Appendicitis is inflammation and infection of the appendix.
The appendix is a small finger-shaped tube projecting from the large intestine near the point where it joins the small intestine. The appendix may have some immune function, but it is not an essential organ.
Except for trapped hernias, appendicitis is the most common cause of sudden, severe abdominal pain and abdominal surgery in the United States. Over 5% of the population develops appendicitis at some point. Appendicitis most commonly occurs during adolescence and in the 20s but may occur at any age.
The cause of appendicitis is not fully understood. However, in most cases, a blockage inside the appendix probably starts a process. The blockage may be from a small, hard piece of stool, a foreign body, or, rarely, even worms. As a result of the blockage, the appendix becomes inflamed and infected. If inflammation continues without treatment, the appendix can rupture. A ruptured appendix spills bacteria-laden intestinal contents into the abdominal cavity, causing peritonitis (inflammation and usually infection of the abdominal cavity), which may result in a life-threatening infection. A rupture also may cause a pus-filled pocket of infection (abscess) to form. In a woman, the ovaries and fallopian tubes may become infected, and the resulting blockage of the fallopian tubes may cause infertility. A ruptured appendix also may allow bacteria to infect the bloodstream—a life-threatening condition called sepsis (see Bacteremia, Sepsis, and Septic Shock: Sepsis and Septic Shock).
Fewer than 50% of people with appendicitis have the traditionally described symptoms in which pain begins in the upper abdomen or around the navel; then nausea and vomiting develop; and then, after a few hours, the nausea passes, and the pain shifts to the right lower portion of the abdomen. When a doctor presses on this area, it is tender, and when the pressure is released, the pain may increase sharply (rebound tenderness). A fever of 100° to 101° F (37.7° to 38.3° C) is common. Moving and coughing increase the pain.
In many people, particularly infants and children, the pain may be widespread rather than confined to the right lower portion of the abdomen. In older people and in pregnant women, the pain may be less severe, and the area is less tender.
If the appendix is ruptured, pain and fever may become severe. Worsening infection can lead to shock (see Shock).
A doctor may suspect appendicitis after reviewing the person's symptoms and examining the abdomen. Typically, exploratory surgery is done immediately if the doctor strongly suspects appendicitis. If the diagnosis is not clear, doctors usually do an imaging test such as computed tomography (CT) or ultrasonography. Ultrasonography is particular useful in children, in whom it is important to limit radiation exposure. Doctors can also do a laparoscopy (see Diagnosis of Digestive Disorders: Laparoscopy) to help determine the diagnosis. A blood test often shows a moderate increase in the white blood cell count because of the infection.
Prognosis and Treatment
With an early operation, the chance of death from appendicitis is very low. The person can usually leave the hospital in 1 to 3 days, and convalescence is normally quick and complete. However, older people often take longer to recover. Without surgery or antibiotics (as might occur in a person in a remote location without access to modern medical care), more than 50% of people with appendicitis die.
For a ruptured appendix, the prognosis is more serious. Decades ago, a rupture was often fatal. Surgery and antibiotics have lowered the death rate to nearly zero, but repeated operations and a long convalescence may be necessary.
Surgery is the main treatment. In nearly 15% of exploratory operations for appendicitis, the appendix is found to be normal. However, delaying surgery until the cause of the abdominal pain is certain can be fatal: An infected appendix can rupture less than 24 hours after symptoms begin. If appendicitis is found, antibiotics are given by vein and the appendix is removed (appendectomy). If the doctor performs an operation and appendicitis is not found, the appendix is usually removed anyway.
Last full review/revision October 2012 by Parswa Ansari, MD