Pyrexia of Unknown Origin Flashcards
What is the definition of a fever?
Elevation of body temperature above normal
How does body temperature vary over the course of the day?
Low in the early morning and high in the early evening
What are pyrogens?
Substances which cause fever
Give examples of pyrogens and how they work?
- Endogenous e.g. cytokines
- Exogenous e.g. endotoxins from G -ve bacteria
- Act of hypothalamic thermoregulatory centre to cause reduced heat loss and hence fever
What is the Petersdorf and Beeson definition of pyrexia of unknown origin?
- Temp > 38.3C
- Recorded on multiple occassions
- Present for at least three weeks
- Defied diagnosis after one week of hospital evaluation
What is the modern definition of pyrexia of unknown origin?
No diagnosis after
- 3 outpatient visits
- 3 days in hospital
- 1 week of outpatient investigation
What is the definition of nosocomial PUO?
PUO developed in hospital which is undiagnosed after 3 days
What is the definition of neutropenic PUO?
Undiagnosed fever on a patient with neutrophils <500m3
What is the definition of HIV associated PUO?
Fever in a patient with HIV infection which is present and undiagnosed for more than three days in an inpatient or four weeks in an outpatient
What are the most common causes of classical PUO?
Infection, malignancy, inflammatory and no diagnosis
What are the commonest causes of HIV - related PUO?
Mycobacterium tuberculosis, mycobacterium avium, more than one causative disease and unknown.
How can PUO be assessed?
History: travel, occupation, hobbies, FH, PMH, drug history and pattern of fever
Exam: include skin, eyes, oral cavity, nails and lymph nodes
What initial investigations can be done for PUO?
CXR, urinalysis + microscopy, FBC, WCC, CRP + ESR, blood cultures, U&Es, creatinine and LFTs
List the indications for further investigations for PUO
- Tropical travel: blood for malaria, dengue and HIV and bone marrow for leishmaniasis
- New Murmur: ECHO
- Headaches: temporal artery biopsy
- Micro Haematuria: auto antibodies +/- renal biopsy and USS
- TB Contact: sputum smear, bone marrow and mantoux
- Drug Misuse: BBV screen
Which imaging techniques can be used for PUO?
-White cell scan
-CT
CT PET
-USS
Which invasive investigations can be used to try and diagnose PUO?
Biopsy: bone marrow and liver are common as part of a blind investigation
What are the management options for PUO?
Therapeutic trial
- Rarely used
- Suspected TB infection: anti-TB therapy
- Suspected vasculitis or connective tissue disorder: steroids
What is a fabricated fever?
- Fever is real but self induced
- Self injection is common
- Microbiology may be biggest clue
- Patient may continue despite being very sick
- Needs psychiatric expertise
What are the potential outcomes of PUO?
- Spontaneous resolution (commoner in young patients)
- Some patients respond to NSAIDs or steroids
- Regular re-appraisal required
