C. jejuni, and invasive E. coli. Patients infected with Shiga toxin-producing E. coli and E. histolytica generally have minimal fecal leukocytes.
A rapid diagnostic test for rotavirus in stool should be performed, especially during the winter. Bacterial stool culturesare recommended for patients with fever, profuse diarrhea, anddehydration or if HUS or pseudomembranous colitis is suspected. If the stool test result is negative for blood and leukocytes,and there is no history to suggest contaminated food ingestion, aviral etiology is most likely. Stool evaluation for parasitic agentsshould be considered for acute dysenteric illness, especially inreturning travelers, and in protracted cases of diarrhea in whichno bacterial agent is identified. The diagnosis of E. histolytica is based on identification of the organism in the stool. Serologictests are useful for diagnosis of extraintestinal amebiasis, including amebic hepatic abscess. Giardiasis can be diagnosed by identifying trophozoites or cysts in stool but require three specimens.More specific and sensitive fecal immunoassays are the diagnostic tests of choice.
Positive blood cultures are uncommon with bacterial enteritis except for S. typhi (typhoid fever), nontyphoidal Salmonella, and E. coli enteritis in very young infants. Intyphoid fever, blood cultures are positive early in the disease, whereas stool cultures become positive only after the secondary bacteremia.
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Abdominal Pain Vomiting Diarrhea Failure to Thrive
Diarrhea can be caused by infection, toxins, gastrointestinal allergy (including allergy to milk or soy proteins), malabsorption defects, inflammatory bowel disease, celiac disease, or any injury to enterocytes. Specific infections are differentiated from each other by the use of stool cultures and enzyme-linked immunosorbent assay or polymerase chain reaction tests, when necessary. Acute enteritis may mimic other acute diseases, such as intussusception and acute appendicitis, which are best identified by diagnostic imaging. Many noninfectious causes of diarrhea produce chronic diarrhea, with persistence for more than 14 days. Persistent or chronic diarrhea may require tests for malabsorption or invasive studies, including endoscopy and small bowel biopsy (see Chapter 129).
Common-source diarrhea usually is associated with ingestion of contaminated food. In the United States, the most common bacterial food-borne causes (in order of frequency) are nontyphoidal Salmonella, Campylobacter, Shigella, E. coli O157:H7, Yersinia, Listeria monocytogenes, and V. cholerae. The most common parasitic food-borne causes are Cryptosporidium parvum and Cyclospora cayetanensis.
Common-source diarrhea also includes ingestion of preformed enterotoxins produced by bacteria, such as S. aureus and Bacillus cereus, which multiply in contaminated foods, and nonbacterial toxins such as from fish, shellfish, and mushrooms. After a short incubation period, vomiting and cramps are prominent symptoms, and diarrhea may or may not be present. Heavy metals that leach into canned food or drinks causing gastric irritation and emetic syndromes may mimic symptoms of acute infectious enteritis.
Most infectious causes of diarrhea in children are self-limited. Management of viral and most bacterial causes of diarrhea is primarily supportive and consists of correcting dehydration and ongoing fluid and electrolyte deficits and managing secondary complications resulting from mucosal injury.