| Gastric bypass surgery | |
|---|---|
| Intervention | |
| ICD-9-CM | 44.31-44.39 |
| MeSH | D015390 |
Gastric bypass procedures (GBP) are any of a group of similar operations that first divides the stomach into a small upper pouch and a much larger lower "remnant" pouch and then re-arranges the small intestine to allow both pouches to stay connected to it. Surgeons have developed several different ways to reconnect the intestine, thus leading to several different GBP names. Any GBP leads to a marked reduction in the functional volume of the stomach, accompanied by an altered physiological and physical response to food.
The operation is prescribed to treat morbid obesity, defined as a Body mass index greater than 40, and also to treat type 2 diabetes, hypertension, sleep apnea, and other co-morbid conditions. Bariatric surgery is the term encompassing all of the surgical treatments for morbid obesity, not just gastric bypasses, which make up only one class of such operations. The resulting weight loss, typically dramatic, markedly reduces comorbidities. The long-term mortality rate of gastric bypass patients has been shown to be reduced by up to 40%.[1][2] As with all surgery, complications occur. One study, from the years 2005-2006, showed that surgery-related death occurred for 0.5% of patients, from complications within six months of surgery.[3]
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:
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:
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.
While some may obtain coverage for some of the expenses related to bariatric surgery, most insurance companies do not cover supplements post operation.[4]
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.
The gastric bypass procedure consists in essence of:
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.
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.
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 ulceration of 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.
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 should serve 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.
For example, it is still widely perceived that gastric bypass works by mechanical means, i.e., food restriction and/or malabsorption. Recent clinical and animal studies, however, have indicated that these long-held inferences about the mechanisms of Roux en-Y gastric bypass (RYGB) may not be correct. A growing body of evidence suggests that profound changes in body weight and metabolism resulting from RYGB cannot be explained by simple mechanical restriction or malabsorption. One study in rats found that RYGB induced a 19% increase in total and a 31% increase in resting energy expenditure (REE), an effect not exhibited in vertical sleeve gastrectomy rats. In addition, pair-fed rats lost only 47% as much weight as their RYGB counterparts. It seems clear that changes in food intake after RYGB only partially account for the RYGB-induced weight loss, and there is no evidence of clinically significant malabsorption of calories contributing to weight loss. Thus, it appears the RYGB procedure effects weight loss by altering the physiology of weight regulation and eating behavior rather than by simple mechanical restriction and/or malabsorption as previously thought.[6]
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. Some assume the cause of regaining weight must be the patient's fault, e.g., eating between meals with high-caloric snack foods, though this has been debated, and others believe it is an unpredictable failure or limitation of the surgery for certain patients (e.g., reactive hypoglycemia). Of course, there may be no 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.
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.
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. Supervision and experience is important when selecting a surgeon, as the way a surgeon becomes experienced in dealing with problems is by encountering, and solving those problems.
Infection of the incisions or of the inside of the abdomen (peritonitis, abscess) may occur, due to release of bacteria from the bowel during the operation. Nosocomial infection, such as pneumonia, bladder or kidney infections, and sepsis (bloodborne infection) are also possible. Effective short-term use of antibiotics, diligent respiratory therapy, and encouragement of activity within a few hours after surgery, can reduce the risks of infections.
Many blood vessels must be cut in order to divide the stomach and to move the bowel. Any of these may later begin bleeding, either into the abdomen (intra-abdominal hemorrhage), or into the bowel itself (gastrointestinal hemorrhage). Transfusions may be needed, and re-operation is sometimes necessary. Use of blood thinners, to prevent venous thromboembolic disease, may actually increase the risk of hemorrhage slightly.
A hernia is an abnormal opening, either within the abdomen, or through the abdominal wall muscles. An internal hernia may result from surgery, and re-arrangement of the bowel, and is mainly significant as a cause of bowel obstruction. An incisional hernia occurs when a surgical incision does not heal well; the muscles of the abdomen separate and allow protrusion of a sac-like membrane, which may contain bowel or other abdominal contents, and which can be painful and unsightly. The risk of abdominal wall hernia is markedly decreased in laparoscopic surgery.
Abdominal surgery always results in some scarring of the bowel, called adhesions. A hernia, either internal or through the abdominal wall, may also result. When bowel becomes trapped by adhesions or a hernia, it may become kinked and obstructed, sometimes many years after the original procedure. Usually an operation is necessary to correct this problem.
Any injury, such as a surgical operation, causes the body to increase the coagulation of the blood. Simultaneously, activity may be reduced. There is an increased probability of formation of clots in the veins of the legs, or sometimes the pelvis, particularly in the morbidly obese patient. A clot which breaks free and floats to the lungs is called a pulmonary embolus, a very dangerous occurrence. Commonly, blood thinners are administered before surgery, to reduce the probability of this type of complication.
