What is endometriosis?

What is endometriosis?

Endometriosis is a chronic gynaecological condition in which tissue similar to the lining of the uterus (endometrium) grows outside the uterine cavity. This tissue - called an endometriotic lesion - responds to hormonal changes during the menstrual cycle just like normal endometrium: it grows each month and bleeds. Unlike the uterine lining, however, this blood has nowhere to leave the body.

The result is chronic inflammation, scar tissue and adhesions that can cause severe pain and damage surrounding organs. Endometriosis is one of the most common causes of pelvic pain and infertility in women.

Where do lesions occur?

Endometriotic lesions most commonly occur in the pelvic area:

• on the ovaries - where they may form endometriomas (cysts filled with old blood)
• on the fallopian tubes
• on the peritoneum (peritoneal endometriosis)
• between the uterus and rectum (rectovaginal septum)
• on the bladder or bowel

In rarer cases, lesions can travel via the bloodstream or lymphatic system to areas outside the pelvis - the diaphragm, lungs, and rarely even the brain or eye.

How common is endometriosis?

Endometriosis affects approximately 1 in 10 women of reproductive age. In the Czech Republic, this means hundreds of thousands of women. Globally, it is one of the most common gynaecological conditions - yet it remains significantly underdiagnosed.

The average time from first symptoms to diagnosis is 7 to 10 years. Symptoms are often overlooked or confused with "normal" menstrual pain, and endometriosis can only be reliably diagnosed by laparoscopy.

Why does endometriosis develop?

The exact cause remains unknown. Researchers work with several theories - the condition likely results from a combination of factors:

• Retrograde menstruation - menstrual blood flows back through the fallopian tubes into the abdominal cavity, where endometrial cells implant and begin to grow. Importantly, retrograde menstruation occurs in up to 90% of women, yet only some develop endometriosis - suggesting additional factors such as immune dysfunction are required.
• Genetic predisposition - endometriosis runs in families. A large genetic study involving 60,600 women with endometriosis identified a shared genetic basis for the condition and specific susceptibility loci on chromosome 7p13-15.
• Immune system dysfunction - in healthy women, the immune system destroys endometrial cells outside the uterus. In women with endometriosis, this defence fails.
• Metaplasia - normal cells in the abdominal cavity transform into endometrium-like cells. This explains cases in women after hysterectomy.
• Lymphatic and vascular spread - endometrial fragments may travel through blood vessels or the lymphatic system, explaining distant-site involvement such as the lungs or diaphragm.
• Environmental influences - some studies suggest environmental toxins may affect reproductive hormones and immune response, though this remains controversial and unproven.

Endometriosis and pain

Pain intensity does not correspond to disease extent. A woman with minimal lesions may suffer more severe pain than a woman with advanced endometriosis. Pain is therefore never a measure of disease severity.

Endometriosis can cause various types of pain:

• severe pain during menstruation
• pain during ovulation (mid-cycle)
• chronic pelvic pain outside menstruation
• pain during sexual intercourse
• pain during urination or bowel movements

Classification of endometriosis

The World Endometriosis Society (WES) consensus published in Human Reproduction recommends three main classification systems:

• Revised ASRM classification (American Society for Reproductive Medicine) - stages I to IV based on lesion extent and adhesions; recommended for all cases
• Enzian classification - specifically designed for women with deep infiltrating endometriosis
• Endometriosis Fertility Index (EFI) - for women who are interested in pregnancy

Myths and facts

• Myth: "Painful periods are normal."
  Fact: Pain that prevents you from functioning normally is not normal and deserves medical investigation. The average diagnostic delay of 7-10 years is largely caused by women and doctors minimising the pain.
• Myth: "Pregnancy will cure endometriosis."
  Fact: Pregnancy may temporarily suppress symptoms, but it does not cure the disease. Symptoms typically return after delivery and the end of breastfeeding.
• Myth: "Endometriosis shows up on a standard ultrasound."
  Fact: A standard ultrasound misses most lesions. Reliable diagnosis requires specialist ultrasound, MRI, and particularly laparoscopy with histological confirmation.
• Myth: "Endometriosis means infertility."
  Fact: Approximately 40% of women with endometriosis have fertility difficulties. Many women conceive naturally or with treatment. Early care significantly improves the chances.
• Myth: "Endometriosis only affects older women."
  Fact: Symptoms can appear in adolescence, shortly after the first period. Endometriosis in teenagers is underdiagnosed and requires attention.

When to seek help?

If you experience any of the following repeatedly, do not delay seeing a doctor:

• severe menstrual pain that disrupts your daily life
• chronic pelvic pain outside your period
• pain during sexual intercourse
• difficulty conceiving
• pain during urination or bowel movements, especially during menstruation
• significant unexplained fatigue

The earlier endometriosis is diagnosed, the more treatment options you have and the smaller the long-term consequences for your health and fertility.

Further information: endometriosis.org and worldendosociety.org.