Appendicitis is an inflammation of the appendix. Inflammation occurs when the opening of the appendix to the large intestine is blocked by feces, tumors, helminths (a worm classified as a parasite), or indigestible substances such as seeds. The tissue becomes infected by bacteria in the digestive tract. Pus accumulates, the blood supply is impaired, and the appendix may rupture. A ruptured appendix allows digestive contents to enter the abdominal cavity, causing peritonitis—a life-threatening surgical emergency. Early detection of appendicitis may permit treatment before the appendix ruptures.