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Diarrhoea Flashcards

1
Q

how do the definitions between diarrhoea and gastroenteritis differ?

A

Diarrhoea - subjective
fluidity and frequency

Gastro-enteritis - objective
three or more loose stools/day
accompanying features

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2
Q

what is dysentery?

A

large bowel inflammation, bloody stool

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3
Q

what is the bristol stool chart?

A
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4
Q

what is the epidemiology of gastroenteritis?

A

Contamination of foodstuffs
- Intensively farmed chicken and campylobacter

Poor storage of produce
Bacterial proliferation at room temperature

Travel-related infections e.g. Salmonella

Person-to-person spread
norovirus

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5
Q

what is the most common foodborn pathogen?

A

Campylobacter

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6
Q

what pathogen causes the most hospital admissions?

A

Salmonella

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7
Q

what is the food linked to most cases of food poisoning?

A

Poultry meat

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8
Q

what defences do we have against enteric infections?

A

stomach acidity
antacids and infection

normal gut flora
Cl. difficile diarrhoea

immunity
HIV + salmonella

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9
Q

what are clinical features of non inflammatory/secretory diarrhoea?

A

secretory toxin-mediated
cholera - increases cAMP levels and Cl secretion
enterotoxigenic E. coli (travellers’ diarrhoea)

frequent watery stools with little abdo pain

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10
Q

what is the mainstay of treatment for secretory/inflammatory diarrhoea?

A

rehydration

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11
Q

what is the cause of non inflammatory/secretory diarrhoea?

A

cholera

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12
Q

what is the mechanism of diarrhoea in cholera?

A

Increased cAMP results
in loss of Cl from cells
along with Na and K

Osmotic effect leads to
massive loss of water from
the gut

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13
Q

what are the clinical features of inflammatory diarrhoea?

A

inflammatory toxin damage and mucosal destruction pain and fever
bacterial infection / amoebic dysentery

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14
Q

what is the choice of treatment for inflammatory diarrhoea?

A

antimicrobials may be appropriate but rehydration alone is often sufficient

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15
Q

what is the cause of inflammatory diarrhoea?

A

shigella dystentry

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16
Q

how should a patient with diarrhoea be assessed?

A

Symptoms and their duration
>2/52 unlikely to be infective gastro-enteritis

Risk of food poisoning
Dietary, contact, travel history
assess hydration

postural BP, skin turgor, pulse

features of inflammation (SIRS)
fever, raised WCC

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17
Q

what would be seen in an infant with diarrhoea?

A
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18
Q

what fluid and electrolyte losses result from secretory diarrhoea especially?

[1-7 l fluid per day containing 80-100 mmol Na]

A

Hyponatraemia due to sodium loss with fluid replacement by hypotonic solutions

Hypokalaemia due to K loss in stool (40-80mmol/l of K in stools)

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19
Q

what investigations should be done for a patient with diarrhoea?

A

stool culture +/- molecular or Ag testing

blood culture

Renal function

blood count - neutrophilia, haemolysis (E. Coli O157)

abdominal X-Ray/CT if abdomen distended, tender

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20
Q

what are differential diagnosis for diarrhoea?

A

Inflammatory bowel disease
Spurious diarrhoea -secondary to constipation
Carcinoma

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21
Q

Diarrhoea and fever can occur with sepsis outside the gut, what might be clues for this differential diagnosis?

A

lack of abdo pain/tenderness
goes against gastroenteritis
no blood/mucus in stools

22
Q

what is the treatment for gastro-enteritis?

A

Rehydration - iv or oral?

Oral rehydration with salt/sugar solution
iv saline

23
Q

what is campylobacter gastroenteritis, and what is associated with it?

A

Up to 7 days incubation so dietary history may be unreliable

Stools negative within 6 weeks

abdominal pain can be severe

<1% invasive
Post-infection sequelae
Guillain-Barre syndrome, Reactive arthritis

24
Q

what routine bacterial cultures are available?

A

selective and enrichment methods of culture necessary - variety of media and incubation conditions

takes 3 days to complete all tests

[molecular and antigen detection]

