Surgical Options In the Treatment of Severe Obesity

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Continuing Education Activity

Obesity is a worldwide pandemic, resulting in comorbidities, socioeconomic costs, and reduced quality of life. Severe obesity, those with a BMI over 40 kg/m^2, is an indication for a patient to undergo bariatric surgery. Main surgical procedures performed have elements of restriction, malabsorption, or a combination of both mechanisms. This activity reviews the evaluation and surgical treatment of severe obesity and highlights the role of the interprofessional team in evaluating and treating this condition.

Objectives:

  • Identify the requirements for a patient to undergo bariatric surgery.
  • Review the bariatric surgeries indicated for severe obesity endorsed by the American Society of Metabolic and Bariatric Surgeons.
  • Summarize the risks and benefits of bariatric surgery.
  • Describe the extensive preoperative assessment by the interprofessional team that a patient must undergo before bariatric surgery.

Introduction

Obesity is a chronic illness that affects children, adolescents, and adults globally. According to the World Health Organization (WHO), approximately 35% of adults and 17% of children are obese in the United States. Worldwide, there are 650 million obese adults and 42 million obese children under the age of 5. The definition of obesity is a body mass index greater than or equal to 30 kg/m2 with further delineation into classes.[1] 

Obesity has a psychosocial impact and an increase in medical and economic complications. With increased adipose tissue deposition, there is an increase in comorbid conditions and medical complications. These comorbidities include Type 2 diabetes mellitus, cardiovascular disease, cerebrovascular accidents, malignancies like colon, breast, and uterine cancers, osteoarthritis, obstructive sleep apnea, major depressive disorder, and liver disease. A positive correlation is seen with increased complications and increased fat deposition. Weight loss decreases medical complications such as hypertension and Type 2 Diabetes Mellitus. From a socioeconomic standpoint, treating obesity and its associated complications results in the United States alone expending more than $200 billion per year, which equals more than 20% of US health expenditure overall. Costs also are associated with missed work and a decreased life expectancy. When considering approaches to weight loss, medical and behavioral modifications may be ineffective for a plethora of obese patients. Patients who undergo bariatric surgery have lower long-term mortality rates than matched controls who do not undergo bariatric procedures.[2] 

Metabolic or bariatric, derived from the Greek words "baros," meaning weight, and "iatrikos," meaning medical, surgery has increased worldwide. In 2018, approximately 394,431 bariatric procedures were performed according to the International Federation of Surgery of Obesity and Metabolic Diseases. When discussing bariatric procedures, it is prudent to discuss obesity classifications. Class 1 is defined as a BMI of 30 to <35. Class 2 is defined as a BMI of 35 to <40. Class 3, which can be categorized as "severe obesity," is defined as a BMI greater than or equal to 40. The National Institute of Health Consensus Development Panel in 1991 outlined the indications for surgical management of class 3, severe obesity, which the American Bariatric Society later revised in 2004.[2]

Candidates for bariatric surgery include adults with a BMI greater than or equal to 40 kg/m^2 without comorbid conditions or adults with a BMI between 35 to 39.9 kg/m^2 with at least one serious comorbidity. These comorbidities include diabetes mellitus, obstructive sleep apnea, hyperlipidemia, obstructive hypoventilation syndrome, hypertension, Pickwickian syndrome, non-alcoholic fatty liver disease, non-alcoholic steatohepatitis, pseudotumor cerebri, gastroesophageal reflux disorder, asthma, venous stasis disease, as well as debilitating arthritis. If a patient has been disqualified from another surgery due to obesity, such as surgery for osteoarthritis or ventral hernia repair, this serves as the qualifying serious comorbidity for bariatric surgery consideration.[3]

Issues of Concern

Preoperative Assessment

When considering a patient for bariatric surgery, if the qualification standards discussed above are met, a preoperative assessment is required. A comprehensive evaluation is utilized, and an interprofessional team is assembled. An interprofessional team that includes behavioral health professionals, including psychiatrists or psychologists, nutritionists, medical bariatric specialists, nurse specialists, and skilled surgeons, are utilized. The preoperative assessment includes psychological, cognitive, emotional, current social situation, and anesthetic risk components.

The preoperative psychological assessment is used to identify prior diagnosed psychiatric disorders to properly determine if an operative candidate has the ability and willingness to make the required lifestyle changes for sustainable weight loss. Any identified significant psychological disorders, including antisocial personality disorder, major depressive disorder, bipolar disorder, should be treated in the preoperative period to decrease the challenges to weight loss initiatives and postoperative psychological complications. According to the American Society of Metabolic and Bariatric Surgeons, there are suggestions for the preoperative assessment to include behavioral, health-related risk behaviors, cognitive or emotional, and current life situation components.[4] 

The behavioral component serves to determine the role of food in a patient's current lifestyle and determine if their extent of eating is driven by behavioral and environmental stimulation. The aim is to identify any prior attempts at weight loss. This may be a multitude of dietary restrictions that may or may not include the addition of exercise.

An assessment for eating disorders is performed. Examples of such would include binge eating, nighttime eating, overeating, or grazing. Maladaptive eating styles can have a stress-related pattern, which is important to identify preoperatively. Physical activity levels should be evaluated. The patient should have the ability to incorporate an exercise regimen in the postoperative state as they are recovering. The provider should encourage them to initiate an exercise program before surgical intervention.

History of or current substance abuse should be assessed in these patients. The patient should have tools for self-management, rational judgment, and coping skills at hand. The need for self-medication should also be explored further with the psychological assessment. Any health-related risk behaviors could include impulsive or compulsive behavior patterns. These will be evident with patient compliance with medical treatment of comorbid disease, likely indicating compliance with postoperative management.

Patient emotional, cognitive intellect should be assessed; they should have the capacity to understand the type of procedure to be performed, the risks associated, benefits, and behavioral changes that are key to weight loss. Any deficits should be addressed, and counseling measures should be taken to help the patient develop coping skills or illuminate maladaptive behavior. An appropriate amount of time should be taken to educate the patient on the procedure, not only on obtaining consent but also on the risks of obesity. This cognitive assessment should include both knowledge of the procedure at hand and alternatives.[4]

The patient's current lifestyle should be evaluated for any chaos or triggering life stressors that may negatively impact balanced meals or a regular exercise routine. Stressors are not necessarily a contraindication to surgical intervention, but if unrecognized or untreated, they may lead to recidivism or result in mental illness in the postoperative period. Stressors at home like discourse with a spouse or child, loss of a job, death of a loved one should be investigated. They should be addressed and offered appropriate counseling. The patient should have social support at home as utilization of such is related to increased healing and effective weight loss. The patient's motivation, whether it is a primary one of health benefits or other reasons, can help in guiding their postoperative course. Expectations, including social, emotional, and lifestyle-wise, should be evaluated to determine if realistic. These will also help determine if the patient is genuinely committed to making permanent changes and adherence to postoperative guidelines to improve their health.

