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DEFINITIONS AND EPIDEMIOLOGY

Gastroenteritis is either the acute onset of vomiting or the acute onset of diarrhea with or without vomiting. Vomiting is the acute onset of forceful expulsion of gastric secretions through the oral cavity and should be differentiated from posttussive emesis and gastroesophageal reflux. Diarrhea is defined as loose or watery stools that exceed the child’s usual number of daily bowel movements by two or more.1 Dysentery is the presence of bloody diarrhea and fever.

Common causes of gastroenteritis are listed in Table 42-1. Viruses cause most cases of gastroenteritis in industrialized countries. In contrast, bacteria are responsible for most cases in developing countries. Another bacterial cause of vomiting and diarrhea is the contamination of food with preformed toxins. Whereas this is a distinct clinical entity, the symptoms and management are similar to those for gastroenteritis due to other causes.

TABLE 42-1Causes of Gastroenteritis

Approximately 180 million cases of gastroenteritis occur annually in the United States.2,3 This disease burden in children results in over 100,000 hospitalizations annually.4 Following the development of the rotavirus vaccines, the most common cause of gastroenteritis in children is now norovirus, with an incidence of 70 per 1000 person-years.

Internationally, there are over 1 billion cases of gastroenteritis and between 1 and 3 million deaths attributed to dehydration annually.5 Most deaths occur in regions with poor access to healthcare. Mortality due to dehydration has decreased by 80% from the 1980s, when there were approximately 5 million deaths per year.6

PATHOGENESIS

Microbial agents of gastroenteritis are transmitted primarily via the fecal–oral route; some viruses may also be transmitted by the airborne route. Once ingested, viral particles enter the enterocytes of the small intestinal villi and induce villus shortening and cell destruction. Cell destruction generates cytokines and chemokines, causing inflammation, which may result in impairment of nutrient absorption or secretion of water and electrolytes. Some viral proteins also act directly as entertoxins. Recovery occurs when the villi regenerate and the villus epithelium matures.7

Bacteria have three mechanisms that induce illness: adhesion, toxin production, and mucosal invasion. Initially, bacteria adhere to the intestinal mucosa. This mucosal adherence may interfere with absorption or cause fluid secretion, both of which ultimately lead to diarrhea. Secreted enterotoxins cause diarrhea by at least two mechanisms: (1) blockage of sodium absorption, triggering cytotoxin-mediated inflammation and causing enterocyte apoptosis; and (2) bacterial invasion of mucosal surfaces, causing ulceration or abscess formation. It is this combination of ...

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