Gastroenteritis

Gastroenteritis Summary

Common Causes

Viruses: Norovirus, Rotavirus
Bacteria: Campylobacter, E. coli
Parasites: Giardia, Cryptosporidium
Toxins: Staph aureus, B. cereus

Dehydration Assessment

Mild: Lassitude, nausea
Moderate: Dizziness, tachycardia
Severe: Confusion, hypotension
Check skin turgor, eyes, mucous membranes

Admission Criteria

Shock/severe dehydration
Intractable vomiting
Bloody diarrhoea (STEC)
HUS/sepsis suspected
High-risk patients

Management

Oral rehydration: ORS solution
IV fluids: For shock/severe dehydration
Antibiotics: Only for specific pathogens
Antidiarrhoeals: Loperamide (avoid in dysentery)

Complications

HUS (E. coli O157)
Reactive arthritis
Guillain-Barré syndrome
Dehydration/electrolyte imbalance

Infection Control

48hr exclusion post-symptoms
Hand hygiene essential
Notify Public Health if required
Food handlers: longer exclusion

Definitions

Episodes of diarrhoea can be classified into several categories:

Acute diarrhoea: Three or more episodes of partially-formed or watery stool in a day, lasting for less than 14 days
Persistent diarrhoea: Acutely starting episode lasting more than 14 days
Dysentery: Loose stools with blood and mucus often with pyrexia and abdominal cramps (caused by Campylobacter, E. histolytica, E. coli, Salmonella, Shigella)
Traveller's diarrhoea: Diarrhoeal disease during/after foreign travel (commonly caused by E. coli, Salmonella, Viruses, Cryptosporidium, Giardia)
Antibiotic-associated diarrhoea: Diarrhoea during/recently after antibiotics (commonly C. difficile)
Food poisoning: Diarrhoea and vomiting with rapid onset (<24hr duration) from preformed toxins (Staph aureus, B. cereus, C. perfringens)

Causes

Viruses

Rotavirus - Most common infantile cause (reduced since vaccine introduction). Symptoms: watery diarrhoea, vomiting (± fever/abdo pain) resolving in 5-7 days
Norovirus - Most common adult cause (England/Wales). Symptoms: sudden nausea → projectile vomiting + watery diarrhoea (± fever/headache/myalgia) lasting 12-60hr
Adenovirus - Common in children
Hepatitis A - From contaminated water/food

Bacteria

Campylobacter - Most common bacterial cause in UK (undercooked poultry, unpasteurized milk). Symptoms: diarrhoea (may be bloody), nausea, vomiting, abdo cramps, fever. Resolves in 1 week
E. coli (including STEC/VTEC O157) - Undercooked beef, raw produce. Symptoms: bloody diarrhoea, fever, abdo cramps. Usually resolves in 10 days
Salmonella - Eggs, poultry, vegetables. Symptoms: bloody diarrhoea, abdo pain, fever. Resolves in 4-7 days
Shigella - Person-to-person (peak summer). Symptoms: bloody/mucoid diarrhoea, fever, abdo cramps. Resolves in 5-7 days
Yersinia - Common in children. Symptoms: watery/bloody diarrhoea, fever, abdo pain (RLQ pain in older children/adults)

Parasites

Cryptosporidium - Animal/human contact, contaminated water. Symptoms: profuse watery diarrhoea, abdo cramps, nausea, fever
E. histolytica - Travel to endemic areas. Symptoms: mild diarrhoea → severe dysentery (blood/mucus)
Giardia - Faecal-oral, contaminated water (common in travellers). Symptoms: diarrhoea, malaise, abdo pain, bloating, malabsorption

Bacterial Toxins

Staph aureus - Handled foods (meats, cream products). Rapid onset (<6hr), short duration
B. cereus - Reheated rice/pasta. Two forms: emetic (1-5hr) and diarrhoeal (8-16hr)
C. perfringens - Inadequately reheated meats. Symptoms: diarrhoea, abdo cramps (8-16hr)

Clinical Features

Diarrhoea (loose/watery stools ≥3x/24hr)
Nausea and sudden vomiting
Blood/mucus in stool
Fever or malaise
Abdominal pain/cramps

Diagnosis is usually clinical; stool culture rarely needed unless specific indications

