What is the differential diagnosis for acute explosive watery diarrhea?

Differential Diagnosis of Acute Explosive Watery Diarrhea

The differential diagnosis for explosive watery diarrhea is primarily divided into noninflammatory (secretory) and inflammatory etiologies, with viral pathogens (especially norovirus) and enterotoxigenic bacteria being the most common causes in immunocompetent adults, while bacterial pathogens predominate when fever, blood, or severe systemic symptoms are present. 1

Noninflammatory (Secretory) Causes

These pathogens cause profuse watery diarrhea without fever or blood by disrupting enterocyte function:

Viral Pathogens (Most Common Overall)

• Norovirus: The leading cause of acute gastroenteritis in adults, causing 58% of foodborne illness with symptoms lasting 2-3 days 1, 2
• Rotavirus: Most common in children <5 years (though vaccine has reduced incidence), causing watery diarrhea for 3-8 days after 2-day incubation 1, 2
• Adenovirus (types 40/41): Longer duration than other viruses (≥1 week), incubation 3-10 days 2
• Astrovirus: Brief illness lasting 1-4 days after 24-36 hour incubation 2
• Sapovirus: Average 4-day illness course 2

Enterotoxin-Producing Bacteria

• Enterotoxigenic E. coli (ETEC): Leading bacterial cause in travelers' diarrhea, particularly common in lower-income countries 3, 4, 5
• Vibrio cholerae: Classic "rice water" explosive diarrhea, though rare in developed countries 6
• Vibrio parahaemolyticus: Associated with seafood consumption 5

Inflammatory/Invasive Causes

These present with fever, abdominal pain, and often bloody diarrhea:

Bacterial Pathogens

• Salmonella enterica: Accounts for 35% of hospitalizations and 28% of deaths from bacterial gastroenteritis; most common serotype is S. enteritidis 1, 5
• Campylobacter jejuni: Second most common bacterial pathogen (28% in children <5 years), causes severe abdominal pain that can mimic appendicitis 1, 5
• Shigella: Accounts for 21% of bacterial infections in young children, causes dysentery with fever 1, 4
• Yersinia enterocolitica: Presents with prolonged fever (often 2+ weeks) and pseudoappendicitis syndrome, associated with pork consumption 1, 7
• Shiga toxin-producing E. coli (STEC): Including O157:H7, causes bloody diarrhea with risk of hemolytic uremic syndrome 1, 4
• Enteroaggregative E. coli (EAEC): Cytotoxin-producing, causes inflammatory diarrhea 6, 5

Cytotoxin-Producing Organisms

• Clostridioides difficile: Most common healthcare-associated infectious diarrhea, must be considered with antibiotic use within 8-12 weeks 1, 7

Parasitic Causes (Especially in Persistent Diarrhea >7-14 Days)

• Giardia lamblia: Common in travelers, causes prolonged watery diarrhea 3, 5
• Cryptosporidium parvum: Particularly severe in immunocompromised patients 3, 5
• Entamoeba histolytica: Causes invasive colitis with bloody diarrhea 3, 6

Critical Clinical Context for Narrowing the Differential

High-Risk Features Requiring Immediate Evaluation

• Fever ≥38.5°C with systemic toxicity: Consider enteric fever (typhoid/paratyphoid), especially with travel to endemic areas; obtain blood cultures immediately 7
• Bloody diarrhea: Suggests Shigella, Campylobacter, STEC, Salmonella, or E. histolytica 1, 7
• Prolonged fever (≥2 weeks) before diarrhea onset: Strongly suggests enteric fever or Yersinia 7
• Severe abdominal pain mimicking appendicitis: Consider Campylobacter or Yersinia 1, 7

Epidemiologic Clues

• Recent travel to endemic areas: ETEC most common, but consider enteric fever, Campylobacter, Shigella 7, 3
• Antibiotic use within 8-12 weeks: Test for C. difficile toxin 1, 7
• Seafood consumption: Vibrio species, particularly V. parahaemolyticus 5
• Undercooked pork/chitterlings: Yersinia enterocolitica 1
• Immunocompromised status: Broader differential including Mycobacterium avium complex, cytomegalovirus, microsporidia, Cystoisospora 7

Age-Specific Considerations

• Children <5 years: Norovirus now most common (post-rotavirus vaccine era), followed by Salmonella (42%), Campylobacter (28%), Shigella (21%) 1
• Adults >65 years: Higher rates of hospitalization and death; increased risk of invasive Salmonella and Vibrio vulnificus (especially with liver disease) 1

Diagnostic Algorithm Based on Clinical Presentation

For acute watery diarrhea without fever/blood in immunocompetent patients: Presume viral etiology; no testing needed unless symptoms persist >7 days or patient is high-risk 1

For diarrhea with fever, blood, or severe symptoms: Obtain stool culture for Salmonella, Shigella, Campylobacter, Yersinia, and test for Shiga toxin; consider C. difficile if recent antibiotics 1, 7

For persistent diarrhea >7-14 days: Add parasitic examination or antigen testing for Giardia, Cryptosporidium, Cyclospora, Entamoeba 7

For fever ≥2 weeks with subsequent diarrhea: Obtain blood cultures and stool cultures; strongly consider enteric fever 7

Critical Management Pitfalls to Avoid

• Never use antimotility agents (loperamide) when fever or bloody diarrhea is present: Risk of toxic megacolon and worsening outcomes 7
• Avoid antibiotics in suspected STEC: May increase risk of hemolytic uremic syndrome 7
• Do not delay empiric antibiotics in suspected enteric fever with sepsis: Start broad-spectrum therapy after cultures, then narrow based on susceptibilities 7
• Fluoroquinolones should not be used empirically for Campylobacter: Resistance exceeds 90% in Southeast Asia; azithromycin is preferred 8
• Immunocompromised patients require treatment even for mild symptoms: Higher risk of bacteremia and systemic complications 1, 8