People with morbid obesity and Type 2 diabetes seeking bariatric surgery for weight loss and improved metabolic function have traditionally undergone procedures such as the duodenal switch, the gastric bypass, and the sleeve gastrectomy.
Now, weight loss experts like Matthew Spann, M.D., chief of the division of general surgery and director of metabolic and bariatric surgery at Vanderbilt University Medical Center, are reviving a different surgical method that allows for even better patient outcomes.
In May 2024, Spann joined his colleague Joseph Broucek, M.D., director of general surgery at VUMC, in performing a single anastomosis duodenal switch with sleeve gastrectomy (SADI-S), the first to take place at Vanderbilt. Support for the SADI-S is emerging following improvements in controlling side effects and recently realized hormonal benefits of this procedure.
“Part of the reason we reconsidered this operation is that the number of patients that we see with a body mass index above 60 is much greater than it was, even just five years ago,” Spann said. “More patients who initially had good success with sleeve gastrectomy continue to suffer from obesity and will need another option to help get them into a healthy range.”
He explained that procedures such as sleeve gastrectomy that suppress hunger or just make the stomach smaller don’t affect hormones that control blood sugar and aid in additional long-term weight control.
A deeper understanding of vitamin absorption and GI tract functions have prompted alterations in some older procedures to achieve longer lasting results.
Traditional Surgeries
In the early period of bariatric surgeries, it was common for clinicians to recommend the duodenal switch, in which a laparoscopic sleeve gastrectomy is performed, followed by an intestinal bypass.
The gastrectomy incisions are made in the upper abdomen to remove roughly 80 percent of the stomach, prompting hormone changes to suppress hunger. Then the small intestine is rerouted to bypass the lower stomach and upper small intestine, slowing digestion in the gastrointestinal tract.
However, this procedure started to lose popularity over time.
“Some of the clinicians started to notice that after the sleeve gastrectomy, certain patients were not coming back for the intestinal bypass,” Spann said. “This led to the sleeve gastrectomy becoming a standalone procedure for weight loss. However, it was not as effective for long-term weight loss for certain patients.”
A common alternative has been the gastric bypass, where a gastric pouch is created in the stomach and the small bowel is rerouted, bypassing about a third of the small intestine.
“With the gastric bypass, you’ll lose a bit less weight than with the duodenal switch. Gastric bypass is much better, however, when it comes to acid reflux, vitamin deficiencies and GI side effects,” Spann said.
SADI-S for Hormone Release
In SADI-S, the original duodenal switch is simplified, creating just one connection with the bypass and rolling the sleeve gastrectomy into the same procedure.
“After performing the sleeve gastrectomy, we bypass the proximal small intestine, connecting the duodenum with about 300 remaining centimeters of small bowel before it attaches to the large bowel,” Spann said.
This leaves only one-third to one-fourth of the small intestine absorption intact, thus decreasing overall nutrient absorption. When the nutrients arrive quickly at the terminal ileum, a massive release of the body’s natural hormones occurs, deploying about 40 that impact hunger and blood glucose control, he said.
“It’s this that makes this operation so popular. Functionally, this drives more weight loss and better diabetes control. Whereas, the gastric bypass has about a 65 percent chance of curing patients with advanced diabetes, SADI-S has shown to improve upon that figure by about 10 percent due to this greater release of hormones.”
“Whereas the gastric bypass has about a 65 percent chance of curing patients with advanced diabetes, SADI-S has shown to improve upon that by about 10 percent, due to the greater release of hormones.”
Patient Selection and Monitoring
Long-term, the SADI-S procedure has both benefits and potential drawbacks when compared with the gastric bypass alone or the duodenal switch.
Fewer ulcers or bowel obstructions occur with SADI-S, and avoiding the second anastomosis means fewer complications. However, the positioning of the one anastomosis can increase leak risk.
“Patients can experience a higher risk of diarrhea, esophageal reflux, bile reflux and vitamin deficiencies,” Spann said of the SADI-S procedure. “For this reason, patients have to be committed to taking supplemental vitamins and proton-pump inhibitors if the reflux is esophageal.”
Because of these risks and requirements, the SADI-S procedure is ultimately reserved for a smaller group of patients – those with a body mass index above 60 and with insulin-dependent type 2 diabetes.
“Internationally, it represents about 3 to 4 percent of the total bariatric surgeries performed, and I think is unlikely to exceed 5 to 8 percent,” he said. “It’s not taking the place of a sleeve gastrectomy or gastric bypass. It’s just an option for patients for whom those particular tools aren’t, statistically, going to get them down to a healthy weight.”
