Adenomyosis: Symptoms, Causes & Treatment

Written by Dr. Simon Khela MBChB MRCGP, GMC Registered Doctor

Last reviewed: 03-08-2026

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A patient in her mid-thirties came to see me convinced she’d simply gained weight around her middle despite no real change in diet or activity. She hadn’t had children and didn’t fit the picture she’d read about online, "a condition for women in their forties who’ve already had babies." An ultrasound told a different story. Her uterus was significantly enlarged, and further investigation confirmed adenomyosis. The bloating she’d noticed wasn’t weight gain at all.

Adenomyosis is far more common than most people realise, and increasingly recognised in younger women without children, which is a shift from how it was traditionally understood. Getting to grips with what it actually is, what causes it, and what genuinely helps matters, particularly because heavy, painful periods are so often dismissed as simply "bad luck" rather than investigated properly.

This article covers:

• What adenomyosis is and what's currently understood about its causes
• The symptoms to recognise, including the bloating some patients call "adenomyosis belly"
• How it’s diagnosed, and how it differs from the similarly named endometriosis and from fibroids
• The treatment options available, from medical management to surgery

Quick Answer: What Is Adenomyosis?

Adenomyosis is a condition where tissue similar to the lining of the womb grows into the muscular wall of the uterus itself, rather than staying confined to the inner lining where it belongs. This causes the uterus to become enlarged, thickened, and often tender, and can lead to heavy, painful periods and chronic pelvic discomfort.

• Common symptoms include heavy menstrual bleeding, worsening period pain, pelvic pain outside your period, and abdominal bloating from an enlarged uterus
• The exact cause isn't fully understood, though several theories exist, and previous uterine surgery or childbirth appear to increase risk
• It's increasingly diagnosed in younger women, not just those in their late thirties and forties who've had children, as was traditionally assumed
• There's no single cure short of hysterectomy, but a range of treatments can meaningfully reduce symptoms for those wanting to avoid or delay surgery

What Causes Adenomyosis?

Many patients are surprised to learn that, much like endometriosis, medical science doesn't have one settled answer for why adenomyosis develops. A few theories currently carry the most weight.

Direct Invasion Theory

The most widely accepted explanation. It suggests that the innermost layer of the womb lining gradually pushes into the underlying muscle layer, where it continues to behave as though it were still lining tissue, thickening and breaking down with each cycle.

Tissue Injury and Repair

Trauma to the uterus, such as from a caesarean section, dilation and curettage, or fibroid surgery, triggers an abnormal healing response that allows lining tissue to embed itself into the muscle wall.

Developmental Theory

A less common explanation suggesting that misplaced embryonic tissue may later develop adenomyosis-like changes.

Known Risk Factors

• Previous uterine surgery, including caesarean section, dilation and curettage, or fibroid removal
• Having given birth, particularly multiple times
• Starting periods at a young age
• Short menstrual cycles
• Increasing age, though it's now recognised in younger, childless women more often than previously thought
• Obesity
• Long-term tamoxifen use, a medication used in some breast cancer treatment

Adenomyosis Symptoms

A question I’m frequently asked is what actually separates adenomyosis from "just" heavy or painful periods. In practice, it’s the pattern, the trend over time, and the presence of additional symptoms beyond bleeding alone.

Period-Related Symptoms

• Heavy menstrual bleeding, sometimes with clots
• Prolonged periods
• Period pain that’s often described as progressively worsening year on year, rather than staying consistent

Symptoms at Any Time in the Cycle

• Chronic pelvic pain or a persistent dull ache
• Pain during or after sex
• A feeling of pressure on the bladder or bowel from an enlarged uterus
• Some people have no symptoms at all, with adenomyosis found incidentally during scanning for another reason

"Adenomyosis Belly": Understanding the Bloating

One of the more common concerns I see in practice is bloating or lower abdominal distension that patients assume is weight gain or bowel-related, when it’s actually the physical enlargement of the uterus itself. This is sometimes informally referred to as "adenomyosis belly."

• It happens because the uterus can grow significantly larger than normal, sometimes to a size more typically associated with early pregnancy
• It's often worse premenstrually, alongside other cyclical symptoms
• Unlike general bloating from diet or digestion, it tends to be a more constant, structural change rather than something that fluctuates day to day with food or fluid intake

Adenomyosis vs Fibroids

This is a genuinely common source of confusion, since both conditions can cause an enlarged uterus, heavy periods, and pelvic pressure, and the two can coexist in the same person.

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Distinguishing between the two matters clinically, since it can influence which treatments, particularly surgical options, are most appropriate.

How Is Adenomyosis Diagnosed?

Adenomyosis was historically only confirmed after hysterectomy, when the removed uterus could be examined under a microscope. Modern imaging has changed this considerably.

