Fred has been experiencing recurring episodes of heartburn, especially when he bends over to lace his shoes or when he lies down in bed. His physician believes Fred may have a hiatal hernia. To confirm this diagnosis, she has scheduled Fred for a “barium swallow.” In this test, a barium-containing fluid that blocks x-rays is swallowed so that the stomach appears as a bright mass in a radiograph. If Fred has a hiatal hernia, what should the radiologist see on the radiograph? Can you explain what caused the symptoms that brought Fred in to see his physician?