What causes appendicitis?

The appendix is a small, closed tube about the size of a finger. It attaches to the beginning of the large intestine, where the small and large intestines meet. The appendix is open at the end where it connects to the large intestine. It is closed at the other end. Material can move in and out of the appendix but it has nowhere else to go. Like the small intestine, the appendix can contract. Also like the small intestine, it has a secreting lining.

If the open end of the appendix becomes plugged for some reason - maybe because of swelling or maybe because something from the large intestine becomes stuck in the opening - then the secretions from the appendix's lining make the appendix swell. That swelling shuts off the blood supply, causing the appendix tissue to die. An operation to remove the swollen appendix (called an appendectomy) is the only way to fix the problem. If it isn't removed, the appendix eventually bursts. This can be fatal if untreated.

The appendix does not appear to do anything. Sometimes, people traveling to foreign countries or on expeditions will have their appendices removed proactively to prevent the possibility of a problem.

The cause of appendicitis is not always known, but some common causes include:
- blockage from stool that becomes trapped
- an infection from a stomach (GI) infection

Whatever the cause, appendicitis is a medical emergency.  It must be treated right away with surgery to prevent any complications.