Gastric Bypass (Malabsorptive) Surgery

(Types of bariatric surgical procedures which involve gastric bypass to some degree include: Roux-en-Y gastric bypass [RYGBP], biliopancreatic diversion [BPD], biliopancreatic diversion and duodenal switch, [BPD-DS])

Procedure overview

What is gastric bypass surgery?

Gastric bypass surgery, a type of bariatric surgery (weight loss surgery), is a procedure that alters the process of digestion. Bariatric surgery is the only option today that effectively treats morbid obesity in people for whom more conservative measures such as diet, exercise, and medication have not been effective.

Bariatric surgery works in one of three ways:

  • Restriction, or limiting the amount of food intake by reducing the size of the stomach

  • Malabsorption, or limiting the absorption of foods in the intestinal tract by "bypassing" a portion of the small intestine to varying degrees

  • Combination of both restriction and malabsorption

Currently, in the U.S., five types of bariatric surgical procedures are generally used to obtain continued weight loss. The purely restrictive bariatric surgeries are called gastric banding or gastric stapling. The biliopancreatic diversion with or without duodenal switch (BPD-DS) is mainly a malabsorptive bariatric surgery. Gastric bypass surgery is a combination of both restriction and malabsorption.

Types of bariatric surgical procedures that involve gastric bypass to some degree include:

Illustration of a roux-en-Y gastric bypass procedure

  • Roux-en-Y gastric bypass (RYGBP). Roux-en-Y gastric bypass is the most commonly performed bariatric procedure. It works by combining both restrictive and malabsorptive elements. The restrictive element can be achieved by stapling the stomach into two sections. The top section becomes a small pouch that serves as the "new" stomach. The small size of this newly formed stomach is so reduced that it "restricts" or limits the amount of food intake. It also provides a feeling of fullness and satisfaction with smaller portions of food. The lower section of the stomach no longer receives, stores, and mixes food but remains functional by continuing to secrete digestive juices.

    The malabsorptive element in gastric bypass is achieved by surgically dividing the small intestine in a certain area. Once divided, the lower part of the intestine (jejunum)is pulled up to directly connect to the small pouch or "new" stomach. The other end of this divided intestine is surgically sewn back at a specific point further down the small intestine. The shape of the intestine now somewhat resembles a "Y." As a result, when food is eaten, it enters the "new" stomach, then travels into the jejunum, first "bypassing" the upper part of the intestine. The effect of bypassing the upper portion of the intestine decreases the amount of calories and nutrients that are absorbed into the body. This surgery can result in two-thirds of excess weight loss within two years. Because of the malabsorption, this increases the risk of nutritional deficiencies. Therefore, after surgery, it will be important to follow the physician's guidelines for nutritional supplementation.

    The Roux-en-Y gastric bypass may be performed with a laparoscope rather than through an open incision in some patients. This procedure uses several small incisions and three or more laparoscopes—small thin tubes with video cameras attached—to visualize the inside of the abdomen during the operation. The surgeon performs the surgery while looking at a TV monitor. People with a Body Mass Index (BMI) of 60 or more or those who have already had some type of abdominal surgery are usually not considered for this technique. A laparoscopic method allows the physician to make a series of much smaller incisions. Laparoscopic gastric bypass usually reduces the length of hospital stay, the amount of scarring, and results in quicker recovery than an open procedure.

  • Biliopancreatic diversion (BPD). A biliopancreatic diversion is primarily malabsorptive, and is a more complicated procedure than the Roux-en-Y gastric bypass. In this procedure a part of the lower stomach is removed. The part of stomach that is left is connected directly to the last part of the small intestine (jejunum). As food is digested, it completely bypasses a larger section of the small intestine than in the Roux-en-Y gastric bypass. This surgery may result in a greater degree of malabsorption than the Roux-en-Y, resulting in greater nutritional deficiencies. It is not as commonly performed.
    A variation of the biliopancreatic diversion is a procedure called the duodenal switch (BPD-DS). This adaptation retains the part of the stomach that includes the valve that controls the release of food into the small intestine. This helps to prevent the "dumping syndrome" which can result in vomiting or diarrhea. A small part of the upper intestine (duodenum) is also retained.

What are the different parts of the digestive system?

The digestive tract

Digestion is the process by which food and liquid are broken down into smaller parts so that the body can use them to build and nourish cells. Digestion begins in the mouth, where food and liquids are taken in, and is completed in the small intestine. The digestive tract is a series of hollow organs joined in a long, twisting tube from the mouth to the anus.

The stomach is where the three mechanical tasks of storing, mixing, and emptying occur. Normally, this is what happens:

  • First, the stomach stores the swallowed food and liquid, which requires the muscle of the upper part of the stomach to relax and accept large volumes of swallowed material.

