II. Definitions
- 
                          Gastroenteritis
                          
- Inflammation of the Gastrointestinal Tract (Stomache and Small Intestine)
 - Typical presentation is Vomiting followed by Diarrhea
 - Most typically secondary to Viral Gastroenteritis
- Can also be caused by Bacteria with ingestion of preformed toxin
 
 
 - Diarrhea
- Frequent liquid, loose or watery stools
- Adults: >200 g/day of stool (at least 3 Bowel Movements daily)
 - Children: >20 g/kg/day of stool
 
 - Timing
- Acute Diarrhea: Duration <2 weeks
- Considered prolonged when duration >7 days
 
 - Persistent Diarrhea: Duration 2 to 4 weeks
 - Chronic Diarrhea: Duration >4 weeks
 
 - Acute Diarrhea: Duration <2 weeks
 
 - Frequent liquid, loose or watery stools
 
III. Epidemiology
- Foodbourne Diarrhea cases: 48 million/year U.S.
 - As many as 179 million outpatient visits in the U.S. per year
 - Hospitalizations: 128,000 to 500,000/year U.S
 - Deaths: 3000 to 5000 per year U.S. (2.5 Million/year worldwide)
 
IV. Pathophysiology
- 
                          Small Intestine secretes and reabsorbs 10 liters/day
- Extrusion of Chloride from villus crypt cell (cAMP)
 - Absorption at villus tip
 
 - Diarrhea classified as one of 3 types
- Watery Diarrhea
- Secretory Diarrhea
- Stool Sodium high (60-120 meq/L)
 - Hypersecretion by intestinal crypts
 
 - Osmotic Diarrhea (osmotic loss of free water)
- Stool Sodium low (30-40 meq/L)
 - Ingestion of non-digestable agents that draw water from the bowel wall
 
 
 - Secretory Diarrhea
 - Inflammatory Diarrhea (Dysentery)
- Severe Diarrhea with pus or blood present in the stool
 - Associated with fever, Abdominal Pain and tenesmus
 
 - Fatty Diarrhea (Malabsorption)
- See Chronic Diarrhea
 - Large greasy, frothy pale stools with foul odor
 
 
 - Watery Diarrhea
 - Serum Electrolyte loss
- Serum Bicarbonate loss
 - Serum Potassium loss
 
 
V. Causes: Acute Vomiting (Gastroenteritis)
- See Vomiting Causes
 - See Foodborne Illness
 - Severe Emergency Department cases in adults
 
VI. Causes: Acute Diarrhea
- See Chronic Diarrhea for systemic medical condition causes of Diarrhea
 - See Drug-Induced Diarrhea
 - Noninfectious Causes
- See Osmotic Diarrhea
 - See Secretory Diarrhea
 - Common Causes
- Partial Intestinal Obstruction
 - Toxic Ingestions
 - Endocrine Causes (Thyroid disease)
 - Inflammatory Bowel Disease (and other inflammatory and Allergic Conditions)
- Crohn Disease
 - Ulcerative Colitis
 - Radiation Enteritis
 
 - Drug Withdrawal (e.g. Opioid Withdrawal)
 - Cholinergic Toxicity (e.g. Organophosphate Poisoning)
 - Mesenteric Ischemia
 
 
 - Extra-intestinal and non-Gastroenteritis infections
 - 
                          Infectious Diarrhea Causes
                          
- See Infectious Diarrhea Causes
 - See Foodborne Illness
 - See Waterborne Illness
 - Viruses (30-40% of episodes) - Non-Inflammatory Diarrhea
 - 
                              Bacteria and Parasites (20-30% of episodes)
- Inflammatory Diarrhea from Bacteria and Parasites (Dysentery)
- Campylobacter jejuni (most common Bacteria)
 - Salmonella
 - Shigella
 - Shiga-toxin producing E. coli (e.g. E. coli 0157:H7, Enterohemorrhagic E. coli)
- Causes 30% of infectious bloody Diarrhea
 
 - Clostridioides difficile
 - Entamoeba histolytica
 - Yersinia
 
 - Non-Inflammatory Diarrhea from Bacteria and Parasites
 
 - Inflammatory Diarrhea from Bacteria and Parasites (Dysentery)
 
