A hiatus hernia means that part of your stomach has squeezed through an opening in your diaphragm and into your chest.
The stomach normally sits in the abdomen, underneath a large, thin sheet of muscle called the diaphragm (see diagram on this page).
The opening in the diaphragm that the stomach can push through is called the hiatus. Your oesophagus (tube that carries food to your stomach) passes through the hiatus to reach your stomach.
How a hiatus hernia can cause heartburn
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.
This means a hiatus hernia can cause highly irritating stomach contents, such as acid, to pass up into the oesophagus. It can cause heartburn and other problems, although in many cases a hiatus hernia causes no symptoms (see Hiatus hernia - symptoms for more information).
Who is affected
Hiatus hernia can affect anyone, but it's more common in women and people who are over 50, overweight, pregnant or who smoke. It's estimated that a third of people over 50 have a hiatus hernia (see Hiatus hernia - causes for more information).
There's a rare type of hiatus hernia that affects newborn babies.
What can be done
Medicines such as antacids can help to relieve symptoms of a hiatus hernia. Surgery may be an option in some cases if medication doesn't work (see Hiatus hernia - treatment for more information).
If the hiatus hernia isn't causing symptoms, treatment is not necessary.
