Metabolic and Bariatric Surgery

Metabolic and Bariatric Surgery

Wayne J. English

Vance L. Albaugh


Obesity is a disease that affects the entire patient, both physically and psychologically, and requires a multidisciplinary treatment approach for long-term success. Despite an increased focus on identifying and developing more effective treatments for obesity, an increased awareness of its associated comorbid conditions, and increasing costs on the healthcare system, its prevalence continues to rise. It is predicted that obesity will affect almost 50% of American adults by the year 2030.1 For some patients, bariatric surgery is a good treatment option.


Numerous clinical studies have demonstrated beneficial effects of bariatric surgery on weight loss, mostly compared with lifestyle intervention.2,3 More recent data has demonstrated that in addition to weight loss, bariatric surgery is also associated with decreased incidence of cancer and decreased risk of cardiovascular mortality compared to nonsurgical control subjects.4,5 All of these studies demonstrate the combined impact of bariatric surgery on weight loss along with decreased cardiovascular mortality.

Metabolic and bariatric surgery continues to become increasingly recognized (a 60% increase in the number of procedures performed has been noted since 2011) as the most effective and sustained treatment available for patient with moderate to severe obesity with associated medical conditions. These procedures are typically performed using minimally invasive techniques that result in short hospital stays and minimal postoperative pain. The advances the bariatric surgical field has continued to make in terms of patient safety and outcomes will no doubt continue to fuel the growth of this field.

The American Association of Clinical Endocrinologists (AACE) Task Force on Obesity in 2011 recommended that surgery is indicated in high-risk patients with obesity and that significant evidence exists to classify obesity as a disease. AACE updated obesity treatment guidelines in 2019, initially created in 2013, which was cosponsored by the American College of Endocrinology, The Obesity Society (TOS), American Society for Metabolic & Bariatric Surgery (ASMBS), Obesity Medicine Association (OMA), and American Society of Anesthesiologists and subsequently endorsed by the American Society for Nutrition (ASN), the Obesity Action Coalition (OAC), and the American Society for Parenteral and Enteral Nutrition (ASPEN). These clinical practice guidelines provide valuable information pertaining to the preoperative and postoperative nutrition and metabolic and nonsurgical care for metabolic and bariatric patients.

Despite the documented benefits of bariatric surgery, healthcare professionals (HCPs) may be hesitant to recommend these procedures to their patients due to wanting to “do no harm”; questioning the long-term effectiveness of surgery; limited knowledge about
surgery; not wanting to recommend surgery too early; and not knowing if insurance would cover surgery.6 This chapter will address some of these knowledge gaps and review primary procedures commonly performed in the United States, indications, contraindications, and psychological and other special considerations when electing to refer a patient for metabolic and bariatric surgery in the primary care setting. This chapter will also discuss risks, as well as the short- and long-term results, that can be expected for the overwhelming majority of patients. Commonly held misconceptions will also be addressed, specifically through case examples that demonstrate the decision-making during the evaluation of the patient with obesity considering metabolic and bariatric surgery.


Sleeve Gastrectomy

The vertical sleeve gastrectomy (VSG) is the most common procedure performed in the United States, representing approximately 61% of all metabolic and bariatric procedures performed in 2018. In this procedure, gastric volume is reduced by approximately 75% to 80%. This is accomplished by removing the greater curvature segment of the stomach with the pylorus being preserved. An intraluminal bougie is placed along the lesser curvature of the stomach and gastric resection begins approximately 5 to 6 cm proximal to the pylorus along the greater curvature. The stomach is then transected vertically toward, but not including, the angle of His (Figure 9.1).

Initially, the VSG was thought to be purely restrictive, but it is now known that endocrine cells responsible for producing ghrelin, a gastrointestinal hunger hormone, are primarily distributed with the stomach and are removed with the gastric segment. Subsequently, decreased hunger and improved glucose metabolism are seen after VSG. The stomach also empties faster after VSG, leading to rapid exposure of nutrients within the small intestines and earlier neurohormonal activity leading to alteration of hunger and satiety.7

When compared to Roux-en-Y gastric bypass (RYGB), the VSG has a slight safety advantage, namely avoiding the risks of bowel obstruction or marginal ulcers. Chronic nonsteroidal anti-inflammatory drugs (NSAIDs) and aspirin (ASA) use after gastric bypass are thought to cause marginal ulcers; therefore, a VSG may be a better option for patients requiring these medications. However, a low-dose ASA daily appears to be well tolerated by gastric bypass patients without major risks of marginal ulceration.8 The main disadvantages of VSG is that gastroesophageal reflux disease (GERD) may significantly worsen in approximately 30% of patients, and resolution of type 2 diabetes mellitus (T2DM) is not experienced as often with an odds ratio of 2.11, compared with 3.51 seen after RYGB.9,10

FIGURE 9.1 Vertical sleeve gastrectomy.

