Endometriosis vs Adenomyosis: What’s the Difference?

12 min read · Updated September 2026 · Educational content only — not medical advice

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Endometriosis vs Adenomyosis: What’s the Difference?

Endometriosis and adenomyosis are easy to confuse. Both can cause severe menstrual cramps, persistent pelvic pain and pain during sex. Both can also occur in the same person.

But anatomically, the difference is straightforward.

Endometriosis is a chronic condition in which tissue similar to the lining of the uterus develops outside the uterus. Lesions are commonly found within the pelvis, including around the ovaries, peritoneum and other pelvic structures, and can sometimes involve the bowel, bladder or areas outside the pelvis.

Adenomyosis occurs when endometrial-type tissue is present within the myometrium — the muscular wall of the uterus.

That one distinction explains much of the difference between the two conditions, but symptoms overlap enough that you cannot reliably tell them apart from pain alone.

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In short

• Endometriosis occurs outside the uterus; adenomyosis occurs within the muscular wall of the uterus.

• Both can cause painful periods, chronic pelvic pain and pain during sex.

• Heavy menstrual bleeding is especially associated with adenomyosis, although bleeding changes can occur with endometriosis too.

• Bowel or bladder symptoms that worsen around menstruation can raise suspicion for endometriosis, particularly when lesions affect those areas.

• Ultrasound and MRI can help identify both conditions, but a normal ultrasound does not rule out endometriosis.

• You can have endometriosis and adenomyosis at the same time.

• Neither condition can be diagnosed from symptoms alone.

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The simplest way to understand the difference

Imagine the uterus as having an inner lining and a thick muscular wall.

The inner lining is called the endometrium.

The muscle surrounding it is the myometrium.

In adenomyosis, endometrial-type glands and tissue are found inside that muscular wall.

In endometriosis, endometrial-like lesions exist outside the uterus altogether.

That can include the ovaries, pelvic lining and structures around the uterus. Deep endometriosis can involve areas such as the bowel, bladder or ureters.

They are therefore distinct diseases rather than two different stages of the same condition.

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Endometriosis: tissue outside the uterus

Endometriosis is a chronic inflammatory disease involving endometrial-like tissue outside the uterus. WHO estimates that it affects around 10% of reproductive-age women worldwide.

The lesions can trigger inflammation and contribute to scarring and adhesions — bands of scar tissue that can cause pelvic structures to stick together.

Endometriosis can look very different from one person to another.

Some people have extensive disease with surprisingly little pain. Others have significant pain even when relatively little disease is visible.

The severity of pain therefore does not reliably tell you how extensive the endometriosis is.

Common symptoms of endometriosis

Symptoms can include:

• very painful periods

• pelvic pain outside menstruation

• pain during or after sex

• painful bowel movements, particularly around a period

• pain when urinating during menstruation

• bloating, diarrhea, constipation or nausea around periods

• difficulty becoming pregnant

• fatigue

• abnormal bleeding patterns

Not everyone has all of these symptoms, and some people with endometriosis have few or no noticeable symptoms.

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Adenomyosis: tissue within the uterine muscle

Adenomyosis affects the uterus itself.

Endometrial-type tissue is present within the myometrium, where it can be associated with changes in the surrounding muscle. Imaging may show features such as small myometrial cysts, an irregular junctional zone, asymmetrical thickening or a more globular uterine shape.

Some people have widespread — or diffuse — adenomyosis, while others have more localized disease.

And just like endometriosis, adenomyosis does not always cause symptoms.

Common symptoms of adenomyosis

When symptoms occur, they can include:

• painful periods

• heavy menstrual bleeding

• chronic pelvic pain

• pain during sex

• a feeling of pressure, heaviness or fullness in the lower abdomen

• bloating

Heavy and painful menstruation are particularly characteristic symptoms.

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Endometriosis vs adenomyosis symptoms

The overlap is substantial, which is why symptoms alone cannot reliably determine which condition you have.

These patterns can help guide an evaluation, but none of them is diagnostic by itself.

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Quick distinction

Painful periods + cyclical bowel or bladder pain may make endometriosis more suspicious.

Painful periods + consistently heavy bleeding + uterine pressure or fullness can fit adenomyosis particularly well.

But real cases often do not follow textbook patterns — and both conditions can exist together.

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Can you have endometriosis and adenomyosis at the same time?

Yes.

These conditions are distinct, but they can coexist.

Research populations differ substantially in how the conditions are diagnosed and which patients are studied, so there is no single reliable percentage that applies to everyone. However, concurrent endometriosis and adenomyosis is well recognized clinically and in research. A 2026 systematic review also found that having both conditions may be associated with greater reproductive challenges than either condition alone, although the available fertility and pregnancy evidence remains heterogeneous.

This matters because finding one condition does not automatically explain every symptom.

Someone diagnosed with endometriosis who also has very heavy bleeding, for example, may still warrant evaluation for adenomyosis or another cause of abnormal bleeding.

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How endometriosis is diagnosed

Endometriosis diagnosis has changed significantly from the old idea that everyone needs surgery before the condition can even be considered real.

