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Gastric bypass


A gastric bypass is one of the more extensive forms of bariatric surgery. It is offered to people who are morbidly obese, who may have a BMI of 35-40 or higher.

gastric-bypassThe overall surgical plan is to bypass most of the stomach and the first part of the small intestine. A new route for food is created. This no longer enters the main stomach, but is sent through a thin tube that joins with the jejunum, the second part of the small intestine.

The stomach is left in place because it makes valuable digestive enzymes that need to pass into the small intestine to digest the food that you eat.

This type of weight loss surgery is called a Roux-en-Y gastric bypass after the surgeon who devised it (Mr Roux) and because the anatomical changes result in a Y shape formed by the stomach and the new route for food.

Who can benefit from a gastric bypass

If you are morbidly obese and have not been able to lose weight by changing your diet and doing more exercise, a gastric bypass is an alternative to a gastric sleeve operation. More people lost the weight they need to lose after a gastric bypass and this is now the most common form of bariatric surgery available in the NHS.

It is a serious operation, but the risks of surgery are often outweighed by the advantages you gain by losing weight. Being morbidly obese is highly dangerous, putting you at risk of developing other chronic health conditions such as type 2 diabetes, sleep apnoea and some types of cancer.

How to prepare for a gastric bypass

Before signing the consent and making the decision to go ahead, you will have a detailed consultation with Mr Alhamdani. He will explain what is involved, the weight you can expect to lose and also what the operation will mean for your life afterwards.

As well as preparing mentally, you will need physical checks to make sure you are well enough to go ahead. This will involve:

  • Having checks on your heart, lungs, liver and taking your blood pressure.
  • Calculating your BMI accurately
  • Losing some initial weight to make the surgery safer. Some patients have a gastric sleeve as a first stage to reduce their BMI before opting for the gastric bypass.

You will need to follow a liquid, low-fat diet with no alcohol for two weeks before surgery to shrink your liver. You will also need to fast the night before the operation as you will have a general anaesthetic.

The gastric bypass operation

The operation itself can take up to three hours. Usually the surgery is done laparoscopically – using a keyhole technique – but some patients require open surgery.

  • Staples are put in place to create a pouch from the top of your stomach
  • A piece of small intestine will be used to connect this pouch to the jejunum
  • The stomach is not removed and its blood supply is left intact so that it can produce digestive enzymes.
  • Once the bypass is complete, stitches are put in place and the incisions are closed.

This is major abdominal surgery and you will be in hospital for between two to four days. You may need drains to remove fluid from your abdomen and pain relief. As soon as you are up and about, and your pain is well controlled and all drains are removed, you will be able to go home.

After surgery

Your body will heal over the next few weeks but you will need to work hard at taking in the right nutrients. While you are in hospital you will be given liquids only as this allows the stomach and intestines to heal.

Within a few days you can start to eat very soft, almost liquid foods such as smooth, thin soup, milk, jelly and fruit juice. You must not have any fizzy drinks and no caffeine. The size of the stomach pouch you have will mean that you can only take a little amount at a time without feeling ill.

After a week or so, you can start eating mashed, soft foods, gradually moving onto more solid foods over a period of two months. You will need to eat very small meals, chew food carefully and drink fluid between meals, not with food.

You will need to change the way you eat completely because trying to eat normally will make you ill, causing nausea, vomiting and diarrhoea. All patients who have had a gastric bypass also need to take vitamin supplements as their digestion is not as efficient as before.

As part of our multi-disciplinary team approach you will see a specialist bariatric dietician (Mrs Lucy Jones) or a specialist nurse practitioner (Mrs Toni Jenkins) during your stay in hospital who will talk to you about your diet, how to lose weight after surgery, and what supplements (multivitamins) you require after your gastric bypass.


The International Federation for the Surgery of Obesity and Metabolic Disorders (IFSO)

The Whittington Hospital

American Society for Metabolic & Bariatric Surgery

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