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

Diarrhea Workup and Management

Initial Clinical Assessment

Begin by obtaining a detailed history focusing on stool characteristics (watery, bloody, mucoid, greasy), frequency, duration, and associated symptoms including fever, abdominal pain, tenesmus, and signs of volume depletion (thirst, orthostasis, decreased urination, lethargy). 1

Key historical elements to elicit:

• Onset and duration: Acute (<14 days) versus chronic (>4 weeks) diarrhea 1
• Stool characteristics: Number per day, consistency, presence of blood/mucus, nocturnal symptoms 1, 2
• Volume depletion signs: Orthostatic vital signs, dry mucous membranes, decreased skin turgor, altered mental status 1
• Epidemiological risk factors: Recent travel, day-care exposure, unsafe food/water consumption, animal contact, sick contacts, recent antibiotics, immunosuppression (HIV/AIDS, immunosuppressive medications), sexual practices, occupation as food handler 1
• Medication review: Recent antibiotics, antacids, antimotility agents, chemotherapy 1
• Dietary history: Lactose-containing products, alcohol, high-osmolar supplements 1, 2

Diagnostic Testing Strategy

Diagnostic testing should be reserved for patients with severe dehydration, bloody stools, persistent fever, immunocompromised status, or symptoms lasting >7 days with no improvement. 1, 3

When testing is indicated:

• Stool studies: Culture for bacterial pathogens (Salmonella, Shigella, Campylobacter), ova and parasites if indicated by exposure history, Clostridioides difficile testing if recent antibiotic use 1
• Blood work: Complete blood count, electrolyte panel, renal function in severe cases 1
• Endoscopy: Reserved for chronic diarrhea with alarm features (blood in stool, weight loss, anemia, palpable abdominal mass) or when initial workup is unrevealing 3, 4

Most cases of acute watery diarrhea are self-limited viral infections requiring no diagnostic workup. 3

Hydration Management

Mild to Moderate Dehydration

Reduced osmolarity oral rehydration solution (ORS) is first-line therapy for all patients with mild to moderate dehydration from any cause of diarrhea. 1

• Use WHO-recommended ORS formulations (e.g., Pedialyte, Ceralyte) containing approximately Na 90 mM, K 20 mM, Cl 80 mM, HCO₃ 30 mM, and glucose 111 mM 1
• Continue ORS until clinical dehydration is corrected, then maintain with ORS to replace ongoing losses 1
• Nasogastric ORS administration may be considered for patients unable to tolerate oral intake 1

Severe Dehydration

Isotonic intravenous fluids (lactated Ringer's or normal saline) must be administered immediately for severe dehydration, shock, altered mental status, or ileus. 1

• Continue IV rehydration until pulse, perfusion, and mental status normalize 1
• Once stabilized and able to tolerate oral intake, transition to ORS for remaining deficit replacement 1

Dietary Management

Implement dietary modifications immediately while maintaining adequate hydration. 1, 2

• Eliminate: All lactose-containing products, alcohol, high-osmolar dietary supplements 1, 2
• Encourage: 8-10 large glasses of clear liquids daily (electrolyte solutions, broth) 1, 2
• BRAT diet: Bananas, rice, applesauce, toast, plain pasta—frequent small meals 1, 2
• Continue breastfeeding in infants throughout the diarrheal episode 1
• Resume age-appropriate diet immediately after rehydration is complete 1

Pharmacological Management

Antimotility Agents

Loperamide may be given to immunocompetent adults with acute watery diarrhea at an initial dose of 4 mg followed by 2 mg after each unformed stool, not exceeding 16 mg daily. 1, 5

Critical contraindications and precautions:

• Never use in children <18 years of age with acute diarrhea 1
• Avoid in any patient with: Bloody diarrhea, high fever, suspected inflammatory diarrhea, or risk of toxic megacolon 1, 5
• Avoid in elderly patients taking QT-prolonging drugs (Class IA/III antiarrhythmics, certain antipsychotics, fluoroquinolones) due to cardiac arrhythmia risk 5
• Do not exceed recommended doses: Higher doses increase risk of cardiac arrest, Torsades de Pointes, and sudden death 5
• Discontinue after 12-hour diarrhea-free interval 1, 2
• If no improvement within 48 hours, discontinue and reassess 5

Antiemetics

Ondansetron may be given to children >4 years and adolescents with vomiting to facilitate oral rehydration tolerance. 1

Second-Line Agents for Refractory Diarrhea

For persistent diarrhea despite loperamide or severe grade 3-4 diarrhea, consider octreotide 100-150 μg subcutaneously three times daily. 1, 2

• Dose may be escalated up to 500 μg three times daily if needed 1
• IV administration (25-50 μg/hour) if severe dehydration present 1
• Anticholinergic agents (hyoscyamine, atropine) may be added for persistent symptoms 1, 2

Adjunctive Therapies

Probiotics may be offered to reduce symptom severity and duration in immunocompetent patients with infectious or antibiotic-associated diarrhea. 1

Zinc supplementation (10-20 mg daily) reduces diarrhea duration in children 6 months to 5 years in areas with high zinc deficiency prevalence or malnutrition. 1

Antimicrobial Therapy

Empiric antibiotics should NOT be given routinely for acute watery diarrhea. 1

Antibiotics are indicated only when:

• Specific pathogen identified requiring treatment (e.g., Shigella, Campylobacter in severe cases, parasites) 1
• Severe inflammatory diarrhea with fever and bloody stools in immunocompromised patients 1
• Traveler's diarrhea with moderate-to-severe symptoms (fluoroquinolone or azithromycin) 1

Modify or discontinue antimicrobials once a clinically plausible organism is identified. 1

Red Flags Requiring Urgent Referral or Hospitalization

Hospitalize or urgently refer patients with:

• Severe dehydration unresponsive to oral rehydration 1
• Grade 3-4 diarrhea (≥7 stools/day above baseline) with fever, blood in stool, or neutropenia 1
• Signs of sepsis, toxic megacolon, or bowel obstruction 1, 5
• Immunocompromised patients (AIDS, chemotherapy) with persistent symptoms 1
• Chronic diarrhea with alarm features: bloody stools, weight loss, anemia, palpable abdominal mass 3, 4

Common Pitfalls to Avoid

• Do not use antimotility agents in bloody or febrile diarrhea: Risk of toxic megacolon and prolonged pathogen shedding 1, 5
• Do not withhold food during rehydration: Early refeeding reduces stool output and improves outcomes 1
• Do not exceed loperamide 16 mg/day: Serious cardiac arrhythmias and death reported with higher doses 5
• Do not give loperamide to children <18 years: Risk of respiratory depression and cardiac toxicity 1, 5
• Do not forget fluid replacement: Pharmacologic therapy never substitutes for adequate hydration 1, 5