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BACKGROUND

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About 7% of all people will develop appendicitis over the course of their lifetime.1 Each year in the United States, about 60,000 to 80,000 children develop appendicitis. It is particularly common in the preteen and teen years, with the average age of onset being about 10 years. Before puberty, boys and girls are affected equally; after puberty, there is a slight male predominance.

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PATHOPHYSIOLOGY

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The appendix, whose function remains unknown, arises from the cecum. Roughly 5% to 15% of people have retrocecal appendixes. In children, the appendix is relatively longer and thinner than in adults, which makes it more susceptible to perforation early in the course of the disease. The greater omentum remains thin, short, and fragile until about 10 years of age. It is therefore less likely to wall off a perforated appendix in a younger child, making generalized peritonitis more common in children than in adults.2

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The pathogenesis of appendicitis begins with obstruction of the appendiceal lumen. The most common cause of obstruction is enlargement of the lymphoid tissue (Peyer patches) in the wall of the appendix. The lymphoid follicles enlarge probably in response to ingested microorganisms, most likely viruses associated with upper respiratory infections. Fecal material, undigested food, other foreign material, or pinworms may also lead to obstruction. Regardless of the initial trigger, the resultant obstruction causes dilation of the lumen of the appendix and thickening of its wall. Bacterial overgrowth results within the structure, with subsequent bacterial invasion of the appendiceal wall, inflammation, and ischemia. If unchecked, gangrene and eventual appendiceal perforation will occur. As the transmural appendiceal inflammation progresses, so does the local peritoneal inflammation. With perforation, the peritonitis can become widespread.

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The responsible bacteria are usual fecal flora, most commonly Escherichia coli, Peptostreptococcus, Bacteroides fragilis, and Pseudomonas species, and the process is usually polymicrobial.

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CLINICAL PRESENTATION

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The classic presentation of appendicitis is not difficult to recognize and occurs in approximately two thirds of cases. Many preschool-age children, however, present with atypical and challenging clinical pictures.

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Typically, a previously healthy child awakes with vague periumbilical pain that is uncomfortable but not debilitating. Shortly after the onset of pain, infrequent nonbilious emesis often develops. Over the next few hours, the poorly localized pain gradually increases in intensity before moving to the right lower quadrant. There is associated anorexia and low-grade fever. A child with appendicitis prefers to remain still, so the jarring and shaking movements during a car ride are painful. Diarrhea, if it occurs, is infrequent and consists of small stools caused by irritation of the sigmoid colon by the inflamed appendix (as opposed to large stools typical of gastroenteritis). Likewise, bladder irritation may produce dysuria or urgency.

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In atypical cases, the pain pattern may be quite different. Young children in particular may not recognize or ...

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