Bariatric surgery typically requires a multidisciplinary team that evaluates the patient before surgery. This includes a dietitian, a psychiatric specialist, an anesthetist, nursing, surgical team, and the primary care provider. This approach has been shown to improve patient outcomes and decrease the chances of a major postoperative complication.[25][26] The procedure requires an anesthesiologist, a bariatric surgeon, a scrub nurse, a surgical technician, and a resident or first assistant.

The preoperative evaluation should be a multidisciplinary approach that contains a team containing dieticians, psychologists, endocrinologists, anesthesiologists, nurses, physician extenders, cardiologists, and the surgeon.

Psychological Evaluation

Patients must be psychologically fit to undergo bariatric surgery. This will help avoid major postoperative complications.[26] Patients need to be evaluated for psychological disorders such as depression, anxiety, and eating disorders. It is necessary to evaluate the patient's support system that they have available. They should be evaluated for substance misuse disorders, such as alcohol or drug use. If they have alcohol dependence, they will need rehabilitation before planning the procedure. If the patient is smoking, smoking cessation needs to be encouraged before proceeding with the operation. Smoking significantly increases the risk of organ space infection, prolonged intubation, reintubation, pneumonia, sepsis, shock, and longer length of stay in all patients undergoing bariatric surgery.[27] Smoking cessation will improve outcomes.

Nutritional Evaluation and Planning 

The nutritional evaluation includes assessment and education that will direct the patient towards dietary changes needed after surgery. Patients are typically placed on a Low carbohydrate diet before surgery to shrink the liver as much a possible before surgery. Studies have shown that preoperative weight loss may lead to some improvements in postoperative outcomes and possibly decrease complications. Patients who can lose weight before surgery have been shown to have total weight loss following the surgery.[28] It is important for weight maintenance strategies to be discussed with the patients in their nutritional evaluation and also the importance of glycemic control in diabetic patients.

Medical Clearance

As with all surgeries, medical evaluation and clearance are extremely important in the preoperative period. Patients must have a detailed history and physical, a thorough review of their prior surgeries and past medical history. Recent laboratory studies should be performed. Patients' functional status must be determined, and if there is a concern, further workup may be warranted by a cardiologist. Patients who have obstructive sleep apnea need to be evaluated with a sleep study and pulmonologist before surgery. Untreated obstructive sleep apnea can put the patient at increased perioperative risks for complications.[29]

Preoperative Imaging

Currently, there is no consensus regarding the imaging modalities to be obtained before a bariatric procedure. Several studies have evaluated the use of abdominal ultrasounds to evaluate liver pathology, size, and cholelithiasis. Imaging was shown to no change patient outcomes and only increase healthcare costs.[30][31][30]

Oher Preoperative Evaluation

EGD before bariatric surgery remains a controversial topic. Some recommend a preoperative evaluation with EGD before restrictive procedures such as sleeve gastrectomy or an adjustable gastric banding. These restrictive procedures may place these patients at a greater risk of worsening gastroesophageal reflux and Barrett's esophagus. Bypass procedures such as Roux en-Y gastric bypass will result in an inaccessible foregut, which will make a further evaluation of the upper gastrointestinal tract difficult.[32] The current recommendations are that an EGD preoperatively should be performed as an individualized basis and in patients with significant gastrointestinal symptoms.[33][34]

1) Preparation and Patient Positioning

Patients are placed under general anesthesia. Intravenous preoperative antibiotics and thromboprophylaxis are given prior to the start of the procedure. Patients are placed in the supine position with split legs position. Both arms are out to the side. The patient will be secured with straps and tape in order to prevent patient movement with table positioning. Sequential compression devices will be placed on the patient's legs. The patient will then be prepped and draped in a sterile fashion. 

2) Entrance

A 15 cm Veress needle is introduced at palmers point (left subcostal area) to create 15mm HG pneumoperitoneum. A 5 mm or 10 mm optical trocar is placed under direct vision two fingerbreadths below the xiphoid process for the camera. A 12 mm port is placed at the left and right flanks. A 5mm port is placed at the epigastrium for the liver retractor. A 5mm port is placed in the left upper and left lower quadrant.

3) Mobilization of the stomach and Duodenal Dissection

Dissection is begun by opening the gastrocolic ligament at the level of the gastric body. This is done using an ultrasonic scalpel. The greater curvature of the stomach is then mobilized from the antrum to the angle of His. In super obese patients who have a short mesentery and adhesions, sleeve gastrectomy may be performed as a first stage operation.[35][36]

The pylorus is then identified and dissected free. The peritoneum is opened at the inferior and superior edges of the duodenum. The patient's antrum will be pulled to the left to visualized the duodenum better. The common bile duct will be identified on the superior aspect of the duodenum. This can be used as a landmark for further dissection. The duodenum can then be mobilized by the inferior or posterior approach. For the inferior approach, the gastrocolic ligament is divided using the harmonic. The pyloric artery is controlled. A posterior dissection is continued for the first 3 to 4 cm of the duodenum. The gastroduodenal artery is a marker for the limit of the posterior dissection. The duodenum will be divided using a 60 mm linear stapler at this point.

