What Does Adenomyosis Look Like? Signs, Scans & More

Adenomyosis shows up differently depending on whether you are looking at symptoms or scans. In your body, it typically announces itself through painful, heavy periods and a dull ache in the pelvis. On an ultrasound screen, it appears as a swollen, asymmetric uterus studded with tiny cysts and shadowy streaks in the muscle wall. On MRI, the hallmark is a thickened band of tissue called the junctional zone, often exceeding 12 mm. The condition is essentially endometrial tissue growing where it should not be, burrowed into the muscular wall of the uterus, and the way that misplaced tissue distorts normal anatomy is what doctors look for when making a diagnosis.

How the Condition Develops

The uterus has an inner lining (the endometrium) and a thick muscular layer (the myometrium). In adenomyosis, glands and supporting tissue from that inner lining push down into the muscle. For a long time the only way to confirm adenomyosis was to examine the uterus under a microscope after a hysterectomy, looking for endometrial glands and stroma at least 2.5 mm below the boundary between the lining and the muscle wall, surrounded by thickened, overgrown muscle tissue.¹ The leading theory for how this happens involves tissue injury and repair: repeated cycles of damage to the base of the endometrium, possibly from menstruation itself or from procedures like cesarean sections, allow endometrial cells to invade downward into the muscle.² That matters because it helps explain why the disease tends to worsen over time and why it often appears in people who have had uterine surgery or multiple pregnancies.

What the Symptoms Look Like Day to Day

The most common symptom is painful periods, often the kind that get progressively worse year after year rather than staying steady. In one study of nearly 300 women with confirmed adenomyosis, about 68% reported menstrual pain, and more than half of those said the pain had been getting worse over time. Roughly a third of the pain cases were rated severe.³ Heavy menstrual bleeding is the other signature complaint, and the two together can be debilitating. But the pain is not always limited to your period. About a quarter of patients in that same study had chronic pelvic pain that lingered between cycles, and a smaller number experienced pain during sex or rectal discomfort.³

One confusing thing about adenomyosis symptoms is that they overlap heavily with fibroids, endometriosis, and even some gastrointestinal conditions. Heavy bleeding and pelvic pain are not specific to any one diagnosis, which is part of the reason adenomyosis has historically gone unrecognized for years before being identified. Some people with the condition have no symptoms at all, with the finding discovered incidentally during imaging for something else. Canadian clinical guidelines list the core symptom triad as heavy menstrual bleeding, pain, and infertility.⁴

What Adenomyosis Looks Like on Ultrasound

Transvaginal ultrasound is usually the first imaging tool used, and a trained sonographer can spot several telltale features. An international consensus group called MUSA (Morphological Uterus Sonographic Assessment) has cataloged the specific signs to look for. These include a uterus that appears enlarged and globular, with one wall noticeably thicker than the other, small cysts scattered within the muscle, bright echogenic islands, fine streaks radiating outward from the lining into the muscle called subendometrial lines and buds, and a characteristic fan-shaped shadowing pattern.¹

The MUSA group draws an important distinction between “direct” and “indirect” features. Direct features are signs that the misplaced endometrial tissue is actually visible in the muscle wall: the myometrial cysts, the hyperechogenic islands, and the subendometrial lines and buds. Indirect features reflect changes in the surrounding muscle caused by the presence of that tissue, like the asymmetric wall thickening or the fan-shaped shadows.⁵ When a sonographer spots direct features, confidence in the diagnosis goes up significantly compared to seeing indirect signs alone.

Three-dimensional ultrasound adds another layer. It can visualize the junctional zone, which is the boundary between the endometrium and the myometrium, and in women with adenomyosis-related abnormal bleeding this zone tends to look irregular, poorly defined, and interrupted on 3D imaging.⁶ That disrupted border is essentially where the endometrial tissue has broken through into the muscle, and seeing it directly on 3D ultrasound helps pin down the diagnosis.

