Endometriosis is a condition in which the endometrium, tissue that normally lines the uterus, grows in other areas of the body, causing pain, irregular bleeding, and frequently infertility.

The tissue growth typically occurs in the pelvic area, outside of the uterus, on the ovaries, bowel, rectum, bladder, and the delicate lining of the pelvis, but it can occur in other areas of the body as well.

Causes, incidence, and risk factors

The cause of endometriosis is unknown. However, a number of theories have been proposed. The retrograde-menstruation theory proposes that endometrial cells (loosened during menstruation) may “back up” through the fallopian tubes into the pelvis, where they implant and grow in the pelvic and/or abdominal cavities.

The immune-system theory suggests that a deficiency in the immune system allows menstrual tissue to implant and grow in areas other than the uterine lining. Another theory suggests that the cells lining the abdominal cavity may spontaneously develop endometriosis. A genetic theory proposes that certain families may exhibit predisposing factors that lead to endometriosis.

Once the endometrial cells implant in tissue outside of the uterus, they may become a problem. Each month the ovaries produce hormones that stimulate the cells of the uterine lining to multiply and prepare for a fertilized egg (swell and thicken).

The endometrial cells outside of the uterus also respond to this signal, but they lack the ability to then separate themselves from the surrounding tissue and slough off during the next menstrual period. They sometimes bleed a little bit, but they heal and are stimulated again during the next cycle.

This ongoing process can cause scarring and adhesions in the tubes and ovaries, and around the tubal fimbriae (fingerlike projections at the end of the fallopian tubes). These adhesions can make transfer of an ovum from the ovary to the fallopian tube difficult or impossible. They can also stop passage of a fertilized egg down the fallopian tube to the uterus.

Once in a while the growing cells will penetrate the tough covering of the ovary and begin to multiply. These cells can collect large amounts of blood and form what is called, appropriately, an ovarian blood cyst (endometrioma).

Ovarian blood cysts have been known to grow to the size of a hen’s egg or even an orange, and are usually painful. Over time the collected blood darkens and, for this reason, the cysts are frequently called “chocolate cysts.”

Endometriosis is a common problem. It occurs in an estimated 10% of women during their reproductive years. The prevalence may be as high as 35% among infertile women. Although endometriosis is typically diagnosed between the ages of 25 and 35, the problem probably begins about the time that regular menstruation begins.

A woman who has a mother or sister with endometriosis has a risk of developing endometriosis that is 6 times greater than that of the general population. Other possible risk factors include early onset of menstrual periods, regular menstrual cycles, and periods lasting 7 or more days.


  • Increasingly painful periods  
  • Lower abdominal pain or pelvic cramps that can by felt for a week or two before menstruation and/or during menstruation (the pain and cramps may be steady and dull or quite severe)  
  • Pelvic or low-back pain that may occur at any time during the menstrual cycle  
  • Pain during or following sexual intercourse  
  • Pain with bowel movements  
  • Premenstrual spotting  
  • Infertility

Note: Frequently, symptoms may not be present. In fact, some women with severe cases of endometriosis have no pain at all, while some women with only a few small adhesions have severe discomfort.

Signs and tests

A pelvic examination may reveal the presence of tender nodules, with a lumpy consistency. These are often found in the posterior vaginal wall or adnexa (ovary regions), and they may sometimes be felt in healed wound scars (especially those from episiotomy and C-section). There may be pain with uterine motion.

The uterus may be fixed or retroverted. A pelvic ultrasound test may detect an endometrioma on an ovary. A laparoscopy is necessary for a definite diagnosis, but most patients can start treatment without this.


Treatment depends on the the degree of symptoms experienced, the extent of the disease (determined through laparoscopy), the woman’s desire for future childbearing, and the woman’s age.

Observation may be the appropriate treatment for younger women with minimal disease and symptoms. It is important to have the woman maintain a regular schedule of examinations (every 6 to 12 months) to note any changes or progression of the disease.

