Types of Weight Loss Surgery

Via Merck Manual:

Bariatric surgery is the surgical alteration of the stomach, intestine, or both to cause weight loss.

In the US, bariatric surgery is done over 200,000 times annually, accounting for almost ²/₃ of all bariatric operations done worldwide. Development of safer laparoscopic approaches has made this surgery more popular.

Indications

To qualify for bariatric surgery, patients should

• Have acceptable operative risk
• Be well-informed and motivated
• Have unsuccessfully tried all reasonable nonsurgical methods to lose weight and manage obesity-associated complications
• Have a BMI of > 40 kg/m² or a BMI > 35 kg/m² plus a serious complication (eg, diabetes, hypertension, obstructive sleep apnea, high-risk lipid profile) that could be expected to be meaningfully reduced with a weight loss of 5 to 10%

Contraindications include uncontrolled major depression or psychosis, binge eating disorders, current drug or alcohol abuse, severe coagulopathy, and inability to comply with nutritional requirements, including life-long vitamin replacement (when indicated). Whether bariatric surgery is appropriate for patients < 18 or > 65 yr is controversial.

Procedures

• Restrictive procedures (adjustable gastric banding, vertical banded gastroplasty)
• Malabsorptive procedures (Roux-en-Y gastric bypass)

Most procedures can be done laparoscopically, but the approach depends on the type of procedure as well as patient weight. Morbidity and mortality tend to be lower with laparoscopic than with open surgery. However, if patients weigh ≥ 180 kg, open surgery is more likely to be successful. In about 8% of cases overall (fewer with experienced surgeons), surgery begun laparoscopically must be finished as open surgery.

Procedures can be restrictive, malabsorptive, or both.

Restrictive procedures: Restrictive procedures limit the volume of the stomach available for ingested food. This limited volume helps restrict food intake probably because of earlier satiety. The effects can be partially defeated by patients who consume more high-calorie liquid foods (eg, milk shakes, alcohol), which pass through the restricted portion quicker.

Purely restrictive procedures include adjustable gastric banding and vertical banded gastroplasty.

Adjustable gastric banding accounts for about 15% of bariatric procedures done in the US; it is much more common in Europe and is growing in popularity in the US. It is the 2nd most common bariatric procedure. 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. Saline can be injected into the band via a subcutaneous access port. When saline is injected, the band expands, decreasing the size of the passageway through the stomach. As a result, the upper pouch fills more quickly, sending a message to the brain that the stomach is full; patients eat smaller meals and lose substantial amounts of weight over time. This procedure is usually done laparoscopically. Saline can be removed to make the passageway larger. Even though weight loss from gastric banding is slightly less than that from Roux-en-Y, morbidity and mortality are much less and gastric banding can be reversed if necessary.

Fig. 1
Adjustable gastric banding.

Vertical banded gastroplasty, is no longer commonly done. 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.

Malabsorptive procedures: Malabsorptive procedures, such as biliopancreatic diversion with a duodenal switch and Roux-en-Y gastric bypass, result in ingested food bypassing parts of the stomach and small intestine, creating malabsorption, which leads to weight loss. These procedures are also restrictive.

Roux-en-Y gastric bypass surgery accounts for about 80% of bariatric procedures in the US. It can often be done laparoscopically. A small part of the proximal stomach is detached from the rest, creating a stomach pouch of < 30 mL. Because stomach volume is smaller, satiety occurs earlier. 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 with a narrow opening, producing even more restriction. The segment of bypassed proximal small intestine (and thus the bypassed stomach) is attached to the distal small intestine, enabling bile acids and pancreatic enzymes to mix with GI contents; this mixing limits malabsorption and nutritional deficiencies. Because a gastrojejunostomy is created, symptoms similar to the dumping-syndrome may occur after high glycemic loads; symptoms (light-headedness, diaphoresis, nausea, abdominal pain, diarrhea) may inhibit the consumption of such foods by adverse conditioning.

Fig. 2
Roux-en-Y gastric bypass surgery.

Biliopancreatic diversion with a duodenal switch 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); malabsorption results. This procedure is technically demanding but can sometimes be done laparoscopically. Malabsorption and nutritional deficiencies often develop.

Preoperative evaluation

Evaluation should determine whether patients have a psychologic commitment to the lifestyle changes and whether operative risks are acceptable. Sleep apnea testing is done.