 
VII. Risk Factors
- See Chronic Diarrhea for systemic medical condition causes of Diarrhea
 - See Infectious Diarrhea Causes
 - Recent travel to endemic area
- See Traveler's Diarrhea
 - Travel to a developing area is associated with a 25% chance of developing Diarrhea
 - Those with Diarrhea in a developing area have an 80% chance of Bacterial Diarrhea
 
 - Food associated illness
- See Foodborne Illness
 - Associated with raw meats, poultry, fish, seafood, milk, rice
 
 - Wilderness travel (or in developing country)
- See Waterborne Illness
 - Hiking in wilderness areas (especially drinking from mountain streams)
 - Consider Giardia, Entamoeba histolytica, Cryptospordium
 
 - Day care exposure
- Consider Rotavirus, Cryptosporidium, Giardia, Shigella
 
 - High-risk sexual behavior
- See Infectious Diarrhea Causes
 - Fecal-oral sexual contact: Shigella, Salmonella, Campylobacter, Protozoa
 - Receptive anal intercourse: Herpes Simplex Virus, Chlamydia, Gonorrhea, Syphilis
 
 - 
                          Antibiotic use within 6 months or recent hospitalizations
- See Clostridium difficile
 - C. Difficile Incidence in unexplained Diarrhea after 3 or more day hospitalization: 15-20%
 - Risk of infection after Antibiotics in first month (7-10 fold increased risk)
- Risk persists more than 3 months after Antibiotics (2-3 fold increased risk)
 
 - Consider Klebsiella oxytoca (uncommon)
- Like Clostridium difficile, causes Antibiotic-Associated Diarrhea, that may be hemorrhagic
 - Improves after stopping Antibiotics and NSAIDs
 
 
 - 
                          Immunosuppression (e.g. HIV Infection, Chemotherapy, longterm Corticosteroids, Immunoglobulin A Deficiency)
- See Diarrhea in HIV
 - Consider Cryptosporidium, Microsporida, Isospora, Cytomegalovirus
 - Consider Mycobacterium Avium Intracellulare complex, Listeria monocytogenes
 
 
VIII. History: Diarrhea
- See Vomiting
 - 
                          Stool size
- Frequent small volume stools
 - Frequent large volume stools
 
 - 
                          Stool consistency
- Rice-water stools (Vibrio Cholerae)
 
 - Provocative agents
- Foods
 - Milk
 - Sorbitol
 - New medications (see Medication-Induced Diarrhea)
 
 - 
                          Inflammatory Diarrhea associated findings
- Blood or mucous present in stool
 - Fever (typically absent in Shiga-toxin producing E. coli 0157:H7)
 - Abdominal Pain
 - Tenesmus (or Rectal Pain or Proctitis)
 
 - Other associated findings
- Paresthesias (consider Neurotoxin such as Ciquatera toxin)
 
 - Acute symptoms in multiple people with same food exposure (Preformed toxins)
- See Foodborne Illness
 - Symptom onset within 6 hours (presents with Vomiting)
- Staphylococcus Aureus (often from cold mayonnaise-based salads)
 - Bacillus Cereus (meats, rice)
 
 - Symptom onset within 8-16 hours (presents with Diarrhea)
- Clostridium perfringens (Cooked meats)
 
 
 
IX. Symptoms
- 
                          Fever
                          
- Campylobacter
 - Salmonella typhi
 - Shigella
 - Yersinia
 - May also occur with Clostridium difficile and Entamoeba histolytica
 
 - 
                          Abdominal Pain
                          
- Campylobacter
 - Salmonella typhi
 - Shigella
 - Shiga-toxin producing E. coli (e.g. E. coli 0157:H7, Enterohemorrhagic E. coli)
 - Yersinia
 - Giardia
 - Norovirus
 - May also occur with Clostridium difficile and Entamoeba histolytica
 
 - 
                          Nausea or Vomiting
- Shigella
 - Norovirus
 - Also occur with Campylobacter, Salmonella, E. coli 0157:H7, Yersinia, Cryptosporidium, Cyclospora, Giardia
 
 - Bloody stool
- Shiga-toxin producing E. coli (e.g. E. coli 0157:H7, Enterohemorrhagic E. coli)
- Causes 30% of infectious bloody Diarrhea
 
