Appendicitis means inflammation of the appendix. It is thought that appendicitis begins 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.n alternative theory for the cause of appendicitis is an initial rupture of the appendix followed by spread of bacteria outside of the appendix. The cause of such a rupture is unclear, but it may relate to changes that occur in the lymphatic tissue that lines the wall of the appendix, for example, inflammation.