Gastric bypass surgery

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Gastric bypass surgery
Intervention
ICD-9-CM44.31-44.39
MeSHD015390
MedlinePlus007199
 
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Gastric bypass surgery
Intervention
ICD-9-CM44.31-44.39
MeSHD015390
MedlinePlus007199

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 connect to both. 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), type 2 diabetes, hypertension, sleep apnea, and other comorbid 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. A study from 2005 to 2006 revealed that 15% of patients experience complications as a result of gastric bypass, and 0.5% of patients died within six months of surgery due to complications.[3]

Surgical indications[edit]

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 suffers from comorbid conditions which are either life-threatening or a serious impairment to the quality of life.

In the past[when?], clinicians interpreted serious obesity as 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 (NIH) 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 comorbidities and 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 the American Society for Bariatric Surgery (ASBS) sponsored a consensus conference which updated the evidence and the conclusions of the NIH panel. This conference, composed of physicians and scientists of both surgical and non-surgical disciplines, reached several conclusions, including:

Surgical techniques[edit]

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 to insert a surgical telescope connected to a video camera, and others to permit access of specialized operating instruments. The surgeon views his operation on a video screen. Laparoscopy is also called limited access surgery, reflecting 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 Roux-en-Y laparoscopic gastric bypass, 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 due to associated benefits such as a shortened hospital stay, reduced discomfort, shorter recovery time, less scarring, and minimal risk of incisional hernia.

Essential features[edit]

The gastric bypass procedure consists of:

Variations of the gastric bypass[edit]

Gastric bypass, Roux en-Y (proximal)[edit]

Graphic of a gastric bypass using a Roux-en-Y anastomosis. The transverse colon is not shown so that the Roux-en-Y can be clearly seen. The variant seen in this image is retrocolic, retrogastric, because the distal small bowel that joins the proximal segment of stomach is behind the transverse colon and stomach.
Illustration of Roux-en-Y gastric bypass surgery

This variant is the most commonly employed gastric bypass technique, and is by far the most commonly performed bariatric procedure in the United States. The small intestine is divided approximately 45 cm (18 in) below the lower stomach outlet and is re-arranged into a Y-configuration, enabling 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 intestine. The Roux limb is constructed using 80–150 cm (31–59 in) of the small intestine, preserving the rest (and the majority) of it for absorbing nutrients. The patient will experience very rapid onset of the stomach feeling full, followed by a growing satiety (or "indifference" to food) shortly after the start of a meal.

Gastric bypass, Roux en-Y (distal)[edit]

The small intestine is normally 6–10 m (20–33 ft) in length. As the Y-connection is moved further down the gastrointestinal tract, the amount available to fully absorb nutrients is progressively reduced, traded for greater effectiveness of the operation. The Y-connection is formed much closer to the lower (distal) end of the small intestine, usually 100–150 cm (39–59 in) from the lower end, causing reduced absorption (malabsorption) 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 larger effects on nutrition are traded for a relatively modest increase in total weight loss.

"Mini-gastric bypass" (MGB)[edit]

The mini gastric bypass procedure was first developed by Dr Robert Rutledge from the USA in 1997, as a modification of the standard Billroth II procedure. A mini gastric bypass creates a long narrow tube of the stomach along its right border (the lesser curvature). A loop of the small gut is brought up and hooked to this tube at about 180 cms from the start of the intestine

Numerous studies show that 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. Today thousands of "loops" are used for surgical procedures to treat gastric problems such as ulcers, stomach cancer, and injury to the stomach. The mini gastric bypass uses the low set loop reconstruction and thus has rare chances of bile reflux.

The MGB has been suggested as an alternative to the Roux en-Y procedure due to the simplicity of its construction, and is becoming more and more popular because of low risk of complications and good sustained weight loss. It has been estimated that 15.4% of weight loss surgery in Asia is now performed via the MGB technique.[6]

Physiology[edit]

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 the stomach and intestine and the ability of the small intestine 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 thumb-full 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 vomiting.

