What remains is a slim, banana-shaped tube. The pylorus (the muscular valve at the bottom of the stomach) is preserved. This means food still empties from the stomach into the intestine in a more normal, controlled way, rather than dumping rapidly as can happen after gastric bypass.

Comparison showing: ① normal stomach with fundus and body intact, ② sleeve stomach after removal of the fundus, forming a narrow tube, ③ preserved pylorus in both views.

*AI-generated image - for illustration only. Clinical accuracy is not guaranteed.

The smaller stomach holds far less food, so you feel full quickly. Removing the fundus also removes most of the cells that produce ghrelin, the hormone that drives hunger. Many patients describe feeling much less hungry in the months after surgery.

The intestinal bypass component

Just past the preserved pylorus, the surgeon divides the duodenum. The lower end is then joined to a loop of the ileum, typically about 250 to 300 centimetres from where the small intestine ends. This is the single anastomosis — the one new connection.

Food now travels a much shorter path through the intestine before reaching the colon. Digestive juices from the liver and pancreas still travel down their natural path and mix with food only in the final stretch of small intestine. The result is that fewer calories — especially from fat — are absorbed.

Diagram of the SADI-S anatomy showing: ① sleeved stomach (narrow tube), ② preserved pylorus, ③ duodenum divided just past the pylorus, ④ single anastomosis connecting duodenum to ileum, ⑤ bypassed segment of small intestine, ⑥ ileum loop brought up to form the connection.

*AI-generated image - for illustration only. Clinical accuracy is not guaranteed.

Why SADI-S Is Performed

Bariatric surgeons typically consider SADI-S in two main situations.

As a primary operation

SADI-S may be considered as a first weight loss operation in people with very high BMI or with metabolic disease that needs powerful correction. Surgeons often discuss it when:

• BMI is very high (often 50 or above), where sleeve gastrectomy alone may not produce enough weight loss
• Type 2 diabetes is severe, long-standing, or requires insulin, and stronger metabolic effects are wanted
• Severe metabolic conditions such as very high triglycerides or non-alcoholic fatty liver disease are also present

As a revision after sleeve gastrectomy

One of the most common uses of SADI-S today is as a second-stage operation for people who had a sleeve gastrectomy but did not lose enough weight, regained weight over time, or whose diabetes did not improve enough. Because the sleeve is already in place, adding the single intestinal bypass converts it into a SADI-S without removing or undoing the previous surgery.

The ASMBS and the International Federation for the Surgery of Obesity and Metabolic Disorders (IFSO) describe SADI-S as a reasonable option in both primary and revisional settings, provided the patient is willing to commit to lifelong nutritional follow-up.

Who Is a Candidate?

Eligibility for bariatric surgery has broadened in recent years. The 2022 ASMBS/IFSO indications recommend considering metabolic and bariatric surgery in adults with:

• BMI of 35 or above, regardless of whether obesity-related conditions are present
• BMI of 30 to 34.9 with metabolic disease such as type 2 diabetes, particularly when it is not well controlled with medication and lifestyle

Within those broader bariatric criteria, SADI-S specifically tends to be considered for people who:

• Have a higher BMI (often 45–50 or more) where strong, durable weight loss is the goal
• Have type 2 diabetes that is difficult to control, where the metabolic effect of an intestinal bypass is expected to add meaningful benefit
• Have had a previous sleeve gastrectomy and are seeking further weight loss or better metabolic control
• Are prepared to commit to lifelong vitamin and mineral supplementation and to regular blood-test monitoring

SADI-S may not be suitable when:

• You have significant inflammatory bowel disease, prior major intestinal surgery, or short bowel
• You are unable or unwilling to take supplements and attend follow-up reliably
• Severe gastro-oesophageal reflux is present (in some cases this points the team towards gastric bypass instead)
• There are untreated eating disorders, active substance use, or unstable mental health conditions that should be addressed first

The final decision is made by the bariatric team after assessing your weight history, medical conditions, previous surgeries, mental health, nutritional status, and personal goals.

Alternatives to SADI-S

SADI-S is one of several established bariatric and metabolic operations. Understanding the alternatives helps clarify why a surgeon may suggest SADI-S in particular, or why they may suggest something else.

Sleeve gastrectomy (alone)

The sleeve is the most commonly performed bariatric operation worldwide. It is simpler, has fewer long-term nutritional risks than SADI-S, and produces good weight loss for many people. However, weight regain and inadequate diabetes improvement happen in a meaningful proportion of patients, which is one reason SADI-S exists as a more powerful option or revision.

Roux-en-Y gastric bypass

Often called “gastric bypass,” this operation creates a small stomach pouch and reroutes the small intestine in a Y-shape. It produces strong weight loss and is particularly favoured when severe reflux is present. Compared with SADI-S, it generally has slightly less weight loss on average but a longer track record, with several decades of published outcomes.

