Reflux may be due to a mechanical problem with the gastro-oesophageal junction or the stomach. The loss of function at the lower oesophageal sphincter allows acid, food or bile to pool in the lower oesophagus repeatedly. This leads to oesophagitis, erosions/ulcers or even inflammatory strictures.
GERD may also be related to herniation of the stomach up the chest (i.e., hiatal hernia), as the absence of the diaphragmatic pinch by the crura and the negative intrathoracic pressures will encourage retrograde flow of gastric contents.