• Diarrhea is an increase in frequency, volume, or fluidity of a patient’s stool as compared to the normal bowel movement pattern.
  • On the basis of its duration, diarrhea can be classified as acute (<14 days), persistent (14 to 29 days), or chronic (>30 days).
  • Acute diarrhea typically presents abruptly with increased fluid content of the stool >10 mL/kg/24 h and lasts <14 days; usually involves the passage of >250 g/24 h of unformed stool
  • Persistent diarrhea can also begin acutely but last for ≥14 days.
  • Diarrhea is caused whenever there is disruption of the normal absorptive and secretory functions of intestinal mucosa.
  • Malabsorption, maldigestion, cellular electrolyte pump dysfunction, and intestinal colonization or invasion by microorganisms can cause diarrhea.
  • Tenesmus, perianal irritation or discomfort, and fecal incontinence may occur with all forms of diarrhea.


Approach to patient

  • The first step in the clinical appraisal of the patient with diarrhea is to identify what the patient “means” by diarrhea; exclude the possibility of fecal impaction with overflow diarrhea and/or incontinence; rule out drug-induced diarrhea; distinguish acute from chronic; categorize as inflammatory, fatty, or watery; and consider the possibility of factitious diarrhea.
  • It is important to determine the type of diarrhea (osmotic vs. secretory), as this will alter your diagnostic and therapeutic plan.
    • Secretory diarrhea
      • Absorption of intestinal fluid and electrolytes is accomplished through multiple cellular pumps transporting sodium (Na), glucose, and amino acids.
      • Factors that interrupt these pumps (e.g., cholera toxin, prostaglandin E, vasoactive intestinal peptide, secretin, acetylcholine) can cause a severe active isotonic secretory state manifested by profuse diarrhea, dehydration, and acidosis. Other causes include bile acid malabsorption, inflammatory bowel disease, disordered regulation (postvagotomy, diabetic neuropathy), peptide-secreting endocrine tumors, and neoplasia (colon carcinoma, lymphoma, villous adenoma).
    • Osmotic diarrhea
      • In general, the solute composition of intestinal fluid is similar to that of plasma.
      • Osmotic diarrhea occurs when poorly absorbed or nonabsorbable solute is present in the intestinal lumen (this may result in low stool pH <6).
      • This can occur with the ingestion of nonabsorbable sugars (e.g., sorbitol), cathartics (e.g., magnesium citrate); carbohydrate malabsorption secondary to mucosal damage (e.g., lactose); maldigestion (e.g., pancreatic dysfunction), rapid transit of intestinal fluid; or with a rare congenital transport defect.


  • Question: Duration? (<14 days, >30 days)
  • Significance: A distinction should be made between acute and chronic diarrhea. The cause of acute diarrhea is almost always related to an infection, a medication, or the addition of a new food.
  • Question: Travel history?
  • Significance: Questions should be asked regarding travel to areas where drinking water is contaminated (e.g., Entamoeba in Mexico) or food handling/preparation is prolonged or unsanitary (e.g., Campylobacter, Bacillus cereus, or E. coli); exposure to freshwater streams or ponds (e.g., Cryptosporidium, Giardia)
  • Question: Recent use of antibiotics?
  • Significance: A variety of antibiotics can be associated with C. difficile colitis or antibiotic-related diarrhea.
  • Question: Adolescents?
  • Significance: Questions should be asked regarding body image and weight. Laxative abuse causing an osmotic diarrhea is common among adolescents who have an eating disorder or athletes attempting to lose weight rapidly.
  • Question: Family history?
  • Significance: conditions with genetic susceptibility (e.g., inflammatory bowel disease, celiac disease)
  • Question: Systemic symptoms?
  • Significance: It is important to ask about concomitant fever, GI bleeding, rashes, or vomiting. Certain GI infections and inflammatory bowel disease have specific associated systemic symptoms.
  • Question: Hematochezia?
  • Significance: The occurrence of acute, bloody stools and fever generally indicates a bacterial infection. However, these same symptoms coupled with fatigue, poor urine output, and history of easy bruising may suggest hemolytic uremic syndrome. Bloody stools in combination with a history of crampy abdominal pain, arthritis, and purpuric rash can indicate HSP, a completely different entity. Chronic bloody diarrhea, abdominal pain, and weight loss are characteristic of inflammatory bowel disease.
  • Question: Steatorrhea? (greasy or bulky stools)
  • Significance: indicates fat malabsorption (e.g., cystic fibrosis)
  • Question: Age? (congenital vs. acquired)
  • Significance: The age of the child is important because a number of diseases present between birth and 3 months of life including cystic fibrosis, milk or soy protein intolerance, and congenital enteropathies (e.g., microvillus inclusion disease, tufting enteropathy).
  • Question: Previously well infant with recent viral illness and subsequent protracted diarrhea?
  • Significance: Postviral enteritis should be suspected. This disorder is characterized by severe mucosal injury resulting in transient disaccharidase deficiency and potentially prolonged malabsorption.
  • Question: Normal preschool-aged children who have 2 to 10 watery stools per day with normal growth?
  • Significance: Chronic nonspecific diarrhea of childhood (a.k.a. functional diarrhea) should be considered. Assess juice and dietary sugar intake.
  • Question: Lactose intolerance?
  • Significance: commonly occurs in many older children and adults, with >95% occurrence rate in some ethnic groups
  • Question: Chronic diarrhea with weight loss?
  • Significance: Inflammatory or immunologic disorders such as ulcerative colitis, Crohn disease, and celiac disease must be ruled out. Celiac disease is an immune-mediated enteropathy caused by dietary gluten intake in genetically susceptible individuals; occurs in ~1:130 of the U.S. population with a genetic predisposition and should be considered in any child with chronic diarrhea and poor weight gain

