Fever of unknown origin in the hospitalized patient

Fever of unknown origin (FUO) is defined as pyrexia of greater than 38.3°C for at least 3weeks with no identified cause after 3days of hospital evaluation or at least 3 outpatient visits. Infection, autoimmune disorders, and malignancy remain the most important causes of FUO in a hospitalized patient. Taking a complete history and performing a comprehensive physical examination are profoundly important in establishing the underlying cause of FUO, and imaging studies are becoming increasingly informative. Although the cause of FUO will remain undetermined in 20% of patients, these patients generally have a good prognosis.