Endometriosis is a condition in which cells similar to those in the endometrium, the layer of tissue that normally covers the inside of the uterus, grow outside of it.  Most often this is on the ovaries, fallopian tubes, and tissue around the uterus and ovaries; however, in rare cases it may also occur in other parts of the body. The main symptoms are pelvic pain and infertility. Nearly half of those affected have chronic pelvic pain, while in 70% pain occurs during menstruation. Pain during sexual intercourse is also common. Infertility occurs in up to half of women affected. Less common symptoms include urinary or bowel symptoms. About 25% of women have no symptoms. Endometriosis can have both social and psychological effects.

The cause is not entirely clear. Risk factors include having a family history of the condition. The areas of endometriosis bleed each month, resulting in inflammation and scarring. The growths due to endometriosis are not cancer. Diagnosis is usually based on symptoms in combination with medical imaging, however, biopsy is the surest method of diagnosis. Other causes of similar symptoms include pelvic inflammatory disease, irritable bowel syndrome, interstitial cystitis, and fibromyalgia. Endometriosis is commonly misdiagnosed, and women are often incorrectly told their symptoms are trivial or normal.

Tentative evidence suggests that the use of combined oral contraceptives reduces the risk of endometriosis. Exercise and avoiding large amounts of alcohol may also be preventive. There is no cure for endometriosis, but a number of treatments may improve symptoms. This may include pain medication, hormonal treatments or surgery. The recommended pain medication is usually a non-steroidal anti-inflammatory drug (NSAID), such as naproxen. Taking the active component of the birth control pill continuously or using an intrauterine device with progestogen may also be useful. Gonadotropin-releasing hormone agonist (GnRH agonist) may improve the ability of those who are infertile to get pregnant. Surgical removal of endometriosis may be used to treat those whose symptoms are not manageable with other treatments.

One estimate is that 10.8 million people are affected globally as of 2015. Other sources estimate about 6–10% of women are affected. Endometriosis is most common in those in their thirties and forties; however, it can begin in girls as early as eight years old. It results in few deaths. Endometriosis was first determined to be a separate condition in the 1920s. Before that time, endometriosis and adenomyosis were considered together. It is unclear who first described the disease.

Signs and symptoms

Drawing showing endometriosis

Pain and infertility are common symptoms, although 20-25% of women are asymptomatic.

Pelvic pain

A major symptom of endometriosis is recurring pelvic pain. The pain can range from mild to severe cramping or stabbing pain that occurs on both sides of the pelvis, in the lower back and rectal area, and even down the legs. The amount of pain a woman feels correlates weakly with the extent or stage (1 through 4) of endometriosis, with some women having little or no pain despite having extensive endometriosis or endometriosis with scarring, while other women may have severe pain even though they have only a few small areas of endometriosis. The most severe pain is typically associated with menstruation. Pain can also start a week before a menstrual period, during and even a week after a menstrual period, or it can be constant. The pain can be debilitating and result in emotional stress. Symptoms of endometriosis-related pain may include:

dysmenorrhea – painful, sometimes disabling cramps during the menstrual period; pain may get worse over time (progressive pain), also lower back pains linked to the pelvis

chronic pelvic pain – typically accompanied by lower back pain or abdominal pain

dyspareunia – painful sexual intercourse

dysuria – urinary urgency, frequency, and sometimes painful voiding

mittelschmerz – pain associated with ovulation

bodily movement pain – present during exercise, standing, or walking

Compared with women with superficial endometriosis, those with deep disease appear to be more likely to report shooting rectal pain and a sense of their insides being pulled down.[16] Individual pain areas and pain intensity appear to be unrelated to the surgical diagnosis, and the area of pain unrelated to area of endometriosis.

There are multiple causes of pain. Endometriosis lesions react to hormonal stimulation and may "bleed" at the time of menstruation. The blood accumulates locally if it is not cleared shortly by the immune, circulatory, and lymphatic system. This may further lead to swelling, which triggers inflammation with the activation of cytokines, which results in pain. Another source of pain is the organ dislocation that arises from adhesion binding internal organs to each other. The ovaries, the uterus, the oviducts, the peritoneum, and the bladder can be bound together. Pain triggered in this way can last throughout the menstrual cycle, not just during menstrual periods.

Also, endometriotic lesions can develop their own nerve supply, thereby creating a direct and two-way interaction between lesions and the central nervous system, potentially producing a variety of individual differences in pain that can, in some women, become independent of the disease itself. Nerve fibres and blood vessels are thought to grow into endometriosis lesions by a process known as neuroangiogenesis.

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Journal of Autoimmune Disorders
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