Extensive preoperative evaluation is probably unnecessary. However, for certain morbidly obese patients (BMI > 50 kg/m²), examining the cardiac, pulmonary, GI, metabolic, and psychologic systems helps identify patients with acceptable operative risk and helps select the appropriate procedure. For these patients, routine preoperative tests may include

• Liver function tests: Increased liver enzymes, especially ALT, are common but do not contraindicate surgery.
• Kidney function tests: If renal blood flow and glomerular filtration rate are increased, proteinuria is more likely and renal clearance of drugs may be increased. Thus, drug dosages may need to be adjusted.
• ECG and echocardiography: These tests are needed because identifying heart failure and pulmonary hypertension clinically in morbidly obese patients is difficult. Signs of heart failure (eg, increased jugular venous pressure, hepatomegaly, pulmonary crackles) are hard to identify when body fat is excessive. Pulmonary hypertension is also difficult to identify because many patients cannot exercise to the point where exertional dyspnea, fatigue, or syncope would result. Pulmonary hypertension is diagnosed if echocardiography shows tricuspid regurgitation and ECG shows tall R waves, right axis deviation, and right ventricular strain.
• Sleep study: Polysomnography (see Sleep and Wakefulness Disorders: Testing) can confirm obstructive sleep apnea, which is common, and determine its severity. An apnea-hypopnea index of > 30 signals high risk of morbidity and premature death. Obstructive sleep apnea does not contraindicate surgery but is done to help plan for use of continuous positive airway pressure (CPAP) postoperatively.

Risks

The most common perioperative complication is wound infection (in about 3%); the most common late complication is anastomotic stomach stenosis (in about 5%).

Other early complications include wound infection, incisional hernia, small-bowel obstruction, GI bleeding, ventral hernia, deep venous thrombosis, and pneumonia. These complications can cause significant morbidity, prolong hospitalization, and increase costs.

The most common cause of early (within about 6 wk) postoperative death (in up to 0.5%) is pulmonary embolism, followed by anastomotic leak. Tachycardia may be the only early sign of anastomotic leak. Less common causes of early postoperative death are MI, pneumonia, and bowel obstruction.

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) 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. After Roux-en-Y gastric bypass, iron deficiency may result. Patients may have symptoms of reflux, especially after biliopancreatic diversion with a duodenal switch. After rapid weight loss, cholelithiasis may develop.

Eating habits may be disordered. Adjusting to new eating habits can be difficult.

Prognosis

Overall, 30-day postoperative risk of death is 0.2 to 1%. Risk is higher in elderly patients and in patients who have had an open procedure, who are extremely morbidly obese (> 50 kg) or who have established organ failure. Risk of death may be lowest with laparoscopic adjustable gastric banding. Risk of death is almost 3 times higher in hospitals that do < 50 of these procedures/yr than in those that do >150 procedures/yr. The American Society of Bariatric Surgery may designate hospitals with better results as a Center of Excellence, based on resources and excellent short- and long-term outcomes.

In most patients, comorbidities (eg, insulin insensitivity, dyslipidemias, hypertension, obstructive sleep apnea, polycystic ovary syndrome, nonalcoholic steatohepatitis) tend to resolve.

Average loss of excess weight (real weight minus ideal weight) is about 60%, or about 40 to 60 kg in most patients. Depending on the procedure, excess weight loss can vary between 50% and 70%; loss tends to be lower with gastric banding and somewhat higher with Roux-en-Y gastric bypass. In many patients, weight loss, although initially rapid, plateaus after about 2 yr; then patients may slowly regain weight.

Mood and work and personal relationships usually improve.

Long-term follow-up data are not yet available because these procedures are relatively new.

Follow-up

Patients should be monitored every 4 to 6 wk while weight loss is rapid (usually about the first 6 mo after surgery), then every 6 to 12 mo. 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 each visit. If alkaline phosphatase is increased, parathyroid hormone level is measured; if parathyroid hormone level is abnormal, bone density is monitored. If weight loss exceeds about 9 kg (20 lb)/mo, visits should be scheduled at least monthly, and blood tests should include Mg, phosphorus, vitamin B₁₂, and iron levels. Nutritional supplementation is sometimes necessary.

Last full review/revision October 2008 by Asish C. Sinha, MD, PhD

Content last modified October 2008