Efferent loop syndrome is one of two "loop syndromes" that can occur after some types of gastric surgery. In a loop syndrome, a portion or "limb" of the small intestine becomes blocked.
This blockage can happen because of a hernia within the small intestine, which becomes trapped and blocked. It can also happen because of blockage from an adhesive band or kinking because of scarring or poor reconstruction during the weight-loss surgery. In some cases, part of your intestine may slide inside another part of the intestine (called intussusception), causing an efferent loop blockage.