Appendicitis is inflammation of the appendix. It is thought that appendicitisbegins when the opening from the appendix into the cecum becomes blocked. The blockage may be due to a build-up of thick mucus within the appendix or to stool that enters the appendix from the cecum. The mucus or stool hardens, becomes rock-like, and blocks the opening. This rock is called a fecalith.
At other times, the lymphatic tissue in the appendix may swell and block the appendix. Bacteria that normally are found within the appendixthen begin to invade (infect) the wall of the appendix. The body responds to the invasion by mounting an attack on the bacteria, an attack called inflammation.
If the inflammation and infection spread through the wall of the appendix, the appendix can rupture. After rupture, infection can spread throughout the abdomen; however, it usually is confined to a small area surrounding the appendix (forming a peri-appendiceal abscess).