In the United States, more than one-third of the population is obese. Currently, bariatric surgery is the best known treatment for obesity, and multiple meta-analyses have shown bariatric surgery to be more effective for treating obesity than diet and exercise or pharmacologic treatment. The modern era of bariatric surgery began in 2005, which is defined by a drastic increase in the use of laparoscopy. Bariatric surgery has the potential to improve obesity-related comorbidities, such as type 2 diabetes, cardiovascular disease, and sleep apnea. The effect of bariatric surgery on weight loss and comorbidities varies by the type of procedure.
Key points
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Bariatric surgery is currently the best known treatment of obesity.
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The sleeve gastrectomy and Roux-en-Y gastric bypass are the two most popular bariatric operations.
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Bariatric surgery has the potential to improve multiple obesity-related comorbidities.
Introduction
Obesity (body mass index [BMI] ≥30 kg/m 2 ) remains a significant problem in the United States, as more than one-third of the American population is obese. Obesity’s burden on the nation’s health care system can be quantified in terms of patient health as well health economics. With respect to the former, obesity is associated with a range of health issues, including diabetes, cancer, and heart disease. Overweight-obesity is responsible for as many as 10% of deaths in America.
At present, bariatric surgery is the best known treatment of obesity, and multiple meta-analyses have shown bariatric surgery to be more effective than diet and exercise or pharmacologic treatment.
Bariatric surgery is marked by large and rapid growth over the last 2 decades. In 1998, 12,775 bariatric operations were performed in the United States. By 2004, that number increased to 135,985. The modern era of bariatric surgery began in 2005, which is defined by a drastic increase in the use of laparoscopy. Although in 2004 less than one-third of bariatric operations were performed laparoscopically, more than 97% of bariatric operations are now laparoscopic procedures.
Three main procedures dominate bariatric surgery: the gastric bypass, sleeve gastrectomy, and gastric band. At their respective peaks, the gastric bypass (in 2003) accounted for 99% of all bariatric surgeries, the gastric band (in 2008) accounted for 29% of all bariatric operations, and the sleeve gastrectomy (in 2012) accounted for 42% of all bariatric operations. Fig. 1 shows trends in the distribution of bariatric procedures over time, from 2004 to 2012.
Patients who undergo bariatric operations are predominantly white and middle aged, and more than 80% are female. These patients have higher rates of obesity-related comorbidities, such as diabetes and hypertension, than the national average. The goal of bariatric surgery is to help patients lose weight and resolve comorbidities associated with obesity. This article reviews the state of bariatric surgery, with a particular emphasis on the relationship between bariatric surgery and gastrointestinal-related comorbidities.
Introduction
Obesity (body mass index [BMI] ≥30 kg/m 2 ) remains a significant problem in the United States, as more than one-third of the American population is obese. Obesity’s burden on the nation’s health care system can be quantified in terms of patient health as well health economics. With respect to the former, obesity is associated with a range of health issues, including diabetes, cancer, and heart disease. Overweight-obesity is responsible for as many as 10% of deaths in America.
At present, bariatric surgery is the best known treatment of obesity, and multiple meta-analyses have shown bariatric surgery to be more effective than diet and exercise or pharmacologic treatment.
Bariatric surgery is marked by large and rapid growth over the last 2 decades. In 1998, 12,775 bariatric operations were performed in the United States. By 2004, that number increased to 135,985. The modern era of bariatric surgery began in 2005, which is defined by a drastic increase in the use of laparoscopy. Although in 2004 less than one-third of bariatric operations were performed laparoscopically, more than 97% of bariatric operations are now laparoscopic procedures.
Three main procedures dominate bariatric surgery: the gastric bypass, sleeve gastrectomy, and gastric band. At their respective peaks, the gastric bypass (in 2003) accounted for 99% of all bariatric surgeries, the gastric band (in 2008) accounted for 29% of all bariatric operations, and the sleeve gastrectomy (in 2012) accounted for 42% of all bariatric operations. Fig. 1 shows trends in the distribution of bariatric procedures over time, from 2004 to 2012.
Patients who undergo bariatric operations are predominantly white and middle aged, and more than 80% are female. These patients have higher rates of obesity-related comorbidities, such as diabetes and hypertension, than the national average. The goal of bariatric surgery is to help patients lose weight and resolve comorbidities associated with obesity. This article reviews the state of bariatric surgery, with a particular emphasis on the relationship between bariatric surgery and gastrointestinal-related comorbidities.
Current options: bariatric surgery
The 4 main bariatric procedures, along with their mechanisms of action, are shown in Fig. 2 .
Gastric Bypass
The Roux-en-Y gastric bypass has been called the gold standard of bariatric surgery. Its effects are restrictive (reduction of stomach capacity), malabsorptive (decreased absorption by the digestive tract), and hormonal (changes in gut hormone levels).
Sleeve Gastrectomy
The sleeve gastrectomy is a common procedure in which the size of the stomach is reduced by approximately 75%, by resecting the greater curvature of the stomach. The sleeve gastrectomy has restrictive and hormonal effects.
Adjustable Gastric Banding
The adjustable gastric band consists of a silicone band attached to an inflatable balloon, which is connected to an access port via a tube. There are currently 2 FDA-approved gastric banding devices: the Lap-Band Gastric Banding System and the Realize Gastric Band. This procedure is purely restrictive.
Biliopancreatic Diversion
Biliopancreatic diversion may be performed as a stand-alone operation, or it may be combined with a duodenal switch in a procedure called the biliopancreatic diversion with duodenal switch. Both procedures are described in detail elsewhere. This procedure is restrictive, malabsorptive, and hormonal. It accounts for only about 2% of bariatric operations.
Eligibility for bariatric surgery
Bariatric surgery is currently recommended for patients with a BMI greater than or equal to 40 kg/m 2 , or a BMI greater than or equal to 35 kg/m 2 with at least 1 serious obesity-related comorbidity, such as heart disease, type II diabetes mellitus (T2DM), or severe sleep apnea. Recently, the American Society of Metabolic and Bariatric Surgery (ASMBS) and the International Federation for the Surgery of Obesity and Metabolic Disorders (IFSO) have emphasized the importance of considering bariatric surgery for patients with BMI greater than or equal to 30 kg/m 2 , provided that they also have serious obesity-related comorbidities. Recent evidence has emerged that supports the use of bariatric surgery in this patient population, and the FDA approved gastric banding for these patients. However, the Centers for Medicare and Medicaid Services do not approve coverage for patients with a BMI less than 35 kg/m 2 .
Weight loss
Current research supports the notion that bariatric surgery is the most effective treatment of obesity. The mechanism of action for bariatric surgery has been described through use of the BRAVE (Bile flow alteration, Reduction of gastric size, Anatomic gut rearrangement and altered flow of nutrients, Vagal manipulation, and Enteric gut hormone modulation) effects. The current theory behind weight loss following bariatric surgery attributes weight loss primarily to physiologic, rather than mechanical, changes. Reduction in levels of ghrelin and leptin, postprandial glucagon-like peptide-1 level increase, and peptide tyrosine tyrosine-response restoration are all credited with playing a major role in weight loss following gastric bypass, as are changes in the intestinal flora and bile acid levels. The sleeve gastrectomy is thought to produce weight loss in similar ways, although the mechanism of action in the sleeve gastrectomy is not as well understood as it is in the gastric bypass.
Gastric Banding
Gastric banding was initially a popular procedure. However, in the long term, many band-related complications have been reported, requiring band removal in almost 50% of patients. Among those patients who have not had the band removed, reports of excess weight loss (EWL) range up to 50%, with follow-up between 5 and 15 years. Compared with laparoscopic sleeve gastrectomy and Roux-en-Y gastric bypass, gastric banding has shown inferior weight loss results and a higher complication rate.
Sleeve Gastrectomy
A systematic review involving 123 studies on the sleeve gastrectomy reported a 59% EWL 1 year after surgery, 64.5% 2 years after surgery, 66% 3 years after surgery, and 60.9% 4 years after surgery. These results are similar to those reported in other systematic reviews.
Roux-en-Y Gastric Bypass
Gastric bypass is traditionally considered the gold standard of bariatric surgery. A recent analysis of the long-term results of Roux-en-Y gastric bypass reported 57% EWL at 10 years of follow-up. In a matched cohort study, gastric bypass showed superior EWL (67%) to both sleeve gastrectomy (56%) and gastric banding (44%). This finding has been repeated elsewhere; for example, one study reported an EWL of 76% for the gastric bypass, 53% for sleeve gastrectomy, and 30% for the gastric band.
Roux-en-Y Gastric Bypass Versus Sleeve Gastrectomy
One of the highest priority questions currently facing bariatric surgeons is whether or not the sleeve gastrectomy can replace the Roux-en-Y gastric bypass as the gold standard surgical procedure. The proven long-term success of the gastric bypass must be weighed against the technical complexity of the procedure and the associated risk for complications. One recent meta-analysis synthesized data from 62 studies comparing the Roux-en-Y gastric bypass with the sleeve gastrectomy (including several randomized controlled trials), resulting in data from 18,455 patients. After fitting a random-effects model, this study found that Roux-en-Y gastric bypass patients had a significantly higher percentage EWL (%EWL) than did sleeve gastrectomy patients, with a weighted mean difference of 7.24%. Similarly, a separate meta-analysis found that gastric bypass patients had a higher 2-year postoperative %EWL following surgery as well as a lower 2-year postoperative BMI than did sleeve gastrectomy patients.