The posterior approach, a window is created 3 to 4 cm distal to the pylorus. Blunt dissection is performed to find the plane between the duodenal wall and the pancreas. Careful dissection is required to avoid small venous branches to the pancreatic head from the gastroduodenal artery. After being fully mobilized, the duodenum will be divided using a 60mm linear stapler at the first portion of the duodenum proximal to the gastroduodenal artery.[35]

4) Sleeve Gastrectomy

Gastric transsection is started from 5 to 7 cm from the pylorus. A linear stapler with 60mm loads is used. The gastric transfection proceeds towards the fundus. A 32-40 french esophagogastric bougie is usually placed for guidance. Hemostasis on the staple line is controlled using clips or a 3-0 absorbable suture. The gastrectomy specimen is placed in a plastic bag and removed through one of the 12 mm trocars.

5) Small Bowel Transection

The patient is placed in the Trendelenburg position with the left side down. The ileocecal junction is identified, and any intrabdominal adhesions between the ascending colon and greater omentum are divided. The length of the metallic part of the laparoscopic bowel graspers (5 cm) is used to measure the alimentary limb. The small bowel is measure 100cm from the ileocecal junction. Then the small bowel is run another 150cm and transected at that level using a 60mm linear stapler. The small bowel mesentery may be opened a few centimeters in order to reduce tension on the duodenal anastomosis.[35]

5) Duodenoileal Anastomosis

The alimentary limb is brought to the right upper quadrant in an ante colic fashion and brought to the transected portion of the duodenum. The omentum is mobilized from the ascending colon to relieve tension on the anastomosis. A handsewn or stapled end to side anastomosis is created. The anastomosis can be tested by insufflating air through the nasogastric tube. Repair sutures can be placed if there is a leak.

6) Ileoileal Anastomosis

The ileoileal anastomosis is then created at 100cm from the ileocecal valve. Following the completion of the anastomosis, the mesenteric window (Petersen window) is closed to prevent an internal hernia. After this has been completed, a routine cholecystectomy and liver biopsy may be performed if warranted.[37]

7) Skin Closure

The trocars are then removed, and the fascia layers of the abdomen are closed at the larger port sites. The skin is then closed with absorbable sutures, and topical skin adhesive or sterile dressings are applied.

As with many surgeries, biliopancreatic diversion with duodenal switch complications can be divided into early and late complications

Common early complications: anastomotic leak and hemorrhage

Anastomotic Leak

The incidence of a gastric or duodenal leak following biliopancreatic diversion with duodenal switch is 1.14% vs. 1.12% for Roux en-Y gastric bypass.[38] The leak site appears to be more common at the duodenoduodenal anastomosis.[39] The risk of leakage from the longitudinal gastric staple line is minimal compared to the leak rate from the gastric staple line in the gastric bypass procedure. These patients may be asymptomatic, but they frequently present with tachycardia, which is usually the first sign. They can also have tachypnea and be febrile. The diagnostic test of choice for an anastomotic leak should be a CT scan with oral and IV contrast, high sensitivity, and specificity. An upper GI series can also be used, but it has a low sensitivity. If the leak is acute (<5 days), they should return to the operating room for exploration with repair and placement of a distal feeding tube.[40]

Hemorrhage

The reported incidence for a postoperative hemorrhage is less than 1% of all gastric bypass surgeries experience bleeding, which requires intervention or transfusion. This can present as intraluminal and extraluminal bleeding. This has likely improved due to improved staple technology. Hemorrhage is more commonly seen with laparoscopic gastric bypass over open procedures.[41] Postoperative hemorrhage is treated at the surgeon's discretion, depending on the patient's clinical picture. For intraluminal bleeding, endoscopic treatment may be necessary but is not very common. Patients who have extraluminal bleeding who are hemodynamically unstable and unresponsive to resuscitation will need to return to the operating room for exploration and repair.

Common late complication: nutritional deficiencies

Nutritional Deficiencies

Biliopancreatic diversion with duodenal switch is the one bariatric procedure associated with the greatest perioperative malnutrition and metabolic-related complications. All patients need to begin supplementation postoperatively. Common nutritional deficiencies that can be seen are Iron deficiency anemia, protein-calorie malnutrition, hypocalcemia, deficiency of the fat-soluble vitamins, vitamin B1, vitamin B12, and folate. Close follow up, and laboratory studies are essential for these patients. If a nutritional deficiency is detected, dietary supplementation is extremely important.[42]

Biliopancreatic diversion with duodenal switch is a common weight loss procedure that is gaining popularity in the US. The procedure is still not as common as sleeve gastrectomy and Roux en-Y gastric bypass. Long term studies have displayed similar outcomes in patients with Roux en-Y gastric bypass, sleeve gastrectomy, and biliopancreatic bypass with duodenal switch. The main differences that have been shown are that patients who are super obese BMI >50 kg/m^2 can lose more weight and maintain weight loss better than the other bariatric procedures. It has also been shown that the biliopancreatic bypass with duodenal switch has a better effect on diabetes and reduction of hyperlipidemia then the other procedures.[43] The caveat is that this procedure requires an adequate follow-up program because there is an increased risk of nutritional deficiencies compared with the other bariatric procedures.

Today the management of obesity has become more and more complicated as the incidence of obesity rises, and the comorbidities associated with it do as well. Now more then ever, the management of obesity requires interprofessional communication. Care coordination between nurses, physicians, extenders, surgeons, pharmacists, and primary care providers can enhance patient-centered care and reduce the incidence of obesity using education, a healthy diet, and exercise. The preventative measure can work if patients are held accountable by the health care team and are compliant. It's important that patients to understand that bariatric surgery does not cure obesity and that weight loss is not always guaranteed. Patients must be educated that without lifestyle change there is a risk that they can gain the weight back after bariatric surgery. Bariatric surgery has been shown to help lose weight which leads to better glucose control and lowering of cholesterol.