Appendicitis

Risk: Appendicitis is slightly more prevalent among men than women, with a lifetime risk of 8.6% for males and 6.7% for females; the peak incidence is between 10 to 30 years of age, with up to 7% of the population affected (Guzman). There is a familial predisposition for appendicitis.

Incidence and Prevalence: Among adults, appendicitis occurs at a rate of 1 to 2 per 1,000 individuals. Approximately 250,000 cases of appendicitis are treated surgically in the US each year (Incesu). Appendicitis occurs with a lower incidence internationally as compared to the US, as it appears to be more prevalent in affluent countries with low fiber diets.

History: The classic initial symptom of appendicitis is cramping or colicky pain around the navel (periumbilical) and loss of appetite (anorexia). As the symptoms from the appendix move downward into the right lower abdominal area (right lower quadrant), the pain becomes localized above the appendix at what is known as McBurney's Point. Fever develops within several hours. Other symptoms may include nausea, vomiting, constipation, rectal tenderness, chills, and shaking. Moving, walking, or coughing may aggravate the pain. Individuals with appendicitis generally report being in good health before the onset of the condition.

Physical exam: The most specific physical findings include rebound tenderness, pain on percussion of the abdomen, rigidity, and guarding. Manipulation of the abdomen (palpation) reveals extreme tenderness at McBurney's point. The individual frequently tightens (guards) the stomach muscles of the abdomen in response to palpation of this region. When the abdomen is depressed on the left side and held momentarily before being quickly released, the individual may experience a momentary increase in pain (rebound). This suggests inflammation has spread into the membrane lining the abdominopelvic walls (peritoneum). If the individual is pregnant, the enlarging fetus may alter the location of the appendix so the tenderness may be higher in the abdomen.

If the appendix has ruptured, the pain may disappear for a short period during which the individual feels better. However, within a short period, infection of the peritoneum (peritonitis) sets in. The pain then returns as the individual becomes progressively more ill. The entire abdomen becomes extremely tender and tight. A mild fever (<100° F [37.8° C]) may initially be present and increases if the appendix ruptures. In women, a rectal exam or a pelvic exam may help distinguish appendicitis from other conditions that produce abdominal pain.

Tests: Laboratory tests may include a complete blood count (CBC) that reveals an increase in white blood cell (WBC) count if an infection is present. A urinalysis helps identify any urological causes for the reported symptoms. Diagnostic tests may include high frequency sound waves (abdominal ultrasound) and x-rays taken following injection of a radiopaque dye (intravenous pyelogram). Abdominal x-rays may not always identify appendicitis. CT scan may also be helpful. For a definitive diagnosis, the abdomen may be examined with a fiber-optic microscope (laparoscopy) or visualized during an exploratory laparotomy. A pregnancy test is needed in sexually mature women to check for an abnormal (ectopic) pregnancy.