Gastroenteritis and infective colitis

Question 1

What is gastroenteritis?

Answer 1

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

Question 2

What is the aetiology of gastroenteritis? (x4)

Answer 2

• Viruses: rotavirus, adenovirus, calicivirus, Norwalk virus, small round structured virus
• Bacterial: Campylobacter jejuni, E. coli, Salmonella, Shigella, Vibrio cholerae, Listeria, Yersinia enterocolitica
• Protozoal: Entamoeba histolytica, Cryptosporidium parvum, Giardia lamblia
• Toxins contained in contaminated foods or water

Question 3

What are the toxins that cause gastroenteritis? (x7 +3)

Answer 3

Toxins that come FROM Staph. Aureus (improperly cooked meat, old rice), Clos. Botulinum (canned food), Clos. Perfringens (improperly cooked meat), Bacillus cereus (old rice), Salmonella (eggs and poultry), Listeria and Campylobacter (milk and cheeses), mushrooms, heavy metals, seafood

Question 4

What is the pathophysiology of gastroenteritis? (x2) Which pathogen or toxin (produced by a pathogen) can cause worse disease?

Answer 4

• NON-INFLAMMATORY MECHANISMS: e.g., V. cholerae and enterotoxigenic E. coli produce ENTEROTOXINS that cause enterocytes to secrete water and electrolytes
• INFLAMMATORY MECHANISMS: e.g., Shigella and enteroinvasive E. coli release CYTOKINES and INVADE and damage the epithelium, with greater invasion and bacteriaemia in the cause of Salmonella typhi.

Question 5

What are the risk factors of gastroenteritis? (x5) (How should this inform your history?)

Answer 5

Recent travel, recent antibiotic use, recent intake of at-risk food (enquire about how cooked, source and whether anyone else is ill), poor hygiene, contact history (faecal-oral transmission)

Question 6

What is the epidemiology of gastroenteritis: Where?

Answer 6

Higher prevalence in the developing world – especially Africa.

Question 7

What are the symptoms of gastroenteritis? (x5)

Answer 7

• Sudden onset nausea and vomiting
• Anorexia
• Diarrhoea (bloody or watery)
• Abdominal pain/discomfort
• Fever

Question 8

How does onset of symptoms differ depending on aetiology of gastroenteritis?

Answer 8

If aetiology is from a TOXIN, onset is early (1-24 hours). If aetiology is bacterial/viral/protazoal, onset is 12 hours or later.

Question 9

How may the toxin involved in gastroenteritis affect a patient’s history? (x2 examples)

Answer 9

Botulinum causes paralysis; mushrooms can cause fits, renal or liver failure.

Question 10

What are the signs of gastroenteritis? (x4)

Answer 10

• Diffuse abdominal tenderness
• Abdominal distension
• Bowel sounds increased
• Pyrexia, dehydration, hypotension if severe

Question 11

What are the investigations for gastroenteritis? (x4 (x3 and x6))

Answer 11

• Diagnosis typically done clinically based on signs and symptoms.
• BLOOD: FBC (raised WBC; sometimes low Hb/platelets is haemolytic uraemic syndrome manifests as complication of E. coli), blood culture (helps identification if bacteraemia present), U&Es (dehydration sign)
• STOOL: faecal microscopy for polymorphs (WBCs), parasites, oocysts, culture, electron microscopy (for viral infections), analysis for toxins (especially Clostridium difficile as a differential – infectious colitis)
• AXR: to exclude differentials for abdominal pain
• USS: to exclude differentials for abdominal pain

Question 12

How is gastroenteritis generally managed? (x3)

Answer 12

• Fluid and electrolyte replacement with oral rehydration solution containing glucose and salt. IV rehydration may be necessary if symptoms severe
• Antibiotics ONLY if severe or the infective agent has been identified
• Public Health: often a notifiable disease

Question 13

How is botulism gastroenteritis managed?