What Adenomyosis Looks Like on MRI

MRI provides the clearest picture of the junctional zone, and the single most important finding for diagnosing adenomyosis on MRI is a junctional zone thicker than 12 mm.⁷ On T2-weighted MRI sequences (the kind that make fluid appear bright and muscle appear dark), the junctional zone normally shows up as a thin, dark band at the inner edge of the muscle wall. In adenomyosis, that band is dramatically thickened and may be studded with bright foci, which are the tiny pockets of endometrial tissue and sometimes small hemorrhages trapped within the muscle.⁸

There is a subtlety worth knowing. While the classic MRI threshold is 12 mm, more recent research suggests that the real hallmark of adenomyosis on imaging is not just thickening but interruption of the junctional zone by endometrial tissue. On ultrasound this shows up as subendometrial lines and buds; on MRI it appears as bright foci within the dark zone. Those bright foci on both T1- and T2-weighted images are considered characteristic of the disease. The junctional zone also measures thicker on MRI than on ultrasound for the same patient, because the two modalities reflect the anatomy differently, with MRI showing a sharp boundary while the histological changes underneath are actually gradual.⁹

Diffuse vs. Focal Forms

Adenomyosis does not always look the same from person to person because it comes in two broad forms. Diffuse adenomyosis involves widespread invasion of endometrial tissue throughout the muscle wall. On MRI, this shows up as a generalized thickening of the junctional zone, typically with a dark, relatively uniform appearance on T2-weighted images. In one imaging study, the junctional zone in diffuse cases ranged from 7 to 37 mm, averaging about 16 mm.¹⁰

Focal adenomyosis, on the other hand, creates a discrete mass. On imaging it looks like a round or oval low-signal-intensity area, averaging around 4 cm in diameter, with blurry edges and bright spots scattered within it. Nearly all focal lesions in one study had poorly defined margins, which helps distinguish them from fibroids, which tend to have sharp, well-defined borders.¹⁰ The focal form can be trickier to identify because it can mimic a fibroid on a quick scan, which is why the imaging details matter so much.

How Doctors Tell It Apart from Fibroids

This is one of the most common diagnostic puzzles in gynecological imaging, and it matters because the treatments are different. Both fibroids and adenomyosis can enlarge the uterus, cause heavy bleeding, and create masses in the muscle wall. On MRI, the key distinction is that adenomyosis appears as an ill-defined, relatively uniform dark area on T2-weighted images with scattered bright spots inside, while fibroids are well-circumscribed masses with a wider range of signal patterns.¹¹ In plain terms, a fibroid looks like a well-defined ball with a clear edge, while adenomyosis looks like a vague, smudgy region that blends into the surrounding muscle.

On ultrasound, fibroids often cast a sharp shadow and may show a ring of blood vessels around their perimeter. Adenomyosis tends to produce fan-shaped shadowing without a clear mass boundary, and the blood vessels run through the lesion rather than around it. Despite these differences, the two conditions coexist frequently, which can make sorting them out on a single scan genuinely difficult.

Is Ultrasound or MRI Better for Diagnosis?

Clinicians often ask whether it is worth ordering an MRI if an ultrasound has already been done. The research is fairly clear: for diagnosing adenomyosis, the two methods perform comparably. A head-to-head meta-analysis found that transvaginal ultrasound had a pooled sensitivity of about 75% and specificity of about 81%, while MRI had a sensitivity of about 69% and specificity of about 80%, with no statistically significant difference between them.¹² A separate meta-analysis reached the same conclusion, finding ultrasound performance to be high and comparable to MRI.¹³

That said, there is a catch. Ultrasound accuracy depends heavily on the experience of the person performing the scan. Considerable training is needed to recognize the distinct ultrasound pattern, whereas MRI findings are somewhat less dependent on the individual operator.¹⁴ In practice, MRI tends to get ordered when ultrasound is inconclusive, when distinguishing adenomyosis from fibroids is critical for surgical planning, or when mapping the extent of disease before a fertility-preserving procedure.

The Overlap with Endometriosis

Adenomyosis and endometriosis are related conditions, and they often appear together. Endometriosis involves endometrial-like tissue growing outside the uterus entirely, on the ovaries, pelvic lining, or bowel, while adenomyosis is the invasion of that tissue into the muscle wall of the uterus itself. When deep infiltrating endometriosis is present, adenomyosis frequently is too. In one study of 255 patients with deep infiltrating endometriosis, more than half had focal adenomyosis of the outer muscle wall, and those patients had a significantly higher number of deep endometriosis lesions and greater disease severity overall.¹⁵

Researchers have also found evidence that adenomyosis driven from the outside in (“extrinsic” adenomyosis, often associated with deep endometriosis) may be biologically different from adenomyosis that grows from the inner lining downward (“intrinsic” adenomyosis). In one study, 90% of women with extrinsic adenomyosis had coexisting deep infiltrating endometriosis, compared to just 13% of those with the intrinsic form.¹⁶ This distinction is still being studied, but it suggests that what we call “adenomyosis” may actually encompass at least two different disease processes that converge on the same organ.