 - May also occur with Campylobacter, Clostridium difficile, Salmonella, Shigella, Yersinia
 
 - Shiga-toxin producing E. coli (e.g. E. coli 0157:H7, Enterohemorrhagic E. coli)
 
X. Exam
- See Vomiting
 - Evaluate for signs of Dehydration
- Tachycardia
 - Dry mucous membranes
 - Decreased Urine Output
 - Altered Level of Consciousness
 - Capillary Refill
 - Poor Skin Turgor
 - Sunken Fontanelles (infants)
 
 - 
                          Eye Exam
                          
- 
                              Episcleritis
                              
- Consider Inflammatory Bowel Disease such as Reiters Syndrome
 
 
 - 
                              Episcleritis
                              
 - Thyroid exam
 - Skin Exam
 - Abdominal exam
- Benign Abdomen despite severe pain
- Consider Mesenteric Ischemia (especially if grossly bloody stool)
 
 - Bowel sounds
- Hyperactive bowel sounds
- Typical in Diarrheal illness
 
 - Hypoactive bowel sounds
 
 - Hyperactive bowel sounds
 
 - Benign Abdomen despite severe pain
 - 
                          Rectal Exam
                          
- 
                              Anal Fissures
- Consider Inflammatory Bowel Disease
 
 - Bloody stool (occult or gross)
- Consistent with Acute Inflammatory Diarrhea
 - Concurrent fever, Abdominal Pain, tenesmus also suggest Acute Inflammatory Diarrhea
 - Consider Inflammatory Bowel Disease
 - Consider Mesenteric Ischemia
 
 
 - 
                              Anal Fissures
 
XI. Labs
- See specific tests for indications
 - Precautions
- Labs are expensive and do not alter management in most cases (in the United States)
 - Directed history and exam are most useful
 
 - 
                          General indications for lab testing
- Dysentery (Bloody Diarrhea, Fever, Abdominal Pain, Tenesmus)
 - Sepsis
 - Persistently more than 6 stools daily
 - More than 1 week of symptoms without improvement
 - Hospital admission for Dehydration
 - History suggestive of specific Parasite or pathogen
 - Recent travel with moderate to severe Diarrhea (esp. with fever)
 - Public health implications
- Food handlers, healthcare workers or childcare workers
 - Nursing Home residents
 
 - High risk patient
- Age >65 years old
 - Infant <12 months
 - Pregnancy
 - Immunocompromised state
 - Men who have Sex with Men
 
 
 - Labs performed as indicated
- Enteric Pathogens Nucleic Acid Test Panels (PCR, NAAT)
- May include Campylobacter, Salmonella, Shigella, Vibrio, Yersina, Norovirus, Rotavirus, Shiga-Toxin
 - Some panels (e.g. Biofire FilmArray) include C. Diff, as well as >20 other Bacteria, Parasites and viruses
 
 - Stool Antigens
- Giardia lambliaAntigen
- Indicated for Diarrhea >7 days and >10 stools/day
 
 - CryptosporidiumAntigen
- Immunocompromised patients
 
 - Clostridium difficile Toxin
- Follows hospitalization for >3 days or
 - Antibiotic use within prior 3 months
 
 - RotavirusAntigen
- Indicated for defining local outbreak
 
 
 - Giardia lambliaAntigen
 - Medication levels
- Theophylline level
 - Lithium level
 
 - Pregnancy Test
- Consider in all women of reproductive age with significant gastrointestinal symptoms
 
 - Serum Electrolytes (basic metabolic panel)
- Normal in 99% of young, healthy adults with Acute Gastroenteritis in the first 24 hours
 - Indications
- Prolonged Diarrhea
 - Dehydration requiring IV fluids
 - Toxic or ill appearance
 - Serious comorbid condition
 
 - Findings
 
 - Other testing to consider
 
 - Enteric Pathogens Nucleic Acid Test Panels (PCR, NAAT)
 - Older tests that have mostly been replaced in U.S. by more specific testing as above
- Fecal lactoferin
- Poor Test Specificity
 
 - Fecal Leukocytes
- Stool Guaiac has the same Positive Predictive Value to identify Bacterial Diarrhea
 - Bloody stool without Fecal Leukocytes suggests E coli 0157:H7 or Entamoeba histolytica
 - Decreased Test Sensitivity with any delay in evaluation (samples easily degrade)
 