A nutritionist and dietitian must be part of the multidisciplinary team. There should be a tailored nutritional plan for before, perioperative, and postoperative to bariatric surgery. The patient should be educated on reading the nutritional content of foods, appropriate portion sizes, alternatives to snacks and drinks, healthy preparation of food, and how to shop for the household. The medical assessment includes a complete history and physical examination. This is utilized to assess for comorbid illnesses such as diabetes mellitus, obstructive sleep apnea, hypertension, and restrictive lung disease. When considering a patient for a bariatric procedure, a comorbid condition is likely identified before the patient falls in the class 2 category of obesity. Many patients may have undiagnosed elements related to their obesity, like obstructive sleep apnea. Screening tools like questionnaire methods like the STOP-Bang are utilized but then confirmed using polysomnography.[4]

If a patient is determined to have moderate to severe obstructive sleep apnea, it is pertinent to obtain pulmonary function tests. A cardiac risk assessment should be performed. A patient with a history of weight loss medications should undergo an echocardiogram. Fenfluramine has a known side effect of cardiac valvular disease. Any patient with a history of gastroesophageal reflux disorder, peptic ulcer disease, a history of an H. pylori infection, or hiatal hernia should undergo an esophagogastroduodenoscopy to rule out any active disease. If a patient is suspected of having nonalcoholic fatty liver disease, with evidence of hepatomegaly on physical examination, liver function tests should be obtained. Radiographic imaging should also be obtained, whether ultrasound or CT scan. A biopsy may be needed to evaluate for cirrhosis as well. As obese patients may have a long-standing history of hypertension or diabetes mellitus, renal function may be impaired, requiring serum chemistries, like a blood urea nitrogen and creatinine level. The hemoglobin A1c should be obtained as part of the preoperative workup for all patients.

A musculoskeletal examination should be performed to evaluate for cervical osteoarthritis. Cervical osteoarthritis will affect positioning in the operating room for bariatric surgery. Any woman of childbearing age should be seen by an OB/GYN to discuss birth control options. Within the 18-to-24-month operative period, pregnancy is discouraged. The discussion with the OB/GYN should include the type of procedure performed. If a patient is undergoing a malabsorptive bariatric procedure, the patient may not adequately absorb certain birth control pills, thus making the form of contraceptive ineffective. If a patient has a hypercoagulable state or a history of venous thromboembolism, hematology/oncology should be consulted. They can help determine the duration of thromboprophylaxis in the perioperative period. An anesthetic risk assessment should be performed as obese patients tend to have respiratory and cardiovascular changes that can impact the delivery of general anesthesia and preoperative anesthesia.[5]

Contraindications

When considering a patient for bariatric procedures, contraindications should be assessed. A bariatric procedure is not an indication for glycemic control, lipid control, or cardiovascular risk reduction independent of the noted BMI parameters. Patients identified with bulimia nervosa are not candidates for bariatric surgery. Advanced age, identified as greater than 65 years old, is controversial and surgeon specific. Pediatric patients under 18 years of age are becoming more common. The American Academy of Pediatrics endorsed patients with severe obesity being evaluated for bariatric procedures. Pre-existing medical or psychological conditions that preclude surgery include any uncontrolled psychosis or major depressive disorder, uncontrolled eating disorder, abuse of any drug and/or alcohol, any severe cardiac disease with prohibitive anesthetic risks associated, severe coagulopathy, or a patient inability to comply with nutritional requirements like lifelong vitamin replacement adherence.[5]

Bariatric Procedures for Management of Severe Obesity

Bariatric mechanisms for weight loss include a combination of volume restriction, nutrient malabsorption, and intestinal hormone alteration. The combination of methods affects satiety, absorption of nutrients and calories, and insulin sensitivity. A bariatric procedure along with behavioral modifications can help a patient achieve but sustain meaningful weight loss. A patient who undergoes bariatric surgery should undergo lifelong surveillance. From 1993 to 2016, approximately 2 million patients in the United States alone underwent bariatric surgery.[5]

The field of bariatric surgery has evolved from an exclusively open procedure like an open gastric bypass or vertical banded gastroplasty to now 98% laparoscopic surgery like a sleeve gastrectomy or a gastric bypass. Complications and mortality rates have reduced from approximately 11.7% and 1%, respectively, in 1998 to 1.4% and 0.04% in 2016.[6]

The mechanism of weight loss typically falls into one of two categories, but some procedures have both components. These mechanisms include malabsorption and restriction. There is a contribution of neurohormonal effects on the regulation of energy balance and hunger control. Key hormones include leptin and ghrelin. Examples of restrictive procedures include the vertical banded gastroplasty, laparoscopic adjustable gastric band, and sleeve gastrectomy. Malabsorptive procedures include jejunoileal bypass, biliopancreatic diversion (BPD), or biliopancreatic diversion with duodenal switch. A combination procedure commonly performed is the Roux-en-Y gastric bypass.[6]

Restriction

The purpose of a restrictive procedure is to reduce the stomach reservoir capacity, thus limiting the caloric intake. A restrictive procedure can be performed via resection, creation of a proximal gastric outlet, or bypass. Both vertical banded gastroplasty and laparoscopic adjustable gastric banding are purely restrictive procedures and do have similarities in anatomical configurations. When discussing these procedures, the mechanism of action is by limiting solid food intake secondary to the reduced stomach size but leaving the absorptive functions of the small bowel intact. Both procedures, the vertical banded gastroplasty, and the laparoscopic adjustable gastric band, have been largely abandoned. The sleeve gastrectomy is a main restrictive procedure likely due to more successful hormonal effects on hunger control.[6]

There are investigational procedures like aspiration therapy or intragastric balloon placement, which restrict food gradually with modest weight loss. These may have higher recidivism rates than the contemporary bariatric procedures performed.

Malabsorption

The malabsorptive mechanisms of weight loss reduce the effectiveness of nutrient absorption by reducing the absorptive length of the small bowel. These procedures can be accomplished either by a bypass of the small intestine absorptive surface area or by the end of diversion of biliopancreatic secretions, which facilitate absorption.[5] Jejunoileal bypass and BPD are examples of malabsorptive procedures. These procedures can have profound effects on weight loss, but this is dependent on the length of the functional small intestine segment. These procedures can have significant metabolic complications like protein-calorie malnutrition or micronutrient deficiencies as the functioning small bowel is affected.

Combination

A combination procedure can also serve as an option for patients. Examples of such include the Roux-en-Y gastric bypass as well as BPD with duodenal switch. Roux-en-Y gastroplasty functions by creating a smaller gastric pouch that limits oral intake with small bowel reconfiguration providing the additional mechanism for weight loss. It creates dumping physiology as well as positive hormonal changes and has mild malabsorptive properties.[5] Effects on hunger are secondary to hormonal changes.

