Adenomyosis vs Fibroids: How to Tell Them Apart

Quick Answer

Fibroids are separate benign muscle growths, while adenomyosis is lining-like tissue growing into the muscle wall of the uterus. Both cause heavy, painful periods, so symptoms alone cannot tell them apart; ultrasound is the usual first test and MRI gives the clearest picture, and many women have both.

Adenomyosis and fibroids can cause the same symptoms, heavy periods, painful cramps and pelvic pain, but they are different conditions. Fibroids are separate, ball-like growths of muscle tissue. Adenomyosis is tissue similar to the uterine lining growing into the muscle wall of the uterus. Symptoms alone cannot tell them apart. An ultrasound is usually the first test, and MRI gives the clearest answer when the picture is unclear. Many women have both.

What each condition is

Fibroids

Fibroids (leiomyomas) are noncancerous tumors that grow from the smooth muscle of the uterus. Each one is a distinct lump with its own edge, and they can grow inside the cavity, within the wall, or on the outer surface of the uterus. They are very common: ACOG estimates they occur in up to 70% of women by menopause. Learn more in our guide to the symptoms of fibroids.

Adenomyosis

In adenomyosis, tissue like the endometrium, the lining of the uterus, is found inside the muscle wall. A 2016 clinical review by Struble and colleagues explains that the leading theory is that the lining grows into the muscle, changing the boundary between the two layers, which is called the junctional zone. Instead of forming a neat lump, adenomyosis usually spreads through the wall and makes the uterus bulky. Sometimes it forms a more focal patch called an adenomyoma, which can look like a fibroid.

How the symptoms compare

Both conditions can cause heavy menstrual bleeding, painful periods and chronic pelvic pain, and both can affect fertility. A 2026 review by Pecorella and colleagues notes some general differences, while stressing that the overlap is large:

	Fibroids	Adenomyosis
What it is	Separate benign muscle tumors	Lining-like tissue growing into the muscle wall
Most typical symptoms	Heavy bleeding; bulk symptoms such as pressure, frequent urination and constipation	Heavy bleeding and painful periods
Uterus on imaging	Well-defined, round masses with a clear edge	Diffuse, poorly defined thickening of the wall
Can occur with the other?	Yes, often	Yes, often

A 2005 radiology review put it plainly: the common symptoms of adenomyosis "do not allow diagnosis." Some women with either condition have no symptoms at all.

How ultrasound and MRI tell them apart

Imaging is how doctors make the distinction. Expert groups recommend starting with ultrasound and using MRI for complex cases or treatment planning.

Ultrasound

A transvaginal ultrasound is usually the first test. Fibroids tend to show up as distinct, round masses, often with blood vessels around their edges. An international expert consensus (the revised MUSA definitions, 2022) lists signs that point directly to adenomyosis, including small cysts in the muscle wall, bright islands of tissue, and fine lines or buds extending from the lining into the muscle. Ultrasound can be harder to read when the uterus is large or has many fibroids.

MRI

MRI shows the layers of the uterus in detail. Radiology reviews describe it as highly accurate for diagnosing adenomyosis and separating it from other conditions. On MRI, a fibroid usually has a sharp border, sometimes with a thin capsule around it. Adenomyosis has a blurred, infiltrating edge and often thickens the junctional zone. A junctional zone of 12 mm or more has traditionally been considered suggestive of adenomyosis, although experts caution it should not be used as the only sign.

In a 2023 study of 50 women who later had a hysterectomy, so the diagnosis could be confirmed under the microscope, MRI correctly identified adenomyosis more often than ultrasound with Doppler (sensitivity about 92% vs 78%, specificity about 86% vs 79%). Even so, reviews note that a clear-cut answer is not always possible, especially with focal adenomyosis that looks like a fibroid. Our article on ultrasound vs MRI for fibroids explains each test in more detail.

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This article is part of our Fibroid Treatment Guide.

