Endometriosis (en-doe-me-tree-O-sis) is an often painful disorder in which tissue that normally lines the inside of your uterus — the endometrium — grows outside your uterus (endometrial implant). Endometriosis most commonly involves your ovaries, bowel or the tissue lining your pelvis. Rarely, endometrial tissue may spread beyond your pelvic region.
In endometriosis, displaced endometrial tissue continues to act as it normally would — it thickens, breaks down and bleeds with each menstrual cycle. Because this displaced tissue has no way to exit your body, it becomes trapped. When endometriosis involves the ovaries, cysts called endometriomas may form. Surrounding tissue can become irritated, eventually developing scar tissue and adhesions — abnormal tissue that binds organs together.
Endometriosis can cause pain — sometimes severe — especially during your period. Fertility problems also may develop. Fortunately, effective treatments are available.
Although the exact cause of endometriosis is not certain, several possible explanations include:
- Retrograde menstruation. This is the most likely explanation for endometriosis. In retrograde menstruation, menstrual blood containing endometrial cells flows back through the fallopian tubes and into the pelvic cavity instead of out of the body. These displaced endometrial cells stick to the pelvic walls and surfaces of pelvic organs, where they grow and continue to thicken and bleed over the course of each menstrual cycle.
- Embryonic cell growth. The cells lining the abdominal and pelvic cavities come from embryonic cells. When one or more small areas of the abdominal lining turn into endometrial tissue, endometriosis can develop.
- Surgical scar implantation. After a surgery, such as a hysterectomy or C-section, endometrial cells may attach to a surgical incision.
- Endometrial cells transport. The blood vessels or tissue fluid (lymphatic) system may transport endometrial cells to other parts of the body.
- Immune system disorder. It’s possible that a problem with the immune system may make the body unable to recognize and destroy endometrial tissue that’s growing outside the uterus.
The primary symptom of endometriosis is pelvic pain, often associated with your menstrual period. Although many women experience cramping during their menstrual period, women with endometriosis typically describe menstrual pain that’s far worse than usual. They also tend to report that the pain has increased over time.
Common signs and symptoms of endometriosis may include:
- Painful periods (dysmenorrhea). Pelvic pain and cramping may begin before and extend several days into your period and may include lower back and abdominal pain.
- Pain with intercourse. Pain during or after sex is common with endometriosis.
- Pain with bowel movements or urination. You’re most likely to experience these symptoms during your period.
- Excessive bleeding. You may experience occasional heavy periods (menorrhagia) or bleeding between periods (menometrorrhagia).
- Infertility. Endometriosis is first diagnosed in some women who are seeking treatment for infertility.
- Other symptoms. You may also experience fatigue, diarrhea, constipation, bloating or nausea, especially during menstrual periods.
The severity of your pain isn’t necessarily a reliable indicator of the extent of the condition. Some women with mild endometriosis have extensive pain, while others with advanced endometriosis may have little pain or even no pain at all.
Endometriosis is sometimes mistaken for other conditions that can cause pelvic pain, such as pelvic inflammatory disease (PID) or ovarian cysts. It may be confused with irritable bowel syndrome (IBS), a condition that causes bouts of diarrhea, constipation and abdominal cramping. IBS can accompany endometriosis, which can complicate the diagnosis.
When to see a doctor
See your doctor if you have signs and symptoms that may indicate endometriosis. The cause of chronic or severe pelvic pain may be difficult to pinpoint. But discovering the problem early may help you avoid unnecessary complications and pain.