What is the workup and treatment for a patient presenting with diarrhea?

Workup and Treatment for Diarrhea

The initial management of diarrhea should focus on rehydration therapy, with oral rehydration solution (ORS) for mild to moderate dehydration and intravenous fluids for severe dehydration, followed by targeted treatment based on the underlying cause. 1, 2

Initial Assessment

• Evaluate for dehydration severity:

  • Mild: Thirst, dry mucous membranes, reduced urine output
  • Moderate: Tachycardia, reduced skin turgor, sunken eyes
  • Severe: Altered mental status, hypotension, oliguria, tachycardia, delayed capillary refill

• Assess for inflammatory diarrhea indicators:

  • Bloody stools
  • Fever
  • Severe abdominal pain
  • Tenesmus (painful straining)

• Risk factors to identify:

  • Recent antibiotic use (C. difficile risk)
  • Travel history
  • Immunocompromised status
  • Foodborne illness exposure
  • Medication use (chemotherapy, immunotherapy)

Rehydration

Mild to Moderate Dehydration

• Oral rehydration therapy with solutions containing 45-75 mEq/L sodium 2, 3
• Continue feeding during episodes of diarrhea to maintain nutritional status
• Avoid high simple sugar and fatty foods

Severe Dehydration

• Initial fluid bolus of 20 mL/kg 1
• Continue rapid fluid replacement until clinical signs of hypovolaemia improve
• Target urine output >0.5 mL/kg/h 1
• Transition to oral rehydration when possible

Laboratory Workup

Reserve diagnostic testing for:

• Severe dehydration
• Persistent fever
• Bloody diarrhea
• Immunocompromised patients
• Suspected outbreaks
• Prolonged symptoms (>7 days)

When indicated, consider:

• Complete blood count
• Basic metabolic panel
• Stool studies:
  • Routine culture (Salmonella, Shigella, Campylobacter)
  • C. difficile toxin assay if recent antibiotic use
  • Ova and parasite examination if travel history or persistent symptoms
  • Fecal leukocytes or lactoferrin/calprotectin for inflammatory diarrhea

Treatment Approaches

Symptomatic Treatment

• Antimotility agents:

  • Loperamide: Initial dose 4 mg followed by 2 mg after each loose stool (maximum 16 mg/day) 1, 4
  • Contraindications: Bloody diarrhea, fever, children <2 years, suspected inflammatory diarrhea 4, 2
  • Caution: Monitor for cardiac adverse reactions, especially with higher doses or in patients taking CYP3A4 or CYP2C8 inhibitors 4

• Other supportive measures:

  • Avoid spicy foods, coffee, alcohol, and milk products during acute episodes 1
  • Consider probiotics to shorten duration of illness 2

Specific Treatments Based on Etiology

1. Viral gastroenteritis:

   • Supportive care with hydration
   • Self-limiting, typically resolves in 2-3 days

2. Bacterial pathogens:

   • Shigella: Azithromycin or TMP-SMX (if susceptible) 5
   • Campylobacter: Azithromycin or erythromycin 5
   • ETEC: TMP-SMX (if susceptible) or azithromycin 5

3. C. difficile infection:

   • Oral vancomycin 125 mg four times daily 6
   • Monitor for adverse effects: nausea (17%), abdominal pain (15%), hypokalemia (13%) 6
   • Discontinue causative antibiotics if possible

4. Chemotherapy-induced diarrhea:

   • Loperamide as first-line therapy 1
   • Consider octreotide 100-150 μg SC/IV three times daily for refractory cases 1
   • Uridine triacetate for early-onset severe toxicity within 96 hours of 5-FU/capecitabine 1

5. Immunotherapy-induced diarrhea:

   • Grade 1: Symptomatic treatment with ORS and loperamide 1
   • Grade 2: Add budesonide 9 mg daily if no bloody diarrhea 1
   • Grade 3-4: Prednisone 1-2 mg/kg/day; consider infliximab for persistent symptoms 1

Prevention

• Proper hand hygiene, especially after toilet use and before food preparation
• Safe food handling practices
• Access to clean water
• Appropriate vaccination (e.g., rotavirus for infants)

Special Considerations

• Elderly patients: Higher risk for dehydration and complications; monitor more closely
• Immunocompromised patients: Lower threshold for diagnostic testing and antibiotic therapy
• Patients on multiple medications: Review for potential drug interactions, especially with loperamide

By following this systematic approach to diarrhea management, focusing first on rehydration and then addressing the underlying cause, most cases can be effectively managed with good outcomes.