Gastro Flashcards
What are the defence mechanisms of the GI microbiome?
Intestinal microflora:
- prevent infection by interfering and competing with pathogens
- produce its own antibacterial substances
Gastric acid kills most organisms that are swallowed
Bile has antibacterial properties
What is diarrhoea?
The passage of loose or watery stools, typically at least three times in 24hrs.
What are the types of diarrhoea?
Acute - 14 days or fewer in duration
Persistant diarrhoea - 14-30 days duration
Chronic diarrhoea - >30 days duration
What are the causes of diarrhoea?
Infective: intraluminal infection, systemic infections (sepsis, TSS, tropical infections, COVID)
Non-infective: cancer, chemical (poisoning, sweeteners, medications), IBD, IBS/malabsorption, endocrine (thyrotoxicosis), radiation
What are the characteristics and causes of watery diarrhoea?
Non-inflammatory
Infection in proximal small bowel
Bacteria implicated: vibrio cholerae, E. coli, Clostridium perfringens, Bacillus cereus (reheated rice), S. aureus, C. difficile
Viral causes: Rotavirus, norovirus
Parasitic: Giardia, Cryptosporidium
What condition is associated with rice water diarrhoea?
V. cholerae infection
What is dysentery?
bloody diarrhoea
What is H. pylori?
Gram -ve rod, commensal bacteria, usually asymptomatic acquisition
What conditions are caused by H. pylori?
Peptic ulcer disease (PUD), chronic gastritis, gastric adenocarcinoma, gastric mucosal lymphoma
What is the pathophysiology of H. pylori infection?
- H. pylori synthesises urease, an enzyme which produces ammonia
- Ammonia damages the gastric mucosa as well as neutralising the protective stomach acid which allows the organs, to survive in the stomach
What are the diagnostic tests for H. pylori infection?
Biopsy
Stool antigen
C-urea breath test
What is the treatment for H. pylori infection?
Triple therapy: clarithromycin, amoxicillin, PPI (lansoprazole, omeprazole)
What is E. coli?
Gram -ve rod, often commensal bacteria
Most strains are harmless but some serotypes are pathogenic:
- ETEC (EnteroToxigenic), EAEC (EnteroHaemorrhagic), EPEC (EnteroPathogenic) → watery diarrhoea
EHEC (EnteroHaemorrhagic) → bloody diarrhoea
Serotype 0157:H7 → Haemolytic Uremic Syndrome
( → haemorrhagic diarrhoea + nephritic syndrome)
What is the treatment for E. coli?
Amoxicillin, trimethoprim, nitrofurantoin
What is C. difficile?
Gram +ve spore-forming, toxin-producing bacteria
Mainly induced w/ antibiotics (ciprofloxacin, co-amoxiclav, cephalosporins, clindamycin)
What is the pathophysiology of C. difficile infection?
Causes pseudomembranous colitis
- Normal GIT flora killed by antibiotics and C. difficile replaces them
- Results in dangerous severe diarrhoea (very watery; ↑↑dehydration)
Highly infectious
What is the treatment for C. difficile?
Stop using C-antibiotics (ciprofloxacin, co-amoxiclav, cephalosporins, clindamycin)
Give vancomycin
Which bacteria cause dysentry?
C - Campylobacter
E - E. coli
S - Shigella
S - Salmonella
What factors are essential to refer to in the history for GI infections?
Onset/duration
Characteristics of stool
Food/drink
Travel
Immune status
Unwell contacts
Hobbies + fresh water
Animal contact
Medications
What are the indications for testing in GI infections
Severe illness: signs of hypovolemia, severe abdo pain, hospitalization
Bloody diarrhoea+ mucus
High-risk host: Age ≥70 years, immunocompromising condition , IBD , pregnancy
Symptoms persisting for more than one week
Public health concerns (eg, diarrhoeal illness in food handlers, HCW, individuals in day care centers)
What can be tested in a stool sample?
Microscopy
Culture
Multi-pathogen molecular panels (GE PCR panel)
Ova, cysts and parasites x3
Toxin detection (C difficile)
What is Acute Cholecystitis?
Gallbladder inflammation caused by cystic duct obstruction by gall stones
What are the symptoms of acute cholecystitis?
Right upper quadrant or epigastric pain, fever and leukocytosis
What is the diagnostic test for acute cholecystitis?
USS