18FFDG PET/CT of FUO/IUO in special populations.

18F fluorodeoxyglucose (18FFDG) positron emission tomography/computed tomography (PET/CT) has established itself as a fundamental non invasive diagnostic technique in the investigation of patients with fever (FUO) and inflammation of unknown origin (IUO). These conditions are for definition challenging due to potential wide underlying causes, including inflammatory disease, infectious disease, malignancies and miscellanea. Sometimes no diagnosis is reached. Data about the diagnostic performances of 18FFDG PET/CT in special populations, such as pediatrics, end-stage renal disease, HIV and intensive care unit (ICU) patients, are preliminary and heterogeneous. Our review aims to describe the role of 18FFDG PET/CT imaging in these specific populations and focus on the potential clinical impact on diagnosis and patient management. Findings presented in the literature demonstrated a good diagnostic yield of FDG PET/CT in the study of these patients affected by FUO/IUO with performances similar to adult general populations. A positive PET scan is often contributory and, in some cases, even essential to diagnosis, whereas a negative scan may be equally important as it excludes focal disease and predicts a favourable prognosis. Further studies with larger populations would be desirable.