Diarrhoea Summary

Definition & Classification

  • Acute: <14 days
  • Persistent: 14-28 days
  • Chronic: >28 days
  • ≥3 loose/liquid stools per day

Key Investigations

  • Stool microbiology if red flags
  • FBC, U&E if severe illness
  • Coeliac serology if chronic
  • Inflammatory markers

Dehydration Assessment

  • Mild: Lassitude, anorexia
  • Moderate: Dizziness, dry tongue
  • Severe: Shock, confusion
  • Check skin turgor, eyes, BP

Management

  • Oral rehydration therapy
  • IV fluids if severe dehydration
  • Avoid antimotility drugs in infection
  • Treat underlying cause

Red Flags

  • Blood/pus in stool
  • Severe dehydration
  • Fever >38.5°C
  • Weight loss
  • Recent antibiotics/hospitalization

C. difficile Management

  • Mild-moderate: Vancomycin 125mg QDS
  • Alternative: Fidaxomicin 200mg BD
  • Stop causative antibiotics
  • Monitor for complications

Diarrhoea

Definition

Diarrhoea is a symptom, of which there are many causes. The World Health Organization defines diarrhoea as 'the passage of three or more loose or liquid stools per day (or more frequent passage than is normal for the individual)'.

  • Acute diarrhoea: Lasting less than 14 days
  • Persistent diarrhoea: Lasting more than 14 days
  • Chronic diarrhoea: Lasting more than 4 weeks

Mechanisms of Diarrhoea

Osmotic Diarrhoea

  • Soluble compounds draw fluid into intestinal lumen
  • Causes: osmotic laxatives, magnesium antacids, sugar alcohols (mannitol, sorbitol, xylitol)
  • Also seen in malabsorption (coeliac disease, pancreatic insufficiency)

Secretory Diarrhoea

  • Increased secretion with decreased absorption
  • Causes: infections (V. cholerae, E. coli, C. difficile), bile salts, drugs (laxatives, diuretics, theophylline)

Inflammatory Diarrhoea

  • Mucosal damage affects absorption
  • Causes: infections (Shigella), IBD (ulcerative colitis, Crohn's)

Increased Motility

  • Increased frequency without increased volume
  • Causes: endocrine disorders (diabetes, hyperthyroidism)

Causes

Acute Diarrhoea

  • Viral: Norovirus, sapovirus, rotavirus
  • Bacterial: Salmonella, Campylobacter, Shigella, E. coli, C. difficile
  • Parasitic: Cryptosporidium, Giardia, E. histolytica
  • Drugs: Laxatives, antibiotics, PPIs, NSAIDs, SSRIs
  • Other: Anxiety, food allergy, appendicitis, intestinal ischaemia

Chronic Diarrhoea

  • Irritable bowel syndrome
  • Inflammatory bowel disease
  • Microscopic colitis
  • Coeliac disease
  • Malabsorption (lactose intolerance, pancreatic insufficiency)
  • Colorectal cancer
  • Bile acid diarrhoea
  • Drugs
  • Constipation with overflow

Assessment

Key Questions

  • Onset, duration, frequency and severity
  • Presence of red flag symptoms
  • Features suggesting infection (fever, vomiting, contacts)
  • Travel history and exposures
  • Risk factors (food handlers, nursing home residents)

Dehydration Assessment

Mild Dehydration Moderate Dehydration Severe Dehydration
Lassitude Apathy/tiredness Profound apathy
Anorexia, nausea Dizziness, headache Weakness
Lightheadedness Muscle cramps Confusion, coma
Postural hypotension Pinched face, dry tongue Shock
Usually no signs Sunken eyes, reduced skin turgor Tachycardia
Postural hypotension SBP <90 mmHg
Oliguria Oliguria/anuria

Examination

Investigations

Stool Microbiology Indications

  • Systemically unwell/hospital admission needed
  • Blood/pus in stool
  • Immunocompromised
  • Recent antibiotics/PPI/hospital stay (test for C. difficile)
  • Foreign travel (test for ova/cysts/parasites)
  • Persistent diarrhoea (≥2 weeks)
  • High-risk individuals (food handlers, healthcare workers)
  • Suspected outbreaks

Acute Diarrhoea

  • Stool microbiology if indicated
  • Consider FBC, U&E if severe illness

Chronic Diarrhoea

  • FBC (anaemia)
  • U&E, LFTs, calcium
  • Vitamin B12, folate, ferritin
  • TFTs, ESR/CRP
  • Coeliac serology (IgA tTG/EMA)
  • Stool tests if infection suspected

Management

Emergency Admission Criteria

  • Unable to retain oral fluids due to vomiting
  • Severe dehydration or shock

Consider admission also for: Elderly (>60), poor home support, fever, bloody diarrhoea, severe pain, high-risk comorbidities

General Management Principles

  • Oral rehydration therapy for mild-moderate dehydration
  • IV fluids for severe dehydration/shock
  • Treat underlying cause when identified
  • Avoid antimotility drugs in infectious diarrhoea

Antibiotic-Associated Diarrhoea (C. difficile)

  • Risk factors: Age >65, comorbidities, prolonged hospitalization, antibiotics (clindamycin, cephalosporins, fluoroquinolones)
  • Severity:
    • Mild: WCC normal
    • Moderate: WCC <15
    • Severe: WCC >15 + fever >38.5°C
    • Life-threatening: hypotension, ileus, toxic megacolon
  • Treatment:
    • Mild-moderate: Vancomycin 125mg QDS for 10d
    • Alternative: Fidaxomicin 200mg BD for 10d

Summary

  • Diarrhoea is defined as ≥3 loose/liquid stools per day
  • Classify as acute (<14d), persistent (14-28d) or chronic (>28d)
  • Assess for dehydration and red flags (blood, weight loss, fever)
  • Send stool tests if systemic illness, blood, immunocompromised or recent antibiotics/hospitalization
  • Admit if severe dehydration/shock or unable to maintain oral intake
  • For C. difficile, stop causative antibiotic if possible and treat with vancomycin/fidaxomicin