Among the especially powerful accomplishments of RYGB has been its ability to produce rapid remission of type 2 diabetes in severely obese patients with that disease [8]. The remission rate is as high as 80 % or more for patients with disease of 5 years’ duration or less. This is a huge consideration for the patient who has begun insulin therapy. The remission of type 2 diabetes after gastric bypass has become the focus of much of the shift from considering RYGB more as a metabolic than a bariatric operation [9]. There is an entire chapter devoted to this topic in this text, and the reader is referred to it for the details of this particular metabolic action of RYGB. It should also be noted that there are also now good data to support extending the indications for performing RYGB for patients with type 2 diabetes who have a BMI between 30 and 35 [10].

Improvement in vital organ function and improvement in obesity-related organ dysfunction is also well documented after RYGB. Patients with nonalcoholic fatty liver disease (NAFLD) have been shown to benefit from RYGB. Postoperatively, based on biopsy analysis, RYGB produced a 93 % incidence of improvement in liver score and at times reversed fibrosis (20 %) and inflammation (37 %) [11].

Cardiovascular disease has also been shown to be improved after gastric bypass. Observations of the improvement in hypertension have been made since the operation has been monitored, and improvement in measured cardiac function has been more recently emphasized in the literature [12]. Cardiac function has been shown to be reversibly improved in adolescents with left ventricular hypertrophy and dilatation after undergoing LRYGB [13].

Pulmonary function has been documented to improve as well after RYGB. Hewitt et al. [14] showed long-term improvement in pulmonary function as measured by spirometry in 101 patients who had undergone RYGB. Nguyen et al. [15] showed similar findings in a similar sized group of patients as well, documenting the changes were evident as quickly as 3 months after surgery.

OSA is almost certainly underdiagnosed in the morbidly obese patient population. Hallowell et al. [16] showed that when routine testing was done for OSA preoperatively, a significant percentage of patients had undiagnosed disease. The incidence of patients felt to have OSA by clinical criteria versus routine testing rose from 56 to 91 %. This high percentage of undiagnosed patients may thus mitigate the already impressive incidence of improvement or resolution of OSA in the many studies after RYGB. Marti-Valeri et al. [17] reported that 86 % of patients no longer needed CPAP 1 year after RYGB. Patients with severe OSA may not be able to wean completely off their CPAP but often have their disease state ameliorated to moderate disease. They also may appear clinically less symptomatic than they prove to be with strict testing [18]. In large database reviews, OSA was seen to be improved in 66 % of patients after RYGB in the BSCN database [19]. The NSQIP data show a 70 % improvement nationally in OSA for patients undergoing LRYGB [20].

Degenerative joint disease is perhaps the most frequent comorbid medical problem found in patients who are candidates for bariatric surgery. However, its resolution or improvement is much more difficult to quantify as it is very much symptom based without objective parameters of measurement. Certainly, however, all bariatric surgeons are witnesses to frequent testimonies by patients of marked improvement in their joint and back pain. Improved mobility is enjoyed by many of the patients and often conversions from wheelchair-bound to ambulatory status are not infrequently seen in this patient population after RYGB.

Gastroesophageal reflux disease (GERD) is symptomatically present in mild degrees in approximately one half of patients with severe obesity and has been objectively proven to be present in 55 % in one study [21]. In another study in which anatomic and physiologic assessments were done of patients planning RYGB, the incidence of GERD was 64 % [22]. In that study, the incidence of postoperative GERD decreased to 33 % and median acid exposure of the esophagus from 5.1 to 1.1 %. The improvement postoperatively was somewhat decreased by a persistent and new onset of regurgitation in some patients. RYGB offers an anatomic advantage to treating this disease, in that the large-volume stomach is no longer connected to the esophagus. Instead, the very-small-volume proximal gastric pouch can be the only source of acid reflux. As a result, the incidence of resolution or improvement of GERD after RYGB is quite high. This has actually made RYGB the treatment of choice for patients with severe GERD and a BMI over 40. Resolution of symptoms in that patient population postoperatively is high and moreover is higher in the long term than patients treated with antireflux surgery, who due to their obesity and its associated increase in intra-abdominal pressure develop recurrence of symptoms and hiatal hernia more frequently than normal-weight individuals.

