The presence of gastric secretions and bile in vomit indicates that the material being expelled has come from the small intestine. When bile is involved, it suggests that the contents have moved beyond the stomach and into the duodenum, which is the first part of the small intestine. This is because bile is produced in the liver and stored in the gallbladder, and it is released into the small intestine to aid in the digestion of fats.
In cases where vomit contains only clear fluid or gastric secretions without bile, it typically indicates that the vomiting is originating from the stomach itself. Furthermore, if the vomit were from the esophagus or large intestine, bile would not be present, as these areas are not associated with the pancreatic and hepatic output that creates bile. Thus, the presence of bile is a key indicator of the source of vomiting being the small intestine rather than the stomach or any other digestive area.