• Short in duration; usually lasts less than 2 weeks
• In infants, stool volume in excess of 10 g/kg/d is considered diarrhea.
• In children older than 3 years of age, the stool volume is equivalent to adult levels and greater than 200 g/d of stool volume is considered diarrhea.

• Most common cause for acute diarrhea is aviral infection:
  • Rotavirus
  • Norwalk
  • Enteric adenovirus
  • Calicivirus
• Bacterial infections:
  • Salmonella
  • Escherichia coli
  • Shigella
  • Campylobacter
  • Clostridium
  • Yersinia
  • Cholera
• Parasitic infections also common
• Variety of less common causes:
  • Antibiotic-associated diarrhea
  • Toxin exposure (food poisoning)
  • Overfeeding in newborns
  • Hirschsprung colitis
  • Hyperthyroidism

• In acute diarrhea, impairment of the normal absorptive and secretory balance of the different regions of the gut resulting in diarrhea.
• Viral pathogens generally produce injury to the proximal small bowel and bacterial pathogens usually cause colonic injury.
• Bacterial pathogens cause injury through:
  • Invasion of the mucosa, causing cell death as they replicate (invasive)
  • Cytotoxicity (direct cell death)
  • Toxigenicity (producing toxins that alter water balance)
  • Adherence to the mucosal surface, causing disruption of normal cell function

• Diarrhea remains one of the most significant global medical problems.
• In developed countries such as the United States, the overall problem is less severe than in other developing countries because improved sanitation systems reduce transmission.
• There are approximately 20 to 40 million episodes of diarrhea in the United States in children less than 5 years of age annually. An estimated 200,000 need hospitalization, and 200 to 400 die each year.
• Worldwide, an estimated 4 million children die from diarrheal disease annually.
• Most transmission is via the fecal-oral route.
• Other organisms are transmitted via direct person-to-person contact (day care centers). Some are transmitted via infected food or water.
• Most common viral pathogens occur in the winter months and the common bacterial pathogens in the summer.

• The most common complication is dehydration. If severe enough, this may be associated with electrolyte abnormalities and acidosis.
• Some bacterial pathogens may also lead to bacteremia and may even cause seizures by either an infectious or a toxin-mediated process.
• Certain pathogens, namely Escherichia coli 0157 subtype H7 can cause the hemolytic uremic syndrome.
• In cases in which the small-bowel mucosa has been significantly injured, a protein-losing enteropathy can occur.
• Meningitis and osteomyelitis are less frequent complications.

• The major cause of acute diarrhea is viral gastroenteritis.
  • Rotavirus is most common between the ages of 6 and 24 months. It is the most common cause of diarrheal illness in the pediatric population.
• There is an increase in incidence during the winter months, and symptoms last between 2 and 8 days.
• Most children have developed antibodies to the virus by the age of 2; this explains the decrease in incidence seen in older patients.
  • Norwalk virus seems to affect older children and adults and has no seasonal variation. Duration of symptoms is between 1 and 2 days.
  • Enteric adenovirus is predominantly seen in children less than 2 years of age and occurs mainly in the summer months. Symptoms may last up to 14 days.
  • Calicivirus accounts for about 3% of diarrheal disease that requires hospitalization. It mainly affects children between 3 months and 6 years. Symptoms last between 2 and 8 days.
  • Cytomegalovirus has been associated with diarrhea and colitis, but is pathogenic predominantly in the immunocompromised host.

    Bacterial pathogens include:

  • Salmonella is the most common cause of bacterial diarrhea in children in the United States. Its highest incidence is in infancy.
  • Shigella accounts for approximately 20% of diarrhea due to a bacterial pathogen. It occurs mainly between the ages of 6 months and 10 years. It is the most common cause of bacterial outbreaks in the day care center setting. A large number of complications can be seen with Shigella infections, such as seizures, bacteremia, meningitis, and osteomyelitis.
  • Campylobacter is a common pathogen, but at times is underdiagnosed because it requires specific media and conditions to grow. It appears to have two peaks of infection: children under 1 year of age and young adults.
  • Yersinia is a fairly common organism worldwide and causes symptoms most frequently in young children.
  • Cholera isa major pathogen in developing nations.
  • Escherichia coli is a species with a diverse group of organisms in which some are non-pathogenic and part of the normal intestinal flora. The four pathogenic types that cause diarrhea include:
    • Enteropathogenic E. coli
    • Enterotoxigenic E. coli
    • Enteroinvasive E. coli
    • Enterohemorrhagic E. coli
  • Clostridium difficile has been noted primarily but not exclusively in patients in whom there has been an alteration in their normal intestinal flora by the use of antibiotics.
  • Aeromonas and Plesiomonas are less common bacterial pathogens. The latter has been diagnosed in immunocompromised hosts.
  • Giardiasis is the most common protozoal cause of acute diarrhea.
• Several other causes of acute diarrhea must be considered along with the infectious causes. These less common etiologies are listed.
  • Antibiotics may cause diarrhea by altering the intestinal flora. In many cases of antibiotic use, diarrhea can still occur without the presence of C. difficile.
  • Overfeeding, especially in small newborns, may lead to diarrhea.
  • Hirschprung disease/colitis can lead to acute bloody, mucous diarrhea when the mucosa of the colon becomes inflamed. These patients tend to appear ill.
  • Toxic ingestions such as with over-the-counter laxatives may be considered in the appropriate clinical setting.
  • Hyperthyroidism can also cause diarrhea.