  • Second, the lower part of the stomach mixes up the food, liquid, and digestive juices produced by the stomach by muscle action.

  • Third, the stomach empties the contents into the small intestine.

The food is then digested in the small intestine and dissolved by the juices from the pancreas, liver, and intestine, and the contents of the intestine are mixed and pushed forward to allow further digestion.

Malabsorptive procedures alter this process in different ways depending on the type of procedure.

Reasons for the procedure

Bariatric surgery is performed because it is currently the best treatment option for producing lasting weight loss in obese patients for whom nonsurgical methods of weight loss have not been effective.

Potential candidates for bariatric surgery include:

  • People with a body mass index (BMI) greater than 40

  • Men who are 100 pounds over their ideal body weight or women who are 80 pounds over their ideal body weight

  • People with a BMI of 35 or more who have another condition such as obesity-related type 2 diabetes, sleep apnea, or heart disease

Because the surgery can have serious side effects, the long-term health benefits must be considered and found greater than the risk. Despite the fact that some surgical techniques can be done laparoscopically with reduced risk, all bariatric surgery is considered to be major surgery.

Although not all risks with each procedure are fully known, bariatric surgery does help many people to reduce or eliminate some health-related obesity problems. It may help to:

  • Lower blood sugar

  • Lower blood pressure

  • Reduce or eliminate sleep apnea

  • Decrease the workload of the heart

  • Lower cholesterol levels

Surgery for weight loss is not a universal remedy, but these procedures can be highly effective in people who are motivated after surgery to follow their physician's guidelines for nutrition and exercise and to take nutritional supplements.

There may be other reasons for your physician to recommend a gastric bypass procedure.

Risks of the procedure

As with any surgical procedure, complications may occur. Some possible complications include, but are not limited to, the following:

  • Infection

  • Blood clots

  • Pneumonia

  • Bleeding ulcer

  • Development of gallstones

  • Gastrointestinal hemorrhage

With the Roux-en-Y gastric bypass procedure, and particularly the biliopancreatic diversion procedure, malabsorptive symptoms may be more serious with an increased risk of anemia and loss of fat-soluble vitamins (vitamins A, D, E, and K). Adequate amounts of iron, calcium, and vitamin B12 may not be absorbed. This can cause metabolic bone disease and osteoporosis.

Stomal stenosis occurs when there is a stricture (tightening) of the opening between the stomach and intestine after a Roux-en-Y procedure. When this occurs, vomiting after eating and sometimes after drinking may occur. Stomal stenosis can be treated easily but should be treated immediately.

"Dumping syndrome" is also more likely to occur with these procedures because the food in the stomach moves to the intestines quickly. Symptoms include nausea, sweating, fainting, light-headedness, tachycardia, palpitations, desire to lie down, loss of concentration, weakness, and/or diarrhea. Almost 85 percent of patients who have gastric bypass surgery will experience this syndrome after the procedure.

There is a risk that additional surgery may be necessary because of complications, including gallstones.

One of the most serious complications of gastric bypass is a stomach leak that can cause peritonitis to develop. Peritonitis is an inflammation of the peritoneum, the smooth membrane that lines the cavity of the abdomen.

There may be other risks depending upon your specific medical condition. Be sure to discuss any concerns with your physician prior to the procedure.

Before the procedure

  • Your physician will explain the procedure to you and offer you the opportunity to ask any questions that you might have about the procedure.

  • You will be asked to sign a consent form that gives your physician permission to perform the procedure. Read the form carefully and ask questions if something is unclear.

  • In addition to a complete medical history, your physician may perform a complete physical examination to ensure you are in good health before undergoing the procedure. You may undergo blood tests or other diagnostic tests.

  • You will be asked to fast for eight hours before the procedure, generally after midnight.

  • If you are pregnant or suspect that you are pregnant, you should notify your physician.

  • Notify your physician if you are sensitive to or are allergic to any medications, latex, iodine, tape, or anesthetic agents (local and general).

  • Notify your physician of all medications (prescription and over-the-counter) and herbal supplements that you are taking.

  • Notify your physician if you have a history of bleeding disorders or if you are taking any anticoagulant (blood-thinning) medications, aspirin, ibuprofen, naprosyn, or other medications that affect blood clotting. It may be necessary for you to stop some of these medications prior to the procedure.

  • You may be asked to begin exercising and alter your diet several weeks before surgery.

  • If you are a woman of child-bearing age, you may receive birth control counseling so that you do not become pregnant in your first year after surgery due to the risk to the fetus from rapid weight loss.

  • You may receive a sedative prior to the procedure to help you relax.

  • Based upon your medical condition, your physician may request other specific preparation.

