Abstract Introduction Colonoscopy enables detailed endoscopic evaluation of the interior of the colon. Changes observed via colonoscopy may be subtle or pronounced and can sometimes mimic those of other diseases, such as deep intestinal endometriosis. The diagnosis of endometriosis in the distal sigmoid and rectum by colonoscopy has been described in previous case reports. Objective We aimed to correlate the endoscopic changes found in the distal sigmoid and rectum with the presence of endometrial deposits confirmed by transrectal ultrasound (TRUS). Methods We included 50 female patients referred to the endoscopy department at our institution for colonoscopy, rectosigmoidoscopy, or TRUS, who exhibited one or more symptoms associated with endometriosis. Results The colonoscopic findings were normal in 36 patients but showed alterations in 14 patients. Among the latter, TRUS revealed involvement of the sigmoid and/or rectal wall in 11 patients. Conclusions The endoscopic changes in the distal sigmoid or rectum described in this study were strongly associated with endometrial deposits confirmed using TRUS.