This is the view of Charlie actually drinking the barium contrast. You can see the nipple in his mouth and the contrast going down his esophagus into his stomach. Neat!
When his tummy was full and it was starting to empty through into the pyloric sphincter, they stop feeding him and watch what happens. This is the view of what shouldn't be happening. The top of the stomach doesn't shut properly and all that contrast is just filling his esophagus again, all the way back up to his mouth. Yikes! No wonder he is in pain so often, and I have to go through so many outfits and burp cloths!