MagDI to SADI-S Conversion

MagDI with sleeve gastrectomy redirects only part of each meal through a magnet-formed side connection. When that partial diversion produces too little weight loss or diabetes control, it can be strengthened by converting MagDI to SADI-S (single-anastomosis duodeno-ileal bypass with sleeve gastrectomy).

In SADI-S, the duodenum is divided just past the pylorus and connected end-to-side to a loop of ileum, so all food follows the bypass. Unlike a full duodenal switch, SADI-S uses only one intestinal connection, which makes it simpler with fewer suture lines while still giving most of the switch's metabolic power. It is the most natural "next step" after MagDI, because MagDI is essentially a partial version of the same idea.

Dr. de la Cruz-Muñoz performs SADI-S and complex revisional surgery and has extensive experience with magnetic anastomosis. He tailors the conversion to your anatomy and nutritional status.

MagDI leaves the duodenum in continuity, with a side opening to the ileum. In conversion to SADI-S:

• The duodenum is divided below the pylorus, ending the bypass of food down the original route.
• A single duodeno-ileal anastomosis is made to an ileal loop, usually 250–300 cm from the end of the small intestine. Sometimes the existing MagDI connection site is used, and sometimes a new one is created at a measured distance.
• The common channel (the length of intestine where food and bile mix) is kept long enough to protect protein and vitamin absorption.
• The sleeve is evaluated and revised if it has stretched.

The pylorus is preserved, so stomach emptying stays controlled and dumping syndrome is uncommon.

Duodenal Switch or SADI-S After MagDI?

Each option turns MagDI's partial diversion into a complete one. SADI-S needs only one connection and usually keeps a longer common channel, so it is simpler and easier on nutrition, with slightly less effect. A duodenal switch adds a second connection and a shorter common channel for maximum weight loss and diabetes control, at a higher nutritional cost. Dr. de la Cruz-Muñoz weighs your BMI, metabolic disease, reflux, nutrition labs and how reliably you can take supplements when recommending one over the other.

• Converts partial diversion to full diversion for greater weight loss and diabetes control
• Only one intestinal connection, so the operation is shorter and has fewer potential leak sites than a full duodenal switch
• Pylorus preserved, with less dumping and fewer marginal ulcers than gastric bypass
• A longer common channel than a classic duodenal switch, which is generally gentler on nutrition
• Can often build on the existing anatomy

• Not enough weight loss, or weight regain, after MagDI
• Persistent type 2 diabetes, prediabetes, or fatty liver disease
• Normal or correctable nutritional labs before surgery
• Willingness to take lifelong supplements and keep regular follow-up

Patients with severe reflux may need a different approach, because the sleeve remains in place. Those needing the maximum possible effect may be better suited to conversion to a full duodenal switch. Evaluation includes endoscopy, a contrast study, nutrition labs, and a dietitian review.

1. Access: laparoscopic or robotic, under general anesthesia.
2. Inspection: adhesions are released, and the sleeve, the duodenum and the MagDI connection are identified.
3. Measurement: the small intestine is measured to choose the ileal loop for the new connection.
4. Duodenal division: the duodenum is divided just past the pylorus.
5. Anastomosis: the duodeno-ileostomy is created and leak-tested. The MagDI site is incorporated or closed as planned.
6. Sleeve and hiatus: the sleeve is revised if needed and any hiatal hernia repaired.

• Surgical risks: bleeding, infection, blood clots, anesthesia risk, and leak at the new duodeno-ileal connection, all somewhat more likely than in a first operation because of scar tissue.
• Nutritional risks: complete diversion absorbs less fat and protein, raising the risk of protein malnutrition, vitamin A, D, E and K deficiencies, iron deficiency, and low calcium with bone loss.
• Bowel changes: more frequent, looser stools and gas, especially after fatty meals.
• Need for further adjustment: in an occasional patient who develops malnutrition, the common channel length has to be revised.

Lifelong supplements, routine blood work and a high-protein diet keep these risks manageable, but they do not make them disappear. For that reason, SADI-S conversion is offered only to patients with a clear need who commit to follow-up.