Roux-en-Y Gastric Bypass

RYGB involves creating a small gastric pouch measuring approximately 15 to 30 mL, causing a restriction in food intake. Additionally, malabsorption is seen due to the rearrangement of the small intestine and diversion of nutrient flow to the small intestine away from the duodenum and proximal jejunum. The jejunum, approximately 50 cm distal to the ligament of Treitz, is divided and the proximal end is reconnected to the small intestines after measuring an additional 100 to 150 cm distally. A jejunojejunostomy is created to re-establish bile and pancreatic enzyme flow into the distal small intestine. The gastrojejunostomy is then created by attaching the initial distal end divided to the gastric pouch.

The small intestine from the ligament of Treitz to the jejunojejunostomy is referred to as the biliopancreatic, or nonalimentary, limb. The segment of the intestine between the gastric pouch and jejunojejunostomy is the Roux, or alimentary, limb and the remaining small intestine from the jejunojejunostomy to the ileocecal valve is the common channel (Figure 9.2).

In addition to causing nutritional malabsorption, the gastric bypass diverts gastric secretions and bile immediately into the mid-jejunal segment resulting in
complex neurohormonal, bile acid, and microbiome alterations that affect hunger, satiety, insulin sensitivity, and glucose homeostasis.11

FIGURE 9.2 Roux-en-Y gastric bypass.

Gastric Banding

Adjustable gastric banding (AGB) is a purely restrictive procedure, creating a compression of the proximal stomach with an adjustable balloon that reduces gastric outflow. During the procedure, a retrogastric passage is created toward the angle of His and the gastric band is pulled through, wrapped around the proximal stomach, and buckled closed. Fixation sutures are placed anteriorly to secure the band into position. The tubing is pulled through one of the laparoscopic port sites and attached to the AGB subcutaneous port, which is then sutured to the rectus muscle fascia to stabilize it for future access. Changing the aperture of the band alters gastric outflow and is accomplished by accessing the port with a specialized needle to inflate or deflate the band (Figure 9.3).

Earlier studies demonstrated effective weight loss and comorbidity resolution, but it has been shown to be relatively ineffective for producing sustained weight loss and resolution of comorbidities. Furthermore, interventions to address complications or weight loss failure represented up to 77% of insurance payments related to AGB. Complication rates reported are as high as 56% and include gastric prolapse, band slippage, erosion, dysphagia, GERD, and esophageal dysmotility.12 These complications can occur any time from weeks to even many years (>5 to 10+ years) from AGB placement and can have an indolent course. For example, reflux, heartburn, and epigastric pain can slowly progress over years. Additionally, cellulitis at the subcutaneous port is many times the earliest sign of an eroded AGB, which necessitates surgical consultation for removal. A referral to the bariatric surgeon is strongly recommended if there are any questions whether symptoms are being caused by the AGB.

FIGURE 9.3 Adjustable gastric band.

The AGB was approved by the Federal Drug Administration in 2001. The procedures performed annually reached its peak in the United States in 2009, when it comprised over 40% of all metabolic and bariatric procedures. Conversely, in 2018, it represents only 1.1% of all metabolic and bariatric procedures performed and the trend appears to be steadily declining.

Biliopancreatic Diversion With Duodenal Switch

Biliopancreatic diversion with duodenal switch (BPD/DS) represented only 0.8% of all metabolic and bariatric procedures performed in the United States in 2018. While it is infrequently performed compared to the VSG and RYGB, it delivers the best results when considering durable weight loss and comorbidity resolution.9

Bile and pancreatic secretions to the distal small intestine are diverted, considerably further distally than gastric bypass. The procedure was initially performed with a partial gastrectomy and pyloric resection and
was known as the BPD. However, a pylorus-preserving technique was adopted and is now the most common technique performed today. This adaptation is known as the duodenal switch.

