OAGB is a keyhole (laparoscopic) procedure. The first step is using a stapling device to create a long and narrow stomach tube in line with the oesophagus, and disconnect the rest of the stomach from the food stream. The operation is completed by joining the lower end of the newly created stomach tube to a loop of small bowel (Jejunum) 2 meters from the start.
How it Works
With OAGB anatomy, the small stomach leads to portion control (restriction). After passage through the small stomach tube, food enters the small bowel with a 2-meter lead, skipping the first 2 meters of the intestine. This reduces the total intestinal length available for digestion and absorption from an average of 6 meters down to 4 meters (malabsorption). It is believed that post bariatric surgery, physiological changes are equally or even more important in long term weight loss and weight maintenance. These changes are mediated by gut hormone changes, gut related nerve fibre signals and immune mediated cell responses. With these changes being more profound, gastric bypass is considered a more metabolically potent operation compared to the sleeve gastrectomy, hence better for type 2 diabetes.
Quick Info
Stomach size surgically reduced and 1/3 of small bowel bypassed
Procedure manipulates hunger signals and other hormones, resulting in a stronger metabolic response, particularly beneficial for Type 2 Diabetics
This procedure is reversible
OAGB is WA Weightloss Centre’s preferred high BMI (BMI +50) & revision procedure
WA Weightloss Centre has performed over 1000 OAGB procedures over the past 7 years
OAGB leads to an average of 75-80% excess weight within the first 12 months, with more durable long term results
Patients typically return to work 2 weeks post surgery
Learn more about OAGB from Dr Werapitiya
Dr Senerath Werapitiya takes you through the weight-loss procedure.
One Anastomosis Gastric Bypass (OAGB)
Explainer video taking you through the steps of the procedure.
Further Information
The first gastric bypass was a one anastomosis gastric bypass carried out by Dr. Mason in 1966 (Mason loop). Initially it consisted of an horizontal stomach pouch with a loop small bowel join (anastomosis). Due to severe bile reflux, the reconstruction was changed to a “Roux-en-Y” configuration, which diverts the bile from the stomach and oesophagus. Over the next few years, Roux-en-Y gastric bypass became more established and later became the surgical standard. After the first laparoscopic gastric bypass was performed by Alan Wittgrove in 1994, the exponential growth of bariatric surgery started.
Laparoscopic Roux-en-Y gastric bypass is a technically challenging surgery with a steep learning curve and has potential risks of two bowel connections (anastomoses). In an attempt to make it simpler and safer, Dr. Rutledge developed the Mini-Gastric Bypass (or omega-loop or one anastomosis gastric bypass). His first surgery was in 1997. Although Rutledge published his experience with thousands of patients, for several years this technique has suffered the criticisms of bile reflux and risk of oesophageal malignancy. Increasing experience with this technique worldwide has reduced these concerns and in recent years it has gained wide acceptance among many surgeons. Over this period no oesophageal malignancy has been reported after OAGB.
- Major weight loss
- Durability
- Reversible
- Revisable
- Low risk
- Good for diabetics
- Ulcer risk
- Nutritional deficiency
- Bile reflux
- Difficult ERCP
- Dumping syndrome
- Diarrhoea
- Difficult ERCP
- Post prandial hypoglycaemia
I understand that obesity has been shown to increase the risk of death from a variety of medical illnesses. Obesity places individuals at an increased risk of diabetes, high blood pressure, respiratory disease, heart disease, high cholesterol, stroke, arthritis, clotting problems and cancer, all of which can increase the risk of disability and may even cause premature death. I have not been able to maintain a healthier weight following diet and exercise with my own best efforts. This is the reason why I am considering surgery as a weight loss option, fully understanding the quite drastic nature of this option.
The surgeon, with the help of the dietitian and other support staff, have given me a detailed explanation of the one anastomosis gastric bypass procedure as well as other surgical options including the gastric band procedure, the sleeve gastrectomy procedure and other gastric bypass procedures.
You will be provided with drawings, as well as written and verbal information regarding this procedure. You are strongly encouraged to make every reasonable effort to investigate and understand the details of the operation.
