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Gastric bypass: function, procedure, risks

by Josephine Andrews
Published: Last Updated on 310 views

Gastric bypass refers to a surgical procedure that bypasses and thus eliminates a large part of the stomach and small intestine in obese people. Only a small part of the stomach remains, so the patients feel a feeling of satiety even after eating very small amounts. The result is rapid and significant weight loss. Find out everything about the operation, its advantages and risks here!

What is a gastric bypass?

The gastric bypass (more precisely: Roux-en-Y gastric bypass) is a very frequently used method of obesity surgery with the aim of weight reduction. The name is derived from the name of the Swiss surgeon “Roux”, who developed the basic technique of the procedure. The “Y” stands for the shape in which the sections of intestine are connected to one another, namely a Y-shape.

The success of the gastric bypass is based on two principles:

  • a stomach reduction to reduce the amount of food (restriction)
  • the elimination of the important upper part of the small intestine ( duodenum ), whereby the digestive juices, which are important for the breakdown of food, only mix with the chyme later (poorer nutrient absorption = malabsorption)

Weight loss after a gastric bypass is very effective and reliable, but it is associated with some lifelong limitations: Patients with a Reoux-en-Y bypass can only tolerate very small meals because the residual stomach (“gastric pouch”) left after the operation only has a very small volume. The poorer nutrient utilization also means that patients should take certain dietary supplements and vitamins (particularly vitamin B12 , trace elements and protein supplements) for the rest of their lives in order not to suffer from any deficiency symptoms. Since some of the nutrients remain undigested, increased fermentation processes can occur in the large intestine .However, once the weight has been successfully reduced, the operation can hardly be reversed.

Preparation for gastric bypass

Before the operation, pathological changes in the stomach must be ruled out. For this purpose, the stomach is examined, for example, for diseases such as inflammation of the gastric mucosa or stomach ulcers and for possible bacterial colonization with the bacterium “Helicobacter pylori”, which can cause stomach ulcers. In addition to a gastroscopy and the examination of the gastric juice, an ultrasound of the upper abdomen is also used, with which gallstones can be detected. These should be removed as part of the gastric bypass surgery as they can lead to inflammation of the gallbladder and bile duct.

Process of gastric bypass surgery

Depending on the patient, gastric bypass surgery takes around 90 to 150 minutes and is performed under general anesthesia. The procedure usually requires a hospital stay of about one day before the operation (preparation for the operation and anesthesia) plus five to seven days afterwards. After gastric bypass surgery, you are unable to work for about three weeks.

Today, the gastric bypass is almost exclusively performed as a so-called minimally invasive operation. This technique, also known as the “keyhole method”, does not require a large abdominal incision. Instead, the instruments and a small camera are inserted into the abdominal cavity through several skin incisions of about two centimeters each. Overall, minimally invasive operations have a lower surgical risk than open operations and are therefore particularly suitable for obese patients who are already more at risk of complications during and after the operation.

Gastric bypass surgery consists of several stages:

  1. After induction of general anesthesia, the surgeon inserts the instruments and a camera with a light source into the abdominal cavity through several skin incisions. A gas (usually CO2) is then introduced into the abdominal cavity so that the abdominal wall is slightly raised from the organs and the surgeon has more space in the abdomen and a better view of the organs.
  2. First, however, the stomach is severed just below the esophagus using a so-called stapler. The stapler cuts and staples at the same time, so the cut edges are sealed immediately. At the end of the esophagus, only a small residual stomach (the so-called stomach pouch or stomach pocket) remains. It has a volume of less than 50 milliliters. The rest of the stomach remains in the body, but is closed at the upper end and thus “shut down” so to speak.
  3. Next, an incision is made through the small intestine in the area known as the jejunum. The lower end of the cut is now pulled up and sewn to the gastric pouch. The connection is therefore also referred to as a gastrojejunal anastomosis.
  4. Now, further below, the remaining cut end of the jejunum is sewn to the third section of the small intestine (“ ileum ”), creating a “Y” shape ( Y anastomosis ). It is here that the digestive juices from the duodenum ( bile and pancreatic secretion) mix with the chyme.

Who is gastric bypass suitable for?

The gastric bypass is suitable for people with a body mass index (BMI) over 40 kg/m² ( obesity grade III or obesity permagna ). In any case, the prerequisite for gastric bypass surgery is that all non-surgical measures have not shown sufficient success even after six to twelve months. These measures include, for example, professional nutritional advice, exercise training and behavioral therapy (multimodal concept for obesity, MMK). For gastric bypass surgery, you should be at least 18 and no more than 65 years old, although the operation is also possible on younger or older people in individual cases.

A gastric bypass is particularly recommended for people whose obesity is mainly due to a heavy consumption of high-calorie food (sweets, fats) and sweet drinks. Because these are now broken down more poorly and can therefore only be utilized by the body to a small extent and stored as body fat. 

If there are already metabolic diseases (metabolic diseases) such as diabetes mellitus, high blood pressure or sleep apnea syndrome due to being overweight, a gastric bypass can make sense from a BMI of 35 kg/m².

For whom a gastric bypass is not suitable

Various physical and mental illnesses speak against obesity surgery such as gastric bypass. Especially after previous operations or malformations on the stomach, stomach ulcers and addictions as well as untreated eating disorders such as “binge eating” or bulimia , a gastric bypass should not be performed. Pregnant women also have to do without a gastric bypass.

Efficacy of Gastric Bypass Surgery

Gastric bypass is a very effective procedure, but only a few patients achieve normal weight (BMI ≤ 25 kg/m²). Studies have shown that with a gastric bypass, a long-term weight loss of about 60 to 70 percent of the excess weight is possible, i.e. the weight that separates the affected person from the normal weight.

In addition to the purely cosmetic effect, weight loss after gastric bypass surgery has a positive effect on the metabolism. For example, in many cases an existing diabetes mellitus is greatly improved and sometimes even cured by the intervention. In many cases, blood sugar levels drop shortly after the operation, even though the patient has not yet lost any significant weight. The reasons for this have not yet been clarified. It is assumed that various hormonal changes are set in motion by the operation (eg in the hormones ghrelin, glucagon, GIP, etc.), which have a favorable effect on the metabolism.

Advantages of gastric bypass over other procedures

Since gastric bypass surgery combines two principles (restriction and malabsorption, see above), the procedure is extremely effective and is particularly effective when the patient’s obesity results from an excessive intake of high-calorie liquid or soft foods. For these so-called “sweet-eaters”, a reduction in the volume of the stomach, such as that achieved with the gastric band, gastric balloon or gastric sleeve, would not be sufficient.

side effects

There are some side effects associated with gastric bypass. How strong these will be varies from person to person and can therefore not be predicted with certainty. The important ones include:

Digestive disorders caused by malabsorption: gas , abdominal pain , nausea, bloating

Iron deficiency and anemia (low blood count): Normally, a large part of the iron that can be utilized from food is absorbed in the duodenum. Since the food is diverted past the duodenum during gastric bypass, iron absorption is more difficult. Iron deficiency is prevented by an additional dose of iron .

Vitamin B12 deficiency (specific form of anemia): Vitamin B12 is absorbed in the last section of the small intestine (terminal ileum). However, this requires an auxiliary substance, the so-called intrinsic factor, which is produced by the stomach. With gastric bypass, however, the food bypasses the stomach and thus less intrinsic factor is formed. Vitamin B12 must therefore be regularly injected into the vein as an injection into the muscle. Vitamin B-12 preparations are also available that are intended to be absorbed directly through the oral mucosa (sublingual application). However, their effectiveness is still being discussed.

Vitamin D deficiency : Why a vitamin D deficiency can occur during a gastric bypass has not yet been clarified. Vitamin D can easily be supplemented with food (orally).

Dumping syndrome : Dumping syndrome (from English to dump = to fall) describes a series of symptoms (dizziness, nausea, sweating or palpitations) which are caused by the immediate (fall-like) emptying of food from the esophagus into the small intestine be able. Because the gastric pouch lacks the lower gastric sphincter (gatekeeper). The chyme in the small intestine attracts water from the surrounding tissue and blood vessels through osmotic forces. This reduces the volume of fluid in the system, which can lead to a drop in blood pressure. Dumping syndrome occurs mainly after very sugary drinks or fatty foods.

Stomach ulcer in the gastric pouch : after gastric bypass surgery, the risk of gastric ulcer (ulcus) in the gastric pouch is increased. Acid-reducing drugs, so-called proton pump inhibitors (PPI), can help, which must be taken permanently if a stomach ulcer develops after gastric bypass surgery.

Loss of muscle mass: Rapid weight loss is often associated with a loss of muscle mass because the body tries to compensate for the relative lack of carbohydrates by breaking down body protein (especially from less stressed muscle cells). Regular physical training can stop this effect. Sports that are easy on the joints, such as light strength training , cycling, swimming or aqua jogging , are particularly advisable for overweight people .

Gastric bypass: risks and complications

A gastric bypass is a major abdominal surgery that greatly alters the normal anatomy of the gastrointestinal system. In principle, the risk of surgery is low, but complications cannot be ruled out, as with all surgical procedures. Non-specific surgical risks include:

  • anesthetic complications
  • Organ and vascular injuries with bleeding
  • Infections of internal and external wounds
  • Leaks in the artificial organ connections (anastomoses) with the risk of peritonitis (peritonitis)
  • Wound healing disorders
  • Disorders of normal gastrointestinal movements (intestinal atonia)

Gastric bypass: nutrition after surgery

People with a gastric bypass must observe the following dietary rules for life in order to avoid digestive problems:

  • Chew food very well
  • eat small portions
  • Avoid high sugar foods and drinks
  • avoid very long-fibered meat or vegetables
  • Take dietary supplements (see above).

Medication after gastric bypass

Some drugs are absorbed by the body after gastric bypass with altered dynamics or in smaller amounts. Dose adjustments by the doctor are therefore necessary for many medications.

Gastric bypass: costs

The costs for a gastric bypass vary considerably depending on the clinic. They are between 6,500 and 15,000 euros. The gastric bypass is currently not a standard benefit of the statutory health insurance companies. This means that the costs of the gastric bypass are only covered upon application and only under certain conditions. Find out more about the necessary requirements before submitting your application!

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