What can be helpful in determining whether the source of diarrhea is from the small or large bowel?

Updated: Jan 31, 2020
  • Author: Stefano Guandalini, MD; Chief Editor: Carmen Cuffari, MD  more...
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Answer

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

Table 1. Stool Characteristics and Determining Their Source (Open Table in a new window)

Stool Characteristics

Small Bowel

Large Bowel

Appearance

Watery

Mucoid and/or bloody

Volume

Large

Small

Frequency

Increased

Highly increased

Blood

Possibly positive but never gross blood

Commonly grossly bloody

pH

Possibly < 5.5

>5.5

Reducing substances

Possibly positive

Negative

WBCs

< 5/high power field

Commonly >10/high power field

Serum WBCs

Normal

Possible leukocytosis, bandemia

Organisms

Viral

  • Rotavirus

  • Adenovirus

  • Calicivirus

  • Astrovirus

  • Norovirus

Invasive bacteria

  • Escherichia Coli (enteroinvasive, enterohemorrhagic)

  • Shigella species

  • Salmonella species

  • Campylobacter species

  • Yersinia species

  • Aeromonas species

  • Plesiomonas species

Enterotoxigenic bacteria

  • E coli

  • Klebsiella

  • Clostridium perfringens

  • Cholera species

  • Vibrio species

Toxic bacteria

  • Clostridium difficile

Parasites

  • Giardia species

  • Cryptosporidium species

Parasites

  • Entamoeba organisms


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