Diarrhea is the passage of loose or watery stools at least three times in a 24 hour period. Diarrheal illness is the second leading cause of child mortality; among children younger than five years, it causes 1.5 to 2 million deaths annually [1,2]. In developing countries, infants experience a median of six episodes annually; children experience a median of three episodes annually .
Diarrheal illness may consist of acute watery diarrhea, invasive (bloody) diarrhea, or chronic diarrhea (persistent ≥14 days). This classification facilitates the approach to management of childhood diarrhea. Issues related to the etiology, clinical assessment, treatment, and prevention of acute watery diarrhea and invasive diarrhea in children in developing countries are reviewed here. Issues related to chronic diarrhea in children are discussed separately. (See "Persistent diarrhea in children in developing countries".)
Most cases of acute diarrhea in developing countries are caused by infectious gastroenteritis. Less commonly, acute diarrhea can be a symptom of a systemic infection or an intra-abdominal surgical emergency.
Infectious gastroenteritis — The most common microbiological causes of infectious gastroenteritis differ by age group, geographical region, and type of diarrhea. In a large study of children five years or younger at seven sites in Asia and Africa, stool samples from 9439 children with moderate to severe diarrhea and from 13129 controls were tested for a panel of microorganisms . Rotavirus, Cryptosporidium, Shigella, and enterotoxigenic Escherichia coli (ETEC) were important pathogens at all study sites, and most attributable cases of diarrhea were due to these organisms. Rotavirus was the most common pathogen among children under two years old, whereas Shigella was the most frequently isolated pathogen in children aged two to five. Cryptosporidium was the second most common pathogen among infants under one year old, but was infrequently detected in children older than two years. Aeromonas was a frequent pathogen in Pakistan and Bangladesh, and Campylobacter jejuni in Pakistan, Bangladesh, and India. Vibrio cholera was an important cause of diarrhea at those three Asian sites as well as Mozambique.
Acute diarrhea can also be classified as watery versus invasive, bloody diarrhea, and the microbiological etiologies differ by type, as discussed below (table 1) .