Gastric Bypass to MagDI Conversion

Roux-en-Y gastric bypass is a durable, effective operation (see Gastric Bypass (RYGB)). Some patients, however, develop weight regain or complications that will not resolve. These include recurrent marginal ulcers, severe dumping, post-bypass hypoglycemia, chronic nausea and pain, or malnutrition (Vosburg et al., ASMBS Reoperative Surgery Review, Surgery for Obesity and Related Diseases, 2026). For the complications, reversing the bypass is often the definitive fix, but weight recurrence is the most common problem after reversal, occurring in 28.8% of patients (Shoar et al., Surgery for Obesity and Related Diseases, 2016). In one comparison, patients reversed to normal anatomy regained 14.2 kg on average, while those reversed to sleeve anatomy lost 4.8 kg (Vosburg et al., ASMBS Reoperative Surgery Review, Surgery for Obesity and Related Diseases, 2026).

Gastric bypass to MagDI conversion builds on the sleeve-anatomy approach. The bypass is rebuilt as a sleeve gastrectomy, and a side-to-side duodeno-ileostomy is created with magnetic compression instead of staples or sutures. Two magnets, one in the duodenum and one in the ileum, are delivered endoscopically and aligned laparoscopically. Over a few weeks they fuse the bowel walls into an opening and then pass naturally (Gagner et al., Surgery for Obesity and Related Diseases, 2024).

MagDI is a new technology. Across 12 prospective studies, pooled device-related leak was 0% and 30-day mortality was zero. The authors rated the certainty of the evidence low to very low, because the studies were small, industry-sponsored, and done at experienced investigational centers (Noel et al., Surgery for Obesity and Related Diseases, 2026). No published series has reported outcomes for converting a gastric bypass to MagDI specifically. The data on this page come from the two components: reversing a bypass to sleeve anatomy and MagDI after a sleeve.

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The operation combines restriction, hormonal change, and partial malabsorption:

• Rebuilding as a sleeve. The gastric pouch is reconnected to the bypassed stomach (a gastrogastrostomy), and the stomach is then trimmed into a sleeve. This restores food passage through the pylorus and duodenum, which resolves many bypass-specific problems such as dumping, hypoglycemia, and marginal ulcers (Vosburg et al., ASMBS Reoperative Surgery Review, Surgery for Obesity and Related Diseases, 2026).

• Adding a magnetic duodeno-ileal pathway. The magnets join the first part of the duodenum to the ileum, usually about 250–300 cm from the ileocecal valve (Cadière et al., Journal of Gastrointestinal Surgery, 2024; Nassar et al., Obesity Surgery, 2026).

• Partial diversion, not full exclusion. Because the connection is side-to-side, normal intestinal continuity is kept. An isotope study found that about 19% of a meal passed directly into the ileum (Cadière et al., Journal of Gastrointestinal Surgery, 2024). This partial diversion may lower the risk of severe malabsorption compared with BPD-DS or SADI-S (Chiappetta et al., Obesity Surgery, 2026).

• No staples or sutures in the bowel connection. Magnetic compression avoids an enterotomy and leaves no retained staples or sutures at the duodeno-ileal connection (Nassar et al., Obesity Surgery, 2026). It also avoids the duodenal stump, a recognized leak site after conventional bypass-to-SADI-S conversion (Moon et al., Surgical Endoscopy, 2020).

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• Fixes bypass complications while limiting weight regain. Reversal to sleeve anatomy led to weight loss rather than the regain seen with reversal to normal anatomy (Vosburg et al., ASMBS Reoperative Surgery Review, Surgery for Obesity and Related Diseases, 2026). The MagDI is designed to add further metabolic effect on top of that.

• No device-related leaks in published series. Pooled device-related leak rate was 0%, with no 30-day deaths (Noel et al., Surgery for Obesity and Related Diseases, 2026). In the multicenter study, all anastomoses formed and all magnets passed, with no leak, bleeding, obstruction, or infection related to the device (Gagner et al., Surgery for Obesity and Related Diseases, 2024).

