Management of Acute Infective Diarrhea in Adults
For most adults with acute infective diarrhea, oral rehydration solution is the cornerstone of treatment, empiric antibiotics should be withheld, and hospitalization is reserved for severe dehydration, shock, or altered mental status. 1
Rehydration: The Foundation of Treatment
First-Line Therapy
- Reduced osmolarity oral rehydration solution (ORS) (< 250 mmol/L) is the first-line treatment for mild-to-moderate dehydration, administered at approximately 100 mL/kg over 2–4 hours. 1
- ORS is superior to intravenous fluids when oral intake is tolerated—it is safer, less invasive, equally effective, and less costly. 1
- The WHO-recommended formulation contains approximately Na 90 mM, K 20 mM, Cl 80 mM, HCO₃ 30 mM, and glucose 111 mM. 1
When to Escalate to IV Fluids
- Switch to isotonic intravenous fluids (lactated Ringer's or normal saline) immediately if any of the following are present: 1
- Severe dehydration (≥ 9% fluid deficit)
- Circulatory shock
- Altered mental status
- Inability to tolerate oral intake or ORS failure
- Intestinal ileus
- Continue IV rehydration until pulse, perfusion, and mental status normalize, then transition back to ORS to replace the remaining deficit. 1
- In patients with ketonemia, an initial IV bolus may be required before oral rehydration becomes tolerable. 1
Alternative Routes
- Nasogastric delivery of ORS is acceptable for patients with moderate dehydration who cannot drink adequately but have intact mental status. 1
Ongoing Loss Replacement
- After initial rehydration, replace each watery stool with 10 mL/kg of ORS and each vomiting episode with 2 mL/kg of ORS, continuing until symptoms resolve. 1
- Reassess hydration status 2–4 hours after initiating therapy. 1
Nutritional Management
- Resume age-appropriate regular diet immediately during or after rehydration—do not withhold food. 1
- Early refeeding prevents malnutrition and may reduce stool output. 1
- Continue breastfeeding throughout the illness in infants and children. 1
Antibiotic Use: When to Treat and When to Avoid
General Rule: Avoid Empiric Antibiotics
- Empiric antibiotics are NOT recommended for most adults with acute watery diarrhea who have not recently traveled internationally. 1
- Antibiotics shorten illness duration by only approximately 1 day, with low-quality supporting evidence. 1
Specific Indications for Empiric Antibiotics
Consider empiric antimicrobial therapy only in these high-risk situations: 1
- Immunocompromised patients with severe illness
- Bloody diarrhea with fever, abdominal pain, and tenesmus (suggestive of shigellosis)
- Recent international travelers with fever ≥ 38.5°C or signs of sepsis
- Clinical features of sepsis with suspected enteric fever
- Ill-appearing infants < 3 months when bacterial infection is suspected
Critical Contraindication
- Never use antimicrobials for Shiga-toxin-producing E. coli (STEC O157 or other toxin-2 producers)—they increase the risk of hemolytic-uremic syndrome. 1
Modification Based on Culture Results
- Modify or discontinue antimicrobials once a specific pathogen is identified. 1
Antidiarrheal Agents: Use with Caution
Loperamide in Adults
- Loperamide may be used in immunocompetent adults with acute watery diarrhea ONLY after adequate hydration is achieved. 1
- Absolute contraindications to loperamide: 1
- Bloody diarrhea
- Fever
- Suspected inflammatory diarrhea (risk of toxic megacolon)
- Age < 18 years
Antiemetics
- Ondansetron may be given to children > 4 years and adolescents with vomiting to facilitate oral rehydration. 1
Probiotics
- Probiotic preparations may be offered to immunocompetent adults to reduce symptom severity and duration, though evidence quality is moderate. 1
Criteria for Hospitalization
Admit to hospital if any of the following are present: 1
- Toxic appearance
- Altered mental status
- Severe dehydration with inability to tolerate ORS
- Circulatory shock
- Signs of sepsis
Diagnostic Testing: When to Investigate
Alarm Signs Requiring Further Evaluation
Expedite diagnostics or consider admission if any of these are present: 1
- Bloody stools
- Fever ≥ 38.5°C
- Severe abdominal pain
- Tenesmus
- Signs of peritonitis
When to Order Stool Studies
- Stool testing (culture, multiplex PCR, microscopy for parasites) is indicated when diarrhea persists > 3 days together with fever or severe abdominal pain. 1
- Molecular studies are preferred over traditional stool cultures unless an outbreak is suspected. 2
Clinical Algorithm for Management
- Assess hydration status: Look for thirst, orthostasis, decreased urination, dry mucous membranes, altered mental status. 1
- Mild-to-moderate dehydration: Administer ORS 100 mL/kg over 2–4 hours. 1
- Severe dehydration or shock: Start isotonic IV fluids immediately, then transition to ORS once stabilized. 1
- Resume normal diet during or immediately after rehydration. 1
- Avoid empiric antibiotics unless specific high-risk features are present (immunocompromise, bloody diarrhea with fever, recent international travel with fever ≥ 38.5°C, sepsis). 1
- Replace ongoing losses with ORS until symptoms resolve. 1
- Consider hospitalization if toxic appearance, altered mental status, or severe dehydration with ORS failure. 1
Common Pitfalls to Avoid
- Do not give loperamide to patients with bloody diarrhea, fever, or suspected inflammatory diarrhea—risk of toxic megacolon. 1
- Do not give antimotility agents to anyone < 18 years of age. 1
- Do not withhold food during the diarrheal episode—early refeeding improves outcomes. 1
- Do not use antibiotics routinely for acute watery diarrhea—they provide minimal benefit and risk adverse effects. 1
- Do not use antibiotics for STEC infections—they increase hemolytic-uremic syndrome risk. 1
- Do not neglect rehydration while focusing on antimicrobial therapy—fluid replacement is the priority. 3