Ultrasonographic evaluation of anal endometriosis: report of four cases

Background The presence of endometriosis in the anal canal and perianal tissues is rare and difficult to suspect at clinical examination. We report our experience with preoperative ultrasound evaluation of four cases of anal endometriosis. Methods Four patients were evaluated by transperineal and high-resolution three-dimensional endoanal ultrasonography. Results In 3 of 4 women, the lesions involved old episiotomy scars. Anal endometriosis appeared as hypoechoic cystic lesions with areas of microcalcification, not well delimited and highly vascularized. The lesions either involved the anal sphincter ( n = 2, one within the rectovaginal septum) or were localized superficially in the ischiorectal space ( n = 2). Surgery and pathologic exam confirmed the ultrasonographic findings. Conclusions Ultrasonographic findings of anal endometriosis are characteristics and may allow accurate preoperative staging of the disease.