Imaging findings of primary urachal actinomycosis.

Primary actinomycosis in urachal remnant is documented rarely in the English literature. The disease is usually misdiagnosed as urachal carcinoma because of its infiltrating and enhancing natures. We illustrate a case of urachal actinomycosis with ultrasound, computed tomography, and magnetic resonance images. The clinical, radiological, and pathological findings are reviewed. Some imaging findings may help us to differentiate an inflammatory process from malignancy.