If the tubelike appendix becomes plugged by a hard bit of fecal matter or by intestinal worms, or becomes inflamed from other causes, normal drainage cannot take place. Because the appendix is chiefly lymphatic tissue, an infection that produces enlarged lymph nodes elsewhere in the body also can increase the glandular tissue in the appendix and obstruct its lumen. Narrowing of the lumen makes the pouchlike organ more susceptible to bacterial infection. Escherichia coli and other types of bacteria multiply and cause inflammation and infection that spread to the peritoneal cavity unless the body's defenses are able to overcome the infection or the appendix is removed before it ruptures. The classic symptoms of appendicitis are pain, nausea, vomiting, and low-grade fever in adults.
Children tend to have higher fevers.
The pain typically begins in the umbilical region and eventually localizes in the right lower quadrant of the abdomen over the site of the appendix. Rebound pain occurs when the abdomen is deeply palpated and the hand is quickly removed from the abdomen. The patient also can feel pain in the area of the appendix when either a rectal or pelvic examination is done. Other data that may support a diagnosis of appendicitis are obtained through a blood cell count. Mild leukocytosis of 14,000 to 16,000 per mm 3 is common.