Horizons in Bariatric Surgery: the SADI-SJuly 6, 2016
The Loop Duodenal Switch also known as the SADI-S (Single Anastomosis Duodenal-Ileal Bypass with Sleeve Gastrectomy) is an investigational bariatric procedure that has been generating increasing interest in the US over the past 3 to 4 years. The SADI-S is quickly becoming many patients’ weight loss surgery of choice as early results have demonstrated that patients may on average lose 80-95% of their unhealthy weight and may cure more than 95% of type 2 diabetes.
The first part of the Loop Duodenal Switch (SADI-S) is the formation of a Sleeve Gastrectomy, which removes approximately 80% of the stomach. After this, the first portion of the small intestine (the duodenum) is divided at the end of the sleeve. The small intestine is then measured 10 feet from the other end of the small intestine and this loop is brought up and connected to the end of the sleeve, bypassing all but roughly 10 feet of the small intestine. The procedure restricts the amount of food that can be consumed and prevents the absorption of unwanted calories. Ideal candidates for the surgery are those with a body mass index (BMI) of 50 or more or those with type 2 diabetes who are also highly committed to daily vitamin supplementation for life. The surgery lasts less than 2 hours. Like other bariatric surgical procedures, patients often leave the hospital within 2 days and can resume solid foods within 6 weeks.
The SADI-S is Different than the Duodenal Switch (DS)
The SADI-S should be considered a completely different operation than the traditional Duodenal Switch (DS).
This is a fact that has been recognized by bariatric surgical societies (MBSAQIP, ASMBS, and ACS) and is one reason that it is still considered an investigative operation in the US.
The traditional DS bypasses a more significant portion of the small intestine leading to persistent malabsorption of vitamins, minerals and/or protein. In a small subset of patients, these deficiencies cannot be fully corrected using oral replacement methods. Instead of leaving only 2-5 feet of the small intestinal length to absorb nutrients like the DS, the SADI-S preserves approximately 10 feet of small intestinal absorptive length. This is a critical difference. In the first Spanish study of the SADI-S, when the length of downstream small intestine increased to at least 8 feet in length, no long-term nutrient deficiencies were noted as long as patients were very compliant with replacement regimens. This has been our early experience as well.
When compared to the RNY Gastric Bypass, the long-standing gold standard for weight loss and diabetic treatment, the SADI-S may carry advantages in terms of better weight loss and improved diabetic cure rates. Traditional Gastric Bypass surgery has transformed many lives with a 65-80% loss of unhealthy weight and an early diabetic cure rate of around 90%. In comparison, early results from the SADI-S indicate a superior weight loss profile of 80-95% of unhealthy body weight. Similarly, initial studies are indicating a diabetic cure rate above 95%. This improved diabetic cure rate may be due to more than the additional weight loss many patients experience with the SADI-S. Certain intestinal hormones, known as incretins, involved in glucose sensitivity have even become targets for diabetic medications over the past decade. These may be more favorably altered by the SADI-S than the Gastric Bypass and may be partly responsible for the additional diabetic benefit.
Potential Complications of the SADI-S?
Just like the Sleeve Gastrectomy or Gastric Bypass, there is potential for a gastrointestinal leak from one of the staple lines. If a leak were to occur a person could become very sick and need additional surgery. Theoretically, there may be a slightly greater risk of a leak with a Duodenal Switch (either traditional or loop) because the divided portion of the duodenal stump end may be more fragile. As a result, in the bariatric community, we are exceedingly careful with the duodenal stump. Although in the bariatric community, we respect this potential for additional risk, the early experience has not shown a higher leak rate with the SADI-S.
Similar to the Sleeve, the SADI-S can increase symptoms of acid reflux acid reflux in up to 20% of patients and even occasionally can cause bile reflux from the loop into the stomach.
Even though the early experience has demonstrated safety in terms of protein or vitamin malnutrition, it is extremely important to understand that the SADI-S should be reserved for patients who have a very high level of dedication to excellent compliance with all protein and vitamin supplementation regimens every day for the rest of their lives. It should also be noted that this may be a bigger commitment that they might have to make for a bypass both in terms of more vitamins and greater cost of supplements that are not covered by insurance. If a person does not commit to this level of consistency, then vitamins, other nutrients, and ultimately long-term health can certainly be at risk. Additionally, patients can expect about two looser bowel movements per day. However, because the SADI-S preserves the emptying valve to the stomach, the SADI-S does not result in dumping syndrome for most patients and may have a lower risk of post-operative gastric ulceration.
For Patients Considering the SADI-S
Good candidates for the SADI-S are highly motivated, very insightful, and dedicated to very consistent vitamin and protein supplementation.
They actively plan to follow-up at all recommended time points and readily institute all recommended changes. They are proactive and foster a close relationship with not only their surgeon but their entire bariatric multispecialty care team and keep all appointments. They are also consistently and intentionally dedicated to maintaining their health long-term.
Patients who may not be good SADI-S candidates are patients who do not approach this operation with respect and realistic expectations. Vitamins can be costly and patients who struggle with limited financial resources or social support may not be able to consistently maintain a healthy life long-term. Patients who require long-term steroids, NSAIDs, or use substances such as nicotine, caffeine, alcohol, or illicit drugs may not be good candidates because these substances can cause irritation leading to ulcers. Also, patients who suffer from irritable bowel syndrome and pain/diarrhea prior to surgery will not be happy with the increased bowel movement frequency following the SADI-S. Finally, patients with severe reflux may need alternative weight management treatments as the SADI-S can worsen reflux in some patients.
Final SADI-S Takeaways?
- Although very promising, the SADI-S is still an investigative operation in this country and can only be performed at a Center of Excellence (COE) that is approved for such a trial.
- The early experience indicates that the SADI-S may offer better weight loss and potentially superior diabetic cure rate than the gastric bypass or sleeve gastrectomy.
- While the SADI-S does appear to be safer in terms of possible vitamin deficiencies than the traditional DS, it should only be considered a safe option for patients who can consistently commit to detailed compliance with all recommendations daily for the rest of their lives.
ABOUT THE AUTHORDr. Josh Long joined Parker Adventist Hospital where he collaborated to pioneer the loop duodenal switch (SADI-S) as a more effective alternative to the gastric bypass. He has gained national recognition for his quality of care; he serves as a national bariatric program site reviewer and is also currently participating as a co-author for the national obesity algorithm. Dr. Long is a bariatric surgeon at the Bariatric and Metabolic Center and considers it an honor to serve every patient with the highest quality of care.