Food is first churned in the stomach before passing into the small intestine. When the lumen of the small intestine comes into contact with nutrients, a number of hormones are released, including cholecystokinin 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, an effect not exhibited in vertical sleeve gastrectomy rats. In addition, pair-fed rats lost only 47% as much weight as their RYGB counterparts. 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 RYGB affects weight loss by altering the physiology of weight regulation and eating behavior rather than by simple mechanical restriction or malabsorption.[7]

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". Concentration on obtaining 80–100 g of daily protein is necessary. Meals after surgery are 1/4–1/2 cup, slowly getting to 1 cup by one 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. 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.

Complications[edit]

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.

Mortality and complication rates[edit]

The overall rate of complications during the 30 days following surgery ranges from 7% for laparoscopic procedures to 14.5% for operations through open incisions. One study on mortality revealed a 0% mortality rate out of 401 laparoscopic cases, and 0.6% out of 955 open procedures (6 Deaths). Similar mortality rates—30-day mortality of 1.1% (364 deaths), and 90-day mortality of 0.3%—have been recorded in the U.S. Centers of Excellence program, the results being from 33,117 operations at 106 centers.[8]

Mortality and complications 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 them.

Complications of abdominal surgery[edit]

Infection[edit]

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 infections, such as pneumonia, bladder or kidney infections, and sepsis (blood-borne 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.

Venous thromboembolism[edit]

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. Blood thinners are commonly administered before surgery to reduce the probability of this type of complication.

Hemorrhage[edit]

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.

Hernia[edit]

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 a cause of bowel obstruction. Antecolic antegastric Roux-en-Y gastric bypass surgery has been estimated to result in internal hernia in 0.2% of cases, mainly through Petersen's defect.[9] 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.

Bowel obstruction[edit]

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. An operation is usually necessary to correct this problem.

Complications of gastric bypass[edit]

Anastomotic leakage[edit]

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 body's natural healing abilities 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 Roux-en-Y gastric bypass and less than 1% in mini gastric bypass. Leaks usually occur at the stomach-intestine connection (gastro-jejunostomy). There is a change in the drain fluid contents from serous (before the leak) to fecal/bilious (after the leak). Usually significant leaks need urgent re-operation. Sometimes a minor leakage can be treated with antibiotics only. It is usually safer to re-operate if an infection cannot be definitely controlled immediately.

Anastomotic stricture[edit]

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.

Anastomotic ulcer[edit]

Ulceration of the anastomosis occurs in 1–16% of patients.[10] Possible causes of such ulcers are:

This condition can be treated with:

Dumping syndrome[edit]

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 intestine, 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 an anxiety attack. The person usually has to lie down, and could be very uncomfortable for 30–45 minutes. Diarrhea may then follow.

Nutritional deficiencies[edit]

Nutritional deficiencies are common after gastric bypass surgery, and are often not recognized. They include:[11]

Nutritional effects[edit]

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 vitamin B12 (cyanocobalamin) supplements are all very important to the post-operative bypass patient.

Total food intake and absorbance rate of food will rapidly decline after gastric bypass surgery, and the number of acid-producing cells lining the stomach increases. Doctors often prescribe acid-lowering medications to counteract the high acidity levels. Many patients then experience a condition known as achlorhydria, where there is not enough acid in stomach. As a result of the low acidity levels, patients can develop an overgrowth of bacteria. A study conducted on 43 post-operative patients revealed that almost all of the patients tested positive for a hydrogen breath test, which indicated an overgrowth of bacteria in the small intestine.[15] Bacterial overgrowth causes the gut ecology to change and induces nausea and vomiting. Recurring nausea and vomiting eventually change the absorbance rate of food, contributing to the vitamin and nutrition deficiencies common in post-operative gastric bypass patients.

Protein nutrition[edit]

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.

