The role of 18F-FDG PET/CT in spinal infections: A comprehensive diagnostic tool

Spondylodiscitis poses diagnostic challenges due to nonspecific symptoms and limitations of conventional imaging modalities. Moreover, causative infection foci often remain unidentified. Early and accurate diagnosis and treatment of the infectious focus are essential to prevent severe complications. ¹⁸F-fluorodeoxyglucose positron emission tomography (FDG-PET) has emerged as complementary tool to MRI, enabling detection of metabolically active infectious processes.

This study evaluates the diagnostic accuracy of FDG-PET/CT in patients with suspected spondylodiscitis and its ability to identify additional infectious foci.

A retrospective analysis included 191 patients who underwent FDG-PET/CT for suspected spondylodiscitis between 01.01.2016 and 31.12.2023. PET findings were compared with MRI, pathological, and microbiological and clinical data.

Spinal infection was confirmed in 160 of 191 patients. In patients with inconclusive MRI findings (n = 46), FDG-PET/CT led to diagnostic reclassification in 21 cases (45.7%). In the subgroup analyzed for diagnostic accuracy (n = 56), sensitivity was 56% for FDG-PET/CT and 62% for MRI, increasing to 74% when both modalities were combined (p = 0.002). Specificity was 96% for FDG-PET/CT and 86% for MRI. FDG-PET/CT identified 23 previously unknown extraspinal infectious foci and confirmed 23 suspected foci, resulting in detection of infectious sources in 73% of patients. Infectious foci were detected more frequently in cervical infections (33.3% vs. 9.5%, p = 0.001). Patients undergoing FDG-PET/CT showed higher clinical resolution rates at follow-up (p = 0.045).

FDG-PET/CT provides complementary value in suspected spondylodiscitis, particularly in cases with inconclusive MRI and for detecting additional infectious foci, supporting its role in multimodal diagnostic strategies.