How Adenomyosis Affects Fertility and Pregnancy

One of the more consequential aspects of adenomyosis is its impact on getting pregnant and staying pregnant. A recent study found that women with adenomyosis had roughly three and a half times the odds of infertility and were nearly three times more likely to conceive through assisted reproductive technology compared to controls.¹⁷ Part of the reason may be that adenomyosis disrupts normal uterine contractions. A meta-analysis found that women with the condition had significantly reduced contraction frequency and fewer forward-directed contractions, the type that help transport sperm and support embryo implantation.¹⁸

Even when pregnancy is achieved, the risks do not end. Adenomyosis has been linked to a range of obstetric complications including preterm birth, premature rupture of membranes, placental problems, fetal growth restriction, and preeclampsia.¹⁹ The same study that found higher infertility rates also reported that women with adenomyosis had about double the risk of preterm birth and roughly triple the risk of placenta previa, along with significantly higher rates of excessive postpartum hemorrhage.¹⁷ If you are planning a pregnancy and have been diagnosed with adenomyosis, these risks are worth discussing with your care team early on.

It Is Not Just a Condition of Older Women

There is a persistent assumption that adenomyosis mostly affects women in their late 30s and 40s. While prevalence does increase with age, the condition is far from absent in younger people. A systematic review looking specifically at adolescents and young women with gynecological symptoms found adenomyosis in about 17% of adolescents and about 30% of young women on imaging, with a clear trend of increasing prevalence as age went up.²⁰ These are symptomatic populations, so the numbers are higher than they would be in the general population, but they demolish the idea that adenomyosis should not be on the radar for younger patients.

The practical consequence is diagnostic delay. If a clinician assumes that a 22-year-old with worsening period pain and heavy bleeding is too young for adenomyosis, the condition will not be looked for on imaging, and years of unnecessary suffering may follow. Awareness that the disease does occur in younger age groups is slowly growing, but it has not fully filtered into routine practice.

Treatment Options After Diagnosis

Treatment is tailored to the symptoms that matter most to you and whether future pregnancy is a goal. The options span a wide range:

Medication: Anti-inflammatory drugs and tranexamic acid for pain and bleeding, hormonal options including combined oral contraceptives, the levonorgestrel intrauterine system, dienogest, other progestins, and GnRH analogues to suppress the disease hormonally.
Uterine artery embolization: A minimally invasive procedure that cuts off blood supply to the affected tissue. Long-term symptom improvement has been reported in about 74% of cases with isolated adenomyosis, and over 80% of patients in longer follow-up studies sustained improvement in quality of life and avoided hysterectomy.²¹
Surgery: Endometrial ablation, surgical excision of focal adenomyosis, or hysterectomy as a definitive option when other treatments fail or when fertility is no longer desired.

Canadian clinical guidelines frame the outcomes of interest as reduction in heavy menstrual bleeding, reduction in pain (menstrual pain, pain during sex, chronic pelvic pain), and improvement in reproductive outcomes.⁴ The choice among treatments depends on severity, subtype (diffuse versus focal, since focal disease may be more amenable to surgical excision), and personal priorities.

Can a Blood Test Diagnose Adenomyosis?

Not yet, but research is actively trying to get there. One of the frustrations with adenomyosis is that there is no simple lab test to flag it. A 2025 study investigated whether specific small molecules called microRNAs circulating in the blood could serve as biomarkers. The researchers identified a two-microRNA panel that performed well in distinguishing women with adenomyosis from healthy controls, with a combined diagnostic accuracy score of 0.941 on the standard measure.²² That is a promising result, but this is still early-stage research and nowhere near clinical use. No validated blood-based screening test exists today.

Artificial Intelligence and the Future of Scanning

Several research groups are training AI systems to recognize adenomyosis on ultrasound images. The appeal is obvious: if a computer could flag the condition reliably, it would reduce the diagnostic gap caused by variation in sonographer experience. Early results have been mixed. One deep learning model tested against intermediate-skill ultrasound trainees achieved lower accuracy than the trainees themselves, with an overall accuracy of about 51% compared to the trainees’ 70%.²³ More recent work using transformer-based neural networks has pursued higher accuracy and automatic identification of the disease from ultrasound images.²⁴ Another team presented results at a 2025 conference showing that an automated deep learning model could diagnose and classify the severity of adenomyosis from ultrasound scans.²⁵ The technology is not ready to replace a skilled examiner, but it represents a direction the field is clearly moving toward, especially for settings where expert sonographers are scarce.