Endometriosis

What is endometriosis?

The uterus is lined by the endometrium, which thickens each month and is shed as a period. In endometriosis, similar tissue sits outside the uterus. It responds to estrogen, so it grows and bleeds with the cycle, but the blood has nowhere to go. This triggers inflammation, nerve sensitization and scar tissue (adhesions) that can glue organs together.

Common sites:

• The peritoneum, the thin lining of the pelvis
• The ovaries, where blood-filled cysts called endometriomas ("chocolate cysts", from their dark brown fluid) form
• The ligaments behind the uterus and the space between the uterus and rectum
• The bowel and bladder in deep disease
• Rarely, the diaphragm, lungs, surgical scars or belly button

Endometriosis is different from adenomyosis, where the lining tissue grows into the muscle wall of the uterus. The two often occur together.

Endometriosis symptoms

Symptoms vary widely. The amount of disease seen at surgery does not match the pain well: some people with small patches have severe pain, and some with large cysts have none.

• Painful periods (dysmenorrhea): cramps that start before bleeding, last throughout, and do not settle with usual pain relief. Pain that gets worse over the years is typical.
• Chronic pelvic pain: aching or stabbing pain in the pelvis or lower back between periods.
• Deep pain during sex: felt inside, often lasting hours afterward.
• Bowel symptoms: painful bowel movements, bloating, diarrhea or constipation around periods. These are often misdiagnosed as irritable bowel syndrome.
• Bladder symptoms: pain when the bladder is full, urgency, and occasionally blood in the urine during periods.
• Heavy or irregular bleeding and spotting before periods.
• Fatigue, which many people describe as one of the most disabling symptoms.
• Difficulty getting pregnant.

Learn how to tell ordinary cramps from warning signs on our page about painful periods.

What causes endometriosis?

The exact cause is unknown. Several mechanisms probably combine:

• Retrograde menstruation: some menstrual blood flows backward through the fallopian tubes into the pelvis. This happens in most people, so other factors must decide who develops disease.
• Immune factors: the immune system may fail to clear misplaced cells.
• Cell transformation: cells in the pelvic lining may change into endometrium-like cells.
• Spread through blood or lymph, which explains distant sites.
• Genetics: having a mother or sister with endometriosis raises your risk several times.

Risk factors

• Close relative with endometriosis
• Periods starting early, short cycles (under 27 days) or long, heavy periods
• Never having given birth
• Conditions that block menstrual outflow
• Low body weight

Stages and types of endometriosis

The American Society for Reproductive Medicine (ASRM) system scores what the surgeon sees:

The stage describes extent, not pain. Stages I and II are covered in detail on our mild endometriosis page.

Doctors also describe three types: superficial peritoneal disease, ovarian endometriomas, and deep endometriosis that invades more than 5 mm into tissue such as the bowel, bladder or ligaments.

How endometriosis is diagnosed

Diagnosis often takes 7 to 10 years from first symptoms, partly because period pain is normalized. Current guidelines encourage doctors to start treatment based on symptoms without waiting for surgery.

1. History: the pattern of pain, how it relates to your cycle, bowel and bladder symptoms, and family history.
2. Pelvic exam: tenderness, nodules behind the uterus or a fixed, tilted uterus suggest deep disease. A normal exam does not rule it out.
3. Transvaginal ultrasound: reliably finds endometriomas and, with an experienced sonographer, deep disease. It usually misses superficial patches.
4. MRI: maps deep disease before surgery.
5. Laparoscopy: keyhole surgery through the belly button lets the surgeon see and sample lesions. It is the only way to confirm superficial disease and can treat it at the same time.

No blood test diagnoses endometriosis. CA-125 can be raised but is not specific.

Endometriosis treatment

Treatment depends on your main goal: pain control, fertility, or both. Endometriosis tends to return after stopping treatment, so most people need a long-term plan.