Survival/mortality
The in-hospital mortality of bariatric surgery is low. One recent study puts the number between 0.07% and 0.10%, while another review cites the range of mortality as 0.1% to 2.0%. A meta-analysis that included nearly 200,000 patients showed that patients who underwent bariatric surgery had greater than a 50% reduction in mortality relative to control patients who did not undergo surgery. One study found that bariatric surgery patients gained an extra 6.5 years of life expectancy relative to a severely obese patient who did not undergo surgery.
Outcomes: gastrointestinal related
Gallbladder Disease
The relationship between bariatric surgery and gallbladder disease is complex, confounded significantly by the practice of prophylactic cholecystectomy (the routine removal of the gallbladder during bariatric surgery). Rapid weight loss is a risk factor for cholelithiasis, and approximately 35% to 38% of patients develop gallstones after bariatric surgery. Some reports show that up to 40% of these patients become symptomatic, which is often cited as a reason for prophylactic cholecystectomy. However, others claim that only 7% to 15% of patients who develop gallstones after bariatric surgery become symptomatic. Thus the practice of prophylactic cholecystectomy during gastric bypass is controversial. A recent Swedish study analyzing 13,443 patients suggested that the increased need for cholecystectomy following gastric bypass may be caused in part by increased detection caused by the bariatric operation itself, and concluded that prophylactic cholecystectomy may not be recommended.
The American Society for Metabolic and Bariatric Surgery has recently recommended that normal and asymptomatic gallbladders not be removed at the time of surgery unless clinically indicated.
Nonalcoholic Fatty Liver Disease
Nonalcoholic fatty liver disease is one way that metabolic syndrome presents in the liver. It has an incidence of up to 70% in the obese, and bariatric surgery significantly reduces histologic features (eg, steatosis and fibrosis) and enzyme levels associated with nonalcoholic fatty liver disease.
Obesity and Gastroesophageal Reflux Disease
Gastroesophageal reflux disease (GERD) is a disease of the upper digestive tract that can significantly affect the quality of life of affected patients. In the general Western population, the incidence of GERD is approximately 10% to 20%. This number increases significantly in the obese population (between 37% and 72% of obese patients have GERD), and some clinicians have suggested a causal link between obesity and GERD. The impact that bariatric surgery has on GERD depends markedly on the procedure performed.
Roux-en-Y gastric bypass is superior to other procedures in improving GERD symptoms. Approximately 56.5% of patients with GERD reported improvement in their symptoms following gastric bypass. It is thought that gastric bypass improves GERD symptoms because of weight loss, the diversion of bile from the Roux limb, and reduced acid production (the small pouch created in the procedure lacks parietal cells).
Several studies find that there is an increase in the prevalence of GERD symptoms following sleeve gastrectomy, including a recent systematic review and meta-analysis. It has been proposed that this occurs because of any or all of the follow mechanisms: a decline in lower esophageal sphincter pressure, the disruption of the angle of His, the decline in gastric compliance, and high intragastric pressure. A significant number of studies have reported new-onset GERD following sleeve gastrectomy (ie, patients who did not have GERD before surgery develop it after surgery). One proposed mechanism of action for this is that hiatal hernias develop following surgery and then the sleeve migrates above the level of the hiatus.
The association of GERD with gastric banding is controversial. Multiple studies show an improvement in symptoms and decrease in medications related to GERD following banding. A systematic review showed a decrease in reflux symptoms postoperatively, from 32.9% to 7.7%, as well as a decrease in medication usage, from 27.5% to 9.5%. Other studies show an increase in GERD symptoms following gastric banding, and propose that the increase results from either esophageal dysmotility or esophageal outflow obstruction caused by increased pressure following band placement.
If there is an onset or worsening of GERD after bariatric surgery, symptoms are treated initially with acid-reducing medications and promotility agents (as they would be in the general population). If medical therapy fails, then revisional surgery is considered. In the cases of gastric banding or sleeve gastrectomy, conversion to gastric bypass has successfully reduced GERD symptoms. In the case of gastric bypass, revisions include lengthening the Roux limb or downsizing the pouch that was created during the initial surgery.
Bariatric Surgery and Inflammatory Bowel Disease
Inflammatory bowel disease (IBD) is a term that refers collectively to 3 conditions: Crohn’s disease, ulcerative colitis, and indeterminate colitis. Although IBD is not traditionally associated with obesity, current research suggests that obesity may play a role in inducing IBD and recent reports have shown that the prevalence of obesity among patients with IBD is increasing.
Several technical considerations come into play when considering gut surgery on patients with IBD. Many surgeons do not to perform bariatric surgery on patients with IBD. Data are therefore scarce on the effects of bariatric surgery on IBD. However, one small study suggested that sleeve gastrectomy and gastric banding are safe in patients with IBD, and saw no exacerbation or only mild exacerbation of IBD symptoms following surgery. Another study of 20 patients who underwent bariatric surgery reported that bariatric surgery is safe and effective in this patient population, and further that 90% of patients who were on pharmacotherapy to control their IBD-related symptoms experienced significant improvement in their symptoms and a major reduction in the maintenance medical therapy following surgery.
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