fever of unknown origin Flashcards
What is normal temperature range?
Define fever/ febrile illness
Fever and febrile illness is any temperature over 38 degrees (but be aware of natural variation).
36.5- 37.2 degrees normal range
Define pyrexia (or . fever) of unknown origin (1961 definition)
Temp of greater 38.3 (on 1 reading)
and no diagnosis after 3 weeks or 1 week of hospital tests
(found often linked to systemic infections e.g. endocarditis and cancers/ autoimmune diseases).
What is the modern term for fever of unknown origin?
Acute undifferentiated febrile illness
temp > or eqqual to 38 degrees celcius
and no organ focus
and less than 2 weeks duration
what are the common causes of fever of unknown origin?
Although the definition describes fever of unknown origin as having no particular focus, this is often as clinicians cannot identify the focus.
Occult infections (hidden infections): endocarditis, liver abscess, biliary, UTI, LRTI etc..
protozoa: malaria, (leishmaniasis, trypanosomiasis)
bacteria: enteric fever, tuberculosis, Q fever, (brucellosis )
subsection of bacteria= Spirochaetes: leptospirosis, (relapsing fever)
Rickettsia: typhus (louse, flea, tick, mite born)
Arboviruses: dengue
Other viruses: EBV, CMV, HIV, viral hepatitis
non infectious causes: malignancy, autoimmune disease, heat illness
What are key questions to ask if someone has returned from travelling?
Where and when?
Activities and exceptions?
accommodation and transport?
food and water?
insects and animals?
sexual contacts and drugs / needles/ blood products
freshwater exposure and bare skin contact with the ground?
precaution and prophylaxis?
others affected?
Always think about incubation periods and speed of onset of symptoms
How might you go about diagnosing the cause of fever of unknown origin?
focus on the symptoms –> they may seem non specific but every component is important
e.g. immunocompromised patient and overseas travel
Think about incubation periods and speed of onset of the symptoms
examination remains very important (and confirm objective fever)
What laboratory investigations might you do to elucidate cause of FUO?
What would some of these results potentially mean?
- urinanalysis –> haematuria/ proteinuria/ WBCS
- FBC:
- often ↓ Hb in chronic infections
- ↑ neutrophils in bacterial infections
- ↑↓ lymphocytes in viral infections
- ↓ platelets in malaria and some viral infections
- ↑ platelets in some bacterial infections and inflammatory disorders
- U and E: acute kidney injury in some infections/ sepsis
- LFT: hepatitis in some infections
- CRP: acute marker of bacterial infection
- ESR: chronic marker of bacterial infections and inflammatory disorders
- Lactate : marker of tissue hypoperfusion and severe sepsis
- Auto-antibodies: markers of autoimmune inflammatory disorders
What are some of the microbiologi investigations that could be done to diagnose cause of FUO?
Blood cultures (+/- mycobacterial blood cultures)
urine microscopy, culture and sensitivities
faeces microscopy, culture and sensitivities
malaria blood films and antigen tests (2-3 tests, each 12-24 hours apart)
serology tests: viral, rare, imported and tropical infections
PCR tests: increasingly used for viral and rare infections
What imaging investigations might be done to work out cause of FUO?
CXR –> for pneumonia, TB which may not have obvious clnical features
USS abdomen and pelvis –> to look at liverm bilary tract and urinary tract
CT thorax, abdomen and pelvis (TAP) : to look at all central organs
Echocardiogram: to look for heart valve vegetations and damage
PET scan: too look for areas of increased metabolic activity
How long might the diagnosis of the cause of FUO take?
What should be done in the case of life threatening diagnosis?
what should always be considered?
definitive diagnosis of the cause of FUO may take days or weeks to acheive
life threatening diagnosis should be considered for possible empirical treatment
diagnosis of sepsis/ severe sepsis must also be considered
How might you treat FUO?
if pt meets definition for sepsis they you may be obliged to treat with antibiotics
if they meet definition for severe sepsis then you need to treat with broad spectrum IV antibiotics
Usual approach to managing sepsis will not diagnose or treat malaria, viral infeciton or some rare/ imported/ tropical infections
antibiotic guidelines for treating sepsis will vary between hospitals and if the infection is thought to be opportunistic or hospital acquired
Best approach to take when assessing FUO?
Take a careful history including travel history –> confirm presence of fever, fever patterns, recent residence or travel, conttact with animals, weight loss common in malignancy and endocrine/ HIV infection/ TB, night sweats non specific but can be ass. with autoimmune/ TB/haematological malignancy
Examination –> ausculation of heart to look for mumurs (bacterial endocarditis), ausculatet lungs, bradycardia, abdominal tenderness, palpable lymph nodes, head and neck exam (sinusistis/ oral lesions), inflammation of joints, rashes/ skin lesions
Investigation –> FBC/ U&E’S/ LFT/ ESR/ Urine and blood culture. Chest radiography, biopsy of rash or lymph nodes, MRI
Further investigation –> CT of abdomen or pelvis (e.g liver abscess)
