Last updated: 04 October 2011
A hernia happens when an internal part of the body, such as an organ, pushes through a weakness in the surrounding muscle or tissue wall.
A hiatus hernia occurs when part of your stomach pushes up into your chest (the stomach normally sits in your abdomen). It squeezes through an opening in the diaphragm, which is the large, thin sheet of muscle separating your chest from your abdomen.
The opening in your diaphragm is called the hiatus, and your oesophagus (the tube that carries food to your stomach) normally passes through this to reach your stomach.
At the base of the oesophagus is a ring-like muscle, called a sphincter, which closes the lower oesophagus. This muscle acts as a one-way valve, preventing stomach contents from flowing upwards into the oesophagus.
When part of your stomach pokes through the hiatus, it prevents the muscle from closing the lower end of the oesophagus.
A hiatus hernia can cause highly irritating stomach contents, such as acid, to move up into the oesophagus. This can cause heartburn and other problems, although in many cases a hiatus hernia causes no symptoms (see Symptoms).
If there are symptoms, antacid medicines and a change of lifestyle are the preferred treatments (see Treatment).
Who is affected?
Hiatus hernia can affect anyone, but it is more common in women and people who are over 50, overweight, pregnant or who smoke. It is estimated that a third of people over 50 have a hiatus hernia (see Causes).
There is a rare type of hiatus hernia that affects newborn babies.
Continue to next section: Symptoms of a hiatus hernia