FIGURE 9.4 Biliopancreatic diversion with duodenal switch.

The pylorus-preserving DS procedure involves a VSG as the initial component of the procedure, but a larger sized bougie is used. The second component of the procedure involves dividing the ileum and duodenum. The distal stapled end of the ileum is then connected to the proximal stapled end of the duodenum, creating a duodenoileostomy. The proximal stapled end of the ileum is attached more distally toward the terminal ileum, creating an ileoileostomy, effectively diverting all bile and pancreatic enzymes to the distal ileum. The common channel often measures between 50 and 100 cm in length, but one of the main disadvantages of this procedure is a greater potential for electrolyte abnormalities and protein malabsorption compared to the RYGB. As a result, some surgeons have increased the common channel lengths to 200 cm or more (Figure 9.4). In comparison to other metabolic and bariatric procedures, BPD/DS is associated with the highest resolution of type 2 diabetes (T2D).9


Indications for metabolic and bariatric surgery endorsed by the National Institutes of Health (NIH) are outlined in the publication “Clinical Guidelines on the Identification, Evaluation, and Treatment of Overweight and Obesity in Adults.” The NIH specified that surgery is an effective obesity treatment option for patients with a BMI of 40 kg/m2 or 35 kg/m2 with obesity-related comorbidities, primarily hypertension, T2D, dyslipidemia, and obstructive sleep apnea ( Additionally, metabolic and bariatric surgery has been shown to be of value in patients with class 1 obesity (BMI between 30 and 35 kg/m2) and severe uncontrolled diabetes. While only a few insurance companies in the United States authorize surgery for patients in this category, it is fully supported within the European guidelines for metabolic and bariatric surgery.13 The center in which you refer your patient will know if class 1 obesity is a covered insurance benefit for your patient.

Absolute contraindications for metabolic and bariatric surgery may include, but are not limited to:

  • Uncontrolled depression

  • Uncontrolled anxiety

  • Uncontrolled bipolar disorder

  • Active substance abuse (drugs/alcohol)

  • Suicidal ideation

  • Borderline personality disorder

  • Schizophrenia

  • Significant eating disorder

  • Acute psychosis

  • Defined noncompliance with previous medical or psychological care

  • Unwilling to comply with necessary guidelines following bariatric surgery

  • Hormonal causes of obesity that can be medically treated

  • Severe cardiopulmonary disease

Some surgeons may not consider schizophrenia as an absolute contraindication, but a relative contraindication depending on whether the patient is highly functional and has readily available psychiatric and psychological support in the postoperative period. Additionally, advanced cardiopulmonary disease may be considered a relative contraindication by some surgeons. It is imperative that you refer patients with increased risk to centers that are experienced in dealing with these types of complex issues.

Relative contraindications for metabolic and bariatric surgery in which a decision to proceed with surgery will be made on an individual basis include, but is not limited to:

  • History of cancer within previous 5 years

  • Hepatic cirrhosis

  • Collagen vascular disease

  • Inflammatory bowel disease (IBD)

  • Down syndrome or intellectual disability

Decisions to operate on patients are typically based on available resources at the metabolic and bariatric center and the discretion of the surgeon. Many surgeons will consider performing metabolic and bariatric surgery on patients with cancer prior to 5 years from their diagnosis if the cancer is associated with a low recurrence risk and are no longer receiving treatment. Advanced cirrhosis with portal hypertension would be considered an absolute contraindication by most surgeons. Furthermore, severe active ulcerative colitis or Crohn’s disease may be considered an absolute contraindication by most surgeons as it is preferable to perform surgery under conditions in which symptoms are stabilized (a case study below reviews a patient with IBD).


