Appendicitis (ap-pen-di-SY-tis) is the inflammation of the appendix (ap-PEN-dix), which is a small organ that branches off the large intestine. The inflammation usually begins abruptly; causes a characteristic right-sided abdominal pain; and may lead to rupture or bursting of the appendix and to severe illness.

What Is Appendicitis?

Acute * appendicitis occurs when the appendix becomes inflamed. An inflamed appendix must be removed so that it does not rupture (break) and spread the infection to the rest of the abdomen, a condition known as peritonitis * . The appendix has no known function, and its removal has no adverse effect on the body.

In most cases, acute appendicitis begins with an obstruction of the appendix's interior cavity, known as the lumen. The appendix is a narrow finger-shaped tube, usually three to six inches (7.6–15.2 cm) long, that branches off the large intestine into the lower right side of the abdomen * . It is also known as the vermiform appendix. Vermiform means worm-shaped. The appendix may become blocked for many reasons. Often, feces obstructs the appendix; but in some cases, a bacterial or viral infection may cause lymph nodes to swell—called lymphoid hyperplasia—and obstruct the appendix. The blockage leads to inflammation. Appendicitis is typically treated with an appendectomy (ap-pen-DEK-to-mee), which is the surgical removal of the appendix. If appendicitis is left untreated, it can be fatal, but it is rare for anyone not to receive treatment in time.

Appendicitis occurs when the appendix, attached to the first part of the large intestine, becomes infected with bacteria and inflamed.

Appendicitis occurs when the appendix, attached to the first part of the large intestine, becomes infected with bacteria and inflamed.
Illustration by Frank Forney. © 2016 Cengage Learning®.

Close-up of recent appendix surgery scar.

Close-up of recent appendix surgery scar.

Who Gets Appendicitis?

Appendicitis is not preventable. Each year in the United States, it affects about one in 500 people. Anyone can develop appendicitis, particularly those under age 40, but it is most common in young people between the ages of 8 and 14, and it affects boys more often than girls. In all, about 7 percent of the population typically has appendicitis sometime during their lifetime.

What Happens to People with Appendicitis? David's Story

David's appendicitis happened suddenly, when he awoke at 1 AM with a terrible bellyache. He blamed it on the chips and ice cream he had eaten after dinner and tried to go back to sleep. By 7 AM, his bellyache was worse; he was not hungry; and he felt very hot. He told his parents about the intense pain in his right side, and they took him to see the doctor immediately. A series of events followed rapidly.

March 2, 10 AM

The doctor asked David numerous questions about the pain: Is it constant? Does the right side hurt the most? Is the pain worse when you move, cough, or take a deep breath? Are you nauseated? David said yes to all of them. His abdomen felt hard when the doctor touched it, and when the doctor pushed on the right lower part, David yelled. A nurse took David's temperature and a blood sample.

March 2, noon

David's blood test showed more white blood cells than usual, which is one of the signs of inflammation. The boy's other symptoms of fever and abdominal pain led the doctor to diagnose appendicitis and to advise David's parents to check him into the hospital.

March 2, 8 PM

David had been at the hospital for several hours, during which the nurses continued monitoring his condition. The pain did not go away and started to get worse. The doctor decided that David should be taken to the operating room right away to have an appendectomy. To prepare the patient for the surgery, the doctor explained anesthesia * and showed David where the surgeon would make a small cut in his abdomen to remove the diseased appendix. The doctor and nurses repeatedly reassured David and his parents that an appendectomy is a common surgery.

March 2, 10 PM

David awoke in the hospital recovery room, groggy, tired, and a little sore. His appendix, which had not yet ruptured, had been removed.

March 4, 8 AM

David went home from the hospital, minus his appendix and with a slight soreness at the site of his appendectomy scar, but otherwise healthy.

Within several weeks, David was back to doing just about everything he had done before his bout with appendicitis. His appendectomy had been a complete success.


Books and Articles

Kolata, Gina. “Antibiotics Are Effective in Appendicitis, Study Says.” New York Times, June 16, 2015. (accessed March 21, 2016).

Parlikar, Urmila. “Surgery Still Trumps ‘Antibiotics First’ Approach to Appendicitis.” Harvard Health Publications. May 14, 2015. (accessed March 21, 2016).


MedlinePlus. “Appendicitis.” U.S. National Library of Medicine, National Institutes of Health. (accessed March 21, 2016).


American College of Gastroenterology. 6400 Goldsboro Rd., Suite 200, Bethesda, MD 20817. Telephone: 301-263-9000. Website: (accessed March 21, 2016).

National Institute of Diabetes and Digestive and Kidney Diseases. 2 Information Way, Bethesda, MD 20892-3570. Toll-free: 800-891-5389. Website: (accessed March 21, 2016).

* acute describes an infection or other illness that comes on suddenly and usually does not last very long.

* peritonitis (per-i-to-NI-tis) is inflammation of the peritoneum (per-i-to-NE-um), which is the membrane that lines the abdominal cavity.

* abdomen (AB-do-men), commonly called the belly, is the portion of the body between the thorax (THOR-aks) and the pelvis.

* anesthesia (an-es-THEE-zha) is a state in which a person is temporarily unable to feel pain while under the influence of a medication.

Disclaimer:   This information is not a tool for self-diagnosis or a substitute for professional care.

(MLA 8th Edition)