The Duodenal Switch (DS) is one of the most powerful tools that we have in modern weight loss surgery. It leads to significant weight loss and improvement in medical co-morbidities, however, many surgeons do not perform the DS because it is thought to have greater risks and difficulty in performing the surgery. In an effort to increase the safety and speed of the surgery, a new form of the DS has been developed – the Single Anastomosis Duodeno-Ileal bypass with Sleeve Gastrectomy (SADI-S). This article will explore the similarities and differences of SADI and DS surgeries.
What is the anatomy of the Duodenal Switch as compared to other types of weight loss surgery? Understanding what each surgery consists of can be confusing, in part because there have been several adjustments over time to the types of bariatric surgery that we perform.
The Duodenal Switch was initially developed as a variation of a surgery called the Biliopancreatic Diversion (BPD); you may see the Duodenal Switch referred to as either the DS-BPD or just DS – both mean the same thing. The original BPD was like a Gastric Bypass with a bigger stomach pouch but with a much, much longer Y-shaped intestinal bypass. The BPD consisted of the stomach being divided in half horizontally, and after bypassing a very long segment of the intestines, the distal (or farthest away) piece of small intestine (called the ileum) was attached to the stomach.
The bile and pancreatic digestive juices were not allowed to mix with the food until the very end of the small intestine. The BPD caused a significant amount of dumping and malnutrition in part because of the very short common channel (CC), which is where the food and digestive juices are finally allowed to mix.
The Duodenal Switch:
In 1988, the BPD was modified to the DS-BPD where instead of transecting the stomach in half horizontally, it was made into a Sleeve Gastrectomy shape. The ileum (distal small intestine) was then attached to the sleeve just after the pylorus. The intestinal bypass was otherwise the same as the BPD, although the Common Channel was allowed to be longer to help reduce malnutrition.
These changes allowed patients to achieve was a reduction in portion sizes that could be eaten in any one setting, and decreased dumping because the pylorus, or muscle located at the end of the stomach, was left intact. Early on, and even sometimes today, the Duodenal Switch was staged, or broken up into two procedures; this was done in order to reduce the risk of doing one big surgery which could take several hours.
The Sleeve Gastrectomy was the first part, followed a few months later by the intestinal bypass. Some patients were happy just with the first part of the procedure- the Sleeve Gastrectomy- and did not want to proceed with the intestinal portion. That is how the stand-alone Vertical Sleeve Gastrectomy started to be used as its own type of weight loss surgery. Of note, the Sleeve Gastrectomy that accompanies the Duodenal Switch is traditionally slightly larger than that of a stand-alone sleeve gastrectomy, in order to allow DS patients to eat a large enough portion of food to get sufficient nutrients (specifically protein) in each day.
The most recent step in this story of evolving surgery was the development of the SADI-S, or Single Anastomosis Duodeno-Ileal bypass with Sleeve Gastrectomy. “Anastomosis” (an-ast-o –MO-sis) is a medical word that means “surgical connection”. When two pieces of intestine, or stomach and intestine, are brought together with staples or sewing, that is called an anastomosis.
As you may know from your research, any time the intestine is cut, and then sewn together with another piece of stomach/intestine, that connection could result in a leak of gastrointestinal contents. Because of the statistical increase for the risk of a leak with each additional connection, the idea behind the SADI-S was to just have ONE anastomosis. Another theoretical advantage is that because fewer connections are required, the surgery could take less time.
In the SADI-S, first a Sleeve Gastrectomy is mad