Approach

When considering technical approaches for surgical intervention, laparoscopic versus open surgical are options. The laparoscopic approach improves both recovery and mortality; thus, it is more commonly utilized. The Nationwide Inpatient Sample from 2003 to 2008 documented data that the proportion of performed laparoscopic procedures increased from 20% in 2003 to 90% in 2008. The laparoscopic approach offers advantages like reducing blood loss, lower incidence of wound infection, incisional hernia, faster recovery, and shorter hospital stay. Important considerations should be taken given the patient's size as laparoscopic instruments, and trocar lengths may be limiting factors for a laparoscopic approach. Prior abdominal surgery is not a contraindication for a laparoscopic approach in a bariatric procedure.[6]

Clinical Significance

Contemporary Procedures Endorsed by the American Society of Metabolic and Bariatric Surgeons

Roux-en-Y gastric bypass is now one of the most performed procedures by bariatric surgeons. The surgery is characterized by creating a small, less than 30 mL proximal gastric pouch that is then divided and separated from the distal stomach. This is anastomosed to a Roux limb of the small intestine that is approximately 75 to 150 cm in length. Both the small created gastric pouch and narrower anastomotic outlet work in tandem to restrict caloric intake while the major digestive and absorptive process occurs in the common channel where pepsin, intrinsic factor, gastric acid, pancreatic enzymes, and bile are all mixed with ingested food particles.

The small intestine is divided at approximately 50 to 150 cm distal to the identified ligament of Tretiz. This division of the small bowel then creates a proximal biliopancreatic limb that is utilized to transport secretions from the gastric remnant, pancreas, and liver. The roux limb, also known as the elementary limb, is then anastomosed to the newly created gastric pouch that drains consumed food. The cut end of the biliopancreatic limb and the Roux limb is anastomosed at approximately 75 to 150 cm distal leave from the gastrojejunostomy.[7]

The major digestive and absorptive process of nutrients occurs in the resultant common channel where the pancreatic enzymes and bile mixes with the ingested food. The smaller created stomach reservoir initially is only able to hold the capacity of approximately one ounce of food, which results in early satiety. Over time, the stomach reservoir stretches and can hold up to about one cup of food.

The gastrojejunostomy created by this procedure is associated with dumping physiology, thus causing nausea, diaphoresis, lightheadedness, abdominal discomfort, and diarrhea with the ingestion of a high sugar meal. This becomes a negative conditioning response if a patient consumes a high sugar diet in the postoperative period. The optimal Roux limb length has a balance between weight reduction and minimizing complications of absorption. Increasing this length can lead to more severe malabsorption as lengthening does shorten the common channel where the processes of major digestion and absorption of ingested nutrients occur. If surgeons do not create a Roux limb length that is longer than approximately 150 cm, "distalization" can be used to make a longer biliopancreatic limb length with a reduction in length of the common length has been utilized in patients who have had an inadequate weight loss response following a standard Roux-en-Y gastric bypass. Still, there are risks for metabolic complications to consider.[7]

Important hormones involved in regulating food consumption and satiety include leptin, which signifies satiety, and ghrelin, which indicates hunger. Ghrelin is a peptide hormone secreted in the foregut and released in a pulsatile fashion. The normal release of this hormone is inhibited by gastric bypass due to the foregut bypass configuration, which is seen in laparoscopic sleeve gastrectomy. The reduction in ghrelin levels contributes to the loss of appetite typically seen in the postoperative Roux-en-Y gastric bypass period. Other notable hormones like cholecystokinin and glucagon-like peptide-1 are upregulated after a Roux-en-Y procedure and may promote an anorexic state. Two years following the Roux-en-Y gastric bypass, the expected excess weight loss is approximately 70%.

Sleeve Gastrectomy

A sleeve gastrectomy includes partial gastrectomy where the greater curvature of the stomach is resected, and a tubular-shaped stomach is created. This procedure was initially offered to patients with "super severe obesity" with a BMI greater than 60 kg/m². Of note, this was the most performed bariatric surgery worldwide and in the United States in 2016. This procedure is technically easier to perform than a Roux-en-Y gastric bypass as it does not require multiple anastomoses. This procedure is safer with the reduction of the risk of internal hernias as well as protein and mineral malabsorption. The antrum is divided at approximately 2 to 6 cm away from the pylorus. A 32 to 40 French bougie is used to create the sleeve.[8] The newly created tubular stomach has a restrictive property and is resistant to stretching due to the absence of the stomach fundus and reduction of ghrelin-producing cells. The sleeve gastrectomy is characterized as a restrictive procedure, but gastric motility changes may affect weight loss.

The sleeve gastrectomy procedure creates a stomach that is a high-pressure organ with sphincters at the proximal and distal ends, which makes leaks more frequent compared to Roux-en-Y gastric bypass. Sleeve gastrectomy does have a higher incidence of gastroesophageal reflux disease secondary to the high-pressure nature. The weight loss mechanism involved in sleeve gastrectomy is not only restrictive as there is evidence of neurohormonal changes caused. Grehlin levels are reduced, promoting fewer feelings of hunger. Peptide YY levels and glucagon-like peptide-1 levels increase and improve insulin resistance and glycemic control. At the two-year mark, the expected excess weight loss is about 60% following a sleeve gastrectomy.[9]

Biliopancreatic Diversion with Duodenal Switch

This procedure is a variant of a biliopancreatic diversion procedure. This procedure involves a partial sleeve gastrectomy but the preservation of the stomach pylorus and the creation of a Roux limb and short common channel. This procedure does pose significant long-term absorptive risks, so this is implemented for patients with very severe obesity, whose BMI is greater than 50 kg/m^2.[9]

The indication for this surgery is unclear as some surgeons do prefer to perform this for super morbidly obese patients, while other surgeons tend to reserve this for a revisional procedure. This procedure results in the malabsorption of both fats and starches. It has been shown to have higher rates of protein malnutrition, diarrhea, stomach ulceration, and anemia, which has limited its usage. It is important to note that the biliopancreatic diversion with a duodenal switch is a technically challenging operation with higher complication rates.[10]

The biliopancreatic diversion procedure with duodenal switch is a variant of the biliopancreatic diversion procedure, so it is important to touch on the original procedure. The original procedure divides the duodenum from the pylorus and then removes the pylorus, followed by dividing the ileum. The distal aspect of the ileum is anastomosed to the remnant stomach and proximal ileum. The biliopancreatic limb, which receives the output from the liver, pancreas, the duodenum, is anastomosed to the terminal ileum at approximately 50 to 100 cm distal to the ileocecal valve. The addition of the duodenal switch procedure involves the creation of sleeve gastrectomy, but with preservation of the stomach pylorus. A Roux limb is created with a short common channel as well.[10]

The differentiating factors between these procedures are in the duodenal switch, the portion of the stomach removed, and the preservation of the pylorus, which has similarities to a sleeve gastrectomy. The duodenal switch procedure allows for more antegrade flow from the biliopancreatic limb and thus avoids the feared complication of stasis in the jejunoileal bypass. There is also a lower incidence of both stomach ulceration and diarrhea. The weight loss mechanism is a combination of both malabsorptive and restrictive. At the two-year postoperative mark, the estimated weight loss excess is 70 to 80%.[10]

