Caloric Restriction

The mechanism for which RYGB works is multifactorial. The simplest mechanism is the caloric restrictive properties of an RYGB. The gastric pouch typically can hold approximately 20–30 ml of fluid. We are aware that carbohydrate‐controlled calorie‐restricted diets produce improvement in insulin resistance and beta cell function. Early post‐RYGB, a patient may have a reduced caloric intake of around 600–800 kcal per day. This undoubtedly will contribute to weight loss. However, studies have demonstrated that caloric restriction alone is not the only mechanism for metabolic improvements and weight loss. GIP, GLP‐1 and glucose levels were not significantly affected with caloric restriction alone compared to RYGB.

Grehlin

In addition to the restrictive properties of RYGB, there are metabolic factors involved in RYGB‐associated weight loss. Grehlin is a 28‐amino acid peptide released from enteroendocrine cells from the gastric fundus that plays a significant role in controlling body weight homeostasis. Grehlin stimulates appetite, affects glucose utilisation rates in adipose tissue and promotes hepatic lipogenesis. When fasting, Grehlin typically increases, and levels decrease after meals with gastric distention. In this recent meta‐analysis of 16 studies, levels of grehlin were found to decrease significantly in short term (<3 months) but found to be increased in long term (>3 months) after RYGB. No association was seen in grehlin levels with pouch size, alimentary or biliopancreatic limb lengths. Lack of decreased levels in long term after RYGB may be secondary to incomplete removal of gastric fundus unlike sleeve gastrectomy.

Incretins

Incretins are a group of metabolic hormones, which stimulate decrease in blood glucose levels. Often released after meals, they tend to augment insulin release and inhibit glucagon release.

Glucagon‐like peptide‐1 (GLP‐1) is a 30‐amino acid peptide hormone produced and secreted by intestinal enteroendocrine L‐cells mostly in the distal ileum and colon. GLP‐1 tends to release in two phases: an early phase 10–15 minutes postprandial and a late phase 30–60 minutes postprandial. One of the mechanisms is to delay gastric emptying, thus decreasing its own secretions. GLP‐1 stimulates insulin secretion and inhibits release of glucagon. A meta‐analysis published in 2017 looking at 24 studies determined that post‐prandial GLP‐1 levels were elevated post‐RYGB, while fasting levels remained the same. Shorter Roux limb length was also found to have increased GLP‐1 levels. No difference was appreciated with diabetes status, percent weight loss or the length of biliopancreatic limb. The increase in GLP‐1 after RYGB is thought to occur due to the small volume of gastric pouch and rapid travel to the small bowel.

Gastric inhibitory peptide (GIP) is a 42‐amino acid peptide hormone synthesised by K‐cells in the duodenum and jejunum. Their receptors are found in the beta cells of the pancreas. This hormone also increases insulin secretion, decreases apoptosis of beta cells and promotes beta cell proliferation. It promotes adipogenesis and lipid accumulation. Unlike GLP‐1, it does stimulate glucagon secretion but does not affect gastric motility. Post‐RYGB, post‐prandial levels of GIP decrease compared to prior to surgery. This is likely related to bypassing the proximal intestine.

Peptide tyrosine tyrosine (PYY) is a peptide hormone secreted by L‐cells in the ileum and colon. It is also secreted by the brain. PYY inhibits gastric emptying and intestinal motility. It also decreases appetite via central mechanisms. Several studies demonstrate a decrease in fasting PYY levels in obese patients, while others have not. However, there are exaggerated meal‐related increases in PYY after RYGB. Thus, these alterations in gut peptide secretion may encourage weight loss with RYGB.

Bile Acids

Bile salts are important regulators of energy balance and increase energy expenditure in adipose tissue. Bile acids facilitate digestion and absorption of lipids. Bile acids also bind with the nuclear receptor FXR and are associated with positive alterations in feeding behaviour (repression of hyperphagia) and improved glucose tolerance. Increased bile acids also upregulate the secretion of GLP‐1, thus regulating glucose metabolism. Bile acids are significantly increased following RYGB.

Foregut Hypothesis

There are two theories on the mechanism of diabetes resolution after RYGB. The foregut hypothesis predicts that excluding the duodenum from nutrients will prevent the secretion of anti‐incretin substances. Rubino et al. demonstrated a resolution of diabetes in rats after exclusion of the duodenum, followed by recurrence of impaired glucose tolerance after restoration of the duodenum.

