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What Is Appendicitis?

Appendicitis is an inflammation of the appendix, a 3 1/2-inch-long tube of tissue that extends from the large intestine. The appendix contains specialized tissue that can produce antibodies, but no one is absolutely certain what its function is. One thing we do know: We can live without it, without apparent consequences.

Appendicitis is a medical emergency that requires prompt surgery to remove the appendix. Left untreated, an inflamed appendix will eventually burst, or perforate, spilling infection into the abdominal cavity. This can lead to peritonitis, a serious infection of the abdominal cavity's lining (the peritoneum) that can be fatal unless it is treated quickly with strong antibiotics.

Sometimes a pus-filled abscess forms outside the inflamed appendix. Scar tissue then "walls off" the appendix from the rest of the abdomen, preventing infection from spreading. An abscessed appendix is a less urgent situation, but unfortunately, it can't be identified without surgery. For this reason, all cases of appendicitis are treated as emergencies.

In the United States, 1 in 15 people gets appendicitis. Although it can strike at any age, appendicitis is rare under age 2 and most common between ages 10 and 30.

What Causes It?

Appendicitis occurs when the tube-shaped appendix becomes blocked, often by fecal material, a foreign body, or cancer. Blockage may also occur from infection, since the appendix swells in response to any infection in the body. As it expands, its opening gradually closes.