Bariatric Metabolic Surgery

1. Introduction

Obesity belongs to the most serious metabolic diseases affecting human health. It has pandemic character and significantly increases the risk of cardiovascular and other obesity-related health complications. The treatment is complex and requires a multidisciplinary approach.

Obesity is the second most common preventable cause of death (after smoking). It is associated with a number of serious negative effects on glucose & lipid metabolism, cardiovascular, respiratory, and musculoskeletal systems as well as mental health. Obesity has a negative impact on fertility, leads to a decreased quality of life, increases the incidence of certain cancers, and likelihood of ischemic and hemorrhagic stroke—thus being responsible for decreased overall survival.

Obesity is a serious medical, social, and economic problem with an interdisciplinary overlap, so sustainable long-term therapeutical success is a must. Obesity can be treated by lifestyle interventions, diet, pharmacologically, or surgically. Healthy lifestyle change with increased physical activity and reduced caloric intake usually results in the first 10% weight loss. To strengthen the effect of the lifestyle change, psychological support in the form of behavioral therapy is needed, since obesity is considered a maladaptive syndrome of eating habits and physical activity [1, 2]. The problem is that caloric restriction reduces the body’s basal metabolism, which significantly reduces the effect of further reduction of food intake in the context of weight loss. Many patients are unable to maintain such a low caloric intake that would lead to continuing weight loss thus risking the “yo-yo effect” (weight regain). Significant progress has been achieved in the field of pharmacotherapy and the new effective drugs such as GLP-1 peptide analogs with better short and long-term effects have appeared on the market [3]. However, in patients who do not achieve a weight loss of more than 5% after 4 months of pharmacological antiobesity therapy, this medication should be discontinued. Nevertheless, bariatric-metabolic surgery (BMS) that leads to significant changes in the body composition remains the most effective long-term therapy for obesity. BMS procedures not only assure weight loss but also positively affect various metabolic and cardiovascular illnesses. As such, the patient may benefit from improvement of several concomitant diseases after mini-invasive BMS intervention.

2. Research methods

A systematic review of the literature was carried out using the databases PubMed, Web of Science, and EBSCO. The MeSH terms relevant for given subchapters were used and subsequently, identified literature resources were reviewed to select the most relevant references.

3. History of BMS

The first attempt at targeted surgery to reduce weight came in the 10th century when a Jewish doctor stitched the lips of the Spanish king, who lost his throne due to obesity. He was left with a small opening to receive liquids, lost half of his weight, and regained the throne [4].

The modern era of bariatric surgery dates back to the 1950s when Swedish surgeon Hendriksson performed the first targeted malabsorptive procedure—resection of part of the small intestine in 1952 [5]. After experimental research on dogs, surgeons began performing jejunoileal bypass in humans in Minnesota (USA). The weight loss was excellent, but malabsorption had unfortunate consequences and the method was soon abandoned due to related complications (liver failure, vitamin deficiency, malnutrition, kidney stones, and others).

In 1966, gastric bypass was introduced into the clinical practice by Mason, inspired by the observation of weight loss in patients after gastric resection for cancer [6]. This operation combines malabsorption (bypasses the duodenum) with restriction (reduces the volume of the stomach). The procedure is currently performed in the Roux-en-Y modification (RYGB) and belongs to the most frequent BMS methods [7].

Jaw wiring was introduced in bariatrics in 1977. The results were excellent, but there was a huge yo-yo effect after the procedure reversal [4].

In 1979, Scopinaro performed biliopancreatic diversion (BPD) [7], and in 1986, Kuzmak invented the silastic ring, based on which adjustable gastric banding was described [8]. In 1987, Johnston introduced gastric sleeve resection, the operation that is currently performed most frequently [9]. Originally it was a part of BPD-duodenal switch.

In 1993, Wittgrove and Clark performed the first laparoscopic RYGB [10]. In the same year, Fried introduced laparoscopic non-adjustable and Broadbent laparoscopic adjustable gastric banding. With laparoscopic approach, perioperative mortality fell below 0.2% and complications decreased to one-third. The length of hospitalization and the patient’s recovery time were significantly shortened.

