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INFECTIOUS DISEASES > Pyrexia of Unknown Origin > Flashcards

Pyrexia of Unknown Origin Flashcards

1
Q

What is the normal body temperature

A

37oC

- BUT has a variation of up to 0.8C daily (circadian rhythm - low to high throughout day))

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2
Q

what is considered to be a fever

A

elevation of the body temp above 37oC

- part of the systemic inflammatory response syndrome (SIRS)

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3
Q

what are pyrogens

A

substances that cause fever

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4
Q

what are the 2 types of pyrogens

A

endogenous - eg cytokines

exogenous - eg endotoxins from gram-ve bacteria

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5
Q

how do pyrogens cause a fever

A

pyrogens act at the hypothalamic thermoregulatory centre to cause reduced heat loss and hence fever

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6
Q

what symptoms are seen in SIRS

A

pulse >90
temp <35 or >38
RR >20
WCC >12 or <5

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7
Q

what are the signs/symptoms of sepsis

A

SIRS + evidence of bacterial infection

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8
Q

what are the signs/symptoms of severe sepsis

A

organ underperfusion - oliguria, confusion, acidosis

ALSO
SIRS + evidence of bacterial infection

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9
Q

what are the signs/symptoms of septic shock

A

irreversible hypotension despite fluid resus

ALSO
SIRS + evidence of bacterial infection
AND
organ underperfusion - oliguria, confusion, acidosis

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10
Q

what is the definition of pyrexia of unknown origin (PUO)

A
  • temp >38.3oC
  • recorded on multiple occasions
  • present for at least 3 weeks

no diagnosis after:

  • 3 outpatient visits OR
  • 3 days in hospital OR
  • one week of outpatient investigation

ie MULTIPLE FEBRILE EPISODES THAT DEFY DIAGNOSIS

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11
Q

what are the 4 types of PUO

A

classical PUO

nosocomial PUO

neutropenic PUO

HIV-associated PUO

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12
Q

what is nosocomial PUO

A

PUO that develops in hospital, undiagnosed after 3 days

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13
Q

what is neutropenic PUO

A

an undiagnosed fever in a patient with neutrophils <500/mm3

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14
Q

what is HIV-associated PUO

A

fever in a patient with HIV infection - present and undiagnosed for more than three days in an inpatient or four weeks in an outpatient

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15
Q

name 2 possible causes of PUO

A

?wound infection

?multiple pulmonary emboli

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16
Q

what bacterium commonly cause HIV-rassociated PUO

A

mycobacterium tuberculosis
mycobacterium avium

COMMONLY ALSO
unknown
more than one causative disease

17
Q

what are the 4 groups of diseases that cause PUO

A

infections (most common - 1in4)
malignancies
autoimmune/inflammatory
other/miscellaneous

18
Q

what aspects of the history are important for PUO

A
  • travel
  • occupation and hobbies (exposure to allergens)
  • family history and age onset - familial fevers e.g. TNF receptor associated periodic syndrome (TRAPS)
  • past medical/surgical history
  • drug history
19
Q

what aspects of the examination are important for PUO

A

BE THOROUGH

  • include skin, yes, oral cavity, nails, lymphs
  • repeated examinations often needed
20
Q

what are the initial investigations that can be done for PUO

A

SIMPLE THINGS FIRST

  • Chest X-Ray
  • Urinalysis and urine microscopy
  • FBC and differential white cell count
  • CRP and ESR
  • Blood cultures taken at times of fevers
  • Urea, creatinine, electrolytes, liver function tests

prolonged cultures often needed

21
Q

how many blood cultures should be taken before ruling out infection

A

3 negative blood cultures

22
Q

what further investigations would a tropical travel history require

A
  • blood: malarial parasites, dengue
    (but less likely if >21 days since return)
  • HIV, bone marrow for leishmaniasis
23
Q

what investigations would a new murmur require

A

ECG (trans-oesophgeal echo may be needed)

24
Q

what investigations would headaches require

A
  • temporal artery biopsy (TA)

- CT PET

25
Q

what investigations would micro-haematuria require

A
  • auto-antibodies +/- renal biopsy (polyarteritis)

- ultrasound (renal Ca)

26
Q

what investigations would TB contact require

A
  • sputum smear
  • bone marrow
  • Mantoux test/skin patch test
27
Q

what investigations would a history of drug misuse require

A

screen for blood borne viruses

28
Q

what are the imaging techniques used in PUO

A
  • contrast CT - FIRST
  • CT PET
  • transoesophageal ECG
29
Q

what can CT PET images show

A
  • looks at uptake of marker - uptake bigger at areas of inflammation
  • shows large vessel vasculitis
  • can be a diagnostic technique
30
Q

what are some limitations of imaging techniques in PUO

A

can’t always differentiate between what is inflamed and what is infected

anatomical changes may not develop in immunocompromised hosts - e.g. neutropenic patients and abscesses

31
Q

what are the invasive investigations used for PUO

A
  • tissue for culture/histology
  • bone marrow/liver/TA biopsy
  • diagnostic laparotomy
32
Q

what do biopsies in PUO most commonly find

A

malignancy, TB, lymphoma

33
Q

what are the treatments for PUO

A

therapeutic trial:

?mycobacterial infection = anti-tuberculous therapy

?vasculitis or conn. tissue disorder = steroids

34
Q

what is a fabricated fever

A

a fever that is real but self-induced

- commonly from self injection

35
Q

what is the strongest clue to diagnose a fabricated fever

A

microbiology - multiple different organisms on blood culture at different times

36
Q

what is important to include if a fabricated fever is suspected in a patient with PUO

A

psychiatric expertise rather than direct confrontation

37
Q

what are the common outcomes of PUO

A

young - spontaneous resolution
elderly - more likely to persist

no diagosis - can still respond well to NSAIDS or steroids (steroid responsive PUO)

regular check ups required

INFECTIOUS DISEASES (15 decks)

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