Inside the operating room—balancing the risks and benefts of new surgical procedures
Bariatric surgery: What role for ethics as established procedures approach new frontiers?
By Philip R. Schauer, MD
Obesity is a staggering problem: 100 million Americans are overweight, 85 million more are obese, and another 15 million are morbidly obese (ie, ≥ 100 lbs above ideal body weight). The incidence of obesity is rising rapidly and threatens to shorten the life spans of today’s young generations relative to their parents. Unlike other conditions, such as cardiovascular disease and cancer, obesity has seen no widespread progress in management in recent years.
Recognition of obesity as a medical problem is a challenge in itself. Many people consider obesity to be a character flaw or a behavioral issue and fail to recognize it as a disease entity. Yet obesity is the root cause of many metabolic conditions and diseases with metabolic components, including type 2 diabetes, heart disease, blood pressure, metabolic syndrome, acid reflux, gout, arthritis, and sleep apnea.
The approach to obesity treatment can be conceptualized as a pyramid, with the aggressiveness of the intervention based on the patient’s body mass index (BMI). At the base of the pyramid, for patients with lower BMIs, are minimally invasive (and minimally effective) interventions involving changes in diet, physical activity, and other lifestyle factors. As BMI increases, so does the intensity of treatment, to include pharmacotherapy and eventually bariatric surgery. Traditionally, surgery has been considered only at the very top of the pyramid, for morbidly obese patients, and is usually not offered as an option for the vast majority of people with this condition.
The sad reality is that the various combinations of these therapies are effective in fewer than 1% of the approximately 100 million Americans who are obese. Because surgery has been shown to be the most effective therapy for obesity, the remainder of my discussion will focus on surgery, with an eye toward potential new indications for bariatric procedures and the questions they raise.
SURGICAL APPROACHES TO OBESITY
Bariatric surgery has evolved over the past 50 years. Although there are about a dozen different permutations of bariatric procedures performed in the United States today, they fall into one of three major types of operations, as outlined below:
Gastric banding reduces appetite and satiety by adjusting and tightening the gastric band. This procedure has been in existence for 10 to 15 years and represents about 25% of operations for obesity in the United States.
The biliopancreatic diversion procedure diverts most of the small bowel and radically reduces absorption of calories. Patients undergoing this procedure lose weight because few calories are absorbed into the body. This approach, while quite effective, is somewhat radical and represents only about 2% of the operations for obesity in the United States.
The Roux-en-Y gastric bypass procedure has been the dominant procedure over the past 15 to 20 years. A combination of the above two procedures, it involves reducing the gastric reservoir and bypassing the stomach and upper intestine. The reduction in gastric volume reduces calorie intake by enhancing satiety, and the limited foregut bypass moderately reduces absorption.
No randomized trials, but much support from observational studies
Virtually none of these procedures evolved with randomized controlled trals. Instead, they evolved incrementally, primarily on the basis of knowledge gained from case procedures. Despite the lack of randomized trials, these operations have been shown to be effective, particularly in patients with multiple metabolic abnormalities associated with severe obesity. A large body of data from case-control and cohort studies demonstrates not only dramatic improvement in metabolic abnormalities with the use of various bariatric procedures, but also improvements in quality of life and survival.20–26 The two most recent of these studies, published in 2007, found reductions in mortality of 29% (adjusted) and 40% among surgical patients compared with well-matched obese controls during mean follow-up of more than 7 years.25,26 Reductions in the incidence of cardiovascular mortality and, secondly, cancer-related mortality were the two major contributors to the overall mortality reduction in these two studies. Consistent with this latter finding, obesity is starting to be thought of as a disease that may lead to cancer.
NEW FRONTIERS FOR BARIATRIC PROCEDURES
The current indications for bariatric surgery have existed intact for about 25 years, and were based on limited evidence available at the time. They are basically as follows, assuming acceptable operative risk and appropriate patient expectations:
- BMI greater than 40 kg/m2
- BMI greater than 35 kg/m2 with significant obesity-related comorbidities.
Payors adhere strictly to these indications, such that they will not pay for bariatric surgery in a patient with a BMI less than 35 kg/m2. This raises questions about the appropriateness of such a firm threshold and whether expansion of these strict indications may be reasonable.
