Differentials
Salmonella gastroenteritis
SIGNS / SYMPTOMS
Symptoms not significantly different. Campylobacter infection often presents with more severe abdominal pain.
Bloody diarrhea is less common in non-enteric Salmonella infections.
INVESTIGATIONS
Stool culture: Salmonella organism.
Shigella gastroenteritis
SIGNS / SYMPTOMS
Symptoms not significantly different. Campylobacter infection often presents with more severe abdominal pain.
INVESTIGATIONS
Stool culture: Shigella organism.
Yersinia gastroenteritis
SIGNS / SYMPTOMS
Symptoms not significantly different. Campylobacter infection often presents with more severe abdominal pain.
Bloody diarrhea is less common with Yersinia infections.
INVESTIGATIONS
Stool culture: Yersinia organism.
Escherichia coli gastroenteritis
SIGNS / SYMPTOMS
Symptoms not significantly different. Campylobacter infection often presents with more severe abdominal pain.
INVESTIGATIONS
Stool culture: E coli organism.
Gastroenteritis caused by Vibrio species
SIGNS / SYMPTOMS
Symptoms not significantly different. Campylobacter infection often presents with more severe abdominal pain.
Bloody diarrhea is less common with Vibrio infections.
INVESTIGATIONS
Stool culture: Vibrio organism.
Listeria gastroenteritis
SIGNS / SYMPTOMS
Symptoms not significantly different. Campylobacter infection often presents with more severe abdominal pain.
INVESTIGATIONS
Stool culture: Listeria organism.
Cholera
SIGNS / SYMPTOMS
Symptoms not significantly different. Campylobacter infection often presents with more severe abdominal pain. Severe cholera is characterized by “rice water stool” (watery stool and mucous) and is often painless.
INVESTIGATIONS
Complete blood count: may have elevated hematocrit or neutrophil count.
Serum lactate: elevated.
Arterial blood gas: metabolic acidosis.
Darkfield/phase-contrast microscopy of stool: large quantity of curved bacilli.
Rapid dipstick testing of stool: positive.
Viral gastroenteritis in adults
SIGNS / SYMPTOMS
Viral gastroenteritis is often associated with upper gastrointestinal symptoms, including nausea and vomiting. However, it can present with diarrhea alone.
INVESTIGATIONS
Stool rapid antigen testing: may be positive for rotavirus or calicivirus.
Stool reverse transcriptase PCR (RT-PCR) or multiple-x PCR: may detect rotavirus, norovirus, astrovirus, or adenovirus.
Viral gastroenteritis in children
SIGNS / SYMPTOMS
Viral gastroenteritis is often associated with upper gastrointestinal symptoms, including nausea and vomiting. However, it can present with diarrhea alone.
INVESTIGATIONS
Serum electrolytes, urea, creatinine: usually normal, although can be abnormal if severe dehydration is present.
Complete blood count: usually normal; elevated white blood cell (WBC) count and granulocytes if sepsis is present.
Stool microscopy: usually normal; presence of WBCs often suggests infection with an invasive cytotoxin-producing organism such asSalmonella,Shigella, orYersinia enterocolitica.
Stool culture: negative.
Crohn disease
SIGNS / SYMPTOMS
Crohn disease (CD) is a chronic condition. It produces diffuse abdominal pain, which may be accompanied by mucus or blood in the stool.
Nonbloody intermittent diarrhea is a common symptom in CD.
Up to 20% to 30% of patients with CD have perianal lesions, including skin tags, fistulae, abscesses, scarring, or sinuses.
INVESTIGATIONS
Stool culture: negative.
Histology: crypt abscess, granuloma.
Upper gastrointestinal and small bowel series: luminal narrowing and strictures.
CT/MRI abdomen: skip lesions, bowel wall thickening, surrounding inflammation, abscess, fistulae.
Colonoscopy: ulcers, hyperemia, edema, cobblestoning, skip lesions, luminal narrowing, or strictures.
Ulcerative colitis
SIGNS / SYMPTOMS
Ulcerative colitis is a chronic condition. Abdominal pain severity and location depend on disease severity and extent. It can range from mild crampy pain associated with tenesmus to severe pain with either severe or complicated colitis (i.e., toxic megacolon, perforation).
Diarrhea is usually bloody; severity and frequency are related to disease severity and extent.
Patients have gross or occult blood on digital rectal exam.
Bleeding severity and frequency is related to disease severity and extent.
INVESTIGATIONS
Stool culture: negative.
Histology: continuous from rectum extending proximally without skip lesions, mucin depletion, basal plasmacytosis, diffuse mucosal atrophy, absence of granulomata, and anal sparing.
Colonoscopy: rectal involvement, continuous uniform involvement with clear transition point to normal mucosa proximally, loss of vascular marking, diffuse erythema, mucosal granularity, fistulas (rarely seen), normal terminal ileum (or mild "backwash" ileitis in pancolitis).
Acute appendicitis
SIGNS / SYMPTOMS
Location and character of abdominal pain secondary to appendicitis may be similar to that of Campylobacter infection. Pain is usually generalized but can often be localized to the right lower quadrant.
INVESTIGATIONS
Ultrasound may show appendix with outer diameter >6 mm, no compressibility, lack of peristalsis, or periappendiceal fluid.
CT scan showing inflammation of the appendix.
Clostridium difficile-associated diarrhea
SIGNS / SYMPTOMS
Most often associated with a history of recent antibiotic use.
INVESTIGATIONS
A positive test for Clostridium difficile toxin is confirmatory in the correct clinical scenario.
Colonoscopy shows pseudomembranes on top of normal mucosa.
Toxin-mediated food poisoning (Staphylococcus aureus, Clostridium perfringens, Bacillus cereus )
SIGNS / SYMPTOMS
Vomiting is more likely and the incubation time is shorter (4-24 hours) in toxin-mediated food poisoning.
INVESTIGATIONS
Detection of organism in stool and food source.
Amebiasis
SIGNS / SYMPTOMS
No fever or systemic features unless extraintestinal amebiasis.
Weight loss if ongoing.
Right upper quadrant abdominal pain if related liver abscess.
INVESTIGATIONS
Stool microscopy for cysts and parasites: positive for Entamoeba.
Cryptosporidiosis
SIGNS / SYMPTOMS
Diarrhea is found in virtually all cases and may continue for up to 3 weeks or sometimes longer; may also have a relapsing and remitting nature. Stools tend to be watery and voluminous. Often associated with an immunocompromised state. In immunocompromised people, the diarrhea may be chronic and intractable.
INVESTIGATIONS
Stool microscopy for cysts and parasites: positive for Cryptosporidium oocysts.
Cryptosporidium stool antigen: positive.
Giardiasis
SIGNS / SYMPTOMS
Weight loss if chronic.
Frequent foul-smelling flatulence with distinctive odor of hydrogen sulfide.
INVESTIGATIONS
Stool microscopy for cysts and parasites: positive for Giardia cysts and trophozoites.
Giardia stool antigen: positive.
Leishmaniasis
SIGNS / SYMPTOMS
Weight loss in visceral leishmaniasis. Associated hepatosplenomegaly.
INVESTIGATIONS
Spleen aspirate, bone marrow aspirate, or lymph node fluid; amastigote form of Leishmania species in macrophages or monocytes.
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