25
what are the two spaces of campylobacter that cause most infections?
specialised culture conditions Two species cause most infections: C. jejuni (90%) C. coli (9%)
26
what is salmonella gastroenteritis and what is associated with it?
symptom onset usually <48 hrs after exposure diarrhoea usually lasts <10 days <5% positive blood cultures 20% patients still have positive stools at 20/52 Prolonged carriage may be associated with gallstones Post-infectious irritable bowel is common
27
what is the routine bacterial culture for salmonella?
2 species in genus: S.enterica S.bongori >2500 serotypes with individual names - most are S.enterica species traditionally named after place of first isolation eg Sandiego, Panama, Derby screened out in lab as ‘lactose non-fermenters’ – look alike microscope - then antigen (O and H) and biochemical tests
28
what are the most common salmonella infections in the UK?
Salmonella enteritidis and Salmonella typhimurium
29
what is ecoli?
Infection from e.g. contaminated meat or person-to-person spread (low incoulum) Typical illness characterised by frequent bloody stools E. coli O157 produces Shiga toxin (same toxin also produced by Shigella spp) (previously called verocyto- toxin) E. coli O157 stays in the gut but the toxin gets into the blood toxin can cause hemolytic-uraemic (HUS) syndrome (haemolytic anaemia and renal failure)
30
what is HUS characterized by?
renal failure, haemolytic anaemia and thrombocytopenia. Treatment supportive – antibiotics NOT indicated
31
what is the mechanism behind HUS?
Toxin stimulates platelet activation micro-angiopathy results
32
what are different species of shigella?
(4 species S. sonnei, S.flexneri, S.boydii, S. dysenteriae) – outbreaks of Shigella sonnei in children’s nurseries
33
what are other forms of ecoli?
enteroinvasive enteropathogenic enterotoxic (traveller’s diarrhoea)
34
what can occasionally cause outbreaks of food poisoning?
Staph aureus (toxin) Bacillus cereus (re-fried rice) Clostridium perfringens (undercooked meat/cooked food left out - toxin accumulates in spore formation)
35
when are antibiotics indicated?
Indicated in gastroenteritis for immunocompromised severe sepsis or invasive infection chronic illness e.g. malignancy Not indicated for healthy patient with non-invasive infection
36
what is clostridiodes difficile diarrhoea?
Patient usually gives history of previous antibiotic treatment – the “4 C antibiotics” Severity ranges from mild diarrhoea to severe colitis C. Diff produces enterotoxin (A) and cytotoxin (B) (inflammatory)
37
what is clostridiodes difficile treated with?
metronidazole oral vancomycin Fidaxomicin (new and expensive) Stool transplants surgery may be required
38
how is CDI prevented?
Reduction in broad spectrum antibiotic prescribing Avoid 4 Cs – cephalosporins, co-amoxiclav, clindamycin, ciprofloxacin Antimicrobial Management Team (AMT) and local antibiotic policy Isolate symptomatic patients Wash hands between patients (spores resist alcohol rubs) – contact precautions Cleaning environment
39
how is CDI managed?
Stop precipitating antibiotic (if possible) Follow published treatment algorithm – oral metronidazole if no severity markers Oral vancomycin if 2 or more severity markers
40
how are parasites diagnosed?
Protozoa and helminths Diagnosis generally by microscopy Send stool with request “parasites, cysts and ova please” or P, C and O
41
what are examples of UK parasites?
Giardia duodenalis (aka G. lamblia/G. instestinalis) - cysts/trophozoites Cryptosporidium parvum
42
what symptoms are caused by Giardia duodenalis (aka G. lamblia/G. instestinalis) - cysts/trophozoites?
diarrhoea, gas, malabsorption, failure to thrive
43
how are Giardia duodenalis (aka G. lamblia/G. instestinalis) - cysts/trophozoites transmitted?
direct contact with cattle/cats/dogs/other people food/water contaminated with faeces
44
how are Giardia duodenalis (aka G. lamblia/G. instestinalis) - cysts/trophozoites diagnosed?
Cysts seen on stool microscopy Trophozoites – duodenal biopsy ‘tightly bound to villi’ or string test
45
what is mechanism of transmission for protozoa?
Carried by >150 species of mammals (cats/dogs/cattle/deer/rabbits…) 20 species known to infect humans Diarrhoea, nausea and vomiting, abdo pain Infected animals/faeces - contaminated water /food – need only 9 oocysts for infection (a stool = 1 million)
46
how is Cryptosporidium parvum diagnosed?
oocysts seen on microscopy
47
how is Cryptosporidium parvum treated?
no specific treatment usually required
48
ntamoeba histolytica amoebic dysentery (instestinal amoebiasis) Invasive extraintestinal amoebiasis (liver/pleuropulmonary/brain abscess) – months/years later – usually no bowel symptoms
Microscopy: trophozoites in symptomatic patient - “hot stool”; asymptomatic patient-cysts seen in formed stool Antibody detection (serum) – for invasive disease Intestinal disease: metronidazole + luminal agent to clear colonization
49
liver abscess pus known as?
amoebic liver abscess - long term complication (“anchovy pus”)
50
rotavirus
Rotavirus in children under 5 yrs common in winter – previously estimated 55000 cases/yr Scotland 1465 laboratory reports in Scotland in 2011 diagnosis by antigen detection in stool rotavirus vaccine introduced July 2013 in UK, 8+12 weeks
51
norovirus?
diagnosis by PCR very infectious -18 virus particles (1g stool=5 billion infectious doses) ward closures common – staff and patients affected strict infection control measures needed Noroviruses - previously known as small round structured viruses (SRSV) Norwalk like viruses (Norwalk,Ohio) Winter vomiting disease – diarrhoea and vomiting common cause of outbreaks Institutions: hospital, community (schools, care homes), cruise ships In Scotland between 1.5 and 3.5 thousand cases/year

Infection (14 decks)

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