Gastric bypass is indicated for the surgical treatment of morbid obesity, a diagnosis which is made when the patient is seriously obese, has been unable to achieve satisfactory and sustained weight loss by dietary efforts, and is suffering from co-morbid conditions which are either life-threatening or a serious impairment to the quality of life.
In the past, serious obesity was interpreted to mean weighing at least 100 pounds (45 kg) more than the “ideal body weight”, an actuarially determined body weight at which one was estimated to be likely to live the longest, as determined by the life insurance industry. This criterion failed for persons of short stature.
In 1991, the National Institutes of Health sponsored a consensus panel whose recommendations have set the current standard for consideration of surgical treatment, the body mass index (BMI). The BMI is defined as the body weight (in kilograms), divided by the square of the height (in meters). The result is expressed as a number usually between 20 and 70, in units of kilograms per square meter.
The Consensus Panel of the National Institutes of Health (NIH) recommended the following criteria for consideration of bariatric surgery, including gastric bypass procedures:
People who have a body mass index (BMI) of 40 or higher. Or,
People with a BMI of 35 or higher with one or more related comorbid conditions.
The Consensus Panel also emphasized the necessity of multidisciplinary care of the bariatric surgical patient, by a team of physicians and therapists, to manage associated co-morbidities, nutrition, physical activity, behavior and psychological needs. The surgical procedure is best regarded as a tool which enables the patient to alter lifestyle and eating habits, and to achieve effective and permanent management of their obesity and eating behavior.
Since 1991, major developments in the field of bariatric surgery, particularly laparoscopy, have outdated some of the conclusions of the NIH panel. In 2004, a Consensus Conference was sponsored by the American Society for Bariatric Surgery (ASBS), which updated the evidence and the conclusions of the NIH panel. This Conference, composed of physicians and scientists of many disciplines, both surgical and non-surgical, reached several conclusions, amongst which were:
Bariatric surgery is the most effective treatment for morbid obesity
Gastric bypass is one of four types of operations for morbid obesity.
Laparoscopic surgery is equally effective and as safe as open surgery.
Patients undergo comprehensive pre-operative evaluation, and should have multi-disciplinary support, for optimum outcome.
[edit] Insurance coverage requirements
Many individuals who are considering bariatric surgery as a means of solving severe obesity look to insurance for coverage. Their goal is to obtain coverage for expenses like laboratory fees, surgeon and surgical fees.
Send in a letter of medical requisite for a bariatric surgeon
Provide documentation of a medically supervised diet prior to obtaining coverage
One must provide evidence of failed attempts to lose weight via diet and exercise
While some may obtain coverage for some of the expenses related to bariatric surgery, most insurance companies do not cover supplements post operation.[4]
[edit] Surgical techniques
The gastric bypass, in its various forms, accounts for a large majority of the bariatric surgical procedures performed. It is estimated that 200,000 such operations were performed in the United States in 2008.[5] An increasing number of these operations are now performed by limited access techniques, termed “laparoscopy”.
Laparoscopic surgery is performed using several small incisions, or ports, one of which conveys a surgical telescope connected to a video camera, and others permit access of specialized operating instruments. The surgeon actually views his operation on a video screen. The method is also called limited access surgery, reflecting both the limitation on handling and feeling tissues, and also the limited resolution and two-dimensionality of the video image. With experience, a skilled laparoscopic surgeon can perform most procedures as expeditiously as with an open incision—with the option of using an incision should the need arise.
The Laparoscopic Gastric Bypass, Roux-en-Y, first performed in 1993, is regarded as one of the most difficult procedures to perform by limited access techniques, but use of this method has greatly popularized the operation, with benefits which include shortened hospital stay, reduced discomfort, shorter recovery time, less scarring, and minimal risk of incisional hernia.
[edit] Essential features
The gastric bypass procedure consists in essence of:
Creation of a small, (15–30 mL/1–2 tbsp) thumb-sized pouch from the upper stomach, accompanied by bypass of the remaining stomach (about 400 mL and variable). This restricts the volume of food which can be eaten. The stomach may simply be partitioned (typically by the use of surgical staples), or it may be totally divided into two parts (also with staplers). Total division is usually advocated, to reduce the possibility that the two parts of the stomach will heal back together (“fistulize”), negating the operation.
Re-construction of the GI tract to enable drainage of both segments of the stomach. The technique of this reconstruction produces several variants of the operation, which differ in the lengths of small bowel used, the degree to which food absorption is affected, and the likelihood of adverse nutritional effects.
[edit] Variations of the gastric bypass
[edit] Gastric bypass, Roux en-Y (proximal)
Graphic of a gastric bypass using a Roux-en-Y anastomosis.
This variant is the most commonly employed gastric bypass technique, and is by far the most commonly performed bariatric procedure in the United States. It is the operation which is least likely to result in nutritional difficulties. The small bowel is divided about 45 cm (18 in) below the lower stomach outlet, and is re-arranged into a Y-configuration, to enable outflow of food from the small upper stomach pouch, via a “Roux limb”. In the proximal version, the Y-intersection is formed near the upper (proximal) end of the small bowel. The Roux limb is constructed with a length of 80 to 150 cm (31 to 59 in), preserving most of the small bowel for absorption of nutrients. The patient experiences very rapid onset of a sense of stomach-fullness, followed by a feeling of growing satiety, or “indifference” to food, shortly after the start of a meal.
