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This page contains basic information about endometriosis and explains the condition in a simple way. This site should only be used to gather information and never as a diagnostic or treatment tool.

It is advisable that you refresh your memory about the endomtrium and menstruation at the female organs and normal menstruation. It is important to understand the endometrium and normal menstruation to be able to understand endometriosis.

Endometriosis is a common disease , but unfortunately one of the most difficult conditions to explain to lay persons. On this page this disease will be explained in a simple manner. Please refer to the pages where the female organs (Click here) and the normal menstruation(Click here) are discussed.

The name endometriosis is derived from the term endometrium. The endometrium is the lining covering the cavity inside the womb. Refer to the page The Female Organs. The changes occurring in the endometrium during the menstrual cycle is responsible for menstruation.

Endometriosis develops when tissue resembling the endometrium starts growing outside the womb. The most common symptoms are period pains, tummy pain, painful sexual intercourse and infertility.

There are different theories about the causes of endometriosis , but to simplify the discussion we will concentrate on retrograde menstruation as a possible cause. ( it refers to backward menstruation through the fallopian tubes into the peritoneal cavity).

The womb is a hollow organ with three openings into its cavity. The cervix (mouth) at the bottom opens into the vagina and two openings ( one on each side ) at the upper end connects to the fallopian tubes.

During menstruation the thick premenstrual endometrium is discarded and breaks into pieces. The pieces are discarded with the menstrual fluid into the vagina. Menstrual blood however also escapes trough the upper openings of the womb into the fallopian tubes. The outer opening of the tubes open directly in the peritoneal cavity. (Click here for more information about the peritoneal cavity).

The menstrual fluid consists of blood, endometrial epithelium, endometrial glands, pieces of blood vessels and connective tissue. All these tissue parts are pieces of the discarded endometrium. These pieces find there way into the peritoneal cavity. In some persons these pieces attach themselves to the peritoneum ( the layer covering the peritoneal cavity) and start growing. This will only happen in some individuals and the reasons why are still obscure. The endometrium is now present and growing in a foreign site and is now known as endometriosis.

The diagnosis depends on suspicion ( symptoms of lower tummy pain, painful sexual intercourse, period pains and infertility) and is confirmed with a laparoscopy. There are different laparoscopic appearances but that is beyond the scope this site. It is sufficient to say that most lesions will be recognized by an experienced gynecologist.

Treatment should be discussed and conducted in consultation with a gynecologist. The options available are surgical destruction of the lesions, medical treatment or both. The medical treatment consists of drugs that suppress the endometrium and keep it thin (atrophic) . These drugs usually suppress the ovaries and prevents the release of estrogen. It is important to remember that prolonged medical treatment might have an effect on bone density. The best way to describe it is to imagine the body in a state of artificial menopause during the treatment. The lesions are also suppressed and this allows the body to heal them.

A Graphic Presentation of Endometriosis
This drawing shows a menstruating uterus and illustrates bleeding through the tubes into the peritoneal cavity. This is known as retrograde menstruation. ( Backward menstruation into the peritoneal cavity.) The menstrual blood also contains endometrial epithelium (covering cells) and pieces of glands , blood vessels and connective tissue. All the ingredients necessary to start a new endomtrium.
This drawing is basically the same as the previous one. The only difference is that it gives a side view. It illustrates how menstrual blood collects behind the uterus and above the utero sacral ligaments. ( see utero sacral ligaments on the glossary page.
On the next few pages endometriosis will be explained in more detail. Many of the aspects already mentioned will be repeated.

It is a very difficult disease to explain to people without a medical background.

It is important to remember that the menstrual fluid contains all the elements necessary to construct an endomtrium. It contains the surface epithelium cells, the glands and blood vessels. To see an explanation of the microscopic structure of the endometrium ( simplified off course) click here .

Due to some still unknown reasons , the endometrial elements in the menstrual fluid will start growing in areas that came into contact with the menstrual fluid. (Ovaries, tubes, the peritoneum in the pouch, on the utero sacral ligaments etc.). This will only happens in some individuals. We are still uncertain why only in some.

