Documented fever of >38.3’C (101’F) for more than 3 weeks and no established diagnosis despite appropriate investigation for 1 week.
Three major categories: infections, collagen-vascular disease and granulomatous disease and tumors.
Workup includes history, physical examination, CBC, chemical blood profile, urinalysis, multiple blood cultures, chest X-ray, CT scan of the abdomen and chest.
Infections constitute about one third of cases.
Tumors account for 7-13% of cases.
Durack and Street proposed four groups: classic, nosocomial, neutropenic, and HIV-associated.
Classic Petersdorf/Beeson FUOs-36% infections, 19% malignancy related, collagen vascular diseases 19%, miscellaneous disorders such as drug fever 19%, and 7% not determined.
Recent FUOs more related to ICU patients with traumatic brain injuries, of other neurologic diseases, dementia, mechanically ventilated, some have central or peripheral intravenous catheters, some cases postoperative, multiple have had previous antibiotics.
PET scan useful in evaluating such patients.