Gastroenteritis

 

• Background

  Pathogens

  • Viral: Norovirus (with Norwalk virus being the only species), Rotavirus, Astrovirus, Adenovirus.
  • Bacteria: Campylobacter jejuni, Salmonella (usually S. enteritidis), Shigella, E. coli, Vibrio cholera, Clostridioides difficile.
  • Protozoa: Giardia, Cryptosporidium, Cyclospora, Entamoeba. See protozoal infections.

  Transmission

  • Most are faecal-oral, and can be person-to-person, foodborne, or waterborne.
  • Some are zoonotic e.g. 1/4 Salmonella cases in kids are from pet reptiles.
  • Campylobacter, Shigella, and Giardia can be sexually transmitted, especially in men who have sex with men.

• Signs and symptoms

  Overview:

  • Acute diarrhoea and/or vomiting is the cardinal feature.
  • Anorexia, malaise, fever, and weight loss are also common.
  • Reliably determining the etiologic agent from clinical history is not usually possible, but the features below may be suggestive.

  Noninflammatory (or noninvasive) diarrhoea:

  • Watery and profuse.
  • Usually due to small bowel infection.
  • Causes: viral, Cholera, Staph. aureus, enteroToxigenic E. coli (Traveller's diarrhoea), Giardia.

  Inflammatory (or invasive) diarrhoea:

  • Tenesmus, abdominal pain, and fever.
  • Presence of blood (rare) = dysentery.
  • Usually due to large bowel infection.
  • Causes, CCESSPIT: Campylobacter, C. diff, E. coli O157 (aka enterohemorrhagic E. coli [EHEC] or Shigatoxigenic E. coli [STEC]), Salmonella, and Shigella Produce Inflammatory Turds.

  Pathogen-specific features:

  • Norovirus: highly infectious, often causing institutional outbreaks e.g. hospitals, cruise ships. Vomiting is predominant. 12-48 hour incubation and infectious up to 48 hours post-symptoms.
  • Campylobacter: common cause of bacterial gastroenteritis, usually from eating infected poultry.
  • Salmonella: usually from eating infected poultry, eggs, or milk.
  • Staph. aureus and Bacillus cereus cause symptoms, often vomiting, within 6 hours of exposure.
  • V. cholera: profuse watery diarrhoea. A common cause of infant mortality in the developing world.

• Differential diagnosis

  Remember that fever plus D+V does not always equal gastroenteritis. D+V can be a feature of sepsis and many other infections e.g. CNS, urinary, appendix.

• Investigations

  • Most cases require minimal if any investigation.
  • Stool culture and microscopy if there is bloody stool, the patient is immunosuppressed, there is recent travel to the developing world, or symptoms are prolonged (>7 days).
  • Basic bloods if unwell: FBC (↑WBC), U&E (dehydration), CRP, LFT (differential).

• Management

  Most gastroenteritis does not require admission and can be managed at home with regular oral fluid intake.

  Inpatient management:

  • Fluids, PO or IV.
  • Anti-emetics and anti-diarrhoeals if severe, but do not give in dysentery.
  • Antibiotics only if systemically unwell or immunosuppressed. Ciprofloxacin (Campylobacter, Salmonella, Shigella) or tetracycline (V. cholera).

  Infection control:

  • Isolate inpatients with D+V.
  • Any food poisoning or suspected food poisoning is a notifiable disease.

• Complications

  • Lactose intolerance.
  • Guillain-Barré syndrome.
  • Reactive arthritis.
  • Haemolytic uraemic syndrome after E. coli O157.

• Clostridioides difficile infection

  Pathophysgiology

  • C. difficile is a Gram +ve anaerobic bacillus that can cause severe gastroenteritis.
  • Transmitted by spores from people or the environment.
  • Often follows antibiotic course, especially clindamycin, quinolones, or cephalosporins, which eliminate gut commensals and allow C. diff to proliferate. Usually 4-9 days after starting, but can be up to 8 weeks.

  Presentation

  • Profuse watery diarrhoea. Bloody stool can occur but is rare.
  • Abdominal pain and tenderness.
  • Fever
  • Complications: pseudomembranous colitis, toxic megacolon.

  Investigations

  • ↑WBC, sometimes very elevated. ≥15 = severe C. diff.
  • U&E. AKI = severe C. diff.
  • Stool PCR ± toxin immunoassay to confirm.

  Management

  • Stop any antibiotics which may be causing it.
  • Non-severe and severe: vancomycin PO 1st line, fidaxomicin PO if vancoymcin ineffective.
  • Life-threatening (shock, ileus, or megacolon): vancomycin PO/PR ± metronidazole IV. May need colectomy if there is toxic megacolon.
  • Consider faecal microbiota transplantation for recurrent disease.