Along with a traditional Roux-en-Y operation, other variations are options for patients suffering from morbid obesity. Staples can be applied to the stomach to reduce its effective volume, so that the patient feels satiated with a lower food volume. An advantage to this type of surgery is that it takes less effort to reverse.
A Roux-en-Y operation requires severing the upper and lower portions of the stomach to create a bypass. Normally food enters follows the following path:
esophagus >>> fundus of stomach >>> stomach >>> pyloric sphincter >>> duodenum >>> jejunum >>> ileum >>> large intestine.
after the Roux-en-Y, food will usually follow this modified path:
esophagus >>> fundus of stomach >>> jejunum >>> ileum >>> large intestine.
bypassing the stomach and duodenum serve two important purposes when trying to reduce a patient's weight. First, the effective volume of the stomach is reduced, so its fills sooner. The fundus also contains barorecptors that signal a patient when they are satiated. The baroreceptors are positioned at the top of the stomach, so that they activate when the stomach fills. Secondly, food will bypass the duodenum, which absorbs the most nutrients while food normally passes through the GI tract. This double-edged attack reduces both the total amount of food consumed, and the amount of nutrients absorbed.
While the Roux-en-Y procedure is effective, it is difficult if not impossible to reverse and requires the patient to live with the condition for the rest of their lives. It can also have unpleasant side effects from the reduced absorption of nutrients.
A relatively new technology are implants that alter effective stomach volume or change the way food is digested within the GI tract. These do not require restructuring of the GI tract, and can be removed after the patient has reached a healthy weight.
One category of implants reduce the stomach by squeezing it into a smaller volume. Known as "lap-band surgery," this type of implant surrounds the stomach with an inelastic cord. Some versions use an inflatable tube, something like an inner tube in a car tire. A computer-controlled pump can inflate or deflate the band to varying degrees, to adjust the effective stomach volume.
Another category of implants produce an artificial feeling of satiety by expanding within the stomach. Wire scaffolding, somewhat like expandable intravascular structures used to counteract atherosclerosis in cardiac vessels is placed in the stomach and holds it open to simulate the presence of food.
Another type reduces the absorption of nutrients from food passing through the GI tract by physically isolating it as it travels through. Frequently, a tube is placed within the GI tract starting at the gastroesophogeal junction, passes through the stomach and downstream into the small intestine. The tube can be permeable, to allow digestive secretions from the stomach to enter the lumen of the implant but not exit until they reach a downstream opening. This way, food travels along its natural pathway but does not interact with enzymes to extract nutrients.
In a reverse of this method, some implants isolate digestive secretions such as bile by coupling to the ampulla of vader and isolate them from food in the small intestine until they reach a downstream segment or the large intestine. this way, nutrients do not get a chance to be absorbed by the more effective duodenum, and leave the body.
One major advantage to these types of implants is that the surgery is reversible. To return a patient's GI tract to its previous condition, a surgeon can detach the implant at its anchor points, and remove it endoscopically. An incision in the abdomen is not required, since all the manipulations can be performed with an endoscope through the esophagus. Some implants are made of biodegradable materials, and are designed to pass through the GI tract after a set period of time.
While gastrointestinal bypass surgery and implants offer a solution to morbid obesity, they are only used as a last attempt when changes in diet and exercise have failed.