Single-Anastomosis Duodenoileal Bypass with Sleeve Gastrectomy

The procedure of a single anastomosis duodenoileal bypass with sleeve gastrectomy is essentially a variant of the biliopancreatic diversion with duodenal switch operation. A transected portion of the duodenum is anastomosed to a loop of the distal small intestine, which differs from the Roux-en-Y-like configuration used in the biliopancreatic diversion procedures. Hence, there is only one single anastomosis. The reasoning for the development of this single anastomosis procedure was to reduce both the complexity and risks of performing a Roux-en-Y with a smaller diameter distal bowel and a necessity for two anastomoses. This procedure has been endorsed as an appropriate primary metabolic bariatric surgery by the American Society for Metabolic and Bariatric Surgery.[10]

There is some controversy for the utilization of this procedure after inadequate weight loss post-Roux-en-Y gastric bypass or a sleeve gastrectomy. The procedure involves the creation of a sleeve first. A sleeve-like gastric pouch is created. Next, the duodenum is divided just after the pylorus. A single anastomosis is created between the sidewall of the distal small intestine and the end of the sleeve-like gastric pouch and duodenum. The gastric pouch anastomosis to the distal ileum is a single end-to-side anastomosis. The common channel length is typically no less than 300 cm, but there is a variation with the sleeve gastrectomy sizes anywhere from 34 to 54 French. The weight loss mechanism involved in this procedure is restrictive, malabsorptive, and hormonal. In the two-year postoperative period, excess weight loss has shown to be approximately 85%.[11]

In non-randomized comparative studies, this procedure achieved similar weight loss as the Roux-en-Y gastric bypass, sleeve gastrectomy, and biliopancreatic diversion with duodenal switch. The patients who underwent the single anastomosis duodenoileal bypass had fewer anastomotic complications, internal hernias, volvulus, and bowel obstructions. This is likely secondary to the one fewer anastomosis involved in the procedure. This procedure did have a higher risk of chronic diarrhea, even with a common channel measuring 300 cm.[11]

With a common channel being less than 300 cm, malnutrition rates were high. The reasoning why the biliopancreatic diversion with duodenal switch can have a common channel of about 150 to 200 cm, but the single anastomosis duodenoileal bypass has improvements with a 300 cm common channel, is unclear.[12]

Intragastric Balloon

An intragastric balloon is a soft, saline-filled balloon that is utilized to induce the feeling of satiety as well as a restriction. This has been advocated more as a bridge to definitive surgical intervention. The usage of such is approved for patients who fall in the class one category of obesity (BMI 30 to 34.9 kg/m^2). These intragastric balloons are indicated for patients who have failed prior attempts for weight loss through diet and exercise alone. These balloons are typically inserted in an endoscopic fashion and filled with approximately 400 to 700 mL of saline. The maximum duration of placement is for six months due to a significant increase in leak rate beyond this time. If the balloon deflates, it can migrate into the small bowel and cause subsequent obstruction, which requires a second endoscopic procedure for retrieval. The weight loss mechanism for an intragastric balloon is purely restrictive, with weight loss contingent upon adherence to lifestyle changes and compliance. As patients with severe obesity do not fall under the indications for intragastric balloons, this article will not go into further detail.

Investigational Procedures

Currently, there are investigational procedures not endorsed by the American Society of Metabolic and Bariatric Surgery. These procedures involve a single anastomosis gastric bypass, aspiration therapy, endoscopic sleeve gastroplasty, endoscopic gastrointestinal bypass device, laparoscopic gastric plication, and bariatric arterial embolization.[13] These are investigational procedures, which will not be discussed in detail. The primary focus of this article is a surgical intervention for severe obesity discussed above.

Other Issues

Primarily Revisional Procedures

Band revisions are utilized in patients who fail the band or health complications that necessitate removal. Options for a failed band procedure can include conversion to a Roux-en-Y gastric bypass, sleeve gastrectomy, or biliopancreatic diversion with a duodenal switch. The band can also be replaced. Revisional timing is important due to inflammation or fibrosis of gastric tissue due to the presence of the band. A staged approach can be utilized with the band being first removed and then, after an 8-to-12-week time, can be converted to another bariatric procedure.[13]

Roux-en-Y gastric bypass revision may be required due to anatomical reasons postoperatively. When discussing the failure of this procedure, an anatomical reason may be due to enlargement of the gastric pouch and remnant stomach, which reduces the restrictive sense. A complication could also be the formation of a fistula between the remnant stomach and gastric pouch. Another factor to consider could be an enlargement of the created anastomosis between the Roux limb and gastric pouch. These could all serve as factors that would lead to weight recidivism secondary to an anatomical reason, other than just non-compliance of the patient to a healthier lifestyle.

The above-listed condition could indicate for the surgeon to recreate the gastrojejunal anastomosis and gastric pouch. The lengthening of the biliopancreatic limb via the process of "distalization" or revision of the jejunojejunostomy anastomosis has gained some traction if the gastric pouch is intact, but the patient has regained significant weight. This limb is lengthened without sacrificing too much of the common channel, which has positive results in renewed weight loss and comorbidity control. It is important to note that the indication to re-operate for weight regain still follows the same criteria as the initial procedure discussed above.

Sleeve gastrectomy has shown that the durability is not as good as a Roux-en-Y gastric bypass over five years. Theoretically, the sleeve could expand over time, thus losing the restrictive mechanism for weight loss. Although data support that sleeve gastrectomy is comparable to Roux-en-Y gastric bypass procedures at three years, sleeve revisions still are performed for patients suffering from intractable reflux disease amidst satisfactory weight loss progress.[14]

Procedures that have been rarely performed or become obsolete include the laparoscopic adjustable gastric banding, jejunoileal bypass, vertical banded gastroplasty, and vagal blockade. Because these procedures are not utilized often or have more historical purposes, they will not be further discussed.

Postoperative Metabolic Effects

The metabolic effects of bariatric surgery are also well studied. The definition for metabolic syndrome is the concurrent risk factors for both cardiovascular diseases, including hyperglycemia, dyslipidemia, hypertension, and abdominal obesity, and the factor for type 2 diabetes. The usage of bariatric procedures induces a significant amount of durable weight loss and helps to alleviate metabolic syndrome in terms of hypertension, dyslipidemia, and hyperglycemia. These are known risk factors for cardiovascular disease; hence cardiovascular disease is reduced post-bariatric surgery. It is estimated that 85% of all patients with type 2 diabetes are overweight or obese. In these patients, failure to control with lifestyle management and medical therapy would make them more apt for surgical intervention as bariatric procedures are most effective in terms of treatment and long-term remission. Remission is reaching a hemoglobin A1c target at or below 6-6.5% without diabetic medications. This is all dependent on the duration of a patient's type 2 diabetes and the severity at baseline.

