Prevention and treatment of complications from bariatric and metabolic surgery: from perioperative risks to long-term nutritional health

(3) Fistula: Anastomotic fistula of LRYGB or gastric fistula of LSG is one of the most challenging complications of bariatric surgery. Most fistulas occur within the first week after surgery, but some patients experience them as early as one month after surgery. Early clinical symptoms of fistula are not easily detected, and clinical attention should be paid to signs such as low-grade fever, respiratory impairment, or unexplained tachycardia (above 120 beats/min). Imaging can confirm the fistula through gastrointestinal contrast radiography or abdominal CT. For early postoperative fistulas, even if a fistula is clinically suspected, emergency surgical exploration is recommended. For experienced physicians, surgical exploration and treatment of the fistula using laparoscopic methods is usually feasible. Treatment principles: ① Use broad-spectrum antibiotics; ② Confirm and repair the defect; ③ Irrigate and control infection; ④ Ensure adequate drainage of the infected area; ⑤ Establish enteral nutrition. For the treatment of persistent gastric fistulas, surgery is technically difficult and often fails. New methods using minimally invasive endoscopic repair techniques appear to be safe and effective for some patients, including bio-glue and placement of covered stents at the fistula site. (4) Outlet stenosis or obstruction: Clinical manifestations depend on the severity of the obstruction. Typical manifestations include persistent nausea, vomiting, dehydration, gastroesophageal reflux, and dysphagia after surgery, eventually leading to intolerance to oral feeding. Diagnosis can usually be made through endoscopy or upper gastrointestinal contrast radiography. Acute anastomotic stenosis caused by tissue edema can initially be treated conservatively by inserting a nasogastric tube for decompression until the edema is relieved. Endoscopic balloon dilation is the first choice for treating persistent obstruction. For a small number of patients who still have persistent stenosis after repeated dilation, surgical correction is required. Persistent and severe vomiting can seriously disrupt normal eating and greatly reduce energy intake. It is necessary to be alert to water and electrolyte imbalances and Wernicke's encephalopathy. Intravenous glucose, electrolytes, vitamins and trace elements should be supplemented, or supplemental parenteral nutrition support should be provided to avoid complications and irreversible neurological damage caused by malnutrition. (5) Food intolerance, nausea, and vomiting: Postoperative food intolerance is a common problem in any surgical procedure involving functional or anatomical reduction of gastric capacity. After ruling out anatomical factors such as outlet stenosis, vomiting and upper abdominal discomfort may be related to eating too quickly or in too large quantities. Because patients haven't yet adapted to the new eating pattern post-surgery, swallowing too fast or consuming more food than the post-operative "small stomach" can cause vomiting. Symptoms usually subside spontaneously after stopping eating or vomiting, requiring no special medical intervention. However, dietary education should be strengthened, and with the assistance of a nutritionist, new eating habits should be established and adapted to as quickly as possible. Most patients become familiar with and recognize the early satiety caused by the "small stomach" within a few months post-surgery and can control the amount and type of food consumed. Patients commonly report that meat products, bread, rice, and pasta are the foods most likely to cause intolerance. Food intolerances gradually decrease over time post-surgery, but in the long term, patients may still have persistent intolerances to certain foods. Educational support from an experienced nutritionist can help patients achieve better behavioral adaptation and/or use alternative foods. (6) Dumping syndrome and hypoglycemia: Dumping refers to a series of postprandial symptoms caused by the rapid transport of high-energy-density food to the small intestine. These symptoms may be nonspecific, but the Sigstad scoring tool can improve the accuracy of diagnosis. The Sigstad score is calculated based on the weighted coefficients of different symptoms of the syndrome, and a score greater than 7 indicates dumping. Previous views considered dumping syndrome to be a typical complication of RYGB (70%-75% of patients experience it within the first year after surgery), but it has also been reported in patients after SG surgery (40% of patients experience it within 6 months after surgery). In clinical practice, dumping syndrome symptoms can be