Appendicitis is a painful swelling of the appendix, a finger-like pouch connected to the large intestine.
It's located in the lower right-hand side of the abdomen (tummy).
The condition starts as a pain in the centre of the abdomen. It then travels to the lower right-hand side and gradually gets worse.
Appendicitis is a medical emergency that usually requires urgent surgery to remove the appendix. If left untreated, the appendix can burst and cause potentially life-threatening infections.
It's not exactly clear what the causes of appendicitis are, although it's thought to occur when something, usually a small piece of faeces, blocks the entrance of the appendix, causing it to swell.
Appendicitis typically starts with a pain in the middle of your abdomen (tummy) that may come and go. Within hours the pain travels to the lower right-hand side, where the appendix lies, and becomes constant and severe.
Read more information about the symptoms of appendicitis.
When to get help
See your GP or contact your local out-of-hours service if you're having abdominal pain that's getting worse.
Call 999 for an ambulance if you get a pain that suddenly gets much worse and spreads across your abdomen. These are signs that your appendix may have burst.
Read more information about the complications of appendicitis.
In most cases of appendicitis, the appendix will have to be surgically removed. Removal of the appendix is one of the most common operations in the UK, and its success rate is excellent.
Surgery is most commonly performed as keyhole surgery (laparoscopy), consisting of three small cuts. Open surgery (a single large cut over the appendix area) is usually carried out if the appendix has burst.
The medical name for this type of surgery is an appendectomy.
Read more information about treating appendicitis.
Appendicitis is a common condition. About 7% of people in the UK will get appendicitis at some point in their life.
The condition is more common in men than in women. It normally occurs in people between 10 and 20 years old.
Although there's no guaranteed way of preventing appendicitis, it's thought to be less common among people who eat a high-fibre diet.