CHOOSING THE RIGHT
SURGICAL TECHNIQUE
"I had a gastric bypass, because after talking it over with my surgeon, it seemed as if that was the safest, most effective way to go for me."
Ted J, 51, 292 lbs pre-op; 172 lbs, 6 years post-op
The field of bariatric surgery has been evolving for several decades. The concept of using gastrointestinal surgery to control obesity grew out of results of operations for cancer or peptic ulcer disease in which large portions of the stomach or small intestine were removed. Because patients undergoing these procedures tended to lose a great deal of weight after surgery, some surgeons adapted these operations to treat severe obesity.
Operative procedures have been refined as knowledge about obesity, nutrition and the consequences of different surgical techniques has increased. Each technique entails risks and benefits. The risks are the complications that result from the procedure while the benefits relate to the amount of weight lost, reduction of co-morbid conditions, and improvements in life-style. Usually, the procedures that produce the greatest weight loss are associated with higher operative risk and most complications. The best operation for any individual involves a careful analysis balancing all of the risks and benefits.
In order to understand the different operations that are performed for the treatment of obesity, it is necessary to be familiar with the anatomy and function of the gastrointestinal (GI) tract.
The GI tract is essentially a tube, measuring about 30 feet, extending from the mouth to the anus,. Along its path, it is divided into specialized portions, known as the esophagus, stomach and small intestine and the large intestine. Each of these sections has a unique structure and function involved in the transportation, absorption and digestion of nutrients.
The esophagus is a narrow straight tube connecting the throat to the stomach, whose primary function is to serve as a passageway for food. No digestion or absorption occurs there. The esophagus is separated from the stomach by a muscle, the lower esophageal sphincter, which allows food to enter and, when functioning normally, prevents stomach contents from flowing back upward, causing "acid reflux" and heartburn.
The stomach is the site of the initial breakdown of food. As food enters the stomach, it comes into contact with acid and digestive enzymes (proteins that facilitate digestion) that are secreted by the stomach. The presence of food in the stomach stimulates other parts of the GI tract to release hormones to assist in other aspects of digestion. The stomach wall is muscular and churns the food until is transformed into a thick "mush" (chyme) that can be transported into the small intestine. Additionally, the stomach secretes a chemical (intrinsic factor) that assists in the absorption of vitamin B12.
The partially digested food is squeezed out of the stomach through an opening, known as the pylorus, into the duodenum, which is the first part of the small intestine. The duodenum, which is only about two feet in length, is strategically located near the stomach, pancreas, liver and gallbladder. In addition to the stomach contents, it receives bile from the liver and gallbladder along with hormones and enzymes from the pancreas that assist with digestion. Dietary iron and calcium are predominantly absorbed into the body in the duodenum.
The duodenum is connected to the jejunum and ileum, which make up the remaining 20 or so feet of small intestine and are the site for the absorption of most nutrients. Hormones, with the assistance of digestive enzymes, break down carbohydrates, proteins and fats into their smaller components so they can be absorbed into the bloodstream.
The primarily liquid contents of the small intestine are then emptied into the colon. Here, the excess water is reabsorbed into the body, leaving behind feces, which are stored until they are eliminated by passing through the rectum and anus.
The process of digestion is analogous to a finely tuned symphony orchestra, with each musician having a unique role in the process.
Operations for the treatment of obesity are classified based upon how they work. One group of procedures functions by preventing the normal absorption of nutrients, and are known as "malabsorptive" procedures. Another group of operations limits the amount of food that can be consumed and are termed "restrictive" procedures. There are also operations that act by combining these two mechanisms.
Jejunoileal Bypass (JIB): The first operation widely performed for the treatment of obesity was known as the jejunoileal bypass (JIB) or the intestinal bypass (shown in Figure 6-2). The JI bypass consisted of dividing the small intestine near its origin in the jejunum and connecting it to the ileum close to its end. This resulted in "bypassing" most of the small intestine (about 18 feet), leaving only about 2 feet for the absorption of nutrients. The JI bypass was highly successful in producing weight loss, however about half of the patients who had a JI bypass developed complications requiring readmission to the hospital. These adverse effects included diarrhea producing severe malnutrition and deficiencies in many vitamins, nutrients and essential bodily chemicals. Some patients developed kidney stones that led to kidney failure, requiring dialysis. The most serious complication was liver malfunction, which occurred in almost all patients, and progressed to fatal liver failure in about 10 percent. This side effect could not be predicted, treated or prevented.
The high incidence and severity of complications necessitated reversal of the procedure in about 25 percent of patients. For these reasons, JIB was abandoned by the surgical community in about 1980. It is currently the recommendation of the American Society of Bariatric Surgery that patients with an intact JIB undergo conversion to a safer weight loss procedure, even if they have no symptoms.
