What is the evaluation and management of acute diarrhea in adults?

Evaluation and Management of Acute Diarrhea in Adults

Initial Triage and Risk Stratification

Self-medication is safe for previously healthy adults under 75 years with sudden onset of watery diarrhea without warning signs, but immediate medical evaluation is required for high fever (≥38.5°C), bloody stools, severe vomiting, obvious clinical dehydration, or altered mental status 1, 2.

Warning Signs Requiring Immediate Medical Attention:

• High fever ≥38.5°C 1, 2
• Bloody or mucoid stools 1, 2
• Severe vomiting preventing oral intake 1
• Clinical dehydration (altered mental status, poor skin turgor, dry mucous membranes, decreased urine output) 1, 2
• Frail elderly patients >75 years or those with significant systemic illnesses 1, 2
• Immunocompromised status 3

Rehydration: The Cornerstone of Management

Mild to Moderate Dehydration:

Reduced osmolarity oral rehydration solution (ORS) is the first-line therapy for mild to moderate dehydration in adults with acute diarrhea from any cause 3.

• For otherwise healthy adults, formal ORS is not required—maintain adequate fluid intake guided by thirst using glucose-containing drinks or electrolyte-rich soups 1, 2
• Nasogastric ORS administration may be considered in adults with moderate dehydration who cannot tolerate oral intake 3
• Continue ORS until clinical dehydration is corrected 3

Severe Dehydration:

Isotonic intravenous fluids (lactated Ringer's or normal saline) must be administered when there is severe dehydration, shock, altered mental status, or failure of ORS therapy 3.

• Continue IV rehydration until pulse, perfusion, and mental status normalize 3
• Once stabilized, the remaining deficit can be replaced using ORS 3
• In patients with ketonemia, initial IV hydration may be needed to enable tolerance of oral rehydration 3

Diagnostic Evaluation

When to Order Stool Studies:

Diagnostic testing is not routinely recommended for most cases of acute watery diarrhea 3, 4. Reserve testing for:

• Bloody diarrhea or dysentery (bloody stools + fever + abdominal cramps + tenesmus) 3, 5
• Persistent fever >38.5°C 2, 6
• Severe dehydration or illness requiring hospitalization 4
• Immunocompromised patients 3, 4
• Recent international travel to endemic areas 3, 4
• Suspected nosocomial infection or outbreak 4
• No improvement within 48 hours 2

Pharmacological Management

Antimotility Agents (Loperamide):

Loperamide 2 mg may be given to immunocompetent adults with acute watery diarrhea once adequately hydrated, with flexible dosing after each unformed stool (maximum 16 mg/day) 1, 2, 7.

• Initial dose: 4 mg (two capsules), then 2 mg after each unformed stool 7
• Maximum daily dose: 16 mg (eight capsules) 7
• Clinical improvement usually observed within 48 hours 7

Critical contraindications for loperamide:

• Bloody diarrhea or suspected inflammatory diarrhea 3, 2
• High fever ≥38.5°C 1, 2
• Children <18 years of age 3
• Suspected toxic megacolon 3

The outdated belief that antimotility agents "trap toxins" and prolong illness is not evidence-based; modern evidence shows loperamide safely relieves symptoms without prolonging illness in uncomplicated cases 2.

Antiemetics:

Antinausea and antiemetic agents (e.g., ondansetron) may be given to facilitate tolerance of oral rehydration once the patient is adequately hydrated 3, 2.

Empiric Antibiotics:

In most adults with acute watery diarrhea without recent international travel, empiric antimicrobial therapy is NOT recommended 3.

Exceptions where empiric antibiotics should be considered:

• Dysentery (bloody diarrhea + fever + abdominal cramps): Azithromycin 500 mg daily for 3 days or 1 gram single dose 3, 5
• Traveler's diarrhea with fever ≥38.5°C and/or signs of sepsis: Azithromycin 1 gram single dose 5
• Immunocompromised patients with severe illness and bloody diarrhea 3, 5
• Suspected enteric fever with sepsis: Broad-spectrum antibiotics after cultures obtained 3

Critical pitfall: Avoid antibiotics in STEC O157 and other Shiga toxin 2-producing E. coli infections due to increased risk of hemolytic uremic syndrome 3, 5.

When a clinically plausible organism is identified, antimicrobial treatment should be modified or discontinued accordingly 3, 5.

Nutritional Management

Resume normal eating guided by appetite during or immediately after rehydration—there is no evidence that fasting or specific dieting is beneficial 3, 2.

• Avoid foods high in simple sugars, fatty, heavy, spicy foods, and caffeine 1, 2
• Consider avoiding lactose-containing foods (except yogurt and firm cheeses) in prolonged episodes 1, 2
• Human milk feeding should be continued in infants throughout the diarrheal episode 3

Monitoring and Follow-Up

Reassess hydration status after 2-4 hours of oral rehydration 1.

Red Flags Requiring Immediate Reassessment:

• No improvement within 48 hours 2
• Worsening symptoms or overall condition 2
• Development of bloody stools, persistent fever >38.5°C, severe vomiting, dehydration, or abdominal distension 2
• Decreased urine output, altered mental status, poor skin turgor, dry mucous membranes 1

Infection Control Measures

• Practice proper hand hygiene after using toilet, before food preparation and eating, and after handling soiled items 1, 2
• Use gloves and gowns when caring for people with diarrhea 1, 2
• Asymptomatic contacts should not receive empiric treatment but should follow infection prevention measures 3

Common Pitfalls to Avoid

• Do not delay rehydration while awaiting diagnostic testing 1
• Do not use sports drinks as primary rehydration in moderate to severe dehydration 1
• Do not unnecessarily restrict diet during or after rehydration 1, 2
• Do not start broad-spectrum antibiotics empirically when rehydration alone is indicated 3, 5
• Do not continue antibiotics when no bacterial pathogen is identified 5
• Do not give loperamide in cases of bloody diarrhea, high fever, or to children 3, 1