eMedicine Specialties > Pediatrics: General Medicine > Gastroenterology

Diarrhea

Author: Stefano Guandalini, MD, Director, University of Chicago Celiac Disease Program, Section Chief of Gastroenterology, Hepatology and Nutrition; Professor, Department of Pediatrics, University of Chicago Comer Children's Hospital
Coauthor(s): Richard E Frye, MD, PhD, Assistant Professor, Departments of Pediatrics and Neurology, University of Texas Health Science Center at Houston; M Akram Tamer, MD, Program Director, Professor, Department of Pediatrics, University of Miami
Contributor Information and Disclosures

Updated: Jan 5, 2009

Introduction

Background

Acute diarrhea is defined as the abrupt onset of abnormally high fluid content in the stool (more than the normal value of approximately 10 mL/kg/d). This situation typically implies an increased frequency of bowel movements, which can range from 4-5 to more than 20 times per day. The augmented water content in the stools is due to an imbalance in the physiology of the small and large intestinal processes involved in the absorption of ions, organic substrates, and thus water. A common disorder in its acute form, diarrhea has many causes and may be mild to severe. Childhood acute diarrhea is usually caused by infection; however, numerous disorders may cause this condition, including a malabsorption syndrome and various enteropathies. Acute-onset diarrhea is usually self-limited; however, an acute infection can have a protracted course. By far, the most common complication of acute diarrhea is dehydration.

Although the term "acute gastroenteritis" is commonly used synonymously with "acute diarrhea," the former term is a misnomer. The term gastroenteritis implies inflammation of both the stomach and the small intestine, whereas, in reality, gastric involvement is rarely if ever seen in acute diarrhea (including diarrhea with an infectious origin); enteritis is also not consistently present. Examples of infectious acute diarrhea syndromes that do not cause enteritis include Vibrio cholerae– induced diarrhea and Shigella -induced diarrhea. Thus, the term acute diarrhea is preferable to acute gastroenteritis.

Diarrheal episodes are classically distinguished into acute and chronic (or persistent) based on their duration. Acute diarrhea is thus defined as an episode that has an acute onset and lasts no longer than 14 days; chronic or persistent diarrhea is defined as an episode that lasts longer than 14 days. The distinction, supported by the World Health Organization (WHO), has implications not only for classification and epidemiological studies but also from a practical standpoint because protracted diarrhea often has a different set of causes, poses different problems of management, and has a different prognosis.

Pathophysiology

Diarrhea is the reversal of the normal net absorptive status of water and electrolyte absorption to secretion. Such a derangement can be the result of either an osmotic force that acts in the lumen to drive water into the gut or the result of an active secre­tory state induced in the enterocytes. In the former case, diarrhea is osmolar in nature, as is observed after the ingestion of nonabsorbable sugars such as lactulose or lactose in lactose malabsorbers. Instead, in the typical active secretory state, enhanced anion secretion (mostly by the crypt cell compartment) is best exemplified by enterotoxin-­induced diarrhea.

In osmotic diarrhea, stool output is proportional to the intake of the unabsorbable substrate and is usually not massive; diarrheal stools promptly regress with discontinuation of the offending nutrient, and the stool ion gap is high, exceeding 100 mOsm/kg. In fact, the fecal osmolality in this circumstance is accounted for not only by the electrolytes but also by the unabsorbed nutrient(s) and their degradation products. The ion gap is obtained by subtracting the concentration of the elec­trolytes from total osmolality, according to the formula: ion gap = osmolality – [(Na + K) × 2].

In secretory diarrhea, the epithelial cells’ ion transport processes are turned into a state of active secretion. The most common cause of acute-onset secretory diarrhea is a bacterial infection of the gut. Several mechanisms may be at work. After colonization, enteric pathogens may adhere to or invade the epithelium; they may produce enterotoxins (exotoxins that elicit secretion by increasing an intracellular second messenger) or cytotoxins. They may also trigger release of cytokines attracting inflammatory cells, which, in turn, contribute to the acti­vated secretion by inducing the release of agents such as prostaglandins or platelet-activating factor. Features of secretory diarrhea include a high purg­ing rate, a lack of response to fasting, and a normal stool ion gap (ie, 100 mOsm/kg or less), indicating that nutrient absorption is intact. 