Gastroplasty: Gastroplasty is a general term used to describe those weight loss procedures that involve partitioning the stomach into a small pouch near the junction between the esophagus and the stomach that holds about 1 ounce. Because the partition is usually performed using surgical staplers, these procedures are commonly referred to "stomach staplings".
These procedures produce weight loss exclusively by limiting food intake. The gastroplasty works because one can only eat small amounts before becoming full. Eating too much stretches the pouch, causing pain, nausea and vomiting. Numerous variations of gastroplasty were devised and subsequently abandoned because of a high rate of failure (Figure 6-3). Failure was often the result of technical problems related to the staples. Many times the staples pulled out, allowing the stomach to return to its normal size, thereby allowing food intake to increase to preoperative levels. The staplers currently in use are much improved and these problems are rare.
The form of gastroplasty in popular use today was introduced by Dr. Edward Mason in the 1970s and is known as Vertical Banded Gastroplasty (VBG, Figure 6-4). This operation is performed by creating a one-ounce-sized pouch near the junction of the stomach and esophagus using a vertically placed staple line. The channel connecting the pouch to the remainder of the stomach is then reinforced with a permanent band [usually 1 cm (about ½ inch) in width and 5.5 cm (2 ½ inches) in length] made of silicone, silastic or polypropylene to prevent the opening from stretching. Food passes through the pouch into the rest of the stomach where it is digested normally. The effectiveness of the operation is closely related to the size of the opening. Gastroplasty works by restriction only, by limiting the amount of food that can be eaten at one sitting. However, it can be sabotaged by the ingestion of high calorie, sweet liquids such as ice cream and shakes.
Figure 6-4: Vertical Banded Gastroplasty (VBG)
Gastric Banding: Gastric banding is a modification of gastroplasty in which a stomach pouch is created by encircling the upper stomach with a silastic or silicone band (Figure 6-5). This creates an hourglass appearance and functions by limiting the consumption of food and then delaying its passage into the rest of the stomach. Some of the bands are adjustable, allowing them to be loosened or tightened as needed. At this time, most of the clinical experience with gastric banding has been in Europe. In the United States, the Food and Drug Administration is evaluating preliminary results of banding procedures prior to its approval for use.
Figure 6-5: Gastric Banding
Several procedures currently in use are a combination of restrictive and malabsorptive procedures.
Roux-en-Y Gastric Bypass (RYGB): The Roux-en-Y gastric bypass (Figure 6-6), which was also developed by Dr. Edward Mason, is the most popular bariatric procedure performed in the United States. It is a combination of restrictive and malabsorptive procedures. The restrictive component consists of making a small pouch near the junction of the esophagus and the stomach using a surgical stapler. The malabsorptive portion is created by dividing the small intestine and re-routing it so that one portion is connected to the small stomach pouch (the "Roux-limb" or "alimentary-limb") and the remaining portion, which delivers the bile and pancreatic juice, is reconnected to the small intestine at a predetermined distance from the stomach (the "bilio-pancreatic limb").
Several variations of this procedure exist in which surgeons use different lengths for the alimentary and the bilio-pancreatic limbs. Lengths of the alimentary or bilio-pancreatic limbs range from 30 cm (12 in) to 250 cm (100 in), with different surgeons using different combinations. Shorter limbs are referred to as "proximal" and longer limbs as "distal." In patients who have a BMI less than 50, the limb length does not appear to affect the amount of weight loss. However, in heavier patients, with a BMI greater than 50, studies performed by Robert Brolin M.D. and by Patricia Choban M.D. and myself, have shown that longer alimentary-limb lengths, 150 cm (60 in) and 250 cm (100 in), helped patients lose more than 50 percent of their excess body weight.
Figure 6-6: Gastric Bypass (RYGB)
Fobi Pouch: Another variant of the RYGB incorporates the placement of a band just before the connection between the stomach and jejunum (Figure 6-7). The purpose of the band is to retard the flow of food, as occurs with a vertical banded gastroplasty, and allow for a larger opening between the stomach and small intestine. This procedure has been popularized by Dr. Mathias A.L. Fobi and is often referred to as the "Fobi pouch".
Bilio-Pancreatic Diversion (BPD): Since the 1980s, the JI bypass has been replaced by a more moderate malabsorptive procedure, known as the bilio-pancreatic diversion or "Scopanaro procedure", named after Dr. Nicola Scopanaro, the Italian surgeon who first devised it (Figure 6-8). This operation consists of several steps. First, about half of the stomach is removed in order to limit food intake. Then, most of the small intestine is re-routed, similar to that which is done in the gastric bypass, to separate the flow of food leaving the stomach from the digestive juices of the liver and pancreas. This, in turn, decreases digestion and absorption. These paths are finally brought back together to mix as a "common channel" in the final 2 feet of the small intestine.