The shift from bariatric to metabolic surgery originated from MacDonald and Pories, who described the positive effect of RYGB on type II Diabetes Mellitus in 1995 [11]. In 1998, obesity was recognized as a metabolic disease, not just an esthetic issue, and costs of BMS began to be covered by health insurance [12].

4. Indications for BMS

Although BMI does not reflect exact body composition, it is widely used as a crucial indicator for BMS due to its simplicity and universal applicability. Patients with greater BMI based on higher muscular mass without obvious excess of fat may not benefit from BMI. Nevertheless, the following indication criteria for the BMS procedures, based on the recommendations of the international working groups IFSO and ASMBS [13], apply in the current general practice:

• individuals with BMI higher than 35 kg/m² are indicated for BMS regardless of the presence, absence, or severity of comorbidities.

• individuals with BMI over 30 kg/m² who have failed other methods of weight reduction or whose obesity-related comorbidities cannot be compensated satisfactorily

• regarding the Asian population, the BMI thresholds have been shifted to 27.5 and 25 kg/m²

• age limit for surgery does not exist anymore, also younger and older individuals can be operated on, taking into consideration the individual balance between the risk and benefit

• in children and adolescents, BMS should be considered if they have a BMI above 120% of their 95th percentile associated with obesity-related comorbidities, or if they have a BMI above 140% of the 95th percentile

• BMS is recommended for patients in whom excess weight loss is desirable in order to undergo other major surgical interventions such as joint arthroplasty, abdominal wall hernia repair, or organ transplantation.

Multidisciplinary assessment of patients on individual basis helps to select those suitable for BMS and determine the best type of BMS procedure. Reoperations due to failure or insufficient effect of the first BMS operation are not an exception. The re-do surgeries can either mean extension of the primary procedure (i.e. distalization of the anastomosis in bypass) or conversion to more aggressive type (i.e. sleeve gastrectomy to RYGB).

5. Current BMS (state of the art procedures)

5.1 Sleeve gastrectomy (SG)

Sleeve gastrectomy (Figure 1) currently represents the most widespread BMS operation in the world. It is defined by 80–90% pylorus-preserving vertical resection of the stomach. It evolved from biliopancreatic diversion with duodenal switch when it was adopted as the first stage of the procedure in high-risk patients. Subsequently, it was observed that vast majority of those patients experienced significant weight loss and did not have to undergo the second stage of the operation. This procedure is defined by both restrictive—reducing the volume of the stomach and metabolic effect—reducing the production of the orexigenic hormone ghrelin. It appears to be a relatively safe surgical method with perioperative mortality close to zero and very low morbidity. The most common complications include bleeding from the resection line, leakage, and gastric fistula. Micronutrient depletion occurs postoperatively, but it seems to be less prominent than after RYGB and disappears after 5 years. Nevertheless, laboratory screening for depletion should be carried out once a year to allow for appropriate supplementation of micronutrients.

The biggest advantage of the procedure is long-term excess weight loss (EWL) of up to 80%. Furthermore, metabolic diseases, including hyperlipidemia and diabetes, disorders of coagulation cascade, biochemical parameters, nonalcoholic fatty liver disease (NAFLD), cardiovascular disorders, obstructive sleep apnea, and hypertension, can be controlled better. Also, non-metabolic diseases, such as musculoskeletal pain, ovarian dysfunction, infertility, incontinence, and the incidence of cancer, are decreased. The procedure is performed laparoscopically, under general anesthesia in the supine position, usually from 5 ports [14, 15, 16]. Patients are admitted to the intensive care unit (ICU) for 1 day and in case of uncomplicated postoperative course dismissed on 1st–3rd postoperative day.

Long-term, ideally lifelong follow-up is a necessity. Significant percentage of patients after sleeve gastrectomy report gastroesophageal reflux disease that may progress to Barrett’s esophagus. While proton pump inhibitors provide effective therapeutic solution for majority of patients, conversion to RYGB may be necessary in some patients.