• Hospital stay: usually one to two nights.
• Diet: over roughly six weeks, move from clear liquids to protein shakes and full liquids, then pureed and soft foods, and finally regular textures.
• Activity: you walk on the day of surgery, most people are back at desk work within two to three weeks, and heavy lifting is avoided for four to six weeks.
• Supplements: a SADI-S regimen, including a high-potency multivitamin, fat-soluble vitamins A, D, E and K, calcium citrate, and iron as needed, begins once you are eating.
• Labs: nutrition labs at about 3, 6 and 12 months, then at least yearly for life.

Most patients achieve meaningful additional weight loss over the following one to two years, along with better blood-sugar control. Long-term health depends on supplements, yearly labs, and a high-protein diet. If you have had MagDI and are not where you hoped to be, call 305-692-0392 to review your options.

What the Research Shows

• The first-in-human magnetic duodeno-ileostomy study enrolled 15 adults with type 2 diabetes; the magnet-formed connection produced no leaks, bleeding, infections, strictures or deaths, and every connection was still open at one year. Patients followed for weight lost 38.8% of excess weight, and HbA1c dropped from 8.2% to 6.6% (Gagner et al., Journal of the American College of Surgeons, 2025).
• In patients revised after a failed band, a single-anastomosis duodenal switch produced more weight loss than conversion to sleeve, and prior surgery did not reduce its effect (Pearlstein et al., Obesity Surgery, 2019). Data specific to MagDI-to-SADI-S conversion are not yet published.

Among patients who had limb distalization, shorter absorptive lengths predicted severe protein-energy malnutrition, while a total alimentary limb of at least 350 cm was associated with lower risk (systematic review and meta-analysis, Annals of Surgery, 2021).

More in MagDI Revisions

Related procedures: MagDI to Duodenal Switch Conversion, Magnetic Duodeno-Ileal Bypass with Sleeve, Sleeve Gastrectomy to Magnetic Duodeno-Ileostomy Conversion, MagDI Revision for Weight Regain, MagDI Revision for Malnutrition. Related primary operations: SADI-S. For an overview of all options, see Revisional Bariatric Surgery.

Conditions treated: Weight Regain, Malnutrition After Bariatric Surgery, Protein Malnutrition.

Dr. Nestor de la Cruz-Muñoz is a nationally recognized bariatric and metabolic surgeon with extensive experience in advanced metabolic procedures and complex revisional surgery. He applies that expertise with the goal of a safe MagDI takedown and precise SADI-S reconstruction.

Over more than 25 years in bariatric surgery, Dr. de la Cruz-Muñoz has completed more than 9,000 bariatric operations, a volume few surgeons reach. That depth is what he draws on when completing a partial MagDI diversion as a SADI-S.

When conversion is done for weight regain or inadequate weight loss, the amount of additional weight loss varies from patient to patient.

Converting MagDI to a full SADI-S brings powerful improvement in type 2 diabetes, insulin resistance, hypertension, dyslipidemia, sleep apnea and fatty liver disease.

Keeping results after SADI-S depends on protein-forward eating, resistance training, steering clear of slider foods, protecting muscle mass, and steady metabolic follow-up.

SADI-S may improve reflux in some patients but may worsen it in others. Patients with severe GERD may benefit more from conversion to gastric bypass. Hiatal hernia repair is performed when needed.

If needed later, a SADI-S created from a MagDI can be adjusted by changing limb lengths, tightening the sleeve, or converting to a full duodenal switch (DS) for the greatest metabolic effect.

Protecting lean mass matters after SADI-S. We coach patients to put protein first, train with resistance, stay hydrated, and track body composition over time.

Because MagDI is still an emerging procedure, insurance coverage varies. A revision to SADI-S may be covered when medical necessity is documented.

Preparation for converting MagDI to SADI-S typically includes blood tests, imaging, an endoscopy, nutrition counseling, a psychological evaluation, and medication changes as needed.

After conversion to SADI-S, meals move from clear and full liquids to purees and soft foods before regular textures return. Hitting protein goals and staying on vitamin supplements is essential.

After a MagDI-to-SADI-S conversion, you walk on the day of surgery, keep to light activity for the first two weeks, and usually add resistance training around weeks 4–6.

Please send the operative report from your MagDI procedure, including the magnet system used and the location of the connection. That allows the conversion to be planned precisely before you arrive. Most patients stay approximately one week, and nutrition labs can be drawn at home and reviewed virtually.