It is essential that patients receive preoperative education, medical and psychological evaluations, and dietary preparation (Table 9.1). The preoperative evaluation must be comprehensive to identify potential treatable causes of obesity and determine factors that will increase risks for potential complications. The goal is to optimize, or prehabilitate, a patient’s health and modify risk factors to ensure surgery is performed under optimal conditions. A complete history and physical examination is performed to identify obesity-related comorbidities and indications for surgery. Routine laboratory tests may include a comprehensive metabolic profile (CMP) and complete blood count (CBC), lipid profile, thyroid function, urinalysis, prothrombin time/international normalized ratio (PT/INR), blood type, and micronutrient screening that includes iron studies, ferritin, vitamin B12, folic acid, and 25-OH vitamin D. Insurance companies may not cover all of these lab tests without the appropriate supporting diagnoses and, at a minimum, a CBC and CMP should be obtained. The nutrient screening is essential in the postoperative period and is usually covered by insurance with the supporting diagnosis of postsurgical malabsorption.

Dietary and psychological evaluations are vital in the preoperative assessment to identify possible areas of concern, such as binge eating disorder, night eating syndrome, or undiagnosed depression, which could compromise outcomes after surgery. To accomplish these goals, most insurance companies require that patients undergo a dietary and psychological assessment prior to bariatric surgery and are typically performed within the comprehensive bariatric surgical center. Furthermore, most centers have preoperative protocols that mandate attendance at one more group classes. Patients are taught how they will need to eat following surgery and learn coping strategies when faced with behavioral and dietary challenges. Understanding your patient’s
goals is important to the overall success after surgery as there may be discrepancies between a patient’s weight loss goals and the realistic weight loss potentially realized after surgery. Numerous factors may influence a patient’s ability to achieve an optimal result after surgery, including psychological profiles as described above, comorbidities, medications that may lead to suboptimal weight loss, age and metabolism, body composition, and energy balance. A comprehensive metabolic and bariatric surgery center is committed to identifying variations in any of these factors which may predispose a patient to insufficient weight loss outcomes or weight regain after experiencing a satisfactory weight nadir.

TABLE 9.1 Preoperative Checklist


  • Comprehensive history and physical

  • Identify treatable causes of obesity and treat, if present

  • Look for inclusion criteria meeting the National Institutes of Health and insurance criteria

  • Note contraindications for surgery, if present

  • Document medical necessity for surgery including obesity-related comorbidities, weight, body mass index

  • Assess patient level of commitment

  • Identify history of cancer, if present

  • Assess for nicotine use (smoking, vaping, patch, chewing, etc.) and require nicotine cessation; refer for counseling if needed

  • Routine labs

  • Complete blood count and comprehensive metabolic profile, including fasting blood glucose and liver function tests, are routine during initial consultation

  • Other recommended labs, if indicated, include thyroid function, lipid profile and glycated hemoglobin, urinalysis, prothrombin time, and partial thromboplastin time

  • Type and screen just prior to surgery

  • Additional nutrition labs, if indicated

  • Iron, TIBC, ferritin, vitamin B12, folic acid, 25-OH vitamin D, parathyroid hormone levels

  • Dietary evaluation

  • Educate about dietary behavior required postsurgery

  • Educate about potential for vitamin and mineral deficiencies in the postoperative period

  • Review body composition and energy balance

  • Set weight loss goals and manage discrepancies

  • Psychological evaluation (includes lifestyle assessment)

  • Assess healthy eating index and identify binge eating and night eating disorder, and treat if present