5.2 Roux-en-Y gastric bypass (RYGB)

Roux-en-Y gastric bypass (Figure 2) means “in the form of a Y” in French. It is the second most spread BMS procedure in the world. This operation consists of several steps. First, a gastric pouch is formed, where a smaller part remains in contact with the esophagus and a larger part is excluded from food intake and remains connected to the duodenum. The goal is to create a small, about 20 ml, gastric reservoir. In the next step, a biliopancreatic limb is formed, which is about 100 cm long (from the ligament of Treitz) and is connected to the alimentary tract about 100 cm aboral from the pylorus by jejunojejunostomy, and after that the continuity of the digestive tube is restored by a gastrojejunostomy [17]. Mesenteric defect is closed with a continuous suture to prevent internal hernia formation after anticipated significant weight loss. Some surgeons close also the Petersen’s space. Patient is monitored in the ICU postoperatively, liquids are administered 3–4 hours after the operation through a straw, and mobilization should be started 4–5 hours after the procedure. Nutritional therapist provides education regarding the appropriate food intake and special diet. Hospital stay is usually about 3 days.

The effect of gastric bypass is restrictive, malabsorptive, and metabolic. Reduced volume of the stomach gives a feeling of satiety with less food intake while biliopancreatic loop reduces absorption in the small intestine. Metabolic effect is most pronounced in patients suffering from type 2 diabetes mellitus (DMT2). The operation is also beneficial for patients with gastroesophageal reflux disease. The effect of therapy is long-lasting, and the EWL is around 70–80%. Complications tend to be more frequent after RYGB, and morbidity is doubled compared to that of SG. It is absolutely necessary to pay attention to the supplementation of micronutrients and vitamins, as there is an increased risk of their depletion. Malnutrition with liver cirrhosis is very serious consequence of non-compliance with the regime. The follow-up must be performed at standard intervals, and laboratory control should be scheduled once to twice per year. There is a recommendation of standard ion and vitamin supplementation to all patients with possible modifications depending on the laboratory findings. RYGB may also cause “dumping syndrome,” a group of symptoms, including diarrhea, nausea, and feeling of sickness after eating or drinking, especially sweets. The risk of internal hernia after RYGB should not be underestimated. Also of note, tobacco and NSAIDs use considerably increases the risk of peptic ulcerations.

5.3 One anastomosis gastric bypass (OAGB)

OAGB (Figure 3) is very similar to RYGB and its effect on weight reduction and metabolic effect is practically identical [18]. Nevertheless, the procedure itself is technically easier. The principle of operation is construction of gastric reservoir, which is longer than in the Roux-en-Y modification, but very narrow. It is created by gastric resection along the 36F probe, similar to sleeve gastrectomy after the stomach is partially cut at a right angle to the lesser curvature at the level of the angular incisure. A simple side-to-side gastroenteroanastomosis is then created at a distance of 200 cm from the Treitz ligament. Some studies confirmed certain degree of biliary reflux but did not demonstrate a higher risk of gastric or esophageal cancer. Nevertheless, presence of severe gastroesophageal reflux or Barrett’s esophagus represents contraindication for OAGB. Postoperative care is identical to RYGB.

5.4 Biliopancreatic diversion with duodenal switch (BPD-DS)

Biliopancreatic diversion (BPD), originally proposed by Scopinaro in 1976, was performed as a 2/3 resection of the stomach and division of the small intestine into alimentary and biliary arm. In the alimentary arm, only carbohydrates and proteins are resorbed while fat resorption takes place in the common channel of the small intestine, 50 cm long, where both arms join. The procedure resembles gastric bypass in the Roux-en-Y modification, but the so-called common channel, that is, the part of the small intestine where all nutrients are resorbed, is significantly shorter than in RYGB (Figure 4). This makes the effect of the operation more pronounced, but at the same time, the quality of life is negatively affected and the risk of malnutrition tends to be higher. In an effort to achieve more physiological conditions during the passage of food through the stomach, Hess proposed an operation called “biliopancreatic diversion with duodenal switch.” Gastric resection is performed similarly to sleeve gastrectomy but a section of approximately 5 cm of duodenum is left, and duodeno-entero anastomosis is created there. The goal is to reduce acidity at the anastomotic site, achieve a quick feeling of satiety, and preserve antropyloric function. Leaving a short section of the duodenum improves the resorption of iron, calcium, and magnesium. It also eliminates the risk of dumping syndrome and reduces the risk of ulcer formation in the anastomosis. Both modifications—BPD and BPD-DS—are currently performed worldwide only in a minimal number of cases [19].

