clinical and laboratory aspects of diarrhoea Flashcards
gastro enteritis
three or more loose stools in 24 hrs at least one:
fever, vomiting, pain , blood
dysentery: large bowel inflammation, bloody stools
campylobacter
types of diarrhoea
non inflammatory/secretory -cholera & enterotoxigenic E coli secetory toxin mediated frequent watery stools with littleabdominal pain rehydration mainstay of therapy increased CAMP levels and Cl- secretion
inflammatory
o Shigella dysentery
♣ inflammatory toxin damage and mucosal destruction pain and fever
o bacterial infection/amoebic dysentery
antimicrobials may be appropriate but rehydration alone is often sufficient
mixed- C difficile
assessing patient
symptoms and duration
risk of food poisioning
assess hydration- postural BP, skin turgor
investigations
stool culture
blood culture
renal function-electrolyte balance
blood count-neutrophilia-haemolysis
Ddx
• Inflammatory bowel disease (more than 2 weeks history of symptoms should suggest)
• Spurious diarrhoea – secondary to constipation
• Carcinoma
• Diarrhoea and fever can occur with sepsis outside the gut
o lack of abdo pain/tenderness
o no blood/mucus in stools
non specific management
rehydration antimicrobials? not routinely given the potential for the development of antimicrobial resistance or side-effects (C.diff), does not justify treatment, except if: ♣ systemic involvement ♣ immunocompromised ♣ severe sepsis or invasive infection ♣ valvular heart disease ♣ chronic illness diabetes
campylobacter G.enteritis
most common cause o chickens, contaminated milk, puppies isolated cases rather than outbreaks• Routine culture: o Takes ~3days to complete all tests under specialised culture conditions o (C. jejuni/ C. coli) o Stools negative within 6 weeks -abdominal pain severe -self limiting -erythromycin
salmonella g.e
contact with reptiles <48hrs after exposure diarrhea<10 days positive stools at 20 weeks gallstone assoc. hard to diff with campylobacter routine bacterial culture: screened out as lactose non fermenters -commonest isolates salmonella enteritidis salmonella typhimurium
E coli 0157
• Infection from contaminated meat or person-to-person spread
• The incubation period is between 1 and 7 days.
• Typical illness characterised by frequent bloody stools
• E. coli O157 produces shiga-like toxin
o E. coli O157 stays in the gut but the toxin produced enters the bloodstream
o Toxin can cause hemolytic-uraemic (HUS) syndrome (haemolytic anaemia and renal failure)
♣ 5-7 day between onset of diarrhoea and HUS
♣ Toxin binds to globotriaosylceramide
♣ Platelet activation stimulated micro-angiopathy results
♣ Attachment to endothelial, glomerular, tubule and mesangial cells
♣ HUS is treated by dialysis if necessary and may be averted by plasma exchange.
Antibiotics should be avoided since they can stimulate toxin release
other bacteria
• Several other forms of E. coli cause diarrhoea:
o Enteropathogenic
o Enterotoxic (traveller’s diarrhoea)
o Enteroinvasive
o Routine diagnosis of these strains not possible – only O157 is easily distinguished from others
clostridium difficile diarrhoea
• usually gives history of previous antibiotic treatment
• Severity ranges from mild diarrhoea to severe colitis
• C. Diff produces enterotoxin (A) and cytotoxin (B) (inflammatory)
• Treatment with:
o Oral metronidazole
o Oral vancomycin
o Surgery may be required
o Stool transplants
-psedomembranous colitis
Antibiotics to avoid
o Reduction in broad spectrum antibiotic prescribing
♣ Avoid 4 Cs – cephalosporins, co-amoxiclav, clindamycin, ciprofloxacin, (+ clarithromycin?)
management
• CDI management:
o Stop precipitating antibiotic (if possible)
o Follow published treatment algorithm – oral metronidazole if no severity markers
o Oral vancomycin if 2 or more severity markers
♣ Grampian C.diff severity markers:
• Temperature >38.5°C
• Consider severe co-morbidities/immunodeficiency
• Suspicion of pseudomembranous colitis, toxic megacolon, ileus
• Evidence of severe colitis on CT scan/x-ray
• White blood cell count >15 x 109cells/L
• Acute rising creatinine >1.5 x baseline
UK parasites
giardia lamblia
♣ contaminated water
♣ diarrhoea, malabsorption and failure to thrive
♣ vegetative form in duodenal biopsy or “string test”
♣ cysts seen on stool microscopy
♣ treat with metronidazole
o Cryptosporidium parvum
♣ first recognised in AIDS consider immunocompromised
♣ contaminated water (animal faeces; cattle the principle reservoir)
♣ cysts seen on microscopy
♣ No treatment
• Imported parasites:
o Entamoeba histolytica - amoebic dysentery
♣ vegetative form in symptomatic patient - (“hot stool” diagnosis)
♣ may mimic ulcerative colitis
♣ cysts seen in asymptomatic patient
♣ amoebic liver abscess may be long term complication (“anchovy pus”)
♣ treat symptomatic disease with metronidazole and furamide for cyst carriage
viral diarrhea
rotavirus
major cause of diarrhea in children under 5
-common in winter
-fecal oral transmission
o infects mature enterocytes of villous body and tip (not crypts) leading to cell death and lactose intolerance.
• Noroviruses - previously known as small round structured viruses (SRSV)
o Winter vomiting disease
o Incubation period is 24–48 hours
o Common cause of outbreaks – hospital, community, cruise ships
o Very infectious – contact and aerosol
♣ ward closures common – staff and patients affected
♣ strict infection control measures needed
o Diagnosis: PCR
