Pediatric Diarrhea

Diarrhea is described as passage of large amounts stools that are often loose, liquid, or watery, resulting in excess loss of fluids and electrolytes. Diarrhea is one of the most common illnesses in children, representing the largest percentages of morbidity and mortality worldwide in the pediatric age group. The majority of cases are infectious, caused by rotavirus, while the rest are caused by bacteria (Escherichia coli, Salmonella) and parasites (Entamoeba histolytica). Management is largely based on rehydration; antibiotic therapy is used only when indicated. Prognosis is excellent if diarrhea promptly treated.

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Diarrhea is defined as excess stool output that is often loose or watery.

Quantification of stool output varies:

  • > 10 mL/kg/day in infants and > 200 g/day in older children, causing excessive loss of fluid and electrolytes
  • Passing ≥ 3 loose watery stools per day (WHO definition)


  • By time of onset:
    • Acute, if it lasts ≤ 2 weeks
    • Chronic, if it lasts > 2 weeks
  • By etiology:
    • Osmotic
    • Secretory
    • Inflammatory
    • Motility-related


  • Leading cause of morbidity and mortality worldwide:
    • In developed countries, acute diarrhea is most common and is associated with lower rates of morbidity and mortality.
    • In developing countries, chronic diarrhea is more common and more lethal.
  • Most common illness of the healthy child:
    • Worldwide, children < 5 years old have an average of 2–3 episodes each year.
  • Most common form is viral diarrhea:
    • Rotavirus is the most common causal agent.



Infants and young children:

  • Infectious:
    • Viral gastroenteritis (rotavirus (most common), Norwalk virus (often seen among cruise ship passengers))
    • Bacterial enteritis (Escherichia coli (commonly seen in nurseries and day care centers), Salmonella (eggs, milk, poultry, reptiles, pets), Shigella (contaminated food), Campylobacter (contaminated food), Yersinia (pets, contaminated food), Clostridium difficile (prior antibiotic use), Staphylococcus aureus (egg products))
    • Parasitic (Entamoeba histolytica, Giardia (commonly seen among hikers), Cryptosporidium)
    • Systemic infections
  • Noninfectious:
    • Antibiotic-associated
    • Hirschsprung toxic colitis
    • Neonatal narcotic withdrawal
    • Congenital adrenal hyperplasia

Older children:

  • Infectious:
    • Viral gastroenteritis
    • Bacterial enteritis
    • Food poisoning
  • Noninfectious:
    • Antibiotic-associated diarrhea (e.g., amoxicillin–clavulanic acid)
    • Appendicitis


Infants and young children:

  • Infectious:
    • Parasites
    • Appendiceal abscess
  • Malabsorption:
    • Postinfectious lactase deficiency
    • Food protein intolerance
    • Toddler’s diarrhea
    • Cystic fibrosis
    • Celiac disease
  • Inflammatory:
    • Eosinophilic
    • Gastroenteritis
  • Immunodeficiency:
    • SCID
    • HIV enteropathy
  • Endocrine: adrenal insufficiency
  • Other:
    • Lymphangiectasia
    • Toxins
    • Rare congenital bowel disorders

Older children:

  • Infectious:
    • Parasites
    • Appendiceal abscess
  • Malabsorption:
    • Lactose intolerance
    • Laxative abuse
    • Celiac disease
    • Secretory neoplasm
  • Inflammatory:
    • Eosinophilic gastroenteritis
    • Irritable bowel syndrome
  • Immunodeficiency: HIV enteropathy
  • Endocrine:
    • Adrenal insufficiency
    • Hyperparathyroidism and hypoparathyroidism
  • Other:
    • Constipation (encopresis)
    • Irritable bowel syndrome
    • Toxins



  • Mechanism:
    • ↓ GI absorption of fluids/solutes 
    • ↑ GI secretion of fluids/solutes 
    • Electrolyte transport defects
    • Can be caused by a secretagogue (e.g., cholera toxin)
  • Causative agents:
    • Cholera
    • E. coli 
    • Carcinoid
    • Neuroblastoma
    • Congenital chloride diarrhea
    • Clostridium difficile 
    • Cryptosporidiosis (AIDS)
  • Clinical features:
    • Persists during fasting
    • Bile salt malabsorption can also increase intestinal water secretion
    • No stool leukocytes


  • Mechanism:
    • Indigestible substances change osmotic gradients in the GI tract.
    • Fluid is pulled out of GI lining rather than flowing into it.
  • Causative agents:
    • Lactase deficiency
    • Glucose–galactose malabsorption
    • Lactulose
    • Laxative abuse
  • Clinical features:
    • Stops with fasting
    • ↑ Breath hydrogen with carbohydrate malabsorption
    • No stool leukocytes

Increased motility

  • Mechanism: 
    • Pathologically hyperactive bowels 
    • ↓ GI transit time
    • Food is not digested and is rapidly excreted.
  • Causative agents:
    • Irritable bowel syndrome
    • Thyrotoxicosis
    • Postvagotomy dumping syndrome
  • Clinical feature: Infection can contribute to increased motility.

