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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 fixed retrocecally in 16% of adults and is freely mobile in the remainder.

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The appendix in youth is characterized by a large concentration of lymphoid follicles that appear 2 weeks after birth and number about 200 or more at age 15. Thereafter, progressive atrophy of lymphoid tissue proceeds concomitantly with fibrosis of the wall and partial or total obliteration of the lumen.

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If the appendix has a physiologic function, it is probably related to the presence of lymphoid follicles. Reports of a statistical relationship between appendectomy and subsequent carcinoma of the colon and other neoplasms in humans are not supported by controlled studies.

Schumpelick V et al: Appendix and cecum. Embryology, anatomy, and surgical applications. Surg Clin North Am 2000;80:295.  [PubMed: 10685154]

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Essentials of Diagnosis

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  • Abdominal pain.
  • Anorexia, nausea and vomiting.
  • Localized right lower quadrant abdominal tenderness.
  • Low-grade fever.
  • Leukocytosis.

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General Considerations

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Approximately 7% of people in Western countries have appendicitis at some time during their lives, and about 200,000 appendectomies for acute appendicitis are performed annually in the United States. The incidence has been steadily dropping over the past 25 years, however, while the incidence in developing countries—which in the past has been quite low—has been rising in proportion to economic gains and changes in lifestyle.

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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, though that theory is doubted by many experts. Evidence of temporal and geographic clustering of cases has suggested a primary infectious etiology. A fecalith or calculus is found in only 10% of acutely inflamed appendices.

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As appendicitis progresses, the blood supply is impaired by bacterial infection in the wall and distention of the lumen by pus; gangrene and perforation occur at about 24 hours, though the timing is highly variable. Gangrene implies microscopic perforation and bacterial peritonitis (which may be localized by adhesions from nearby viscera).

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Clinical Findings

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Acute appendicitis has protean manifestations. It 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.

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Symptoms and Signs

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Typically, the illness begins with vague midabdominal discomfort followed by nausea, anorexia, and indigestion. The pain is persistent and continuous but not ...

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