• Short magnet step. As a standalone revision after a sleeve, the MagDI step averaged about 67 minutes, with a median hospital stay of one day (Nassar et al., Obesity Surgery, 2026). In the Italian multicenter study, operative time averaged 73 minutes and hospital stay 1.6 days (Chiappetta et al., Obesity Surgery, 2026).

• Possibly gentler on nutrition. Only isolated, correctable vitamin deficiencies were reported in early follow-up (Chiappetta et al., Obesity Surgery, 2026). Protein-energy malnutrition (9.3%) was confined to one different magnet device, not the linear MagDI system (Noel et al., Surgery for Obesity and Related Diseases, 2026).

• Better blood sugar. All patients with type 2 diabetes improved after MagDI (Gagner et al., Surgery for Obesity and Related Diseases, 2024).

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• Bypass patients who need reversal for complications, such as recurrent marginal ulcer, severe dumping, post-bypass hypoglycemia, chronic nausea or pain, or malnutrition, and who want to protect their weight loss (Vosburg et al., ASMBS Reoperative Surgery Review, Surgery for Obesity and Related Diseases, 2026). See Gastric Bypass Reversal, Gastric Bypass Revision for Marginal Ulcer, and Gastric Bypass Reversal for Chronic Pain and Functional Obstruction.

• Bypass patients with weight regain who want a duodeno-ileal operation and accept that evidence for this exact pathway is still emerging, after a full discussion of SADI-S and duodenal switch conversion (see Gastric Bypass Revision for Weight Regain).

• Patients who are nutritionally stable, with no severe protein malnutrition at the time of surgery.

• Patients without significant reflux, erosive esophagitis, or Barrett's esophagus, because a sleeve-based anatomy can worsen reflux (see GERD/Reflux Considerations).

• Patients committed to lifelong follow-up, vitamins, and lab monitoring.

Who is usually better served by another operation:

• Patients with severe reflux are usually better off keeping the bypass (see Gastric Bypass (Roux-en-Y) for GERD and Hiatal Hernia Repair After Gastric Bypass).

• Patients whose main goal is maximum weight loss may do better with Gastric Bypass to SADI-S Conversion or Gastric Bypass to Duodenal Switch (DS) Conversion, which have longer follow-up (El-On et al., Obesity Surgery, 2026; Roulet et al., Surgery for Obesity and Related Diseases, 2024).

• Patients with excessive weight loss or malnutrition need a different approach (see Gastric Bypass Reversal for Excessive Weight Loss and Gastric Bypass Reversal for Malnutrition).

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The operation is usually staged to separate its two highest-risk steps.

• Stage 1: Bypass to sleeve. Done laparoscopically or robotically. The gastrojejunostomy is taken down and the pouch is reconnected to the remnant stomach. The Roux limb is reconnected or removed depending on total bowel length; a remaining intestinal length of at least 4 m is generally required before the limb is removed (Gero et al., Obesity Surgery, 2025). A sleeve gastrectomy is then created. Some surgeons delay the sleeve itself until a later step. In a two-stage bypass-to-SADI-S series, the sleeve was performed 6–8 months after the reversal, with no complications in five patients (Sánchez-Pernaute et al., Obesity Surgery, 2024).

• Stage 2: MagDI. Under general anesthesia, one magnet is placed endoscopically in the post-pyloric duodenum. A second magnet is guided laparoscopically to the ileum, and the two are aligned. Over about 1–3 weeks the magnets compress the tissue between them, and the bowel heals into a side-to-side duodeno-ileostomy. The paired magnets pass naturally, at a median of 35 days after a prior sleeve (Gagner et al., Surgery for Obesity and Related Diseases, 2024; Gagner et al., Journal of the American College of Surgeons, 2025).

• Single-stage option. In selected patients, the sleeve and MagDI can be done at one operation. Concurrent MagDI with sleeve has been studied only in primary (non-revisional) patients (Gagner et al., Surgery for Obesity and Related Diseases, 2024).

You can watch the magnetic duodeno-ileostomy technique in our GT Metabolic Duodenoileostomy Animation video.

