Approach to Acute Diarrhea

Jun 19, 2024

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Lecture Notes: Approach to Acute Diarrhea

Introduction

  • Focus on adult and teen patients, not younger pediatric groups.
  • No uniform definition for diarrhea; can be based on:
    • Number of bowel movements within 24 hours.
    • Stool volume within 24 hours.
    • Subjective consistency.
  • Patient's self-report is typically taken at face value.
  • Acute diarrhea is generally considered if present for less than two weeks.

Diagnostic Framework

  • Two major categories for diarrhea:
    1. Non-Inflammatory Diarrhea
      • Watery stool.
      • Abdominal pain, fever, and sepsis uncommon.
    2. Inflammatory Diarrhea
      • Stool with gross blood or mucus.
      • Abdominal pain and fever common.
      • Also known as dysentery but avoid using the term without microbial diagnosis.

Etiologies of Non-Inflammatory Diarrhea

  • Viral Causes: Norovirus, Rotavirus, Enteric adenoviruses, Cytomegalovirus (immunocompromised patients), SARS-CoV-2.
  • Bacterial Causes:
    • C. difficile (post-antibiotic use)
    • High-risk antibiotics: Clindamycin, Fluoroquinolones, Broad-spectrum penicillins, Third-generation cephalosporins.
    • E. coli (ETEC, EPEC, EAEC subsets).
    • Listeria, Vibrio cholerae, Vibrio parahaemolyticus.
  • Toxin Ingestion: Staph aureus, B. cereus.
  • Protozoal Causes: Giardia, Cryptosporidium.
  • Non-Infectious Causes: Medications (antibiotics, anti-neoplastic drugs, colchicine, NSAIDs, magnesium antacids, PPIs, H2 blockers, SSRIs), psychosocial stressors.

Etiologies of Inflammatory Diarrhea

  • Bacterial Causes: EIEC, EHEC (includes O157:H7 subtype), Campylobacter, Shigella, Yersinia, non-typhoidal Salmonella.
  • Protozoal Causes: Entamoeba histolytica.
  • Non-Infectious Causes: Ischemic colitis.
  • Chronic diarrhea causes presenting acutely: e.g., inflammatory bowel disease.

Common Causes and Special Considerations

  • Most Common Causes: Norovirus, various E. coli subtypes, Campylobacter.
  • Developing World Pathogens: Vibrio cholerae, Shigella, Entamoeba.
  • Traveler's Diarrhea:
    • Risk factors: Travel to resource-limited areas, warm/wet seasons, street vendor food, salads, raw vegetables.
    • Common etiologies: ETEC, Campylobacter, Norovirus.

Patient Assessment

  • History:
    • Duration (acute vs. chronic).
    • Stool characteristics (watery vs. bloody/mucus).
    • Associated symptoms: fever, nausea, vomiting, abdominal pain, tenesmus.
    • Past medical history: immunocompromise, recent C. diff infection.
    • Medication history: particularly antibiotics.
    • Dietary and environmental exposure.
    • Travel history.
  • Physical Exam:
    • Vitals and orthostatics (volume status).
    • Abdominal exam.
  • Diagnostic Tests:
    • Stool culture, multiplex PCR panel, C. diff testing, microscopy for Entamoeba.
    • CBC and chemistry panel for severe cases.

Diagnostic Flowchart

  1. Risk of C. Diff? - Recent antibiotic use or C. diff history.
    • If yes: Test for C. diff.
    • If positive: Begin treatment.
  2. Evidence of Inflammatory Diarrhea or Severe Disease?
    • Severe abdominal pain, bloody stool, fever, hypovolemia, risk factors for severe outcome, public health concerns.
    • If none: Symptomatic treatment, monitor.
  3. Persistent Symptoms After Several Days?
    • Stool culture, multiplex panel, Shiga toxin test, Entamoeba test.
    • Treatment based on diagnosis.
    • Monitor if no diagnosis is made.

Key Takeaways

  • Acute diarrhea: Non-inflammatory (watery, minimal systemic symptoms) vs. Inflammatory (blood/mucus in stool, fever).
  • Most common etiologies: Norovirus, Campylobacter, E. coli.
  • C. diff important in hospitalized patients.
  • Testing reserved for inflammatory diarrhea, severe cases, chronic disease, suspected outbreaks.

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