Treatment with medications may focus on several strategies. Analgesic therapy, treating the discomfort of the disease only, may be indicated for women with mild to moderate premenstrual pain, with no pelvic examination abnormalities, and with no immediate desire to become pregnant.

“Pseudopregnancy” (a state resembling pregnancy) may be achieved through hormonal drug regimens. This approach was developed in response to the observed regression of endometriosis during pregnancy.

Pseudopregnancy can be induced using oral contraceptives containing estrogen and progesterone. This takes 6 to 9 months and relieves most of the symptoms, but does not prevent scarring and adhesion left by the disease. Potential side effects, such as breakthrough spotting, may limit this treatment option.

Progesterone medications by themselves are another effective hormonal treatment for endometriosis. Progesterone pills or injections can be used. Possible side effects of these agents - including depression, weight gain, and breakthrough spotting, may be a problem for some patients.

“Pseudomenopause” (a state resembling menopause) was developed as a means of treatment because of the observation that endometriosis regresses after menopause. Danazol, a weak androgenic (male characteristic) hormonal drug may be used to reduce natural levels of estrogen and progesterone to low levels.

Some studies have shown that the use of danazol may be superior to the “pseudopregnancy” regimens in controlling symptoms and progression of the disease in women with moderate-to-severe endometriosis. However, due to possible side effects from danazol, it is now prescribed less often then some newer medications.

A new class of antigonadotropin drugs has been developed that also produces a “pseudomenopausal” state in women.

These drugs, such as Synarel and Depo Lupron (trade names), prevent stimulation of the pituitary for the production of FSH (follicle stimulating hormone) and LH (luteinizing hormone). This stops the ovary from producing estrogen. Potential side effects of these drugs include: menopausal symptoms (such as hot flashes), vaginal dryness, mood changes, and early loss of calcium from the bones.

Due to the effects on bone density, treatment of endometriosis with one of these agents is usually limited to 6 months or less.

Surgery (either laparoscopy or laparotomy) is usually reserved for women with severe endometriosis, including adhesions and infertility. Conservative surgery attempts to remove or destroy all of the outside endometriotic tissue, remove adhesions, and restore the pelvic anatomy to as close to normal as possible. Nerve removal (neurectomy) may rarely be performed during surgery as a means of relieving the pain associated with endometriosis.

Definitive surgery is appropriate for the woman with severe symptoms or disease, and no desire for future childbearing. This type of surgery involves abdominal removal of the uterus (hysterectomy), both ovaries, both fallopian tubes, and any remaining adhesions or endometriotic implants. Hormonal replacement therapy may be indicated after removal of the ovaries and should be tailored to the individual woman’s needs.

Expectations (prognosis)

Fertility rates in women with mild endometriosis are very high, even without therapy. Enhanced fertility after surgery for endometriosis depends on the extent of the endometriosis.

Pregnancy rates, achieved after conservative surgery in women previously considered to be infertile, are approximately 75% for mild endometriosis, 50-60% for moderate cases, and 30-40% for severe cases.


Infertility may result from endometriosis, but not in every patient - especially if the endometriosis is mild. Endometriosis has been known to recur even after a hysterectomy. Other complications are rare. In a few cases endometriosis implants may cause obstructions of the gastrointestinal or urinary tracts.

Calling your health care provider

Call for an appointment with your health care provider if symptoms of endometriosis occur, or if back pain or other symptoms recur after treatment of endometriosis.

Screening for endometriosis should be considered if your mother or sister has been diagnosed with endometriosis, or if you are unable to become pregnant after 1 year of attempting to conceive.


There is no proven prevention for endometriosis. Women with a strong family history of endometriosis may consider taking oral contraceptive pills, as this treatment may help to prevent or slow down the development of the disease.

Johns Hopkins patient information

Last revised: December 7, 2012
by Sharon M. Smith, M.D.

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