The precise cause of appendicitis is not entirely clear. However, the two most likely causes are thought to be:
- infection - possibly a stomach infection that has travelled to the site of the appendix, and
- obstruction - for example, a hard piece of stool (faeces) that gets trapped in your appendix, and the bacteria in the stool then infects the appendix.
Once bacteria gets into your appendix, they rapidly multiply, causing the appendix to swell and become filled with pus.
If appendicitis is left untreated, your appendix will burst and the bacteria that is released may then go on to infect other parts of your body, such as the lining of your abdomen (peritonitis), or the blood (sepsis).
