In this study of 38,000 Danish women who were hospitalized between 1997 and 2007 and then tracked up to 13 years after their follow up. More women developed inflammatory bowel disease (ulcerative colitis at a rate for than double Crohn’s). Women who have endometriosis were 50% more likely to get inflammatory bowel disease than the general population. The woman who had surgery to verify that they had endometriosis were 80% more likely to get inflammatory bowel disease than the general population. In this study the percent chance of getting inflammatory bowel disease was .8%.
Even though women who have endometriosis are more likely to get inflammatory bowel disease a 50%-80% increase in a disease the disease would still affect relatively few women. Although, it is interesting if endometriosis is causing inflammatory bowel disease. When looking at these studies we have to be careful not to assume X cause Y since the human body is so complex and there are many factors involved.