SADI-S and Duodenal Switch Surgery: What to Know

Oct 12, 2026

The duodenal switch and a newer, simpler version called SADI-S are weight-loss operations that shrink the stomach and reroute the small intestine. They tend to bring more weight loss than other operations but require vitamins and checkups for life.

Know the warning signs after weight-loss surgery. Baylor College of Medicine tells bariatric patients to call 911 for trouble breathing, coughing up blood or severe chest pain. Cleveland Clinic, MedlinePlus and Baylor say to call your surgeon right away for belly pain, fever, vomiting that won’t stop, severe diarrhea, signs of dehydration, a racing heart, leg swelling, black or bloody stools, yellow skin or eyes, being unable to eat or drink, or a red, swollen or draining incision.

In the video above, LoneStar Bariatrics, the North Texas practice of bariatric surgeon Dr. Chad Carlton, shows how SADI surgery is performed. The information below comes from the medical sources listed at the end of this article.

What these operations do

Both start with a sleeve gastrectomy: the surgeon removes most of the stomach, leaving a narrow tube but keeping the valve at its outlet. The first part of the small intestine (the duodenum) is then cut just past that valve and connected to a section much farther down. Food skips a long stretch of intestine, so fewer calories are absorbed. The American Society for Metabolic and Bariatric Surgery (ASMBS) says gut hormone changes also curb hunger and improve blood sugar.

Duodenal switch (BPD/DS). Short for biliopancreatic diversion with duodenal switch, it uses two connections. Food and digestive juices travel separately and meet only near the end of the small intestine. ASMBS says food bypasses about 75% of the small intestine. Our library also has a duodenal switch animation.

SADI-S. Single anastomosis duodeno-ileal bypass with sleeve gastrectomy, first described in 2007, simplifies the duodenal switch to one connection: a loop of intestine several feet from its end is joined to the duodenum. Cleveland Clinic says it bypasses about half of the small intestine, so more nutrients are absorbed, and it is quicker to perform. ASMBS endorsed SADI-S in 2020, judging its results so far similar to the classic operation’s.

How they compare with the sleeve and bypass

A sleeve gastrectomy only shrinks the stomach. A gastric bypass routes food past most of the stomach and the upper small intestine. The duodenal switch and SADI-S bypass more intestine, which Cleveland Clinic and ASMBS say raises the risk of vitamin and mineral shortages. The National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) says the duodenal switch brings the most weight loss but the highest risk of complications. It is rare: under 1% of U.S. weight-loss operations in 2018, ASMBS reported.

Who may be considered

For weight-loss surgery in general, ASMBS guidelines updated in 2022 recommend surgery for adults with a body mass index (BMI) of 35 or more, or 30 or more with type 2 diabetes. The duodenal switch in particular is generally considered for people with a BMI over 50, according to Loyola Medicine and M Health Fairview. Professional sources also mention:

  • Type 2 diabetes. ASMBS calls the duodenal switch the most effective approved operation for it.
  • A past sleeve. ASMBS says SADI-S can be a good option for people who had a sleeve gastrectomy and regained weight or didn’t lose enough.

Benefits

  • Weight loss. In a Norwegian and Swedish trial of 60 people with a BMI of 50 to 60, those randomly assigned to a duodenal switch had lost about a third of their starting weight 10 or more years later, versus about a fifth after gastric bypass. The Spanish surgeons who first described SADI-S reported a similar 10-year average, though not all patients were followed that long.
  • Diabetes. ASMBS calls both operations highly effective for type 2 diabetes.

Risks and downsides

  • Surgery risks include bleeding, infection, blood clots, leaks, hernias and bowel blockage. ASMBS says the duodenal switch is a longer, more complex operation with slightly more complications than other procedures.
  • Nutrition problems are the main long-term concern: low protein; low vitamins A, D, E and K; and low iron, zinc or copper. ASMBS nutrition guidelines cite studies in which more than half of duodenal switch patients ran low on zinc or copper. Shortages can occur even with supplements and can lead to anemia and weak bones. In the 10-year trial, about 1 in 7 duodenal switch patients developed protein malnutrition, and most needed another operation.
  • Bowel changes. Stools often become looser and more frequent, with more gas, and M Health Fairview mentions foul-smelling gas. Cleveland Clinic says following the eating plan prevents diarrhea in most cases, but ASMBS notes a few SADI-S patients needed surgery for lasting diarrhea.
  • Reflux and heartburn can start or worsen, ASMBS says.
  • Gallstones are more likely during rapid weight loss.

What’s still uncertain

SADI-S is still fairly new. In its 2020 statement, ASMBS asked for more long-term research and urged caution, citing open questions about nutrition, the best length for the shared channel and long-term weight regain. It is also unknown whether SADI-S’s single-loop design changes the risk of bile reflux.

For the classic duodenal switch, the 10-year trial found more weight loss than gastric bypass, but also more vitamin shortages, bone thinning and loose stools. Its authors concluded it may not be better than bypass for people with a BMI of 50 to 60.

Life after surgery

  • Recovery. Cleveland Clinic says most people stay in the hospital one to two days and resume normal activities within about a month.
  • Eating. Meals move from liquids to pureed and soft foods, then to small portions of regular food, with help from a dietitian.
  • Supplements for life. Your care team chooses them and adjusts them based on blood tests.
  • Lifelong checkups. Cleveland Clinic describes frequent visits for two years, then regular visits for life. ASMBS guidelines advise checking zinc and copper at least yearly after a duodenal switch.

Questions to ask your surgeon

  • Which operation best fits my health and goals, and why?
  • How much of my small intestine would be bypassed?
  • Which vitamins and minerals will I need, and how often will my blood be tested?
  • What bowel changes should I expect, and how are they managed?
  • If I’ve had a sleeve, how does SADI-S compare with other revision options?
  • Who will check my nutrition and bone health over the long term?

Dr. Carlton is a bariatric surgeon in the Dallas–Fort Worth area. See Dr. Carlton’s Best Docs Network profile for more about the practice.

Sources

This article is for general information only and is not medical advice. Talk with a qualified health professional about your own situation. If you think you may have a medical emergency, call 911.

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