As discussed above, bariatric procedures can have glucose regulatory effects as well as neuroendocrine mechanisms. It is believed that gastrointestinal physiology is altered postoperatively as improvement in a patient's glycemic control is seen typically within days two weeks following their procedure. Of note, non-insulin-dependent patients with diabetes or those with a shorter duration or lower baseline hemoglobin A1c level have better outcomes post-bariatric surgery than those with a more advanced stage of diabetes. There is a notable association between hypertension development and obesity. An estimated 64% of adults categorized with severe obesity seeking bariatric procedures have been diagnosed with hypertension. Whether weight loss is achieved through lifestyle modifications or by bariatric surgery, this improves a patient's obesity-associated hypertension and can contribute to its remission. Dyslipidemia also has an association with obesity. Approximately 64% of adults categorized with severe obesity seeking bariatric procedures have dyslipidemia. This includes hypertriglyceridemia, increased low-density lipoprotein cholesterol particles, and even decreased high-density lipoprotein cholesterol levels.[15]

Observational studies have been performed and demonstrate improved lipid profiles post-bariatric procedures. As the risk factors or associated comorbid illnesses with obesity are reduced, the overall cardiovascular risk is thus reduced with bariatric surgeries. This intervention reduces both the number of cardiovascular deaths and a lower incidence of cardiovascular events in adults with obesity.

Postoperative Cancer Reduction

There are known associations between obesity and certain cancers. These cancers include endometrial, renal, breast, and pancreatic cancer. Overall, obesity increases the likelihood of a worse oncologic outcome for a patient. A database study that included over 16,000 patients noted that patients who underwent a bariatric procedure were at a decreased risk of hormone-related cancers compared to patients who did not have bariatric surgery. These cancers include breast, endometrial, and prostate cancer. The Roux-en-Y gastric bypass had the largest risk reduction impact for hormone-related cancers but also had an associated elevated risk for colorectal cancer. Studies performed using a database known as the Swedish Obese Subjects Database had made an association between bariatric surgery with a lower risk of cancer over 20 years from 6% to 3.9%.[16] This reduction was more pronounced in female patients. Interestingly, bariatric procedures are also associated with a lower risk of skin cancers, even that of melanomas.

Functional Outcomes

Functional outcomes also are seen after bariatric surgery. Both the functionality and quality of life are improved in those patients who suffer from obesity-related conditions. The effects do vary depending on the individual condition and which bariatric surgery is performed. Obstructive sleep apnea has an increased prevalence in the obese population. Weight loss, whether by lifestyle modification or bariatric surgery, improves overall health and decreases the apnea-hypopnea index. This index is defined as the number of apneas and hypopneas per hour of sleep. The Roux-en-Y gastric bypass has shown greater weight loss and reduced apnea-hypopnea index.[16]

Gastroesophageal reflux disease is also a risk factor for developing in an obese patient. Overall, a Roux-en-Y gastric bypass is an effective anti-reflux procedure in a patient who has obesity. The American College of Surgeons Bariatric Surgery Center's Network Data shows that approximately 70% of patients achieve improvement in symptomatology or even remission at the one-year mark following Roux-en-Y gastric bypass. There also appears to be a significant improvement in extraesophageal symptoms, the use of proton pump inhibitors, esophagitis, and decreased total acid exposure. Significant joint pain, as well as limitation of physical function, is also associated with severe obesity. Improvement in gait biomechanics and osteoarthritis postoperatively decreases pain and increases joint function. Intravertebral disc height on MRI has shown an increase by approximately 2 mm postoperatively, which would indicate improved inflammatory arthritis.

Obesity does induce a pro-inflammatory state, and postoperatively pro-inflammatory cytokines like C-reactive proteins and interleukin-6 have decreased. Polycystic ovarian syndrome is found in 30% to 70% of obese women in women in their reproductive years. This syndrome is associated with a higher risk of infertility. The hyperandrogenic symptoms, as well as the insulin resistance, can be improved with weight reduction. And women who underwent a Roux-en-Y gastric bypass within 3 to 4 months had improvement in and restoration of menstrual cycles as well as decreased signs of hirsutism. There was a noted increased ability for conception two years after surgery. Diabetes and hypertension, which are typically comorbidities of obesity, can induce renal dysfunction. As discussed above, these comorbidities can be improved secondary to bariatric surgery; thus, renal dysfunction also improves. Lab values such as creatinine and glomerular filtration rate improve one year postoperatively in each of the chronic kidney disease classes.

Obesity also serves as a risk for urinary incontinence secondary to increased intra-abdominal pressure and weakened pelvic floor muscles. Factors for the remission of this disorder include weight loss which could be secondary to bariatric surgery, inability to ambulate independently, and younger age. There is a strong association between the development of nonalcoholic fatty liver disease and obesity. There is an association with bariatric surgery and decreased hepatic inflammation, grade of steatosis, and fibrosis in a patient with nonalcoholic fatty liver disease and obesity.[17] No single procedure is defined as the optimum bariatric procedure in nonalcoholic fatty liver disease patients. Most patients benefit from Roux-en-Y gastric bypass, sleeve gastrectomy, or a laparoscopic adjustable gastric band procedure.

Psychological Impacts

Psychological impacts are seen in patients with obesity. Mental health conditions associated with individuals who undergo bariatric surgery include depression in as high as 19% of patients and binge eating disorders in 17%. These are higher than the rates for the general population within the United States. Improvements in depression, eating disorders, quality of life, and body image have been seen postoperatively following a bariatric intervention. There is a noticeable increase in the prevalence of alcohol and substance abuse after bariatric interventions. Studies have shown that most of these patients have developed alcohol use disorder the second year postoperatively.[18]

Postoperative Nutritional Management

Malnutrition can result after any bariatric procedure if the patient does not adhere to a proper diet. Bypass procedures such as the biliopancreatic diversion with duodenal switch or the Roux-en-Y gastric bypass are known causes for micronutrient malabsorption. Sleeve gastrectomy procedures do not lead to intestinal bypass but can have nutritional deficiencies. A staged approach is taken with a significant emphasis on nutritional needs at each stage of healing and weight loss. Texture and volume of food are given consideration. Early in the postoperative phase, a patient is given a diet of hydration and liquids. An emphasis is also placed on adequate protein intake. Stage one consists of a clear liquid diet with advancement to a full liquid diet and then to puréed foods, consumed for several weeks after the operation. The puréed diet is the stage two diet. The key reasons for an emphasis on hydration with adequate protein and carbohydrate consumption to meet metabolic needs are essential, and the stage two diet also aids in avoiding irritation to the surgical sites along the digestive tract.[19]

Importantly, all patients should receive both preoperative education surrounding their surgery with an education that focuses on their nutritional needs in the postoperative phase. This would include consuming adequate amounts of both clear and full liquids daily to maintain proper hydration status and urinary output. Guidelines such as a shopping list and sample meals of when a patient should be consuming these liquids and the appropriate amount should be provided preoperatively. A stage three diet is also known as a soft solid food diet and tends to occur anywhere from 10 to 14 days postoperatively. This timeframe is approximately when the gastrointestinal tract is healing, and the patient can tolerate solid textured foods. Soft solid foods should include a good source of protein, some carbohydrates, and fruits and vegetables to provide fiber. Puréeing food is not required, but if a patient maintains difficulty chewing, they can continue with puréeing food.

