Blueprints Surgery, 5th Edition

Part II - Gastrointestinal and Abdominal

Chapter 10

Bariatric Surgery

Bariatric surgery, or weight loss surgery, limits the amount of food the stomach can hold by reducing the stomach's capacity to a few ounces. In addition to reducing food intake, some weight loss surgeries also alter the digestive process, which curbs the amount of calories and nutrients absorbed.

ANATOMY

The relevant anatomy involves the stomach and proximal small bowel. These are well-vascularized organs, and although they can withstand significant transections and bypass, it remains critical not to compromise the blood supply. See Chapter 3, Stomach and Duodenum, and Chapter 4, Small Intestine.

MORBID OBESITY

EPIDEMIOLOGY

The increased risk for morbidity and mortality is proportional to the degree of a person's excess weight. The most common way to quantify obesity is by the body mass index (BMI), which is calculated as [weight (kilograms)/height (meters)²]. The BMI associated with lowest mortality is between 20 and 25 kg/m². An adult with a BMI >25 kg/m² is considered overweight; an adult with BMI >30 kg/m² is considered obese. Morbid obesity, approximately equivalent to a person being 100 pounds overweight, can be a life-threatening condition. A person is classified as being morbidly obese if he or she has a BMI ≥40 kg/m², or a BMI of ≥35 kg/m² with an obesity-related disease, such as type 2 diabetes, heart disease, or sleep apnea. Approximately 100 million Americans are obese, and 15 million are morbidly obese. Obesity is rapidly becoming an epidemic in the United States, with prevalence rates of 15% in 1980, and increasing to 33% in 2004. Obesity costs the U.S. healthcare system an estimated $117 billion annually, according to the National Institute of Diabetes and Digestive and Kidney Diseases. After tobacco, obesity is the second leading cause of preventable death in the United States.

PATHOPHYSIOLOGY

The ultimate biologic basis of obesity is unknown. A sedentary lifestyle and the availability of high-caloric foods certainly contribute to this disease process. This disorder, nevertheless, is accompanied by a reduction in life expectancy, which is due in large part to the complications associated with diabetes, hypertension, and sleep apnea.

HISTORY

The approach to the morbidly obese patient has to take into account the weight history, dietary habits, lifestyle, exercise tolerance, and medical comorbidities of the individual. Previous attempts at nonsurgical weight loss should be documented. The dietary and weight history should focus on identifying eating disorders, as well as any emotional or psychiatric conditions that may be linked. Counseling a patient to engage in an active exercise regimen is also critical.

The medical history should aim at ruling out any metabolic causes of obesity, such as hypothyroidism and Cushing's syndrome. Obesity is also related to a host of medical comorbidities that should be identified and

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stabilized preoperatively. These are listed in Table 10-1. As with any other major operation, surgical risk should be individually assessed on the basis of the medical history.

PHYSICAL EXAMINATION

A general physical examination should be performed preoperatively. Specific to the bariatric population, the airway should be evaluated for difficulty of intubation as well as risk for obstructive sleep apnea. The abdomen should be assessed for the degree of central obesity, as well as prior surgical incisions, which may make laparoscopic surgical approaches difficult.

DIAGNOSTIC EVALUATION

Patients are considered suitable candidates for bariatric surgery if they meet criteria set by the 1991 National Institutes of Health consensus conference on bariatric surgery. Patients must:

• Have a BMI >40, or a BMI >35 with significant weight-related comorbidities, such as diabetes, hypertension, or sleep apnea.
• Have no metabolic abnormalities that could cause weight gain.
• Have attempted and failed at nonsurgical weight loss.
• Be psychologically stable with no identifiable eating disorders.

As for any major surgical procedure, the preoperative workup should include an ECG and possibly stress testing to rule out cardiac disease. A chest radio-graph may show an enlarged heart or pulmonary congestion. A sleep study may be necessary to evaluate for sleep apnea, which may necessitate the use of a continuous positive airway pressure machine during sleep. Patients with a significant history of heartburn or reflux should undergo an upper gastrointestinal radiograph to rule out a hiatal or paraesophageal hernia, which may alter the surgical plan.

TREATMENT

Nonsurgical Options

Before surgery, all potential candidates should have attempts at lifestyle modifications, including supervised diet and exercise plans. Pharmacologic options include sympathomimetic drugs, such as phentermine or sibutramine (Meridia), or drugs that alter fat digestion, such as orlistat (Xenical). However, most studies have shown that medical management of obesity fails in up to 95% of cases and that most patients regain a substantial portion of their excess weight as soon as medications are discontinued.