  • Assess overall mood and identify untreated depression, and treat if present

  • Assess for substance and alcohol abuse, and treat if present

  • Identify medications that may contribute to suboptimal weight loss

  • Assess overall support structure

  • Identify need for further behavioral support and counseling

  • Cardiology evaluation, if indicated

  • Electrocardiogram

  • Echocardiogram

  • Stress testing

  • Cardiac catheterization

  • Optimization of hypertension

  • Pulmonary evaluation, if indicated

  • Sleep apnea screening

    • STOP-BANG questionnaire

    • Epworth Sleepiness Scale

  • Optimization of COPD, asthma

  • Gastrointestinal (GI) evaluation, if indicated

  • Esophagogastroduodenoscopy

  • Upper GI contrast study

  • Helicobacter pylori testing

  • Gallbladder ultrasound

  • Colonoscopy

  • Endocrine evaluation, if indicated

  • Optimization of diabetes mellitus

  • Glycated hemoglobin

  • Dexamethasone test

  • 24-Hour urinary cortisol

  • Thyroid-stimulating hormone

  • Testosterone

  • Dehydroepiandrosterone

  • Insurance prerequisites, if applicable

  • Confirm patient has benefits covering metabolic and bariatric surgery

  • Preoperative weight management documentation

  • Documented weight loss prior to surgery

Cardiopulmonary evaluation is often required in patients interested in having metabolic and bariatric surgery. Cardiology evaluations for risk assessment should follow standards of practice for perioperative evaluation and management of patients undergoing noncardiac surgery, which may include electrocardiogram, echocardiogram, stress testing, and cardiac catheterization as indicated.14 Patients with previous history of unprovoked deep vein thrombosis or pulmonary embolism should undergo a formal hematology evaluation to rule out a hypercoagulable state. Pulmonary clearance should be obtained in patients with significant chronic obstructive pulmonary
disease in order to optimize patients prior to surgery. Chest x-rays are not routinely obtained unless clinically indicated. A sleep study is indicated in patients with significant snoring, witnessed apnea episodes, morning headaches, daytime sleepiness, and significant oxygen desaturation on overnight pulse oximetry. Screening using the Epworth Sleepiness Scale or STOP-BANG questionnaire may help to identify at-risk patients to refer for an overnight polysomnogram (Table 9.2).15,16 Patients newly diagnosed with obstructive sleep apnea should implement continuous positive airway pressure (CPAP) treatment to optimize their pulmonary status for at least 1 month prior to surgery.

TABLE 9.2 Epworth Sleepiness Scale and STOP-BANG Questionnaire Used for Obstructive Sleep Apnea Screening

Epworth Sleepiness Scale

0-10: Normal range

10-12: Borderline

12-24: Abnormal

Use the following point tabulation for each question

0: No chance of dozing

1: Minimal chance of dozing

2: Moderate chance of dozing

3: High chance of dozing

How likely are you to doze off or sleep during the following?

1. Sitting or reading?

2. Watching television?

3. Sitting inactive in a public space?

4. As a passenger in a car for an hour without a break?

5. Lying down to rest when circumstances permit?

6. Sitting and talking to someone?

7. Sitting quietly after lunch without alcohol?

8. In a car, while stopped for a few minutes in traffic?

STOP-BANG Questionnaire

0-2: Low risk

3-4: Intermediate risk

5-8: High risk

Use the following point tabulation for each question

0: No

1: Yes

S: Snore loudly?

T: Feel tired during the day?

O: Observe apnea while sleeping?

P: Treated for high blood pressure?

B: Body mass index ≥35 kg/m2

A: Age ≥50 years

N: Neck circumference

  • Male ≥17 inches

  • Female ≥16 inches

G: Gender—male

Gastrointestinal (GI) evaluations are often obtained as clinically indicated. Some centers routinely obtain esophagogastroduodenoscopy (EGD) on all patients, while others are more selective and perform preoperative EGDs only when indicated, such as a history of dyspepsia, reflux, dysphagia, or previous ulcer disease. Helicobacter pylori screening is not routinely performed but should be considered in regions of high prevalence and treated with triple antibiotic regimen if tested positive. A gallbladder ultrasound may be obtained routinely by some surgeons but is usually ordered selectively as clinically indicated. If cholelithiasis is present, surgeons may elect to perform a cholecystectomy concurrently with the metabolic and bariatric procedure.

Endocrine evaluations for patients with severe uncontrolled diabetes despite taking multiple medications should be considered since hyperglycemia is associated with increased risk for infection, poor wound healing, and extended hospitalization. A preoperative glycated hemoglobin level of ≤8% should be achieved, if possible. A serum thyroid-stimulating hormone level should be obtained if clinical evidence of hypothyroid is present and treated accordingly. Screening for PCOS and Cushing syndrome should be only be conducted if clinically indicated.


The principal goal for the preoperative psychosocial evaluation in patients preparing for metabolic and bariatric surgery is to ensure patients are committed to the necessary lifelong changes after surgery, but most importantly to identify those with increased risk for potential relapse of preexisting depression or behavioral eating disorders and subsequently address potential issues that may contribute to a poor postoperative outcome.

