In this procedure a small gastric pouch is created. The jejunium is divided and a Roux-en-Y jejunal limb anastomosis to the small gastric pouch is done. The Roux-en-Y configuration is done to avoid the potential complication of bile reflux gastritis and/or esophagitis associated with loop gastrojejunostomy. The loop gastrojejunostomy has been used in the performance of a gastric bypass known as “mini-gastric bypass”. Long-term outcomes of this procedure remain to be defined. There are three components to a gastric bypass which contribute to its success as a bariatric surgical procedure.

(1) Gastric restriction due to the small gastric pouch and bypass of at least 90 % body of the stomach. This results in diminished ghrelin secretion [15]. (2) Bypass of the duodenum and proximal jejunum. Neuroendocrine phenomena, particularly with regard to stimulation of gastrointestinal peptide (GIP) occurs [16]. (3) Creation of an alimentary limb in which there is no proximal mixing of bile and pancreatic secretions to facilitate digestion. This procedure leads to relocation of the digestion and absorption of the nutrients more distally in the small intestine, presumably responsible for release of neuroendocrine signaling including gastrointestinal glucagon-like peptide 1 (GLP-1) and peptide YY secretion (PYY) [17]. These hormones are known to inhibit food intake. This procedure has proved durable with weight loss of 20–30 % persisting for 10 or more years [17].

Adjustable gastric banding was developed to address what was believed to be a primary limitation of the vertical banding gastroplasty. A small gastric pouch above the band and variable tightness of the band restrict the rate of gastric emptying. Tightening of the band may affect appetite and satiety apart from its role in restricting the amount of nutrients consumed. Weight loss following adjustable gastric banding was initially reported to approach that of gastric bypass, but more recent studies in the United States have indicated that 3 or more years following gastric banding, weight loss is approximately half of that seen with gastric bypass [2].

This procedure as initially described involved a partial gastrectomy with reconstruction of the small intestine to limit exposure of ingested nutrients, pancreatic secretion and bile to a short segment of distal small intestine, thereby creating a degree of malabsorption. In the duodenal switch modification of this procedure a gastric tube is created by resection of approximately 80 % of the stomach and anastomosis distal to the pylorus to the small intestine. Weight loss following this procedure is similar or superior to the weight loss following gastric bypass, as is the effect in ameliorating type in ameliorating type-2 diabetes. An increased rate of early and late complications particularly secondary to malabsorption, however, has limited application of this procedure.

The application of the duodenal switch procedure to a subset of patients with severe obesity (generally BMI > 60) was associated with a problematic perioperative complication rate. As a modification the gastric component of the procedure was done as an initial procedure to be followed by the malabsorptive component in a later time. Careful observation of these patients demonstrated that many achieve satisfactory weight loss as the result of the partial gastrectomy component. As a result, sleeve gastrectomy became an independent procedure intended to be a definitive bariatric surgical procedure. This procedure has achieved considerable popularity, presently second to gastric bypass in application in the United States. Weight loss is generally reported as intermediate between that following gastric bypass and adjustable gastric banding [19, 20]. Long-term weight loss results remain to be determined. The impact on obesity related comorbid conditions also appears intermediate although more closely approximate the response seen following gastric bypass, thus accounting for much of this recent popularity.

A number of procedures have been and continue to be developed to identify procedures which may offer satisfactory weight loss with less risk and/or cost. One such procedure is gastric plication in which a gastric tube similar to that achieved in sleeve gastrectomy is accomplished by imbrication of the greater curvature of the stomach. A number of devices are also under investigation. These include: intragastric balloon, devices to accomplish intermittent vagal blocking, an intraluminal sleeve to extend from the pylorus distally into the jejunum, and other devices which may serve to restrict nutrient intake. All of these investigational procedures in early studies have shown efficacy and acceptable safety. The sustainability of clinical outcomes will require further investigations [21–23].

As with all surgical procedures, complications following bariatric surgery may occur and may be an important consideration. The relative safety of bariatric surgery has been substantially improved in recent years. For example, an expected mortality of 2 % in the past has been reduced to 0.3 % or less at 30 days [24]. The most common complications leading to perioperative mortality are anastomotic leak and secondary abdominal sepsis (procedures involving a gastrointestinal anastomosis), venous thromboembolism, and acute cardiac events (Table 17.1). Factors associated with nonfatal postoperative complications vary with variable definitions. Complications judged to be serious or requiring some type of intervention occurs in approximately 4 % of patients [24]. Several analyses of the predictors of increased perioperative risk have yielded inconsistent results making predictions of perioperative risk and risk adjustment difficult. Factors involved in the improved safety of bariatric surgery include, but are not limited to the application of bariatric surgery to lower risk patients, establishment of care protocols, and increased operative experience for surgeons as well as the establishment of high volume bariatric surgery centers. Such centers may be accredited by a combined program of the American College of Surgeons and the American Society for Metabolic & Bariatric Surgery which is focused on the quality of care [25].

Pories et al. made an important clinical observation that type-2 diabetes appears to go into remission very soon following RYGB, well before weight loss occurs [9]. The short- and long-term response to gastric bypass compared to gastric banding leads to greater weight loss and clinical response to diabetes [11

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