Bariatric surgery is the surgical alteration of the stomach, intestine, or both to cause weight loss.
In the US, about 220,000 bariatric operations were done in 2009. Development of safer laparoscopic approaches has made this surgery more popular.
To qualify for bariatric surgery, patients should
Although studies have shown that surgery causes remission of diabetes in patients with a BMI of 30 to 35, long-term data are limited, and the use of bariatric surgery is controversial in patients with a lower BMI.
The most common procedures done in the US include
Most procedures are done laparoscopically, resulting in less pain and a shorter healing time than open surgery. Traditionally, bariatric surgery has been classified as restrictive and/or malabsorptive, referring to the presumptive mechanism of weight loss. However, other factors appear to contribute to weight loss; for example, RYGB (traditionally classified as malabsorptive) and SG (traditionally classified as restrictive) both result in metabolic or hormonal changes that favor satiety and weight loss and in other hormonal changes (eg, an increase in insulin release [incretin effect]) that appear to contribute to the rapid remission of diabetes. After RYGB (particularly) or SG, levels of GI hormones, such as glucagon-like peptide-1 (GLP-1) and peptide YY (PYY), are increased, possibly contributing to satiety, weight loss, and remission of diabetes. Increased insulin sensitivity is evident immediately postoperatively, before significant weight loss occurs, suggesting that neurohormonal factors are prominent in remission of diabetes.
Roux-en-Y gastric bypass surgery
RYGB accounts for about 80% of bariatric procedures in the US and is usually done laparoscopically. A small part of the proximal stomach is detached from the rest, creating a stomach pouch of < 30 mL. Also, food bypasses part of the stomach and small intestine, where it is normally absorbed, reducing the amount of food and calories absorbed. The pouch is connected to the proximal jejunum; the opening between them is narrow, limiting the rate of gastric emptying. The segment of small intestine connected to the bypassed stomach is attached to the distal small intestine. This arrangement allows bile acids and pancreatic enzymes to mix with GI contents, limiting malabsorption and nutritional deficiencies.
RYGB is particularly effective in treating diabetes; remission rates are up to 62% after 6 yr.
For many patients who have had RYGB, eating high-fat and high-sugar foods can cause dumping syndrome; symptoms can include light-headedness, diaphoresis, nausea, abdominal pain, and diarrhea. Dumping syndrome may inhibit the consumption of such foods by adverse conditioning.
Traditionally, SG has been done only when patients are considered too high risk for procedures such as RYGB and biliopancreatic diversion (eg, patients with a BMI > 60), typically before one of these procedures or another similar procedure is done. However, because SG causes substantial and sustained weight loss, it is being used increasingly in the US as definitive treatment for severe obesity. Part of the stomach is removed, creating a tubular stomach passage. The procedure does not involve anatomic changes to the small intestine.
Mean excess weight loss tends to be higher than with that with AGB. Although traditionally classified as a restrictive procedure, weight loss is probably also related to neurohormonal changes. The most serious complication is gastric leak at the suture line; it accounts for 1 to 3% of complications.
Biliopancreatic diversion with a duodenal switch
This procedure accounts for < 5% of bariatric procedures done in the US. Part of the stomach is removed, causing restriction. The remaining part empties into the duodenum. The duodenum is cut and attached to the ileum, bypassing much of the small intestine, including the sphincter of Oddi (where bile acids and pancreatic enzymes enter); as a result, food absorption decreases. This procedure is technically demanding but can sometimes be done laparoscopically. Malabsorption and nutritional deficiencies often develop.
Adjustable gastric banding
AGB is the 2nd most common bariatric procedure done in the US. A band is placed around the upper part of the stomach to divide the stomach into a small upper pouch and a larger lower pouch. Typically, the band is adjusted 4 to 6 times by injecting saline into the band via a port that is placed subcutaneously. When saline is injected, the band expands, restricting the upper pouch of the stomach. As a result, the pouch can hold much less food, patients eat more slowly, and satiety occurs earlier. This procedure is usually done laparoscopically. Saline can be removed from the band if a complication occurs or if the band is overly restrictive.
Weight loss with the band varies and is related to the frequency of follow-up; more frequent follow-ups result in greater weight loss. Although postoperative morbidity and mortality are less than those with RYGB, long-term complications, including repeat operations, are more likely, possibly occurring in up to 15% of patients.
Vertical banded gastroplasty
This procedure is no longer commonly done because complication rates are high and the resulting weight loss is insufficient. For this procedure, a stapler is used to divide the stomach into a small upper pouch and a larger lower pouch. A nonexpandable plastic band is placed around the opening where the upper pouch empties into the lower pouch.