 - Stool Culture
- Replaced by Enteric Pathogens Nucleic Acid Test Panels (PCR)
 - Expensive and very low test senstitivity (5%)
 - Indications
- Toxic appearance
 - Prolonged Diarrhea >4 days
 - Blood or pus in stool (or other signs of Inflammatory Diarrhea)
 - Immunocompromised patients
 
 
 - Ova and Parasites
- Low yield (requires multiple samples)
 - Specific Stool ParasiteAntigens are preferred with better accuracy
 - Indications
- Travel to developing countries
 - Watery Diarrhea >7 days
 
 
 
 - Fecal lactoferin
 
XII. Evaluation: Labs for specific presentations
- See Labs and Endoscopy below
 - 
                          Inflammatory Diarrhea or Dysentery
- Enteric Pathogens Nucleic Acid Test Panels (PCR) or Stool Cultures (SSCE)
- Salmonella including Salmonella typhi
 - Shigella
 - Campylobacter
 - Escherichia coli 0157:H7 (STEC: Shiga Toxin E coli)
- Shiga Toxin (if bloody stool)
 - Avoid Antimicrobial Agents
 
 
 - Clostridium difficile Toxins
- Indicated for recent Antibiotics or Chemotherapy
 
 - Consider Antibiotic coverage (if not STEC)
- Quinolone if suspected Shigellosis
 - Macrolide for suspected Campylobacter
 
 
 - Enteric Pathogens Nucleic Acid Test Panels (PCR) or Stool Cultures (SSCE)
 - Nosocomial Diarrhea (after 3 days of hospitalization)
- Clostridium difficile Toxins
 - Enteric Pathogens Nucleic Acid Test Panels (PCR) or SSCE culture
- Especially if nosocomial outbreak, age over 65 years, comorbidity or Immunocompromised
 
 - Discontinue Antibiotics if possible
 - Consider Flagyl if worsens or persists
 
 - Persistent Diarrhea >7 days (esp. Immunocompromised)
- Fecal Lactoferrin (preferred over Fecal Leukocytes)
- High Test Sensitivity for SSCE Bacteria (up to 93%) as well as increased in Inflammatory Bowel Disease
 
 - Parasitic Infection evaluation (esp. if adominal bloating, Eructation, Nausea)
 
 - Fecal Lactoferrin (preferred over Fecal Leukocytes)
 - 
                          Immunocompromised
                          
- See Diarrhea in HIV
 - Consider Clostridium difficile Toxin (especially if recent Antibiotics or hospitalization)
 - Consider Nucleic Acid Amplification Tests or SSCE Stool Culture (especially if Inflammatory Diarrhea)
 - Consider Parasitic Infections (e.g. Cryptosporidium, especially if present >7 days)
 - Consider other opportunistic infections (especially in HIV positive patients)
- Microsporidia
 - Mycobacterium Avium Intracellulare Complex
 - Cytomegalovrius
 
 
 
XIII. Evaluation: Endoscopy
- Indications
- Unclear diagnosis with persistent symptoms
 - Suspected Tuberculosis
 - Diffuse colitis (e.g. Clostridium difficile)
 - Noninfectious Diarrhea cause evaluation (e.g. Inflammatory Bowel Disease)
 - Does not distinguish Infectious from Inflammatory Diarrhea
 - Immunocompromised condition (e.g. AIDS, HIV Infection)
 
 - 
                          Sexually Transmitted Disease (STD)
- Lesions in Distal 15 cm in homosexual men
 - Herpes Virus
 - NeisseriaGonorrhea
- Nonspecific findings limited to Rectum
 - Biopsy and Culture show superficial exudates
 
 - Syphilis
 - Chlamydia (Lymphogranuloma venereum)
- Similar to Inflammatory Bowel Disease
 
 
 
XIV. Management: Vomiting
- See Vomiting
 - See Antiemetic
 - See Vomiting Management in Children
 - See Vomiting in Pregnancy
 
XV. Management: General
- See Diarrhea Management in Children
 - See Traveler's Diarrhea Management
 - Intravenous Fluid indications
 - 
                          Electrolyte solutions containing Glucose (not Artificial Sweetener)
- Glucose assists with water reabsorption
 - Oral Rehydration Solution (ORS) is preferred but may not be tolerated well
- See Oral Rehydration Solution
 - Pedialyte, Rehydrate or Infalyte in children
 
