Common Causes, Presentations, and Treatments of Gastroenteritis in the US
Oral rehydration therapy is the cornerstone of treatment for most cases of gastroenteritis, with antimicrobial therapy reserved only for specific bacterial causes and patient populations. 1
Common Causes of Gastroenteritis
Viral Causes
- Rotavirus: Most common cause in children <5 years before vaccine introduction; now less common due to vaccination 2
- Norovirus: Currently the leading pathogen causing gastroenteritis in the US (58% of cases) 2
- Other viruses: Adenovirus, astrovirus, calicivirus
Bacterial Causes
- Salmonella: Leading bacterial cause (11% of cases), responsible for 35% of hospitalizations 2
- Campylobacter: Common bacterial cause, especially from contaminated food
- Shigella: Associated with bloody diarrhea and fever
- E. coli (including STEC): Can cause severe illness including hemolytic uremic syndrome
- Clostridioides difficile: Common cause of nosocomial and antibiotic-associated diarrhea
Parasitic Causes
- Giardia lamblia: Common in daycare settings and contaminated water
- Cryptosporidium: Associated with recreational water exposure
Clinical Presentations
Viral Gastroenteritis
- Incubation period: 1-3 days
- Symptoms: Abrupt onset, often with vomiting preceding diarrhea
- Fever: Up to one-third have temperature >102°F (>39°C)
- Duration: Typically resolves in 3-7 days
- Seasonality: Winter peaks (November-May) 2
Bacterial Gastroenteritis
- Shigella/Dysentery: Frequent scant bloody stools, fever, abdominal cramps, tenesmus 2
- Salmonella: Fever, abdominal pain, diarrhea (may be bloody)
- Campylobacter: Fever, abdominal pain, bloody diarrhea
- STEC: Bloody diarrhea, abdominal pain, risk of hemolytic uremic syndrome
Dehydration Assessment
| Severity | Fluid Deficit | Clinical Signs |
|---|---|---|
| Mild | 3-5% | Increased thirst, slightly dry mucous membranes, normal vital signs |
| Moderate | 6-9% | Loss of skin turgor, skin tenting, dry mucous membranes, tachycardia |
| Severe | ≥10% | Lethargy, prolonged skin tenting, cool extremities, decreased capillary refill, hypotension [1] |
Treatment Approach
Rehydration Therapy
- First-line treatment: Oral rehydration solution (ORS) for mild to moderate dehydration 1
- Children: 50-100 mL/kg over 3-4 hours
- Adults: 2-4 L of ORS
- Severe dehydration: IV fluids with isotonic solutions (lactated Ringer's or normal saline) 1
Nutritional Management
- Continue breastfeeding throughout diarrheal episodes
- Resume normal diet during or immediately after rehydration 1
- Avoid fasting for prolonged periods
Antimicrobial Therapy
Empiric antimicrobial therapy is not recommended except in specific situations 2:
- Infants <3 months with suspected bacterial etiology
- Immunocompromised patients with severe illness and bloody diarrhea
- Fever >38.5°C with bloody diarrhea and recent international travel
- Signs of sepsis
When indicated, recommended antimicrobials 2:
- Adults: Fluoroquinolone (e.g., ciprofloxacin) or azithromycin based on local susceptibility patterns
- Children: Third-generation cephalosporin (infants <3 months) or azithromycin
Symptomatic Treatment
- Antiemetics: Ondansetron may be given to children >4 years when vomiting is significant (0.15 mg/kg) 1
- Antimotility agents: Loperamide contraindicated in children <18 years and in bloody diarrhea; may be used in adults with watery diarrhea 1
- Probiotics: May reduce symptom severity and duration in immunocompetent patients 1
Special Considerations
When to Test
- Mild symptoms resolving within a week: No testing needed 3
- Indications for stool testing:
- Bloody diarrhea
- Severe symptoms or prolonged duration (>7 days)
- Recent antibiotic exposure (test for C. difficile)
- Immunocompromised host
- Suspected outbreak
High-Risk Populations
- Infants and young children: Higher risk of dehydration due to higher body surface-to-weight ratio and metabolic rate 1
- Elderly: More susceptible to complications from dehydration; require close monitoring 1
- Immunocompromised patients: May experience severe, prolonged, and even fatal rotavirus gastroenteritis 2
Prevention
- Hand hygiene: Critical after using toilet, changing diapers, before/after food preparation 1
- Vaccination: Rotavirus vaccine has reduced infections by up to 90% in children 3
- Food safety practices: Proper cooking and storage of food
Common Pitfalls to Avoid
- Using ondansetron as a substitute for rehydration therapy
- Administering loperamide to children or patients with bloody diarrhea
- Delaying reintroduction of normal diet
- Unnecessary antimicrobial therapy for viral gastroenteritis
- Overlooking the need for IV fluids in severely dehydrated patients 1