Gastroenteritis

Broad term, but is usually used to refer to an infective illness which causes diarrhoea, vomiting and often abdominal pain

Aetiology

Risk factors

  • Poor sanitation/personal hygiene
  • Immunosuppression e.g. aids
  • Poor food preparation - infection may arise from poorly cooked food, cooked food that has been left too long at room temperature or from uncooked food such as shellfish
  • Age - <5 not breastfeeding, older age
  • Malnutrition
  • Closed communities
  • Acid suppression

Pathophysiology

Viral gastroeneritis

  • Incubation period for viruses is usually about a day
  • Adenovirus
  • Enterovirus
  • Norovirus - highly infectious, explosive D+V, oral-droplet spread with short incubation (< 24h), associated with cruise ships
  • Rotavirus - commonest cause of D+V in children <3 years, self-limiting, associated with fever, associated with cruise ships

Bacterial gastroenteritis

  • Incubation period for bacteria is usually a few hours to four days
Secretory diarrhoea (watery)
  • Clostridium difficile (C. diff)
    • Gram positive spore-baring bacillus which is carried as part of normal bacterial flora, particularly in the elderly and in infants
    • Infection occurs when antibiotics are prescribed that kill off normal competitive bowel flora and allows C. diff to overgrow
    • Produces toxin A (enterotoxin) and toxin B (cytotoxin)
    • Diarrhoea can be bloody
  • Bacillus cereus - associated with starchy foods e.g. reheated rice, presents with profuse vomiting
  • Listeria - associated with unpasteurized milk products, deli counter, can cause meningitis/bacteraemia
  • Vibrio cholerae - profuse secretory diarrhoea (cholera), associated with refugee camps
Inflammatory diarrhoea (bloody stool and fever)
  • Campylobacter jejuni - most common bacterial cause of foodborne gastroenteritis
    • Associated with poultry, unpasteurized milk
    • Common in travel to SE Asia
  • Salmonella - associated with poultry, meat and raw egg
  • Shigella
    • Produces a toxin which binds to receptors (e.g. renal cells, WBCs) - inhibits protein synthesis, leading to cell death
    • Causes bloody diarrhoea
    • Second most common association with HUS
  • E. coli 0157
    • Produces a Shigella-like toxin → bloody diarrhoea
    • Associated with food (beef), person to person transmission, animal contact
    • Most common association with HUS
    • Most common cause of acute traveler’s diarrhoea
  • Vibrio (non-cholera) - associated with seafood
  • Tropical sprue
    • Colonisation by pathogen or alterations in intestinal bacterial flora induced by exposure to another environmental agent
    • Occurs mainly in tropical regions of the Caribbean, India, South Africa and Southeast Asia
    • Presents with diarrhoea and signs of malabsorption (from inflammation) e.g. steatorrhea, weight loss
  • Whipple’s disease
    • Caused by Tropheryma whipplei, increase in the frequency of HLA-B27 antigen
    • Presents with diarrhoea and signs of malabsorption (from inflammation) e.g. steatorrhea, weight loss, other systemic involvement e.g. arthritis
Invasive diarrhoea
  • Yersinia enterocolitica
    • Common with travel to Asia
    • May mimic appendicitis as it may invade mesenteric nodes
  • Salmonella typhi/paratyphi
    • Most common in those returning from the Indian subcontinent and SE Asia, often in people visiting family/friends
    • Causes enteric fever - fever, non-specific symptoms e.g. headache, constipation or diarrhoea, dry cough

Parasites

  • Incubation period for parasites is usually 7-10 days
  • Amoebiasis - entamoeba histolytica
    • Bloody diarrhoea/colitis
    • Beware toxic megacolon
  • Giardiasis - giardia
    • Watery, malodorous diarrhoea
    • Can cause longer term disease e.g. malabsorption

Clinical presentation

  • Epidemics in the UK are usually caused by rotavirus, norovirus is a comon cause of 'winter vomiting'
  • Bloody diarrhoea should arouse suspicion of bacterial infection
    • E. coli O157 especially
    • After return from an exotic location, it may be E. histolytica
    • Salmonella spp. is also a possibility
  • Pyrexia in adults often suggests an invasive organism as the cause

Investigations

  • History - to help identify causative organism
  • Stool culture samples - not routinely performed as does not usually affect management, consider if:
    • Acute painful diarrhoea or blood, mucus and/or pus in the stool (E. coli 0157, C. diff)
    • Patient is systemically unwell or immunocompromised
    • Patient has had recent hospital admission (C. diff)
    • Recent overseas travel
    • Not resolving after 7 days
  • Endosopy + biopsy indicated in some specific cases - if suspect tropical sprue or Whipple's disease

Management

  • Oral rehydration (at home)
  • Antibiotics rarely indicated - can precipitate HUS
  • Anti-diarrhoea drugs rarely recommended - risk of bowel obstruction
  • Admit to hospital if signs of severe dehydration

Pathogen-specific treatment

  • C. diff:
    • Less severe - PO metronidazole
    • Severe - PO vancomycin +/- PO metronidazole
  • Tropical:
    • Metronidazole or tinidazole for parasitic diarrhoea
    • Enteric fever - if severe sepsis IV ceftriaxone

Complications

Hemolytic uremic syndrome (HUS)

  • Group of blood disorders characterized by low RBCs, low platelets, high WBCs and acute kidney failure
  • Most cases occur after infection with E. coli 0157, other causes include Shigella and Salmonella