Gastric bypass surgery

What is gastric bypass surgery?

When we swallow, the food and drink passes down the gullet (oesophagus – tube which joins the back of the throat to the stomach). The stomach acts as a store of food just eaten, although acid and some digestive juices in the stomach do start some of the processes of digestion. The stomach then empties slowly, with what we have eaten passing through various parts of our small bowel before continuing into the large bowel. During this journey through our small bowel the food mixes with digestive juices and this is where our body absorbs all the nutrients, calories and fats.

The most common version of this operation is called the Roux-en-Y gastric bypass. It is named after the Swiss surgeon (Roux) who first described it and the Y shape made by the re-routed bowel. A small gastric pouch is made by stapling and dividing off a small part of the stomach just below the gullet (Figure 1). A small opening is then made in the pouch and a Y loop of the small intestine is joined to this opening. This loop is 1.5 metres long. The greater part of the stomach, duodenum (first part of the bowel beyond the stomach) and top part of the small intestine (about 50 cm of small intestine) is joined to the bottom of the Roux loop (Figure 1). It is at this point that the food eaten mixes with the digestive juices allowing digestion to begin. After a gastric bypass, there is usually 2-3 metres of common channel small intestine before the colon is reached.

The gastric bypass is usually performed laparoscopically (by keyhole surgery) and takes 1-2 hours to perform. This typically involves making five small cuts on your tummy, to enable the camera and instruments necessary to perform the operation to be inserted. It is performed under general anaesthetic (you are asleep!) Your post-operative stay is usually 2 days, but you are allowed home when you are able to drink enough fluids, and your pain control is adequate to allow you to mobilise easily.

Figure 1 - Roux-en-Y gastric bypass

How does the gastric bypass work?

The gastric bypass works in a number of ways:

The small gastric pouch can restrict the amount of food you can eat at one sitting, helping you stick to a controlled diet. There is no escaping from this. You need to stay on a healthy, restricted diet to lose weight and keep weight off in the long term. Foodstuffs that are more liquid in consistency, often get through the pouch more easily with less feeling of fullness after eating.
The gastric bypass takes part of the small bowel out of the digestive loop (the small bowel is the part that absorbs or takes in digested food and nutrients). The Roux loop in a sense is acting purely as a pipe without significant digestion or absorption taking place, reducing the length of the bowel for calorie absorption.
Having said that, research has shown that how the body adapts to the presence of a gastric bypass is quite complicated. It is not simply a smaller stomach and shorter bowel. The body produces many hormones (chemicals made by the body that move around organs including the brain) controlling hunger, appetite, food seeking behaviour, exercise behaviour, and other processes linked to energy balance, such as temperature control, metabolic rate.
If you take a lot of people who have had a gastric bypass, the average weight loss is around 70 % of their excess body weight at five years. (Excess body weight is the difference between their actual weight and their ideal weight). Much of this weight will be lost in the first year, but this also varies between people. Remember average is the half way point, half of people will lose more than 70 % of excess body weight, but that also means half will lose less than that. All patients have their ‘target’ weight, but we gain most health improvements from the first stone of weight that we lose and least benefit, although still some benefit, from the last stone in weight that we lose.

Alternatives to the gastric bypass

It would be best to avoid surgery altogether. Making major lifestyle changes to include dieting, healthy food choices and regular movement and exercise will be required after surgery anyway, and many people find that these things alone help them to lose weight without the need to undergo an operation. Others find that the addition of prescribed weight loss drugs provides all the help they need to get their weight down.

If these things don't help, or the effects don't last, it is reasonable to consider weight loss surgery, at which point the major consideration becomes which operation is best for you. Apart from the gastric bypass, current surgical options include the gastric sleeve, gastric band and the gastric balloon.

Benefits of the gastric bypass

Gastric bypass surgery is a relatively safe operation. However, it involves more major surgery than the gastric band or gastric sleeve, with a greater risk of complications. The gastric bypass however is a more reliable weight loss operation. Furthermore, while attention to your diet is important, in some people if you do eat more than you should, this can lead to ‘dumping’. Dumping is where the excess foodstuffs, especially sugar based foods, acts like a laxative and leads to diarrhoea. Persistent overeating though will enlarge the gastric pouch, allowing you to store larger meals, and this can sometimes be the reason for subsequent weight gain.