Answer 13

Botulinum antitoxin IM and manage in ITU

Question 14

What are the complications of gastroenteritis? (x5)

Answer 14

• Dehydration, electrolyte imbalance, prerenal failure
• Secondary lactose intolerance (particularly in infants)
• Sepsis (particularly Shigella and Salmonella)
• Haemolytic uraemic syndrome in E. coli
• Guilian-Barre syndrome (rapid-onset weakness from autoimmune peripheral nerve damage) weeks following Campylobacter gastroenteritis

Question 15

What is the prognosis of gastroenteritis?

Answer 15

Good as the majority of cases are only self-limiting.

Question 16

What is the difference between gastroenteritis and infectious colitis?

Answer 16

Gastroenteritis refers to inflammation of the gastrointestinal tract, usually the stomach and intestines. Colitis refers to inflammation of the colon. They also differ in their aetiology – as I will discover shortly.

Question 17

What is infectious colitis?

Answer 17

AKA PSEUDOMEMBRANOUS COLITIS. Large bowel inflammation with mucosal destruction and inflammatory exudates forming pseudomembranes on the bowel wall associated with toxin-releasing Clostridium difficile bacilli.

Question 18

What is the aetiology of infectious colitis? (x2 points)

Answer 18

Colonic overgrowth of C. difficile Gram-positive bacteria leading to disturbance of gut microflora, nearly always brought about by antibiotic use. Transmission is also a risk through faecal-oral route, fomites or direct exposure to contaminated environment.

Question 19

What antibiotics are more suggestive of infectious colitis? (x3)

Answer 19

Clindamycin, ampicillin, and broad-spectrum cephalosporins

Question 20

What is the pathophysiology of infectious colitis?

Answer 20

C. difficile releases two potent toxins: toxin A (enterotoxin) and toxin B (cytotoxin). Toxin A inactivates Rho-GTPase (epithelial cytoplasmic protein) causing intestinal hypersecretion, disaggregation of epithelial actin microfilaments and cell death. Both toxins also disrupt intracellular tight junctions and cause an inflammatory response leading to pseudomembrane formation and inflammatory exudates (increased vascular permeability).

Question 21

What are pseudomembranes?

Answer 21

Composed of an exudate made of WBCs, fibrin and mucus and are thin yellowish membrane with intact underlying epithelium.

Question 22

What is the epidemiology of infectious colitis: Population? Hospitals?

Answer 22

C. difficile carried asymptomatically in 2% of the population. Pseudomembranous colitis common in hospitals where there is both increase carriage of C. difficile and antibiotic use.

Question 23

What are the symptoms of infectious colitis? (x2)

Answer 23

Remember it is a large intestine issue, so no upper GI symptoms like vomiting: Watery diarrhoea which may become bloody, and crampy abdominal pain.

Question 24

What are the signs of infectious colitis? (x3)

Answer 24

Pyrexia, abdominal tenderness. In severe cases, toxic megacolon or perforation.

Question 25

What are the investigations for infectious colitis? (x3)

Answer 25

• BLOOD: FBC (increased WCC), high CRP, lactate, blood culture (excludes other organisms)
• STOOLS: demonstration of C. difficile toxin by ELISA. Stool culture only used to exclude differentials
• SIGMOIDOSCOPY: visualises colitis and pseudomembranes

Question 26

How is infectious colitis medically managed? (x2)

Answer 26

• Oral metronidazole or vancomycin. IV in critically ill. Empiric therapy is appropriate (antibiotics before diagnosis)
• Supportive treatment: rehydration and electrolyte imbalance from diarrhoea

Question 27

How is infectious colitis managed after relapse?

Answer 27

Repeat treatment. In second relapse, taper vancomycin over 6 weeks plus probiotics started during final week of vancomycin and continued for two additional weeks.

Question 28

How is infectious colitis surgically managed? Indication?

Answer 28

Subtotal colectomy with ileostomy for patients over 65 with WCC over 20x10^9/L or plasma lactate between 2.2 and 5 mEq/L.

Question 29

What are the complications of infectious colitis? (x3)

Answer 29

Toxic megacolon, perforation, septic shock.

Question 30

What is the prognosis of infectious colitis?

Answer 30

Recovery is prompt with treatment. 25% relapse on stopping treatment.