ACOG's 2026 diagnostic guideline supports a clinical or presumptive diagnosis based on history, symptoms, examination and imaging in appropriate patients, allowing treatment to begin without automatically requiring diagnostic surgery first.

Your symptom history matters

A healthcare professional may ask about:

• when the pain occurs

• whether it has worsened over time

• pain during sex

• bowel or bladder symptoms

• bleeding patterns

• fertility history

• how symptoms affect work, school, sleep and everyday activities

• family history of endometriosis

NICE specifically recommends asking about first-degree relatives because having a close family member with endometriosis increases its likelihood.

Ultrasound

Current NICE guidance recommends transvaginal ultrasound for people with suspected endometriosis, even when the pelvic examination appears normal.

Ultrasound can identify ovarian endometriomas, some forms of deep endometriosis and other conditions that might explain symptoms.

But this point is crucial:

A normal ultrasound does not rule out endometriosis.

Superficial disease in particular can be difficult to see with routine imaging. NICE explicitly recommends that clinicians continue to consider endometriosis when symptoms are suggestive despite normal examination and ultrasound findings.

MRI

Specialist pelvic MRI can be useful when deep endometriosis is suspected or when clinicians need to map how extensively disease may involve surrounding structures.

Laparoscopy

Laparoscopy — keyhole surgery used to inspect the pelvis directly — still has an important role.

NICE recommends considering diagnostic laparoscopy when endometriosis remains suspected, including in some people whose ultrasound or MRI is normal. Biopsy may be taken from suspicious lesions.

But surgery is no longer appropriately described as the only legitimate route to an endometriosis diagnosis.

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How adenomyosis is diagnosed

Adenomyosis historically had a different problem.

For many years, the most certain diagnosis was made by examining the uterus after hysterectomy. That meant adenomyosis was often thought of primarily as a disease identified in people later in reproductive life.

Modern imaging has changed that.

Current adenomyosis guidance recognizes transvaginal ultrasound and MRI as diagnostic tools, meaning the condition can now be identified without removing the uterus.

Transvaginal ultrasound

Ultrasound is usually the practical first-line imaging test.

Specialists look for a combination of features rather than one single definitive sign.

The revised MUSA consensus divides ultrasound findings into direct features, which more directly suggest endometrial tissue within the myometrium, and indirect features, reflecting changes in the uterine muscle.

Examples include:

• myometrial cysts

• echogenic islands

• subendometrial lines or buds

• a globular uterine shape

• asymmetrical wall thickening

• an irregular or interrupted junctional zone

• fan-shaped shadowing

No individual ultrasound sign is perfectly diagnostic on its own.

MRI

MRI can provide additional information when ultrasound findings are uncertain, anatomy is difficult to evaluate or more detailed mapping is useful. Both ultrasound and MRI are recognized imaging options in current adenomyosis guidance.

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Does one condition cause heavier periods?

Both can involve abnormal bleeding, but heavy menstrual bleeding is more strongly characteristic of adenomyosis.

Adenomyosis changes the muscular wall of the uterus and is recognized in guidelines as a possible cause of heavy menstrual bleeding as well as painful periods.

Endometriosis can occur alongside heavy bleeding, and WHO lists heavy menstrual bleeding among possible symptoms. But heavy flow itself is not specific enough to identify either condition.

Heavy periods can also have many unrelated causes, including fibroids, problems with ovulation and bleeding disorders.

That is why pain + heavy bleeding does not automatically equal adenomyosis.

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Which causes worse pain?

There is no useful answer.

Both conditions can cause mild symptoms in one person and debilitating pain in another.

Pain severity also does not reliably indicate how anatomically extensive a condition is.

This is particularly important with endometriosis, where treatment decisions should be guided by symptoms, preferences and priorities rather than assuming a simple relationship between disease “stage” and pain. NICE explicitly recommends treating according to symptoms and priorities rather than the endometriosis stage alone.

The practical question is not which disease is objectively more painful.

It is how much your symptoms are affecting your life.

How treatment differs

There is considerable overlap in symptom management, but treatment goals are not identical.

Endometriosis treatment

Management depends on pain, the location and extent of disease, previous treatments and whether pregnancy is a current goal.

Options can include:

• NSAIDs and other pain management

• hormonal contraceptives

• progestin-based therapies

• medications that suppress ovarian hormone activity, including GnRH-based treatments

• laparoscopic surgery to remove or destroy endometriosis lesions

• fertility treatment when needed

NICE recommends discussing both symptoms and fertility priorities when selecting treatment.

Importantly, hysterectomy is not inherently a cure for endometriosis, because endometriosis lesions exist outside the uterus and symptoms may persist even after the uterus is removed. WHO specifically cautions that symptoms can remain after hysterectomy.

Adenomyosis treatment

Treatment is tailored to whether the primary issue is heavy bleeding, pain, fertility concerns or a combination.

Options may include:

• NSAIDs for pain

• tranexamic acid for heavy bleeding

• a levonorgestrel-releasing intrauterine system

• combined hormonal contraception

• progestin therapy

• other hormone-suppressing treatments

• selected interventional or surgical treatments

Hysterectomy may be considered when symptoms are severe and other approaches have not worked in someone who does not wish to preserve the uterus.