5.5 Single anastomosis duodenal-ileal bypass with sleeve (SADI-S)

SADI-S represents relatively new approach in BMS. The procedure is technically easier than BPD. The first phase of SADI-S is sleeve gastric resection followed by the transverse incision of the duodenum and creation of duodenoenteroanastomosis. The small bowel suture site is 250–300 cm from the ileocecal junction (Figure 5). As such, this operation achieves a combination of food intake restriction and severe malnutrition, which makes this surgery very effective. SADI-S is more frequently used as a re-do procedure after failure of previous sleeve gastrectomy rather than as a primary surgery [20, 21].

5.6 Adjustable gastric banding (AGB)

This BMS procedure gained peak popularity in Europe at the turn of the millennium. In principle, food intake is restricted by application of the silicone ring just below the gastroesophageal junction thus creating a small gastric reservoir (Figure 6). The tightness of the band can be adjusted by calibrating the balloon on its inner side by injecting the physiological solution into the calibration chamber (connected with the band by tube) that is subcutaneously implanted into the abdominal wall.

Currently, AGB is practically abandoned because of the fact that other operations are significantly more effective in the long term [22]. At the moment, AGB accounts for less than 1% of bariatric procedures performed worldwide.

6. Emerging procedures

6.1 Single aastomosis sleeve ileal bypass (SASI)

SASI is the combination of sleeve resection and single side-to-side anastomosis in the region of the gastric antrum and ileum, 250 cm before the ileocecal junction (Figure 7). Part of the food passes through the natural pathways and part through the anastomosis, which achieves a certain degree of malnutrition and activates intestinal hormones. The great advantage of this procedure is the preservation of the passage through the pylorus and the duodenum enabling endoscopic access to the papilla of Vater, which can be truly important for the management of the common bile duct stones or other diseases of the extrahepatic bile ducts. This operation, however, has not been recognized yet as standardized BMS approach by the IFSO. SASI offers both excellent weight loss and resolution of comorbidities. Some data suggest the average EWL at 12 months as high as 85.6% and diabetes remission in 95.8% of patients [23]. Nevertheless, more high-quality and large-scale studies are still needed to support the efficacy of SASI.

7. Endoscopic procedures

Endoscopic bariatric metabolic procedures seem optimal in very high-risk patients as a bridge to BMS rather than final solution. There are several endoscopic options that are currently used in clinical practice.

Various types of gastric balloons reducing the effective volume of the stomach have been designed. One of the most up-to-date examples is the Obalon, which can be swallowed as a small capsule on a connecting tube and then filled with liquid without the aid of endoscopy. It is possible to place up to three balloons in the stomach, which must be removed within 6 months endoscopically. Another interesting concept is represented by the so-called transpyloric shuttle. During this procedure, two interconnected balloons are inserted endoscopically, the larger one in the stomach and smaller one in the duodenum. The gastric part of the shuttle prolongs the evacuation of the stomach (Figure 8). This system is indicated for the patients with BMI of 30–40 kg/m² and can be left in place for 12 months.

Some endoscopic procedures reduce the volume of the stomach by suturing its wall, thus mimicking SG. The Apollo overstitch system is capable of constructing endoscopic transmural sutures. The disadvantage of the technique is an increased risk of suture line failure compared to SG, which is reflected in the lower efficacy in terms of the weight loss [24].

