Authored by Dr Mary Lowth, 01 Aug 2017

Patient is a certified member of
The Information Standard

Reviewed by:
Dr Adrian Bonsall, 01 Aug 2017

Appendicitis is inflammation of the appendix, a small pouch on the gut wall at the start of the large intestine. It is a medical emergency as, left untreated, the appendix can burst or perforate.

The appendix is a small, blind-ended tube that comes off the caecum, which is the very first part of the large bowel (large intestine). In the vast majority of people the appendix is located in the bottom, right-hand quarter of the tummy.

The appendix is normally about 5-10 cm long, but quite narrow. It has muscular walls, like the intestine, and there is some immune tissue in those walls. Scientists used to believe that the appendix had no useful role in modern humans. They thought that our ancestors had needed the appendix only to digest tough food like tree bark. However, more recently it has been suggested that the appendix may contains a reservoir of helpful digestive bacteria and that, in early childhood, the immune tissues in the appendix are important in the development of the immune system. Despite all this it seems that removing the appendix leaves no ill effects.

Diagram of the bowel showing an inflamed appendix

Appendicitis is painful, although the severity of the pain can vary. The inflamed appendix becomes infected with germs (bacteria) from the intestine. Once it becomes inflamed, the appendix gradually swells and fills with pus. Eventually, if not treated, the swollen appendix becomes weakened, and can burst (perforate). This is very serious, as the contents of the intestine can then leak into the tummy (abdominal) cavity. Here they may cause a serious infection of the membrane that lines the abdomen (a condition called peritonitis), or a collection of pus (an abscess) in the abdomen. So, if appendicitis is suspected, early treatment is needed before it bursts.

The main symptom of appendicitis, at first, is tummy pain, which may start in the centre of the abdomen around the belly button, and which gets worse over a period of hours.

Read more about the symptoms of appendicitis.

Appendicitis is thought most often to be caused by blockage of the appendix 'tube' either by something stuck on the inside, or by swelling of the appendix wall. Blockage may be by trapped seeds, indigestible food remnants or hard stools (faeces) that get stuck in the appendix, or by lymph glands in the appendix wall which have swollen in response to infection elsewhere in the body.

If the appendix is inflamed and swollen, and cannot empty, then germs (bacteria) may thrive and cause inflammation in the wall and behind the blockage in the 'dead end' of the appendix.

Appendicitis is common and can affect anyone of any age. Teenagers and young adults are the most commonly affected. About 1 in every 7 people in the UK have appendicitis at some time in their lives. Appendicitis can develop at any age but it is most common between 10 and 20 years of age. It is very rare under the age of 2 years.

It is slightly more common in women than in men and is much more common in western countries. This is thought to be partly due to the western diet which is often low in fibre. It is rare in rural parts of the developing world.

Further reading and references

Good morning/evening! I'm hoping someone can help me or advise further, I had my appendix removed, via keyhole surgery on the 16th July. The pain was horrible! I even nearly passed out which has...

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