Pyomyositis: characteristics at CT and MR imaging.
OBJECTIVE
To establish imaging criteria for pyomyositis (PM).


METHODS
Twenty-seven computed tomographic (CT) scans and 11 magnetic resonance (MR) images obtained in 32 patients with PM were reviewed. Images in 10 patients with PM and 16 with soft-tissue masses were evaluated blindly.


RESULTS
At CT, all 27 patients had muscle enlargement with heterogeneous attenuation; 26 patients had a focal fluid collection, with rim enhancement in all 18 patients who underwent contrast material-enhanced CT. Twenty-four patients had cellulitis. At MR imaging, all 11 patients had both a subtle increase in signal intensity in the affected muscle(s) on T1-weighted images and cellulitis. Nine patients had a focal fluid collection, which had high signal intensity and a hypointense rim on T2-weighted images. In six patients, a rim of increased signal intensity was seen around the collection on T1-weighted images. Six gadolinium-enhanced examinations demonstrated rim enhancement. Eight patients had fluid in the distal joint. All patients with PM were correctly identified when evaluated with the control subjects; however, there were four false-positive results.


CONCLUSIONS
CT and MR imaging can help characterize changes that are suspicious for PM.
Gordon
B A
BA
Department of Radiology, Duke University Medical Center, Durham, NC 27710, USA.
Martinez
S
S
Collins
A J
AJ
D000293:Adolescent; D000328:Adult; D000368:Aged; D002648:Child; D002675:Child, Preschool; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D009220:Myositis / Q000175:diagnosis* / Q000000981:diagnostic imaging; D013203:Staphylococcal Infections; D013492:Suppuration / Q000175:diagnosis / Q000000981:diagnostic imaging; D014057:Tomography, X-Ray Computed