Traditional duodenal switch (BPD/DS)

The classic duodenal switch is the operation SADI-S was derived from. It uses two intestinal anastomoses and produces the strongest weight loss and diabetes remission rates of any bariatric procedure. The trade-off is greater technical complexity and a higher rate of long-term nutritional problems. SADI-S aims to capture much of the metabolic benefit with less of that risk.

Adjustable gastric band

Once common, the band is now rarely used in most centres because of high rates of complications and re-operation. It is generally not considered for the patient profile that SADI-S targets.

Non-surgical options

Newer weight-loss medications such as GLP-1 receptor agonists (for example semaglutide and tirzepatide) have changed the conversation around obesity treatment. For some patients, these medications produce meaningful weight loss without surgery. For others — particularly those with very high BMI or severe metabolic disease — surgery still gives more reliable and durable results. Many bariatric teams now discuss medications alongside surgery, both as alternatives and as tools that may be used before or after an operation.

Comparison of intestinal routing: ① SADI-S with one duodeno-ileal anastomosis, ② classic BPD/DS with two intestinal anastomoses, ③ bypassed intestinal segment in each procedure.

*AI-generated image - for illustration only. Clinical accuracy is not guaranteed.

• Intestinal connections: SADI-S has one. Classic BPD/DS has two.
• Operative time: SADI-S is generally shorter.
• Technical complexity: SADI-S is somewhat less complex, though both are advanced operations.
• Weight loss: Both produce very strong weight loss; published series report similar outcomes in the first few years.
• Diabetes remission: Both have among the highest reported diabetes remission rates of any bariatric operation.
• Nutritional risk: Reported rates of severe protein and vitamin deficiencies are generally lower with SADI-S than with classic BPD/DS, but both require lifelong supplementation and monitoring.
• Track record: Classic BPD/DS has decades of long-term data. SADI-S has shorter follow-up, with most published outcomes covering up to about ten years.

Some surgeons still prefer classic BPD/DS for the very highest BMI patients, while many others now offer SADI-S as the default malabsorptive option. Practice varies by centre.

Preparing for SADI-S Surgery

Bariatric surgery is not an isolated event. Preparation usually takes weeks to months and is a structured process led by a multidisciplinary team.

Medical evaluation

You can expect:

• Blood tests, including baseline vitamin and mineral levels
• Assessment of heart and lung function, especially if other medical conditions are present
• Upper endoscopy to check the stomach and oesophagus, identify reflux, and look for conditions such as Helicobacter pylori infection or hiatus hernia
• Sleep study if obstructive sleep apnoea is suspected
• Imaging of the abdomen in some cases, particularly before revisional surgery

Nutritional and psychological assessment

A dietitian will review your eating patterns and help you prepare for the dietary changes ahead. A psychological assessment is standard in most bariatric programmes to screen for eating disorders, depression, and unrealistic expectations, and to confirm that you are well placed to manage the lifelong changes that follow surgery.

Pre-operative diet

Most teams ask you to follow a low-calorie, high-protein diet for about two to four weeks before surgery. This shrinks the liver, which makes the operation safer and technically easier. Stopping smoking well before surgery is strongly advised because smoking increases the risk of complications including poor wound healing and leaks at surgical joins.

Medication review

Your team will review all medications, including diabetes drugs (which often need adjustment around surgery), blood thinners, anti-inflammatory drugs, and supplements. NSAIDs such as ibuprofen are typically avoided after bariatric surgery because they raise the risk of ulcers.

What Happens During SADI-S

SADI-S is almost always performed using minimally invasive techniques — either standard laparoscopy or robotic-assisted laparoscopy. Open surgery is uncommon and usually reserved for unusual situations or when complications during a laparoscopic operation require conversion.

On the day of surgery:

• You receive general anaesthesia and a breathing tube is placed
• Several small incisions (usually four to six) are made in the abdomen
• Carbon dioxide gas is used to create working space inside the abdomen
• The surgeon performs the sleeve gastrectomy, removing the outer portion of the stomach using a stapling device
• The duodenum is divided just past the pylorus
• A loop of ileum is brought up and joined to the duodenum to create the single anastomosis
• Staple lines and the anastomosis are checked for leaks, often by passing dye or air through the new stomach
• The small incisions are closed

Laparoscopic port placement for SADI-S surgery showing typical positions of four to six small abdominal incisions.

*AI-generated image - for illustration only. Clinical accuracy is not guaranteed.

Hospital stay

Most patients stay in hospital for two to three days. You will be encouraged to get up and walk within hours of surgery, which lowers the risk of blood clots and helps the bowel start working again. Pain is usually well controlled with medications that avoid NSAIDs. Many centres use enhanced recovery pathways that include early mobilisation, early sips of water, and rapid removal of drains and catheters.