For most patients who have gastric bypass surgery, the benefits in terms of losing weight are much greater than the risks. In particular, most patients with recently-diagnosed diabetes mellitus (less than 5 years) can be cured of their diabetes with a gastric bypass, and this may all happen within a few days of surgery, well before any significant weight loss has occurred.

Risks of the gastric bypass

Performing a gastric bypass involves an operation. There are thus the risks of the general anaesthetic, and there are the risks of the operation itself.

Modern anaesthetics are very safe, but being overweight does add a slight risk when having a general anaesthetic, and if, for example, you have other illnesses such as diabetes or heart disease then the anaesthetic risk is a little higher again. At Weight Loss Surgery Scotland you will undergo a careful preoperative assessment where any potential risk factors are identified. Other specialists can be called in for opinions if required, and the consultant anaesthetists will meet you to discuss your anaesthetic beforehand. The hospital operating and anaesthetic facilities are state-of-the-art and all precautions are taken to reduce the risks.

A gastric bypass is like a plumbing job. The pipework of your intestines is cut and rejoined in several places. Like any plumbing job, these joins can leak. This is a serious complication and often requires urgent, further surgery to correct. Damage to your stomach, intestines or liver is possible during the operation and bleeding or perforation of the stomach or bowels may be the result. Bleeding is not usually too much of a problem as long as it is recognised and fixed promptly. The need for a blood transfusion as a result of a gastric bypass is highly unlikely. Similarly, perforation of the stomach or bowels is not usually of major concern if the perforation is recognised and fixed.

The other main risk of surgery is blood clots. This can happen to anyone having any operation, not just a weight loss surgery operation. Every attempt is made by the Weight Loss Surgery Scotland team to minimise this risk around the time of your operation. We do this by using injections to thin the blood, as well as special stockings and calf pumps during the procedure. Getting you up out of bed moving as quickly as possible after the operation is also important to keep the blood circulating in your legs.

Long term complications of the gastric bypass operation

Pouch dilation
If you regularly overeat into the small gastric pouch, it will stretch and get bigger. This will mean you can eat bigger meals and thus lose less weight, or indeed put weight on. Sometimes, if picked up early, more careful eating behaviour can reverse this dilation.

Internal herniation
The operation rearranges your bowel anatomy and this can cause potential sites for abnormal rotation and internal herniation of the bowel. If you develop severe crampy abdominal pain, or the feeling of abdominal distension (the feeling of being blown up like a balloon), and feel unwell with it, you should seek urgent medical attention. A CT scan is often required to help with this diagnosis.

Vitamin and other nutrient deficiencies
Because of the malabsorption component of this operation, you may not absorb sufficient minerals and nutrients from your food for your body's needs. Deficiencies can generally be prevented by keeping your protein intake up, and taking a daily multivitamin supplement for life.

Gallstones
Gallstones are common in the UK. Patients who lose weight are more likely to develop gallstones. In many patients, these gallstones cause no symptoms, and you are not aware you have them. But sometimes they can cause inflammation in the gallbladder. If this happens, you may require an operation to remove your gallbladder along with the stones at some point after your gastric bypass if they cause symptoms.

Is my gastric bypass for life?

You should consider the gastric bypass as an operation for life. However, occasionally the operation is required to be reversed; although the need for this is very rare. This is a difficult operation and often requires open surgery through a large incision to reverse. The main reason for reversal is vitamin or other nutrient deficiencies that cannot be corrected by medication and nutrient supplements in diet and tablet form.

How you and food interact remains a key part of you both losing weight and keeping your weight steady in the long term. There is no bariatric surgery that allows you to eat what you want and lose weight. Establishing good eating patterns and making right food decisions is important for you to get the most from your surgery. That is why follow up after your surgery is vital. A one year follow up with our team is included with our inclusive care price. You should make use of these appointments to help you get the best result from your gastric bypass.