This procedure is primarily used as part of a staged approach to surgical weight loss. Patients who have a very high body mass index (BMI) or who are at risk for undergoing anesthesia or a longer procedure due to heart or lung problems may benefit from this staged approach. Sometimes the decision to proceed with a two-stage approach is made before surgery due to these known risk factors. In other patients, the decision to perform sleeve gastrectomy (instead of gastric bypass) is made during the operation. Reasons for making this decision intraoperatively include an excessively large liver or extensive scar tissue that would make the gastric bypass procedure too long or unsafe.