Diarrhea is a change in normal bowel movements characterized by increase in frequency, water content or volume of stools. The usual stool output is 10 g/kg/day.
Acute diarrhea lasts ≤14 days while chronic diarrhea lasts >14 days.
Infectious diarrhea is usually associated with symptoms of nausea and vomiting and abdominal cramps.


Watery Diarrhea

  • Semi-formed to loose-watery stools without the presence of blood
  • Often clinical presentation of enterotoxin-induced diarrhea

Bloody Diarrhea

  • Bloody diarrhea is considered if macroscopic exam of stools contains blood


  • Diarrhea: Change in normal bowel movements characterized by increase in frequency (3 times within 24 hours), water content or volume of stools or with bloody stools
    • Usual stool output is 10 g/kg/day
  • Acute diarrhea: Diarrhea lasting ≤14 days duration
    • Chronic diarrhea is a diarrhea lasting >14 days
  • Infectious diarrhea: Diarrhea of infectious origin & is usually associated with symptoms of nausea & vomiting & abdominal cramps


Watery Diarrhea 

  • Severe dehydration with severe watery diarrhea is most likely caused by Vibrio cholerae subgroup O1
  • Vibrio O139, other non-O1 vibrios & occasionally Vibrio parahaemolyticusAeromonas sp & enteropathogenic Escherichia coli can cause a similar clinical picture (though diarrhea by these organisms usually causes milder forms of diarrheal illness)
  • Cholera
    • Cholera is highly suggested by severe profuse watery diarrhea & dehydration
    • Other clinical features: Very abrupt onset of acute diarrhea with rapid progression to severe dehydration, the presence of muscle cramps but no fever or abdominal pain
    • Stools are usually greenish-yellow clear watery with little food residue
    • Dark-field microscopy (DFM) & stool culture should be done in all cases
    • Microscopic exam of stool may also reveal shooting bacteria, but not white blood cell (WBC) or red blood cell (RBC)
    • If cholera is confirmed in nonendemic areas, it should be reported to health authorities
    • Any case of watery diarrhea in endemic areas during outbreaks or seasonal epidemics should be treated as cholera & stool cultures should be done in all cases to confirm

Bloody Diarrhea 

  • Shigella spCampylobacter jejuni
    • Shigella dysenteriae Shigella flexneri may cause a more severe disease with high fever
    • Shigella boydii Shigella sonnei cause a milder disease
  • Salmonella enteritidis, Yersinia enterocolitica, C difficile, Balantidium coli, Plesiomonas, enterohemorrhagic E coli (EHEC) & enteroinvasive E coli (EIEC) can produce bloody diarrhea

Signs and Symptoms

Associated Symptoms  

  • Frequency & intensity of nausea & vomiting, abdominal pain, cramps, myalgia, headache, altered sensorium

Symptoms of Volume Depletion

  • Thirst
  • Tachycardia
  • Orthostasis
  • Decreased urination
  • Decrease in skin turgor
  • Lethargy

Bloody Diarrhea

  • Patients often have fever that may last >2 days & might be high (>38.5°C)
  • May initially suffer with watery diarrhea that rapidly changes to bloody diarrhea & dysentery
  • Red blood cell (RBC) & white blood cell (WBC) are found on microscopic exam of the stools
  • Mild dehydration
  • Dysentery
    • Suggested by frequent passage (10-30x/day) of small volume stools that consist of blood, mucus & pus
    • Patient usually suffers abdominal cramps & tenesmus

Risk Factors

  • Travel to developing/underdeveloped areas
  • Daycare attendance
  • Ingestion of unsafe foods (eg unpasteurized dairy products, undercooked meats, seafood)
  • Swimming/drinking untreated fresh water
  • Poor personal & public hygiene (eg seldom practice of hand washing)
  • Visit to farm or contact with pets with diarrhea
  • Knowledge of other ill persons
  • Recent or regular medications (eg antibiotics)
  • Underlying medical conditions (eg AIDS, immunosuppressants)
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