The origins of the gastric bypass operation date back to the 1960s and the contributions of Dr. Mason. While searching for a weight loss operation without the detrimental side effects often seen with the jejuno-ileal bypass, he noted that patients with peptic ulcer disease who had undergone a partial gastrectomy with Billroth II gastrojejunostomy subsequently experienced weight loss and had difficulty regaining that lost weight. Based on these findings, Mason described the original gastric bypass in 1967 using a technique that divided the stomach and anastomosed a jejunal loop to the proximal gastric pouch [7, 8]. His original description emphasized a small pouch as well as a small diameter anastomosis to delay gastric emptying and enhance satiety [8]. Over the ensuing several decades, there have been a variety of technical modifications, including attempted calibration and standardization of gastric pouch size [9] and the replacement of the loop gastrojejunostomy with a Roux-en-Y configuration [10]. In 1995, Wittgrove reported the first laparoscopic RNYGB [11]. Since this time, data from the Nationwide Inpatient Sample from 2003 through 2008 have documented an increase of laparoscopic bariatric operations from 20 % in 2003 to 90 % in 2008 [12]. Minimally invasive techniques now account for the vast majority of bariatric procedures performed today and should be considered the standard of care in primary procedures.

Despite the evolution and almost universal adoption to a laparoscopic technique, there still remain significant technical variations in the way a RNYGBP can be performed. Owing to its complexity and the need for a high degree of laparoscopic technical skills, the relative risk of complications has been reported to diminish following a 500-procedure learning curve [13]. The number of surgeries performed, or experience of the operating surgeon, and the standardization of the laparoscopic technique have been cited as main factors contributing to improved rates of postoperative complications, mortality, and decrease in conversion to open rates [13]. The currently adopted surgical principles, as described by Pories et al. include the exclusion of a majority of the stomach (~ 90 %) except for a 15–30-ml pouch created around the gastroesophageal junction, and transection of the jejunum 30–60 cm from the ligament of Treitz [14]. The distal jejunal segment (Roux limb) is then anastomosed to the gastric pouch and the proximal jejunal segment (biliopancreatic limb) connected distally as a jejunojejunostomy approximately 75–150 cm from the ligament of Treitz, providing secretory drainage of the bypassed stomach, duodenum, and proximal jejunum (common channel limb). The Roux limb, or alimentary limb, carries ingested food and is delineated between the gastrojejunostomy and the jejunojejunostomy. The Roux limb, the excluded or remnant stomach, duodenum, and proximal jejunum represent the bypassed section of the RNYGB [3, 14]. Variations in operative techniques other than gastric pouch size and Roux limb length have included various positionings of the Roux limb and gastrojejunal anastomosis in relation to other body structures. Combinations have included antecolic (above colon) versus retrocolic (behind colon) placement of the Roux limb and antegastric (above stomach) versus retrogastric (behind stomach) creation of the gastrojejunostomy. Techniques for construction of the gastrojejunostomy have included: one layer versus two-layered anastomosis, stapled versus hand-sewn anastomosis or combinations of techniques. Other major variations include routine versus selective closure of mesenteric defects [15, 16].

Multiple studies have demonstrated that among morbidly obese patients, compared with nonsurgical control patients, the use of RNYGB has been associated with higher rates of diabetes remission and lower risk of cardiovascular and other negative health outcomes over long-term follow up [17–20]. In contrast, the cardiovascular and metabolic status of obese control participants generally worsens over time, despite aggressive medical management. When comparing RNYGB with lifestyle and intensive medical management, achievement of primary end points including hemoglobin A1C level, low-density lipoprotein cholesterol levels, systolic blood pressure, and the number of medications needed to manage these comorbidities, the literature has consistently supported gastric bypass, although at the potential expense of increased nutritional deficiencies and potential surgical complications [21].

Several studies have evaluated the degree of weight loss following gastric bypass, and the durability of the lost weight . A meta-analytic review of the recent published surgical experience found an excess weight loss of 68.2 % (61.5–74.8 %) for RNYGB [22]. A randomized series reported by Nguyen et al. examined 111 laparoscopic RNYGB during a 4-year follow-up period. The authors reported 68.4 % excess weight loss (EWL) for RNYGB with a mean body mass index (BMI) decrease of 15 kg/m² [23]. In a smaller series, Spivak et. al. reported an EWL of 58.6 % at 7 years follow-up [24]. However, after an initial 4 years of progressive weight loss,the authors reported that most patients experience a certain weight regain during a long-term follow-up period [24]. The prospective, controlled Swedish Obese Subjects study reported a 7 % mean weight regain among patients after gastric bypass surgery from 2 years to 10 years [20]. A more recent study described similar results, with a weight regain of approximately 7 % at 2 years following gastric bypass surgery [17]. Overall, it has been found that for the majority the weight loss is durable and weight regain is modest. It is unclear, at present, if the weight regain represents the normal weight trajectory of the patient’s weight over time or a consequence of physiological or behavioral adaptations to the surgical changes performed .

Insulin resistance constitutes a central pathophysiology of type II diabetes mellitus (DM) in the obese. Long-standing remission of DM has been reported to occur in up to 83 % of individuals undergoing RNYGB [3, 18, 25, 26]. In the Surgical Treatment and Medications Potentially Eradicate Diabetes Efficiently (STAMPEDE) trial, intensive medical therapy was compared to surgical treatment (gastric bypass or sleeve gastrectomy) as a means of improving glycemic control. The proportion of patients with the primary end point was 12 % in the medical-therapy group versus 42 % in the gastric bypass group (P = 0.002) [27]. The mechanisms by which gastric bypass results in prolonged improvement in glycemic control have been the subject of a great deal of scientific study. Weight loss, reduced oral intake, altered enteric hormonal secretion (glucagon-like peptide-1, glucose-dependent insulinotropic peptide, ghrelin), and changes to the gastrointestinal tract microflora, all having been proposed as playing a part in this phenomenon [28–34]. Caloric restriction in obese patients without surgery improves insulin sensitivity and glucose homeostasis significantly before any evidence of weight loss is seen [35]. Similarly, all types of bariatric surgery include an element of caloric restriction, which may be the common cause for the associated improvements in insulin sensitivity independent of anatomic changes [3, 36]. However, the immediate effects in glycemic control often precede substantial weight loss typically associated with insulin sensitivity [3]. These observations are consistent with findings by Schauer et al. where reductions in the use of diabetes medications occurred before the achievement of maximal weight loss, suggesting that caloric restriction alone is unable to explain the complex effects RNYGB has on DM [21, 27, 37–39].

Despite the expectation that DM may undergo remission, or at least improve following RNYGB, there is a relative paucity of data attempting to identify patient-specific predictive factors. Hayes et al. used 13 preoperative parameters and a variety of statistical techniques to create mathematical models able to correctly identify which patients would experience remission of DM at 12 months follow-up in 82.7–87.4 % of cases[40]. The two strongest predictors of DM resolution were low HbA1c and the nature and level of preoperative DM control [25, 40, 41]. Other predictive factors that have been proposed for long-term DM remission have included gender (males more likely than women), younger age, and percentage of postoperative EWL [42, 43].

Hyperlipidemia plays a major role in the excess morbidity and premature mortality of the morbidly obese. Improvements in coronary risk factors, including hyperlipidemia, after gastric bypass have been predicted to lower the 10-year risk of ischemic heart disease events by approximately 50 % [44]. Nguyen et al. showed a significant positive effect on atherogenic lipids with improvement of favorable lipoprotein levels after RNYGB that were sustained for the duration of the study [45]. Improvement in lipid profiles was observed as early as 3 months postoperatively and sustained at 2 years follow-up. One year after gastric bypass, mean total cholesterol levels decreased by 16 %; triglyceride levels decreased by 63 %; low-density lipoprotein cholesterol levels decreased by 31 %; very-low-density lipoprotein cholesterol decreased by 74 %; total cholesterol/high-density lipoprotein cholesterol risk ratio decreased by 60 %, and high-density lipoprotein cholesterol levels increased by 39 %. Also, within 1 year, 82 % of patients requiring lipid-lowering medications preoperatively were able to discontinue their medications [45].

A large meta-analysis of over 29,000 patients reported mortality of gastric bypass to be 0.5 %.(4) The obesity surgery mortality risk score (OS-MRS) developed by a single institution experience of 2075 patients and subsequently validated used a 90-day all-cause death rate, not just hospitalization, and confirmed a high-risk predictive score [46, 47]. The OS-MRS assigns 1 point to each of 5 preoperative variables , including body mass index > = 50 kg/m2, male gender, hypertension, known risk factors for pulmonary embolism (previous thromboembolism, preoperative vena cava filter, hypoventilation, pulmonary hypertension), and age > = 45 years [48, 49]. Overall mortality for the validation cohort was 0.7 %, consistent with published standards, and represents an average mortality risk among all patient subgroups. Although the highest-risk group class based on the OS-MRS score experienced a 12-fold increase in mortality compared with the lowest-risk group patients, the authors emphasized that the increased risk should not preclude consideration for surgical treatment, as these high-risk patients represent those with a high-risk of early death from their associated comorbidities of obesity.