 - Gatorade or similar
- May be used as alternative (but not ideally formulated to match Diarrheal losses)
 - Requires 1:1 dilution with water to half strength
 
 
 - Dietary guidance
- Early reintroduction of food is recommended
- Decreases Diarrhea severity and duration
 - Restores nutritional status earlier
 - Duggan (1997) J Pediatr 131(6): 801-8 [PubMed]
 
 - BRAT diet
- Includes Bananas, rice, apple sauce, toast, soup, crackers
 - Reasonable and non-harmful, but not evidence-based
 - Likely too restrictive, and patients are now encouraged to eat what they will tolerate
 
 - Avoid provocative agents that worsen Diarrhea
 
 - Early reintroduction of food is recommended
 - Adjunctive measures
- Probiotics
- Show benefit in Pediatric Diarrhea, but not verified in adults
 - Consider Lactobacillus GG (Culturelle) or Saccharomyces boulardii (Florastor)
 - Decreases Diarrhea duration by one day, and decreases risk of prolonged Diarrhea
 - Collinson (2020) Cochrane Database Syst Rev (12):CD003048 [PubMed]
 
 - Zinc
- Reduces severity of Pediatric Diarrhea in developing countries, but not evaluated in adults in U.S.
 
 
 - Probiotics
 - Antidiarrheal medications
- Loperamide (Imodium)
- Antimotility properties
 - Do not use Loperamide if fever or bloody stool are present (Inflammatory Diarrhea)
 
 - Bismuth Subsalicylate (Pepto-Bismol)
- May be used in Inflammatory Diarrhea
 - Antisecretory properties
 - Contraindicated in children (contains Salicylates)
 
 
 - Loperamide (Imodium)
 
XVI. Management: Antibiotics
- Use is controversial with potentially serious complications (e.g. Hemolytic Uremic Syndrome)
 - Advantages
- Antibiotics appear to shorten Diarrhea course by 24 hours
 - Effect is regardless of stool guiaic, fecal Leukocyte or Stool Culture result
 
 - Disadvantages
- Most Acute Diarrheal is non-infectious, viral or self-limited
 - Increased Antibiotic Resistance
 - Increased risk of prolonged carrier state with certain infections (e.g. Salmonella)
 - Increased risk of developing Hemolytic Uremic Syndrome with E. coli 0157:H7
 - Increased risk of Clostridium difficile
 
 - Contraindications
- Grossly bloody Diarrhea or other signs of Escherichia coli 0157:H7 (STEC: Shiga Toxin E coli)
- Risk of Hemolytic Uremic Syndrome increases with Antibiotic use
 
 
 - Grossly bloody Diarrhea or other signs of Escherichia coli 0157:H7 (STEC: Shiga Toxin E coli)
 - Indications
- Findings suggestive of Bacterial Diarrhea
- Guiaic positive stool (not grossly bloody stool)
 - Fecal Leukocyte positive
 
 - Overseas travel
 - Diarrheal illness lasting longer than 10-14 days
 - Immunocompromised patients
 - Severe illness or Sepsis
 - Age over 65 years old
 
 - Findings suggestive of Bacterial Diarrhea
 - Empiric Antibiotics
- See Traveler's Diarrhea Management
 - Ciprofloxacin (adults)
- Empiric adult dose: 500 to 1000 mg once or 500 mg twice daily for 3 days
 - Preferred agent for E. coli (ETEC, EIEC), Shigella
 - Also covers Campylobacter, Salmonella, Yersinia, Cryptosporidium
 
 - Trimethoprim-Sulfamethoxazole (Septra, Bactrim)
- Empiric adult dose: One DS twice daily for 3-5 days
 - Preferred agent for Cyclospora or Isospora
 - Also covers E. coli (ETEC, EIEC), Salmonella, Shigella, Vibrio Cholerae, Yersinia (Septra has higher resistance rates)
 - Used in combination with Aminoglycoside to treat non-Vibrio Cholerae
 
 - Azithromycin
- Empiric adult dose: 500 mg daily for 3 days
 - Preferred agent for Campylobacter
 - Also covers E. coli (ETEC), Salmonella, Shigella, Vibrio Cholerae
 
