Appendicitis, acute inflammation of the vermiform (wormlike) appendix, a blind tube projecting from the cecum,—the beginning of the large intestine. The appendix, located in the lower right side of the abdomen, is an organ with no known function in humans. If the appendix wall ruptures, infection may spread to the abdominal cavity, causing peritonitis. Symptoms of appendicitis include pain and cramps in the area between the right hip bone and the navel, fever, nausea and vomiting, constipation, and diarrhea. The treatment is surgical removal of the appendix (appendectomy). Although the frequency of appendicitis is highest among young adults, the ailment can affect persons of any age.