Another innovative endoscopic option is duodenojejunal sleeve. During the procedure, polyethylene sleeve is anchored in the pyloric area by a metal ring with hooks around its perimeter. The length of the sleeve is 60 cm, so it reaches up to the proximal jejunum. This prevents contact of food with the mucosa of the duodenum (Figure 9). As a result, anatomical and pathophysiological effects of the gastric bypass are imitated. Nevertheless, endoscopic sleeve can only be left in situ for a maximum of 12 months, after which it must be extracted. Data demonstrates weight gain after sleeve explantation. Also of note, one of the studies had to be discontinued due to unacceptable rate of complications [25].

In general, it can be concluded that endoscopic procedures have not yet been proven effective in the long term. One can appreciate their importance in high-risk patients for whom surgery would be unbearable, or, as a bridge to surgical intervention. To evaluate the true potential of endoscopic procedures, future properly designed larger-scale studies with long-term follow-up are necessary.

8. Discussion

Ideal BMS procedure should ensure maximal long-term EWL with minimal complications. Nevertheless, universal single approach does not exist at the moment, so patients require individual assessment and tailored therapy.

In the past, gastric banding was very popular operation among both patients and surgeons due to its relative simplicity, reversibility, and significant weight loss achieved on solely restrictive principle. However, in the long term, EWL did not seem sustainable. Also of note, complications requiring removal of the band lead to almost 100% yo-yo effect [26].

On the contrary, malabsorptive procedures proved to be highly successful in terms of sustainable long-term weight loss, but their results were discredited by metabolic complications and risk of disruption of the internal environment. Nevertheless, RYGB has established itself as a relatively safe and effective option over the time, providing also highly valuable metabolic effects in patients with DM, thus solving very complex condition of obesity with insulin resistance. As such, RYGB began to be widely promoted. However, technical difficulty of the the RYGB was stimulating the search for simpler procedures that could comparably modify metabolic disease while maintaining excellent long-term results. That is why OAGB has been gradually becoming established in clinical practice as a technically simpler and feasible alternative to RYGB. Besides sustainable EWL, OAGB positively affects DMT2, dyslipidemia, and arterial hypertension, as well as the other metabolic and obesity-related diseases [27].

Later on, interesting observation that SG indicated as the first stage of BPD-DS in polymorbid high-risk patients appeared to provide comparable EWL as well as metabolic effect, which led to the acceptance of SG as primary BMS procedure. The two main reasons why SG is currently the preferred operation worldwide include excellent long-term results and very good safety profile with minimal number of complications [28].

It is important to point out that correct timing of BMS is crucial for its success. Although indication for surgery is relatively straightforward, patient must undergo thorough preoperative preparation not only for the procedure itself but also for the life after BMS. Therefore, multidisciplinary approach and assessment is inevitable. The team consists of a surgeon, gastroenterologist, internist, nutritionist, clinical psychologist, endocrinologist, diabetologist, and selectively other specialists if needed. Every patient indicated for BMS should undergo behavioral intervention as soon as possible—setting-up an ideal diet, defining lifestyle changes, and designing regular physical activity program in the patient’s routine. The initial effect of this complex behavioral therapy on EWL should subsequently be supported by pharmacotherapy to improve the patient’s adherence to therapy. Only the patient who can successfully complete the preprocedural algorithm should be indicated for BMS with the clear consent. If failure of surgical treatment is reported, it is usually caused by failure to comply with the postoperative regimen in poorly prepared patients [29].

Any malnutritive procedure is potentially dangerous due to the risk of ion imbalance and micronutrient and vitamin deficiency. Although this risk is the same for all the patients in the beginning, there is a huge interindividual variability. Therefore, regular laboratory and clinical checks are necessary after RYGB, OAGB, BPD-DS, and SADI-S. The problem is especially pronounced in non-adherent patients who do not follow the regimen and drop out from regular follow-up, but can occur even in those complying with follow-up [30].

Also of note, the indication criteria for BMS have moved toward the lower BMI limits recently. Generally speaking, a decrease of 5 kg/m² can be noticed. This means that BMS is now available to wider range of patients at the earlier stage of obesity. As higher BMI is associated with more severe obesity-related comorbidities and disabilities as well as perioperative and postoperative complication rates, it appears logical that shift toward lower BMI indications could be linked with better results and subsequently with better quality of healthcare accessible to wider range of patients.

