This operation was developed to its current form in the 1990s.
The surgery starts with a sleeve gastrectomy, then the duodenum is divided below the level of the pylorus. The ileum is then transsected 250-300 cm proximal from the colon and the distal portion is connected to the duodenum below the pylorus. This is the alimentary or digestive loop. The proximal end of the ileum is connected to the side of the digestive loop 100-150 cm proximal to the ileocecal valve. It sounds a bit complcated so review the technique on the video below. This procedure induces much more malabsorption than any other weight loss surgery and has a profound effect on type-2 diabetes. The excellent result, however, comes at a cost. Very precise and diligent LIFELONG vitamin and protein intake is mandatory to avoid serious metabolic deficiencies. Patients usually report having 2-3 bowel movements daily, but a well managed BPD-DS does not involve diarrhea. In recent years, better clinical understanding of procedures combining restrictive and malabsorptive approaches has increased the choices of effective weight loss surgery for thousands of patients. The sleeve gastrectomy and the preservation of the duodenum assure better absorption of vitamin B12 and eliminate dumping symptoms. By adding significant malabsorption, food is delayed in mixing with bile and pancreatic juices that aid in the absorption of nutrients. The result is an early sense of fullness, combined with a sense of satisfaction that reduces the desire to eat.
In addition to these mechanisms, there is a growing body of evidence pointing to substantial neurohormonal changes that are similar to but also exceed what we experience after gastric bypass surgery, that directly affect metabolism, insulin secretion and resistance, satiety and hunger. These factors explain the efficiency in bringing so many co-morbid conditions to resolution is a relatively short time period.