Pain relief

• NSAIDs such as ibuprofen or naproxen at the label dose, started a day before the period. Avoid them if you have stomach ulcers or kidney disease.
• Heat, regular exercise, pelvic floor physical therapy and good sleep help many people.

Hormonal treatment

These lower estrogen or stop periods, which quiets lesions:

• Combined birth control pills, often taken continuously to skip periods
• Progestins: dienogest, norethindrone, the hormonal IUD or the contraceptive implant
• GnRH antagonists or agonists (for example elagolix, relugolix combination or leuprolide), which create a temporary low-estrogen state. "Add-back" hormone is given to protect bones and reduce hot flashes.

Hormones do not remove existing lesions and are not used while trying to conceive.

Surgery

• Laparoscopic excision or ablation removes or destroys lesions and adhesions and improves pain for most people, though symptoms return in a significant number within 5 years, less often with ongoing hormonal suppression.
• Endometrioma surgery removes the cyst wall, balancing pain relief against loss of ovarian egg reserve.
• Hysterectomy, sometimes with removal of the ovaries, is an option for people who do not want future pregnancy and have severe disease, but it does not guarantee cure if lesions outside the uterus remain.

Deep bowel or bladder disease is best treated at a specialist endometriosis center.

Endometriosis and pregnancy

Many people with endometriosis conceive naturally. Others have reduced fertility because of adhesions that distort the tubes, inflammation affecting eggs and sperm, or lower ovarian reserve after endometriomas. Options include surgery for minimal-to-mild disease, intrauterine insemination, and IVF, which is the most effective for advanced disease or other fertility factors. See our page on female infertility for the wider workup.

Symptoms often ease during pregnancy and breastfeeding, but pregnancy is not a cure, and pain usually returns afterward.

Complications and related conditions

• Infertility
• Ovarian cysts that can rupture or twist
• Bowel or ureter blockage from deep disease (rare)
• Chronic pain, anxiety and depression
• A small increase in risk of certain types of ovarian cancer (clear cell and endometrioid). The absolute risk stays low.

Endometriosis also overlaps with chronic pelvic pain, interstitial cystitis, migraine and fibromyalgia, which may need their own treatment.

Living with endometriosis

Symptoms usually improve after menopause as estrogen falls, although hormone therapy can reactivate disease in a few people. Until then, a pain diary, a doctor experienced in endometriosis, and a combination of medical, physical and psychological support give the best results. Many people manage well with one long-term hormonal method.

Frequently asked questions

What are the first signs of endometriosis?

The first sign is usually period pain that is severe, starts in the teen years, and gets worse over time rather than better. Other early clues are pain during sex, painful bowel movements during periods, missing school or work each month, and pain relievers that no longer help.

Can endometriosis be cured?

Not permanently at present. Surgery removes visible lesions and hormones suppress growth, so most people get good control, but disease and pain can return. Symptoms generally settle after menopause. Long-term hormonal suppression after surgery lowers the chance of recurrence.

Does endometriosis show up on an ultrasound?

Sometimes. Ovarian endometriomas show up clearly, and deep nodules can be seen by an experienced specialist. Small superficial patches, the most common type, are usually invisible on ultrasound and MRI. A normal scan does not rule endometriosis out.

Can you get pregnant with endometriosis?

Yes. Many people with endometriosis conceive without help. Fertility can be reduced, especially with moderate or severe disease. If you have tried for 12 months (6 months if you are 35 or older), or know you have endometriomas, ask about a fertility assessment early.

Is endometriosis hereditary?

It runs in families. Having a mother or sister with endometriosis increases your risk several times. Many genes each contribute a small amount, so there is no single genetic test for it.

What does endometriosis pain feel like?

People describe deep cramping, stabbing or burning pain in the lower belly, pelvis or lower back, sometimes spreading down the legs. It is often worst just before and during periods, but can be present all month, and may come with pain during sex, bowel movements or urination.