What is Endometriosis

What is endometriosis? 

It is a condition where pieces of tissue similar to the lining of the uterus are present in places outside the uterus, where they shouldn’t be, usually in the pelvis. This tissue is like the tissue lining the uterine cavity, it looks similar under the microscope but according to gynaecology specialists it is not the same.

Patches or areas of endometriosis are known as lesions. A lesion is a medical word for an area of abnormality.

Endometriosis is a problem because it can lead to pain or scarring.

It is usually present on the peritoneum, which is the lining of the pelvic cavity. The commonest site for endometriosis is within the pelvic cavity. Typically, endometriosis lesions a present as small spots on the side walls of the pelvis, or on the surface of the pelvic organs etc.) These organs include the outside of the uterus, the ovaries, fallopian tubes, bowel, bladder, ureter and appendix. In more severe cases endometriosis can grow into the pelvic organs. However, it is important to note that endometriosis is not cancerous.

The organs of the pelvis are lined with a shiny membrane called the peritoneum. The peritoneum also lines the inside of the pelvic cavity and the abdomen. Most lesions of endometriosis are found on or within the peritoneum. When viewed directly through a laparoscope, endometriosis lesions are found to consist of different shapes, sizes and colours. Endometriosis is thought to be a different colour depending on the stage of development of the endometriosis. The different appearances are as follows:

Red lesions: These contain blood vessels, and have the appearance of small raised lumps. They sometimes look like a group of blood vessels. It is thought that red lesions may be the first stage in the development of endometriosis.

Clear lesions: These have the appearance of very small bubbles. They are a form of early endometriosis and can be difficult to visualise.

Black lesions: The peritoneum around endometriosis is irritated, causing scarring. Blood which is trapped within the scar tissue becomes black over time.

White lesions: Gradually, the scar tissue formed around the endometriosis blocks the blood vessels. The blood is reabsorbed by the body and a white scar is left.

Endometriosis or chocolate cysts: These are large clumps of endometriosis that form inside an ovary. 

Peritoneal pockets or windows: These are areas that appear like a dent in the surface of the peritoneal lining. They are usually oval-shaped.

Invisible areas: If biopsies are taken of what looks like normal peritoneal lining, sometimes microscopic patches of endometriosis are found when examined under a microscope. This is especially likely when biopsies are taken in the region around obvious patches of endometriosis.

Young women tend to have clear, pink or red lesions of endometriosis. These are known to be the most active forms of endometriosis and they are the type most likely to lead to pelvic pain. They are also the most difficult lesions to identify during a pelvic laparoscopy. Older women usually have brown, white or black lesions. These have usually been present for a longer period of time.

Most lesions of endometriosis are small and thin. They usually measure 1-2 mm in diameter. Thicker and larger lesions are known as nodules. These usually measure from a few millimetres to a few centimetres across.

Chocolate cysts

These are the largest type of endometriosis lesions. They can measure up to several centimetres across. The fluid inside the cyst is dark brown and looks quite like chocolate sauce. A chocolate cyst is also known as an endometrioma, endometrioid cyst or endometrial cyst.

Mild endometriosis.

This is when a woman has only a few lesions of endometriosis. Her endometriosis may cause any problems and it may have been diagnosed incidentally during an operation carried out for another reason, such as a laparoscopic sterilisation.

Moderate endometriosis.

This lies between mild and severe endometriosis.

Severe endometriosis.

If a woman has many lesions or if the lesions are large then the endometriosis is severe.

The lesions are nearly always found within the pelvis. However, rarely lesions may be present in unusual places such as the umbilicus (navel or belly button), within a previous caesarean section scar or in the lungs. Very rarely they have been found in men who have taken oestrogen hormone treatments.

Endometriosis is particularly prevalent in Western countries. However it may be found throughout the world and amongst women of all ethnic backgrounds.

As mentioned above, it is important to emphasise that, although it may spread, endometriosis is not a form of cancer.

The word endometriosis is derived from the medical word for the lining of the womb (uterus) which is endometrium.’Endo’ means inside and ‘metra’ means uterus.The endometrium is the lining of the uterus that grows each month and then is shed each month causing a menstrual period. Although they appear similar under a microscope, a lesion of endometriosis is not the same as the lining of the uterus. The lesions of endometriosis rarely bleed and make different hormones from the normal endometrium.