• Leak at the gastrogastrostomy or sleeve staple line is the main surgical risk. Leaks occurred in 25% of patients reversed to sleeve anatomy, compared with 7.7% of those reversed to normal anatomy (Vosburg et al., ASMBS Reoperative Surgery Review, Surgery for Obesity and Related Diseases, 2026). In a series of 12 bypass-to-sleeve conversions, 4 patients had 7 major complications, including leak, bleeding, portal vein thrombosis, and pulmonary embolism (Carter et al., Surgery for Obesity and Related Diseases, 2015). The staple line crosses an older anastomosis and can leave areas with limited blood supply, which is the main reason for staging (Sánchez-Pernaute et al., Obesity Surgery, 2024).

• Overall complications of conventional bypass-to-duodenal-switch conversion, for comparison: 17.2% at 30 days, with a 5.8% leak rate after conversion to BPD-DS (Serra et al., Surgical Endoscopy, 2026).

• Magnet-stage risks. Most adverse events were mild (Clavien-Dindo grade I–II), and there were no device-related leaks, bleeding, obstruction, or deaths (Gagner et al., Surgery for Obesity and Related Diseases, 2024). In the Italian multicenter series of 28 patients, there were three procedure-related serious adverse events: one ileal perforation, one case of liver insufficiency that led to reversal, and one trocar-site hernia (Chiappetta et al., Obesity Surgery, 2026).

• Nutritional deficiencies. Vitamin D, B12, A, K, and iron deficiencies were reported and corrected with oral supplements (Chiappetta et al., Obesity Surgery, 2026). Long-term nutritional surveillance is mandatory.

• New or worse reflux. Severe reflux occurred in 10.2% of patients after bypass reversal (Shoar et al., Surgery for Obesity and Related Diseases, 2016).

• Less weight loss than expected. As a standalone revision after a sleeve, MagDI produced modest weight loss, and early results varied widely between patients (Nassar et al., Obesity Surgery, 2026).

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Stage 1 usually requires 2–3 nights in the hospital. The two-stage bypass-to-SADI-S series averaged 2.5 days (Sánchez-Pernaute et al., Obesity Surgery, 2024). Patients follow a liquid diet for about a month, then soft foods, with at least 100 g of protein per day in that protocol (Sánchez-Pernaute et al., Obesity Surgery, 2024). The MagDI stage typically involves a one-day stay (Nassar et al., Obesity Surgery, 2026). Most patients do not notice the magnets passing over the following weeks. Walking starts on the day of surgery, and heavy lifting is avoided for several weeks after each stage.

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Long-term data on this conversion do not yet exist. For the components, the longest MagDI follow-up is one year. In a small group of 10 primary patients, all anastomoses remained open with satisfactory diameters at one year (Cadière et al., Journal of Gastrointestinal Surgery, 2024). Reversal to sleeve anatomy was followed for an average of 5.3 years without the weight regain seen after full reversal (Vosburg et al., ASMBS Reoperative Surgery Review, Surgery for Obesity and Related Diseases, 2026). Because obesity is a chronic disease, many patients benefit from anti-obesity medication and lifelong follow-up.

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More in Gastric Bypass Revisions

Related procedures: Gastric Bypass to OAGB Conversion, Transoral Outlet Reduction, Gastric Bypass Revision for Weight Regain, Gastric Bypass Pouch Reduction, Gastric Bypass Limb Lengthening, Gastric Bypass Distalization. Related primary operations: Gastric Bypass, Magnetic Duodeno-Ileal Bypass with Sleeve. For an overview of all options, see Revisional Bariatric Surgery.

Conditions treated: Weight Regain, Inadequate Weight Loss, Marginal Ulcer, Internal Hernia, Post-Bariatric Hypoglycemia, Dumping Syndrome.

This operation combines two of the most demanding procedures in bariatric surgery: reversing a gastric bypass and creating a duodeno-ileal pathway. It also uses a new magnetic technology that only a small number of surgeons in the country offer. Dr. Nestor de la Cruz-Muñoz, MD, FACS, DABOM, has performed and revised gastric bypasses for decades. He is a board-certified surgeon and a diplomate of the American Board of Obesity Medicine, and he served for 10 years as a fellowship program director, teaching surgeons the reoperative techniques these cases require.

