Fever of unknown origin: a retrospective study of 52 cases with evaluation of the diagnostic utility of FDG-PET/CT

Scand J Infect Dis. 2012 Jan;44(1):18-23. doi: 10.3109/00365548.2011.603741. Epub 2011 Sep 5.


Objectives: Fever of unknown origin (FUO) is dynamic in its origin and will be an ongoing challenge to the clinician because of shifting disease epidemiology. Here we present a series of patients with classical FUO admitted to an infectious diseases department during a 5-y period, with an emphasis on the diagnostic utility of ¹⁸F-fluorodeoxyglucose positron emission tomography (PET)/computed tomography (CT) in present-day cases of FUO.

Methods: Patient records were reviewed retrospectively.

Results: A final diagnosis was achieved for 31 of the 52 cases (60%). The final diagnoses of these 31 cases and their distribution in the respective diagnostic categories were: infections 32% (10/31), non-infectious inflammatory disease 55% (17/31), and malignancy 13% (4/31). In our study PET/CT successfully identified an infectious, inflammatory, or neoplastic cause of fever in 10 of the 22 patients (45%) who underwent this scan.

Conclusions: During the past decade the proportion of non-infectious inflammatory diseases in FUO series has increased. Based on our findings we recommend: (1) a PET/CT scan be performed early in the diagnostic work-up of patients with FUO, and (2) restraint in performing invasive procedures in patients with FUO in whom no cause of fever has been determined during diagnostic work-up.

MeSH terms

  • Adult
  • Aged
  • Female
  • Fever of Unknown Origin / diagnostic imaging*
  • Fever of Unknown Origin / etiology*
  • Fluorodeoxyglucose F18
  • Humans
  • Infections / complications*
  • Inflammation / complications*
  • Male
  • Middle Aged
  • Multimodal Imaging / methods*
  • Neoplasms / complications*
  • Positron-Emission Tomography*
  • Radiopharmaceuticals
  • Retrospective Studies
  • Tomography, X-Ray Computed*


  • Radiopharmaceuticals
  • Fluorodeoxyglucose F18