Complications

Dehydration/Electrolyte

Acidosis
Circulatory failure
Renal failure
Hypovolaemic shock

Systemic

Bacteraemia/sepsis
HUS (E. coli O157) - AKI, haemolytic anaemia, thrombocytopenia
Reactive arthritis (Salmonella, Campylobacter, Yersinia, Shigella)
Guillain-Barré (Campylobacter)

GI

Colonic perforation (C. difficile, Salmonella, Shigella)
Toxic megacolon (C. difficile, Shigella, CMV, Yersinia)
Intestinal obstruction
Malnutrition
Lactose intolerance

Other complications: Drug malabsorption (antiepileptics, OCP, warfarin), irritable bowel syndrome

Assessment

Assess for:

Dehydration/shock (see tables)
Alternative diagnoses (check vitals, abdominal exam)
Risk factors (age, pregnancy, comorbidities, medications)
Severity (stool frequency, blood, vomiting, intake)
Possible cause (contacts, food/water, travel, antibiotics)

Dehydration Severity in Children

No Dehydration	Clinical Dehydration	Shock
Well appearance Alert Normal urine output Warm extremities Normal skin turgor	Unwell appearance Irritable/lethargic Decreased urine output Sunken eyes Dry mucous membranes Tachycardia	Profound apathy Decreased consciousness Pale/mottled skin Weak pulses Prolonged CRT Hypotension (late)

Dehydration Severity in Adults

Mild	Moderate	Severe
Lassitude Anorexia/nausea Lightheadedness Postural hypotension	Apathy/tiredness Dizziness Headache Muscle cramps Pinched face Dry tongue Tachycardia Oliguria	Profound apathy Confusion/coma Marked vasoconstriction Hypotension Tachycardia Anuria

Management

Hospital Admission Criteria

Emergency admission if: unable to retain fluids, shock, or severe dehydration

Children Admission Criteria

Systemically unwell/severe dehydration
Intractable/bilious vomiting
Painful bloody diarrhoea (STEC suspected)
HUS/sepsis suspected
Deteriorating despite ORS
Risk factors + unable to monitor at home

Adults Admission Criteria

Systemically unwell/severe dehydration
Intractable vomiting/high-output diarrhoea
Suspected sepsis
Inadequate response to ORS
High-risk patients (elderly, comorbidities)
Unable to manage at home

Resuscitation (Shock)

Children

ABCDE approach
IV bolus: 10-20ml/kg NaCl 0.9% + glucose 5% (NICE:20ml/kg, Resus:10ml/kg)
Repeat if shock persists
After shock resolved: Maintenance fluids + deficit replacement (10% deficit in shock, 5% in non-shock)

Adults

ABCDE approach
IV bolus: 500ml crystalloid over <15min
Repeat if shock persists
Further 250-500ml if still shocked + seek help
After shock resolved: Assess fluid/electrolyte needs

Oral Rehydration

Children with Dehydration

Low-osmolarity ORS solution frequently
Discourage juices/carbonated drinks
No solids until rehydrated
After rehydration: Resume normal diet
NICE ORS doses:
- <5yrs: 50ml/kg over 4hr + maintenance
- 5-11yrs: 200ml after each loose stool
- 12-16yrs: 200-400ml after each loose stool

Children without Dehydration

Continue usual feeds/breastfeeding
Encourage fluids
Offer ORS if increased risk

Adults

With dehydration: ORS 200-400ml after each stool
Without dehydration: Encourage fluids + supplements
High-risk adults: ORS as supplemental fluid

Medications

Antidiarrhoeals: Loperamide for mild-moderate cases (avoid in dysentery/VTEC)
Antibiotics: Only for known microbiological causes after specialist advice:
- Campylobacter: Clarithromycin (severe cases)
- Giardiasis: Tinidazole single dose
- Amoebiasis: Metronidazole + diloxanide
- Shigella: Only if severe (specialist advice)
Avoid: Antiemetics, zinc, probiotics (not recommended)

Infection Control

No school/work until 48hr symptom-free
Hand hygiene, flush toilet use
Longer exclusion if specific pathogens

Notify Public Health immediately for: Cholera, bloody diarrhoea, food poisoning, HUS, STEC