Patients with class 2 (BMI 35.0 to 39.9 kg/m2) and 3 (BMI ≥40 kg/m2) obesity often carry a diagnosis of depression, anxiety, and other stress-related conditions including eating disorders. They also often battle with body image and poor self-esteem issues. The psychologist can help patients develop coping strategies to ensure a more positive outcome after surgery. To underscore the importance of having continued behavioral health services available in the postoperative period, patients with a diagnosed psychological health disorder were noted in one study to have 34% increased odds of 30-day readmission when compared with patients who did not have a mental health disorder diagnosis. The odds were even greater (46%) in patients diagnosed with depression or bipolar disorder. Careful consideration must be given to patients with depression taking antidepressants who undergo an RYGB procedure as medication malabsorption may exacerbate symptoms.

An awareness of the potential for excessive alcohol and illicit substance use following surgery is critical as patients may seek substitutes to attain the dopaminergic reward previously achieved with food. Obesity-induced dysregulation of dopamine reward processing, in theory, can result in compensatory overeating, and this process is thought to be reversed after RYGB.

Finally, there are some studies suggesting that there are potentially increased risks for self-harm and suicide after metabolic and bariatric surgery. However, other studies argue the increased risks were already present prior to surgery and that patients need to be monitored carefully in the postoperative period.17 A number of psychosocial issues that might potentially attribute to suicide include the lack of improvement in quality of life, physical limitation, sexual dysfunction, relationship, or low self-esteem. Additional factors to consider include a prior history of being abused or perceived postoperative failure due to insufficient weight loss or weight regain.


Preoperative medical weight management requirements with mandatory weight loss in the preoperative period is often imposed by many insurance companies, and patients may be denied surgery benefits if weight loss is not observed during this time period. However, there is no evidence to support that insurance-mandated preoperative weight loss results in decreased complication rates or improved outcomes after surgery and these practices should be abandoned as it causes unnecessary delays in receiving treatment, contributes to patient attrition, and leads to the progression of obesity-related comorbidities.18 A preoperative very low calorie diet (VLCD) treatment is prescribed by many surgeons for up to 2 to 4 weeks prior to surgery to achieve substantial liver size reduction, which allows for better exposure of the gastroesophageal region during surgery. A 5% to 20% reduction in liver volume has been demonstrated in patients completing a preoperative VLCD. Additionally, one study demonstrated that greater than 3.5% total weight loss in patients completing VLCD 4 weeks preoperatively was associated with significantly greater weight loss at 12 months postoperatively compared with patients who lost less weight.19


In 2018, approximately 252,000 metabolic and bariatric procedures were performed in the United States, noting a 60% increase in the number of procedures performed compared with 2011. VSG is currently the most common procedure, representing 61% of procedures performed in the United States. The number of RYGB and AGB procedures performed annually has been steadily declining since 2011 and currently account for 17% and 1.1% of all procedures, respectively. But there was slight increase in RYGB noted in 2017 and 2018 in which RYGB represented approximately 17% of all procedures. Revisions of previous metabolic and bariatric procedures, which will be briefly reviewed later in this chapter, continue to rise as increasing numbers of AGB are removed and may soon surpass the number of RYGB procedures being performed annually (Figure 9.5).

FIGURE 9.5 Metabolic and bariatric surgery procedure trends: 2011-2018. RYGB, Roux-en-Y gastric bypass; BPD/DS, biliopancreatic diversions with duodenal switch.


Metabolic and bariatric surgical procedures are now among the safest performed in the United States. This extraordinary achievement is principally due to the introduction of laparoscopic techniques and national accreditation with a long-standing emphasis on patient safety and continuous quality improvement efforts.

Leading the way in quality improvement efforts is the Metabolic and Bariatric Surgery Accreditation and Quality Improvement Program (MBSAQIP), a joint effort between the American College of Surgeons (ACS) and the American Society of Metabolic and Bariatric Surgery (ASMBS) developed standards that are designed to optimize patient safety and requires centers to enter patient demographic and outcomes data into a national data registry. This data registry allows a comprehensive analysis of safety and outcomes data on a large scale in which centers can use as an opportunity to improve structural and process deficiencies. (See Clinical Highlights for information on how you can refer your patient to an accredited center.)

Only gold members can continue reading. Log In or Register to continue

Stay updated, free articles. Join our Telegram channel

Aug 25, 2021 | Posted by in GENERAL | Comments Off on Metabolic and Bariatric Surgery

Full access? Get Clinical Tree

Get Clinical Tree app for offline access