divided into early-onset and late-onset types, depending on the time it takes for symptoms to appear after eating: early-onset symptoms generally occur about 10-30 minutes after a meal, while late-onset symptoms usually appear 1-3 hours after food intake. Late dumping is closely related to the occurrence of reactive hypoglycemia, possibly related to changes in gastrointestinal hormones and insulin secretion. Dietary adjustments are usually sufficient to control dumping, including eating smaller, more frequent meals, avoiding liquid intake within 30 minutes of eating solid food, avoiding simple sugar intake, increasing dietary fiber and complex carbohydrate intake, and increasing protein intake. Drinking half a cup of orange juice (or taking a supplement with an equivalent amount of sugar) about one hour after eating can also prevent delayed dumping symptoms and reactive hypoglycemia. (7) Wound infection and wound fat liquefaction: Signs of wound infection include unexplained fever, fluctuation, erythema, or effusion. Treatment includes incising the infected area to drain infected effusion or pus, debridement of all devitalized tissue, and antibiotics if the surrounding skin indicates cellulitis. Wound fat liquefaction makes healing difficult. (8) Pulmonary embolism and deep vein thrombosis: Pulmonary embolism remains the most common cause of death in the perioperative period after bariatric surgery, accounting for more than 50% of deaths. The most common risk factors associated with fatal pulmonary embolism include severe venous stasis, BMI > 60 kg/m², trunk obesity, and obesity-hypopnea syndrome. Diagnosing pulmonary embolism after weight loss surgery in morbidly obese patients is very difficult because standard diagnostic methods (e.g., radionuclide lung scan, CT angiography, pulmonary angiography, and/or lower extremity ultrasound) are difficult to implement. Patients with a high clinical suspicion of pulmonary embolism should be immediately anticoagulated; for patients with contraindications to anticoagulation, mechanical filters can be placed in the inferior vena cava to reduce the risk of continued blood clot embolism. (9) Pulmonary complications: atelectasis, respiratory failure, etc. Atelectasis is common after various types of surgery under general anesthesia, and is more common in morbidly obese patients. Early ambulation and stimuli lung volume measurement after surgery are important to reduce the incidence of pulmonary complications. Preoperative confirmation of significant obstructive sleep apnea and initiation of continuous positive airway pressure (CPAP) can also reduce the risk of postoperative pulmonary complications. 2. Long-term postoperative complications (1) Nutrition-related complications: ① Micronutrient deficiency: including vitamin and trace element deficiency, is one of the most common and urgent problems to be solved after weight loss surgery. Prevention, detection and treatment of these deficiencies are the cornerstone of long-term follow-up of obese patients. Patients should follow a proper diet and supplement vitamins for life after surgery. Vitamin B12 deficiency is more common 2 years or longer after bariatric surgery. It is recommended to supplement with 1200-2000 mg/d of elemental calcium and 400-800 IU of vitamin D daily after surgery. Iron deficiency with or without anemia is common after RYGB and BPD-DS surgery, and can also occur after SG. Iron supplements should be given in time if iron deficiency occurs. ② Dysphagia and/or vomiting: Patients often experience vomiting and upper abdominal discomfort if they swallow too quickly or eat more than the capacity of their "small stomach" after surgery. ③ Osteoporosis and fracture: In the short term after bariatric surgery, the patient's bone density is not significantly affected, but over time, it may have adverse effects on the bones, including bone loss, osteoporosis and increased risk of fracture. (2) Psychological, neurological and other systemic complications: Depression may be a coexisting disease before surgery or a manifestation after surgery, and should be given high attention. Neurological complications are mainly caused by vitamin and trace element deficiencies, most commonly vitamin B12, folic acid, and thiamine (vitamin B1). In addition, rapid weight loss can promote the formation of stones by increasing the litholytic activity of bile. Approximately 8% of patients after RYGB surgery are found to have kidney stones. (3) Insufficient weight loss or weight rebound after surgery: Insufficient weight loss after bariatric surgery is common, and most patients will face the problem of weight regain after surgery. Studies have found that 20% to 30% of patients fail to maintain 20% of the weight loss effect within 10 years.