Frequency

United States

In the United States, one estimate assumes a cumulative incidence of 1 hospitalization for diarrhea per 23-27 children by age 5 years, with more than 50,000 hospitalizations in 2000. By these estimates, rotavirus is associated with 4-5% of all childhood hospitalizations, and 1 in 67 to 1 in 85 children are hospitalized due to rotavirus by age 5 years. Furthermore, acute diarrhea is responsible for 20% of physician referrals in children younger than 2 years and for 10% in children younger than 3 years.

International

In developing countries, an average of 3 episodes per child per year in children younger than 5 years is reported; however, some areas report 6-8 episodes per year per child. In these settings, malnutrition is an impor­tant additional risk factor for diarrhea, and recurrent episodes of diarrhea lead to growth faltering. Childhood mortality associated with diarrhea has constantly but slowly declined during the past 2 decades, mostly because of the widespread use of oral rehydration solutions; however, it still remains high.

Because the single most common cause of infectious diarrhea worldwide is rotavirus, and because a vaccine has been in use for over 2 years now, a reduction in the overall frequency of diarrheal episodes is hoped for in the near future.

Mortality/Morbidity

Mortality from acute diarrhea is overall globally declining but remains high. Most estimates have diarrhea as the second cause of childhood mortality, with 18% of the 10.6 million yearly deaths in children younger than age 5 years.

Despite a progressive reduction in global diarrheal disease mortality over the past 2 decades, diarrhea morbidity in published reports from 1990-2000 slightly increased worldwide compared with previ­ous reports.

Furthermore, in countries where the toll of diarrhea is highest, poverty also adds an enormous additional burden, and long-term conse­quences of the vicious cycle of enteric infections, diarrhea, and malnutrition are devastating.

Sex

Most cases of infectious diarrhea are not sex specific. Females have a higher incidence of Campylobacter species infections and hemolytic uremic syndrome (HUS).

Age

Viral diarrhea is most common in young children. Rotavirus and adenovirus are particularly prevalent in children younger than 2 years. Astrovirus and norovirus usually infect children younger than 5 years. Yersinia enterocolitis typically infects children younger than 1 year, and the Aeromonas organism is a significant cause of diarrhea in young children.

Very young children are particularly susceptible to secondary dehydration and secondary nutrient malabsorption. Age and nutritional status appear to be the most important host factors in determining the severity and the duration of diarrhea. In fact, the younger the child, the higher is the risk for severe, life-threatening dehydration as a result of the high body-water turnover and limited renal compensatory capacity of very young children. Whether younger age also means a risk of run­ning a prolonged course is an unsettled issue. In developing countries, persis­tent postenteritis diarrhea has a strong inverse correlation with age.

Clinical

History

• Acute diarrhea in developed countries is almost invariably a benign, self-limited condition, subsiding within a few days. The clinical presentation and course of illness depend on the etiology of the diarrhea and on the host. For example, rotavirus is more commonly associated with vomiting, fever, and a greater number of work days lost than nonrotavirus gastroenteritis.
• A prospective study conducted in the United States in 604 children aged 3-36 months in community settings found that the highest incidence of acute diarrhea was in January and August, with an overall incidence of 2.21 episodes per person-year.¹ Close to 90% of episodes were acute (ie, lasting <14 d, with a median duration of 2 d and a median of 6 stools per day).
• Diarrhea implies an increase in stool volume and diminished stool consistency.
  • In children younger than 2 years, diarrhea is defined as daily stools with a volume greater than 10 mL/kg.
  • In children older than 2 years, diarrhea is defined as daily stools with a weight greater than 200 g. In practice, this typically means loose-to-watery stools passed 4 or more times per day.
  • Individual stool patterns widely vary; for example, breastfed children may normally have 5-6 stools per day.
• Flatulence associated with foul-smelling stools that float suggests fat malabsorption, which can be observed with infection with Giardia lamblia.
• Knowledge of the characteristics of consistency, color, volume, and frequency can be helpful in determining whether the source is from the small or large bowel. Table 1 outlines these characteristics and demonstrates that an index of suspicion can be easily generated for a specific set of organisms.