An anastomosis is a surgical connection between the stomach and bowel, or between two parts of the bowel. The surgeon attempts to create a water-tight connection by connecting the two organs with either staples or sutures, either of which actually makes a hole in the bowel wall. The surgeon will rely on the healing power of the body, and its ability to create a seal like a self-sealing tire, to succeed with the surgery. If that seal fails to form, for any reason, fluid from within the gastrointestinal tract can leak into the sterile abdominal cavity and give rise to infection and abscess formation. Leakage of an anastomosis can occur in about 2% of gastric bypass procedures, usually at the stomach-bowel connection. Sometimes leakage can be treated with antibiotics, and sometimes it will require immediate re-operation. It is usually safer to re-operate if an infection cannot be definitely controlled immediately.
As the anastomosis heals, it forms scar tissue, which naturally tends to shrink ("contract") over time, making the opening smaller. This is called a "stricture". Usually, the passage of food through an anastomosis will keep it stretched open, but if the inflammation and healing process outpaces the stretching process, scarring may make the opening so small that even liquids can no longer pass through it. The solution is a procedure called gastroendoscopy, and stretching of the connection by inflating a balloon inside it. Sometimes this manipulation may have to be performed more than once to achieve lasting correction.
Ulceration of the anastomosis occurs in 1-16% of patients.[7] Possible causes of such ulcers are:
This condition can be treated as follows:
Normally, the pyloric valve at the lower end of the stomach regulates the release of food into the bowel. When the Gastric Bypass patient eats a sugary food, the sugar passes rapidly into the bowel, where it gives rise to a physiological reaction called dumping syndrome. The body will flood the intestines in an attempt to dilute the sugars. An affected person may feel their heart beating rapidly and forcefully, break into a cold sweat, get a feeling of butterflies in the stomach, and may have a "sky is falling" type of anxiety. He/she usually has to lie down, and could be very uncomfortable for about 30 to 45 minutes. Diarrhea may then follow.
After surgery, patients feel fullness after ingesting only a small volume of food, followed soon thereafter by a sense of satiety and loss of appetite. Total food intake is markedly reduced. Due to the reduced size of the newly created stomach pouch, and reduced food intake, adequate nutrition demands that the patient follow the surgeon's instructions for food consumption, including the number of meals to be taken daily, adequate protein intake, and the use of vitamin and mineral supplements. Calcium supplements, iron supplements, protein supplements, multi-vitamins (sometimes pre-natal vitamins are best) and B12 (cyanocobalamin) supplements are all very important to the post-operative bypass patient.
The total food intake and absorbance rate of food will rapidly decline after gastric bypass surgery. After gastric bypass surgery there is an increase in the number of acid producing cells in the lining of the stomach. Many doctors are prescribing acid lowering medications to counteract the high acidity levels. Many patients then experience a condition known as achlorhydria. Achlorhydria is a condition where there is not enough acid in stomach. Patients can develop an overgrowth of bacteria as a result of the low acidity levels in the stomach. A study conducted on 43 post operative patients revealed that almost all of the patients tested positive for a hydrogen breath test, which determined an overgrowth of bacteria in the small intestine[10] The overgrowth of bacteria will cause the gut ecology to change and will induce nausea and vomiting. Recurring nausea and vomiting will change the absorbance rate of food which contributes to the vitamin and nutrition deficiencies common in post operative gastric bypass patients.
Proteins are essential food substances, contained in foods such as meat, fish and poultry, dairy products, soy, nuts, and eggs. With reduced ability to eat a large volume of food, gastric bypass patients must focus on eating their protein requirements first, and with each meal. In some cases, surgeons may recommend use of a liquid protein supplement. Powdered protein supplements added to smoothies or any food can be an important part of the post-op diet.
The profound weight loss which occurs after bariatric surgery is due to taking in much less energy (calories) than the body needs to use every day. Fat tissue must be burned, to offset the deficit, and weight loss results. Eventually, as the body becomes smaller, its energy requirements are decreased, while the patient simultaneously finds it possible to eat somewhat more food. When the energy consumed is equal to the calories eaten, weight loss will stop. Proximal GBP typically results in loss of 60 to 80% of excess body weight, and very rarely leads to excessive weight loss. The risk of excessive weight loss is slightly greater with Distal GBP.
Vitamins are normally contained in the foods we eat, as well as any supplements we may choose to take. The amount of food which will be eaten after GBP is severely reduced, and vitamin content is correspondingly reduced. Supplements should therefore be taken, to completely cover minimum daily requirements of all vitamins and minerals. Pre-natal vitamins are sometimes suggested by doctors, as they contain more of certain vitamins than "regular" multi-vitamins. Absorption of most vitamins is not seriously affected after proximal GBP, although vitamin B12 may not be well-absorbed in some persons. Sublingual preparations of B12 will provide adequate absorption. Some studies suggest that GBP patients who took probiotics after surgery were able to absorb and retain higher amounts of B12 than patients who did not take probiotics after surgery. After the distal GBP, fat-soluble vitamins A, D and E may not be well-absorbed, particularly if fat intake is large. Water-dispersed forms of these vitamins may be indicated, on specific physician recommendation. For some patients, sublingual B12 is not enough, and patients may require B12 injections.
