One Anastomosis Gastric Bypass
(Mini Gastric Bypass)

One Anastomosis Gastric Bypass (OAGB)

What is an OAGB?

The OAGB, also known as the ‘Mini’ or  ‘Omega Loop’ Gastric Bypass, is a procedure combining some properties of the Sleeve Gastrectomy, with those of the Roux-en-Y Gastric Bypass. However, nothing is removed from your body during an OAGB. It differs from the traditional Roux-en-Y Gastric Bypass, requiring only one join, instead of two. This procedure can be performed either robotically or laparoscopically (keyhole surgery), leaving you with about five small incisions (cuts) in your abdomen.

How does an OAGB help you?

This procedure affects both food restriction and decreased calorie absorption, resulting in significant weight loss. It decreases your stomach capacity from approximately 1500ml to 100ml – reducing the amount of food you can eat. Approximately 150-200cm of the top portion of the small bowel is bypassed, therefore less of the nutrients and calories in the food eaten is absorbed. The result is that your satiety hormone LEPTIN will increase, and your hunger hormone GHRELIN will decrease, causing you to feel less hunger, and fuller for longer. This procedure also positively affects other hormones improving blood sugar control and diabetes.

Mini Gastric Bypass

Advantages of an OAGB

  • Less complex than the Roux-en-Y Gastric Bypass (only one join instead of two). 
  • Shorter operating time than the Roux-en-Y/SADI-S bypasses – takes approximately 1.5 hours to complete.
  • Better weight loss results than the Sleeve Gastrectomy – may reduce excess weight by 70-80%.
  • More powerful effect on diabetes than the Sleeve Gastrectomy – can reduce its severity or may completely reverse it (the outcome is dependent on how long you have had diabetes and used insulin).
  • Can improve other obesity related conditions such as high blood pressure, high cholesterol, sleep apnoea, and osteoarthritis symptoms.
  • Less risk of weight regain due to the intolerance of fatty or sugary foods, leading to unpleasant ‘dumping’ syndrome – these foods will be avoided!
  • Less risk of bowel obstruction than the Roux-en-Y Gastric Bypass (only has 1 join instead of 2).
  • Can be reversed, but with some degree of difficulty

Disadvantages of an OAGB

  • More complex surgically than the Sleeve Gastrectomy due to bowel involvement.
  • Eating fatty or sugary foods will lead to dumping syndrome, symptoms of which include stomach cramps and diarrhoea.
  • Requires life-long vitamin and mineral supplementation to prevent deficiencies after surgery.
  • Not suitable for smokers and regular users of anti-inflammatory drugs (ie ibuprofen)

Risks and Complications of an OAGB

Risks In the Short-Term of an OAGB

(common to most surgical procedures)

  • Bleeding during or after the operation
  • Damage to surrounding organs
  • Wound infections
  • Chest infections
  • Deep Vein Thrombosis (blood clots in legs)
  • Pulmonary Emboli (blood clots in lungs)
  • Leakage or bleeding at the new joint between stomach and bowel
  • Death (very rare)
  • Anaesthetic complications (see section detailing these)

Risks In the Long-Term of an OAGB

  • Potential for adhesions or scar tissue formation within the abdomen that sometimes requires surgery to release (can occur after any abdominal procedure).
  • Potential for hernia formation at the site of the wound closure – this may require surgery to repair
  • Potential for internal hernia/bowel obstruction,  where loops of bowel tangle or twist – this may require surgery to correct
  • Potential for anastomotic strictures where the join between the stomach and bowel over tightens during the healing process – this may require stretching by gastroscopy
  • Potential to worse or develop new-onset reflux – this may require medication or revision surgery
  • Potential for development of ulcers if patients smoke or use anti-inflammatory medications (ie ibuprofen)
  • Potential for development of nutritional deficiencies due to bowel involvement and malabsorptive features – this may be avoided with good diet and vitamin/mineral supplementation
  • Potential for failure to lose weight, or subsequent weight regain – this most frequently occurs due to poor dietary choices

How is an OAGB performed?

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OAGB Animation

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The information herein is not intended as medical advice. It should be considered as a reference only, or a starting point for further discussions with Dr Willingham and his team about weight loss surgery. Please be aware that results may vary from person to person