Again, adequate fluid intake is encouraged to prevent dehydration. The patient should be counseled on eating during the stages. They should eat slowly, chew their food very extensively, stop eating once they reach the point of satiety, and avoid food and beverage intake at the same time. If a patient ingests food too rapidly or consumes more than the stomach pouch or sleeve has the capacity for, epigastric discomfort and vomiting typically occur.

With the progression of these dietary stages, guidance by the help of a bariatric registered dietitian is advised. The stage four diet consists of solid food, starting when a patient reaches their stable, maintenance weight. It tends to be unpredictable at what point a patient will reach the stage as there is variability in the rate of weight loss, the healing process, food tolerances, and the amount of food a patient can consume. The transition throughout these dietary stages is all based on individual tolerance levels. Supplementation for micronutrients is initially started upon hospital discharge with either chewable or liquid vitamins. At around the three-month mark, most patients can tolerate regular vitamin pills. These supplements should contain the recommended daily allowance amounts for biotin, zinc, vitamin B 12, Vitamin K, folic acid, copper, and iron.[19]

After a Roux-en-Y gastric bypass, the patient may have food aversions when transitioning from the liquids to soft foods into a full diet. There is a loss of a variety of foods when progressing through this post-bariatric procedure diet. A patient after this procedure may have a degree of dumping syndrome, as discussed above. Food intolerance can also develop, especially with red meat. The sleeve gastrectomy procedure again involves resectioning the greater curvature of the stomach, including the fundus. This promotes rapid gastric emptying, accelerates the transit time of nutrients into the small intestine, and leads to favorable changes within the gut microbiome.

Patients undergoing a sleeve gastrectomy should be wary of acid reflux symptoms postoperatively. The stomach has a limited capacity as well as decreased motility of food particles through the sleeve during healing, with the preservation of stomach acid, which can lead to symptoms of acid reflux if ingesting food too fast or too much. The biliopancreatic diversion with duodenal switch is associated with a substantial amount of malabsorption of both micro and macronutrients. The malabsorption causes diarrhea and poses a risk for both protein-calorie malnutrition and severe deficiencies and micronutrients, like that of fat-soluble vitamins.[20]

In bariatric patients, vitamins and mineral laboratory evaluation should be done annually for life. As with Roux-en-Y gastric bypass procedures, biliopancreatic diversion with a duodenal switch can lead to dumping syndrome. Osteoporosis is seen due to the malabsorption of vitamin D and calcium. With malabsorption of fat-soluble vitamins, like A, D, E, K as well as protein, fat, iron, and calcium, a patient can have foul-smelling stools and diarrhea. A potentially life-threatening diagnosis from protein malnutrition is known as kwashiorkor, which can be seen in the biliopancreatic diversion. The addition of duodenal switch with pancreatic diversion has reduced the rate of protein malabsorption from 11% to 3%. Overall, macronutrient and micronutrient goals and supplementation should be discussed and determined in the preoperative phase with a bariatric registered dietician to prevent deficiencies and subsequent symptomatology.[20]

Complications

There are multiple complications to bariatric procedures. In sleeve gastrectomy, staple line leaks can be an early complication within the first few weeks in the postoperative period. The sleeve gastrectomy surgery creates a small volume stomach wedged between two sphincters, thus having high pressure. This can result in distention leading to ischemia and delayed healing along the staple or suture line. A patient may complain from mild or nagging abdominal discomfort to hemodynamic instability and peritonitis.

If a patient presents with fever, epigastric pain, tachycardia, or referred shoulder pain, a leak should be considered. Imaging should be performed with an abdominal CT with oral contrast; IV contrast may or may not be given. The second line imaging modality is an upper gastrointestinal series (GI) or even endoscopy. If a leak is detected within the first week postoperatively, a repair or revision surgically is the treatment of choice. Endoscopic repair is preferred after a week from surgery. In a stable patient, a percutaneous drain, as well as antibiotics and total parenteral nutrition (TPN) therapy, can be provided until the leak heals, thus avoiding surgical intervention. A gastric outlet obstruction can occur after a sleeve gastrectomy secondary to stenosis of the tubular stomach.[20]

The most common sites for this would include the incisura angularis as well as the gastroesophageal junction. A patient will likely have symptoms such as reflux, nausea, vomiting, dysphagia, dehydration, and an inability to tolerate oral intake. An early cause associated with stenosis is oversewing of the staple line. This results in both edema and ischemia. Later, there can be fibrosis and kinking or rotation of the tubular-shaped gastric pouch. To identify sleeve gastrectomy stenosis, an abdominal CT with oral and IV contrast should be performed.[20]

The literature recommends that a patient presenting more mildly with symptoms limited to dysphagia and reflux undergo an upper GI series instead. The upper GI series will demonstrate dilation and accumulation contrast proximal to the area of stenosis. Treatment modality includes endoscopic dilation of the stenotic area. A surgical revision or conversion may be appropriate if a stenosed area is too great in length. Other complications typically seen in less than one month postoperatively include abscess formation, fistula, or bleed.[20]

Roux-en-Y gastric bypass has complications that should be recognized. An early complication within the first ten days of the postoperative period would include an anastomotic leak. This is like the staple line leak seen with sleeve gastrectomy. The most encountered site for an enteric leak is gastrojejunal anastomosis. Jejunojejunal anastomotic leaks can also occur in the early postoperative period. Presenting symptoms include fever, nausea, vomiting, tachycardia, oliguria, abdominal pain, and hypotension. The first line imaging choice would be a CT scan with oral and IV contrast. Pneumoperitoneum, contrast leak, abscess formation, or fat stranding may be visualized on the CT scan.

An upper GI series is the second line in terms of imaging modality. Once diagnosed with an anastomotic leak, broad-spectrum antibiotics should be initiated. If a patient has signs of peritonitis on physical examination or has hemodynamic instability, emergent surgery may be required for repair with aggressive fluid resuscitation. A stable patient in this circumstance may be able to avoid surgical intervention with admission for broad-spectrum antibiotics, percutaneous drainage, and TPN. About 6% of all gastric bypass patients suffer from anastomotic stenosis. The areas of stenosis typically occur at the gastrojejunal or jejunojejunal anastomosis.[21]

In the first week of the postoperative period, jejunojejunal stenoses are more common, whereas gastrojejunal stenosis is typically seen several weeks to months later. These areas of stenosis occur when the stoma is narrow to less than 1 cm in diameter. This is likely secondary to ischemia and/or ulceration. Stenosis causes a bowel obstruction with the proximal backup of fluid. Patients with gastrojejunal stenosis will typically present with nausea, vomiting, reflux, epigastric pain, progressive dysphagia, and an inability to tolerate oral intake, even that of fluids. An upper GI series will show gastric dilation with a reduced flow of contrast through the anastomosis in gastrojejunal stenosis. Conversely, a jejunojejunal stenosis will show dilation of the stomach remnant and the biliopancreatic limb.[21] Endoscopic balloon dilation should be performed for gastrojejunal stenosis. Surgical repair is likely for a jejunojejunal stenosis.

