Irritable bowel syndrome, or IBS, is a relatively common disorder that affects the colon. Many of its symptoms are similar to those of endometriosis, such as diarrhea, constipation, bloating, cramping, and abdominal pain. Unlike endometriosis, IBS can be more or less controlled with medication or a change in diet. Surgery is rarely needed. Doctors often mistake endometriosis for IBS because of the similarities in symptoms and because they don’t know much, if anything, about endometriosis. I know that the intentions of these doctors are very good—they want their patients to get well—but their knowledge is limited.