The laparoscopic one anastomosis gastric bypass operation is both a restrictive and a malabsorptive procedure. This operation involves creating a long narrow stomach tube with a join between a loop of small bowel and the far end of the stomach tube. The join is placed 200 cm from the top end of the small bowel bypassing the first two meters of the small bowel.
Just as there may be some expected benefits from the one anastomosis gastric bypass procedure, I understand that all surgical procedures including the proposed one anastomosis gastric bypass procedure involve risks. I understand that the list of complications includes the following but may not be limited to this.
Bleeding: Surgery involves incisions and cutting that can result in bleeding. This may range from minor to massive bleeding, which may require blood transfusion, emergency surgery and may even lead to death in extremely rare circumstances. Bleeding is most serious if it is within the abdominal cavity. Bleeding can occur into the intestine from the bowel join or into the abdominal cavity. After a bleed, it is usual for patients to go through a slow and long recovery period.
For patients on blood thinners and or blood pressure medication – I know that blood thinners can lead to a higher chance of bleeding after surgery and hence there is a need for me to stop such medication under medical supervision prior to surgery. Uncontrolled high blood pressure is another factor that may increase the risk of bleeding and I know the importance of taking my blood pressure medication as usual.
Leak: (Staple line or suture line failure) – I know that after this surgery, stapling and stitching is involved creating the stomach tube and the new join. These staple and suture lines are meant to be water tight without any leakage of intestinal content to the abdominal cavity. I understand that there is a rare risk of leaking (1 – 2%), particularly in the first three weeks after the surgery. Leaking from the staple line/bowel join is a serious problem. The leak may allow stomach acid, bile, bacteria and digestive enzymes to escape into the abdominal cavity causing severe infection (peritonitis). Common symptoms of a leak are severe upper abdominal pain, nausea, fever, increased heart rate, increased respiration and feeling sick.
I understand that strictly following the prescribed post-operative diet is important in minimizing the chance of a leak. I also understand that If I am worried about the possibility of a leak, I have to inform Dr. Werapitiya directly without delay.
I know if a leak is suspected, I may have to undergo further tests including x-rays and emergency surgery. I am aware that the emergency surgery usually involves placement of multiple drains and a nasal feeding tube. I am also aware that resolution of a leak can take a long period of time, usually requiring me to have in hospital care for a long period of time, sometimes weeks or even months. In the process, I may also require intensive care treatment or transfer to a different hospital for optimal care.
I understand the risk of leak is higher if one anastomosis gastric bypass is done as a revision surgery following failure of a previous gastric band or a sleeve gastrectomy. I also clearly understand that this complication can very rarely be lethal.
Infection: The most serious infection is peritonitis associated with a leak. This is fortunately extremely rare. There is also a chance of other minor infections like wound infection, bladder infection etc.
Blood Clot: Also called deep vein thrombosis (DVT) and pulmonary embolus. I understand that this is an exceedingly rare complication, but if severe can lead to death. I understand that blood thinning medications will be administered while I am in hospital to minimize the risk of blood clotting and calf compression stockings will be used. I also understand that from my part, it is important that I get out of bed as early as possible and move my feet and legs to try and help prevent blood clots. I also understand the importance of preventing dehydration and keeping up with my fluids.
Nausea, Vomiting and Headache: I understand that it is relatively common for me to feel some nausea, vomiting and/ or headache. This is partly a result of the fasting period prior to the surgery leading to some degree of dehydration, the effects of the anaesthesia and pain relief medication that I am going to be receiving, as well as the effects of the surgery. I understand that the powerful pain medication that I am going to be on will increase the chance of nausea and I understand the importance of seeking help with anti-nausea medication early to minimize the chance of vomiting.
Laparoscopic entry associated risks: Laparoscopic surgery uses punctures to enter the abdominal cavity which can lead to abdominal organ injury, (bowel, spleen, liver etc.) or lead to a puncture of a vessel that can lead to bleeding and even death in rare circumstances.
Anaesthetic complication: I understand that general anaesthesia these days is very safe, however, it is not without complications. I understand I will have a full description of the anaesthetic associated complications from my anaesthetist. I understand that I have been provided with the contact details of my anaesthetist and I am supposed to make an appointment with my anaesthetist prior to my operation.