Surgical Options

Bariatric surgery has been recognized by the National Institutes of Health as the most effective method to achieve long-term weight loss. A myriad of bariatric surgical procedures have been devised over the years and may be classified as either being restrictive, malabsorptive, or a combination thereof. Restrictive procedures include adjustable gastric banding (AGB), sleeve gastrectomy, and vertical banded gastroplasty. Malabsorptive procedures such as the jejunal-ileal bypass or biliopancreatic diversion have largely fallen out of favor because of issues with malnutrition and organ failure.

The two most commonly performed bariatric surgical procedures in modern practice are AGB and the Roux-en-Y gastric bypass (RYGB). RYGB, the most popular operation in the United States, is both restrictive and malabsorptive. Both AGB and RYGB can be performed either in traditional open fashion or laparoscopically, although the latter approach has significant advantages in decreasing pain, recovery time, and wound complications. Performing these procedures laparoscopically is technically challenging and associated with a significant learning curve.

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RYGB involves the creation of a proximal gastric pouch of approximately 30 mL capacity. Intestinal continuity is restored by attaching a limb of proximal jejunum to this gastric pouch with biliopancreatic continuity established via a jejunojejunostomy (Fig. 10-1).

Patients may experience dumping syndrome postoperatively with RYGB, especially with consumption of highly concentrated sweets. Dumping syndrome is manifested by abdominal cramps, nausea, vomiting, and flushing. In a way, this may be used as an effective form of negative reinforcement to limit the consumption of sweets. Other risks of this procedure include leakage from the intestinal anastomoses, as well as ulcers, strictures, and internal hernias.

Morbidly obese patients are inherently high risk given their propensity for deep venous thrombosis formation and higher incidence of diabetes, hypertension, obstructive sleep apnea, and undiagnosed heart conditions. These all have to be taken into consideration when planning for RYGB. Mortality rate averages 0.5%.

AGB involves placing a silicone band around the upper portion of the stomach (Fig. 10-2). A catheter connects the band to an injection chamber, which is implanted subcutaneously. In the postoperative period, this chamber is used to inflate the band gradually to progressively narrow the gastric inlet and limit caloric intake by controlling portion size. Because no intestines are bypassed, dumping syndrome does not occur. Complications of this procedure include slippage of the stomach around the band, erosion of the band into the lumen of the stomach, and infection, leakage, and migration of the band and injection chamber. Mortality rate averages 0.05%.

RESULTS

Bariatric surgical procedures achieve variable weight loss results. RYGB, whether performed laparoscopically or open, is associated with 75% to 80% excess weight loss (EWL). Excess weight is defined as preoperative weight minus a person's ideal body weight. More importantly, this is associated with resolution of diabetes in approximately 80% to 85% of patients, hypertension in 70% to 80%, and obstructive sleep apnea in 75%. Significant improvements are also seen in lipid profiles and other cardiac risk factors. Long term, there is a 40% decrease in all causes of mortality. Patients need to be monitored

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long term for any signs of mineral and vitamin deficiency. There are case reports of comatose patients as a result of B-complex vitamin deficiencies, as well as problems with calcium deficiencies and transient hair loss; patients usually recover after the first 6 months postoperatively. In the long term, up to 50% of patients who undergo RYGB may have some weight regain, such that the effective long-term excess weight loss is approximately 65% EWL.

AGB achieves 30% to 40% EWL within a year. However, long-term weight loss is approximately 50% to 55% EWL at 5 to 10 years postoperatively. Diabetes improves in approximately 60% of patients, as do most other comorbidities. Good weight loss results with AGB are particularly dependent on compliance with healthy dietary habits, as patients will not develop any dumping syndrome to dissuade them from consuming inordinate amounts of sweets.

Regardless of the surgical procedure, success in terms of postoperative weight loss is still highly dependent upon patient behavior in terms of pursuing healthy dietary and exercise behavior. Patients who continue to overeat and disregard restrictions on portion size run the risk of dilating the gastric pouch in either a RYGB or AGB. Weight regain in the long term can often be attributed not to any technical surgical failure, but to the fact that patients may revert back to unhealthy lifestyle habits.

Key Points

• Morbid obesity is defined as a body mass index >40 kg/m², or a body mass index of 35 to 40 kg/m²with comorbidities such as hypertension, diabetes, or sleep apnea.
• Pharmacologic options such as phentermine, sibutramine, or orlistat may result in some weight loss but rarely achieve sustained results in the long term.
• Surgical options are generally categorized into restrictive and malabsorptive options.
• The two most commonly performed bariatric procedures are the Roux-en-Y gastric bypass and the adjustable gastric band.
• Excess weight loss is approximately 65% to 80% with Roux-en-Y gastric bypass and 50% with adjustable gastric band.
• Both procedures are associated with significant improvements in medical comorbidities.