3. Reflux
A hernia might also cause the stomach to protrude upwards through the diaphragm and into the chest.
The diaphragm of course is the sheet of muscle that is responsible for breathing and it is found along the divide between the abdomen and the chest. Thus, you might not actually notice a lump in this case making it harder to spot and diagnose.
However, the clue in this case is more likely to be gastrointestinal distress and reflux. This is caused by the stomach leaking its contents back into the esophagus, causing burning and causing the food to be brought back up.
This form of hernia is most commonly experienced by those over 50 years old.