He is also among the surgeons offering magnetic duodeno-ileostomy, alongside every conventional option. These include Gastric Bypass Reversal, Gastric Bypass to SADI-S Conversion, Gastric Bypass to Duodenal Switch (DS) Conversion, Gastric Bypass Distalization, and anti-obesity medication. That range lets him recommend MagDI only when it is the right fit. He also tells patients plainly where the evidence is still early, so every decision is an informed one.

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Dr. de la Cruz-Muñoz has been performing bariatric surgery for over 25 years and has completed more than 9,000 bariatric operations — a volume few surgeons reach.

No outcome data exist for this exact conversion. The closest data:

• Reversal to sleeve anatomy: an average weight loss of 4.8 kg (Vosburg et al., ASMBS Reoperative Surgery Review, Surgery for Obesity and Related Diseases, 2026).

• MagDI after a prior sleeve: about 7.0% total weight loss and 17.4% excess weight loss at 6 months (Gagner et al., Surgery for Obesity and Related Diseases, 2024). Pooled revisional MagDI data showed 5.4% at 6 months and 5.3% at 12 months (Noel et al., Surgery for Obesity and Related Diseases, 2026).

• MagDI with concurrent sleeve in primary patients: 28.1% at 6 months (Gagner et al., Surgery for Obesity and Related Diseases, 2024) and 34.2% at one year in 10 patients (Cadière et al., Journal of Gastrointestinal Surgery, 2024).

• Comparison: conventional bypass-to-SADI-S/BPD-DS conversion reached 25.0% total weight loss at 12 months (Moon et al., Surgical Endoscopy, 2020).

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All patients with type 2 diabetes improved after MagDI (Gagner et al., Surgery for Obesity and Related Diseases, 2024). In a first-in-human study of patients with diabetes, HbA1c fell from 8.2% to 6.6% at one year with a related magnetic device (Gagner et al., Journal of the American College of Surgeons, 2025). Reversing the bypass also resolved reactive hypoglycemia in 75% of affected patients (Vosburg et al., ASMBS Reoperative Surgery Review, Surgery for Obesity and Related Diseases, 2026).

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Long-term success requires protein-forward nutrition, resistance training, avoiding slider foods, maintaining muscle mass, and consistent metabolic follow-up. Body composition monitoring is essential.

Converting a bypass back to sleeve anatomy gives up the bypass's anti-reflux protection. After bypass reversal, severe reflux occurred in 10.2% (Shoar et al., Surgery for Obesity and Related Diseases, 2016). Patients with significant reflux, erosive esophagitis, Barrett's esophagus, or a large hiatal hernia are generally poor candidates and are usually better served by keeping the bypass (see Gastric Bypass (Roux-en-Y) for GERD). Any hiatal hernia is repaired at Stage 1.

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If weight loss is not enough, options include anti-obesity medication, conversion to a conventional SADI-S or duodenal switch configuration, or adjustment of limb length. Experience with revising a MagDI is limited. Complications related to the original bypass are covered on Gastric Bypass Stricture Management, Gastric Bypass Revision for Marginal Ulcer, and Gastric Bypass Candy Cane Limb Resection.

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Preserving lean mass is essential for long-term success. Patients are guided to prioritize protein intake, resistance training, hydration, and body composition monitoring.

Coverage for revisional surgery varies widely, and only 67% of policies cover a second bariatric procedure for weight-loss failure (Gebran et al., Obesity Surgery, 2020). Reversal for documented complications such as marginal ulcer, hypoglycemia, or malnutrition is more often considered medically necessary. Because magnetic anastomosis is new, coverage for the MagDI component should be verified individually with the insurer.

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Pre-op requirements may include bloodwork, imaging, endoscopy, nutrition consultation, psychological evaluation, and medication adjustments.

Nutrition progresses from clear liquids to full liquids, purees, soft foods, and then regular textures. Protein goals and vitamin supplementation are essential.

Early walking begins immediately after surgery. Light activity continues through week 2. Resistance training typically begins at week 4–6.

Because conversion to MagDI uses a newer technique, eligibility is reviewed carefully before any travel. Send your bypass operative report, recent labs and endoscopy. Allow approximately one week in Miami for surgery and early recovery.