Single anastomosis duodenal switch, also known as Single Anastomosis DuodenoIleal Bypass (SADI) is a procedure that is being discussed in literature. There have been a few series of case reports that have been published in the last few years. I would like to review the procedure and share my opinion.
The theory behind the SADI has been to simplify the duodenal switch procedure. In “classical” duodenal switch procedure, the small bowel is divided in two places, (duodenum, and distal ileum) and two anastomosis are created (duodeno-ileostomy, and ileo-lieostomy). This can theoretically provide two potential places for leak, bleeding, adhesions as complications. In SADI, there is a single bowel division of the duodenum and a single anastimosis of the duodenum and the ileum. The sleeve component of the procedure is the same for both procedures. This is where their similarities end.
In the duodenal switch operation, the bowel is partitioned in to two parallel limbs- one that carries the biliopancreatic juices and a parallel limb that bring the food down from the post pyloric duodenum. They then join and form the common channel. The length of the biliopancreatic limb is so long that it does not allow bile to reflux back into the duodenum or back to the stomach causing the complication of bile reflux gastritis. With the single anastomosis of the SADI, the length of the bowel where the bile meets the duodenum is shorter than it is in normal anatomy. This significantly increases the possibility of the bile reflux. The second difference is the selective nature of the reduced absorption of the fat in the duodenal switch, in comparison to that of the carbohydrates. Duodenal switch operation has two absorptive lengths- the Alimentary channel, which is involved with protein and carbohydrate absorption, and the common channel that absorbs, fat, protein and carbohydrates. One can make changes to the common channel and impact the fat absorption significantly more than that of the carbohydrate and the proteins. In SADI procedure, that common channel and the alimentary limb are both the same- there is no way to selectively adjust the fat absorption without making significant changes to that of the protein and carbohydrate absorption.
There are a number of publications that have reported the short-term outcome of the SADI procedure. They appear promising, but they are short-term results. Long-term data is needed. If the outcome does not change significantly over time, then I could see a role for SADI in the treatment for obesity. In the mean time, patients need to be made aware that the suggestion that SADI is the same as the duodenal switch is probably not correct since we do not have the data to support this oversimplification.