Enlarged RNY Gastric Bypass Pouch: What You Need To Know

April 22, 2019

"How do I know if I have an enlarged pouch?" is a common question for patients who underwent a Roux-en-Y Gastric Bypass. Let’s quickly review the anatomy of a patient after Roux-en-Y Gastric Bypass. The stomach is transected to create a small pouch, which is the size of a large egg. It is measured to be between 75-100 cm, and it too is transected - this is called the Roux limb. A connection between the small intestine and the transected stomach is created. This connection is called a gastrojejunal (GJ) anastomoses, which is about 1-1/2 centimeters.

Subsequently, the small bowel portion that drains the bile and pancreatic juices, called the biliopancreatic limb, is connected to the Roux limb. The two limbs come together to form the common limb or channel. Food is digested once the two limbs meet, and digestive juices mix with the food and break its content. (See diagram below.)

For the first 9-12 months, patients lose weight fairly rapidly. Initially, the rate of weight loss is rapid and then slows down as the patient moves further out from surgery. The weight loss mechanism is multi-factorial in patients who’ve had Roux-en-Y Gastric Bypass.

One common statement is, ‘I don’t have the same appetite suppression, which I had in the early phase post-surgery’!

Increased Hunger and Decreased Appetite Suppression

THREE factors play a major role in the initial weight loss phase.

The small pouch allows for a significantly smaller amount of food, which translates to fewer calories.
Bypassing a portion of the small bowel and only allowing the mixing of digestive enzymes with food in a shorter segment leads to decreased absorption.
Hormonal changes occur which ultimately leads to decreased hunger and effectively increased metabolic activity.

Let’s focus on the Gastric pouch, its role in weight loss, and potentially weight regain after the first year of Roux-en-Y Gastric Bypass. As described above, the Gastric pouch's role is to limit the amount of food consumed after Roux-en-Y Gastric Bypass.

However, there is also a very potent metabolic and hormonal mechanism involved in this early weight loss. The stomach is divided near the gastroesophageal junction. It is believed this location contains ghrelin hormone-producing cells; therefore, by partitioning the stomach in this manner, the ghrelin hormone levels are decreased.

Ghrelin hormone stimulates the hypothalamus center in the brain producing the sensation of hunger. As the hormone level increases, the sensation of hunger increases too. This leads the brain to halt other activities to make sure the body receives the food eaten. We have all been in situations where we are so hungry we can’t focus or perform any other activities before eating. As the ghrelin hormone decreases the hunger sensation, patients may initially have to remind themselves to eat, otherwise; they may not eat for hours.

The Gastric pouch's small size allows less food to be consumed and, therefore, fewer calories. The connection between the stomach and the small bowel also plays a very important role in slowing the speed at which food passes from the Gastric pouch into the small bowel. This also leads to a sensation of fullness and less hunger.

Getting Hungry Faster With Larger Amounts of Food

As the body adapts to your post-surgery anatomy, several changes occur. It slowly adapts to lower ghrelin levels and its cascading effects. Being a muscle, the Gastric pouch slowly enlarges, and the capacity to accommodate more food increases. The gastrojejunal anastomosis, the connection between the Gastric pouch and the small bowel, also widens over time.

Let’s evaluate these changes and their effects. The enlarged pouch means more food is needed to feel full, so more calories will be consumed. Also, the widening of the gastrojejunal anastomosis allows food to transit faster through the Gastric pouch. As larger quantities of food transit faster through the Gastric pouch, larger amounts of calories are consumed.

However, the predominant reason patients gain weight after weight loss surgery is consuming calorie-rich liquids and easily digested meals that don’t allow for satiety. Examples of these are milkshakes, ice creams, alcohol, creamy soups, chocolate, etc.

An Enlarged Pouch and Weight Regain After WLS

The anatomy must first be evaluated. One cause for increased food intake and hunger may be a gastro-gastric fistula, communication between the Gastric pouch and the stapled stomach, so the stomach's capacity significantly increases should this happen. This will show on imaging and endoscopic studies. The treatment for this is to disconnect the two parts of the stomach. It is usually challenging and should only be undertaken by an experienced bariatric surgeon.

If there are no significant anatomical abnormalities, then the Gastric pouch's size and the gastrojejunal anastomosis needs to be evaluated. Re-operative surgery is definitely feasible, and you should discuss if you are a good candidate with your surgeon. The size of the pouch can be revised and made smaller. The gastrojejunal anastomosis may need to be narrower during the same operation. Furthermore, most surgeons will also manipulate the length of your roux and biliopancreatic limbs to stimulate hormonal changes and increase malabsorption.

Revisional bariatric surgeries are very challenging, weight loss isn’t as effective as de-novo surgery, and complication rates are higher as well. You should discuss it in great detail with your surgeon and make an educated decision whether to move forward with it or not.