Endometriosis explained

Endometriosis is a chronic inflammatory condition where tissue similar to the lining of the uterus is found elsewhere in the body.

This tissue is often called endometriosis tissue, endometriosis lesions, or endometriotic lesions.

It is important to understand that this tissue is similar to the lining of the uterus, but it is not exactly the same. Endometriosis is not simply “period tissue in the wrong place” and it is not just a bad period.

Endometriosis can affect the whole body. For some people, it causes severe pain and daily symptoms. For others, symptoms may come and go, or they may not realise they have it until they are investigated for something else, such as fertility problems.

Where can endometriosis be found?

Endometriosis has been found in many areas of the body. It can involve pelvic organs and tissues, and it can also affect areas outside the pelvis.

It may be found on or around:

  • the ovaries
  • the fallopian tubes
  • the outside of the uterus
  • the pelvic lining
  • the bowel
  • the bladder
  • the ureters
  • the diaphragm
  • the lungs
  • surgical scars
  • the abdominal wall
  • other abdominal or extra-pelvic sites

In very unusual cases, endometriosis has also been reported in more distant areas of the body.

This is why endometriosis should not be described as only a pelvic or period-related condition. It can affect different body systems and may need different types of specialist support.

What does endometriosis do in the body?

Endometriosis lesions can create inflammation. Inflammation is part of the body’s immune response, but when it becomes ongoing, it can contribute to pain, irritation and tissue changes.

Endometriosis can also lead to:

  • scar tissue
  • adhesions, where organs or tissues stick together
  • cysts on the ovaries, called endometriomas
  • irritation around nerves
  • bowel or bladder symptoms
  • pelvic floor muscle tension
  • fertility difficulties for some people
  • fatigue and reduced quality of life

The symptoms depend on where the disease is, how the body responds to it, and whether other conditions are also present.

The amount of endometriosis seen does not always match the amount of pain someone feels. A person with a small amount of visible disease can have severe symptoms, while someone with more widespread disease may have fewer symptoms.

Is endometriosis the same as a period problem?

No.

Periods can make endometriosis symptoms worse for many people, but endometriosis is not simply a period problem.

Some symptoms may flare around a period, but others can happen throughout the month. People with endometriosis may have pain, fatigue, bowel symptoms, bladder symptoms, nerve pain, pain during or after sex, pain with movement, or pain that continues outside their period.

Endometriosis can affect school, work, relationships, mental health, fertility and everyday life.

Pain that stops someone from living normally should not be dismissed as “just period pain”.

Common symptoms of endometriosis

Endometriosis can look different from person to person.

Symptoms may include:

  • very painful periods
  • pelvic pain
  • pain that continues outside the period
  • pain during or after sex
  • pain when opening the bowels
  • pain when passing urine
  • bowel symptoms such as bloating, constipation, diarrhoea or pain
  • bladder symptoms such as urgency, frequency or pain
  • heavy bleeding
  • spotting between periods
  • lower back, hip or leg pain
  • fatigue
  • nausea
  • fertility difficulties
  • pain around ovulation
  • pain that affects school, work, exercise or daily life

Some people also experience symptoms linked to the location of disease. For example, bowel endometriosis may cause bowel symptoms, bladder involvement may cause urinary symptoms, and diaphragm or thoracic endometriosis may cause chest, shoulder or breathing-related symptoms, especially around the menstrual cycle.

What are adhesions?

Adhesions are bands of scar-like tissue that can make organs or tissues stick together.

In endometriosis, adhesions may form because of inflammation, bleeding, healing and scarring around lesions.

Adhesions can sometimes affect how organs move. For example, they may involve the ovaries, bowel, bladder, uterus or pelvic sidewall. This can contribute to pain, pulling sensations, bowel symptoms, fertility difficulties or problems during surgery.

What are endometriomas?

Endometriomas are cysts linked to endometriosis. They are most often found on the ovaries.

They are sometimes called “chocolate cysts” because they can contain thick, old blood that looks dark brown.

Endometriomas can affect pain, ovarian function and fertility for some people. They should be assessed by a healthcare professional with appropriate experience.

What causes endometriosis?

The exact cause of endometriosis is not fully understood.

There are several theories, and research is ongoing. Endometriosis is likely to involve a combination of factors, including inflammation, immune system changes, genetics, hormones, cell behaviour and the local tissue environment.

It is important not to oversimplify the cause. Endometriosis is a complex disease, and no single explanation fully accounts for all cases.

Can teenagers have endometriosis?

Yes.

Endometriosis can affect teenagers and young people. Severe period pain, pain that causes missed school, vomiting, fainting, bowel or bladder symptoms, or pain that does not improve with basic support should not be ignored.

A young person should not have to wait years before being taken seriously.

Early support matters because symptoms can affect education, confidence, mental health and daily life.

Can endometriosis affect fertility?

Endometriosis can affect fertility for some people, but not everyone with endometriosis will have difficulty getting pregnant.

It may affect fertility through inflammation, adhesions, endometriomas, changes around the ovaries or fallopian tubes, or other factors that are still being studied.

If fertility is important to you now or in the future, it is reasonable to ask your healthcare professional how endometriosis may affect your options and whether specialist fertility advice is needed.

Is there a cure?

There is currently no known cure for endometriosis.

However, symptoms can often be managed, and many people benefit from a combination of support. This may include pain management, hormonal treatment, pelvic physiotherapy, nutrition support, fertility care, psychological support, and surgery in some cases.

The right care depends on the person, their symptoms, their goals, the location of disease, access to services and whether fertility is a priority.

Why diagnosis can take time

Endometriosis can be difficult to diagnose because symptoms vary and can overlap with other conditions.

Some people are told their pain is normal. Others are treated for bowel, bladder or muscle problems before endometriosis is considered.

Diagnosis may involve a careful symptom history, pelvic examination where appropriate, ultrasound, MRI, referral to a gynaecologist or endometriosis specialist, and sometimes surgery.

Normal scan results do not always mean endometriosis is not present. Some types of endometriosis are easier to see on imaging than others.

When to seek medical advice

You should seek medical advice if you or someone you care for has:

  • period pain that stops normal activities
  • pelvic pain that keeps coming back
  • pain during or after sex
  • pain when opening the bowels or passing urine
  • bowel or bladder symptoms that flare with the menstrual cycle
  • very heavy bleeding
  • bleeding between periods
  • ongoing fatigue with pain or heavy bleeding
  • difficulty getting pregnant
  • symptoms that are being dismissed or not improving

You deserve to be listened to. Pain that affects your life is worth investigating.

Endometriosis is real, complex and deserving of care

Endometriosis is not weakness. It is not exaggeration. It is not simply a bad period.

It is a chronic inflammatory condition that can affect different parts of the body and can have a significant impact on daily life.

Understanding what endometriosis is can help you recognise symptoms, ask better questions, prepare for appointments and seek the right support.

You do not need to know everything before asking for help. You only need to know that your symptoms matter.