Differentials
Bacterial gastroenteritis
SIGNS / SYMPTOMS
High fever, bloody diarrhea, or severe diarrhea suggests bacterial infection.
INVESTIGATIONS
Stool microscopy and culture are differentiating tests. Evidence of inflammation (fecal leukocytes or a positive lactoferrin immunoassay) may be present. Culture may grow enteropathogenic bacteria, such as Campylobacter jejuni, Salmonella species, enteropathogenic Escherichia coli, Shigella, Yersinia enterocolitica, Shiga toxin-producing E coli, or Vibrio cholerae.
Protozoal infections
SIGNS / SYMPTOMS
May be suspected if a patient has recently traveled to countries where protozoal infections are endemic (e.g., Mexico, India, South America, many parts of the US). Signs and symptoms vary based on the parasite.
Amebic dysentery presents with bloody diarrhea with excessive mucus and abdominal pain.
Giardiasis can present with bloating and prolonged diarrhea.
Parasitic infections should always be ruled out in immunocompromised patients.
INVESTIGATIONS
Traditionally, stool microscopy is used to identify Giardia lamblia, Entamoeba histolytica, cryptosporidium, or other parasites. Stool antigen testing or serology can also be used.
Helminthic infections
SIGNS / SYMPTOMS
These infections are common in immunocompromised patients and in people who have traveled from endemic areas.
INVESTIGATIONS
Stool microscopy can identify the worm.
Clostridioides difficile colitis
SIGNS / SYMPTOMS
Recent antibiotic use is a risk factor.
Some patients can progress very rapidly to serious toxic megacolon, so early detection and presumptive treatment may be warranted.
INVESTIGATIONS
Stool test for C difficile toxin would be positive.
Food poisoning
SIGNS / SYMPTOMS
Usually suspected if multiple people develop symptoms after eating the same contaminated food or drink. Symptoms can vary from nausea, vomiting, abdominal pain, and/or diarrhea which start suddenly a few hours to 2 days after eating the contaminated food.
INVESTIGATIONS
Stool cultures are low-yield as most of these diseases are caused by toxins. Toxin testing may be available for epidemiologic purposes.
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