Indigestion, Acid/Bile reflux: I am aware that acid/ bile reflux can happen after this operation leading to heartburn and regurgitation of fluid or food content. I also understand that this risk is higher in people who have had gastro-oesophageal reflux prior to having the operation. The new join between the stomach tube and the intestine is designed to minimise the chance of bile in the intestine refluxing back into the stomach. I am aware however, if this happens, this can lead to bile gastritis. In the rare instance where bile in the stomach tube refluxes into the oesophagus, it can also lead to injury to the oesophagus. I am aware that there has been concern regarding increased risk of oesophageal cancer in the long term as a result of bile reflux. However, to date there has been no reported cases of oesophageal cancer after this procedure. To manage severe bile reflux, anti-reflux surgery, reversal/revision of the bypass or conversion to Roux-en-Y bypass may be necessary.
Anastomotic ulcer: I know that I may develop an ulcer at the join between the stomach tube and the small bowel. I also understand that smoking ( including passive), heavy alcohol use, H pylori infection and non-steroidal anti-inflammatory medications (Aspirin, Ibuprofen, Voltaren etc.), can lead to an increased chance of ulcer formation. I am also aware that strong acid suppression medication (esomeprazole) is used in the first 6 months after surgery to minimize the ulcer risk. I understand a proportion of ulcers can go on to have further serious complications like perforation and severe bleeding, which are surgical emergencies. I also understand that in rare circumstances, when the ulcer fails to heal with medication, there may be the necessity for the operation to be reversed or revised.
Vitamin and mineral deficiencies: After one anastomosis gastric bypass there is malabsorption of many vitamins and minerals. I understand that I need to take vitamin and mineral supplements for the rest of my life to protect myself from these problems. I also know that I need to have at least yearly blood tests to measure the blood levels of these vitamins and minerals. I have been given detailed written information regarding the nutritional supplements by my bariatric dietitian. Common deficiencies that can occur after a one anastomosis gastric bypass include iron, vitamin D, calcium, B12, thiamine and folate. I know that in some cases the deficiencies can be so severe that they can lead to brain or nerve damage, and the operation may have to be reversed as a result.
Dumping Syndrome: I understand that dumping syndrome can occur in some patients after gastric bypass surgery. Symptoms of dumping syndrome include weakness, sweating, nausea, diarrhoea, palpitations and dizziness soon after a meal. I also understand a heavy load of refined sugars/refined carbohydrates, rapid eating, and drinking while eating, are all factors that may increase the risk of dumping. I also understand if it becomes a disabling problem, it may require reversal of the bypass operation.
Bowel Obstruction: Any abdominal operation can lead to post-operative scarring which may lead to bowel obstruction. I understand the chance of this is minimal with keyhole (laparoscopic) surgery. With changes in the orientation of the small bowel after one anastomosis gastric bypass, bowel obstruction can also rarely happen due to prolapsing of the bowel through tight spaces that are created as a result of the operation.
Hair loss: Many patients develop hair loss for a period after the operation. When this occurs it usually starts about 3 – 4 months after surgery and resolves about 7 – 9 months after the operation. This usually responds to the increased oral intake of protein and vitamins, but it may only recover partially.
Inadequate weight loss: I recognize that the one anastomosis gastric bypass surgery is not by any means a perfect treatment and that one of the risks that I face is a possibility of inadequate weight loss following this surgery. I also recognize that I may lose enough weight in the short term but may also experience late weight regain in the long term (close to 20% chance). I understand that I need to follow the dietitian’s instructions and continue my follow up commitments with the dietitian and the surgeon to minimize the chance of this happening.
Extensive weight loss: I clearly understand that I might suffer malnutrition and lose too much weight. I am well aware that some patients sustain excessive weight loss after weight loss operations. I understand that excessive weight loss may require surgical revision or reversal of the one anastomosis gastric bypass procedure to prevent malnutrition, vitamin and mineral deficiencies, or even death.
I am aware that up to almost 1% of people may lose an excessive amount of weight. As a part of this agreement, I promise and agree to monitor my weight and health carefully and if excessive weight loss occurs, I will submit to early and appropriate treatment.
