Appendicitis is an inflammation of the appendix, a long, thin pouch attached to the colon on the right side of the abdomen. Although the appendix serves no known purpose, experts believe that at one time the organ may have played a role in digestion.

When the appendix becomes inflamed and then infected and fills with pus, it causes pain that begins near the navel and gradually moves to the lower right abdomen. Over time, this pain may become severe, and the appendix may rupture. This can lead to a life-threatening infection called peritonitis, and requires immediate medical attention.

Appendicitis can affect people of all ages, although it is more common between the ages of 10 and 30. It is rare in children younger than 1, and is most common in adolescents.

Although the exact cause of appendicitis is not always known, it appears that several different factors can trigger the condition. Infection in the digestive tract may allow bacteria to invade the appendix, leading to inflammation and the formation of pus (infection). In some cases, food waste or a hard piece of stool (called a fecal stone or fecolith) can become lodged in the entrance to the appendix or inside the cavity (lumen) that runs its length. This fecolith may be seen on an abdominal x-ray.

In rare cases, a traumatic injury to the abdomen can trigger appendicitis. Genetics may also play a role, as appendicitis sometimes runs in families. This may be the result of a genetic factor that leaves a person more vulnerable to obstruction of the appendix.

Surgical removal of the appendix (appendectomy) is the standard treatment for appendicitis and is the most common emergency surgical procedure of the abdomen, according to the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK).

In most cases, surgery can provide quick and effective treatment of appendicitis with few complications. However, it is important to treat this condition promptly to prevent infections, such as peritonitis. In rare cases, appendicitis may be fatal.