Technique selection, indication assessment, and clinical implementation of bariatric and metabolic surgery

Metabolic surgery methods and indications

Over the past 60 years, bariatric surgery has seen the development of more than 20 surgical techniques in clinical practice. Despite the diverse surgical designs, these techniques can be categorized into three types based on their weight loss mechanism: restricting nutrient intake, reducing intestinal absorption, and a combination of both. They can also be categorized by anatomical approach: altering only the stomach, altering only the intestines, and altering the anatomy of both the stomach and intestines. According to recent global data from the International Federation for Surgery in Obesity and Metabolic Disorders (IFSO) in 2018 and US data from the American Society for Surgery in Metabolic and Obesity (ASMBS) in 2019, the number of bariatric surgeries performed globally, from most to least, is as follows: laparoscopic sleeve gastrectomy (LSG), laparoscopic Roux-en-Y gastric bypass (LRYGB), laparoscopic adjustable gastric banding (LAGB), and bile-pancreatic diversion with duodenal transposition (BPD-DS). Thanks to advancements in medical materials and instruments, endoscopic weight loss procedures are rapidly developing and are already being used clinically. These include intragastric balloon (IGB), endoscopic sleeve gastrectomy (ESG), endoscopic sleeve cannula placement, duodenojejunal bypass (EDJBS), gastric drainage (AT), and gastric electrical stimulation (GES). (1) LSG: This procedure reduces the volume of the stomach only. The entire fundus and greater curvature of the stomach are removed along the 3236Fr gastric tube that serves as a gastric support, ultimately forming a sleeve stomach with a volume of approximately 60-80 ml. This procedure maintains the original gastrointestinal anatomy and can alter some gastrointestinal hormone levels, resulting in a better improvement in glucose metabolism and other metabolic indicators in obese patients. The excess weight loss percentage (EWL%) after 2 years post-surgery is on average 65%-75%, and LSG is the first choice for the vast majority of obese patients with metabolic syndrome. (2) LRYGB: This is a surgical procedure that simultaneously restricts intake and reduces absorption. A small gastric pouch with a volume of 1530ml is created below the cardia, leaving the entire gastric fundus open. It is then anastomosed with a 75-150cm segment of the small intestine Roux branch (also known as the food branch). The Chinese guidelines for the surgical treatment of obesity and type 2 diabetes recommend that the sum of the lengths of the food branch and the bile-pancreatic branch should be >200cm (which can be adjusted according to the patient's BMI, the severity of T2DM, and specific circumstances). This procedure has a good weight loss effect, with an average EWL% of 70%-80% after 2 years post-surgery. It can also significantly improve glucose metabolism and other metabolic indicators. For obese patients with moderate to severe reflux esophagitis or severe metabolic syndrome, or for super-obese patients, LRYGB can be considered as the preferred choice. (3) BPD-DS: This is a surgical procedure that mainly reduces the absorption of nutrients. Based on LSG, the pylorus of the stomach is preserved and transected in the upper part of the duodenum. The small intestine is transected about 250cm from the ileocecal valve. The distal end of the duodenal transect is closed with an anastomosing device, and the proximal end of the duodenal transect is anastomosed with the distal end of the small intestine. The proximal end of the small intestine transect is anastomosed with the ileum at a distance of 50-100 cm from the ileocecal valve. This procedure is superior to other procedures in terms of weight loss and metabolic index control. The average EWL% after 2 years is over 80%. The disadvantage is that the operation is relatively complicated, and the risk of nutritional deficiency increases with the shortening of the common intestinal length. The incidence of complications and mortality are higher than other procedures. BPD-DS is mainly used for super-obese patients (BMI>50kg/m²), obese patients with severe metabolic syndrome, or patients with a long history of T2DM, provided that postoperative vitamin and nutrient supplementation can be guaranteed. (4) LAGB: It is a simple restrictive surgery that separates the upper part of the stomach by placing a tight, adjustable artificial band around the stomach entrance. The advantage is that the stomach is not cut open or the intestine is removed, but it is rarely used now due to its high postoperative correction rate and weight rebound.

