Endometriosis
Endometriosis is a noncancerous disorder in which pieces of endometrial tissue--normally occurring only in the lining of the uterus (endometrium)--grow outside the uterus.
 See the figure Endometriosis: Misplaced Tissue.
Endometriosis is a chronic disorder that may be painful. Exactly how many women have endometriosis is unknown because it can usually be diagnosed only by directly viewing the endometrial tissue (which requires a surgical procedure). Endometriosis probably affects about 10 to 15% of menstruating women aged 25 to 44. It can also affect teenagers.
Endometriosis sometimes runs in families. It is more likely to occur in women who have their first baby after age 30, who have never had a baby, who are of Asian descent, or who have structural abnormalities of the uterus.
The cause of endometriosis is unclear, but there are several theories: Small pieces of the uterine lining that are shed during menstruation may flow backward through the fallopian tubes toward the ovaries into the abdominal cavity, rather than flow through the vagina and out of the body with the menstrual period. Cells from the uterine lining (endometrial cells) may be transported through the blood or lymphatic vessels to another location. Or cells located outside the uterus may change into endometrial cells.
Common locations of misplaced endometrial tissue are the ovaries and the ligaments that support the uterus. Less common locations are the outer surface of the small and large intestines, the ureters (tubes leading from the kidneys to the bladder), the bladder, the vagina, and surgical scars in the abdomen. Rarely, endometrial tissue grows on the membranes covering the lungs (pleura), the sac that envelops the heart (pericardium), the vulva, or the cervix.
As the disorder progresses, the misplaced endometrial tissue tends to gradually increase in size. It may also spread to new locations.
Symptoms
The main symptom associated with endometriosis is pain in the lower abdomen and pelvic area. The pain usually varies during the menstrual cycle. Menstrual irregularities, such as heavy menstrual bleeding and spotting before menstrual periods, may occur. Misplaced endometrial tissue responds to the same hormones--estrogen and progesterone (produced by the ovaries)--as normal endometrial tissue in the uterus. Consequently, the misplaced tissue may also bleed during menstruation, often causing cramps and pain.
Some women with severe endometriosis have no symptoms. Others, even some with minimal disease, have incapacitating pain. In many women, endometriosis does not cause pain until it has been present for several years. For such women, sexual intercourse tends to be painful before or during menstruation.
Endometrial tissue attached to the large intestine or bladder may cause abdominal bloating, pain during bowel movements, rectal bleeding during menstruation, or pain above the pubic bone during urination. Endometrial tissue attached to an ovary or a nearby structure can form a blood-filled mass (endometrioma). Occasionally, an endometrioma ruptures or leaks, causing sudden, sharp abdominal pain.
The misplaced endometrial tissue may irritate nearby tissues. As a result, scar tissue may form, sometimes as bands of fibrous tissue (adhesions) between structures in the abdomen. The misplaced endometrial tissue and adhesions can interfere with the functioning of organs. Rarely, adhesions block the intestine.
Severe endometriosis may block the egg's passage from the ovary into the uterus, causing infertility. Mild endometriosis may also cause infertility, but how it does so is less clear. Endometriosis affects as many as 25 to 50% of infertile women.
Diagnosis
A doctor may suspect endometriosis in a woman who has certain symptoms or unexplained infertility. Occasionally, during a pelvic examination, a woman may feel pain or tenderness or a doctor may feel a mass of tissue behind the uterus or near the ovaries.
However, the diagnosis can usually be confirmed only if a doctor examines the abdominal cavity and sees pieces of endometrial tissue. For this examination, a viewing tube (laparoscope) is usually used. It is inserted into the abdominal cavity through a small incision just below the navel. Carbon dioxide gas is injected into the abdominal cavity to distend it so that organs can be viewed more easily. Laparoscopy usually requires a general anesthetic, so that the entire abdominal cavity can be examined. An overnight stay in the hospital is not required. Laparoscopy may cause mild abdominal discomfort, but normal activities can usually be resumed in 1 or 2 days.
Sometimes a biopsy is necessary. A small sample of tissue is removed, usually through the laparoscope, and examined under a microscope.