Ulceration around the anastomotic junction, typically the gastrojejunal junction can occur in a Roux-en-Y gastric bypass. This is known as a marginal ulcer. In the normal, non-surgically intervened GI tract, stomach acid is buffered by bilious secretions and pancreatic secretions within the duodenum.

Post-Roux-en-Y gastric bypass, the duodenal mucosa is exposed to buffered stomach acids, even with a smaller stomach area. This leads to mucosal breakdown as well as ulceration. Importantly, ulceration can also be due to other factors like ischemia due to tension at the anastomosis site, a helicobacter pylori infection, smoking, and nonsteroidal anti-inflammatory (NSAID) use. A patient with suspected ulceration typically presents with vague abdominal pain, nausea, vomiting, hematemesis, dysphagia, and GI bleeding. Diagnosis and management of marginal ulcers are performed via endoscopy, which allows for diagnosis, biopsy, and monitoring.[21]

Upon discharge, a patient should have six weeks of a proton pump inhibitor, and sucralfate prescribed. Any NSAIDs should be discontinued, and counseling on smoking cessation should be provided. Surgical intervention may be necessary if a patient has gastric perforation or continues to re-bleed despite medical management. A complication of a Roux-en-Y gastric bypass that requires urgent evaluation includes small bowel obstruction and internal hernias. It is estimated that 60% of small bowel obstructions in a patient with Roux-en-Y gastric bypass are secondary to internal hernias, which can occur at any time in the postoperative period. The anatomical rearrangement, as well as the substantial weight loss post-procedure, leads to large potential spaces within the abdominal cavity for herniation.[22]

The patient's symptomatology can vary from a diffuse vague abdominal pain with nausea and vomiting to peritonitis. Obstruction typically presents with intermittent distinct periods of abdominal discomfort in the same region. Typically, a patient with an internal hernia will have constant pain with incarceration or strangulation of the bowel loop. If a patient does have bilious emesis following this procedure, this indicates a common limb obstruction. This requires emergent surgical care due to the risk of distention of the biliopancreatic limb and stomach remnant rupture. Imaging of choice would be an abdominal CT scan with oral and IV contrast during a painful episode.[21][22][21]

Dumping syndrome is a complication postoperatively secondary to rapid gastric emptying. The incidence of the syndrome is seen in nearly 75% of gastric bypass patients. This occurs as there is either bypass or removal of the stomach pylorus, which, in turn, causes rapid movement of stomach contents into the small intestine. When a high carbohydrate meal is ingested, this hyperosmolar food bolus enters the intestines and leads to bowel distention, fluid shifts across the intestinal wall, and causes GI hormone over secretion.

The patient may have early dumping syndrome, which demonstrates symptoms 30 minutes postprandial, or late dumping syndrome, which occurs 2 to 4 hours postprandial. Patients with early dumping syndrome tend to have dehydration, abdominal pain, diarrhea, nausea, tachycardia, dizziness, hypotension, and syncope. The late dumping syndrome is secondary to a postprandial insulin surge in response to a high carbohydrate intake, leading to hypoglycemia hours after a meal. Patients with a late dumping syndrome tend to have symptoms such as faintness, decreased concentration, altered mental status, and hyperhidrosis. Treatment for these patients is both fluid resuscitation and electrolyte repletion. Dietary modifications should be taken as well. Adequate counseling and discharge instructions should also be included. Patients are advised to eat smaller meals, avoid concentrated foods, and limit sugar and lactose intake. Early dumping syndrome tends to be self-limiting and resolves within the 7 to 12-week postoperative period.[22]

Octreotide treatments can reduce symptoms by slowing the gastric emptying process in severe cases. As discussed above, metabolic derangements can occur after bariatric surgeries. In a patient who has undergone a Roux-en-Y gastric bypass, calcium and iron resorption in the duodenum is bypassed, which leads to deficiencies. The intraluminal pH within the duodenum is reconfigured, which leads to an inactive form of intrinsic factor. This impairs vitamin B12 absorption. Vitamin D absorption is also impaired, so supplementation should be provided to prevent early osteoporosis. Within most bariatric procedures, an early complication is vomiting and decreased oral intake, which predisposes a patient to thiamine deficiency.

Biliopancreatic diversion with a duodenal switch can also have complications. The most common major complication includes an anastomotic leak, anastomotic stenosis with an associated small bowel obstruction, and GI hemorrhage. Weight complications, as defined as greater than 30 days postoperatively, tend to involve a small bowel obstruction, incisional hernias, and malnutrition.[22]

The malabsorption associated with this procedure causes mineral and vitamin derangement. These levels include that fat-soluble vitamins, zinc, selenium, iron, calcium, and magnesium. Notably, severe protein deficiency, described as an albumin level less than 30 g per liter, was only noted in approximately 1% of patients. To minimize these nutrient deficiencies, a patient undergoing this procedure requires a more intensive supplementation regimen in the postoperative period and monitoring their nutritional status closely for life.[22]

Complications seen in the laparoscopic adjustable gastric band include band slippage, band erosion, and port site infection, which may require balloon deflation or removal. If a patient has peritonitis and or signs from a perforation, this may require surgical repair.

Overall, bariatric surgery is safe and effective in evaluating and treating obese patients, particularly severely obese patients. As discussed above, multiple surgical interventions can provide adequate results, but each of these options does have technical as well as metabolic issues that should be considered when determining a weight-loss surgery for each patient. Not only should a patient undergo an extensive preoperative assessment, but a postoperative plan which includes a discussion with the multi-disciplinary team should also be completed. The surgery with all associated risks, benefits, and alternatives to surgery should be discussed. Given the extent of the risk-to-benefit ratio which favors surgical intervention in severely obese patients, bariatric surgery can be a viable option for substantial and long-term weight loss as well as comorbidity control.