Hindgut Hypothesis

This theory predicts that early presence of food into the distal small bowel stimulates incretin secretions, which as explained previously will increase insulin production, decrease insulin resistance and improve glycaemic control. Others believe that both theories act together towards the goal of diabetes resolution.

Positioning

The position of the patient and where the surgeon chooses to stand is variable and based on surgeon preference. Some surgeons prefer to stand on the patient’s right side, while the patient lay supine with arms out and legs together. Others prefer a ‘French’ position where the surgeon stands between the patient’s legs in lithotomy position (Figure 17.1).

Trocar Placement

As more surgeons are performing bariatric surgery, the placement of trocars has become increasingly variable. However, unlike non‐obese patients, external landmarks for trocar placements may be deceiving and lead to difficulty and poor ergonomics while performing the procedure. What is also important to note is the uniqueness of an RYGB in the sense that the procedure requires to perform an anastomosis in both the infracolic and supracolic regions, further signifying the importance of trocar placement in order to perform both with minimal difficulty. Lastly, many patients have a thick abdominal wall with an abundance of subcutaneous tissue. Therefore, placing trocars in a direction towards the base of the mesentery or the midline may help to avoid rigidity of mobility of the instrumentation while performing critical portions of the procedure.

Below is an example of the authors’ preferential trocar placement based on internal anatomy:

1. Initial trocar (12 mm) – left upper quadrant, subcostal and midclavicular line: We perform an optiview entry with a 10 mm zero‐degree scope without prior insufflation. This area is often free of prior surgical adhesions. Additionally, this placement allows us to determine best placement for our camera trocar. It may be beneficial to have the anaesthesiologist decompress the stomach with an orogastric tube prior to entry.
   
2. Primary camera trocar (5 mm trocar): We plan for this placement to be in midline with entry into the abdominal wall at a 45° angle directed towards the edge of the liver at which the falciform enters. This will be the primary trocar for the camera to be used.
   
3. Right sided trocar (12 mm trocar): It is placed to the right of the midline, midclavicular and angled towards the root of the mesocolon so that it may have proper triangulation on the hiatus and the ligament of Treitz.
   
4. Left inferior trocar (12 mm trocar): It is placed to the left of the camera trocar at the midclavicular line. This should be directed towards the root of the transverse mesocolon. This port is responsible for the stapler entry of the jejunojejunostomy creation.
   
5. Liver retractor (5 mm incision): Subxiphoid placement using Nathanson retractor (Figure 17.2).

The following description is how the authors perform an RYGB. There are many different variations that are discussed; however, the concepts remain the same.

Jejunojejunostomy Creation

Surgeon stands on the patient’s right side and the assistant on the patient’s left. Initial step is to take the omentum and roll it over the transverse colon and tuck it beneath the liver. The ligament of Treitz is located and the small bowel is followed while measuring the length of the biliopancreatic limb. The length of the biliopancreatic limb ranges from 50 to 150 cm depending on the patient’s BMI. As the biliopancreatic limb is measured, the proximal bowel is placed towards the ligament of Treitz to keep only the bowel involved in the anastomosis in the field. Once a location of transection is decided, a 60 mm linear cutting stapler is used to transect the bowel (Figure 17.3).

An ultrasonic vessel sealer is used to transect the mesentery towards its root with care to stay in between both sides of the transected bowel. The distal portion of the transected bowel is now followed and measured in order to find the length of the Roux limb. Of note, the direction of placing the bowel while measuring is in an anti‐clockwise fashion in order to prevent the dreaded Roux‐en‐O. Our Roux limb length ranges from 100 to 75 cm depending on the patient’s BMI.

Once the site of anastomosis is chosen on the Roux limb, the end of the biliopancreatic limb is placed side to side with this limb and a stay suture is placed. Enterotomy is created in both limbs adjacent to the stay suture. A 60 mm linear cutting stapler is placed via the left lower 12 mm trocar through both limbs and a side‐to‐side anastomosis is created. A running absorbable braided suture is used to close the common enterotomy.

The mesenteric defect of the newly created jejunojejunostomy is approximated using a braided permanent suture in a purse‐string fashion and extended to form a second protective seromuscular layer over the closed common enterotomy.

Gastric Pouch Creation

Once the liver retractor has been positioned and secured, the prominent fat pad near the angle of His and gastroesophageal junction (GEJ) is dissected. This exposes the angle of His, and an articulating dissector is placed at that site to free the stomach from the diaphragm at the angle of His.

