Gastric Bypass is a common operation for weight loss in the severely obese patient. The procedure was developed in the 1960s by Drs. Mason and Ito who observed significant weight loss in a patient undergoing partial gastrectomy for peptic ulcer disease. This surgery was traditionally done with the open approach, and as with any open surgery, there were incidences as high as 20% of an incisional hernia and wound complications as high as 8%. This led to the advent of the laparoscopic approach to improve postoperative outcomes in bariatric patients. The first case series of laparoscopic Roux-en-Y gastric bypass (RYGB) was presented in 1994 by Drs. Wittgrove and Clark, and the largest trial was reported by Nguyen and colleagues in 2001. Much data has proven that the laparoscopic approach to RYGB results in decreases in hospital stay, intraoperative blood loss, postoperative pain, pulmonary complications, and wound infections. Studies have shown a steep learning curve for the laparoscopic gastric bypass, and a possible increased rate of postoperative internal hernia (a surgical emergency.) Despite this, it is now considered safer and more cost-effective than traditional, open RYGB.
Today over 90% of gastric bypasses performed for weight loss are done laparoscopically. Despite being one of the most challenging, minimally invasive operations, it has become the most common foregut surgery performed in the United States. Of the many ways to perform this surgery, the fundamentals of each technique remain the same.
To perform a laparoscopic gastric bypass, the clinician must have a thorough understanding of the entire intraabdominal cavity. There are many different organs involved, but this operation intimately involves the stomach, small intestine, liver, spleen, transverse colon and its mesentery, and diaphragm.
The stomach is perhaps the most important organ to understand anatomically. It is a muscular tube that generally makes a “reversed C” contour when viewed from anterior to posterior. It begins at the lower esophageal sphincter and ends as it continues as the first portion of the duodenum. It is divided into the cardia (just distal to GE junction), fundus (abutting the left diaphragm), body, antrum, and pylorus (most distal portion entering the duodenum). The lesser curvature lies beneath the medial segments of the liver and is attached to it via the gastrohepatic ligament (the lesser omentum). The spleen lies in the left upper quadrant and is attached to the greater curvature of the stomach by the gastrosplenic ligament (containing the short gastric vessels).
The duodenum is divided into four portions. The second portion of the duodenum contains the duodenal papilla which is the opening on the medial portion of the duodenum that allows the common bile duct and pancreatic duct to drain into the alimentary tract. The fourth portion of the duodenum emerges from the retroperitoneum and traverses the transverse mesocolon at the ligament of Treitz to become the jejunum. The jejunum lies in the intraperitoneal cavity and transitions into the ileum, which leads to the large intestine at the ileocecal valve. The average small bowel length is approximately 500 cm but can range from as little as 200 cm to about 800 cm.
There are few indications for laparoscopic gastric bypass in the modern age. In rare cases, a surgeon may consider this procedure for gastric outlet obstruction secondary to tumors or peptic ulcer disease. 
Main Indication for Bariatric Patients
For a patient to be a candidate for any weight loss surgery, they historically must meet the following criteria :
The most common bariatric surgery is the sleeve gastrectomy. Head-to-head comparisons in the recent literature between SG and RYGB and have shown comparable results in excess weight loss and resolution of comorbidities at 5 years postoperatively . The major exception is gastroesophageal reflux disease, which has been shown to worsen in almost one-third of patients undergoing sleeve gastrectomy. A significant percentage of these patients may require conversion to RYGB due to unrelenting symptoms of GERD. This is a relative indication to choose laparoscopic gastric bypass over sleeve gastrectomy when considering weight loss surgery. 
The contraindications for this procedure are generally the same as with any laparoscopic procedure and include the inability to tolerate pneumoperitoneum, uncorrectable coagulopathy, and previous abdominal surgeries (relative c/i) 
Patients with conditions requiring long-term endoscopic surveillance, as well as Barrett esophagus with severe dysplasia, are both contraindications to laparoscopic gastric bypass.
The basic laparoscopic equipment required for this operation includes insufflation with CO2, drapes, monitors, laparoscopic instruments, electrocautery, and trocars.
Contrary to conventional laparoscopic procedures, with bariatric patients, the procedure requires longer trocars as well as longer laparoscopic instruments to accommodate for the thicker abdominal wall.
There are many different techniques to perform a gastric bypass; however, many of the steps and equipment required are uniform:
Patients are required to be seen by a multidisciplinary team before being a bariatric surgery candidate. This includes a nutritionist, a psychiatric specialist, surgical team, and the primary care physician.
For the operative portion, the following personnel is required:
Preoperatively, all patients should receive upper endoscopy with Helicobacter pylori testing, abdominal ultrasonography, pulmonary function tests, and basic laboratory evaluation.
The patient is given preoperative antibiotics 30 minutes before incision as well as venous thromboembolism prophylaxis. Abdominal hair is removed with clippers in the preoperative area. After induction of anesthesia, a Foley catheter is inserted, and an orogastric tube is positioned within the stomach.
The following are common methods and variations that surgeons may perform :
The patient is positioned supine on the operating table with the arms extended and placed on arm boards. The patient is secured to the table with multiple means (tape, velcro, spindle sheet on the patient's pelvis).
The anastomosis generally can be performed with three different techniques:
The evidence behind the use of the different techniques includes the following:
Ninety-day mortality is very low (less than 0.5%). Morbidity of the procedure is classified into early complications and late complications. 
Early Complications (0-30 days)
Further information on complications after gastrectomy is out of the scope of this review article. These are very complex disease processes with specific etiologies, pathophysiologies, and treatments.
The laparoscopic gastric bypass is currently the second most popular weight loss surgery in the United States of America. It has clear benefits over the traditional open approach in terms of cost and patient satisfaction with similar successes. Patients can expect to have approximately 60% excess weight loss and an exceptional long-term resolution of obesity-related comorbidities after laparoscopic gastric bypass. Although there is a steep learning curve, once one has become an experienced surgeon, a laparoscopic gastric bypass can be performed with low morbidity and excellent outcomes.