How is diarrhea defined and stool assessed in the evaluation of bacterial gastroenteritis?

Updated: Jul 17, 2018
  • Author: Jennifer Lynn Bonheur, MD; Chief Editor: BS Anand, MD  more...
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Answer

Diarrhea is defined as daily stools with a mass greater than 15g/kg for children younger than 2 years and greater than 200 g for children 2 years or older. Adult stool patterns vary from 1 stool every 3 days to 3 stools per day; therefore, consider individual stool patterns.

Consistency, color, volume, and frequency are very important in determining whether the stool source is from the small or large bowel. Table 1, below, outlines these characteristics and demonstrates that an index of suspicion can be generated easily for a specific set of organisms.

Table 1. Stool Characteristics and Sources (Open Table in a new window)

Stool Characteristics

Small Bowel

Large Bowel

Appearance

Watery

Mucus and/or blood

Volume

Large

Small

Frequency

Increased

Increased

Blood

Possibly heme-positive but never gross blood

Possibly grossly bloody

pH

Possibly < 5.5

>5.5

Reducing substances

Possibly positive

Negative

White blood cell (WBC) count

< 5/high-power field (HPF)

Possibly >10/HPF

Serum WBC count

Normal

Possible leukocytosis, bandemia

Organisms

Preformed toxins:

Bacillus species, Staphylococcus aureus

Invasive bacteria:

E coli and Shigella, Salmonella, Campylobacter, Yersinia, Aeromonas, and Plesiomonas species

Toxic bacteria:

E coli, cholera, C perfringens, Vibrio species, Listeria monocytogenes

Toxic bacteria:

C difficile

Other causes:

rotavirus, adenovirus, calicivirus, astrovirus, Norwalk virus, and Giardia and Cryptosporidium species

Other causes:

Entamoeba species


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