Table 1. Stool Characteristics and Determining Their Source

Open table in new window

• Associated systemic symptoms include the following:
  • Some enteric infections commonly have systemic symptoms, whereas others less commonly are associated with systemic features.
  • Table 2 outlines the frequency of some of these symptoms with particular organisms. It also outlines incubation periods and usual duration of symptoms of common organisms. Certain organisms (eg, C difficile, Giardia, Entamoeba species) may be associated with a protracted course.

Open table in new window

• Daycare considerations are as follows:
  • Certain organisms are spread quickly in daycare. These organisms include rotavirus; astrovirus; calicivirus; and Campylobacter, Shigella, Giardia, and Cryptosporidium species.
  • Increase in daycare usage has raised the incidence of rotavirus and Cryptosporidium species.
• Food history can be helpful.
  • Ingestion of raw or contaminated food is a common cause.
  • Organisms that cause food poisoning include the following:
    • Dairy food -Campylobacter and Salmonella species
    • Eggs -Salmonella species
    • Meats -C perfringens and Aeromonas, Campylobacter, and Salmonella species
    • Ground beef - Enterohemorrhagic E coli
    • Poultry -Campylobacter species
    • Pork -C perfringens, Y enterocolitica
    • Seafood - Astrovirus and Aeromonas, Plesiomonas, and Vibrio species
    • Oysters - Calicivirus and Plesiomonas and Vibrio species
    • Vegetables -Aeromonas species and C perfringens
• Water exposure can contribute to diarrhea.
  • Water is a major reservoir for many organisms that cause diarrhea.
  • Swimming pools have been associated with outbreaks of infection with Shigella species; Aeromonas organisms are associated with exposure to the marine environment.
  • Giardia, Cryptosporidium, and Entamoeba organisms are resistant to water chlorination; therefore, exposure to contaminated water should raise index of suspicion for these parasites.
• A history of camping suggests exposure to water sources contaminated with Giardia organisms.
• Travel history may indicate a cause for diarrhea.
  • Enterotoxigenic E coli is the leading cause of traveler's diarrhea.
  • Rotavirus and Shigella, Salmonella, and Campylobacter organisms are prevalent worldwide and need to be considered regardless of specific travel history.
  • Risk of contracting diarrhea while traveling is, by far, highest for persons traveling to Africa.
  • Travel to Central and South America and Eastern European countries is also associated with a relatively high risk of contracting diarrhea.
  • Other organisms that are prevalent in particular parts of the world include the following:
    • Nonspecific foreign travel history - Enterotoxigenic E coli and Aeromonas, Giardia, Plesiomonas, Salmonella, and Shigella species
    • Underdeveloped tropical visit -C perfringens
    • Travel to Africa -Entamoeba species, Vibrio cholerae
    • Travel to South America and Central America -Entamoeba species, V cholerae, enterotoxigenic E coli
    • Travel to Asia -V cholerae
    • Travel to Australia -Yersinia species
    • Travel to Canada -Yersinia species
    • Travel to Europe -Yersinia species
    • Travel to India -Entamoeba species, V cholerae
    • Travel to Japan -Vibrio parahaemolyticus
    • Travel to Mexico -Aeromonas, Entamoeba, Plesiomonas, and Yersinia species
    • New Guinea -Clostridium species
• Animal exposure can contribute to diarrhea.
  • Exposure to young dogs or cats is associated with Campylobacter organisms.
  • Exposure to turtles is associated with Salmonella organisms.
• Certain medical conditions predispose patients to infection, including the following:
  • C difficile - Hospitalization, antibiotic administration
  • Plesiomonas species - Liver diseases or malignancy
  • Salmonella species - Intestinal dysmotility, malnutrition, achlorhydria, hemolytic anemia (especially sickle cell disease), immunosuppression, malaria
  • Rotavirus - Hospitalization
  • Giardia species -Agammaglobulinemia, chronic pancreatitis, achlorhydria, cystic fibrosis
  • Cryptosporidia species - Immunocompromised or immunosuppressed state