[edit] Gastric bypass, Roux en-Y (distal)
The normal small bowel is 6 to 10 m (20 to 33 ft) in length. As the Y-connection is moved farther down the Gastrointestinal tract, the amount of bowel capable of fully absorbing nutrients is progressively reduced, in pursuit of greater effectiveness of the operation. The Y-connection is formed much closer to the lower (distal) end of the small bowel, usually 100 to 150 cm (39 to 59 in) from the lower end of the bowel, causing reduced absorption (mal-absorption) of food, primarily of fats and starches, but also of various minerals, and the fat-soluble vitamins. The unabsorbed fats and starches pass into the large intestine, where bacterial actions may act on them to produce irritants and malodorous gases. These increasing nutritional effects are traded for a relatively modest increase in total weight loss.
[edit] Loop Gastric bypass (“Mini-gastric bypass”)
The first use of the gastric bypass, in 1967, used a loop of small bowel for re-construction, rather than a Y-construction as is prevalent today. Although simpler to create, this approach allowed bile and pancreatic enzymes from the small bowel to enter the esophagus, sometimes causing severe inflammation and ulcerationyes either the stomach or the lower esophagus. If a leak into the abdomen occurs, this corrosive fluid can cause severe consequences. Numerous studies show the loop reconstruction (Billroth II gastrojejunostomy) works more safely when placed low on the stomach, but can be a disaster when placed adjacent to the esophagus. Thus even today thousands of “loops” are used for general surgical procedures such as ulcer surgery, stomach cancer and injury to the stomach, but bariatric surgeons abandoned use of the construction in the 1970s, when it was recognized that its risk is not justified for weight management.
The Mini-Gastric Bypass, which uses the loop reconstruction, has been suggested as an alternative to the Roux en-Y procedure, due to the simplicity of its construction, which reduced the challenge of laparoscopic surgery.
[edit] Physiology of the gastric bypass
The gastric bypass reduces the size of the stomach by well over 90%. A normal stomach can stretch, sometimes to over 1000 ml, while the pouch of the gastric bypass may be 15 ml in size. The Gastric Bypass pouch is usually formed from the part of the stomach which is least susceptible to stretching. That, and its small original size, prevents any significant long-term change in pouch volume. What does change, over time, is the size of the connection between stomach and bowel, and the ability of the small bowel to hold a greater volume of food. Over time, the functional capacity of the pouch increases; by that time, weight loss has occurred, and the increased capacity serves to allow maintenance of a lower body weight.
When the patient ingests just a small amount of food, the first response is a stretching of the wall of the stomach pouch, stimulating nerves which tell the brain that the stomach is full. The patient feels a sensation of fullness, as if they had just eaten a large meal—but with just a thumbful of food. Most people do not stop eating simply in response to a feeling of fullness, but the patient rapidly learns that subsequent bites must be eaten very slowly and carefully, to avoid increasing discomfort, or even vomiting.
Food is first churned in the stomach before passing into the small bowel. When the lumen of the small bowel comes into contact with nutrients a number of hormones are released including cholecystikin (CCK) from the duodenum and PYY and GLP-1 from the ileum. These hormones inhibit further food intake and have thus been dubbed satiety factors. Ghrelin, is a hormone that is released in the stomach that stimulates hunger and food intake. Changes in circulating hormone levels after gastric bypass have been hypothesized to produce reductions in food intake and body weight in obese patients. However, these findings remain controversial, and the exact mechanisms by which gastric bypass surgery reduces food intake and body weight have yet to be elucidated.
To gain the maximum benefit from this physiology, it is important that the patient eat only at mealtimes, 5 to 6 small meals daily, and NOT graze between meals, which can effectively “bypass the bypass”. The meals after surgery are 1/4 to a 1/2 cup, slowly getting to 1 cup by 1 year. This requires a change in eating behavior, and alteration of long-acquired habits for finding food. In almost every case where weight gain occurs late after surgery, capacity for a meal has not greatly increased. The cause of regaining weight is eating between meals, usually high-caloric snack foods. There is no known operation which can completely counteract the adverse effects of destructive eating behavior. This surgery is only a tool and as with most tools, if not used correctly, it can be of no use. Concentration on 80 to 100 g of protein daily is necessary.
[edit] Complications
Any major surgery involves the potential for complications—adverse events which increase risk, hospital stay, and mortality. Some complications are common to all abdominal operations, while some are specific to bariatric surgery. A person who chooses to undergo bariatric surgery should know about these risks.
[edit] Mortality and complication rates
The overall complication rate of this type of surgery ranges from 7% for laparoscopic procedures to 14.5% for operations through open incisions, during the 30 days following surgery. Mortality for this study was 0% in 401 laparoscopic cases, and 0.6% in 955 open procedures. Similar mortality rates—30-day mortality of 0.11%, and 90-day mortality of 0.3%—have been recorded in the U.S. Centers of Excellence program, the results from 33,117 operations at 106 centers.
Mortality is affected by complications, which in turn are affected by pre-existing risk factors such as degree of obesity, heart disease, obstructive sleep apnea, diabetes mellitus, and history of prior pulmonary embolism. It is also affected by the experience of the operating surgeon: the “learning curve” for laparoscopic bariatric surgery is estimated to be about 100 cases. Unfortunately, the way a surgeon becomes experienced in dealing with problems is by encountering those problems over time.
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