The upper gastrointestinal tracts contour can be seen with the use of barium testing. On standard images, the gut (gastrointestinal tract) does not appear particularly clearly. On the other hand, when you consume a white beverage that includes the chemical barium sulphate, the shape of the upper digestive tract including the oesophagus, stomach, and small intestine is plainly visible on images. This is so that s cant penetrate barium.