Laparoscopic one anastomosis (mini/omega) gastric bypass

The Omega Loop Gastric Bypass is performed laparoscopically. It involves bypassing the food from a smaller stomach to the distal part of the small bowel, taking both a resitricitve and malabsorption approach to weight loss.

How does it work?

The bypass works by both restriction and malabsorption. The keys components include:

  • Stomach size reduction
    • More than 90% of the stomach is detached from the gastric pathway. This means the stomach is reduced to a very small size. With a smaller stomach, you can physically fit a much smaller amount of food and fluids into the stomach at any given time. Less food leads to reduce caloric intake and thus weight loss.
  • Reduced hunger hormone ‘Grehlin’
    • Parietal cells are located in the lining of the stomach. Parietal cells produce the hunger hormone ‘grehlin’.
    • Reduces appetite and improves metabolism: Grehlin acts on the brain to stimulate appetite, as well as acting of fat cells to store fat and increases growth hormone which also stimulates appetite and fat storage. With a large portion of the stomach removed, the amount of hunger hormone grehlin is also greatly reduced, thus reducing hunger. Less hunger leads to reduce caloric intake and thus weight loss.
    • Improves insulin resistance: Grehlin suppresses insulin production from the pancreas, reduced grehlin and an increase in 2 other metabolic hormones (GLP-1 and PYY) that increase following a gastric sleeve, leads to increased insulin secretion and improvement in insulin sensitivity and improved diabetic control with weight loss.
  • Neurohormonal pathway alternations reduce appetite, improve metabolism and reduce insulin resistance
    • Studies show that both the gastric sleeve and gastric bypass affect key neurohormonal pathways leading to appetite suppression and an increase in metabolism. This also assists with resetting the ‘weight set point’ and use of calories consumed.
  • Malabsorption of intake
    • Less absorption of food leads to less caloric intake and increased weight loss.​

How is it performed?

Laparoscopically the top 5% of the stomach is divided from the remainder of the stomach, creating a small stomach pouch. This restricts the amount of food or fluid consumed at any given time.

Next a loop of small bowel 150-200cm distal to the stomach is attached to the lower part of the stomach pouch. The food passes from the small pouch into the distal small bowel, bypassing the proximal 2m of small bowel. In effect, there is less absorption of food (and calories). Fewer calories absorbed, means weight loss.

Advantages of Omega loop bypass

  • ​Significant excess weight loss
  • Significant improvement/resolution of type II diabetes mellitus in many patients

Disadvantages of Omega loop bypass

  • ​Higher risk of micro-nutrient and vitamin deficiency. Multivitamins and monitoring required.
  • Potential dumping syndrome
  • Complications are uncommon and several measures are taken to reduce risk of complications.
    • General surgical complications
    • Staple line bleed or leak
    • Stricture of the stomach or joins

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