Decreased motility

  • Mechanism: 
    • Defect in neuromuscular unit(s) 
    • Stasis leading to bacterial overgrowth
  • Causative agents:
    • Pseudo-obstruction
    • Blind loop
    • Hirschsprung disease
  • Clinical feature: possible bacterial overgrowth

Decreased surface area

  • Mechanism: ↓ functional capacity
  • Causative agents:
    • Short bowel syndrome
    • Celiac disease
    • Rotavirus enteritis
  • Clinical feature: might require elemental diet plus parenteral alimentation

Mucosal invasion

  • Mechanism: 
    • Inflammation
    • Decreased colonic reabsorption
    • Increased motility
  • Causative agents:
    • Salmonella 
    • Shigella 
    • Amebiasis
    • Yersinia
    • Campylobacter
  • Clinical feature: Dysentery evident in blood, mucus, and WBCs.

Clinical Presentation


  • Important associated signs and symptoms:
    • Fever
    • Blood or mucus in the stool
    • Exposure to farm animals and reptiles (Salmonella, E. coli) for hemolytic uremic syndrome in children
    • Suspicious foods
    • Recent travel 
    • Recent antibiotic use
  • When caused by a virus:
    • 7–10 days of watery diarrhea
    • Vomiting
    • Some children may have upper respiratory symptoms.
  • When caused by bacteria:
    • High fever
    • Bloody stools
    • Abdominal pain
    • Shigella infection may be accompanied by seizures.

Physical examination

  • Signs of dehydration:
    • Dry oral mucous membranes
    • ↓ Skin turgor 
    • ↓ Capillary refill
    • Sustained tachycardia
    • BP usually remains high until extreme dehydration occurs.
  • Signs of systemic infection:
    • ↓ Level of consciousness
    • Fever
  • Abdominal exam: Look for rebound and guarding.
  • Delayed growth and weight gain
  • Perianal inspection can show tags or fissures in Crohn’s disease.
  • Yersinia infection associated with:
    • Arthritis and rash
    • Pseudo-appendicitis
Table: Degree of dehydration in children
Weight loss
  • < 5% in infants
  • < 3% in older children
  • 5%–10% in infants
  • 3%–9% in older children
  • > 10% in infants
  • > 9% in older children
Dry mucosa (1st sign)+/–, looks dry+, looks parched
Skin turgor (last sign)++/–++/+
Anterior fontanelle depression+++/+
Mental statusNormalFatigue/irritabilityApathy/lethargy
BreathingNormalDeep, may be tachypneicDeep and tachypneic
HRNormalIncreasedVery high
Distal perfusionNormal
  • Feels cold
  • 3–4 seconds
  • Acrocyanotic
  • > 4 seconds
Urinary outputDecreasedOliguriaOliguria/anuria


Workup is generally not needed and is indicated only in cases of moderate to severe dehydration, immunocompromise, and sepsis and in chronic cases.

  • Labs:
    • Basic metabolic panel (BMP)  in cases of severe dehydration can show: 
      • ↓ Glucose 
      • ↑ BUN
      • ↑ Sodium and chloride
      • ↓ Bicarbonate
      • ↑ Creatinine
    • Stool microscopy, looking for ova and parasites
    • Stool culture
    • If hemolytic uremic syndrome is suspected: specific testing for E. coli O157:H7
    • If failure to thrive is suspected:
      • Cystic fibrosis: stool elastase, sweat test
      • Irritable bowel disease (IBD): ↑ inflammatory markers, erythrocyte sedimentation rate (ESR)/CRP, fecal calprotectin
      • Malabsorption: stool-reducing substances, fecal fat
      • Immunodeficiency: HIV, lymphocyte enumeration, Ig profile
  • Diagnostic imaging: endoscopy/colonoscopy in special cases (e.g., children with unresolved emesis or suspected IBD)


  • Supportive care only for most cases:
    • Fluid replacement therapy in children
    • Proper nutritional recovery: Encourage feeding during and after diarrheal episodes.
  • Antibiotics for children who are:
    • Severely ill 
    • Immunocompromised 
  • Prevention:
    • Exclusive breastfeeding until 6 months of age
    • Vaccinations against rotavirus and cholera in endemic zones
    • Education about:
      • Proper washing and disinfecting of food
      • Adequate food waste disposal
      • Boiling water
      • Handwashing, especially after defecating, and other hygiene habits

Clinical Relevance

  • Hirschsprung toxic colitis: congenital nonobstructive dilation of the colon associated with systemic toxicity. In Hirschsprung toxic colitis, inflammation of the intestinal lining causes distention and diarrhea and often requires colectomy at a young age.
  • Appendicitis: inflammation and infection of the appendix causing RLQ pain and fever and may present with vomiting and diarrhea. In pediatrics, the imaging of choice for appendicitis is ultrasonography and management is with surgery.
  • Cystic fibrosis: autosomal recessive disorder caused by a mutation in the CFTR gene associated with chronic pulmonary infections and pancreatic malfunction. In addition to pulmonary symptoms, GI symptoms can include chronic diarrhea. Children present at an early age, and screening is performed routinely in the United States.
  • Celiac disease: also called gluten-sensitivity enteropathy. Celiac disease is characterized by gluten intolerance that produces recurrent diarrhea. Diagnosis by colon biopsy is the gold standard, but assays are available for screening stool. Management is with avoidance of gluten.
  • Irritable bowel syndrome: chronic GI motility disorder with no organic cause, characterized by irregular bowel habits, abdominal pain, and GI symptoms that include flatulence and diarrhea. Management is supportive.
  • Crohn’s disease: inflammatory bowel disease characterized by immune-mediated colonic inflammation. Diarrhea is frequently experienced by individuals with inflammatory bowel diseases. Management is with immunosuppressive agents such as steroids.


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