The GI surgeon who performed my gastroscopy said that it was a sliding hiatus hernia and that it was small (little over 2cm) at the time of the scope. The nature of sliding hernias means that the herniation can move up further into the thorax at times; I think this is what must happen when symptoms flare up significantly.

I have experienced a wealth of strange symptoms due to the hernia. It can be really hard to live with at times. But then there are other times where it causes little to no interference.

Your mothers case is interesting to me as I recently read a case report of an elderly lady who developed severe recurrent episodes of pulmonary edema and congestive heart failure. The culprit was a very large hiatus hernia!