Acute gastroenteritis (AGE) is an extremely common cause of morbidity and mortality in infants and children living in the United States and accounts for >1.5 million outpatient visits, 200,000 hospitalizations, and approximately 300 deaths/year. It is usually of viral etiology, most commonly rotavirus. Worldwide, diarrheal diseases result in 1.5 to 2.5 million deaths per year in children younger than 5 years. Rates of morbidity and mortality remain extremely high, but mortality has been dramatically decreased with the use of worldwide campaigns that promote the treatment of acute diarrhea with oral rehydration therapy (ORT). Although originally used in developing countries, the success of oral rehydration solutions (ORS) resulted in the first World Health Organization (WHO) guidelines for ORT. ORT is now the standard of care for acute gastroenteritis (clinically efficacious and cost-effective).

In AGE, vomiting usually precedes diarrhea by 12 to 24 hours. The patient may or may not have fever. Dehydration may exist, but its clinical symptoms may not be easy to detect depending on the degree of dehydration. Those at increased risk for dehydration include those who are younger than 12 months, have frequent stools (>8/day), have frequent episodes of emesis (>2/day), and who that are undernourished. Acute diarrhea is defined as ≥3 loose or watery stools per day. The volume can range from 5 mL per kilogram of body weight/day to ≥200 mL per kilogram of body weight/day. Viral diarrhea affects the small bowel and results in large amounts of watery diarrhea and midabdominal cramping. On the other hand, bacterial diarrhea results in smaller volumes of bloody, mucoid diarrhea, and lower abdominal pain. A bacterial etiology should especially be considered in children with
a history of travel, who have epidemic day care exposure, and who have high fevers, bloody stools, or severe cramping. Emesis may be the initial presentation of a variety of illnesses including appendicitis, urinary tract infection, volvulus, inborn errors of metabolism, diabetic ketoacidosis, and hemolytic uremic syndrome. Obtaining a thorough and accurate history is for the workup and diagnosis of AGE and should not be made prematurely.

Treatment of AGE with ORT often begins at home and begins with seven specific principles of therapy (Table 151.1). It is important to stress to parents that they have a supply of ORS in the home at all times for this reason. Early administration of ORS leads to fewer office and emergency department visits, and fewer hospitalizations. Parents should be encouraged to start this therapy as soon as diarrhea begins, and they should be trained to recognize signs of illness or treatment failure. Indications for medical intervention or evaluation include: