Etiology and Pathophysiology

Common viral etiologies of acute infectious diarrhea in immunocompetent children include rotavirus, enteric adenoviruses, noroviruses, and astroviruses. Common bacterial pathogens include Salmonella spp., Escherichia coli, Shigella spp., and Campylobacter jejuni (Figure 96-2). Clostridium difficile is the most common cause of antibiotic-associated diarrhea, although its role in infants younger than 1 year of age is unclear. Additional causes are discussed in Table 96-1 with further discussion of treatment. These pathogens cause diarrhea by a variety of pathogenic means: (1) osmotic or malabsorptive, (3) inflammatory, and (3) toxigenic. In immunocompromised hosts, cytomegalovirus and herpes simplex virus should also be considered as causes of infectious diarrhea.

Figure 96-2 Bacillary dysentery.

Table 96-1 Common Infectious Causes of Gastroenteritis

Clinical Presentation

Patients with gastroenteritis often present with symptoms that include emesis, diarrhea, and abdominal pain, which may be associated with fever. Clinical examination findings are usually nonspecific and do not point toward the etiologic organism.

Electrolyte losses and dehydration account for the high morbidity of acute gastroenteritis. In a systematic meta-analysis conducted by Steiner et al., useful individual clinical signs to predict 5% dehydration in children are an abnormal capillary refill time, abnormal skin turgor, and abnormal respiratory pattern for clinical signs of dehydration. Other studies have found that a combination of clinical signs and symptoms is more reliable in the demonstration of at least 5% dehydration: capillary refill time longer than 2 seconds, absent tears, dry mucous membranes, and ill general appearance.

Certain infectious agents are associated with extraintestinal manifestations. Shigella spp. organisms produce a toxin that has been associated with seizure. Yersinia enterocolitica infection has been associated with reactive arthritis. Additional extraintestinal manifestations can be seen in Table 96-1.

Differential Diagnosis

A broad differential diagnosis must be entertained with acute gastroenteritis. Diarrhea can be the presenting symptom of other infections, anatomic, or malabsorptive issues such as bowel obstruction or inflammatory bowel disease. In addition, vomiting may indicate other infections such as meningitis, lower lobe pneumonia, sepsis, or urinary tract infection, as well as metabolic disorders, toxin ingestion, heart failure, and trauma.

Evaluation and Management

The laboratory evaluation of children with gastroenteritis is often guided by history and clinical presentation, particularly the degree of dehydration. Assessment and treatment of dehydration is at the forefront of management of gastroenteritis in children. Serum electrolyte testing helps in the management of patients who appear severely dehydrated and in the detection of hyponatremic or hypernatremic dehydration. Hemoccult testing of stool can aid in identifying pathogens that cause bloody diarrhea. Stool culture should be performed in patients in whom a bacterial etiology is suspected, especially in cases lasting longer than 3 days and with bloody diarrhea. Identifying diarrhea-associated E. coli can be difficult because most clinical laboratories cannot differentiate diarrhea-associated E. coli strains from normal intestinal flora. Bacterial toxin testing is used to identify A and B toxins from C. difficile, as well as Shiga-type toxins. Viral antigen detection or molecular polymerase chain reaction–based tests can be used to identify rotavirus, adenovirus, and caliciviruses (norovirus).

Treatment of patients with gastroenteritis includes supportive care and fluid management. In some cases of bacterial gastroenteritis, antimicrobial therapy may be helpful, although it is not routinely recommended.

A brief discussion of rehydration is provided here, but more detailed discussions can be found in the Suggested Readings section at the end of the chapter. Current recommendations from the American Academy of Pediatrics encourage use of ORT in managing acute gastroenteritis in children. Oral rehydration occurs in two phases of treatment: a rehydration phase in which water and electrolytes are given in the form of an oral rehydration solution (ORS) for existing losses and a maintenance phase. ORS introduces glucose as well as sodium at the same time to allow for coupled transport. The World Health Organization’s components for rehydration solution consist of at least a complex carbohydrate or 2% glucose and 50 to 90 m Eq/L of sodium. Early refeeding is now encouraged after previous losses are corrected. Antimicrobial therapies for certain bacterial etiologies are discussed in Table 96-1.

Future Directions

New research into prevention and treatment continues. The use of vaccination for rotavirus may reduce the morbidity and mortality of gastroenteritis in young children. Use of probiotics is an ongoing controversial issue with future research still necessary to see if it aids recovery from gastroenteritis.