Venous stasis ulcers were shown by Sugerman et al. [23] to be effectively treated with RYGB in over 90 % of cases. These patients, however, were noted to have higher risk factors, more severe comorbidities, and higher death and complication rates than the general population of patients undergoing RYGB.

Pseudotumor cerebri is present in perhaps 1 % of patients with morbid obesity. However, when present, it is especially well treated with bariatric surgery. Reports of its almost 100 % resolution of RYGB have been documented in the literature [24]. The key to its treatment is appreciation by a neurologist or neurosurgeon of the value of weight loss in eliminating the condition.

Pseudotumor cerebri as well as stress urinary incontinence, another condition which responds well to weight loss therapy, represent diseases among the spectrum of comorbid medical problems which have been hypothesized by Sugerman to arise from increased abdominal pressure [25]. The fact that there is an inflammatory component to many of these comorbid problems, as a result of the pressure, further supports this hypothesis. Metabolic studies have now shown inflammatory components to the cardiovascular, glucose intolerance, renal dysfunction, and hyperlipidemia dysfunction present in the severely obese patient population. The metabolic syndrome is characterized by a constellation of medical conditions, all of which are felt to include an inflammatory component in their etiology. The metabolic syndrome is well treated by RYGB, with resolution in 45 % of patients reported in one large series of diverse backgrounds [26].

In one recent study, LRYGB was shown to decrease the measured amount of urinary and serum inflammatory markers, as well as mean arterial pressure. It is hypothesized by the authors that the improvements seen in renal function, proteinuria, and hypertension after RYGB are related to weight loss-induced decrease in these inflammatory factors [27].

Overall quality of life has been measured in numerous reports of patients undergoing open and LRYGB. Schauer et al. [28] showed an improved quality of life for patients undergoing LRYGB, and Nguyen et al. [29] showed that SF-36 and BAROS score improvement was even greater than the improvement seen after open RYGB.

Open gastric bypass has traditionally provided patients with weight loss in the range of 60–70 % of excess weight at 1 year after surgery. Studies looking at outcomes from the era of open surgery reported this figure to be in the 60–65 % range [7]. Longer-term follow-up data show that some patients regain weight. However, the recidivism of weight regain tends to decrease after 10 years, and studies have shown that RYGB and other procedures produce long-term durable weight loss [5, 8].

Mortality after open RYGB was traditionally reported as between 1 and 2 % in the literature [30, 31]. A combination of many factors has now caused that number to have dropped to one-tenth its value in current practice.

Complications after open RYGB were also reported as being higher than they are today. The differences, however, could be variable depending on whether a study included long-term complications such as incisional hernia, bowel obstruction, and marginal ulcer, to name a few common ones. The transition from open surgery to laparoscopic surgery drastically reduced the serious wound complications and virtually eliminated the problem of incisional hernia after RYGB. The latter, in our institutional experience, was approximately 33 % if patients were followed carefully for a decade. Table 2 shows data from the University of Virginia comparing the first 5 years of our laparoscopic experience with performing gastric bypass versus the previous 15 years’ experience with open surgery. Notable is the decrease in postoperative wound and incisional hernia complications, which consequently results in a huge difference in the overall complication rates of RYGB versus LRYGB. The second important observation is that patients who underwent open RYGB were generally heavier and had more comorbid medical problems than those undergoing LRYGB. This phenomenon likely has, to some extent, contributed to the decrease in incidence of morbidity and mortality after gastric bypass as well as other bariatric and metabolic operations.

Institutions besides our own reported an open RYGB complication rate in the 15–25 % range, depending on how such complications were defined and classified. Recent databases on LRYGB give the complication rates as being between 11.79 % for the BOLD database [32] and 15 % for the NSQIP database for cases done from 2007 to 2010 [19]. Current NSQIP 30-day complication rates for gastric bypass are as low as 4.7 % for 21,557 entered cases [20].