SGastric Bypass (GBP) refers to a group of similar operative procedures used to treat morbid obesity, a condition which arises from severe accumulation of excess weight as fatty tissue, and the resultant health problems ("co-morbidities") which occur. Bariatric surgery is the surgical treatment of morbid obesity, and includes the gastric bypass procedures as one of several classes of operations.

A gastric bypass consists of a division of the stomach into a small upper pouch and a much larger, lower "remnant" pouch, accompanied by re-arrangement of the small intestines to permit both pouches to remain connected. The manner in which the intestines are reconnected gives rise to several variations of the procedure. The operation leads to a marked reduction in the functional volume of the stomach, accompanied by an altered physiological and psychological response to food. Weight loss is typically dramatic, and co-morbidities are markedly reduced.

The most common form of gastric bypass surgery is Roux-en-Y gastric bypass surgery. Here, a small stomach pouch is created with a stapler device, and connected to the distal small intestine. The upper part of the small intestine is then reattached in a Y-shaped configuration.

The gastric bypass is the most commonly performed operation for weight loss in the United States. In the U.S, approximately 140,000 gastric bypass procedures were performed in 2005, an amount dwarfing the number of Lap-Band®, duodenal switch and vertical banded gastroplasty procedures done. Furthermore, since the gastric bypass has been performed for almost 50 years, surgeons have become very comfortable with the understanding of the risks and benefits of the procedure. By sheer volume of cases combined with the volume of scientific research, the gastric bypass has become the "gold standard" operation for weight loss in the U.S. An emerging factor in the success of gastric bypass surgery is following an established gastric bypass diet after surgery

Co-Morbid Conditions

Obesity becomes life-threatening when it causes health problems, which are a consequence of its mechanical or metabolic effects. These co-morbidities may in turn lead to severe deterioration of health, shortened life expectancy, and impaired enjoyment of lifestyle.

Major co-morbidities include:

Atherosclerotic Cardiovascular Disease (ASCVD). Obesity is associated with the occurrence of hypercholesterolemia, hypertriglyceridemia, and is a factor in the occurrence of atherosclerosis, the deposition of fats within the walls of the blood vessels. This leads to conditions such as coronary artery disease, congestive heart failure, and "hardening of the arteries". This group of conditions is a leading cause of death in the United States.

Diabetes Mellitus Type 2 Also called adult-onset diabetes, this form of diabetes occurs mostly in middle and older ages, and is up to 40 times as likely in those who are severely overweight. It is associated with ASCVD, kidney failure, blindness, nerve damage, and amputations of the extremities, and is also a leading overall cause of death in the United States. Dysmetabolic Syndrome X, a pre-diabetic condition frequently associated with obesity, is accompanied by elevated levels of insulin in the blood, and a high incidence of early development of coronary heart disease.

Essential Hypertension or "high blood pressure", is much more common in obese individuals. It can lead to early development of ASCVD, as well as to kidney disease. Weight loss is considered to be an important feature of treatment.

Obstructive Sleep Apnea (OSA) Persons with this condition tend to suffer from airway obstruction when asleep, as the muscles relax and the weight and bulk of tissues collapses the throat passages. An observer notices loud snoring, frequent periods when breathing ceases (apneas), and episodes of restlessness and partial awakening. The afflicted patient is often unaware of the nature of the problem, but may notice frequent awakening at night, dry mouth, a sense of having slept poorly, daytime drowsiness and fatigue, or inappropriate sleeping (such as at work, in meetings, or while driving). This condition has a significant associated mortality.

Gastroesophageal Reflux Disease (GERD) is characterized by regurgitation (reflux) of acid and gastric contents into the esophagus, and sometimes into the back of the throat. Gastric acid and bile are very corrosive to the lining membrane of the esophagus, and cause it to become inflamed (esophagitis) and sometimes scarred (esophageal stricture). Reflux which occurs while sleeping can lead to sudden coughing and choking at night, a burning sensation in the throat (pyrosis), and inhalation of acid and stomach contents into the lungs, with the risk of hoarseness, bronchitis, pneumonia, lung abscess and lung scarring. GERD is often associated with development of asthma, and causation of asthmatic attacks, and may also be aggravated by OSA.

Gall-Bladder Disease is much more likely in obese individuals, being associated with formation of gallstones, usually composed of crystallized cholesterol, within the gallbladder. Although readily treatable by removal of the gallbladder (cholecystectomy), it may lead to life-threatening problems such as obstruction of the ducts from the liver, jaundice, and inflammation of the pancreas (gallstone pancreatitis).

Liver Disease is present in some degree in 90% of persons who undergo bariatric surgery, usually a manifestation of the metabolic effects of obesity on the liver. This may take the form of large fat globules within the liver cells (steatosis), chronic inflammation of the liver (steatohepatitis), and in a few instances, cirrhosis of the liver. The latter condition may lead to liver failure and the need for a liver transplant.

Venous Thromboembolic Disease (VTE) affects the legs, and causes swelling, thickening and discoloration of the skin, and ulceration of the skin. This condition begins with damage to the veins of the legs, associated with formation of blood clots (thrombophlebitis), often associated with an injury, a pregnancy (even use of birth-control pills or hormones), or a surgical operation. When a newly formed blood clot breaks loose, and floats through the veins to the heart and lungs, it is called a pulmonary embolus. This may sometimes be fatal within minutes. More commonly, the blood clot remains in place locally, and heals by becoming a scar, which permanently damages the vein. Once damaged, the veins cannot fully function to return blood to the heart, and increased venous pressure in the legs causes swelling, impaired circulation in the skin, and sometimes skin breakdown. Obesity is a major risk factor in development of VTE, and may also aggravate the increased venous pressure in the legs.

Degenerative Disc Disease is a progressive "wearing-out" of the cartilage disks between the vertebral bones of the spine. It occurs more often and earlier in life in obese persons, due to the markedly increased mechanical stress on the disks from the extra weight. Its most common sign is chronic low back pain, which may be disabling. This condition is also associated with sciatica, lumbar spondylosis, and spinal stenosis.

Degenerative Disease of the Weight-Bearing Joints, or osteoarthritis, affecting the hips, knees, ankles and feet, occurs earlier in life, and in greater degree, in obese individuals, due to the mechanical stresses of excess weight. Joint pain, loss of mobility, and joint replacement surgery are much more likely in obese persons.

Surgical Indications

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 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, a Consensus Panel of physicians was sponsored by the National Institutes of Health, and its 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 should undergo comprehensive pre-operative evaluation, and have multi-disciplinary support, for optimum outcome.

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.

Surgical Techniques

The gastric bypass, in its various forms, accounts for a large majority of the bariatric surgical procedures performed. It is estimated that 140,000 such operations were performed in the United States in 2005. 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.