 - Third Generation Cephalosporin (e.g. Cefdinir, Cefpodoxime)
- Consider in children for Shigella, Salmonella
 - Ceftriaxone is a first line agent in Non-Typhoidal Salmonella and Shigella
 - Covers Yersinia enterocolitica and Salmonella enterica, typhi or paratyphi (Ceftriaxone)
 
 
 - Other Antibiotics used for specific indications
- Metronidazole
- Preferred agent for Entamoeba histolytica
 - Alternative agent for Clostridium difficile (but high failure rate), and Giardia
 
 - Azithromycin
- Campylobacter (treat with 3-5 day course)
 - Shigella
 
 - Ciprofloxacin
- Non-Typhoidal Salmonella (other Fluoroquinolones are also effective)
 - Salmonella enterica, typhi or paratyphi
 - Shigella (Reduces duration and shedding)
 - Campylobacter (alternative agent)
 - Yersinia enterocolitica
 
 - Doxycycline
- Preferred agent for Vibrio Cholerae
 - Used in combination with Ceftriaxone to treat non-Vibrio Cholerae
 - Also covers Yersinia (when combined with an Aminoglycoside)
 
 - Oral Vancomycin
- Alternative agent for Clostridium difficile
 
 - Fidaxomicin (Dificid)
- Preferred agent for Clostridium difficile
 
 - Amoxicillin
- Non-Typhoidal Salmonella
 
 
 - Metronidazole
 - 
                          Antiparasitic Agents used for specific indications
- See Metronidazole indications above
 - Albendazole (Albenza)
- Preferred agent for Microsporida
 
 - Tindazole (Tindazole)
- Covers Entamoeba histolytica (when treated in combination with Paromomycin)
 - Preferred agent for Giardia
 
 - Nitazoxanide (Alinia)
- Covers Cryptosporidium
 - Preferred agent for Giardia
 
 
 
XVII. Management: Admission Criteria
- Severe Diarrhea with difficulty maintaining hydration
 - Very young or very old
 - Severe comorbid illness
 - Severe pain
 - High fever
 - Intractable Vomiting
 
XVIII. Prevention
- See Water Disinfection
 - See Traveler's Diarrhea Prevention
 - See Foodborne Illness Prevention
 - 
                          Hand Washing
                          
- Wash with soap and water for at least 20 seconds ("Mary had a little lamb...") before rinsing
 - Decreases Infectious Diarrhea Incidence by one third
 - Ejemot (2008) Cochrane Database Syst Rev (1):CD004265 [PubMed]
 
 - Healthcare workers and food workers should not return to work until symptoms have resolved for 48 hours
 - 
                          Vaccinations
- Rotavirus (part of Primary Series in U.S. for infants)
 - Typhoid Vaccine (frequently required for overseas Travel Immunizations)
 - Cholera Vaccine
 
 - CDC Reportable Illnesses (National Notifiable Diseases Surveillance System or NNDSS)
 
XIX. Complications: Postinfectious Diarrhea Conditions
- Erythema Nodosum
 - Glomerulonephritis
 - Guillain-Barre Syndrome
 - Hemolytic Anemia
 - Hemolytic Uremic Syndrome
 - IgA Nephropathy
 - Lactose Intolerance (transient)
 - Meningitis
 - Reactive Arthritis
 - Postinfectious Irritable Bowel Syndrome
 - Bowel Perforation
 
XX. Resources
- IDSA Clinical Practice Guidelines for the Diagnosis and Management of Infectious Diarrhea (2017)
 
XXI. References
- Glauser and Schafer (2020) Crit Dec Emerg Med 34(1):3-12
 - May and Mason in Herbert (2021) EM:Rap 21(6): 15-6
 - Herbert (2012) EM:RAP-C3 2(4): 2
 - Barr (2014) Am Fam Physician 89(3): 180-9 [PubMed]
 - Guerrant (2001) Clin Infect Dis 32:331-48 [PubMed]
 - Meisenheimer (2022) Am Fam Physician 106(1): 72-80 [PubMed]
 - Scallen (2011) Emerg Infect Dis 17(1): 7-15 [PubMed]
 - Shane (2017) Clin Infect Dis 65(12): e45-80 [PubMed]