Gastric bypass surgery
Gastric bypass surgery refers to a technique in which the stomach is divided into a small upper pouch and a much larger lower "remnant" pouch, where the small intestine is rearranged to connect to both. Surgeons have developed several different ways to reconnect the intestine, thus leading to several different gastric bypass procedures. 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 severe obesity, type 2 diabetes, hypertension, obstructive sleep apnea, and other comorbid conditions. Bariatric surgery is the term encompassing all of the surgical treatments for severe 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%. As with all surgery, complications may occur. A study from 2005 to 2006 revealed that 15% of patients experienced complications as a result of gastric bypass, and 0.5% of patients died within six months of surgery due to complications. A meta-analysis of 174,772 participants published in The Lancet in 2021 found that bariatric surgery was associated with 59% and 30% reduction in all-cause mortality among obese adults with or without type 2 diabetes respectively. This meta-analysis also found that median life-expectancy was 9.3 years longer for obese adults with diabetes who received bariatric surgery as compared to routine care, whereas the life expectancy gain was 5.1 years longer for obese adults without diabetes.
Uses
Gastric bypass is indicated for the surgical treatment of severe 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 has comorbid conditions that are either life-threatening or serious impairment to the quality of life.Before 1991, clinicians interpreted serious obesity as weighing at least 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 standard for consideration of surgical treatment, the body mass index. The BMI is defined as the body weight, divided by the square of the height. The result is expressed as a number in kilograms per square meter. In healthy adults, BMI ranges from 18.5 to 24.9, with a BMI above 30 considered obese, and a BMI less than 18.5 considered underweight.
The Consensus Panel of the National Institutes of Health recommended the following criteria for consideration of bariatric surgery, including gastric bypass procedures:
- people who have a BMI of 40 or higher
- people with a BMI of 35 or higher with one or more related comorbid conditions
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 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:
- bariatric surgery is the most effective treatment for severe obesity
- gastric bypass is one of four types of operations for severe obesity
- laparoscopic surgery is equally effective and as safe as open surgery
- patients should undergo comprehensive preoperative evaluation and have multi-disciplinary support for optimum outcome
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.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 to specialized operating instruments. The surgeon views the 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 and reported on in case studies between 1993 and 1994, is regarded as one of the most difficult procedures to perform by limited access techniques. The 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
The gastric bypass procedure consists of:- Creation of a small, 15–30 mL pouch from the upper stomach, accompanied by bypass of the remaining stomach. This restricts the volume of food that can be eaten. The stomach may simply be partitioned, or it may be divided into two separate/separated parts. Total division is usually advocated to reduce the possibility that the two parts of the stomach will heal back together and negate the operation.
- Re-construction of the GI tract to enable drainage of both segments of the stomach. The particular technique used for this reconstruction produces several variants of the operation, differing in the lengths of the small intestine used, the degree to which food absorption is affected, and the likelihood of adverse nutritional effects. Usually, a segment of the small bowel is brought up to the proximal remains of the stomach.
Variations
Gastric bypass, Roux-en-Y (RYGB, proximal)
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 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 end of the small intestine. The Roux limb is constructed using of the small intestine, preserving the rest of it from absorbing nutrients. The patient will experience a very rapid onset of the stomach feeling full, followed by a growing satiety shortly after the start of a meal.Gastric bypass, Roux-en-Y (RYGB, distal)
The small intestine is normally 20 – 22 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 end of the small intestine, usually from the lower end, causing reduced 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 larger effects on nutrition are traded for a relatively modest increase in total weight loss.Mini-gastric bypass (MGB)
The mini-gastric bypass procedure was first developed by Robert Rutledge from the US 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. A loop of the small gut is brought up and hooked to this tube at about 180 cm from the start of the intestine.Numerous studies show that the loop reconstruction 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.