Next, 4 cm distal to the GEJ is measured along the lesser curve of the stomach. A window is created in the gastrohepatic ligament to enter the lesser sac. A 60 mm linear cutting stapler is entered via the right upper trocar, and a transverse transection is made in the stomach. Care is taken not to get too close to the greater curve as this prevents fluid from the remaining and excluded stomach to evacuate into the duodenum.

An articulating dissector is placed via the left lower trocar and is placed in the lesser sac towards the dissected angle of His. This is retracted laterally to flatten the stomach for the purpose of preventing too much posterior stomach in the created pouch. A 60 mm linear cutting stapler is placed via the left upper trocar and is directed for a vertical transection of the stomach towards the angle of His. Prior to firing the stapler, a 34 French tube is passed by anaesthesia into the oesophagus and advanced until it abuts the previously made horizontal staple line. This is used to guide the next staple load and prevent too much posterior stomach to be part of the pouch. Two total staple loads are used to completely create the pouch and separate it from the remnant stomach.

Gastrojejunostomy Creation

The authors choose to perform an antecolic bypass. The omentum is split to the level of the transverse colon via the ultrasonic vessel sealer. The previously created Roux limb is then found and now pulled in a clockwise fashion and brought up to the newly created gastric pouch. The ‘candy cane’ should lay with the end facing the patient’s left and the limb towards the patient’s right side.

A four‐layer gastrojejunostomy is performed. A running braided absorbable suture is used to create a posterior layer and locked but not tied at the end. An ultrasonic vessel sealer is used to create a gastrotomy and enterotomy approximately 1.5 cm in length. A second posterior layer is then performed using another absorbable braided suture in a running fashion. The first anterior layer is performed using another absorbable braided suture in a running fashion. Prior to tying this to the second posterior layer suture, the 34 French tube is advanced through the newly created gastrojejunostomy until it is in the proximal Roux limb. The anterior layer suture and the second posterior layer suture are then tied together. A second anterior layer is then performed in a running seromuscular fashion using a fourth absorbable braided suture and tied to the initial posterior layer suture. The 34 French tube is then removed.

Peterson’s defect is the mesenteric defect between the transverse colon mesentery and the Roux limb mesentery. This is approximated using a braided non‐absorbable suture in a purse string fashion.

Leak Test

An intraoperative endoscopy is performed. The assistant occludes the Roux limb distal to the anastomosis and fills the abdominal cavity with sterile water. The endoscopy is advanced into the stomach to appreciate the patency of the anastomosis, evaluate any bleeding and to appreciate a leak if present. If a leak is present, then this is located intraoperatively and repaired at that time. Once the anastomosis has been traversed and there is no leak or bleeding, the scope is removed.

Pain Management

An intraoperative transversus abdominus plane block is performed with liposomal Bupivacaine. This volume block is performed at the beginning of the operation after trocar placement. This has allowed authors to provide fewer narcotics intraoperatively and post‐operatively.

Gastrojejunostomy

There are three main approaches to performing a gastrojejunostomy. Each is depicted in the illustrations (Figure 17.4). There is a hand‐sewn anastomosis (HSA) as described in the previous section (Figure 17.4c). The second approach is a linear stapler anastomosis (LSA) (Figure 17.4b).

To perform this anastomosis with a linear stapler, a posterior running seromuscular layer is performed with an absorbable suture to line the gastric pouch and Roux limb together. An enterotomy and gastrotomy is performed on the side where the end of the Roux limb meets the gastric pouch. A linear stapler is entered into the gastric pouch and Roux limb, and the anastomosis is created. The common enterotomy is approximated using running absorbable suture of the surgeon’s choice. An anterior running seromuscular layer is then performed.

The third approach is to perform a gastrojejunostomy using a circular stapler anastomosis (CSA) with or without an OrVil (Figure 17.4a). The anvil of the circular stapler is placed through the gastric pouch wall either via a gastrotomy or using the OrVil. An abdominal wall port must be dilated in order to pass the circular stapler into the abdominal cavity. This is often performed via the right upper abdominal trocar. A wound protector is often used as well around the circular stapler. An enterotomy is performed on the end of the Roux limb and extended to allow the circular stapler to enter the lumen of the Roux limb. Once an appropriate location of the Roux limb is chosen, the male component of the circular stapler pierces through the bowel wall and connects to the female component of the anvil on the gastric pouch. The stapler is tightened, and a circular anastomosis is created. Often a 25 mm stapler is sufficient. Once the stapler is removed, the dilated fascia of the right upper quadrant trocar site must be closed, and the portion of the excess Roux limb which had the enterotomy is transected and removed.

Stay updated, free articles. Join our Telegram channel

Join