Mechanical Issues: Narrowing (stricture) of the join between the stomach and the small bowel can occur after this operation, which may require further endoscopic procedures or even surgery. Mechanical issues associated with the stomach tube can develop in the form of segmental dilatation leading to a pouch or some narrowing that may require further surgery. Small bowel hernia or a twist (volvulus) can occur very rarely which can lead to small bowel loss.
Port site hernia (Incisional hernia): Extremely rarely, contents within the abdominal cavity can protrude through the muscle slits at the sites of access ports known as a port site hernia. This can be easily corrected with surgery.
Complications of Pregnancy: I understand that obese pregnant women are at higher risk for an adverse peri-natal outcome. I am also aware that there are well known risks to the patient and the baby after surgery for morbid obesity. Vitamin and mineral deficiencies can put newborn babies of gastric bypass mothers at risk.
NO PREGNANCY SHOULD OCCUR FOR THE FIRST 12 MONTHS AFTER THE OPERATION.
Gastric bypass has been shown to cause multiple types of vitamin and mineral deficiencies including iron, B12, folate, thiamine, vitamin D, calcium, and many others. Many of these deficiencies have been shown to cause birth defects or are suspected that they could cause birth defects.
We also know that many patients who lose weight feel that they are well after surgery and forget to take their vitamins. I understand and take full responsibility to be certain not to miss any of my vitamins and obtain a specialist obstetric consultation if I decide to go ahead with pregnancy following surgery.
Unplanned Pregnancy: Warning to women using oral contraceptive pills. Typical failure rates among pill users can be as high as 12 – 20 % according to some surveys. Other factors that have been shown to increase the risk of pill failure are smoking, diarrhoea, vomiting, drug interaction, systemic illness, psychological stress and menstrual disturbances. Therefore, it is important to recognize that birth control pills may not be an effective method of birth control after one anastomosis gastric bypass. Until those factors have resolved, we have found in many cases that oral hormonal methods of birth control may fail after one anastomosis gastric bypass. Couples need to plan another form of non-oral birth control for at least the first 6 – 12 months after surgery. The Depo-Provera injection has been associated with cases of marked nausea in post one anastomosis gastric bypass patients.
Depression: Depression and anxiety are common medical illnesses and have been found to be particularly common after weight loss operations.
Osteoporosis: There is a growing appreciation that weight loss procedures may be associated with the development of osteoporosis and bone disease. Gastric surgery and weight loss in morbidly obese individuals can cause increased bone resorption and increased bone loss. Treatment and prevention include calcium and vitamin D supplementation, and increased weight bearing activity.
22. Need for further surgery in the future: Weight loss surgery comes with no assurance to be able to achieve or maintain a a certain body weight target. In fact some long term weight regain is almost universal and outright failure with regaining all or even more than what you lost may happen in the long term. Up to 20% of post OAGB patients may end up with significant weight regain and may be in need of further measures for weight control including revisional surgery. In another 5%, long term post OAGB complications like intractable bile reflux / regurgitation, ulcer complications, post prandial hypoglycaemia, dumping or mechanical issues leading to blockages ect. may require further corrective surgery when other measures fail to resolve the issue.
I know that the practice of medicine and surgery is not an exact science and I acknowledge that no guarantee has been made about the results that may be obtained from this procedure.
I am aware that in the practice of medicine other unexpected problems, risks or complications not discussed may occur. I also understand that during the course of the proposed procedure, unforeseen conditions may be revealed requiring the performance of additional procedures, and I authorise such procedures to be performed. I further acknowledge that no guarantee or promises have been made to me concerning the results of any procedure or treatment.
I recognise that the proposed one anastomosis gastric bypass is a serious undertaking with known long-term risks. To minimise this risk, enable early detection of complications and to enable prompt treatment, I understand the importance of regular and life-long follow up. I promise that I will make every effort to follow Dr Werapitiya’s directions to protect myself from complications that may be associated with the gastric bypass procedure. I understand that Dr Werapitiya may involve other suitably trained doctors in my post-operative follow up care. I also promise to return to my surgeon’s clinic at 1, 3 and 6 months following surgery, and every year thereafter for evaluation and further education.