The indication for BMS also used to be limited to an upper age limit of 65 years. This policy is no longer valid as the age alone should not be considered a prohibitive factor. Therefore, the decision is left to the attending surgeon and multidisciplinary team on an individual basis, after careful assessment of biological age, comorbidities, BMS risks, and benefits as well as patient’s preference.

Furthermore, the prevalence of obesity among the population younger than 18 years is increasing. Children and adolescents with severe obesity are at risk of developing and worsening obesity-related comorbidities, especially hypertension, DM, dyslipidemia, and sleep apnea syndrome, as well as facing psychological problems. Lifestyle changes play a crucial role in these patients, but in more severe obesity, those are often insufficient while use of pharmacotherapy is limited in this age group. Therefore, BMS has become indicated for adolescents under 18 years of age with severe obesity. The preferred BMS procedures are SG and RYGB due to their excellent long-term results. However, the indication has to be based on the careful assessment of the multidisciplinary panel, and only after successful preoperative interventions leading to a change in the lifestyle. Also, the compliance of the patients with recommended postoperative regimen and long-term follow-up must be assured as vitamin and mineral supplementation may be necessary. Successful BMS in the pediatric patients with severe obesity improves the overall quality of life, solves the associated comorbidities, and prolongs life expectancy in this subpopulation [31, 32, 33, 34, 35, 36].

It is not uncommon for the initial BMS to fail and thus, re-do surgeries are not unusual. The reasons may vary but they are mostly related either to non-compliance with the postoperative regimen by the patient or inadequate choice of the procedure by the surgeon. Most commonly, BMS reoperations are performed after gastric band removal when SG is usually indicated. In case of failed SG due to dilated gastric sleeve, a re-sleeve gastrectomy can be attempted, but higher complication rate can be expected compared to primary procedure. In case of failed SG without dilatation of the gastric sleeve, modification to OAGB, RYGB, or SADI-S is feasible, thus adding malabsorptive effect to the procedure [37].

Currently, progress may be noted in the pharmacotherapy of obesity as well. Significant weight loss can be achieved by using GLP-1 peptide analog (liraglutide), the dual GLP-1/GIP receptor agonist (tirzepatide), and the triple-hormone-receptor agonist (retatrutide). Randomized controlled trials provided support for the use of liraglutide 3.0 mg for weight management in the adults with obesity or overweight [38]. Recent meta-analysis suggested that tirzepatide led to substantial weight, BMI, and waist circumference reduction for the cost of increased frequency of gastrointestinal symptoms (nausea, vomiting, and diarrhea) compared to placebo [39]. The double-blind, randomized, placebo-controlled trial on 338 adults showed that retatrutide treatment for 48 weeks resulted in substantial reduction in body weight [40]. Although the weight loss under these novel medications appears to be comparable to the results of BMS, future randomized trials are needed to assess the true potential of pharmacotherapy to compete with surgical management.

9. Conclusion

BMS is currently the most successful therapeutic approach to obesity. It provides desirable long-term effects and excellent results if patient complies with the postoperative regimen. Besides weight loss, there are also positive effects on associated metabolic diseases, obesity-related diseases, and overall increase in the quality of life that is achieved. Therefore, BMS has an impact not only from medical point of view but also from psychological, social, and economic one. Prevention of complications related to diseases associated with obesity thus significantly reduces the costs that would have to be spent on their treatment in future. Also of note, obese patients often complain about negative experiences in their social life with tendency to depression. Successful BMS significantly improves their postoperative quality of life both from physical and psychological perspectives.

Acknowledgments

Great thanks belong to Mrs. Anna Pekarova MD., PhD. for the figures illustrations. This study was supported by Specific University Research Grant no. MUNI/A/1547/2023 provided by the Ministry of Education, Youth, and Sports of the Czech Republic. We want to acknowledge the Hospital AGEL Czech Republic for the support in writing this chapter.

Conflict of interest

The authors declare no conflict of interest.