Adenomyosis vs. Endometriosis: What’s the Difference?

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By Marta Pietrzak

Adenomyosis and endometriosis are different conditions, but their symptoms can overlap enough that it is easy to confuse the two.

Both can be associated with painful periods and chronic pelvic pain. Both may occur in the same person. And in someone who has already been diagnosed with endometriosis, adenomyosis can sometimes help explain persistent heavy bleeding or uterine pain that remains even after treatment for endometriosis.

The key difference is where the abnormal tissue is located.

Endometriosis involves tissue similar to the lining of the uterus growing outside the uterus. Adenomyosis involves endometrial-type glands and supporting tissue within the muscular wall of the uterus itself.

Understanding that distinction can make symptoms, imaging results, and treatment discussions easier to navigate.

In this article

What Is Adenomyosis?

Adenomyosis is a condition in which endometrial-type glands and stroma are found within the myometrium, the muscular wall of the uterus.

Normally, the endometrium lines the inside of the uterine cavity. In adenomyosis, endometrial-type tissue is present within the muscle surrounding that cavity.

This can be associated with changes in the uterine muscle, including thickening, enlargement, inflammation, increased sensitivity, and altered uterine contractions.

Adenomyosis does not look the same in every person. It can be diffuse, meaning changes are spread more broadly through the uterine muscle, or focal, meaning they are concentrated in a particular area. A localized mass-like form is often called an adenomyoma.

Some people with adenomyosis have significant symptoms, while others have few or no symptoms at all.

Adenomyosis vs. Endometriosis: What’s the Difference?

Adenomyosis and endometriosis are related gynecological conditions, but they are not the same disease.

The simplest distinction is location:

  • Adenomyosis: endometrial-type tissue is located within the muscular wall of the uterus.
  • Endometriosis: endometrial-like tissue is located outside the uterus.

Endometriosis lesions may occur on structures such as the ovaries, pelvic peritoneum, bowel, bladder, or other pelvic tissues.

Adenomyosis remains within the uterus.

This anatomical difference also matters for diagnosis and treatment. A laparoscopy can be used to visualize and treat many forms of endometriosis in the pelvis, but adenomyosis is located within the uterine muscle and is generally evaluated with imaging such as transvaginal ultrasound or MRI.

What Are the Symptoms of Adenomyosis?

Adenomyosis can cause symptoms that overlap substantially with endometriosis and other gynecological conditions.

Commonly reported symptoms include:

  • painful periods;
  • heavy or prolonged menstrual bleeding;
  • chronic pelvic pain;
  • a sensation of pelvic pressure or heaviness;
  • pain during sex; and
  • symptoms related to heavy blood loss, such as fatigue or iron-deficiency anemia.

The uterus may also be enlarged or tender on pelvic examination, although these findings are not present in everyone.

No single symptom confirms adenomyosis. Heavy periods and pelvic pain can have many causes, including fibroids, endometriosis, bleeding disorders, and other gynecological conditions.

Can You Have Adenomyosis and Endometriosis at the Same Time?

Yes. Adenomyosis and endometriosis frequently coexist.

However, the exact percentage varies greatly between studies because researchers use different populations, imaging methods, surgical criteria, and definitions of adenomyosis.

Studies have reported very different rates of adenomyosis among women with endometriosis, so it would be misleading to say that nearly everyone with one condition has the other.

What is clear is that the overlap is clinically important.

A person can have:

  • endometriosis without adenomyosis;
  • adenomyosis without endometriosis; or
  • both conditions at the same time.

Researchers are also studying biological features the two conditions may share, including hormone-responsive signaling, inflammation, tissue remodeling, and altered immune processes. Their exact causes and relationship to one another are still being investigated.

Why Can Pain Persist After Endometriosis Surgery?

If pelvic pain continues after endometriosis surgery, it does not necessarily mean the surgery “failed,” and adenomyosis is only one of several possible explanations.

Endometriosis surgery targets endometriosis lesions that can be identified and surgically treated. It does not automatically treat adenomyosis within the uterine muscle.

