Ultrasound-guided Aspiration Combined with Medical Treatment for an Unexpected Rectal Endometriotic Cyst: A Case Report.

Most bowel endometriotic lesions are ill-defined serosal and subserosal nodules, and no case of cystic bowel endometriosis has been reported in the literature. This is the first report of an unexpected presentation of bowel endometriosis as a primary cyst located inside the posterior rectal wall. The patient was a 26-year-old nulliparous woman with progressive lower abdominal pain for 6 days and difficult defecation for 1 day. Colorectal surgeons recommended bowel resection owing to the giant rectal mass. However, the patient refused to undergo surgery. Ultrasound-guided aspiration of the rectal endometriotic cyst followed by gonadotropin-releasing hormone agonist injection was individually scheduled, which finally brought significant improvement both in symptoms and in the size of the rectal endometriotic lesion.