WHAT IS ADENOMYOSIS?
Why heavy, painful periods might not be "just endometriosis" or "just bad periods
By Katie Rice | Accredited Naturopath & Nutritionist | Her Herbs Founder
You've been told your periods are heavy because that's just how you are. Or you've had an endometriosis diagnosis and the treatments have helped some things but not everything. The cramping is still severe. The bleeding is still significant. There's a constant sense of pressure or fullness low in your abdomen that doesn't fully go away between periods.
If this sounds familiar, there's a condition that deserves to be part of the conversation, and it's one that's frequently missed, misattributed to endometriosis, or dismissed as simply bad periods.
It's called adenomyosis. And it is not the same thing as endometriosis.
What Adenomyosis Actually Is
Adenomyosis is a condition where endometrial-like tissue, the tissue that normally lines the inside of the uterus, grows into the muscular wall of the uterus itself, the myometrium. Each cycle, that misplaced tissue bleeds inside the muscle. Over time this damages blood vessels, creates small blood pockets within the uterine wall, and causes the uterus to thicken, enlarge, and become tender.
The result is a uterus that bleeds more heavily, contracts more painfully, and often feels bulky or pressured in a way that's hard to describe but immediately recognisable to women who experience it.
This is not endometriosis. It is a separate condition with a different location, a different mechanism, and in many cases a different treatment pathway. The two conditions can and frequently do coexist, which is part of why adenomyosis gets missed. When both are present, everything is more severe and more complex, and it's easy to attribute all of it to the diagnosis you already have.
How It Differs From Endometriosis
Both conditions involve endometrial-like tissue growing where it shouldn't. That's where the similarity ends.
In endometriosis, that tissue grows outside the uterus entirely, on the ovaries, fallopian tubes, bowel, bladder, peritoneum, and other pelvic structures. In adenomyosis, it grows inward, into the uterine muscle wall itself.
That difference in location drives a difference in symptoms. Endometriosis more commonly causes bowel and bladder pain, pain with urination or bowel movements, nausea, and diarrhoea around periods, reflecting where the lesions are sitting. Adenomyosis more commonly causes very heavy bleeding, a sense of uterine bulk and pressure, and deep, persistent cramping that can be present between periods as well as during them.
Both cause painful periods and pelvic pain. Both can cause pain with sex. But the heaviness, the bloating low in the abdomen, the feeling that the uterus itself is enlarged and uncomfortable, these point more specifically toward adenomyosis.
How It Differs From Fibroids
This is the other common confusion, and it matters because fibroids and adenomyosis can look similar from the outside but are different conditions requiring different management.
Fibroids are benign tumours of the uterine muscle, not endometrial tissue. They form as discrete, well-defined lumps or nodules in or on the uterus. They can cause heavy bleeding and pressure, particularly if they're large or positioned inside the uterine cavity.
Adenomyosis is more diffuse. Rather than distinct lumps, it causes a generalised thickening of the uterine wall. On examination or imaging, the uterus is often described as globally enlarged and boggy rather than lumpy or irregular. That distinction is what imaging is specifically looking for.
It's also worth knowing that fibroids, adenomyosis, and endometriosis can all be present simultaneously, which is not uncommon and significantly complicates both the symptom picture and the diagnostic process.
Why Heavy, Painful Periods May Be Adenomyosis
The classic adenomyosis presentation includes several features that are worth knowing.
Very heavy or prolonged periods, often with clots, and frequently leading to anaemia and fatigue. Heavy bleeding occurs in around 40 to 60 percent of women with adenomyosis, driven by increased endometrial surface area, greater tissue buildup, and higher blood flow to the affected uterine wall.
Severe cramping that is deep, persistent during the period, and sometimes present between cycles. This is linked to stronger uterine contractions and elevated prostaglandin activity within the affected muscle.
A sense of uterine bulk, pressure, or fullness low in the abdomen, sometimes called adenomyosis belly. This is a constant or near-constant feeling of heaviness that doesn't fully resolve between periods, which distinguishes it from the more cyclically concentrated pain of endometriosis.
Painful sex and in some cases reduced fertility, particularly when adenomyosis is severe or coexists with endometriosis.
If you've been managing heavy, painful periods for years and been told it's normal, or attributed everything to endometriosis without the adenomyosis question being specifically raised, this pattern is worth bringing to your next appointment directly.
How Adenomyosis Is Diagnosed
This is one of the most important pieces of information for women navigating this condition, because historically adenomyosis was only confirmed after hysterectomy. That is no longer the case.
Adenomyosis can now be diagnosed non-invasively in most cases, and imaging is the key tool.
Transvaginal ultrasound is usually the first investigation for women presenting with heavy or painful periods. An experienced sonographer looking specifically for adenomyosis will assess the myometrium for heterogeneous texture, myometrial cysts, and junctional zone thickening. Sensitivity is around 72 percent and specificity around 81 percent, meaning it's a good starting point but not perfect.
Pelvic MRI has higher accuracy, with sensitivity around 77 percent and specificity around 89 percent. It's particularly useful when ultrasound is unclear, when detailed mapping is needed before treatment decisions, or when the symptom picture is complex.
The critical point is that adenomyosis needs to be specifically looked for. A standard ultrasound for pelvic pain or irregular bleeding may not include the specific assessment required. If you have heavy bleeding, severe cramping, a sense of uterine bulk, and those symptoms haven't fully responded to treatment for endometriosis or fibroids, asking specifically for adenomyosis to be assessed on imaging is a reasonable and important next step.
What to Say at Your Appointment
Bring your symptom history with as much specificity as possible. How heavy is the bleeding, how many days does it last, are there clots, has it been getting worse over time. Where exactly is the pain, is it deep and persistent or sharper and cyclical. Is there a sense of pressure or fullness between periods.
Ask directly: "Could this be adenomyosis? Has that been specifically assessed on imaging?"
If you've had an endometriosis diagnosis and symptoms haven't fully resolved with treatment, asking whether adenomyosis might also be contributing is not an overcomplicated question. It's a clinically relevant one.
If you want to go deeper on adenomyosis, including treatment options, pain management, and fertility implications, the Her Herbs Adenomyosis Series covers the full picture.
EXPLORE THE HER HERBS ADENOMYOSIS SERIES
A Note From Katie
"Adenomyosis was one of the most under-diagnosed conditions I encountered in clinic, and the women who had it had almost always been told for years that their periods were just heavy, or that their endometriosis explained everything. It doesn't always. Adenomyosis is a real, separate condition that deserves its own investigation and its own treatment plan. If your symptoms include that deep, persistent sense of uterine heaviness and pressure alongside very heavy bleeding, please push for adenomyosis to be specifically ruled in or out. You deserve a complete picture."
-Katie Rice, Naturopath & Founder, Her Herbs
This content is for educational purposes only and does not constitute medical advice. Please consult your healthcare provider regarding your individual health concerns.
