FDG-PET or PET/CT in Fever of Unknown Origin: The Diagnostic Role of Underlying Primary Disease

Abstract

Fever of unknown origin (FUO) is generally defined as a fever greater than 38.3°C on several occasions during a period longer than 3 weeks for which the etiology behind cannot be diagnosed at the end of at least 1 week hospital stay. Conventional diagnostic methods are still not adequate to reveal underlying reason in approximately 50% of patients with FUO. In patients with certain diagnosis, three major categories are infections, malignancies, and noninfectious inflammatory diseases. Fluoro-18-fluoro-2-deoxy-D-glucose (FDG) is a structural analog of 2-deoxyglucose and accumulates in malignant tissues but also at sites of infection and inflammation. For this reason, FDG PET or PET/CT has great advantage in understanding of underlying pathology in assessment of FUO. However, till today, there are limited studies about the role of FDG PET or PET/CT in evaluation of FUO. In this paper, the impact of FDG PET or PET/CT in the diagnostic work-up of FUO is described by data obtained from literature review.

Figure 1

A 54-year-old woman with FUO underwent PET-CT for the diagnosis of underlying disease. Transaxial slices of CT (a1, b1), fusion (a2, b2), and PET (a3, b3) and anterior MIP image (c) showed accumulation of FDG in the wall of thoracic aorta and the supra-aortal branches. Gigantocellular arteritis was confirmed subsequently by temporal arterial biopsy.

Figure 2

PET-CT of a 63-year-old man with FUO. Transaxial slices of CT (a), fusion (b), PET (c), and anterior MIP image (d) demonstrated increased uptake of FDG in the pericardium. Viral pericarditis was diagnosed by fine needle aspiration biopsy.

Figure 3

A 58-year-old man with long standing FUO. Diffuse FDG accumulation in bone marrow with no extraosseous manifestations was shown on the transaxial slices of CT (a1, b1), fusion (a2, b2), and PET (a3, b3) and anterior MIP image (c). Non-Hodgkin's lymphoma was diagnosed by bone marrow biopsy.

Figure 4

PET-CT of a 77-year-old man with FUO. Transaxial slices of CT (a1, b1), fusion (a2, b2), and PET (a3, b3), and anterior whole body (c1), lower extremities (c2) MIP images revealed multiple foci in the walls of vessels. Nonspecific vasculitis was diagnosed by biopsy.