Enhancing Healthcare Team Outcomes

Managing a bariatric patient with severe obesity is both challenging and complex. While a skilled surgeon is required for surgical success, the care surrounding this patient requires the expertise of a multidisciplinary team. To derive favorable outcomes, meet the goals and objectives of healthy weight loss and maintenance long-term, a patient must be counseled appropriately with the aid of the bariatric team. This team includes a registered dietitian, bariatric medical specialist, bariatric nurses, and bariatric surgeon. It is essential to incorporate assistance from each team member of the interprofessional healthcare to optimize the patient for success. [Level 5]

A retrospective observational study that analyzed multidisciplinary team treatment decisions to proceed with bariatric surgery found that an interprofessional format changed surgical decision-making for a significant number of patients. Specifically, there was an interprofessional team agreement for 55% of patients to proceed to surgery versus 45% team disagreement. The most common reason for the failure of team agreement was the patient’s nonadherence to attending appointments. Overall, using a single-day multidisciplinary team clinic format improved the quality of care for patients and likely avoided preventable bad outcomes. The interprofessional team approach for bariatric surgery is valuable and should be the standard of care.[23]


Article Details

Article Author

Kaitlyn Crossan

Article Editor:

Amy J. Sheer

Updated:

1/2/2022 4:54:33 PM

References

[1]

Arterburn DE,Telem DA,Kushner RF,Courcoulas AP, Benefits and Risks of Bariatric Surgery in Adults: A Review. JAMA. 2020 Sep 1;     [PubMed PMID: 32870301]

[2]

Buchwald H, The evolution of metabolic/bariatric surgery. Obesity surgery. 2014 Aug;     [PubMed PMID: 25008469]

[3]

Stewart F,Avenell A, Behavioural Interventions for Severe Obesity Before and/or After Bariatric Surgery: a Systematic Review and Meta-analysis. Obesity surgery. 2016 Jun;     [PubMed PMID: 26342482]

[4]

Benaiges D,Goday A,Pedro-Botet J,Más A,Chillarón JJ,Flores-Le Roux JA, Bariatric surgery: to whom and when? Minerva endocrinologica. 2015 Jun     [PubMed PMID: 25665592]

[5]

Parrott JM,Craggs-Dino L,Faria SL,O'Kane M, The Optimal Nutritional Programme for Bariatric and Metabolic Surgery. Current obesity reports. 2020 Sep;     [PubMed PMID: 32451780]

[6]

Piché ME,Tchernof A,Després JP, Obesity Phenotypes, Diabetes, and Cardiovascular Diseases. Circulation research. 2020 May 22;     [PubMed PMID: 32437302]

[7]

Climent E,Benaiges D,Pedro-Botet J,Goday A,Solà I,Ramón JM,Flores-LE Roux JA,Checa MÁ, Laparoscopic Roux-en-Y gastric bypass vs. laparoscopic sleeve gastrectomy for morbid obesity: a systematic review and meta-analysis of lipid effects at one year postsurgery. Minerva endocrinologica. 2018 Mar;     [PubMed PMID: 28206728]

[8]

Wiggins T,Majid MS,Agrawal S, From the Knife to the Endoscope-a History of Bariatric Surgery. Current obesity reports. 2020 Sep;     [PubMed PMID: 32430773]

[9]

Schirmer B, Laparoscopic bariatric surgery. Surgical endoscopy. 2006 Apr;     [PubMed PMID: 16544059]

[10]

Zhu C,Pryor AD, Innovations in Bariatric Surgery. Surgical technology international. 2015 Nov;     [PubMed PMID: 26680389]

[11]

Chung AY,Thompson R,Overby DW,Duke MC,Farrell TM, Sleeve Gastrectomy: Surgical Tips. Journal of laparoendoscopic & advanced surgical techniques. Part A. 2018 Aug     [PubMed PMID: 30004814]

[12]

Fernandes M,Atallah AN,Soares BG,Humberto S,Guimarães S,Matos D,Monteiro L,Richter B, Intragastric balloon for obesity. The Cochrane database of systematic reviews. 2007 Jan 24;     [PubMed PMID: 17253531]

[13]

Sánchez-Pernaute A,Rubio MÁ,Pérez N,Marcuello C,Torres A,Pérez-Aguirre E, Single-anastomosis duodenoileal bypass as a revisional or second-step operation after sleeve gastrectomy. Surgery for obesity and related diseases : official journal of the American Society for Bariatric Surgery. 2020 Oct;     [PubMed PMID: 32665113]

[14]

Switzer NJ,Karmali S,Gill RS,Sherman V, Revisional Bariatric Surgery. The Surgical clinics of North America. 2016 Aug;     [PubMed PMID: 27473804]

[15]

Schlottmann F,Galvarini MM,Dreifuss NH,Laxague F,Buxhoeveden R,Gorodner V, Metabolic Effects of Bariatric Surgery. Journal of laparoendoscopic     [PubMed PMID: 30004821]

[16]

Mackenzie H,Markar SR,Askari A,Faiz O,Hull M,Purkayastha S,Møller H,Lagergren J, Obesity surgery and risk of cancer. The British journal of surgery. 2018 Nov;     [PubMed PMID: 30003539]

[17]

Jumbe S,Hamlet C,Meyrick J, Psychological Aspects of Bariatric Surgery as a Treatment for Obesity. Current obesity reports. 2017 Mar;     [PubMed PMID: 28243838]

[18]

Kassir R,Debs T,Blanc P,Gugenheim J,Ben Amor I,Boutet C,Tiffet O, Complications of bariatric surgery: Presentation and emergency management. International journal of surgery (London, England). 2016 Mar;     [PubMed PMID: 26808323]

[19]

Mechanick JI,Apovian C,Brethauer S,Garvey WT,Joffe AM,Kim J,Kushner RF,Lindquist R,Pessah-Pollack R,Seger J,Urman RD,Adams S,Cleek JB,Correa R,Figaro MK,Flanders K,Grams J,Hurley DL,Kothari S,Seger MV,Still CD, CLINICAL PRACTICE GUIDELINES FOR THE PERIOPERATIVE NUTRITION, METABOLIC, AND NONSURGICAL SUPPORT OF PATIENTS UNDERGOING BARIATRIC PROCEDURES - 2019 UPDATE: COSPONSORED BY AMERICAN ASSOCIATION OF CLINICAL ENDOCRINOLOGISTS/AMERICAN COLLEGE OF ENDOCRINOLOGY, THE OBESITY SOCIETY, AMERICAN SOCIETY FOR METABOLIC     [PubMed PMID: 31682518]

[20]

Thorell A,MacCormick AD,Awad S,Reynolds N,Roulin D,Demartines N,Vignaud M,Alvarez A,Singh PM,Lobo DN, Guidelines for Perioperative Care in Bariatric Surgery: Enhanced Recovery After Surgery (ERAS) Society Recommendations. World journal of surgery. 2016 Sep;     [PubMed PMID: 26943657]

[21]

Conner J,Nottingham JM, Biliopancreatic Diversion With Duodenal Switch StatPearls. 2021 Jan;     [PubMed PMID: 33085340]

[22]

Tabesh MR,Maleklou F,Ejtehadi F,Alizadeh Z, Nutrition, Physical Activity, and Prescription of Supplements in Pre- and Post-bariatric Surgery Patients: a Practical Guideline. Obesity surgery. 2019 Oct;     [PubMed PMID: 31367987]

[23]

Bullen NL,Parmar J,Gilbert J,Clarke M,Cota A,Finlay IG, How Effective Is the Multidisciplinary Team Approach in Bariatric Surgery? Obesity surgery. 2019 Oct;     [PubMed PMID: 31209829]