The appendix is a blind ended muscular pouch situated in the right lower quadrant of the abdomen, at the junction between the small intestine and the caecum. It is argued that the appendix has no physiological function, yet there is some evidence to suggest that it may have a role in the immune system1. However, this evidence is equivocal.
Appendicitis is secondary to an obstruction in the appendiceal lumen, the potential causes of which are noted in Box 1.
Whatever the cause of the obstruction, ulceration of the mucosal lining within the appendix occurs early on. This facilitates bacterial invasion of the muscularis propria, causing the production of pus, and is described as suppurative appendicitis. Prolonged obstruction leads to oedema, elevated intraluminal pressure and ischaemic necrosis of the mucosa. The ischaemia can eventually lead to gangrene and subsequent perforation of the appendix.