The Single Anastomosis Duodeno-Ileal bypass (SADI-S) is a highly effective surgical treatment for severe obesity and related metabolic diseases. It is a simplified variation of the traditional Duodenal Switch, designed to maximize weight loss and disease resolution while reducing surgical complexity. SADI-S offers a powerful option for patients requiring significant, sustained health improvement. The operation is recognized by major international surgical societies for its promising long-term results in treating high-grade obesity and Type 2 Diabetes.
Defining the SADI-S Procedure
The full name of the operation is Single Anastomosis Duodeno-Ileal bypass with Sleeve Gastrectomy, which outlines the two distinct surgical actions. The first step involves creating a vertical sleeve gastrectomy, removing approximately 75 to 80% of the stomach. This leaves a small, tubular stomach pouch that restricts the volume of food intake.
The second part involves the intestinal bypass, which is the malabsorptive component. Surgeons divide the duodenum just past the pyloric valve. The small intestine is then re-routed, creating a single connection (anastomosis) between the duodenum and a lower segment of the small intestine called the ileum.
The bypass is performed by measuring upward from the ileocecal valve (the connection of the small and large intestines). The segment where food mixes with bile and pancreatic juices, known as the common channel, is typically constructed to be 250 to 300 centimeters long. The remaining bypassed section of the small intestine, which normally handles most nutrient absorption, becomes inactive for digestion.
Physiological Mechanisms of Weight Loss
The substantial weight loss and metabolic improvements after SADI-S are driven by three physiological changes. First, the vertical sleeve gastrectomy enforces mechanical restriction, as the smaller stomach pouch limits the amount of food a person can consume.
Second, intestinal re-routing induces malabsorption. Connecting the duodenum directly to the lower ileum bypasses a large segment of the small intestine, reducing the surface area and time available for absorbing calories, fats, and complex carbohydrates.
Finally, the procedure causes profound changes in hormonal balance, suppressing appetite and improving metabolic function. Removing the stomach’s upper curvature decreases the production of ghrelin, the “hunger hormone,” reducing appetite. Rapid delivery of partially digested food to the lower small intestine triggers the release of gut hormones, such as Glucagon-Like Peptide-1 (GLP-1) and Peptide YY (PYY). These peptides increase feelings of fullness (satiety) and dramatically improve the body’s sensitivity to insulin.
Determining Patient Eligibility
The SADI-S procedure is reserved for individuals with higher levels of obesity or poorly controlled related medical conditions. The standard eligibility requirement is a Body Mass Index (BMI) of 40 or greater (severe obesity). Patients with a BMI between 35 and 39.9 may also be considered if they suffer from at least one severe obesity-related comorbidity.
Comorbidities often include Type 2 Diabetes, obstructive sleep apnea, hypertension, or high cholesterol. The procedure is also considered for patients with super-obesity (BMI of 50 or higher), where its greater power for weight loss is beneficial. SADI-S is also an option for patients who have experienced insufficient weight loss or significant weight regain after a prior bariatric operation, such as a standalone sleeve gastrectomy.
Managing Long-Term Nutritional Needs
Because SADI-S relies on malabsorption, lifelong nutritional management is a requirement. The body’s reduced ability to absorb nutrients necessitates the permanent use of specialized nutritional supplements. This prevents severe deficiencies, as the bypassed small intestine segment is the primary site for absorbing many vitamins and minerals.
Patients must take high-dose supplements, including fat-soluble vitamins A, D, E, and K, which are susceptible to malabsorption. Supplementation of Vitamin B12, iron, and calcium is mandatory to maintain healthy levels. Long-term studies indicate that even with supplementation, deficiencies in ferritin (iron storage), Vitamin D, and Vitamin A can be frequently observed, underscoring the need for specialized dosing.
Adequate protein intake (typically 80 to 100 grams per day) is important to prevent protein-energy malnutrition, a significant risk with malabsorptive procedures. Regular blood monitoring is required for life to proactively correct any emerging micronutrient deficiencies. This long-term follow-up must be managed by a multidisciplinary bariatric team, including a surgeon and a specialized dietitian.
Expected Health Outcomes
The SADI-S procedure produces some of the highest rates of sustained weight loss among all bariatric operations. Patients typically lose 75% to 87% of their excess body weight within five years, which is greater than with many other common procedures. This weight loss is associated with substantial and lasting improvements in overall health and quality of life.
The procedure is effective at resolving obesity-related metabolic diseases. Complete remission of Type 2 Diabetes is reported in a high percentage of patients, often exceeding 75%, due to the procedure’s metabolic effects. Resolution or significant improvement is common for other conditions, including obstructive sleep apnea, hypertension, and high cholesterol. Studies show that complete resolution of sleep apnea occurs in approximately 75% of affected individuals.