• A pelvic examination may reveal an enlarged, tender uterus with a characteristic "boggy" texture, though this alone isn't diagnostic
• Transvaginal ultrasound is usually the first-line imaging test and can show a thickened, irregular-looking muscle wall
• MRI scanning gives a more detailed picture and is particularly useful for distinguishing adenomyosis from fibroids, or for surgical planning
• Histological confirmation after hysterectomy remains the definitive diagnosis, though it's no longer necessary for most people to reach a confident clinical diagnosis and start treatment

If symptoms are significant or imaging findings are unclear, a referral to a specialist, usually a gynaecologist, allows for more detailed assessment and discussion of the full range of treatment options.

Adenomyosis Treatment

There's no treatment that reliably eliminates adenomyosis without removing the uterus entirely, but several options can meaningfully reduce symptoms for those who want to avoid or delay that step.

Medical Management

NSAIDs

Such as ibuprofen, for pain relief during periods.

Tranexamic Acid

Can reduce the volume of heavy bleeding.

Hormonal Intrauterine System (IUS)

Often particularly effective for adenomyosis specifically, since it delivers hormone directly to the womb lining.

Other Hormonal Options

Including the combined contraceptive pill, other progestogen-based treatments, or GnRH analogues for more severe cases. Medication of this kind is often arranged through a private prescription once the right option has been discussed.

Minimally Invasive Options

• Uterine artery embolisation, a procedure performed by an interventional radiologist to reduce blood flow to affected areas of the uterus
• Focused ultrasound treatment, a newer, non-surgical option available in some specialist centres, using targeted ultrasound energy to treat affected tissue

Surgical Options

• Adenomyomectomy, a fertility-sparing procedure to remove a localised area of adenomyosis (an adenomyoma), though this is technically more challenging than similar fibroid surgery and isn't suitable for the more diffuse form of the condition
• Hysterectomy, which is the only definitively curative option, since it removes the affected organ entirely, reserved for those who've completed their family or where other treatments haven't controlled symptoms adequately

Fertility Considerations

Adenomyosis is associated with somewhat lower success rates in fertility treatment and a higher risk of miscarriage in some studies, though outcomes vary considerably between individuals. Anyone trying to conceive with a known or suspected diagnosis should raise this early with their GP or an infertility clinic, since treatment decisions can differ significantly depending on whether pregnancy is being planned.

Common Myths and Misconceptions

Myth: Adenomyosis only affects older women who've already had children.

This was the traditional view, but it's increasingly recognised in younger women, including those who haven't given birth, particularly as imaging has improved detection.

Myth: Heavy periods are just something to live with.

Bleeding heavy enough to affect daily life, cause anaemia, or require frequent changes of protection is worth investigating, not something to simply endure indefinitely.

Myth: You can only diagnose adenomyosis by removing the uterus.

This used to be true, but modern MRI and ultrasound imaging now allow a confident diagnosis in most cases without surgery.

Myth: Adenomyosis and fibroids are the same condition.

They're different conditions with different underlying processes, though they share some symptoms and can occur in the same person at the same time.

Myth: There's nothing you can do except have a hysterectomy.

Several medical and minimally invasive treatments can meaningfully reduce symptoms before hysterectomy needs to be considered, and many people manage well without ever needing surgery.

Benefits and Limitations of Treatment Options

Medical treatments, particularly the hormonal IUS, are genuinely effective for many people, reversible, and avoid the risks of surgery, but they don't remove the underlying tissue and symptoms can return if treatment stops. Minimally invasive procedures such as uterine artery embolisation can reduce symptoms without major surgery, but aren't suitable for everyone and long-term outcomes data is still developing compared with more established treatments.

Hysterectomy is the only option that definitively resolves adenomyosis, since it removes the affected organ, but it's a major, irreversible procedure that ends fertility, which is why it's generally considered only once other options have been tried or aren't appropriate for the individual's circumstances.

When to See a GP

• If your periods have become noticeably heavier or more painful than they used to be
• If you notice abdominal bloating or distension that doesn't fit with your usual pattern
• If you have pelvic pain outside your period that isn't explained by anything else
• If heavy bleeding is affecting your daily life, work, or leaving you feeling constantly tired
• If you're trying to conceive and have ongoing concerns about heavy or painful periods

An online GP consultation or a private GP appointment is a sensible starting point to discuss your symptoms, and a private blood test can check for anaemia if bleeding has been heavy, alongside a broader general health check if you haven't had one recently. For women approaching perimenopause with overlapping symptoms, it's also worth raising this alongside a menopause clinic review, since adenomyosis symptoms often ease naturally after menopause.

Frequently Asked Questions