Gastric Bypass

Laparoscopic Gastric Bypass Surgery

What is gastric bypass surgery?

Gastric bypass surgery (most commonly the Roux-en-Y gastric bypass) is a type of weight loss surgery that works by making your stomach smaller and by bypassing part of your digestive system. This means that you can only eat small meals and your body absorbs less food. The operation is done as a laparoscopic (keyhole) surgery procedure while you are asleep under a general anaesthetic. It usually takes one to three hours.

On average, patients tend to lose 60-70% of their excess body weight with this procedure.

About the operation:

Firstly, a small pouch is created at the top of your stomach using staples. A piece of your intestine is then joined to this gastric pouch, which bypasses the rest of your stomach and the upper part of the intestine, where most nutrients and calories are usually absorbed.

The small top part of your stomach fills up quickly with food, giving you a sensation of fullness, and then passes directly to the middle part of your small intestine and through the rest of your digestive system. As the digestive system has effectively been made shorter you should absorb fewer calories.

This procedure can be performed as a standard open surgery, or as a laparoscopic surgery. The laparoscopic approach involves several (5-6) very small incisions and has many advantages over open surgery, including quicker recovery and shorter hospital stays, as well as a significantly reduced risk of wound infection. Patients also report less pain and quicker return to normal activity.

What are the alternatives?

Other alternative surgical options are laparoscopic gastric banding or laparoscopic sleeve gastrectomy.

Surgery is usually recommended only if non-surgical treatments, such as diet, exercise and medicines haven’t worked.

What are the advantages of having a gastric bypass?

  • Greater and faster weight loss than with the gastric band or sleeve gastrectomy.
  • An immediate remission of type 2 diabetes and improvement in blood pressure within days of having the operation in up to 80% of cases.

What are the risks?

Gastric bypass surgery is generally a safe operation.

However, in order for you to make an informed decision and give consent for the operation, you need to be aware of the possible side-effects and the risk of complications of this procedure.


These are the unwanted, but mostly temporary effects of a successful treatment.

You are likely to have some bruising, pain and swelling of the skin around the healing wounds.

You may feel or be sick after eating, especially if you try to eat too much. If you eat too many sugary foods you can get an unpleasant sensation, called "dumping", which may make you feel sick or faint, or give you diarrhoea. You should drink plenty of

fluids until the feelings have passed, and you should also reduce the amount of sugary foods you eat.

In the long term, your restricted diet may cause some shortage of nutrients like iron, calcium and vitamins, so you may need to take multivitamin/mineral tablets indefinitely.


This is when problems occur during or after the operation.

Most people will not experience any serious complications from this surgery.

As with any operation, there are risks associated with having a general anaesthetic. The possible complications include an unexpected reaction to the anaesthetic, excessive bleeding or developing a blood clot, usually in a vein in the leg (deep vein thrombosis, DVT) or in the lungs (pulmonary emboli, PE). The risks increase for people who already have other medical conditions, such as heart disease or high blood pressure.

Some of the complications you may get after a gastric bypass operation are listed here:

  • Infection - antibiotics are usually given during surgery to prevent infection.
  • Damage to other organs in your abdomen - you may need further surgery to repair any damage.
  • Anastomotic leak (join) - the point where your intestine is re-joined to your stomach pouch could leak in the first few days and you may need further surgery to repair this.
  • Anastomotic stricture or ulceration (join) – the point where your intestine is re-joined to your stomach pouch could narrow or form ulcers after surgery and you may need endoscopy with or without dilatation or further surgery to fix it.
  • Internal herniation and adhesion problems – you may need further surgery for it.
  • Gallstones - there is a risk you may develop gallstones if you lose weight quickly. These can be painful and you may need surgery to remove them.
  • Failure to lose weight - it's possible you may fail to lose sufficient weight or regain weight you have lost after bypass surgery.

There is a chance your surgeon may need to convert your keyhole procedure to open surgery. This means making a bigger cut on your abdomen. This is only done if it's impossible to complete the operation safely using the keyhole technique.

The exact risks are specific to you and will differ for every person. Overall, there is a 2-5% risk of adverse effects (as listed above) and a 1 in 200 (0.5%) risk of death caused by having this operation.

How long does it take to get better from surgery?

You will normally need to stay in hospital for about two to three days after the operation. Full recovery from a gastric bypass can take two to three weeks.

Is the gastric bypass operation reversible?

The gastric bypass operation is considered to be a permanent weight loss measure.

However, in exceptional circumstances it's possible to fully or partly reverse it, for example, in an emergency or if you experience severe side-effects or complications from the operation.

A full reversal requires another operation of the same, or greater scale, with the same, or greater, risks than your original operation. Because of this, you will usually only be considered for the reversal operation if you experience long-term side-effects or complications. A full reversal of your gastric bypass operation will usually mean that you regain any weight you have lost.

An alternative to a full reversal which is sometimes performed is an operation to reduce the amount of your bowel that was originally bypassed. This won't mean that you will be able to eat more, but it will allow you to absorb more of your food.

This factsheet is for people who are planning to have gastric bypass surgery, or who would like information about it. Although every effort is made to inform you on gastric bypass surgery, there will be specific information that will not be discussed here. Also, your care will be adapted to meet your individual needs and may differ from what is described here.

Further information:

Association for the Study of Obesity (ASO) 020 8503 2042

British Obesity Surgery Patients Association (BOSPA) 0845 602 0446

Gastric bypass prices start from£9,246*


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