Calorie nutrition[edit]

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 60–80% 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[edit]

Vitamins are normally contained in foods and supplements. The amount of food eaten after GBP is severely reduced, and vitamin content is correspondingly lowered. Supplements should therefore be taken to complete minimum daily requirements of all vitamins and minerals. Pre-natal vitamins are sometimes suggested by doctors, as they contain more of certain vitamins than most 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 provide adequate absorption. Some studies suggest that GBP patients who took probiotics after surgery are able to absorb and retain higher amounts of B12 than patients who did not take probiotics after surgery.[citation needed] After a 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.

Minerals[edit]

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 (with 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.

Alcohol metabolism[edit]

Post-operative gastric bypass patients develop a lowered tolerance for alcoholic beverages because their altered digestive tract absorbs alcohol at a faster rate than people who have not undergone the surgery. It also takes a post-operative patient longer to reach sober levels after consuming alcohol. In a study conducted on 36 post-operative patients and a control group of 36 subjects (who had not undergone surgery), each subject drank a 5 oz. glass of red wine and had the alcohol in their breath measured to evaluate alcohol metabolism. The gastric bypass group had an average peak alcohol breath level at 0.08%, whereas 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.[16]

Pica[edit]

There have been reported cases in which pica recurs after gastric bypass in patients with a pre-operative history of the disorder, which are possibly due to iron deficiency. Pica is a compulsive tendency to eat substances other than normal food. Some examples would be people eating paper, clay, plaster, ashes, or ice. Low levels of iron and hemoglobin are common in patients who have undergone gastric bypass.[17] One study reported on a female post-operative gastric bypass patient who was consuming eight to ten 32 oz. 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. Normal iron blood levels of adult women are 30 to 126 µg/dL and normal hemoglobin levels are 12.1 to 15.1 g/dl. This deficiency in the patient's iron levels may have led to the increase Pica activity. The patient was then given iron supplements that brought her hemoglobin and iron blood levels to normal levels. After one month, the patient's eating diminished to two to three glasses of ice 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.[18]

Results and health benefits of gastric bypass[edit]

Weight loss of 65–80% of excess body weight is typical of most large series of gastric bypass operations reported. The medically more significant effects include a dramatic reduction in comorbid conditions:

A study in a large comparative series of patients showed an 89% reduction in mortality over the five years following surgery, compared to a non-surgically treated group of patients.[citation needed]

Concurrently, most patients are able to enjoy greater participation in family and social activities.

Living with gastric bypass[edit]

Gastric bypass surgery has an emotional and physiological impact on the individual. Many who have undergone the surgery suffer from depression in the following months as a result of a change in the role food plays in their emotional well-being.[23] Strict limitations on the diet can place great emotional strain on the patient. Energy levels in the period following the surgery can be low, both due to the restriction of food intake and negative changes in emotional state.[24] It may take as long as three months for emotional levels to rebound. Muscular weakness in the months following surgery is also 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. Muscle weakness may result in balance problems, difficulty climbing stairs or lifting heavy objects, and increased fatigue following simple physical tasks. Many of these issues 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.[citation needed] The benefits and risks of this surgery are well established; however, the psychological effects are not well understood.

Even if physical activity is increased patients may still harbor long term psychological effects due to excess skin and fat.[citation needed] Often bypass surgery is followed up with "body lifts" of skin and liposuction of fatty deposits. These extra surgeries have their own inherent risks but are even more dangerous when coupled with the typical nutritional deficiences that accompany convalescing gastric bypass patients.[citation needed]

Surgeon accreditation[edit]

The American Society for Metabolic & Bariatric Surgery lists bariatric programs and surgeons in its "Centers of Excellence" network,[25] while the American College of Surgeons accredits providers through its Bariatric Surgery Center Network.[26] 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.[27]

See also[edit]

References[edit]

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  25. ^ Surgical Review Corporation Centers of Excellence
  26. ^ ACS Bariatric Surgery Center Network
  27. ^ IFSO National Councils

The MiniMizer Ring is for use in banded bypass and banded sleeve gastrectomies offering a peri-operative adjustable alternative to the GaBP Fobi ring

External links[edit]