Appendicitis is a condition characterized by inflammation of the appendix. It is classified as a medical emergency and many cases require removal of the inflamed appendix, either by laparotomy or laparoscopy. Untreated, mortality is high, mainly because of the risk of rupture leading to peritonitis and shock. Reginald Fitz first described acute and chronic appendicitis in 1886, and it has been recognized as one of the most common causes of severe acute abdominal pain worldwide. A correctly diagnosed non-acute form of appendicitis is known as "rumbling appendicitis".
The term "pseudoappendicitis" is used to describe a condition mimicking appendicitis. It can be associated with Yersinia enterocolitica.