Preoperative evaluation consists of diagnosing and correcting comorbid conditions as much as possible, assessing readiness and ability to engage in lifestyle modification, and excluding contraindications to surgery. All patients should be evaluated by a dietician to review the postoperative diet and to assess their ability to make necessary lifestyle changes. All patients should also be evaluated by a psychologist or other qualified mental health care practitioner to identify any uncontrolled psychiatric disorder and any dependencies that would preclude surgery and to identify and discuss potential obstacles to adherence to lifestyle changes postoperatively.
Extensive preoperative evaluation is not routinely necessary, but preoperative testing may be necessary based on clinical findings, and measures to control certain conditions (eg, hypertension) or reduce risk may be taken.
Perioperative risks are lowest when bariatric surgery is done in an accredited center.
Complications include gastric and/or anastomotic leaks (in 1 to 3%), pulmonary complications (eg, ventilator dependence, pneumonia, pulmonary embolism), MI, wound infection, incisional hernia, small-bowel obstruction, GI bleeding, ventral hernia, and deep venous thrombosis. These complications can cause significant morbidity, prolong hospitalization, and increase costs. Tachycardia may be the only early sign of anastomotic leak.
Later problems may include prolonged nausea and vomiting secondary to small-bowel obstruction and anastomotic stenosis. Nutritional deficiencies (eg, protein-energy undernutrition, vitamin B12 deficiency, iron deficiency) may result from inadequate intake, inadequate supplementation, or malabsorption. Malodorous flatulence, diarrhea, or both may develop, particularly after malabsorptive procedures. Ca and vitamin D absorption may be impaired, causing deficiencies and sometimes hypocalcemia and secondary hyperparathyroidism. With prolonged vomiting, thiamin deficiency may occur. Patients may have symptoms of reflux, especially after SG. During rapid weight loss, cholelithiasis (often symptomatic), gout, and nephrolithiasis may develop.
Eating habits may be disordered. Adjusting to new eating habits can be difficult.
Overall 30-day mortality in hospitals accredited by the American Society of Bariatric Surgery as centers of excellence is 0.2 to 0.3%. Mortality is higher with RYGB than laparoscopic AGB and higher with open procedures (2.1%) than laparoscopic procedures (0.2%). Factors that predict higher risk of mortality include a history of deep venous thrombosis or pulmonary embolism, obstructive sleep apnea, and poor functional status. Other factors such as severe obesity (BMI > 50), older age, and male sex have also been associated with higher risk but the evidence is inconsistent.
Average excess weight loss depends on the procedure.
For laparoscopic AGB, weight loss is 45 to 72% at 3 to 6 yr and 14 to 60% at 7 to 10 yr. Percentage of weight loss is related to the frequency of follow-ups and number of band adjustments. Patients with a lower BMI tend to lose more weight than those with a higher BMI.
For SG, weight loss is 33 to 58% at 2 yr and 58 to 72% at 3 to 6 yr; longer-term data are not available.
For RYGB, weight loss is 50 to 65%.
Comorbid conditions that tend to abate or resolve after bariatric surgery include cardiovascular risk factors (eg, dyslipidemia, hypertension, diabetes), cardiovascular disorders, diabetes, obstructive sleep apnea, osteoarthritis, and depression. Diabetes is particularly likely to remit (eg, with RYGB, up to 62% of patients at 6 yr). All-cause mortality decreases by 25%, primarily because cardiovascular and cancer mortality is reduced.
Regular, long-term follow-up helps ensure adequate weight loss and prevent complications. After RYGB or SG, patients should be monitored every 4 to 12 wk during the period of rapid weight loss (usually about the first 6 mo after surgery), then every 6 to 12 mo thereafter. With laparoscopic AGB, results appear to be optimal when patients are monitored and the band is adjusted at least 6 times during the first year after surgery.
Weight and BP are checked, and eating habits are reviewed. Blood tests (usually CBC, electrolytes, glucose, BUN, creatinine, albumin, and protein and liver function tests) are done at regular intervals. Glycosylated Hb (HbA1c) and fasting lipid levels should be monitored if they were abnormal before surgery. Depending on the type of procedure, vitamin and mineral levels, including Ca, vitamin D, vitamin B12, folate, and iron, may need to be monitored. Because secondary hyperparathyroidism is a risk, parathyroid hormone levels should also be monitored. Bone density should be measured after SG and RYGB. Clinicians should check for any changes in response to antihypertensives, insulin, oral hypoglycemics, or lipid-lowering drugs during the period of rapid weight loss after surgery. Patients should be regularly evaluated for gout, cholelithiasis, and nephrolithiasis, all of which can develop after bariatric surgery. Prophylactic ursodiol reduces risk of cholelithiasis and should be offered after bariatric surgery.
To minimize risk of hypoglycemia (due to increased insulin sensitivity after bariatric surgery) in patients with diabetes, clinicians should adjust the dose of insulin and decrease the dose of oral hypoglycemics (particularly sulfonylureas) or stop them after RYGB and SG.
Last full review/revision March 2013 by Ashish C. Sinha