What is the workup for a patient presenting with diarrhea for possible gastroenteritis?

Workup for Diarrhea in Suspected Gastroenteritis

The workup for suspected gastroenteritis should begin with assessment of severity, hydration status, and specific symptoms to determine the need for diagnostic testing and appropriate management.

Initial Assessment

History

• Onset and duration of diarrhea
• Number and composition of stools (watery, bloody, mucus)
• Presence of nocturnal diarrhea
• Associated symptoms:
  • Fever
  • Abdominal pain/cramping
  • Vomiting
  • Dizziness or weakness (signs of dehydration)
• Medication profile to identify diarrheogenic agents
• Dietary profile to identify diarrhea-enhancing foods 1
• Recent travel history
• Exposure to others with similar symptoms

Physical Examination

• Vital signs (especially for fever, tachycardia, orthostatic hypotension)
• Hydration status assessment (skin turgor, mucous membranes, capillary refill)
• Abdominal examination (tenderness, distention, peritoneal signs)

Diagnostic Testing

For Mild Cases (Grade 1: <4 stools/day above baseline, no colitis symptoms)

• Conservative management without immediate testing
• If symptoms persist >48 hours:
  • Stool testing for infectious causes 1
  • Consider fecal lactoferrin to identify inflammatory diarrhea 1

For Moderate to Severe Cases (Grade 2-4: ≥4 stools/day above baseline or colitis symptoms)

• Complete blood count (CBC)
• Comprehensive metabolic panel (CMP)
• C-reactive protein (CRP) and ESR
• Stool studies:
  • Culture for bacterial pathogens (Salmonella, Shigella, Campylobacter)
  • Clostridium difficile testing (especially with recent antibiotic exposure)
  • Ova and parasites
  • Viral studies (particularly norovirus)
  • Fecal lactoferrin and calprotectin 1

Additional Testing Based on Clinical Presentation

• Imaging (CT scan of abdomen/pelvis) for:

  • Severe abdominal pain
  • Suspected complications (perforation, obstruction)
  • Bloody diarrhea with systemic symptoms 1

• Endoscopy with biopsy if:

  • Positive inflammatory markers (lactoferrin/calprotectin)
  • Bloody diarrhea
  • Symptoms persisting >7 days despite treatment 1

Management Algorithm

Mild Cases (Grade 1)

1. Hydration: 8-10 large glasses of clear liquids daily 1, 2
2. Dietary modifications:
   • BRAT diet (Bananas, Rice, Applesauce, Toast) 2
   • Avoid lactose-containing products, alcohol, high-osmolar supplements 1, 2
   • Frequent small meals rather than large ones 1
3. Consider loperamide (4 mg initially, then 2 mg after each loose stool, max 16 mg/day) if no fever or bloody stools 2
4. Monitor for worsening symptoms

Moderate Cases (Grade 2)

1. All measures for mild cases
2. Complete diagnostic workup as outlined above
3. Consider holding medications that may contribute to diarrhea
4. Loperamide if no bloody stools or fever (discontinue after 12-hour diarrhea-free interval) 1, 2
5. Consider oral rehydration solutions for fluid replacement 2, 3

Severe Cases (Grade 3-4)

1. Consider hospitalization for:
   • Severe dehydration
   • Hemodynamic instability
   • Fever with bloody diarrhea
   • Significant abdominal pain 1
2. Intravenous fluid rehydration
3. Complete diagnostic workup including imaging and possible endoscopy
4. Targeted antimicrobial therapy based on identified pathogens 4
5. Avoid antimotility agents in bloody diarrhea 3

Special Considerations

Immunocompromised Patients

• Lower threshold for diagnostic testing and antimicrobial therapy 4
• Consider broader testing for opportunistic pathogens
• More aggressive hydration and monitoring

Travelers' Diarrhea

• Stool testing indicated for:
  • Fever
  • Bloody diarrhea
  • Symptoms >5 days
  • Severe clinical course 4
• Consider empiric antimicrobial therapy (azithromycin or ciprofloxacin) for moderate to severe cases 4

Suspected Immune Checkpoint Inhibitor-Related Colitis

• Assess for grade of diarrhea/colitis
• Consider holding immunotherapy
• For grade ≥2: stool testing, fecal inflammatory markers, and consider endoscopy
• Corticosteroids for confirmed immune-related colitis 1

When to Refer or Hospitalize

• Severe dehydration or hemodynamic instability
• Persistent fever
• Bloody diarrhea with systemic symptoms
• Immunocompromised status
• Failure to improve with outpatient management
• Severe abdominal pain or peritoneal signs 5, 3

The workup for diarrhea in suspected gastroenteritis should be tailored to the severity of symptoms, with most mild cases requiring only supportive care and more severe cases warranting comprehensive diagnostic evaluation and targeted therapy.