Role of colonoscopy in the diagnostic work-up of bowel endometriosis

AIM: To evaluate the accuracy of colonoscopy for the prediction of intestinal involvement in deep pelvic endometriosis. METHODS: This prospective observational study was performed between September 2011 and July 2014. Only women with both a clinical and imaging diagnosis of deep pelvic endometriosis were included. The study was approved by the local ethics committee and written informed consent was obtained in all cases. Both colonoscopy and laparoscopy were performed by expert surgeons with a high level of expertise with these techniques. Laparoscopy was performed within 4 wk of colonoscopic examination. All hypothetical colonoscopy findings (eccentric wall thickening with or without surface nodularities and polypoid lesions with or without surface nodularities of endometriosis) were compared with laparoscopic and histological findings. We calculated the sensitivity, specificity, positive predictive value and negative predictive value for the presence of colonoscopic findings of intestinal endometriosis. RESULTS: A total of 174 consecutive women aged between 21-42 years with a diagnosis of deep pelvic endometriosis who underwent colonoscopy and surgical intervention were included in our analysis. In 76 of the women (43.6%), intestinal endometrial implants were found at surgery and histopathological examination. Specifically, 38 of the 76 lesions (50%) were characterized by the presence of serosal bowel nodules; 28 of the 76 lesions (36.8%) reached the muscularis layer; 8 of the 76 lesions (10.5%) reached the submucosa; and 2 of the 76 lesions (2.6%) reached the mucosa. Colonoscopic findings suggestive of intestinal endometriosis were detected in 7 of the 174 (4%) examinations. Colonoscopy failed to diagnose intestinal endometriosis in 70 of the 76 women (92.1%). A colonoscopic diagnosis of endometriosis was obtained in all cases of mucosal involvement, in 3 of 8 cases (37.5%) of submucosal involvement, in no cases of muscularis layer involvement and in 1 of 38 cases (2.6%) of serosa involvement. The sensitivity, specificity, positive predictive and negative predictive values of colonoscopy for the diagnosis of intestinal endometriosis were 7%, 98%, 85% and 58%, respectively. CONCLUSION: Being an invasive procedure, colonoscopy should not be routinely performed in the diagnostic work-up of bowel endometriosis.