The indications for bariatric surgery, as outlined in the "Guidelines for Surgical Treatment of Obesity and Type 2 Diabetes in China (2019 Edition)," are as follows: ① For patients with a BMI ≥ 37.5 kg/m², surgery is recommended; for those with a BMI ≤ 32.5 kg/m² < 37.5 kg/m², surgery is recommended; for those with a BMI ≤ 27.5 kg/m² < 32.5 kg/m², whose obesity is difficult to control with lifestyle modifications and medical treatment, and who meet at least two components of metabolic syndrome or have comorbidities, surgery may be considered after comprehensive evaluation. ② For men with a waist circumference ≥ 90 cm and women with a waist circumference ≥ 85 cm, and whose imaging findings suggest central obesity, the recommendation level for surgery may be increased after extensive consultation with a multidisciplinary team (MDT). ③ The recommended age for surgery is 16-65 years. Indications for surgery in patients with type 2 diabetes mellitus (T2DM): ① T2DM patients still have some insulin secretion function; ② BMI ≥ 32.5 kg/m², surgery is recommended; 27.5 ≤ BMI < 32.5 kg/m², surgery is recommended; 25 ≤ BMI < 27.5 kg/m², blood glucose is difficult to control with lifestyle modifications and medication, and at least two components of metabolic syndrome are met, or comorbidities exist, surgery should be performed with caution. ③ For patients with 25 ≤ BMI < 27.5 kg/m², waist circumference ≥ 90 cm for men and ≥ 85 cm for women, and imaging examinations indicating central obesity, the recommendation level for surgery may be increased after extensive consultation by a multidisciplinary team (MDT). ④ The recommended age for surgery is 16-65 years. For patients under 16 years of age, a multidisciplinary team (MDT) discussion involving nutrition and developmental pediatrics is necessary to comprehensively assess feasibility and risks. Informed consent must be obtained after thorough explanation, and widespread implementation is not recommended. For patients over 65 years of age, their health status, comorbidities, and treatment history should be carefully considered. An MDT discussion should be conducted to fully assess cardiopulmonary function and surgical tolerance. Informed consent must be obtained before surgery is performed cautiously. II. Complications of Metabolic Surgery Different bariatric surgical procedures have slightly different rates of perioperative and long-term complications. Generally, with the continuous improvement of surgical instruments and laparoscopic techniques, the perioperative safety of bariatric surgery has significantly improved. IFSO data from 2016 showed that the 30-day postoperative mortality rate in well-established obesity treatment centers in Europe had dropped to 0.012%. However, since all surgical methods involve remodeling the anatomy or physiology of the gastrointestinal tract, patients need to adapt to the new gastrointestinal physiological state after surgery. Long-term postoperative risks of nutritional, surgical, and psychological complications are increased, as are long-term issues such as weight loss failure, weight regain, and recurrence of complications.

Perioperative complications (1) Intraoperative injury: Some super-obese patients have thick abdominal walls and a large amount of visceral fat, making visualization difficult and surgery more challenging. Intraoperative complications such as cannula injury, splenic rupture, portal vein injury, etc. may occur, which are very rare. (2) Postoperative bleeding: Early bleeding usually occurs at the surgical anastomosis or suture site, which may occur inside or outside the digestive tract, but most often in the gastrointestinal tract. Common clinical manifestations are tachycardia, decreased hematocrit and melena. This type of bleeding generally does not require surgical intervention, but may require transfusion of blood products and reversal of anticoagulation; patients with persistent bleeding who require large blood transfusions need careful endoscopic examination and hemostatic treatment; patients with hemodynamic instability, who are not suitable for endoscopic treatment, or who continue to bleed even after coagulation function has returned to normal need emergency surgical treatment.