The first two weeks

Diet progresses in carefully managed stages:

• Clear liquids for the first few days
• Full liquids and protein shakes for the following week or so
• Puréed foods as tolerated

You will be asked to sip fluids slowly throughout the day to avoid dehydration, which is one of the most common reasons for re-admission after bariatric surgery. Light walking is encouraged daily. Heavy lifting, strenuous exercise, and swimming are avoided.

Weeks two to six

Diet advances through soft foods to regular textures, in close coordination with your dietitian. Most people return to desk-based work after about two weeks and to physical work after three to four weeks, though this varies. You should expect to feel tired during this period; your body is healing and you are taking in far fewer calories than before.

Beyond six weeks

By six to eight weeks, most patients are eating small portions of regular food, exercising more, and seeing steady weight loss. Energy generally improves through the first few months. Weight loss continues over 12 to 24 months, after which it tends to plateau.

Vitamin and mineral supplements

• A bariatric multivitamin
• Calcium with vitamin D
• Vitamin A, vitamin E, and vitamin K (the fat-soluble vitamins)
• Vitamin B12
• Iron, especially in menstruating women
• Additional supplements based on blood test results

Post-operative monitoring timeline for SADI-S showing: ① hospital discharge (days 2–3), ② first clinic and blood tests (1 month), ③ blood tests (3 months), ④ blood tests (6 months), ⑤ annual review and bone density (12 months onward).

*AI-generated image - for illustration only. Clinical accuracy is not guaranteed.

Risks and Complications

SADI-S, like all bariatric surgeries, carries real risks. Modern minimally invasive techniques and experienced centres have lowered these substantially, but they are not zero.

Early surgical risks

• Leak at the sleeve staple line or at the intestinal anastomosis — uncommon but serious, and a major reason for prolonged hospital stay or re-operation
• Bleeding, which may need transfusion or, rarely, return to theatre
• Infection of wounds or inside the abdomen
• Blood clots in the legs or lungs — reduced by early walking and short-term blood-thinning injections
• Anaesthetic complications

Later surgical risks

• Internal hernia, where loops of bowel pass through a gap and may twist — less common after SADI-S than after Roux-en-Y bypass, but possible
• Bile reflux, where digestive juices flow back into the stomach — reported in a minority of patients
• Gallstones, which are more common after rapid weight loss
• Stricture or narrowing at the sleeve or anastomosis

Nutritional and metabolic risks

These are the most important long-term risks of any malabsorptive operation:

• Protein malnutrition, particularly in the first year if protein intake is inadequate
• Vitamin and mineral deficiencies — especially of vitamins A, D, E, K, B12, iron, calcium, and zinc
• Anaemia
• Bone loss over time if calcium and vitamin D are not maintained
• Loose, frequent, or foul-smelling stools, which can be socially difficult and is more common when fat intake is high

These risks are managed by lifelong supplementation, regular blood tests (typically at 3, 6, and 12 months in the first year, then yearly), and dietetic support. Compared with classic BPD/DS, published outcomes suggest SADI-S has lower rates of severe protein malnutrition, but the risk is still meaningfully higher than with sleeve or gastric bypass alone.

Mortality

Death from bariatric surgery in experienced centres is rare, generally well under one percent, and SADI-S figures are broadly in line with other complex bariatric operations.

Life After SADI-S

SADI-S is best thought of as a tool, not a cure. The results depend on what you do with it.

Weight loss

Published series report that most patients lose around 70 to 85 percent of their excess body weight over two to three years. Weight loss is typically rapid in the first six months, then gradual, with most patients reaching a stable weight between 18 and 24 months. Some weight regain over the following years is common but usually modest when follow-up and habits are maintained.

Diabetes and metabolic disease

SADI-S has among the highest rates of type 2 diabetes remission of any bariatric procedure. Many patients reduce or stop diabetes medications within weeks of surgery, well before significant weight loss has occurred — reflecting the direct metabolic effects of the intestinal bypass. Improvements in cholesterol, triglycerides, blood pressure, sleep apnoea, and fatty liver disease are commonly reported. Whether diabetes stays in remission long term depends on how long you had diabetes before surgery, how severe it was, and how well habits are maintained afterwards.

Eating after SADI-S

You will eat much smaller portions, focus on protein first at every meal, and learn to chew thoroughly and eat slowly. Some foods may not be well tolerated, and this varies by person. Drinking calories — sugary drinks, juices, alcohol — tends to undermine weight loss and is generally discouraged.

Pregnancy

If you may become pregnant, most bariatric teams advise waiting 12 to 18 months after surgery, when weight is stable and nutritional status is well established. Pregnancy after any malabsorptive operation should be managed by an obstetric team familiar with bariatric patients, with close monitoring of vitamin levels.

