A change in stool consistency to watery or loose, with >3 episodes or >200g stool in 24 hours.

  • Acute: <14 days
  • Persistent: 14-30 days
  • Chronic: >30 days (Shane 2017)


  • It is difficult to obtain accurate data on the prevalence of diarrhea, as the majority of cases are self-limited with affected persons never seeking care.
  • Diarrhea is the leading cause of death worldwide in children under five years of age, with death occurring due to dehydration and electrolyte derangements.
  • Estimated prevalence:
    • Worldwide = 1.7 billion cases per year
    • USA = ~179 million cases per year, ~900,000 hospitalizations per year (Lazarciuc 2018)


  • Infectious: 85-90% of cases
    • Viral: 60%
      • Norovirus most common pathogen in USA
      • Rotavirus most common pathogen in children (Lazarciuc 2018)
    • Bacterial: 20-25%
      • E coli, Campylobacter, Salmonella, and Shigella most commonly identified pathogens (Sattar 2019)
    • Parasitic: 6%
  • Non-infectious: 10-15% of cases
    • Toxins, medication side effects, osmotic food and drink, underlying GI pathology (inflammatory bowel disease, malignancy, etc) (Lazarciuc 2018)


Resuscitate if necessary

  • Patients may be fluid depleted and require volume resuscitation
  • Give IV fluids if clinically dehydrated
  • Antibiotics with gram negative and anaerobic coverage should be given as quickly as possible if patient is hemodynamically unstable.
    • Consider addition of PO vancomycin for coverage of c difficile

Obtain relevant history

  • Ask food intake history to identify any suspect foods.
    • Consumption of raw or undercooked meats, unpasteurized dairy, or osmotic supplements may yield clues as to the causative organism.
    • Onset of symptoms within 6 hours of inoculation suggests ingestion of pre-formed toxins, usually staphylococcus or bacillus species (Riddle 2016). However, often difficult to know at what time inoculation occurred.
  • Determine nature of symptoms
    • Small bowel (more likely viral): watery, large volume stools. Often associated with abdominal cramping, bloating, and gas. Less commonly febrile.
    • Large bowel (more likely bacterial): frequent small volume stools. Stools may be bloody or mucoid. Often associated with painful bowel movements. Fever common (LaRocque 2019).
  • Exposure to poultry, livestock, turtles suggests Salmonella infection (Healy 2019)
  • Travel to developing nations should raise concern for bacterial or parasitic infection, check CDC travel advisories for specific endemic infections (Connor 2019)
  • Recent antibiotic use or hospitalization increases risk of c difficile infection (Shane 2017)

Determine whether high-risk features are present (LaRocque 2019, Shane 2017):

  • Severe abdominal pain
  • Bloody or mucoid diarrhea
  • Extremes of age (e.g. >70 years old or <3 months old)
  • Known HIV or other immunocompromise
  • Known inflammatory bowel disease
  • Co-morbidities exacerbated by hypovolemia
  • Pregnancy

Laboratory Testing

  • Complete blood count
    • Marked elevation in WBC count common in c difficile infection (Lazarciuc 2018)
    • Thrombocytopenia should raise concern for hemolytic uremic syndrome (HUS)
  • Basic metabolic panel
    • Patients may be hypokalemic. Replete as needed
    • Assess creatinine level. Acute kidney injury may be present if patient hypovolemic
  • Hepatic panel
  • Lactate
    • Only warranted if patient unwell appearing. May indicate hypoperfusion in volume depletion
  • Fecal leukocytes
    • Low utility in the ED
    • Will be elevated in any inflammatory condition. Could result from viral, bacterial, or autoimmune process such as ulcerative colitis or Crohns disease.
    • Will be low in malignancy, mesenteric ischemia
    • Classically low in amebiasis, but can be variable (Lazarciuc 2018)
  • Stool culture
    • Common assays will reliably identify campylobacter, salmonella, shigella (Lazarciuc 2018)
  • Stool ova/parasites
    • Useful in cases of chronic diarrhea, when patient is immunocompromised, or in patient from developing nation
    • Will identify e. histolitica, cryptosporidium, giardia, cyclospora (Lazarciuc 2018)
  • Specific assays:
    • Many available: examples include c diff, e. coli 0157:H7, giardia (protozoa), amebiasis
  • Urinalysis, Urine culture
    • Warranted if dysuria present, or if patient is infant or elderly to rule out UTI as cause of diarrhea
  • CT abdomen pelvis
    • Warranted if abdomen tender to palpation raising concern for acute abdomen, or if history concerning for mesenteric ischemia or other acute intraabdominal pathology


  • Not routinely needed, but contact isolation required if c difficile is suspected
  • Good hand hygiene is the most effective way to prevent spread of pathogens (Riddle 2016)
  • Use standard barrier precautions

Bloody diarrhea

The majority of diarrhea is non-bloody. The presence of blood raises concern for shiga-toxin producing e coli(O157:H7) or for non-infectious causes of diarrhea such as ischemia or inflammatory bowel disease (Shane 2017).

  • Traditional teaching is to avoid antibiotics in this case. Administration of antibiotics could cause widespread release of shiga-toxin as bacteria lyse, inducing Hemolytic Uremic Syndrome (Shane 2017).
  • This risk may be overstated in adults, but remains of concern in children (LaRocque 2019, Wong 2000).
  • Shigella, campylobacter, and salmonella may also commonly cause bloody diarrhea (Lazarciuc 2018).
  • Patients with bloody diarrhea will likely benefit from antibiotic therapy, but treatment should be delayed until stool is tested for shiga-toxin
  • If non-infectious etiology is suspected, CT abdomen pelvis likely warranted to assess underlying pathology.

