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Category: Family Medicine | Gastroenterology | Internal Medicine

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Acute diarrhea overview

Published: March 31, 2017. Updated: April 01, 2017

Diarrhea is defined as either the passage of stools that are loose in consistency, the passage of 3 or more stools per day or the passage of at least 200mg (150ml) per day.


Inflammatory/invasive diarrhea (dysentery)

  • Diarrhea +inflammatory signs (blood, mucus, fever) suggests infection of the large bowel.
  • Common organisms: CHEESSY

Severe diarrhea

  • Diarrhea + hypovolemia, passage of ≥ 6 unformed stools per day, need for hospitalization.

Acute diarrhea

  • >Diarrhea of ≤ 2 weeks duration.

Most cases of acute diarrhea are infectious and the majority of those are self-limited (viral etiology). However, most cases presenting with severe diarrhea or inflammatory diarrhea have a bacterial etiology and may require culture and empiric antibiotic treatment.

Exposure history listed below canprovide further narrow down the potential pathogen:

  1. Food poisoning (vomiting):
    • Within 6 hours: suggests ingestion of a preformed toxin of Staphylococcus aureus or Bacillus cereus, particularly if nausea and vomiting were the initial symptoms
    • At 8 to 16 hours: suggests infection with Clostridium perfringens
    • At > 16 hours: suggests either viral or other bacterial infection (eg, contamination of food with enterotoxigenic or EHEC or other pathogens)
    • Campylobacter (most common cause of invasive diarrhea in U.S.)
    • Protozoal (Ova and parasitespresent in stools)
      • Cryptosporidium (HIV positive), no therapy.
      • Giardiasis (history of camping or homosexual behaviour), treat with metronidazole or tinidazole, with quinacrine as an alternative.
      • Symptomatic amebiasis (amebic dysentry): travelers to areas with poor sanitation and in homosexual men. Confirm diagnosis with stool examination for Entameba hystolitica trophozoites or cysts or serum antibody test. It is treated with metronidazole, followed by paromomycin or iodoquinol to eliminate cysts.
    • Preformed toxin ingestion (5-6 hours incubation period - only important when evaluating outbreaks)
      • Staphylococcus ingestion: Mainly upper GI symptoms. Staphylococcal enteritis is caused by eating food contaminated with staph enterotoxin. The toxin, not the bacterium, settles in the small intestine and cause inflammation and swelling. Treatment is therefore mainly supportive and antibiotics are not indicated.
      • Bacillus cereus: Chinese food. Mainly upper GI symptoms. It is the most common bacillus infection in humans. Antibiotic therapy is not indicated for treatment of toxin-mediated food poisoning caused by B. cereus.
    • E. coli: HUS, hamburgers, traveller
    • Vibrio parahaemolyticus: Shellfish ingestion. Watery diarrhea.
    • Scombroid: causes acute gastroenteritis in minutes (fish which is packed with histamines).
  2. Traveler’s diarrhea:
    • Campylobacter jejuni,E.coli, entameoba histolytica, salmonella, shigella.
    • Treated with
    • Antibiotics can increase the possibility of hemolytic-uremic syndrome associated with Shiga toxin– producing E. coli infections (E. coli O157: H7), especially in children and the elderly [1].
  3. Exposure to animals:
    • Salmonella: Poultry (chicken, eggs—> infected chicken ovary)
  4. Occupational exposure
    • Daycare centers:Shigella, Cryptosporidium, and Giardia, viral gastroenteritis from children.
  5. Medicinal exposure:

    • Antibiotic-associated diarrhea: Clostridium difficile infection causes pseudomembranous colitis. Diagnosed with toxin test. C. difficile infections are preventable. Treatment: Oral metronidazolefor mild to moderate cases. Oral vancomycin is used for resistant cases[2]. Fidaxomicin and fecal microbiota transplant are alternativeoptions.
  6. Other risk factors:
    • Pregnancy increases the risk of listeriosis following infections of contaminated meat products or unpasteurized dairy products.
    • Cirrhosis is associated with Vibrio infection.
    • Hemochromatosis is associated with Yersinia infection.


  • Fluid repletion including IV hydration in severe cases, represents an essential initial step in the therapy of diarrheal disease.
  • Symptomatic therapy:
    • Loperamide, opiates (tincture of opium, belladonna, and opium capsules), and anticholinergic agents (diphenoxylate and atropine [Lomotil]) are the most effective nonspecific antidiarrheal agents.
    • Pectin and kaolin preparations (bind toxins) and bismuth subsalicylate (antibacterial properties) are also useful in symptomatic therapy of acute diarrhea.
    • Bile acid– binding resins (e.g., cholestyramine) are beneficial in bile acid– induced diarrhea.
    • Octreotide is useful in hormone-mediated secretory diarrhea but can also be of benefit in refractory diarrhea.
  • Empiric antibiotic therapy is only recommended in patients with moderate-to-severe disease and associated systemic symptoms while awaiting stool cultures.

    • Oral fluoroquinolone (ciprofloxacin 500 mg twice daily, levofloxacin 500 mg once daily, or norfloxacin 400 mg twice daily [not available in the US]) for up to five days.
    • Alternative: Azithromycin (500 mg PO once daily for three days) or erythromycin (500 mg PO twice daily for five days).


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