Speculating on How Endometriosis Develops The Most Common Theories

Several prevalent theories exist as to why endometriosis develops in some women and not in others. Some days you may not really care how it got there; you just want it to go away! But understanding how a disease works is the first step to overcoming the problems it can bring. In this section, we review the most common theories.

Migrating out the tubes: Retrograde menstruation

Every woman with a uterus has endometrial cells (cells that line the inside of the uterus and support a pregnancy). Studies have shown that most, if not all, women also have retrograde menstruation.

What exactly is retrograde menstruation? Most of the shed endometrial lining during your period follows the route of gravity; it flows through the cervix, into the vagina, and then out into the world for you to deal with (check out Figure 4-1). The cramps you feel with your period are tiny contractions of the uterine muscle as it tries to push the blood out. However, some menstrual flow can take a wrong turn, so it ends up in the fallopian tubes and spills onto the ovaries and into the peritoneum (the membrane lining of the abdominal cavity). This process is called retrograde menstruation.

Figure 4-1:

Endometrial tissue and menstrual blood outflow into the pelvic cavity during retrograde menstruation.

Retrograde menstruation: Endometrial tissue and menstrual blood back up into fallopian tubes.

Retrograde menstruation: Endometrial tissue and menstrual blood back up into fallopian tubes.

Figure 4-1:

Endometrial tissue and menstrual blood outflow into the pelvic cavity during retrograde menstruation.

Retrograde Menstruation

Retrograde menstrual outflow into the pelvic cavity.

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Normal menstrual outflow

Retrograde menstrual outflow into the pelvic cavity.

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Normal menstrual outflow

Retrograde menstruation is one of the oldest theories describing the possible development of endometriosis. In the 1920s, Dr. John Sampson first identified retrograde menstruation as a possible explanation for endometriosis. But this theory can't be the only explanation of how endometriosis develops, because of these problems:

^ This theory doesn't explain how endometriosis ends up in places far from the pelvic cavity.

^ This theory doesn't explain why all women don't have endometriosis, because more than 90 percent have retrograde menstruation.

The following two sections look more closely at how a woman's body, combined with retrograde menstruation, can lead to endometriosis.

Pelvic abnormalities and endometriosis

Women with pelvic abnormalities (such as in Figure 4-2) are more prone to endometriosis, mostly due to mechanical factors. This fact supports the retrograde menstruation theory because these abnormalities lead to more back-flow out the tubes.

Figure 4-2:

Pelvic abnormalities may lead to more menstrual backflow.

Fallopian tube

Fallopian tube

Endometriose Grau

The following are some of the more common abnormalities that may cause endometriosis:

^ Cervical stenosis: The cervix is more tightly closed than normal. This condition can cause a greater degree of retrograde menstruation. Because blood and debris can't escape through the cervix as quickly and easily as normal, it backs up so more of it flows backwards. Studies show that around 80 percent of women with cervical stenosis develop endometriosis.

I Longer menstrual periods with heavier than normal flow: These periods can increase the chance of endometriosis in the same way as cervical stenosis. Because more than 99 percent of all menstrual flow should flow out of the vagina, only 1 percent normally goes backward, or in retrograde direction. But, if your periods are closer together, heavier, or longer lasting, you have more flow than normal. As a result, your 1 percent retrograde flow is also more than normal.

I Uterine anomalies: These anomalies can be malformations of the shape of the uterus and can also contribute to endometriosis. Approximately 2 to 4 percent of all women have some sort of uterine anomaly. Uterine anomalies that are congenital (present from birth) often arise from problems with the Mullerian ducts. (Check out the next section.)

Malformed Mullerian ducts

The top third of the vagina, cervix, uterus, and fallopian tubes develops from two tubular structures in the fetus called the Mullerian ducts. Abnormalities of this system can cause a higher risk of endometriosis. Mullerian ducts normally begin on the sides of the pelvic area and fuse in the middle, beginning at the cervix. At the top of the new uterus, these ducts separate and form the fallopian tubes that go out to the sides of the pelvis.

The most common Mullerian abnormality is a failed fusion somewhere along the way. The most likely location for the problem is the top of the uterus, where a partial separation of the body of the uterus can occur. In very rare cases, a woman can have two of everything, including a cervix, a uterus, and a tube on each side.

51 Tips for Dealing with Endometriosis

51 Tips for Dealing with Endometriosis

Do you have Endometriosis? Do you think you do, but aren’t sure? Are you having a hard time learning to cope? 51 Tips for Dealing with Endometriosis can help.

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