Physical Exam

  • Finding: Stool in left lower quadrant and/or a history of encopresis?
  • Significance: Chronic loose stools are common in children with functional constipation and large fecal impaction due to overflow incontinence and can be easily mistaken for diarrhea.
  • Finding: Child’s growth parameters?
  • Significance: Previous measurements and growth curves are necessary to make an accurate evaluation. Findings of a chronically malnourished child with years of weight loss or poor growth velocity would indicate a divergent differential diagnosis from that of a healthy-appearing child with a history of normal growth.
  • Finding: Arthritis and rash?
  • Significance: Diarrhea accompanied by these signs can occur in diseases such as inflammatory bowel disease, celiac disease, HSP, and specific bacterial infections.
  • Finding: Oral ulcers?
  • Significance: occur in inflammatory bowel disease and celiac disease
  • Finding: Dehydration?
  • Significance: Capillary refill >3 seconds, tachycardia without pain or fever, and dry mucous membranes provide clues to dehydration.
  • Finding: Nail bed clubbing?
  • Significance: This finding may direct questioning to rule out cystic fibrosis or chronic inflammatory bowel disease.
  • Finding: Masses?
  • Significance: A right lower quadrant mass could suggest an abscess (e.g., terminal ileitis in Crohn disease or appendiceal abscess) or intussusception (e.g., irritable child with currant jelly-like stools).

Differential Diagnosis

  • Acute diarrhea
    • Dietary causes
      • Sorbitol, fructose, lactose, and intolerance to specific foods (beans, fruit, peppers, etc.)
    • Infectious causes:
      • Bacterial (e.g., Escherichia coli, Clostridium difficile, Salmonella, Shigella, Campylobacter, Yersinia)
      • Viral (e.g., rotavirus, norovirus, adenovirus)
      • Parasites (e.g., Giardia, Cryptosporidium, Entamoeba histolytica)
    • Medications
      • Antibiotics, laxatives
  • Chronic diarrhea
    • Allergic/autoimmune
      • Milk/soy protein allergy, eosinophilic enteritis, Henoch-Schönlein purpura (HSP), celiac disease, autoimmune enteropathy, or microscopic colitis
    • Immunodeficiency
      • HIV/AIDS, chronic granulomatous disease, hyper IgM, severe combined immunodeficiency
    • Anatomic abnormalities
      • Short bowel syndrome (e.g., history of necrotizing enterocolitis, Hirschsprung, malrotation, inflammatory bowel disease)
    • Bile acid malabsorption
    • Congenital
      • Cystic fibrosis, microvillus inclusion disease, tufting enteropathy, or IPEX syndrome
    • Encopresis
    • Endocrine disorders
      • Hyperthyroidism, diabetes, congenital adrenal hyperplasia
    • Bacterial overgrowth (e.g., blind loop, ostomy)
    • Inflammatory bowel disease
      • Ulcerative colitis, Crohn disease
    • Intestinal lymphangiectasia
      • Primary and secondary
    • Irritable bowel syndrome
    • Lactose intolerance
      • Primary, secondary, and congenital
    • Pancreatic exocrine dysfunction
      • Shwachman-Diamond syndrome, cationic trypsinogen deficiency, Jeune syndrome, Pearson syndrome, and Johanson-Blizzard syndrome
    • Postinfectious enteropathy
    • Secretory tumors
      • VIPoma, somatostatinoma, gastrinoma, carcinoid, glucagonoma