These abnormal endometrial tissue will continuously increase in size and also invade the deeper laying tissues. All the monthly changes that occur in the normal endometrium ( see normal menstruation ) , also occur in the abnormal endometrium.

Graphical explanation of how the Endometriosis developes
1) A drop of menstrual fluid drips from the fimbrial opening of the tube. (retrograde menstruation)

2) The menstrual fluid comes into contact with the peritoneum.

3) The endometrial components in the fluid start forming a new endometrium.

4) The new endometrium is in a foreign site . It cannot establish contact with the muscle layer of the womb (uterus) and the edges curl inwards.

5) A endometrioma ( endometrial lesion ) forms.

6) It menstruates monthly and grows larger and it also invades the the deeper layers of the peritoneum.

7) Pressure inside the lesion increases over months due to the continuous menstruation. Some of the lesions might rupture (burst open) and there contents might spread to form new lesions.

8) The ruptured lesions forms rough areas to which other organs ( bowel, fallopian tubes) might adhere to , forming adhesions.

9) Longstanding adhesions between endometriosis and bowel.

Further Graphic Explanations of Endometriosis
The following drawings attempt to explain this in a simple manner. To understand the meaning of these drawings, it is important to have an idea about the peritoneal cavity and the peritoneum.

Bleeding through the fallopian tubes spills blood into the peritoneal cavity. The endometrial tissue present in the blood starts invading the peritoneal membrane and spreading along it. Probably due to its presence in a foreign site the endometrial tissue behaves differently. It does not spread to cover a surface but instead it curls and forms small sphere like structures. A type of menstruation will occur inside these spheres. They will gradually grow larger and eventually some will rupture. When they rupture, endometrial building blocks are released into the peritoneal cavity and this also helps the disease to spread. The ruptured endometrial nodules also cause adhesions. Refer to "Adhensions explained".

The following drawing illustrates the intact uterus and ovaries. The vagina is removed. The blue layer surrounding the uterus is the peritoneum. The peritoneum covering most of the uterus is densely adherent to the muscle and therefore represent buy a different color.

The previous drawing should be used as a guide to understand the next one better. The next drawing shows the purple nodules representing endometriosis occurring on the peritoneum next to the uterus , on the tubes and on the ovaries.

The abnormal endometrium is also under hormonal control and the same changes that occur in the normal endometrium occur in the abnormal endometrium. The next illustrations show a nodule in the different stages of menstruation. This nodule is situated on peritoneum as illustrated in the next drawing.

The next drawing shows a cross section through this module just after a menstration

The purple line represents the endometrial epithelium cells and the blue line the peritoneum. Because the endometrium is in a foreign region and not in contact with the muscle of the uterus (womb), the epithelium curls at the edges. The edges meet and a spherical structure is formed. If endometrium

The following drawing shows a cross section through the lesion at the time of ovulation.The endometrium is thick and resembles the normal menstruation just before ovulation occurs.

The next drawing shows a cross section through a lesion just before the onset of menstruation. The abnormal endometrial tissue resembles the normal premenstrual endometrium with increased blood flow, spiral arteries and increased glandular secretions.

The next drawing shows a cross section through a menstruating lesion. Menstruation occurs in the abnormal endometrium in the same way and at the same time when it occurs in the uterus.

The menstrual cycle will repeat over and over and as it does the lesions grow bigger . It is obvious that tissue damage with subsequent pain and other symptoms will follow.

The only reliable way to diagnose this disease is to see the lesions and to take biopsies ( tissue samples). This is usually done by doing a laparoscopy. A detailed discussion of the treatment is beyond the scope of this site. The treatment depends on two methods namely surgical destruction of the lesions and medical suppression of female hormonal activity. The latter causes the endometrium to become atrophic ( very thin and inactive) this allowing the body to destroy the abnormal endometrium. A combination of both methods is often used.


Endometriosis: Lighting the Path

The 2002 Official Patient's Sourcebook on Endometriosis