Having both conditions

Adenomyosis and fibroids frequently occur together, and adenomyosis is also linked with endometriosis. This matters because a treatment aimed at fibroids may leave adenomyosis symptoms behind, or the other way around. If your imaging report mentions both, ask your doctor which one is more likely driving your symptoms.

Why the difference matters for treatment

Options for fibroids include medication, a hormonal IUD, uterine fibroid embolization, myomectomy to remove the fibroids, and hysterectomy. Because fibroids are separate lumps, they can often be removed or treated individually.

Adenomyosis is harder to remove because it is woven through the muscle wall. The 2016 Struble review noted that hysterectomy is the only definitive treatment. Medical treatments aim to control bleeding and pain.

Uterine artery embolization has also been studied for adenomyosis. In the 2025 QUESTA study of 101 women, quality of life improved after both embolization and hysterectomy at 1 year, but hysterectomy gave greater pain relief and higher satisfaction (95% vs 73%), and the study could not show that embolization was as good as hysterectomy. A 2026 review calls embolization's effectiveness for adenomyosis "still debatable", with better results in localized disease. You can read about this research in embolization for adenomyosis. Whether it is a reasonable option for you is a question for the specialist reviewing your imaging.

For fibroids, the evidence is broader. Uterine fibroid embolization (UFE) has been compared with surgery in several randomized trials. Before UFE, European interventional radiology standards (CIRSE 2015) name contrast-enhanced MRI as the preferred imaging test, partly because it shows whether adenomyosis is also present. See every fibroid option in our fibroid treatment guide.

Questions to ask about your imaging report

Imaging reports can be hard to read. These questions can help you understand yours:

Does the report describe fibroids, adenomyosis, or both?
If fibroids, how many, how large, and where are they (inside the cavity, in the wall, or on the outside)?
If adenomyosis, is it spread through the wall or in one area?
Which condition is most likely causing my main symptom?
Was the ultrasound clear, or would an MRI add useful information?
Which treatments fit what the images show, and which would not?

Writing down your symptoms before the visit, including how many days you bleed, how often you change protection, and when pain is worst, helps your doctor connect the images to your experience.

When to see a doctor

Make an appointment if your periods are heavy enough to disrupt daily life, cramps are getting worse over time, you have pelvic pressure or pain between periods, or you feel tired and short of breath from possible anemia. Seek urgent care for bleeding with faintness or a racing heartbeat, or sudden severe pelvic pain. Bring any previous ultrasound or MRI reports to your visit, since comparing images over time helps.

Frequently Asked Questions

Can you have adenomyosis and fibroids at the same time?

Yes. The two conditions frequently occur together, which can make diagnosis and treatment planning more complex. Imaging, especially MRI, helps show how much of each is present.

Which is more painful, adenomyosis or fibroids?

Painful periods are a hallmark of adenomyosis, while fibroids more often cause heavy bleeding and pressure symptoms. Both can cause pain, and individual experiences vary widely.

Can an ultrasound miss adenomyosis?

Yes. Ultrasound is the usual first test, but it can be harder to read when the uterus is large or has many fibroids. MRI is often used when the ultrasound is unclear.

Is adenomyosis cancer?

No. Adenomyosis is a benign condition, as are fibroids. Both can cause significant symptoms that deserve treatment.

Does uterine fibroid embolization treat adenomyosis?

Embolization has been studied for adenomyosis, with symptom improvement in many patients, but in the 2025 QUESTA study it did not match hysterectomy for pain relief or satisfaction. Ask a specialist whether it suits your situation.

Keep Reading

Sources

Medically reviewed by David Fox, MD, FACS, RPVI. This article is general information, not a substitute for a medical evaluation.

Living with heavy periods, pelvic pressure or other fibroid symptoms? Schedule a consultation with Dr. David Fox at Fox Vein & Vascular in Manhattan to find out whether uterine fibroid embolization is right for you. Call (212) 362-3470 or request a UFE consultation online.

Adenomyosis vs Fibroids: Symptoms, Imaging and Why the Difference Matters