Health Topics A-to-Z
What Is It? Appendicitis is an inflammation of the appendix, a small, fingerlike tube that hangs from the lower right side of the large intestine. The purpose of the appendix is not known. It usually becomes inflamed because of an infection or an obstruction in the digestive tract. If untreated, an infected appendix can burst and spread the infection throughout the abdominal cavity and into the bloodstream.