However, malnutrition occurs in about 10 percent of patients with additional nutritional deficiencies, such as low calcium levels and bone disease in even more. This operation is popular in parts of Europe, especially Italy. Nevertheless, most bariatric surgeons in the United States feel that BPD is too radical an operation for most patients and its precise role in the management of severe obesity remains to be determined. For these reasons, BPD was not evaluated during the NIH Consensus Development Conference on the Surgical Treatment of Obesity in 1991.
Bilio-Pancreatic Diversion with Duodenal Switch: A variation of the bilio-pancreatic bypass, known as the Duodenal Switch (DS, Figure 6-9), has been developed in the United States by Douglas Hess M.D. and is currently preferred over the standard BPD by some surgeons in the United States and Canada. This modification involves connecting the re-routed small intestine to the duodenum instead of the stomach, which results in a lower incidence of stomach ulcers than the standard BPD. Only a few studies describing the long-term results of the DS have been published. The prevailing view of most bariatric surgeons in the United States is that DS, like BPD, is too radical for most patients, but that it probably has a limited role that remains to be determined.
Figure 6-9: Duodenal Switch (DS)
Thus, of the "combined" procedures, the RYGB functions more like a restrictive procedure, while the BPD and the DS are more like malabsorptive procedures.
Note: The RYGB, BPD and DS all involve division and reconstruction of the gastrointestinal tract using a technique called "Roux-en-Y" in which the intestine is reconnected in the shape of the letter Y. This technique was first employed by Cesar Roux, a Swiss surgeon in the late 19th century. The name credits him for the technique while describing the anatomy of the intestinal reconstruction. Thus, the abbreviation "RNY", which is sometimes used for the Roux-en-Y gastric bypass is inaccurate
"My surgeon explained to me how gastric bypass works. I'm not sure if I quite understand it all. All I know is that I can eat almost anything that I enjoy, but I become full much faster. I eat much smaller portions, and consequently, I've lost a lot of weight and kept it off for a long time."
Cathy T, 36, 327 lbs pre-op; 189 lbs 5 years post-op.
"I'm not even sure that doctors know exactly how this operation worksbut the amazing part is that it does."
Jill M, 33, 306 lbs pre-op; 173 lbs 2 years post-op.
The malabsorptive procedures produce weight loss by preventing the normal absorption of nutrients. The different procedures either short circuit parts of the GI tract so that food passes through too quickly to be properly digested or absorbed, or they re-route the food so that it bypasses certain parts of the GI tract and does not come into contact with the hormones and juices necessary for digestion.
The restrictive procedures promote weight loss by limiting food intake through partitioning the stomach with staples or dividing it. When food enters this "smaller" stomach, the pouch quickly fills up, stretching the sides. Signals are then sent to the brain indicating a feeling of fullness. If too much food is consumed and the pouch is stretched too quickly, pain followed by nausea and vomiting can result.
The combined procedures, which involve both restrictive and malabsorptive components, also appear to induce weight loss by altering the way the body uses energy. After a restrictive operation, patients consume small quantities of food for several months, usually about 500 calories per day after 6 weeks, 800-1000 calories per day at 6 months and 1200-1400 calories per day after 1 year. Such a low level of caloric intake is called semi-starvation. Normally, when people diet and consume such reduced amounts of food, the body interprets it as a threat to health. The body then compensates for this by lowering the amount of energy consumed in order to try to preserve body weight. Energy consumption can be reduced by as much as 30 percent, which is one of the primary reasons that it is often so difficult to lose weight by dieting alone. One purpose of combining exercise with dieting is to offset this reduction in energy utilization.
My colleague, Patricia Choban M.D., and I measured the amount of energy expended by our patients who underwent RYGB. We found that despite the fact that they were consuming markedly reduced amounts of food than prior to surgery--between 500 and 1200 calories per day, which should have caused a reduction in their energy use by 15 to 30 percent-- their energy expenditure was normal.
Earlier research involving patients who had a VBG, a purely restrictive operation, showed a reduction in energy consumption, similar to what happens when patients go on an ordinary diet. Thus, we believe that this "paradoxical response" after RYGB, in which patients maintain a normal level of energy use despite low caloric intake, and do not demonstrate the expected slowdown in metabolic rate, may be responsible for the increased weight loss observed after RYGB when compared to VBG.
