In infants, the appendix is a conical diverticulum at the apex of the cecum, but with differential growth and distention of the cecum, the appendix ultimately arises on the left and dorsally approximately 2.5 cm below the ileocecal valve. The taeniae of the colon converge at the base of the appendix, an arrangement that helps in locating this structure at operation. The appendix is freely mobile in the majority and is fixed retrocecally in 16% of adults.
The appendix in children is characterized by a large concentration of lymphoid follicles that appear 2 weeks after birth and number about 200 or more at age 15 years. Thereafter, progressive atrophy of lymphoid tissue proceeds with fibrosis of the wall and partial or total obliteration of the lumen. If the appendix has a physiologic function, it is probably related to the presence of lymphoid follicles.
Approximately 7% of people in Western countries have appendicitis at some time during their lives. With more than 250,000 appendectomies for acute appendicitis performed annually in the United States, it is the most common surgical emergency encountered by the general surgeon and accounts for about 1% of all surgical operations.
Obstruction of the proximal lumen by fibrous bands, lymphoid hyperplasia, fecaliths, calculi, or parasites has long been considered to be the major cause of acute appendicitis. A fecalith or calculus is found in only 10% of acutely inflamed appendices. Though evidence of temporal and geographic clustering of cases has suggested a primary infectious etiology this remains to be proven.
As appendicitis progresses, the blood supply is impaired by bacterial infection in the wall and distention of the lumen; gangrene and perforation occur at about 24 hours, though the timing is highly variable. Gangrene implies microscopic perforation, bacterial contamination of the peritoneum, and peritonitis. This process may be effectively localized by adhesions from nearby viscera.
Acute appendicitis may simulate almost any other acute abdominal illness, and in turn may be mimicked by a variety of conditions. Progression of symptoms and signs is the rule—in contrast to the fluctuating course of some other diseases.
Typically, the illness begins with vague midabdominal or periumbilical discomfort followed by nausea, anorexia, and indigestion. The pain is continuous but not severe, with occasional mild cramping. The patient may feel constipated or may vomit. Importantly, within several hours of the onset of symptoms the pain shifts to the right-lower quadrant, becoming localized and causing discomfort on moving, walking, or coughing.
Physical examination shows localized tenderness to palpation and perhaps slight muscular guarding. Rebound or percussion tenderness (the latter provides the same information more humanely) may be elicited in the right-lower quadrant. Rectal and pelvic examinations are likely ...