Unexplained fever in children—Benefits and challenges of FDG‐PET/CT

Aim To explore [fluorine‐18]‐fluoro‐2‐deoxy‐d‐glucose positron‐emission‐tomography/computed tomography (18FDG‐PET/CT) in patients where standard investigations were non‐diagnostic. Methods We reviewed medical records of previously healthy children who had 18FDG‐PET/CT performed at Copenhagen University Hospital in 2015–2020 due to unexplained fever. Results Thirty‐five of 819 paediatric 18FDG‐PET/CT were performed due to unexplained fever. The final diagnoses were malignancy (11%), infections (23%), inflammatory diseases (43%) and miscellaneous (26%). 18FDG‐PET/CT was diagnostic in six cases with Takayasu's arteritis, tuberculosis, Langerhans cell histiocytosis and Ewing sarcoma. Sixteen cases had focal 18FDG‐uptake, but 18FDG‐PET/CT could only differentiate malignancy, infection and inflammation in three cases. In six cases with inflammatory diseases and no focal signs, PET/CT was normal except increased non‐specific 18FDG‐uptake in bone marrow and spleen in five cases. One case was false positive (suspicion of appendicitis) and two false negative (leukaemia and inflammatory disease). Conclusion 18FDG‐PET/CT was diagnostic, or contributed to the diagnosis, in several children with unexplained fever referred to a tertiary centre. Challenges comprised (i) only increased non‐specific 18FDG‐uptake in bone marrow and spleen in half of cases with inflammatory diseases, (ii) no differentiation between complicated infections, malignancy and inflammation in most cases with focal processes and (iii) a small risk of false positive and false negative results.