The Roux-en-Y Gastric Bypass (RYGB) is a bariatric operation designed to facilitate substantial weight loss by modifying the stomach and the small intesine. In this procedure, a small pouch is created from the upper section of the stomach, significantly limiting food intake. This newly formed pouch is then connected directly to a section of the small intestine, essentially bypassing the majority of the stomach and a significant portion of the small intestine. This rerouting is achieved through two critical connections or "anastomoses": one where the small stomach pouch is joined to the small intestine, and another further down where the bypassed portion of the stomach and upper intestine is reattached to the small intestine.
Absorption Before and After Roux en-Y Gastric Bypass Surgery
Normal Absorption Before Gastric Bypass
Stomach: The stomach primarily initiates the digestion of proteins through the action of gastric acid and enzymes like pepsin. The stomach acid convert iron and calcium to forms that is easier for the intestine to absorb. The stomach also secrets the interinsic factor. This binds Vitmain B12 facilitating its absorption by the small intestine. The stomach does not absrob much.
Proximal Small Intestine (Duodenum and Jejunum): This is where a significant portion of nutrient absorption occurs. The duodenum and jejunum are primarily responsible for the absorption of iron, calcium, magnesium, and the majority of vitamins, including fat-soluble vitamins (A, D, E, K). The proximal small intestine also absorbs most carbohydrates, proteins, and lipids.
Rest of the Intestine (Ileum and Large Intestine): The ileum continues the absorption of nutrients not absorbed by the jejunum, including vitamin B12 and bile acids, which are critical for fat digestion. The ileum and large intestine also absorb water and electrolytes.
Changes in Absorption After Roux en-Y Gastric Bypass Surgery
Macronutrient Absorption:
Proteins: The altered pH and reduced stomach size after RYGB can impact protein digestion, as less gastric acid and pepsin are available. This might lead to slightly reduced efficiency in protein absorption, particularly in the early postoperative period. However, most patients can absorb enough protein from the adapted small intestine with proper dietary intake.
Carbohyrdate: absorption of carbohydrates is usually not affected.
Fats: Fat absorption is more significantly impacted due to bypassing the duodenum and jejunum, where most fat digestion and absorption occur. The reduced emulsification by bile acids (due to altered bile flow) and decreased lipase activity can lead to steatorrhea (fat in the stool) and contribute to fat-soluble vitamin deficiencies.
Micronutrient Absorption:
Iron and Calcium: These minerals are primarily absorbed in the duodenum, which is bypassed in RYGB. Reduced stomach acid also decreases iron's conversion to its more absorbable form, leading to an increased risk of anemia. Calcium absorption is similarly affected, increasing the risk of osteoporosis.
Vitamins: The absorption of fat-soluble vitamins (A, D, E, K) is compromised due to decreased fat absorption. Vitamin B12 absorption is also impacted due to bypassing parts of the stomach that produce intrinsic factor, essential for its absorption in the ileum.
Other Micronutrients: The absorption of other micronutrients like magnesium and zinc can also be affected, given their absorption sites are in the regions of the intestine that are bypassed or altered.
Patients require lifelong supplementation of vitamins and minerals, particularly those whose absorption has been most affected, to prevent deficiencies and associated complications.
Advantages of Roux en-Y Gastric Bypass
- Significant and Sustained Weight Loss: RYGB typically results in substantial long-term weight loss, helping patients lose up to 70% of their excess weight. This dramatic reduction can significantly decrease the risk of mortality associated with obesity.
- Resolution of Comorbidities: The procedure has a profound impact on obesity-related health conditions. Diabetes remission rates are notably high, with many patients experiencing improved or normalized blood sugar levels. Hypertension, obstructive sleep apnea, and dyslipidemia also improve or resolve in a majority of patients.
- Metabolic Benefits: The surgery induces significant metabolic improvements, including changes in gut hormones that lead to reduced appetite and increased satiety, making it easier for patients to adhere to healthier dietary patterns.
- Improvement in acid reflux or GORD: One of the notable advantages of Roux-en-Y Gastric Bypass (RYGB) operaton over all other bariatric operations is its beneficial effect on Gastroesophageal Reflux Disease (acid reflux). This is achieved by several mechanisms.
- Weight Loss: The substantial weight loss that follows RYGB reduces intra-abdominal pressure, one of the key contributors to GORD.
- Anatomical Changes: RYGB alters the stomach's anatomy, significantly reducing the stomach size and, consequently, the amount of acid produced. Anatomical Changes: RYGB alters the stomach's anatomy, significantly reducing the stomach size and, consequently, the amount of acid produced.
- Reduction in pressure inside the stomach pouch: By joining the small stomach pouch to the intestine this reduces the pressure inside the stomach pouch thus less pressure to drive acid the wrong way up into the oesophaugs.
- No bile reflux: the second joint in RYGB is done about 60-100cm down stream from the stomach pouch joint. This ensures that no bile reaches the stomach pouch and thus oesopahgus. This is one of the main advantages of RYGB over OAGB.
