Pyrexia of Unknown Origin Flashcards
Describe the natural variation of body temp
Variation of up to 0.8 degrees daily (circadian rhythm): low in early morning, high in early evening
What are pyrogens? How do they act?
Substances which raise temperature and cause fever
They act at hypothalamus thermoregulatory centre to cause reduced heat loss and hence fever
Give examples of pyrogens
Endogenous - cytokines
Exogenous - endotoxins and gram negative bacteria
Describe the progression of bacterial infection –> septic shock
Suspected bacterial infection –> systemic inflammatory response syndrome –> sepsis (SIRS + evidence) –> severe sepsis (organ under-perfusion) –> septic shock (irreversible hypotension despite fluid resuscitation)
What is the definition of pyrexia of unknown origin (PUO)?
Temp > 38 recorded on multiple occasions +
3 outpatient visits OR
3 days in hospital OR
one week of outpatient investigation
What are the 4 types of PUO?
Classical PUO
Nosocomial PUO (develops in hospital)
Neutropenic PUO (undiagnosed fever in patient with low neutrophils)
HIV associated PUO
During assessment of a patient with PUO, what should history be asked?
Travel Occupation Hobbies FH and age of onset PMH + Past surgical history Drug history
What examination should be done?
Skin, eyes, mouth, nails, lymph nodes
Repeated examination is often worthwhile
What investigations should be done?
CXR Urinalysis, urine microscopy FBC, differential WCC CRP, ESR Blood cultures @ times of fevers Urea, Cr, Electrolytes, LFTs
What indications are there for further investigation + what investigations are they?
Tropical travel - test blood for malarial parasites, HIV etc
New murmur - Echo scan
Headaches - temporal artery biopsy
Micro-haematuria - auto-antibodies +/- renal biopsy, USS
TB contact - sputum smear, mantoux test
Drug misuse - screen for blood borne viruses
What imaging techniques are used in PUO?
USS, CT, MRI, radio-labelled white cell scan, isotope bone scan
Is there treatment for PUO?
Therapeutic trials can be used (rarely)
They are indicated if there is mycobacterial infection, suspected vasculitis or connective tissue disorder
For which condition does the patient recover rapidly with the use of steroids?
Temporal arteritis
What is fabricated/ factitious fever?
Where the fever is real but self induced
Self-injection is common
Psychiatric expertise should be sought
How often does infection contribute to PUO?
infection accounts for less than 1 in 4 cases
other causes: malignancy, inflammatory
