MRI Features Associated With the Detection of Microbial Pathogens by CT-Guided Biopsy in Septic Spondylodiscitis

OBJECTIVE The aim of this study was to assess the magnetic resonance imaging (MRI) features associated with microbial pathogen detection by computed tomography (CT)-guided biopsy in patients with suspected septic spondylodiscitis. METHODS For the last 10-year period, we analyzed the medical records of patients who underwent MRI and CT-guided biopsy for suspected septic spondylodiscitis. Clinical characteristics were recorded. The following MRI features were assessed: edema or contrast enhancement of the intervertebral disc, adjacent vertebrae, epidural and paravertebral space, presence of abscess, and paravertebral edema size. A positive biopsy was defined by pathogen identification on bacterial analysis or the presence of granuloma on histology. Predictors of a positive biopsy were assessed with a logistic regression model. RESULTS We analyzed data for 61 patients (34 [56%] male; mean age, 59.9 ± 18.0 years); for 35 patients (57%), CT-guided biopsy was positive for a pathogen. The 4 MRI findings significantly associated with a positive biopsy were epiduritis, greater than 50% vertebral endplate edema, loss of intradiscal cleft, and abscess. The size of paravertebral edema was greater with a positive than negative biopsy (median, 15.9 [interquartile range, 11.3-21.3] vs 7.3 [4.6-12.9] mm; p = 0.004). On multivariable analysis, epiduritis was the only independent predictor of a positive biopsy (adjusted odds ratio, 7.4 [95% confidence interval, 1.7-31.4]; p = 0.006). CONCLUSIONS Epiduritis and the size of paravertebral edema on MRI are associated with detection of a microbial pathogen in suspected septic spondylodiscitis. For patients without these MRI signs, the need for further investigations such as enriched or prolonged cultures, a second CT-guided biopsy, or even surgical biopsy need to be discussed.