Figure 3b. Tubo-ovarian actinomycosis in a 44-year-old woman. The TOA has a predominantly solid appearance. (a) Contrast-enhanced CT scan shows a round, solid mass (arrows) in the right adnexal region. Multiple small, rim-enhancing lesions (arrowheads) are seen inside the mass. (b) Contrast-enhanced CT scan obtained caudad to a shows a well-enhancing solid lesion (arrows) extending posteriorly from the mass. (c) Contrast-enhanced CT scan obtained caudad to b shows an enhancing perirectal mass (arrows), which is formed by the lesion extending from the adnexal mass. An IUD is noted (arrowhead). (d) Image from a barium study of the rectosigmoid shows segmental narrowing of the distal sigmoid colon with a serrated border (arrows), an appearance indicative of invasion by the perirectal mass.