Diagnostic yield of CT-guided percutaneous aspiration procedures in suspected spontaneous infectious diskitis

PURPOSE: To evaluate the diagnostic yield of computed tomography (CT)-guided percutaneous needle aspiration procedures in the setting of suspected spontaneous infectious diskitis and to assess the usefulness of concurrent cytologic examination as a supplement to microbiologic evaluation. MATERIALS AND METHODS: A retrospective study was performed to evaluate 105 consecutive CT-guided percutaneous disk space aspiration procedures in 92 patients suspected of having spontaneous (non-postoperative) infectious diskitis. Our criterion standard for the presence of active infection was the identification of a pathogen either from the CT-guided aspiration specimen or from a surgical specimen. All cases had microbiologic analysis, 78 cases had cytopathologic analysis, and 31 cases had open surgery. RESULTS: Microbiologic analysis of the CT-guided percutaneous aspiration specimens was positive in 39 of 43 cases proved to have active infections, with four false-negative and no false-positive cases (sensitivity, 91%; specificity, 100%). The false-negative cases were all active fungal infections identified from surgical specimens. Adding cytopathologic analysis to microbiologic analysis improved sensitivity but reduced specificity. The most common pathogens were species of Staphylococcus, Streptococcus, Candida, and Mycobacterium. All 30 active bacterial infections were identified with the CT-guided procedures, but only five of nine fungal infections were identified. CONCLUSION: CT-guided percutaneous needle aspiration is an accurate method for identifying active bacterial disk space infections but is less reliable for identifying fungal infections.