Rectal Endometriosis That Is Difficult to Differentiate from Endoscopically Resectable Subepitherial Lesion

Endometriosis occurs most frequently in the intestine. In the pelvic organs intestinal endometriosis presents with various symptoms and endoscopic findings. If an asymptomatic submucosal lesion is found in the sigmoid colon or rectum of reproductive women, a differential diagnosis should be done. Owing to advancements in endoscopic therapy, endoscopic excision has been attempted for various subepithelial lesions. To successfully do an endoscopic excision, accurate diagnosis should be obtained through diagnostic tests such as endoscopic ultrasonography prior to excision. Here the authors report a case of rectal endometriosis in an asymptomatic woman of reproductive age. They attempted endoscopic resection based on the endoscopic finding that the subepithelial lesion was limited to the submucosal layer in endoscopic ultrasonography. This conclusion turned out to be a mistaken one. Because of tumor adhesion to the proper muscular layer, we failed to successfully conduct an endoscopic excision. Ultimately, we did surgery and diagnosed rectal endometriosis.