Endometriosis

A condition in which tissue similar to the lining of the womb grows outside it. It is common, it is frequently diagnosed years late, and the delay is usually caused by severe period pain being treated as normal.

What it is

Endometriosis occurs when tissue resembling the lining of the uterus is found elsewhere: most often on the pelvic peritoneum, the ovaries, the ligaments supporting the uterus, and sometimes the bowel or bladder. This tissue responds to hormonal signals, producing inflammation, adhesions that stick structures together, and cysts on the ovaries known as endometriomas.

Adenomyosis is a related condition in which similar tissue grows within the muscular wall of the uterus itself. It causes heavy, painful periods and a sensation of pressure, and the two often occur together.

Several explanations for how the tissue arrives there are proposed, and none accounts for every case. What is established is that the condition is inflammatory, is influenced by hormones, tends to run in families, and is not caused by anything the person did.

Symptoms

• Period pain severe enough to interfere with normal activity, often beginning a day or two before bleeding.
• Pelvic pain outside periods, which may become constant over time.
• Deep pain during or after sex, felt internally rather than at the entrance.
• Pain when opening the bowels or passing urine, particularly during periods.
• Bowel symptoms that follow the cycle, sometimes misattributed to irritable bowel syndrome.
• Heavy bleeding, or bleeding between periods.
• Difficulty becoming pregnant, which is sometimes the first thing to prompt investigation.
• Profound fatigue, which is commonly reported and rarely asked about.

The key distinction from ordinary period pain is functional: pain that stops someone attending work or school, that does not respond to standard pain relief, or that requires planning life around the cycle is not ordinary.

Why diagnosis takes so long

Several factors combine. Period pain is common, so severe pain is easily normalised, by the person as much as by clinicians. Symptoms overlap with irritable bowel syndrome and with bladder conditions. Examination is frequently normal. Ultrasound scans detect endometriomas and deep disease but often miss superficial disease entirely, so a normal scan reassures wrongly.

The practical response is to describe the impact rather than the sensation. Days missed, pain relief that does not work, the effect on sex and on work, and any bowel or bladder pattern tied to the cycle all carry more weight than an adjective.

Investigation

A history and examination come first, including a vaginal examination that may find tenderness or nodules behind the uterus. Transvaginal ultrasound is the usual first imaging test and is good at identifying endometriomas and some deep disease. Magnetic resonance imaging is used where deep disease involving the bowel or bladder is suspected.

Laparoscopy, a keyhole operation, allows direct inspection and is the definitive test. Where disease is found it can often be treated during the same procedure. Guidance in several countries now supports beginning treatment on the basis of symptoms rather than requiring surgical confirmation first, which reduces delay for many people.

There is no reliable blood test for endometriosis.

Treatment

Pain relief

Anti inflammatory pain relief taken from before the pain begins works better than the same medicine taken once pain is established. Where simple measures are not enough, a pain service may be involved, particularly where pain has become persistent rather than cyclical.

Hormonal treatment

Suppressing the cycle reduces the stimulation of the tissue and reduces pain for many people. Combined hormonal contraception, progestogen based methods including the hormonal intrauterine system, and other suppressive treatments are all used. These control symptoms rather than removing disease, and symptoms usually return when treatment stops. They are not appropriate while trying to conceive.

Surgery

Laparoscopic removal or destruction of endometriosis tissue and division of adhesions improves pain for many people, with a recognised chance of recurrence. Complex disease involving the bowel, bladder or ureters is managed in specialist centres by a team, and asking for referral to such a centre is reasonable where disease is extensive.

Hysterectomy, with or without removal of the ovaries, is sometimes discussed for severe disease. It is not automatically curative, because disease outside the uterus remains unless it is also removed, and the consequences of surgical menopause need careful discussion.

Fertility

Many people with endometriosis conceive without help. Where there is difficulty, the options include surgery and assisted conception, and a specialist assessment is appropriate rather than a long wait.

Wider support

Persistent pain changes the nervous system over time, which is why pelvic pain services, physiotherapy for the pelvic floor, and psychological support for pain management are part of care rather than an admission of defeat. Muscle guarding secondary to years of pain is extremely common and treatable in its own right. See an overactive pelvic floor.

Living with it

Symptoms fluctuate, and planning around a predictable bad week is reasonable. Keeping a symptom and pain record is genuinely useful for appointments, because it converts an impression into a pattern. Menopause often reduces symptoms, though not invariably, particularly where hormone therapy is used.

Last reviewed: September 2026