A blockage, or obstruction, in the appendix can lead to appendicitis, which is an inflammation and infection of your appendix. The blockage may result from a buildup of mucus, parasites, or most commonly, fecal matter. When there’s an obstruction in the appendix, bacteria can multiply quickly inside the organ. This causes the appendix to become irritated and swollen, ultimately leading to appendicitis. The appendix is in the lower right side of your abdomen. It’s a narrow, tube-shaped pouch protruding from your large intestine.