Having to do with the gastrointestinal (GI) tract or GI system. The GI tract includes the mouth, throat, esophagus, stomach, small intestine, large intestine, rectum, and anus. Food and liquids travel through the GI tract as they are swallowed, digested, absorbed, and leave the body as feces. The GI system includes these organs as well as the salivary glands, liver, gallbladder, and pancreas, which make digestive juices and enzymes that help the body digest food and liquids. Also called GI.