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Gastroenteritis is commonly defined as either the acute onset of vomiting or the acute onset of diarrhea with or without vomiting. Vomiting is defined as 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. When bloody diarrhea and fever are present, the illness is referred to as dysentery. The majority of gastroenteritis in the developed countries occurs due to a viral etiology, predominantly rotavirus, whereas bacteria are responsible for the majority of cases in less developed nations. Relatively common causes of gastroenteritis are listed in Table 39–1.
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In the United States, children develop between one and three episodes of gastroenteritis per year. This disease burden results in 3.5 million physician visits, 200,000 hospitalizations, 900,000 hospital days, and approximately 300 deaths annually.1 Children will invariably have had an episode of rotavirus gastroenteritis by the age of 5 years.2 Furthermore, rotavirus has been found to cause a more serious illness than other pathogens; children with rotavirus gastroenteritis are five times more likely to become dehydrated than children with other causes of acute gastroenteritis.3
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Internationally, there are over 1 billion cases of gastroenteritis and 1 to 3 million deaths attributed to dehydration annually.4 Most deaths occur in regions that have poor access to health care. Although the number of deaths due to dehydration seems high, this number represents an 80% decrease from the 1980s when there were approximately 5 million deaths per year.5
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The intestinal tract is constantly secreting and absorbing fluids. In fact, it secretes and absorbs approximately 6 L of fluid in a day from saliva, gastric secretions, pancreatic secretions, and intestinal secretions. When the reabsorption process is disrupted, children can sustain large volume losses and become dehydrated.6
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Gastroenteritis, whether viral, bacterial, or parasitic in origin, is 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, which cause inflammation. The inflammation impairs absorption of nutrients, particularly carbohydrates, and potentiates the diarrhea. Villus cells are temporarily replaced with immature crypt-like cells that cause the intestine to secrete water and electrolytes. Some viral proteins also act as entertoxins directly. Recovery occurs when the villi regenerate and the villus epithelium matures.7
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Bacteria, on the other hand, utilize three ...