Because adenomyosis exists within the uterus itself, removing the uterus removes the adenomyotic tissue. That is fundamentally different from endometriosis, which may remain elsewhere in the pelvis or body.

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Why this matters

A treatment can make menstrual pain easier to manage without treating the underlying condition itself.

Heat, pain medication and electrical nerve stimulation, for example, may be useful symptom-management tools for pelvic or menstrual pain. They do not remove endometriosis lesions or adenomyosis.

Relieving pain and investigating why severe pain is happening are separate goals.

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What about fertility?

Both conditions have been associated with fertility problems, but the evidence is stronger and more established for endometriosis.

Endometriosis can affect fertility through several possible mechanisms, including inflammation, adhesions, ovarian involvement and anatomical changes within the pelvis. WHO recognizes infertility as an important manifestation of endometriosis.

Adenomyosis has increasingly been associated with reduced fertility and adverse reproductive outcomes as diagnosis by imaging has improved. The 2023 Canadian adenomyosis guideline includes infertility among the outcomes that may influence management.

However, reproductive outcomes depend on many factors beyond either condition, including age, ovarian reserve, sperm factors and other reproductive conditions.

Having endometriosis or adenomyosis therefore does not mean pregnancy is impossible.

If pregnancy is a priority and conception is taking longer than expected, management may need to involve a fertility specialist rather than focusing only on pain or bleeding symptoms.

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When to talk to a healthcare professional

Period pain deserves evaluation when it is persistently interfering with everyday life rather than only when it becomes unbearable.

Consider discussing your symptoms with an ob-gyn or another healthcare professional if:

• period pain is severe or becoming progressively worse

• pain regularly causes you to miss work, school or normal activities

• you have pelvic pain outside your period

• sex is consistently painful

• bowel movements or urination become painful around menstruation

• your periods are unusually heavy or have become substantially heavier

• you repeatedly experience pelvic pressure or fullness

• you are having difficulty becoming pregnant

• symptoms persist despite treatments that previously helped

NICE recommends referral for suspected endometriosis when symptoms have a detrimental impact on daily life, are persistent or recurrent, or initial treatment is ineffective or not tolerated.

Seek more urgent medical assessment for sudden severe pelvic pain, particularly if pregnancy is possible, or if heavy bleeding is accompanied by fainting, marked dizziness, weakness, shortness of breath or feeling seriously unwell.

These symptoms have multiple possible causes and should not simply be assumed to be endometriosis or adenomyosis.

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The bottom line

The easiest way to remember the difference is location:

Endometriosis = endometrial-like tissue outside the uterus.

Adenomyosis = endometrial-type tissue within the muscular wall of the uterus.

Their symptoms overlap considerably, so painful periods alone cannot tell you which condition — if either — is present. Heavy bleeding and uterine pressure may point more toward adenomyosis, while cyclical bowel or bladder symptoms can raise suspicion for endometriosis, but neither pattern is diagnostic.

Modern diagnosis is also less invasive than many outdated explanations suggest. Ultrasound and specialist imaging play increasingly important roles in both conditions, and a presumptive diagnosis of endometriosis can sometimes be made without surgery. At the same time, a normal ultrasound does not automatically exclude endometriosis.

If pain or bleeding repeatedly changes the way you live your life, finding the underlying reason matters more than deciding whether your symptoms fit one perfect checklist.

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Sources & References

American College of Obstetricians and Gynecologists (ACOG). Diagnosis of Endometriosis. Clinical Practice Guideline No. 11. 2026.
ACOG — Diagnosis of Endometriosis

National Institute for Health and Care Excellence (NICE). Endometriosis: Diagnosis and Management (NG73). Published 2017; updated November 2024.
NICE — Endometriosis: Diagnosis and Management

World Health Organization. Endometriosis. Updated October 15, 2025.
WHO — Endometriosis

Dason ES, Maxim M, Sanders A, et al. Guideline No. 437: Diagnosis and Management of Adenomyosis. Journal of Obstetrics and Gynaecology Canada. 2023;45(6):417–429.e1.
PubMed — Diagnosis and Management of Adenomyosis

Harmsen MJ, Van den Bosch T, de Leeuw RA, et al. Consensus on revised definitions of Morphological Uterus Sonographic Assessment (MUSA) features of adenomyosis: results of modified Delphi procedure. Ultrasound in Obstetrics & Gynecology. 2022;60(1):118–131.
PubMed — Revised MUSA Consensus

Cunha TM, et al. Adenomyosis at a Glance: An Integrated Review of Transvaginal Ultrasound and MR Imaging Findings. Current Problems in Diagnostic Radiology. 2023.
PubMed — Adenomyosis Imaging Review

National Health Service (NHS). Adenomyosis.
NHS — Adenomyosis

Holdsworth-Carson SJ, et al. Comorbidity of endometriosis and adenomyosis: A systematic review examining the impact of co-morbid disease on fertility and pregnancy outcomes. 2026.
PubMed — Endometriosis and Adenomyosis Comorbidity