Anal endosonography in the diagnosis and management of perianal endometriosis: report of a case.

We report a rare case of perianal endometriosis, diagnosed in a 39-year-old woman who presented with a several-day history of a painful mass in the perineum. Perianal examination showed redness and swelling in the right anterior direction. A soft tumor was palpated, but there was no evidence of an episiotomy scar, or of fistula orifices. An anal endosonography in the right anterior direction revealed a sharply defined lesion, 17 x 14 mm in diameter, with high echoic enhancement at its center. The lesion was located along the edge of the external anal sphincter but did not involve it. Based on these endosonographic findings, the tumor was not considered to be an abscess or fistula. We detected its location, and judged it possible to enucleate the tumor under local anesthesia without injuring the anal sphincter. The operation was performed uneventfully and a histological diagnosis of endometriosis was confirmed. Using anal endosonography, we were able to determine the exact anatomic relationship of the lesion in the internal and external sphincter, which substantially influenced the diagnosis and operative procedures.