Pyrexia of unknown origin Flashcards
what is normal body temperature
~37C
variation of up to 0.8C daily, low in early morning, high in early evening
define fever
elevation of body temp above normal
part of the systemic inflammatory response (SIRS)
define pyrogens
substances which cause fever
act at hypothalamic thermoregulatory centre to cause reduced heat loss and therefore fever
examples of pyrogens
endogenous e.g. cytokines
exogenous e.g. endotoxins from gram -ve bacteria
define pyrexia of unknown origin
temp >38C
recorded on multiple occasions
3 outpatient visits or 3 days in hospital or 1wk of outpatient investigation
define nosocomial PUO
develops in hospital
undiagnosed after 3 days
define neutropenic PUO
undiagnosed fever in patient w/ neutrophils <500/mm^3
define HIV associated PUO
fever in patient w/ HIV infection
present and undiagnosed for >3 days as an inpatient or >4wks in outpatient setting
causes of PUO
infections - becoming a less common cause malignancy inflammatory misc/other undiagnosed
causes of HIV related PUO
HIV itself mycobacterium infections tumours and lymphomas multiple causative diseases other
hx of PUO
travel occupation hobbies FHx PMH and surgical hx drug hx pattern of fever
examination of PUO
be thorough
skin, eyes, oral cavity, nails and lymph nodes
repeated examination often worthwhile
initial investigations
simple things first CXR urine analysis and microscopy FBC and differential WCC CRP and ESR (acute phase reactants) blood cultures taken at times of fevers - take at least 3 sets of blood cultures urea, creatinine, electrolytes, LFTs
further investigations - tropical travel
blood for malarial parasites, dengue, HIV, bone marrow for leishmaniasis
less likely if >21 days since return
further investigations - new murmur
echo (trans-oesophageal echo may be needed)
further investigations - headaches
temporal artery biopsy (temporal/cranial/giant cell arteritis)
tenderness over temporal artery
further investigations - microhaematuria
auto-antibodies +/- renal biopsy, (polyarteritis), US (renal Ca)
further investigations - TB contact
sputum smear, bone marrow, mantoux
further investigations - drug misuse
screen for blood borne viruses
PUO imaging
more valuable if they have some “direction”
cannot always differentiate between infection and inflammation
anatomical changes may not develop in immunocompromised hosts (e.g. neutropenic pts and abscesses)
PUO invasive investigations
obtain tissue for culture and histology
bone marrow and liver often examined as part of blind investigation - malignancy, TB, lymphoma
diagnostic laparotomy - rarely necessary
PUO treatment
therapeutic trial
therapeutic trial for PUO
rarely used
suspected mycobacterial infection (anti-TB therapy)
diagnosis of Mtb unlikely if no response to chemotherapy within 2wks
suspected vasculitis or connective tissue disorder (steroids)
response of temporal arteritis to steroids is dramatic - usually within 48hrs
fabricated fever
fever is real but self-induced
self injection common cause
microbiology may be strongest clue in relation to main clinical picture
patient often continues to inject dangerous substances despite being very sick
form of Munchausen’s - psychiatric expertise should be sought rather than direct confrontation
outcome of PUO
spontaneous resolution of PUO commoner in young compared with old patient
some pts w/ no diagnosis respond to NSAIDs or steroids (steroid responsive PUO)
regular re-appraisal required - answer may not become apparent for many months