Diagnostic Tests and Interpretation

  • Test: stool culture
  • Significance: Stool examination for blood, mucus, inflammatory cells, and microorganisms is an important first step in determining the cause of the diarrhea. Stool cultures for parasites (e.g., Giardia, Cryptosporidium, Entamoeba), bacterial pathogens (e.g., Salmonella, Campylobacter, Shigella, Yersinia, Aeromonas, Plesiomonas), viral particles, and C. difficile toxin should be appropriately obtained in all children with unexplained diarrhea.
  • Test: stool pH and reducing substances
  • Significance: These tests are useful in identifying carbohydrate malabsorption. A stool pH <5 to 6 and stool-reducing substances >0.5–1% is suggestive of malabsorption.
  • Test: stool osmolality and electrolytes
  • Significance: Stool osmolality, stool Na, and stool K can be used to calculate an ion gap and differentiate between secretory and osmotic diarrhea.
    • Stool osmotic gap = measured stool osmolality − estimated stool osmolality
    • Estimated stool osmolality = 2 (Na stool + K stool)
    • An increased stool osmotic gap is >50 mOsm/kg.
  • Test: stool guaiac test (Hemoccult®)
  • Significance: Sensitive and specific test is helpful in distinguishing truly heme-positive stools from ingested foods/drinks with artificial or natural red coloring. Stool positive for blood is suggestive of bacterial or inflammatory causes.
  • Test: 72-hour quantitative fecal fat evaluation
  • Significance: This is a sensitive test for steatorrhea. Patients need to be placed on a high-fat diet (2 to 4 g/kg) for a minimum of 1 day prior to testing.
    • Over 3 days, all stool is collected, refrigerated, and tested. A diet record needs to be performed for the 3 days that correspond to the stool collection period.
    • The coefficient of fat absorption is calculated: grams of fat ingested − grams of fat excreted/grams of fat ingested × 100.
    • Normal values are as follows:
      • Premature infants: 60–75%
      • Newborns: 80–85%
      • Children 10 months to 3 years: 85–95%
      • Children >3 years: 93%
    • When fat malabsorption is present, disorders of pancreatic function (e.g., cystic fibrosis, Shwachman-Diamond syndrome) or severe intestinal disease should be suspected.
  • Test: lactose breath test
  • Significance: This noninvasive test measures hydrogen levels and or methane. It is based on the principle that hydrogen gas is produced by colonic bacterial fermentation of malabsorbed carbohydrates. When abnormal in older healthy-appearing children, primary lactase deficiency is likely. However, in young children, a secondary lactase deficiency should be considered and small-bowel disease should be ruled out.
  • Test: D-xylose test
  • Significance: This serum test is an indirect measure of functional small bowel surface area. D-xylose absorption in the blood occurs independent of bile salts, pancreatic enzymes, and intestinal disaccharidases. A specific dose of D-xylose (1 g/kg, maximum 25 g) is given orally after an 8-hour fast, and the serum level of D-xylose is determined after 1 hour. Levels <15 to 20 mg/dL in children is abnormal and suggestive of disorders that alter or disrupt intestinal mucosa absorption.
  • Test: fecal calprotectin
  • Significance: Calprotectin is a neutrophilic protein detected in stools in inflammatory conditions.
  • Test: endoscopy and colonoscopy
  • Significance: Direct visualization of the intestinal mucosa as well as intestinal culture, disaccharidase collection, and biopsies can provide clues to diagnosis.
  • Test: celiac panel
  • Significance: This includes a tissue transglutaminase IgA, quantitative IgA level, and endomysial antibody.


General Measures

  • The key elements in treatment of diarrhea are as follows: (i) correction of hydration, (ii) correction of electrolytes, and (iii) specific treatment of underlying cause when indicated.
  • Rehydration is the cornerstone of treatment.
  • Oral rehydration therapy with glucose concentrations of 111 mmol/L and 90 mmol/L Na is recommended.
  • IV rehydration is indicated for patients who are severely dehydrated and unable to tolerate oral feedings.

