If I have endometriosis, am I likely to get adenomyosis?

Endometriosis is a condition where endometrial tissue — the lining layer of the uterus (womb) that sheds each month as your period — is found growing outside of the uterus. The lining layer of the uterus can leave the body – as blood, during a period – out of the vagina. However, when the same tissue grows in other parts of the body (for example, around the ovaries, near the rectum, or anywhere else in the body) and bleeds, the blood cannot leave the body and instead causes a chronic inflammatory reaction.

Between 2 and 10% of people with vulvas have endometriosis, but the prevalence of endometriosis is higher in those who have difficulty getting pregnant – up to 50% of women with infertility are thought to have the condition.¹

Not everyone who has endometriosis will experience symptoms, but those who do can experience pain during menstruation, pain during sexual intercourse, pain on passing faeces or urine, and pelvic pain, depending on where exactly the uterus tissue is growing.

People with endometriosis may also have difficulty getting pregnant, may develop endometriotic cysts (collections of tissue from the bleeding, sometimes called “chocolate” cysts), and may have associated bowel symptoms.² For the majority of those with endometriosis the pain will be cyclical, peaking during menstruation, and stopping once menstruation has finished. It tends to occur in people of reproductive age, starting in the teenage years.

Why do people get endometriosis?

Scientists have not yet discovered why some people develop endometriosis. The most prevalent theory is that it begins as a result of retrograde menstruation, when blood that should flow out of the vagina during your period instead flows back the other way, possibly as a result of a uterus that is tilted backwards, and exits into the pelvis.³

While retrograde menstruation is not uncommon, the theory suggests that if someone has this in combination with an immune system that does not recognise these endometrial cells as not belonging outside of the uterus, the deposits of cells stick in the other parts of the body. The resulting inflammation causes adhesions and scarring to other parts of the affected person’s anatomy.⁴

The most prevalent theory is that it begins as a result of retrograde menstruation, when blood that should flow out of the vagina during your period instead flows back the other way

The diagnosis and management of endometriosis overlap. Since it is the bleeding of these deposits that cause symptoms, if medication is given that stops menstruation (such as the pill taken back to back for three months or injections that temporarily put your ovaries to sleep) and your symptoms disappear, it can be assumed that you have endometriosis without the need for surgery.

The only way to know for sure that you have endometriosis is to have laparoscopic (keyhole) surgery, during which a surgeon looks into the pelvis to identify deposits of uterine tissue. This procedure also can be a form of treatment: a surgeon can burn or remove the uterine tissue, as well as breaking apart bands of scarring and removing any endometriotic cysts which may be contributing to your symptoms. However, surgery carries its own risks (like infection or anaesthetic complications) which is why medical treatment is a reasonable way to first approach a suspected diagnosis.

Adenomyosis

Adenomyosis is a different condition to endometriosis. In adenomyosis, the uterine tissue lining (called the endometrium) is found in small pockets within the muscle wall of the uterus (the myometrium). This may sound deceptively similar to endometriosis, as it also involves tissue being found where it shouldn’t be. For a while the condition was known as endometriosis of the uterus.⁵

However, research suggests that adenomyosis is caused by a very different process, and there is no evidence to suggest that endometriosis causes adenomyosis. Current opinion posits that adenomyosis is usually found in a uterus that has had to heal after some sort of muscle trauma, such as a sharp curettage immediately post pregnancy (when any retained products from the pregnancy need to be removed surgically from the uterus),⁶ or after other surgery, such as when someone has had a caesarean.⁷

People that have adenomyosis can also experience painful periods. They are more likely to complain of heavy and prolonged menstruation

In theory, these processes blur the distinct line between the muscular and endometrial layers, allowing deposits from the endometrium to invade the muscle. This theory would also explain why adenomyosis is more prevalent among those who have already had children; it normally presents between the ages of 40 and 50.

These pockets of endometrial tissue buried within the uterus muscle layer still bleed under hormonal influence and so people that have adenomyosis can also experience painful periods. They are more likely to complain of heavy and prolonged menstruation, and to be found to have a bulkier, more tender uterus on examination as the small pockets of blood collect in the muscle layer of the uterus.

Diagnosing and treating adenomyosis

Previously, adenomyosis was a diagnosis that could only be made retrospectively, after performing a hysterectomy (surgical removal of the uterus), and finding adenomyosis within the muscle layer. However, advances in imaging now mean that highly skilled specialists in transvaginal ultrasounds and MRI images can reliably detect about 8 out of 10 cases of adenomyosis.⁸

Treatment of the two conditions may overlap: as with endometriosis, treatment for adenomyosis can involve stopping the menstrual cycle with synthetic hormones. If the deposits within the uterus muscle layer don’t bleed, they won’t cause further pain or heavy periods.

Adenomyosis can also respond to local hormonal treatment such as the Mirena intrauterine system (IUS), also used as contraception. The IUS releases a progesterone called levonorgestrel into the uterus and prevents the uterus lining becoming too thick.

Treatment for adenomyosis can involve stopping the menstrual cycle with synthetic hormones, as with endometriosis, so treatment of the two conditions does overlap.

If the main symptom of adenomyosis is heavy bleeding this can also be managed by burning the lining of the uterus (in keyhole surgery) , inserting a Mirena IUS, or even having a procedure called uterine artery embolisation. This is where all of the blood vessels that feed the uterus are visualised in an x-ray type of lab, and a doctor (an interventional radiologist) inserts small devices to block off specific arteries leading to the blood supply of sections of adenomyosis within the uterus muscle.⁹ This is the same procedure that is sometimes used to manage uterine fibroids (overgrowths of the uterine muscle causing heavy bleeding and a feeling of pressure).

Are the two conditions linked?

As you can see, there are many similarities in the way that these two conditions present and are managed. Endometriosis is more likely to present in younger people with cyclical pain symptoms, with adenomyosis more common in older people with heavier bleeding. It can be hard to differentiate between the symptoms without extensive examination and investigation.

The conditions do coexist in some, although it is unclear how often this happens. One systematic review (which looks at all the studies published in a particular area) found that the prevalence of adenomyosis with endometriosis ranged between 0% and 56% across 18 different studies. When the authors of the systematic review pooled all the studies together, they found that the prevalence of adenomyosis and endometriosis was about 6%.¹⁰ The incidence of adenomyosis among the general population is also unknown as historically it could only be diagnosed in hindsight, but it is believed to be anywhere from 5 to 70%.¹¹

What we do know is that having one of the conditions does not mean you will have the other, and that there is no connecting pathway that shows having endometriosis means that you will also one day develop adenomyosis. The ways they occur follow distinctly different anatomical and immunological pathways of development. Clinical examination and ultrasound diagnosis can help diagnose which condition you may have, or if you have both.

If you feel you have any of the symptoms listed and they are negatively affecting your quality of life then visiting your GP is a good place to start. They can take a history, perform a clinical examination, order blood tests and imaging investigations, and start you on some basic medicines that may be able to resolve your symptoms. They can also refer you on to a gynaecologist who can address your concerns.

Featured image is a person looking at themselves pensively, as if lost in thought, in the bathroom mirror. The mirror has fogged up and the person has wiped part of it clean in order to look at themselves

Last updated January 2024
Next update due 2027