Under normal circumstances the junction between the bottom end of the gullet (oesophagus) and the top of the stomach (called the gastro-oesophageal junction or GOJ) is at the level of the breathing muscle (diaphragm) at the bottom of the rib cage. In some people the GOJ is above the diaphragm and therefore in the chest: the stomach has been pushed (or herniated) through the opening (or hiatus) in the diaphragm leading to a hiatus hernia.There are 2 main types of hiatus hernia: sliding or rolling (or para-oesophageal).The former is much more common; the latter occurs more commonly in the elderly. As a result of this disruption of the normal muscular barrier, acid produced by the stomach may move more freely into the lower oesophagus leading to gastro-oesophageal reflux disease or GORD.

A hiatus hernia is usually diagnosed at upper gi endoscopy or less commonly, following an X-ray study called barium swallow.

Most patients with a hiatus hernia respond to life-style measures such as weight loss and eating smaller meals more frequently or taking drugs (H2-receptor antagonists, such as ranitidine or proton pump inhibitors, such as omeprazole) to control symptoms. Occasionally however surgery (Nissen fundoplication) may be required to correct the mechanical defect.