Endometriosis and inflammatory bowel disease: A systematic review of the literature

The potential link between endometriosis and Inflammatory Bowel Disease (IBD) has been investigated over the last twenty years. Endometriosis shares with IBD features and symptoms so to become a significant diagnostic challenge, resulting in a delayed or indeterminate diagnosis. We conducted a systematic review to summarize the available data in literature on the co-diagnosis of IBD and endometriosis. A systematic literature search was performed using the electronic databases MEDLINE and EMBASE from 1990 to November 2019, using the search terms: inflammatory bowel disease OR ulcerative colitis OR Crohn's disease AND endometriosis. We selected 23 articles: 15 case-report, 3 clinical series, 3 case-control studies, 1 cross-sectional study and 1 cohort study. All the epidemiological studies included in this review reported a positive association between endometriosis and IBD. Meta-analysis was not possible because, due to study design and type of patients included, there were no comparable groups to analyze. In epidemiological studies with a control group, the proportion of IBD in patients with endometriosis varied from 2 to 3.4 %, compared to 0-1 % of the control group. A large nationwide Danish cohort study reported a 50 % increase in the risk of IBD in women with endometriosis in comparison with women in the general population. In a large Danish cohort study women with endometriosis had an increased risk of CD and UC with a standardized incidence ratio of 1.5 (95 % CI 1.3-1.7) and 1.6 (95 % CI 1.3-2.0) respectively. Several studies do not provide information on the temporal sequence of endometriosis and IBD and therefore a clear analysis of a cause-effect association between these two pathologies is lacking. The high number of case-reports in the literature highlights how the diagnosis can be challenged, as endometriosis can be masquerading as IBD or vice versa or be present within the same patient. Further research is needed to better understand the temporal association between endometriosis and IBD, which could be useful to correct evaluation and improve the management of these patients.