Persistent or recurrent pain can also have other causes, including recurrent or residual endometriosis, pelvic-floor dysfunction, adhesions, nerve-related pain, central sensitization, gastrointestinal or urinary conditions, and other sources of chronic pelvic pain.

However, if pain continues alongside symptoms such as increasingly heavy periods, prolonged bleeding, uterine tenderness, or a sense of pelvic pressure, discussing adenomyosis with your healthcare professional may be appropriate.

How Is Adenomyosis Diagnosed?

Historically, adenomyosis was most definitively identified by examining uterine tissue under a microscope after hysterectomy.

Modern imaging has changed that.

Today, clinicians can often make a working diagnosis of adenomyosis without removing the uterus by combining:

  • symptoms and medical history;
  • pelvic examination;
  • transvaginal ultrasound; and
  • magnetic resonance imaging (MRI) when appropriate.

Diagnosis can still be challenging because adenomyosis varies considerably in appearance and can coexist with fibroids or endometriosis.

Experience matters. Imaging performed or interpreted by clinicians familiar with adenomyosis can be particularly useful.

Can Adenomyosis Be Seen on Ultrasound?

Yes. Transvaginal ultrasound is an important first-line imaging tool for evaluating suspected adenomyosis.

Clinicians look for a combination of characteristic changes in the uterine muscle rather than relying on a single ultrasound feature.

Possible findings include:

  • asymmetrical thickening of the uterine walls;
  • small cysts within the myometrium;
  • an irregular or interrupted junction between the endometrium and myometrium;
  • fan-shaped shadowing;
  • echogenic lines or buds extending into the myometrium; and
  • a globular appearance of the uterus.

International groups have developed standardized terminology for describing these ultrasound features, which can help make imaging assessment more consistent.

Not every person with adenomyosis will show every feature.

Can Adenomyosis Be Seen on MRI?

Yes. MRI can be particularly useful when ultrasound findings are unclear, when the condition is difficult to distinguish from fibroids, or when more detailed mapping of the uterus is needed.

One part of MRI assessment is the junctional zone, the inner portion of the uterine muscle next to the endometrium.

Historically, a junctional-zone thickness greater than approximately 12 mm has often been considered suggestive of adenomyosis.

However, this measurement should not be treated as a stand-alone diagnostic test.

Research has shown that junctional-zone thickness can vary with age, hormonal status, the menstrual cycle, medications, and temporary uterine contractions. Some prospective research has also found that irregularity and other direct imaging features may be more diagnostically useful than simply applying a 12 mm cutoff.

Radiologists therefore assess the overall pattern of findings rather than diagnosing adenomyosis based on one measurement alone.

How Is Adenomyosis Treated?

There is no single treatment that is right for everyone with adenomyosis.

Management depends on factors including:

  • the severity of pain and bleeding;
  • your age and overall health;
  • whether adenomyosis is diffuse or focal;
  • whether endometriosis or fibroids are also present;
  • your fertility goals; and
  • your preferences.

Managing pain and heavy bleeding

For some people, treatment begins with medications aimed at controlling symptoms.

Options that may be discussed with a healthcare professional include:

  • nonsteroidal anti-inflammatory drugs (NSAIDs) for pain when medically appropriate;
  • combined hormonal contraceptives;
  • progestin-based treatment;
  • the levonorgestrel-releasing intrauterine system (LNG-IUS); and
  • other hormone-modulating therapies in selected situations.

Hormonal treatments do not all work through exactly the same mechanism, and the best option depends on the individual patient.

Uterus-preserving procedures

For selected patients, particularly those with focal adenomyosis, surgical or minimally invasive uterus-preserving approaches may sometimes be considered.

These procedures require individualized assessment because adenomyosis can be difficult to remove completely when it is diffusely distributed throughout the uterine muscle.

Fertility goals are especially important when discussing these options.

Hysterectomy

Hysterectomy, or surgical removal of the uterus, is the definitive surgical treatment for uterine adenomyosis because the disease is located within the uterus itself.

It is a major and irreversible decision and is generally considered for people with significant symptoms who do not wish to preserve the uterus and for whom other approaches have not provided adequate relief or are not appropriate.

Having adenomyosis does not automatically mean you need a hysterectomy.