Skin and body changes

Significant weight loss often leaves loose skin, and some patients consider body-contouring surgery after weight has been stable for a year or more. This is a separate set of operations and a separate decision.

Mental health

Big changes in body, eating, and identity can affect mood and relationships. Many bariatric programmes include ongoing psychological support, which is helpful during the transition. New eating problems, including grazing or, less commonly, increased alcohol use, are recognised after bariatric surgery and respond best when addressed early.

Reversibility

SADI-S is generally regarded as permanent. The sleeve gastrectomy part cannot be undone because stomach tissue has been removed. The intestinal bypass can technically be reversed in rare circumstances, such as severe malnutrition, but this is uncommon and complex. The decision to have SADI-S should be made on the assumption that it is for life.

Long-term Follow-up

Lifelong follow-up is part of the operation, not an optional extra. Typical follow-up includes:

• Clinic visits at 1, 3, 6, and 12 months in the first year, then annually
• Blood tests at each visit, checking protein levels, full vitamin and mineral panels, liver and kidney function, blood counts, and glycaemic control
• Bone density scans at intervals advised by your team
• Ongoing dietetic input
• Mental health support when needed

People who attend follow-up consistently and take their supplements reliably have markedly better long-term outcomes than those who drift away from the programme. If you are travelling for surgery, arranging a clear follow-up plan with a local team at home is essential before you go.

Frequently Asked Questions

How is SADI-S different from a gastric sleeve?

A gastric sleeve alone is purely restrictive — it makes the stomach smaller. SADI-S includes the sleeve plus an intestinal bypass that reduces absorption. The result is stronger weight loss and a stronger effect on type 2 diabetes, but with greater nutritional demands afterwards.

Can SADI-S be done if I already had a sleeve?

Yes. One of the most common uses of SADI-S today is as a second-stage operation after a sleeve gastrectomy that did not produce enough weight loss or enough diabetes improvement. Because the sleeve is already in place, the surgeon only needs to add the intestinal bypass.

Will my diabetes go away after SADI-S?

SADI-S has among the highest reported rates of diabetes improvement and remission of any bariatric operation. Many people are able to reduce or stop their diabetes medications. Whether full remission is reached and held depends on how long you have had diabetes, how severe it is, and your habits after surgery. Your endocrinologist and surgeon can give you a personalised view.

Will I have to take vitamins for life?

Yes. Lifelong vitamin and mineral supplementation is not optional after SADI-S. Stopping supplements puts you at risk of serious deficiencies, some of which can cause permanent damage. Regular blood tests check that your levels are adequate and allow your team to adjust doses.

Is SADI-S reversible?

In practical terms, no. The sleeve part removes stomach tissue permanently. The bypass can be technically undone in rare medical emergencies, but SADI-S should be considered a permanent change.

How long does the operation take?

Typically two to three hours, though longer in revisional or complex cases.

How soon can I exercise after SADI-S?

Walking begins the day of surgery. Light activity builds gradually over the first two weeks. Moderate exercise such as cycling or swimming usually resumes around four to six weeks, and heavier resistance work later, guided by your surgical team.

Will I have loose skin after weight loss?

Many people do, particularly after large amounts of weight loss. Skin changes vary by age, genetics, and how much weight is lost. Body-contouring surgery is an option that some patients consider once weight has been stable for at least a year.

Can I drink alcohol after SADI-S?

Alcohol is absorbed differently after any bariatric surgery and its effects can be felt much more strongly. There is also evidence of higher rates of alcohol-related problems after bariatric surgery. Most teams advise avoiding alcohol entirely for at least six to twelve months and being cautious with it long term.

What if I become pregnant after SADI-S?

Most teams advise waiting 12 to 18 months after surgery before pregnancy, so that weight is stable and nutrition is well established. Pregnancy after SADI-S needs careful nutritional and obstetric monitoring because of the increased risk of vitamin deficiencies affecting the baby.

Conclusion

SADI-S surgery is a powerful bariatric and metabolic operation that combines a sleeve gastrectomy with a single intestinal bypass. For people with very high BMI, difficult-to-control type 2 diabetes, or inadequate results from a previous sleeve, it offers strong, durable weight loss and significant improvement in metabolic health, while being technically simpler than the older duodenal switch.

It is also a major commitment. Lifelong vitamin and mineral supplementation, regular blood tests, ongoing dietetic input, and consistent follow-up are part of the operation, not optional extras. The patients who do best are those who go in well informed, have realistic expectations, and stay engaged with their bariatric team for years afterwards. Whether SADI-S is the right choice in your situation is a decision to make together with a bariatric surgeon, dietitian, and the wider team after a full assessment of your health and your goals.