Issue for Referral

Children who present with growth failure, noninfectious heme-positive diarrhea, or unexplained chronic diarrhea should be considered for referral to a pediatric gastroenterologist.

Inpatient Consideratons

Diarrhea can lead to significant dehydration and electrolyte imbalance. Any child suspected of clinical dehydration should be closely observed. Only if oral rehydration is ineffective is IV therapy indicated. Culture-negative GI bleeding associated with severe abdominal pain and diarrhea should always be treated urgently.

  • Antibiotics
    • Vibrio cholerae, Shigella, and Giardia lamblia require antimicrobial therapy (i.e., trimethoprim/sulfisoxazole, azithromycin, tetracycline, ciprofloxacin, metronidazole).
    • Prolonged courses of enteropathogenic E. coli, Yersinia in patients with sickle cell disease, and Salmonella species infections in the very young febrile or bacteremic infant require antimicrobial therapy.

Ongoing Care


  • Breastfeeding should continue during episodes of gastroenteritis, as it promotes mucosal healing.
  • A regular diet should be resumed as soon as possible. Dietary limitations are not indicated and can delay nutritional recovery.
  • Micronutrient supplementation
    • Zinc supplementation at a dose of 20 mg/24 h for children >6 months and 10 mg/24 h in those <6 months for 10 to 14 days during episodes of acute diarrhea has been shown to decrease severity and duration as well as preventing future episodes in malnourished children.
  • Probiotics and Prebiotics
    • Have been used for both prevention and treatment of diarrhea
    • Lactobacillus rhamnosus GG has been shown to shorten the duration of diarrheal illness and viral shedding (e.g., rotavirus).
    • Best evidence for effectiveness in antibiotic-associated diarrheas, rotavirus, and recurrent C. difficile

Additional Reading

  1. Aomatsu T, Yoden A, Matsumoto K, et al. Fecal calprotectin is a useful marker for disease activity in pediatric patients with inflammatory bowel disease. Dig Dis Sci. 2011;56(8):2372–2377.  [PMID:21394462]
  2. Castelli F, Saleri N, Tomasoni LR, et al. Prevention and treatment of traveler’s diarrhea. Focus on antimicrobial agents. Digestion. 2006;73(Suppl 1):109–118.  [PMID:16498259]
  3. Gore JI, Surawicz C. Severe acute diarrhea. Gastroenterol Clin North Am. 2003;32(4):1249–1267.  [PMID:14696306]
  4. Guandalini S. Probiotics for prevention and treatment of diarrhea. J Clin Gastroenterol. 2011;(Suppl 45):S149–S153.  [PMID:21992955]
  5. Hartling L, Bellemare S, Wiebe N, et al. Oral versus intravenous rehydration for treating dehydration due to gastroenteritis in children. Cochrane Database Syst Rev. 2006;(3):CD004390.  [PMID:16856044]
  6. Patel K, Thillainayagam AV. Diarrhea. Medicine. 2009;37(1):23–27.
  7. Scharf RJ, Deboer MD, Guerrant RL. Recent advances in understanding the long-term sequelae of childhood infectious diarrhea. Curr Infect Dis Rep. 2014;16(6):408.  [PMID:24819871]
  8. Surawicz CM. Mechanisms of diarrhea. Curr Gastroenterol Rep. 2010;12(4):236–241.  [PMID:20532705]
  9. Thielman NM, Guerrant RL. Clinical practice. Acute infectious diarrhea. N Engl J Med. 2004;350(1):38–47.  [PMID:14702426]



  • 787.91 Diarrhea
  • 558.9 Other and unspecified noninfectious gastroenteritis and colitis
  • 009.2 Infectious diarrhea


  • R19.7 Diarrhea, unspecified
  • K52.9 Noninfective gastroenteritis and colitis, unspecified
  • A09 Infectious gastroenteritis and colitis, unspecified


  • 62315008 Diarrhea (finding)
  • 409966000 Acute diarrhea (disorder)
  • 236071009 Chronic diarrhea (disorder)
  • 236076004 Infective diarrhea (disorder)
  • 69980003 non-infective diarrhea (disorder)


Kerri Gosselin, MD, MPH

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