All versions of the GBP bypass the duodenum, which is the primary site of absorption of both iron and calcium. Iron replacement is essential in menstruating females, and supplementation of iron and calcium is preferable in all patients. Ferrous sulfate is poorly tolerated. Alternative forms of iron (fumarate, gluconate, chelates) are less irritating and probably better absorbed. Calcium carbonate preparations should also be avoided; calcium as citrate or gluconate, 1200 mg as calcium, has greater bioavailability independent of acid in the stomach, and will likely be better absorbed. Chewable calcium supplements that include vitamin K are sometimes recommended by doctors as a good way to get calcium.
There was a study that confirmed post operative gastric bypass patients will absorb alcohol at a faster rate than people who have not undergone the surgery. It will also take a post operative patient longer to reach sober levels after consuming alcohol than those who have not undergone the surgery. A study was conducted on 36 post operative patients and a control group of 36 subjects who have not undergone the surgery. Each subject was given a 5 oz of glass of red wine and the alcohol in their breath was measured to evaluate their alcohol metabolism. The gastric bypass group had an average peak alcohol breath level at 0.08%. The control group had an average peak alcohol breath level of 0.05%. It took on average 108 minutes for the gastric bypass patients group to return to an alcohol breath of zero, while it took the control group an average of 72 minutes to return to an alcohol breath of zero.[11] Patients who have undergone gastric bypass surgery will have a lower tolerance than people who have not gone through the surgery. It will also take a gastric bypass patient longer to return to a sober level after drinking alcohol than a person who has consumed alcohol that has not had the surgery.
There was a study conducted that confirmed the development of pica after gastric bypass surgery due to iron deficiencies. Pica is a compulsive tendency to eat substances other than normal food. Some examples would be people eating paper, clay, plaster, ashes, or ice. A study was conducted on a female post operative gastric bypass patient who was consuming eight to ten 32oz glasses of ice a day. The patient's blood test revealed iron levels of 2.3 mmol/L and hemoglobin level of 5.83 mmol/L. The patient was then given iron supplements that brought her hemoglobin and iron blood levels to a normal level. After one month the patient's eating diminished to two to three glasses per day. After one year of taking iron supplements the patient's iron and hemoglobin levels remained in a normal range and the patient reported that she did not have any further cravings for ice. The patient was eating ice due to the iron deficiencies that occurred after gastric bypass surgery. Low levels of iron and hemoglobin are common in patients who have undergone gastric bypass. Pica is more common in gastric bypass patients who have a history of the condition prior to the surgery.[12]
Weight loss of 65 to 80% of excess body weight (the amount by which actual body weight exceeds actuarial ideal body weight) is typical of most large series of Gastric Bypass operations reported. The medically more significant effects are a dramatic reduction in co-morbid conditions:
A recent study in a large comparative series of patients showed an 89% reduction in mortality over the 5 years following surgery, compared to a non-surgically treated group of patients.
Concurrently, most patients are able to enjoy greater participation in family and social activities.
Gastric bypass surgery has an emotional, as well as a physiological, impact on the individual. Many who have undergone the surgery suffer from depression in the following months.[14] This is a result of a change in the role food plays in their emotional well-being. Strict limitations on the diet can place great emotional strain on the patient. Energy levels in the period following the surgery will be low. This is due again to the restriction of food intake, but the negative change in emotional state will also have an impact here.[15] It may take as long as three months for emotional levels to rebound. Muscular weakness in the months following surgery is common. This is caused by a number of factors, including a restriction on protein intake, a resulting loss in muscle mass and decline in energy levels. The weakness may result in balance problems, difficulty climbing stairs or lifting heavy objects, and increased fatigue following simple physical tasks. Many of these issues will pass over time as food intake gradually increases. However, the first months following the surgery can be very difficult, an issue not often mentioned by physicians suggesting the surgery. The benefits and risks of this surgery are well established; however, the psychological effects are not well understood, and potential patients should ensure a strong support system before agreeing to the procedure. It is important for patients to start changing their outlook on food and diets before surgery to avoid the shock after.
The American Society for Metabolic & Bariatric Surgery lists bariatric programs and surgeons in its "Centers of Excellence" network,[16] while the American College of Surgeons accredits providers through its Bariatric Surgery Center Network.[17] For listings of surgeons and centers in other countries, the International Federation for the Surgery of Obesity and Metabolic Disorders lists medical associations by country.[18]