C difficile

  • Suspect in patients with:
    • Profuse diarrhea, significant abdominal pain, fever
    • Recent abx exposure
    • Recent hospitalization
    • History of c difficile infection
  • Treatment:
    • Nonsevere, first time infection:
      • Vancomycin 125 mg PO 4 times per day or fidaxomicin 200 mg twice daily for 10 days
      • If oral Vancomycin and fidaxomicin unavailable, metronidazole 500 mg PO TID for 10 days is acceptable alternative
    • Severe or fulminant infection:
      • Vancomycin 500 mg PO QID
      • PLUS Metronidazole 500mg IV every 8 hours
      • If Ileus present, ADD Vancomycin 500 mg in 100 mL normal saline per rectum every 6 hours as a retention enema (McDonald 2018)

HIV / other immunocompromise

  • When infected with common pathogens, immunocompromised patients may present with more severe disease
  • In addition, these patients are at increased risk of infection from:
    • Viruses: particularly cytomegalovirus
    • Mycobacterium avium
    • Parasites such as cryptosporidium, microsporidium, and giardia
  • Patients with HIV may also suffer from primary HIV enteritis and are at increased risk of malignancies such as Karposi sarcoma and lymphoma, which may also present with diarrhea (NIAID 1995).

Anal receptive intercourse

  • In addition to enteric flora, patients engaging in anal receptive intercourse may develop proctitis and diarrhea from sexually transmitted infections such as chlamydia, gonorrhea, syphilis, herpes simplex virus (Shane 2017).


  • Pregnant women are ten times more likely to be infected with Listeria than the general population, and may present as diarrheal illness
  • Maternal Listeria infection can result in fetal infection, so testing for Listeria and/or empiric treatment with ampicillin or penicillin should be considered in the pregnant patient presenting with diarrhea (ACOG 2014).


  • Rare in developed countries, but endemic in developing countries – particularly Africa and Southeast Asia.
  • Exposure usually from:
    • Developed countries: undercooked shellfish
    • Developing countries: unclean water and poor sanitation
  • Classically presents with profuse “rice-water” diarrhea and severe dehydration
  • Treatment centers on oral rehydration therapy (N’cho 2019).
  • Patients with severe disease benefit from doxycycline (azithromycin for pregnant women and children)


  • Specific strain of Salmonella leading to typhoid fever
  • Endemic to much of the developing world
  • May present with concurrent fever and relative bradycardia, elevated transaminases, characteristic red macular rash on trunk
  • Asymptomatic carriers may develop, so major public health concern
  • Typically treated with ciprofloxacin
    • Other options are azithromycin or cephalosporins (Appiah 2019)


  • Classically causes nausea, vomiting, and diarrhea for 48-72 hours with rapid resolution of symptoms
  • May be identified using GI pathogen panel PCR testing
  • Usually self-limiting for an individual patient, but is extremely contagious and thus a public health concern.
  • Norovirus requires special disinfection
    • Clorox wipes and alcohol-based hand sanitizers ineffective Shane 2017).


Indications for Hospitalization

  • Toxic appearance / severe dehydration requiring IV rehydration
  • Marked electrolyte derangements
  • Inability to tolerate PO fluids
  • Severe symptoms in any high risk patient group (Lazarciuc 2018).

Low risk patient

If the patient has no high risk features and no hemodynamic instability, discharge home with oral hydration and return precautions. Oral hydration is preferred over enteral. No antibiotic treatment is recommended.

If patient has bloody diarrhea (after first ruling out e coli O157:H7), severe symptoms (fever, >6 episodes per day), dehydration, or foreign travel, empiric antibiotic treatment may be warranted.

Outpatient antibiotic regimens:

  • Azithro 1g once or 500mg PO daily for 3 days
  • Ciprofloxacin – 750mg PO daily or 500mg PO twice daily for 3-5 days
  • Levofloxacin – 500mg PO daily for 3-5 days (Shane 2017)

Symptomatic Treatment:

  • Loperamide – may be considered in nonbloody diarrhea (Riddle 2016)
  • Bismuth subsalicylate – less efficacious than loperamide (Riddle 2016)
  • Probiotics – may shorten length of symptoms and frequency of bowel movements. Appears lactobacilli most effective (Riddle 2016, Allen 2010)


  • No proven benefit to any specific diet during diarrheal illness
  • Generally recommended to consume simple starches such as pasta, bread, or fruit, and to avoid foods heavy in fats or lactose
  • Oral rehydration with diluted sports drinks or specifically designed formulas is beneficial (Riddle 2016)


  • Diarrhea is an extremely common complaint, with the vast majority of cases being self-limited
  • Care of patients with diarrhea centers on management of volume status and electrolyte repletion
  • Majority of patients require no testing unless history or exam reveal high risk features
  • Be cautious with certain patient groups such as the young, elderly, pregnant women, and the immunocompromised.
  • Avoid antibiotic use in the majority of cases. Antibiotics may be considered in patients with severe symptoms, travel to endemic areas, or bloody diarrhea after testing for shiga-toxin.


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