Gastroenteritis

Question 1

Define

Answer 1

Acute inflammation of the lining of the GI tract, manifested by nausea, vomiting, diarrhoea and abdominal discomfort.

Question 2

Causes

Answer 2

Caused by viruses, bacteria, protozoa, toxins from contaminated food/water

Causes:

1.  Improperly cooked meat (S. aureus, C. perfringens)
2.  Old rice (B. cereus, S. aureus)
3.  Eggs and poultry (Salmonella)
4.  Milk and cheeses (Listeria, Campylobacter)
5.  Canned food (botulism)

Inflammatory mechanisms:

• Release of cytotoxins and invasion of epithelium causing damage and bacteraemia (Shigella, Enteroinvasive E. coli, Salmonella)

Non-inflammatory mechanism:

• Production of enterotoxins that cause enterocytes to secrete water and electrolytes (V. cholerae Enterotoxigenic E. coli)

Question 3

Epidemiology

Answer 3

Common and underreported
~20% of the population every year
Serious cause of morbidity and mortality in the developing world

Question 4

Risk factors

Answer 4

• Recent travel
• Poor personal hygiene/lack of sanitation
• Food intake (e.g. undercooked, contaminated source) Swimming/etc. in contaminated water
• Exposure to others suffering from gastroenteritis Compromised immune system (e.g. AIDS) Achlorhydria (absence of HCl in gastric secretions)

Question 5

Symptoms

Answer 5

↘ Sudden onset nausea, vomiting, anorexia

↘ Diarrhoea (bloody or watery)

↘ Abdominal pain/discomfort

↘ Fever and malaise

Time of onset:
Toxins → early, 1-24 hours

Bacterial/viral → 12 hours or later

Parasites → days

Question 6

Signs

Answer 6

Diffuse abdominal tenderness, abdominal distension

↘ ↑Bowel sounds

↘ If severe – pyrexia, dehydration, hypotension, peripheral shutdown

Assess for features of dehydration

Note: toxins may cause paralysis (botulinum) or fits/renal failure/liver failure (mushrooms)

Question 7

Investigations

Answer 7

• Bloods: FBC, blood culture (identify bacteraemia), U&Es (dehydration)
• Stool: faecal microscopy and analysis for toxins (particularly for the toxin causing pseudomembranous colitis (C. difficile toxin)
• AXR or ultrasound: exclude other causes of abdominal pain (e.g. bowel perforation)
• Sigmoidoscopy: usually unnecessary unless inflammatory bowel disease needs to be excluded

Question 8

Management

Answer 8

• Bed rest
• Fluid and electrolyte replacement with oral rehydration solution (contains glucose and salt)
• IV rehydration may be necessary in those with severe vomiting
• Most infections are self-limiting (so will go away with time)
• Antibiotic treatment is only used if severe or if infective agent has been identified

NOTE: if botulism is present (due to Clostridium botulinum) treat with botulinum antitoxin (IM) and manage in ITU

NOTE: this is often a notifiable disease and is an important public health issue

Question 9

Complications

Answer 9

• Dehydration
• Electrolyte imbalance
• Prerenal failure (due to dehydration)
• Secondary lactose intolerance (particularly in infants)
• Sepsis and shock
• Haemolytic uraemic syndrome (associated with toxins from E. coli O157)
• Guillain-Barre Syndrome may occur weeks after recovery from Campylobacter gastroenteritis

NOTE: botulism can lead to respiratory muscle weakness or paralysis

Question 10

Prognosis

Answer 10

Good prognosis because most cases are self-limiting