How to manage a patient with diarrhea?

Management of Loose Bowel Movements (Diarrhea)

The management of diarrhea hinges on rapid assessment of hydration status and severity, followed by oral rehydration solution (ORS) as first-line therapy for mild-to-moderate cases, with loperamide reserved for uncomplicated diarrhea in adults and children ≥2 years, while avoiding antimotility agents entirely in children under 18 years. 1, 2, 3

Initial Assessment and Risk Stratification

Immediately classify the patient by dehydration severity and complicating features:

• Mild dehydration (3-5% fluid deficit): Increased thirst, slightly dry mucous membranes 2
• Moderate dehydration (6-9% fluid deficit): Loss of skin turgor, dry mucous membranes, decreased urine output, rapid deep breathing, prolonged skin retraction time 1, 2
• Severe dehydration (≥10% fluid deficit): Severe lethargy or altered consciousness, prolonged skin tenting, decreased perfusion—this is a medical emergency requiring immediate IV rehydration 2

Identify "complicated" versus "uncomplicated" diarrhea:

• Uncomplicated: Grade 1-2 diarrhea without fever, blood in stool, severe cramping, vomiting, or signs of sepsis 4
• Complicated: Any diarrhea with fever, bloody stools, severe dehydration, neutropenia, sepsis, altered mental status, or diminished performance status 4

Treatment Protocol for Uncomplicated Diarrhea

For mild-to-moderate uncomplicated diarrhea, initiate the following simultaneously:

• Oral rehydration solution (ORS): Use reduced osmolarity ORS (50-90 mEq/L sodium) as first-line therapy 1, 2, 5

  • Mild dehydration: 50 mL/kg over 2-4 hours 2
  • Moderate dehydration: 100 mL/kg over 2-4 hours 1, 2
  • Acceptable commercial products: Pedialyte, CeraLyte, Enfalyte/Infalyte 2, 5

• Dietary modifications: Eliminate lactose-containing products and high-osmolar supplements 4

• Loperamide (adults and children ≥2 years only):

  • Initial dose: 4 mg, then 2 mg after each unformed stool (maximum 16 mg/day) 4, 3
  • Pediatric dosing (2-12 years): Age-specific dosing required—see detailed schedule below 3
  • CRITICAL WARNING: Loperamide is contraindicated in children <2 years due to risk of respiratory depression and cardiac adverse reactions 3

• Skin protection: Use barriers to prevent irritation from fecal material, especially in incontinent patients 4

Pediatric-Specific Loperamide Dosing (Ages 2-12 Years)

First day dosing: 3

• 2-5 years (13-20 kg): 1 mg three times daily (3 mg total)
• 6-8 years (20-30 kg): 2 mg twice daily (4 mg total)
• 8-12 years (>30 kg): 2 mg three times daily (6 mg total)

Subsequent days: 1 mg/10 kg body weight only after loose stool, not exceeding first-day maximum 3

Treatment Protocol for Complicated Diarrhea

Hospitalize immediately and initiate aggressive management: 4

• Continue loperamide at standard dosing (4 mg initially, then 2 mg after each loose stool, maximum 16 mg/day) 4

• IV fluids and electrolytes: Use isotonic solutions (lactated Ringer's or normal saline) for severe dehydration or shock 1, 2

• Stool evaluation: Obtain blood and stool cultures 4

• Consider empiric antibiotics:

  • Fluoroquinolones for suspected bacterial etiology 4
  • Metronidazole if Clostridioides difficile suspected 4, 6

• Consider octreotide for refractory cases: 100-150 μg subcutaneously three times daily, or IV 25-50 μg three times daily, escalating to 500 μg three times daily if needed 4

Ongoing Fluid Loss Replacement

Replace losses during both rehydration and maintenance phases: 1

• Per diarrheal stool: 10 mL/kg ORS 1
• Per vomiting episode: 2 mL/kg ORS 1
• Infants <10 kg: 60-120 mL ORS per episode, up to ~500 mL/day 1

Nutritional Management

Resume feeding immediately upon rehydration completion—do NOT "rest the bowel": 2, 5

• Breastfed infants: Continue nursing on demand throughout illness 1, 2, 5
• Bottle-fed infants: Use full-strength, lactose-free, or lactose-reduced formulas immediately after rehydration 1, 2
• Children >4-6 months and adults: Resume age-appropriate normal diet as soon as appetite returns 1, 2, 5

Critical Pitfalls to Avoid

Never use antimotility agents in children <18 years with acute diarrhea—this is explicitly contraindicated: 5, 3

Avoid loperamide in the following high-risk situations: 3

• Patients taking QT-prolonging drugs: Class IA/III antiarrhythmics, antipsychotics, certain antibiotics (moxifloxacin), methadone 3
• Patients with cardiac risk factors: Congenital long QT syndrome, history of arrhythmias, electrolyte abnormalities, elderly patients 3
• Patients taking CYP3A4/CYP2C8 inhibitors or P-glycoprotein inhibitors: These dramatically increase loperamide exposure (up to 12.6-fold with combined itraconazole and gemfibrozil) 3

Do not exceed recommended loperamide dosages—higher doses cause QT prolongation, Torsades de Pointes, cardiac arrest, and death: 3

Do not delay rehydration while awaiting diagnostic results: 5

Do not give empiric antibiotics for uncomplicated watery diarrhea without recent international travel—this promotes resistance without benefit: 5, 7

When to Switch to IV Therapy

Transition from ORS to IV fluids if: 1, 2, 5

• Progression to severe dehydration or shock
• Altered mental status
• Persistent vomiting preventing oral intake
• Paralytic ileus
• ORS therapy failure after appropriate trial
• Patient cannot tolerate oral/nasogastric intake

Use 20 mL/kg IV boluses of lactated Ringer's or normal saline until pulse, perfusion, and mental status normalize, then transition back to ORS for remaining deficit replacement: 2

Reassessment and Monitoring

Reassess hydration status after 2-4 hours of ORS therapy: 1, 2

• If still dehydrated, reestimate fluid deficit and restart rehydration protocol
• Monitor weight changes, stool frequency/consistency, skin turgor, mucous membrane moisture, mental status 1, 2

Discontinue loperamide and contact healthcare provider if: 3

• No clinical improvement within 48 hours
• Blood in stools develops
• Fever or abdominal distention occurs
• Constipation, abdominal distention, or ileus develops 3

Special Populations

Elderly patients: More susceptible to dehydration, electrolyte imbalance, renal decline, and QT prolongation—use loperamide with extreme caution and avoid in those taking QT-prolonging medications 4, 3

Cancer patients on chemotherapy: Dose reductions may be needed for patients ≥70 years receiving irinotecan or capecitabine; watch for neutropenic enterocolitis 4

Immunocompromised patients: Consider empiric antibiotics even for watery diarrhea; watch for C. difficile superinfection 5, 6