Other procedures, such as ultrasonography, barium enemas with x-ray, computed tomography (CT), and magnetic resonance imaging (MRI), may be used to determine the extent of endometriosis and follow its course, but their usefulness for diagnosis is limited. Blood tests may be performed to measure levels of substances (called markers) that increase when endometriosis is present. Markers include cancer antigen 125 and antibodies to endometrial tissue. Such measurements may help a doctor follow the course of endometriosis. However, because these markers may be increased in several other disorders, they are not useful in establishing the diagnosis. Tests may also be performed to determine whether the endometriosis is affecting the woman's fertility (see Section 22, Chapter 254).
Treatment
Treatment depends on a woman's symptoms, pregnancy plans, and age, as well as the extent of endometriosis.
Drugs can be given to suppress the activity of the ovaries and thus slow the growth of the misplaced endometrial tissue and reduce bleeding and pain. However, these drugs do not eliminate endometriosis. They include combination oral contraceptives (estrogen plus a progestin), progestins (such as medroxyprogesterone), danazol (a synthetic hormone related to testosterone), and gonadotropin-releasing hormone agonists (GnRH agonists--such as buserelin, goserelin, leuprolide, and nafarelin). GnRH agonists turn off the brain's signal to the ovaries to produce estrogen and progesterone. As a result, production of these hormones decreases. Continued use of GnRH agonists causes a decrease in bone density and may lead to osteoporosis unless small doses of estrogen plus a progestin or of a progestin alone are also taken. Even when taken this way, GnRH agonists are not usually given for longer than 1 year. New types of drugs, such as GnRH antagonists, antiprogestins, and aromatase inhibitors, are being studied for the treatment of endometriosis.
Nonsteroidal anti-inflammatory drugs (NSAIDs) (see Section 6, Chapter 78) may be given to relieve pain. For persistent pain, options include surgery to remove the misplaced endometrial tissue, surgery to interrupt the nerve pathways that conduct pain sensation from the pelvic area to the brain, and surgery to do both.
Often, misplaced endometrial tissue can be removed during laparoscopy when the diagnosis is made. However, if endometriosis is moderate to severe, more extensive surgery requiring an incision into the abdomen (abdominal surgery) may be necessary. This type of surgery is usually necessary when pieces of endometrial tissue are larger than 1½ to 2 inches in diameter, when adhesions in the lower abdomen or pelvis cause significant symptoms, when endometrial tissue blocks one or both fallopian tubes, or when drugs cannot relieve severe lower abdominal or pelvic pain.
Sometimes electrocautery (a device that uses an electrical current to produce heat), an ultrasound device, or a laser (which concentrates light into an intense beam to produce heat) is used to destroy or remove endometrial tissue during laparoscopic or abdominal surgery. Doctors remove as much misplaced endometrial tissue as possible without damaging the ovaries. Thus, the woman's ability to have children may be preserved. Depending on the extent of the endometriosis, 40 to 70% of women who have surgery may become pregnant.
Surgical removal of misplaced endometrial tissue is only a temporary measure. After treatment, endometriosis recurs in most women, although the use of oral contraceptives or other drugs may slow its progression. The drugs used to suppress endometriosis may be started immediately after surgery.
Some women who have endometriosis can become pregnant through the use of assisted reproductive techniques, such as in vitro fertilization (see Section 22, Chapter 254).
Both ovaries and the uterus are removed only when drugs do not relieve abdominal or pelvic pain and the woman does not plan to become pregnant. Because removal of the ovaries and uterus has the same effects as menopause (effects that result from the decrease in estrogen levels (see Section 22, Chapter 243)), estrogen therapy may be started. Some experts recommend the use of estrogen plus a progestin (because a progestin can suppress the growth of endometriosis). When estrogen is given alone, it may be started after a delay of 4 to 6 months after surgery, because estrogen may stimulate any remaining pieces of endometrial tissue. The delay gives the endometrial tissue time to disappear.
 See the drug table Drugs Commonly Used to Treat Endometriosis.
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