Anne had never had problems with her periods the way some of her friends did. But over time her periods started getting so painful that she dreaded their arrival. Every month for a few days she would curl up on the couch with a heating pad and take a pain reliever. The cramps eventually became so bad that she was missing school a couple of days a month, and the pain even started happening between periods.

It is not known exactly how many women have endometriosis, but it is believed that more than 5 million American women, including teen girls, are affected. Its not always diagnosed right away in teens because at first they or their doctors assume that their painful periods are a normal part of menstruating, or that their abdominal pain is due to another problem. But continuing, excessive pain that limits activity isnt normal and should always be taken seriously. Because severe endometriosis can make it harder for a girl to have children in the future, its a good idea to get medical help for endometriosis and not wait too long.

Because the abnormal growths associated with endometriosis are made up of the same kind of tissue and blood vessels found in the uterine lining, any endometrial implants will act just like the endometrium in the uterus. That means they respond in the same way to the hormonal changes of the menstrual cycle.

However, in the uterus, if the egg isnt fertilized, the extra tissue and blood leave a girls body in the form of menstrual fluid. With endometriosis, though, theres nowhere for the accumulating blood and tissue to go once the implants start to break down. This causes irritation of the surrounding body parts, which can cause pain. With continued build up and irritation, the symptoms of endometriosis tend to become more painful over time.

Doctors arent sure what causes endometriosis. They do know that it is slightly more common in teens and women who have a family member who has been diagnosed with endometriosis.

There are several theories about how the endometrial tissue actually gets outside the uterus in the first place. One theory suggests that the menstrual blood flow somehow "backs up" into the fallopian tubes, carrying some tissue from the uterine lining with it. In effect, the tissue gets transplanted and starts growing outside the uterus.

Another theory is that endometrial tissue cells travel out of the uterus through blood or lymph vessels, and then start growing in the new locations where theyre deposited. Yet another theory suggests that some girls are born with "misplaced" cells that can turn into endometrial implants later in life. Scientists continue to research the condition to help doctors fully understand and treat it.

The most common sign of endometriosis is severe pelvic (lower abdominal) pain. It may occur occasionally or constantly, and it may be associated with a girls period. Although slight cramps for a couple of days before or during a menstrual period are normal, lasting or intense pain that disrupts a girls day is not. With endometriosis, the pain is usually so bad that it causes a girl to miss school, sports, and social activities.

Diagnosing endometriosis isnt always easy. Lots of things can cause pelvic pain, so even if a girls symptoms point to endometriosis, a doctor may want to rule out other possibilities.

In addition to doing a physical exam, the doctor will take your medical history by asking you about any concerns and symptoms you have, your past health, your familys health, any medications youre taking, any allergies you may have, and other issues. The doctor may ask about your periods and whether you have had sex. Its important to answer all of these questions honestly so your doctor can figure out whats going on.

Depending on your symptoms, the doctor might ask you to keep a pain diary, which may involve recording this information every time you experience pain:

The severity of the pain isnt always an indication of how severe the endometriosis might be. A girl may have many growths and just a little pain or a few growths and a great deal of pain. Every girls situation is a little bit different.

The only way to know for certain whether a girl has endometriosis is to perform a minor surgical procedure called laparoscopy (pronounced: la-puh-ras-kuh-pee). This allows the doctor to know for certain whether a girl has endometrial implants and, if so, how extensive they are.

While a girl is under anesthesia, the doctor makes a small cut near her belly button and inserts a thin, lighted tube (known as a laparoscope) that acts as a tiny video camera so that the doctor can view the pelvic organs. During the procedure, the abdomen is filled with a gas to help the doctor see the organs better. The doctor may also do a biopsy, which means removing small pieces of the growths for examination under a microscope. If endometrial implants are seen, the doctor might be able to remove them.