18F-fluorodeoxyglucose uptake pattern in patients with suspected spondylodiscitis.

BACKGROUND: Infections of the spine are rare and often discovered late, but they can have a severe outcome with hospital case fatality rates of up to 17%. Efficient and early diagnosis is important, because early diagnosis and therapy improve outcome. The aim of the current study was to evaluate the clinical value of F-fluorodeoxyglucose (18F-FDG) uptake pattern in PET as a diagnostic modality for the detection of spondylodiscitis.

MATERIALS AND METHODS: 18F-FDG-PET examinations of the spine were performed in 42 patients with suspected spondylodiscitis. Of these 42 patients, 13 had already undergone spinal surgery in the past, making initial definition of the test group difficult and complex. Qualitative analysis was based on 18F-FDG uptake patterns, and quantitative maximal standard uptake value measurements were ascertained. PET findings were verified by comparing them with combined information from intraoperative findings, blood results, microbiological investigations, histopathology, and clinical examination.

RESULTS: Evidence of spondylodiscitis was correctly determined in 95% of patients and absence of spondylodiscitis in 86% of patients using 18F-FDG-PET. The detection of spondylodiscitis by 18F-FDG-PET had a sensitivity of 86% and a specificity of 95%. Three patients had false-negative and one patient a false-positive finding on 18F-FDG-PET.

CONCLUSION: The application of 18F-FDG uptake patterns in 18F-FDG-PET helps to predict or exclude spondylodiscitis. Differentiation between inflammatory and degenerative changes in the vertebral body endplates is possible. Owing to the high specificity of this method, a negative PET result in the setting of a diagnostically unclear case diminishes the need for surgical intervention. 18F-FDG-PET is therefore an important tool in inflammation imaging and can be used in the diagnostic cascade of difficult cases with suspected spondylodiscitis. In contrast, a positive PET result does not always clearly establish the cause of increased 18F-FDG uptake.