Diarrhea, acute

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Chapter 13 DIARRHEA, ACUTE

Theodore X. O’Connell

General Discussion

The term diarrhea refers to an increase in the frequency, fluidity, or volume of bowel movements relative to the usual habit of an individual. The World Health Organization (WHO) defines diarrhea as the passage of three or more loose or watery stools per day. An acute diarrheal illness typically is defined as a duration of 5 days or less. Children younger than 5 years old in developing countries have three to nine diarrheal illnesses per year, whereas in North America, young children have on average two diarrheal episodes per year.

Acute viral gastroenteritis is the most common cause of acute gastroenteritis in developed countries. Of the viral agents, rotavirus is the most common. Other common causes of diarrhea are bacterial infections, systemic nongastrointestinal infection, and antibiotics. Potentially life-threatening causes of diarrhea include hemolytic uremic syndrome (HUS), intussusception, pseudomembranous colitis, toxic megacolon, and appendicitis.

In contrast to the largely viral causation of gastroenteritis in the United States, diarrhea acquired in developing countries is more frequently bacterial in origin. Escherichia coli (E. coli), the most frequently isolated pathogen, may cause diarrhea of varying types and severity. Enterotoxigenic E. coli usually produces a mild, self-limited illness without significant fever or systemic toxicity, although it may be severe in newborns and infants. Enteroinvasive strains of E. coli cause a more significant illness characterized by fever, systemic symptoms, blood and mucus in the stool, and leukocytosis. Other invasive pathogens include Campylobacter, Shigella, and nontyphoid Salmonella. Aeromonas and noncholera Vibrio spp. are encountered less frequently.

Dehydration is the main complication of acute diarrhea. HUS is characterized by microangiopathic hemolytic anemia, thrombocytopenia, and renal failure. HUS is strongly associated with Shiga toxin–producing E. coli, although other strains and bacteria have been implicated.

Suggested Work-up

The extent of evaluation of stool specimens from a specific patient should be determined by the patient’s symptoms, time to onset of disease, age of the patient, travel history, food consumed, immunologic status, and prior history of antibiotic use. In most children with watery diarrhea and no associated symptoms such as fever, abdominal pain, blood or mucus in the stools and no history of diarrheal outbreak or toxin exposure, laboratory investigation is not required.

Stool leukocyte examination	Useful in patients with moderate to severe diarrhea with any associated symptoms such as fever, abdominal pain, blood or mucus in the stools, history of diarrheal outbreak, or toxin exposure
Stool culture	If the patient is febrile and has bloody diarrhea or if the stool leukocytes are positive
Urine culture	Should be considered in febrile children under 1 year of age
Serum electrolytes	If the patient is ill-appearing or appears significantly dehydrated
Stool for Clostridium difficile toxin	If the patient has bloody diarrhea and has been on antibiotics in the preceding 3 to 6 months
Stool for ova and parasites	If the patient has traveled to an endemic area

Additional Work-up

Complete blood count (CBC), chemistry panel, C-reactive protein, serum lactate dehydrogenase, urinalysis, and stool culture	If hemolytic uremic syndrome is suspected
Abdominal ultrasound	May be used if intussusception is suspected
Air contrast barium enema	If intussusception is suspected. May be therapeutic in such cases
Abdominal computed tomography (CT) scan	If an intra abdominal process such as appendicitis is suspected
Colonoscopy	May be indicated to establish the diagnosis of pseudomembranous colitis
Mucosal biopsy specimens for cytomegalovirus identification and culture	May be indicated in immunocompromised children

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2. Ramaswamy K., Jacobson K. Infectious diarrhea in children. Gastroenterol Clin. 2001;30:611–624.

3. Razzaq S. Hemolytic uremic syndrome: an emerging health risk. Am Fam Physician. 2006;74:991–996.

4. Yates J. Traveler’s diarrhea. Am Fam Physician. 2005;71:2095–2100.

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