Single anastamosis bypass (also known as mini-bypass or omega-loop bypass) is a variation on the traditional ‘roux en y’ gastric bypass.  The variation has designed to decrease the rate of internal hernia (3-5% lifetime risk after ‘roux en y’ bypass) and the rate of complications after surgery (one surgical join required and not two).  It appears to give similar weight loss and health benefits to the traditional ‘roux en y’ gastric bypass, but does have a 10-20% rate of bile reflux (reflux that isn’t as easily treated with tablets).  

In gastric bypass two things are done to cause weight loss.  Firstly a small pouch is created at the upper part of your stomach. This has the effect of decreasing the amount of food you can eat in a meal.  Secondly, your small bowel is joined to the pouch.  This decreases the amount of time food will spend in contact with both the bowel, and also the enzymes that help digestion and absorption in your bowel.   It also alters the way your body processes food, sugars, carbohydrates and hormones associated with feelings of fullness , also helping with long term weight loss. 

A single anastamosis gastric bypass is performed as a laparoscopic (key-hole) operation through 5 small incisions.  Firstly, the pouch is made using a stapling device.  Secondly the small bowel joined with a single join to the pouch.   After this is done a test is performed to ensure the join is watertight.  You should expect to spend 1-2 nights in hospital after your operation.

Longer term you must avoid all anti-inflammatory tablets and smoking.  Using anti-inflammatory tablets or smoking even years after your surgery can cause significant ulcers and other problems.  

What to expect

Before your operation you will be expected to go on an ‘opti-fast’ diet for 2-6 weeks.  This is a meal replacement diet which will help you loose a few kilos, but most importantly will shrink your liver before surgery.  Shrinking your liver is important as it makes the operation safer for you as your liver is less likely to bleed or tear during surgery.  Megan or Sue, our dieticians, will give you more information on this diet when you see her. 

You will be admitted to the hospital on the day of your operation.  You will meet the nursing staff and the anaesthetist who will be administering your anaesthetic.  After your operation you will wake up in the recovery area of the hospital where specialised recovery nurses will look after you and ensure you recover from your anaesthetic safely.  After this you will be moved either to the day stay area of the hospital or to the ward. At any stage if the nurses have concerns about your recovery they will contact your anaesthetist or Dr Hamer.

Side effects to be aware of

All operations have side effects or potential complications you need to be aware of.  The overall  chance of a complication is low but with surgery can never be zero.  Risks of any operation include the risk of the anaesthetic, small risks of bleeding, infection, developing hernias where the key hole instruments are inserted, blood clots and pneumonia.  In gastric bypass there is a risk of leakage from where the new joins have been made.  This can be a serious complication and in some cases require a prolonged stay in hospital, and further interventions or operations.  If your operation is not able to be performed safely with key-hole surgery, a larger cut may need to be made.  This is uncommon. 

Longer term you can develop ulcers or a narrowing at the join between the stomach and small bowel.  This is relatively uncommon and most often occurs if you have restarted smoking. 
Some people develop ‘dumping syndrome’.  This occurs as a result of food passing quickly into the small bowel which can give you flushing or make you feel light headed.  This occurs more commonly in the months immediately after your surgery as your body adjusts to your bypass.  If it occurs later on it can often be rectified by adjusting your eating patterns.  Our dieticians can help you with this.  

There is a small but real risk of developing an ‘internal hernia’.  This is an emergency where your bowel wraps itself around the section of small bowel that is joined to the stomach.  This is important to be aware of as if you need to go to the emergency department with abdominal (stomach) pains, you will need to make sure the doctors looking after you know that you are a bypass patients as they urgently will need to perform a CT scan.   

After your operation it will be recommended that you take a multivitamin life-long.  If you don’t do this you are at risk of vitamin and mineral deficiencies as your body cannot absorb these in the same way that it could before your operation.

After your operation

After surgery, to begin you will only be allowed small amounts of water and similar clear fluids.  You will go home on a fluid diet and from this gradually move to what will become your regular diet normal healthy foods in smaller portions.  The booklet you will be given when you schedule surgery contains detailed information on all of this for you. 


After you have been discharged from the hospital, you will have dressings over your wounds.  These do not affect how well your wounds heal, but they do protect your clothes from any seepage which may occur.  If they become dirty or wet they may simply be removed and changed for a similar dressing or a band aid.  After a week they can be removed and discarded.  Occasionally people feel more comfortable leaving a dressing on for an extra week, particularly if the wound is somewhere that can rub on your clothing. 


Your wounds will be closed with either glue or dissolving sutures, neither of these need removal. 

Pain killers: 

Most people find taking regular paracetamol to be enough for their pain.  Paracetamol has the advantage (unlike most other pain killers) that it won’t make you constipated or feel woozy.  It is also very safe if taken carefully according to the instructions on the packet.  In some circumstances you will be given additional pain killers to take home with you.  If this is the case you should read and follow the instructions carefully. 


Complications after discharge are unusual.  If you do have any problems, you have multiple ways of accessing help.  During office hours you can contact Dr Hamer’s rooms or your GP.  For more pressing problems or after hours you can also contact the emergency department at the hospital. 


Generally most people find that they are fit to return to work after about 2 weeks.  Everyone is different and some people will return earlier, and other need a bit longer.  If you are still having significant problems at the 2-3 week mark you should be reviewed to ensure you are still recovering appropriately.

Follow Up

You will be seen 4 weeks after your operation.  After this you will be seen regularly by both Dr Hamer and one of our dieticians to monitor your weight loss.  Many people decide it is helpful to continue to see a psychologist regularly as well.