When Should You Ask Your Doctor About Adenomyosis?

Consider discussing adenomyosis with your OB-GYN if you experience symptoms such as:

  • very painful periods;
  • increasingly heavy or prolonged periods;
  • pelvic pressure or heaviness;
  • chronic pelvic pain;
  • pain during sex;
  • fatigue associated with heavy menstrual bleeding; or
  • persistent symptoms despite treatment for diagnosed endometriosis.

These symptoms do not prove that you have adenomyosis. They are reasons to ask whether further evaluation may be appropriate.

If you already have endometriosis, it can be especially useful to remember that not every symptom necessarily comes from endometriosis alone. Adenomyosis, fibroids, pelvic-floor dysfunction, and other conditions can coexist and may require different approaches.

Frequently Asked Questions About Adenomyosis

Is adenomyosis the same as endometriosis?

No. In adenomyosis, endometrial-type tissue is located within the muscular wall of the uterus. In endometriosis, endometrial-like tissue is located outside the uterus.

Can you have adenomyosis and endometriosis together?

Yes. The conditions frequently coexist, although reported rates vary widely between studies. Having one does not mean that you necessarily have the other.

Does adenomyosis cause heavy periods?

Heavy or prolonged menstrual bleeding is a common symptom associated with adenomyosis, although not everyone with adenomyosis experiences it.

Can adenomyosis cause severe period pain?

Yes. Painful periods are one of the common symptoms of adenomyosis. Severe period pain can also occur with endometriosis and other gynecological conditions, so symptoms alone cannot determine the cause.

Can ultrasound diagnose adenomyosis?

Transvaginal ultrasound can identify characteristic features associated with adenomyosis and is commonly used as a first-line imaging test. Diagnosis is based on the overall clinical and imaging picture rather than one ultrasound finding alone.

Is MRI better than ultrasound for adenomyosis?

Both can be useful. High-quality transvaginal ultrasound is an important first-line tool, while MRI may provide additional detail when ultrasound is inconclusive, when fibroids complicate the picture, or when more detailed mapping is needed.

Does a 12 mm junctional zone mean I have adenomyosis?

Not necessarily. A junctional-zone thickness above 12 mm has historically been used as one imaging feature associated with adenomyosis, but current evidence indicates that this measurement should not be used alone to make the diagnosis.

Can adenomyosis be cured?

Symptom-focused medical and uterus-preserving treatments can help many people manage adenomyosis. Hysterectomy is considered the definitive surgical treatment because adenomyosis is located within the uterus, but it is not appropriate or necessary for everyone.

References / Sources

Harada T, Khine YM, Kaponis A, et al. (2023). The Asian Society of Endometriosis and Adenomyosis guidelines for managing adenomyosis. Reproductive Medicine and Biology, 22(1), e12535. View full guideline.

Selntigia A, Molinaro P, Tartaglia S, et al. (2024). Adenomyosis: An Update Concerning Diagnosis, Treatment, and Fertility. Journal of Clinical Medicine, 13(17), 5224. View review on PubMed.

Chapron C, Vannuccini S, Santulli P, et al. (2020). Diagnosing adenomyosis: an integrated clinical and imaging approach. Human Reproduction Update, 26(3), 392–411. View review.

Tellum T, Matic GV, Dormagen JB, et al. (2019). Diagnosing adenomyosis with MRI: a prospective study revisiting the junctional zone thickness cutoff of 12 mm as a diagnostic marker. European Radiology, 29(12), 6971–6981. View study on PubMed.

Agostinho L, Cruz R, Osório F, et al. (2017). MRI for adenomyosis: a pictorial review. Insights into Imaging, 8, 549–556. View article on PubMed.

Santulli P, Vannuccini S, Bourdon M, Chapron C, Petraglia F. (2025). Adenomyosis: the missed disease. Reproductive BioMedicine Online, 50(4), 104837. View review.

This article is for educational purposes only and is not intended to diagnose, treat, cure, or prevent any disease. Symptoms such as severe pelvic pain or heavy menstrual bleeding should be discussed with a qualified healthcare professional. Treatment decisions for adenomyosis or endometriosis should be individualized with your healthcare provider.

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