Question: Exposure history?
Significance: Needs to be obtained, focusing on possible exposures to other affected individuals, especially children in day care centers.

Question: Diet history?
Significance: Focusing on water source, poultry intake, milk intake, and fish sources needs to be performed.

Question: Antibiotic use?
Significance: Presence of C. difficile

Question: Travel history?
Significance: Important for endemic causes and seasonal variations.

Question: Stool pattern and symptoms?
Significance: May be beneficial in helping to focus on a specific etiology.

• Signs consistent with dehydration

Finding: Stools with occult or gross blood
Significance: Shigella, Salmonella, E. coli, Campylobacter

Finding: Abdominal tenderness
Significance: E. coli

Finding: Extraintestinal findings such as seizures, mental status changes
Significance: Shigella

Finding: Bone and joint pain
Significance: R/O osteomyelitis, salmonella

Finding: Rashes
Significance: Typhoid

Test: Stool evaluation
Significance: Stool should be evaluated for:

• Occult blood and WBC
• Ova and parasites
• Rotavirus (Rotazyme test)
• C. difficile (toxin A and B)
• Shigella
• E. coli

Test: X-ray study
Significance: In more severe cases or in the appropriate clinical setting abdominal x-ray studies may be helpful.

Test: Endoscopy and/or colonoscopy
Significance: In the most complex and difficult cases more invasive procedures may be helpful in making the diagnosis.

Test: Blood tests
Significance: CBC, blood culture, and electrolytes may be helpful in management but are not diagnostic.

• Most cases of acute, infectious diarrhea seen in pediatric offices in developed countries are mild and self-limited and can be managed on an outpatient basis with close follow-up.
• The goal of therapy is to treat the underlying cause of the diarrhea if identifiable and treatable and to provide adequate hydration in order to maintain euvolemia, electrolyte balance, and acid-base balance.
• The hydration status in dehydrated patients can be altered by oral or intravenous replacement therapy based on the clinical situation. Support with total parenteral nutrition (TPN) or elemental tube feeds may be necessary in patients with severe episodes of diarrhea.
• Antimicrobial agents do not greatly affect the overall course of gastroenteritis in most cases. Specific antibiotic therapies do exist for certain organisms and do help lessen the severity of the episode as well as decrease the fecal shedding and, therefore, the spread of the organism. In certain clinical settings, such as infection with Salmonella, antibiotics are not indicated.
• The best possible therapy for acute, infectious diarrhea is prevention. The best way to prevent transmission is to interrupt the fecal-oral pathway. For the most part, this requires an increased awareness of sanitation and hygiene as well as the proper handling and cooking of meat, fish, and poultry products.

• In cases in which the dehydration is below 5%, oral replacement therapy is used. In cases in which the dehydration is severe (<10%), intravenous fluids should be used. Between 5% to 10% dehydration, each individual clinical situation should be considered and at times a combination of oral and intravenous therapy have the best outcome.
• Other limitations to oral rehydration would include intractable vomiting, high stool output, and carbohydrate malabsorption.
• Reassessment of a patient with dehydration should be very vigilant and continuous, and adjustments should be made every 2 to 4 hours as needed.
• In addition to replacement of the deficit, ongoing losses should initially be replaced on a 1:1 basis.

• At this point, advancement in diet should begin and should proceed as tolerated. Special care should be taken with patients who may initially be lactose-intolerant. Soon after resolution of diarrhea an appropriate lactose-free formula may be used in the initial refeeding phase.
• Ongoing fluid losses should continue to be replaced until the diarrhea has resolved.

• The majority of episodes of acute diarrhea are mild and self-limited and with close supervision and education of hydration status, patients can do well.
• In more severe cases, close monitoring and reassessment of hydration status is required.
• Once symptoms have improved and the diarrhea resolved, there is no routine follow-up needed.

• Reassess therapy frequently and adjust therapy based on clinical setting.
• Use appropriate electrolyte solutions during rehydration and maintenance therapy.

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