Endoanal sonography in the assessment of perianal endometriosis with external anal sphincter involvement.

Endoanal sonography can be used in the assessment of benign and malignant anal conditions and to evaluate the anatomy of the anal sphincters. We used endoanal sonography with a 10-MHz rotating endocavitary probe to evaluate a 45-year-old woman with a perianal mass, fecal incontinence, and menses-associated perianal pain. She had had 2 vaginal deliveries requiring episiotomies. Biopsy of the mass showed endometrial tissue. The ultrasound examination showed a perianal mass and an external anal sphincter injury. A wide excision and sphincteroplasty were performed, with improvement of fecal continence and pain. Histopathologic examination of the mass confirmed perianal endometrioma in an episiotomy scar.