A sudden inflammation or swelling of the appendix is called appendicitis. The appendix is a tube-like structure that branches off where the large intestine (colon) begins. It's pencil-thin and normally about 10 cm (4 inches) in length.
For many years, scientists were unsure of the function of the appendix in the body. Now we know it helps make immunoglobulins – substances that are part of the immune system. Immunoglobulins are made in many parts of the body, thus removing the appendix does not seem to result in problems with the immune system.
Appendicitis is rarely fatal these days, due to the use of antibiotics and safe surgery. The condition affects 1 in 20 people and strikes men more than women. The incidence of appendicitis decreases with age and hardly ever affects young children or older adults. It occurs most commonly in people between 10 and 30 years of age.