Unusual causes of tubo-ovarian abscess: CT and MR imaging findings.

Actinomycosis, tuberculosis, and xanthogranulomatous inflammation are rare but specific causes of tubo-ovarian abscess (TOA). TOAs with these causes are frequently misdiagnosed as ovarian malignancies due to their unusual appearances at computed tomography (CT) and magnetic resonance (MR) imaging. Tubo-ovarian actinomycosis frequently has a predominantly solid appearance. A linear, solid, well-enhancing lesion extending directly from the mass is a characteristic CT and MR imaging finding. Small rim-enhancing lesions in the solid part of the mass are also suggestive of actinomycosis. Tuberculous TOAs usually mimic peritoneal carcinomatosis from ovarian cancers. The granulomatous and fibrotic nature of this infection may be reflected in the CT and MR imaging appearances, which can help in differentiation. TOAs from xanthogranulomatous inflammation demonstrate more nonspecific imaging findings than actinomycotic or tuberculous TOAs, although multiple xanthogranulomas in the mass may be seen on MR images. Knowledge of these characteristics can help one make the correct diagnosis and treat the patients appropriately. (c) RSNA, 2004.