Day #31 - Fever of Unknown Origin

Today we discussed a case of true fever of unknown origin.

Epidemiologic Criteria:

• Fever x 3 weeks (38.3)
• Failure to find cause despite appropriate initial outpatient/inpatient investigations

Causes:

• Majority unknown
• Then infection (most commonly TB or occult abscesses), inflammatory, malignancy, other

Diagnostic tests (beyond initial):

• CT abdomen to look for abscess, lymphadenopathy, other pathology. Yield ~20%
  
• Bone scan (insensitive, but specific with good + LR)
• Liver biopsy -- regardless of hepatomegaly or LFT abnormalities has yield ~15%
• Temporal artery biopsy in the elderly -- yield ~ 15%
• Leg dopplers -- yield 2-6%
• Bone marrow biopsy-- in those with cytopenias or compatable syndromes. Yield ~1%