**4. Metabolic surgery that includes duodenal exclusion**

### **4.1 Roux-en-Y gastric bypass**

Roux-en-Y Gastric Bypass (RYGB) has four main components: a small gastric pouch, a biliopancreatic limb, a gastrojejunostomy, and a jejunojejunostomy.

### *Duodenal Exclusion: Indications and Clinical Considerations DOI: http://dx.doi.org/10.5772/intechopen.108516*

A small gastric pouch (approximately 50 mL) is constructed primarily by dividing the lesser curvature of the stomach and excluding a large portion of the fundus, entire greater curvature, and distal stomach, along with the duodenum, and first portion of the jejunum. The biliopancreatic limb consists of the remnant stomach proximally, the duodenum, and proximal jejunum and it drains the biliary and pancreatic digestive enzymes into the alimentary limb at the second, distal anastomosis. It is created by dividing the jejunum approximately 50 cm from the Treitz ligament. The Rouxen-Y technique is used to avoid a loop gastroenterostomy and the bile reflux that this may generate. A Roux limb of approximately 100 cm to 200 cm is measured past the jejunal resection, and at this point, the biliopancreatic limb is anastomosed with the alimentary limb via jejunojejunostomy. To perform the gastrojejunostomy, the Roux limb is brought up to the gastric pouch and an anastomosis created.

RYGB can be a demanding procedure with a longer learning curve, given the number of steps it requires and the need for 2 anastomoses. These steps increase the operation time compared with simpler techniques such as sleeve gastrectomy.

Weight loss is obtained due to restrictive and hypoabsorptive mechanisms [2, 11]. The creation of a gastric pouch restricts the quantity of food that can be ingested whereas the rearrangement of the anatomy by bypassing most of the stomach and the first part of the small intestine limits the absorption of calories and nutrients. The exclusion of these segments also favors a rapid improvement in hyperglycemia and finally T2DM resolution. The fact that these benefits begin to be noticed only days after the procedure without a significant weight loss, implies that the changes in the different glucose regulatory mechanisms, in the release of gastrointestinal tract hormones, and the intestinal microbiota are responsible for this endeavor. The latter mainly consists of anaerobic microorganisms that inhabit the intestinal tract and may have an important role in the pathogenesis of T2DM and obesity. Due to the anatomical modifications with RYGB, unaltered food will directly reach the distal small intestine for digestion and nutrient absorption thus relocating the microbiota which may favor weight loss and metabolic improvement.

**Figure 1.** *Roux-en-Y gastric bypass.*

The main complications associated with RYGB include bleeding, anastomotic ulcer, anastomotic leak or stricture, internal hernia, dumping syndrome, nutritional deficiencies, reactive hypoglycemia, diarrhea, and gallstones [20]. The overall risk of major technical complications is typically <1% when done by a high-volume surgeon at an established center. Given the known malabsorptive consequences, vitamin and mineral supplements should be prescribed after surgery, including multivitamins, calcium, vitamin B12, vitamin D, and iron. Moreover, blood tests should be performed on regular basis to gauge vitamin and mineral levels (**Figure 1**).
