Diagnostic value of 18F-FDG PET/CT in fever of unknown origin

Fever of unknown origin is a common differential diagnostic problem in medicine. More than 60 years have passed since the first established definition of the disease, and despite constant development and improvement of diagnostic procedures, the differential diagnosis and choosing adequate therapy still remains a challenge in this patient popula-tion. The medical literature lists at least 200 diseases that may manifest with fever of unknown origin, and it encom-passes a wide clinical spectrum. This symptom is present in approximately 1.5-3% of hospitalized patients. In recent decades, not only the concept of fever of unknown origin has changed several times, but the recommended differen-tial diagnostic procedures as well. Positron emission tomography is one of the latest imaging procedures that also contributes to establishing the correct diagnosis. The purpose of this publication is to provide an overview of differ-ent diseases which might cause fever of unknown origin, and the most frequently used diagnostic algorithms, more-over to highlight the importance of positron emission tomography in the evaluation of the aetiology of fever of un-known origin.