Even without broadened indications, the volume of bariatric procedures in the United States has grown dramatically in recent years. Whereas only 10,000 to 20,000 of these operations were performed annually in the 1990s, approximately 200,000 such procedures were performed in 2007, and this number is expected to double over the next 5 years or so.
This growth in volume has been paralleled by burgeoning media interest in bariatric procedures, particularly in the last few years. More attention can be expected as we increasingly recognize the potential of bariatric procedures for indications beyond strictly the treatment of morbid obesity. At least two new frontiers loom: metabolic surgery and endoscopic surgery.
Metabolic surgery
Procedures that incorporate a bypass—the Roux-en-Y gastric bypass and the biliopancreatic diversion —have been associated with a reversal of metabolic diseases such as type 2 diabetes.27–32 Many patients with type 2 diabetes who have undergone these procedures have been able to be weaned off insulin and insulin-sensitizing medications while maintaining normal blood glucose levels. The effect has been profound and immediate, occurring even before the patient loses weight. In one series of patients with type 2 diabetes who had undergone a bypass operation, 30% left the hospital in a euglycemic state.29
These observations have been made primarily in the morbidly obese population, who are the primary candidates for bariatric bypass procedures. However, because of the rapid improvement in metabolic abnormalities that has been observed, interest has arisen in applying these procedures to populations that are not morbidly obese. Bypassing of the foregut appears to be critical, perhaps because it tempers the release of hormonally active peptides from the gastrointestinal tract.33 In any case, the gut is regaining recognition as a major metabolic organ.
In light of these hypotheses, the duodenal-jejunal bypass is a bariatric procedure that may be beneficial for a patient with type 2 diabetes who is not morbidly obese. In this operation, the stomach volume is preserved but the foregut is bypassed. In a small experimental series from Brazil, patients with type 2 diabetes who were normal weight or only slightly overweight had resolution of their diabetes following this procedure, without any weight loss.34
New applications for endoscopy
Another area of development is endoluminal and transgastric bariatric surgery. Endoluminal surgery is performed entirely within the lumen of the gastrointestinal tract using flexible endoscopy. Transgastric surgery is performed within the peritoneal cavity, which is accessed via a hollow viscus. Both approaches use natural orifices to gain surgical access, thereby avoiding access incisions and scars.35
The benefits of such an approach are numerous:
(1) fewer complications and side effects; (2) less invasiveness, and thus the ability to perform in the outpatient setting; (3) reduced procedure costs; and (4) better access to treatment. The implication in terms of indications is the potential to use such procedures to prevent progression to morbid obesity.
Examples of these procedures are proliferating:
Gastrojejunostomy reduction is an endoscopic procedure that involves reducing the dilated opening of the gastric pouch after gastric bypass surgery. New endoscopic suturing or stapling devices enable the outlet reduction without requiring surgery. The result is enhancement of weight loss without a major operation.
Endoluminal suturing uses endoscopic instruments to suture the stomach to reduce its volume. When this procedure is perfected, the patient should be able to leave the endoscopy suite and return home within a few hours.
The duodenal sleeve is an avant garde concept in which an internal sleeve is threaded into the stomach and down the intestines.36 The sleeve covers the absorptive surface of the small bowel, preventing absorption of nutrients to cause weight loss. This procedure has been shown to have a strong antidiabetic effect as well.
Clinical applications of these operations are emerging. An endoluminal sutured gastroplasty procedure to shrink stomach volume has been shown in a small clinical trial to cause loss of significant excess body weight; the operation leaves no scars and is associated with a low risk of bleeding or any type of surgical complication.37 A similar procedure is in development that involves staples instead of sutures.
How best to validate innovations moving forward?
As we move into these new eras of metabolic surgery and endoluminal and transgastric bariatric surgery, interesting questions arise. We as innovators and caregivers are ethically obligated to demonstrate reasonable safety and efficacy before such new procedures are performed widely. Although some of these emerging procedures involve new devices that will go through the FDA review process, many are existing procedures for which indications may be expanded, while others are permutations of existing procedures for which no formal rules for validation exist. For new procedures that differ substantially from existing proven procedures but which do not require new devices, should we not be ethically bound to demonstrate safety and efficacy even though they do not require FDA review? These are the challenges that await as innovation takes bariatric surgery to new frontiers.