Physical

• Dehydration
  • Dehydration is the principal cause of morbidity and mortality.
  • Assess every patient with diarrhea for signs, symptoms, and severity.
  • Lethargy, depressed consciousness, sunken anterior fontanel, dry mucous membranes, sunken eyes, lack of tears, poor skin turgor, and delayed capillary refill are obvious and important signs of dehydration.
• Failure to thrive and malnutrition
  • Reduced muscle and fat mass or peripheral edema may be clues to the presence of carbohydrate, fat, and/or protein malabsorption.
  • Giardia organisms can cause intermittent diarrhea and fat malabsorption.
• Abdominal pain
  • Nonspecific nonfocal abdominal pain and cramping are common with some organisms.
  • Pain usually does not increase with palpation.
  • With focal abdominal pain worsened by palpation, rebound tenderness, or guarding, be alert for possible complications or for another noninfectious diagnosis.
• Borborygmi: Significant increases in peristaltic activity can cause an audible and/or palpable increase in bowel activity.
• Perianal erythema
  • Frequent stools can cause perianal skin breakdown, particularly in young children.
  • Secondary carbohydrate malabsorption often results in acidic stools.
  • Secondary bile acid malabsorption can result in a severe diaper dermatitis that is often characterized as a "burn."

Causes

Although infectious agents are by far the most common cause for sporadic or endemic episodes of acute diarrhea, one should not dismiss other causes that can lead to the same presentation.

• Causes of acute diarrhea include the following:
  • Infections
    • Enteric infections (including food poisoning
    • Extraintestinal infections
  • Drug-induced
    • Antibiotic-associated
    • Laxatives
    • Antacids that contain magnesium
    • Opiate withdrawal
    • Other drugs
  • Food allergies or intolerances
    • Cow's milk protein allergy
    • Soy protein allergy
    • Multiple food allergies
    • Olestra
    • Methylxanthines (caffeine, theobromine, theophylline)
  • Disorders of digestive/absorptive processes
    • Sucrase-isomaltase deficiency
    • Late-onset (adult-type) hypolactasia, resulting in lactose intolerance
  • Chemotherapy or radiation-induced enteritis
  • Surgical conditions
    • Acute appendicitis
    • Intussusception
  • Vitamin deficiencies
    • Niacin deficiency
    • Folate deficiency
  • Vitamin toxicity
    • Vitamin C
    • Niacin, vitamin B3
  • Ingestion of heavy metals or toxins (eg, copper, tin, zinc)
  • Ingestion of plants (eg, hyacinths, daffodils, azalea, mistletoe, Amanita species mushrooms
• Infectious causes of acute diarrhea in developed countries
  • Viruses
    • Rotavirus - 25-40% of cases
    • Calicivirus - 1-20% of cases
    • Norovirus - 10% of cases
    • Astrovirus - 4-9% of cases
    • Enteric-type adenovirus - 2-4% of cases
  • Bacteria
    • Campylobacter jejuni - 6-8% of cases
    • Salmonella - 3-7% of cases
    • E Coli - 3-5% of cases
    • Shigella - 0-3% of cases
    • Y enterocolitica - 1-2% of cases
    • C difficile - 0-2% of cases
    • Vibrio parahaemolyticus - 0-1% of cases
    • V cholerae - Unknown
    • Aeromonas hydrophila - 0-2% of cases
  • Parasites
    • Cryptosporidium - 1-3% of cases
    • G lamblia - 1-3% of cases

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