Gastric Bypass

Roux en-Y gastric bypass surgery is the gold standard operation against which all other obesity operations are judged. First performed in the USA in 1967 by Mason & Ito, it has stood the test of time providing reliable, long-term weight loss with little long-term risk of malnutrition or complications. Globally it is the most common procedure with 200,000 gastric bypasses performed in the US alone in 2008. First performed as an open operation it is now mainly performed laparoscopically, reducing hospital stay to two or three days with a shorter time to return to normal activities.

How Does The Gastric Bypass Work

A gastric bypass has a physical and hormonal effect. Physically it restricts food intake, portions sizes after surgery are much reduced with an early feeling of fullness. Over-eating causes abdominal discomfort and vomiting. While the majority of the reduction in a patient’s calorie intake is attributable to the restriction, initially there is also an element of malabsorption of fat similar to the duodenal switch. Long-term malabsorption is probably not important as the patient’s body adapts to the bypass. Nevertheless patients do need regular dietetic review and should be tested for anaemia annually after surgery.

The gastric bypass also reduces a patient’s appetite. The mechanism by which this occurs is not fully understood, but is related to a change in the normal gut hormonal patterns. Bypassing the first part of a patient’s small intestine affects the production of hormones which control appetite. After surgery most patients feel far less hungry, often forgetting to eat. Bypass surgery also affects the hormones that control blood sugar and consequently many diabetic patients become non-diabetic immediately after surgery.

Gastric Bypass Surgery

While the majority of patients will be suitable for laparoscopic (keyhole) surgery, for some patients open surgery may be a safer option. Irrespective of the approach used, internally the bypass is performed in the same way. Your surgeon will advise you on the best option for you. We use advanced medical products from Covidien.

The patient is admitted to hospital on the day of surgery. A general anaesthetic is needed for the surgery, it cannot be performed under local or spinal anaesthesia. Laparoscopic surgery uses six small cuts on the upper abdomen, three are about 1.5 cm long and three are about 0.5 cm long. Using a digital telescope and long operating instruments the surgeon performs the procedure in a standardised way. For open surgery, Streamline surgeons use an 8 to 10 cm long midline incision in the upper abdomen that. Most other centres performing open surgery will use a much longer incision.


Before Surgery

After Surgery

Before Roux En Y Gastric Bypass Surgery
After Roux En Y Gastric Bypass Surgery


The first step of the operation is to make the Roux en-Y bypass from the small intestine. The small intestine is divided using a surgical stapler 0.75m to 1.25m from it’s origin, approximately 0.75 to 1.5 m from the place of division it is re-joined to the small intestine. This join is made using a combination of a surgical stapler and suturing. The next step is to make a small gastric pouch from the patient’s stomach. Surgical staplers are used to form a vertical pouch of approximately 20 ml in volume. The bypass is then joined to the pouch using a 1 cm diameter join called an anastomosis.

The skin incisions, laparoscopic or open are closed with soluble stitches and local anaesthetic is injected into the skin around the incisions to reduce post-operative pain. A surgical drain, which is a long plastic tube, may be placed close to the gastric join passing through the patient’s abdominal wall to drain into a bag. It will normally be removed after 48 to 72 hours. Similarly, it is sometimes necessary to keep the gastric pouch empty with a fine plastic tube passed through the patients nose into the pouch. This tube is also normally removed after 24 to 48 hours.

After Gastric Bypass Surgery

After surgery, the patient spends an hour or two in the recovery area of theatre, being closely observed before returning to the ward. The patient has an intravenous drip in their arm for fluid, oxygen through a face mask, heart monitoring via leads on their chest, and blood pressure monitoring with a special cannula placed in an artery in the wrist. The patient will also have pneumatic compression  stockings around the calf, which improve blood circulation, through the leg veins during surgery helping to prevent thromboses.

After surgery the patient is usually kept nil by mouth overnight before being allowed to drink small amounts the following morning, building to normal drinking through the first day after surgery. On the second day, soft diet is started ready for discharge the next day. The pain after laparoscopic surgery isn’t usually too bad, it is a bit worse after open surgery but can usually be controlled without too much difficulty. Morphine may be needed in the first 24 hours after laparoscopic surgery and for 48 hours after open surgery. The rate at which morphine is injected is controlled by the patient using a computer controlled syringe, when a button is pressed the syringe injects a small dose of morphine into a vein. Software prevents the patient from over-dosing themselves. After a day or two pain should easily be controlled with paracetamol and ibuprofen. Patients having a laparoscopic gastric bypass are usually discharged from hospital on the third day after surgery, but may sometimes be fit for discharge the evening before. After open gastric bypass surgery patients are discharged on the third or fourth day after surgery.

After discharge, it is important to rest and eat carefully. Most people need two to three weeks off normal activities before returning to work. The pain shouldn’t be too severe and should be controlled with paracetamol and an anti-inflammatory pain killler such as ibuprofen. Patients shouldn’t drive for ten days to a fortnight and should notify their insurer before driving. After surgery patients need to stick to the diet recommended by our dieticians, slowly building up too bigger portions and less easily digested foods such as meat and fish. Most medication can be taken as normal although it is sometimes necessary to break tablets or capsules.

Follow Up After Surgery

Good follow up is essential after gastric bypass surgery to get the best weight loss and ensure patients don’t develop protein malnutrition or vitamin deficiency. The best follow up advice is given by specialist bariatric dieticians trained to advise patients on diet and vitamin supplementation after bypass surgery. Research has shown that the patients who achieve the best weight loss have worked well with their dietician’s sticking to the prescribed diet. Patients should take a multi-vitamin daily and be checked for anaemia annually by their general practitioner.

Expected Weight Loss & Health Benefits

Research including many thousands of patients has shown that on average patients having a gastric bypass lose 66% of their excess weight. Putting this weight loss into context, an average patient with a Body Mass Index of 45 kg/m2, who is 5’6” tall and weighs 19.5 stone is 8.5 stone over their ideal weight. On average with a gastric bypass this patient will lose nearly six stone and have a long-term weight of 13.5 stone. The same research compared the gastric bypass with other surgical procedures, the gastric band has an average weight loss of 49% and duodenal switch 70%.

In practice weight loss after bypass surgery is affected by many patient factors including age, activity level and basal metabolic rate. Many of Streamline’s gastric bypass patient’s have much better than average weight loss.

Health Benefits

  • In addition to the weight loss there is a dramatic improvement in the medical conditions commonly associated with obesity.
  • Raised blood cholesterol is  corrected in over 70% of patients.
  • High blood pressure is cured in over 70% of patients, and medication requirements are usually reduced in the remainder.
  • Obstructive sleep apnoea is resolved in 86% of patients, snoring improves for most patients
  • Diabetes Mellitus is cured in up to 90% of patients, often within days of the surgery.
  • Reflux of acid is usually cured by the surgery.
  • Low back pain and musculo-skeletal pain is usually relieved or improved.