During the procedure

Gastric bypass surgery requires a stay in the hospital. Procedures may vary depending on which type of procedure is performed and your physician's practices.

Gastric bypass is generally performed while you are asleep under general anesthesia.

Generally, gastric bypass surgery follows this process:

  1. You will be asked to remove clothing and will be given a gown to wear.

  2. An intravenous (IV) line will be started in your arm or hand.

  3. You will be positioned lying on your back on the operating table.

  4. A urinary catheter may be inserted into your bladder.

  5. If there is excessive hair at the surgical site, it may be clipped off.

  6. The anesthesiologist will continuously monitor your heart rate, blood pressure, breathing, and blood oxygen level during the surgery.

  7. The skin over the surgical site will be cleansed with an antiseptic solution.

  8. For an open procedure, the physician will make a single large incision in the abdominal area. For a laparoscopic procedure, a series of small incisions will be made on the abdomen. Carbon dioxide gas will be introduced into the abdomen to inflate the abdominal cavity so that the stomach and other structures can easily be visualized with the laparoscope.

  9. For an open procedure, the abdominal muscles will be separated and the abdominal cavity will be opened. For a laparoscopic procedure, the physician will insert the laparoscope and other small instruments.

  10. For a Roux-en-Y gastric bypass, the physician will staple the stomach across the top to create a new small pouch for a stomach. The rest of the stomach will be separated from the new pouch and closed off by the staples; however, the remaining stomach will continue to produce digestive juices that will be used in digestion. A portion of the small intestine will be shaped like a "Y" and connected to the pouch.

  11. For a biliopancreatic diversion, a large part of the lower stomach will be removed. The small part of stomach that is left is then connected directly to the last part of the small intestine. For a duodenal switch procedure, the physician will retain more of the stomach, including the valve that controls the release of food into the small intestine. A small part of the duodenum will also be kept.

  12. A drain may be placed in the incision site to remove fluid.

  13. The incision will be closed with sutures or surgical staples.

  14. A sterile bandage/dressing will be applied.

After the procedure

In the hospital

After the procedure, you will be taken to the recovery room for observation. Once your blood pressure, pulse, and breathing are stable and you are alert, you will be taken to your hospital room. Weight loss surgery usually requires an in-hospital stay of several days.

You may receive pain medication as needed, either by a nurse or by administering it yourself through a device connected to your intravenous line.

You will be encouraged to move around as tolerated while you are in bed, and then to get out of bed and walk around as your strength improves. This is very important, as it helps to prevent blood clots from forming.

At first you will receive fluids through an IV. After a day or two you will be given liquids, such as broth or clear juice, to drink. As you are able to tolerate liquids, you will be given thicker liquids, such as pudding, milk, or cream soup, followed by foods that you do not have to chew, such as hot cereal or pureed foods. Your physician will instruct you about how long to eat pureed foods after surgery. By one month after your procedure, you may be eating solid foods.

You will be instructed about taking nutritional supplements to replace the nutrients lost due to the reconstruction of the digestive tract.

Before you are discharged from the hospital, arrangements will be made for a follow-up visit with your physician.

At home

Once you are home, it will be important to keep the surgical area clean and dry. Your physician will give you specific bathing instructions. The sutures or surgical staples will be removed during a follow-up visit.

The incision and abdominal muscles may ache, especially with deep breathing, coughing, and exertion. Take a pain reliever for soreness as recommended by your physician. Aspirin or certain other pain medications may increase the chance of bleeding. Be sure to take only recommended medications.

You should continue the breathing exercises used in the hospital.

You should gradually increase your physical activity as tolerated. It may take several weeks to return to your previous levels of stamina.

You may be instructed to avoid lifting heavy items for several months in order to prevent strain on your abdominal muscles and surgical incision.

Weight loss surgery can be emotionally difficult because you will be adjusting to new dietary habits and a body in the process of change. You may feel especially tired during the first month following surgery. Exercise and attending a support group may be helpful at this time.

Notify your physician to report any of the following:

  • Fever and/or chills

  • Redness, swelling, or bleeding or other drainage from the incision site

  • Increased pain around the incision site

Following gastric bypass surgery, your physician may give you additional or alternate instructions, depending on your particular situation.

Online resources

The content provided here is for informational purposes only, and was not designed to diagnose or treat a health problem or disease, or replace the professional medical advice you receive from your physician. Please consult your physician with any questions or concerns you may have regarding your condition.

This page contains links to other websites with information about this procedure and related health conditions. We hope you find these sites helpful, but please remember we do not control or endorse the information presented on these websites, nor do these sites endorse the information contained here.

American Society for Metabolic and Bariatric Surgery

Medem - Medical Library

National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)

Office of the Surgeon General of the United States - Overweight and Obesity