What is endometriosis, really?

Women's health

4 July

Most people think of endometriosis as a condition where tissue similar to the lining of the uterus grows outside the uterus. While this is true, it's only part of the story.

Endometriosis affects around one in nine Australian women and people assigned female at birth by the age of 44, making it one of the most common chronic health conditions affecting reproductive-aged women. Although pelvic pain is one of its most recognised features, it can also affect the bowel, bladder, fertility, and many other aspects of health. The more researchers learn about endometriosis, the clearer it becomes that it's a complex condition involving much more than the pelvis alone. Understanding that broader picture can make the diagnosis feel much less confusing.

Endometriosis is more than tissue growing outside the uterus

For many years, endometriosis was described simply as a condition in which tissue similar to the lining of the uterus grows outside the uterus. While this remains a defining feature of the disease, researchers now recognise that this explanation doesn't tell the whole story.

Endometriosis involves much more than the lesions themselves. The condition is also associated with changes in the immune system, hormone signalling, inflammation, and the way the nervous system processes pain. These processes don't occur independently. They influence one another, helping to explain why endometriosis can look so different from one person to the next.

One observation that shaped this broader understanding is that symptom severity doesn't always match the amount of visible disease. Some people have widespread endometriosis but relatively mild symptoms, while others experience severe pain despite having only a small number of lesions. This tells us that pain in endometriosis isn't simply determined by the size or location of the lesions. Part of the explanation seems to involve the growth of new nerve fibres within the lesions themselves, adding to the processes already at play.

This is also why endometriosis is no longer viewed simply as a disease confined to the pelvis. Its effects appear to extend well beyond the lesions themselves, and researchers are still working out exactly how these different processes contribute to the range of symptoms people experience. That shift, from a disease defined by misplaced tissue to a condition shaped by multiple interacting systems, is changing how clinicians and researchers approach diagnosis, treatment, and future research.

What symptoms can endometriosis cause?

Although painful periods are one of the most recognised symptoms of endometriosis, the condition can present in many different ways. Some people experience only one or two symptoms, while others are affected across several areas of their health.

Symptoms often vary depending on where endometriosis is located, how the body responds to it, and the degree of inflammation and pain sensitisation that has developed over time.

Pelvic symptoms

Pain is the symptom most commonly associated with endometriosis, but it doesn't always follow the same pattern. Some people experience pain mainly during their menstrual period, while others have pelvic pain throughout the month. The pain may gradually become more persistent over time, or it may fluctuate from cycle to cycle.

Common pelvic symptoms include:

painful periods (dysmenorrhoea)
chronic pelvic pain
pain during or after sexual intercourse
pain around the time of ovulation.

Bowel and bladder symptoms

Because endometriosis can affect structures close to the bowel and bladder, some people experience symptoms that are easily mistaken for digestive or urinary conditions.

These may include:

abdominal pain
bloating
constipation or diarrhoea
pain when opening the bowels, particularly during menstruation
nausea
pain when passing urine
blood in the urine or bowel motions during menstruation (less common).

These symptoms often become worse around the menstrual period, although this isn't always the case.

Fertility

Some people discover they have endometriosis during investigations for difficulty conceiving, while others become pregnant without any difficulty. Although endometriosis can affect fertility, it doesn't necessarily mean someone will be unable to conceive. The relationship between endometriosis and fertility is complex and depends on many factors, including the location and severity of the disease, age, ovarian reserve and other aspects of reproductive health.

How can endometriosis affect everyday life?

Endometriosis can also affect aspects of health that extend beyond the pelvis. While these experiences don't affect everyone, they are increasingly recognised as important parts of the condition and can have a significant impact on a person’s quality of life.

Fatigue

Although pain is often the symptom that receives the most attention, many people with endometriosis describe fatigue as being just as disruptive to daily life. This isn't simply a matter of feeling tired after a poor night's sleep. While pain and disrupted sleep can certainly contribute, fatigue is likely to arise from several interacting factors, including ongoing inflammation, changes in the immune system, and the physical and emotional demands of living with a chronic condition.

Many people describe feeling physically and mentally drained, particularly during symptom flares. Some find it difficult to concentrate, while others feel they have less energy for work, exercise or social activities than they once did. Although fatigue isn't experienced by everyone, it's an important reminder that endometriosis is about much more than pelvic pain alone.

Emotional wellbeing

Living with endometriosis can affect emotional wellbeing in many different ways. For some people, the emotional impact comes from living with persistent pain, navigating repeated medical appointments, or coping with uncertainty before receiving a diagnosis. Pain can affect work, study, relationships, sleep and everyday activities, all of which can take a significant emotional toll over time.

Researchers are also beginning to understand that the relationship may be more complex than this alone. The same inflammatory and nervous system changes involved in endometriosis may also influence mood and emotional wellbeing, although exactly how these processes interact is still being investigated.

Studies consistently show that people with endometriosis experience higher rates of anxiety, depression and psychological distress than the general population. This doesn't mean these experiences are inevitable, but it does highlight the importance of recognising emotional wellbeing as part of the condition rather than viewing it as something separate.

What causes endometriosis?

Despite decades of research, we still don't know exactly why endometriosis develops. Rather than there being a single cause, researchers now believe that several different biological processes contribute to the development of endometriosis. Understanding exactly how these processes interact remains one of the biggest challenges in endometriosis research.

One of the best-known theories is retrograde menstruation. This proposes that during menstruation, some menstrual fluid flows backwards through the fallopian tubes into the pelvic cavity, allowing endometrial-like cells to reach areas outside the uterus. Although retrograde menstruation almost certainly plays a role in some cases, we now know it cannot explain the condition on its own. Retrograde menstruation is thought to occur in many women who never develop endometriosis, while endometriosis has also been found in locations that this theory cannot adequately explain.

Over time, several other theories have emerged. Some suggest that certain cells already present within the pelvis can transform into endometrial-like tissue under particular conditions. Others propose that stem cells, genetic susceptibility, immune dysfunction or the spread of cells through the blood or lymphatic system may contribute to the development of lesions.

Rather than competing explanations, these theories are increasingly viewed as pieces of a much larger puzzle. Instead of searching for a single cause, researchers now think endometriosis is likely to develop through the interaction of multiple factors, including genetics, hormones, the immune system and the local tissue environment. Exactly how these factors combine probably differs from one person to another.

How is endometriosis managed?

Managing endometriosis often involves addressing several aspects of the condition at once. Depending on the individual, this may include reducing pain, improving quality of life, preserving fertility, supporting day-to-day function, or helping to prevent symptoms from returning after treatment.

Because endometriosis affects people differently, there is no single treatment that's appropriate for everyone. Management is usually tailored to a person's symptoms, age, reproductive goals, the extent of disease, previous treatments, and their own preferences.

Pain management

Pain is one of the most common reasons people seek treatment. Depending on the individual, pain management may involve simple pain relief, hormonal therapies, physiotherapy, exercise, psychological support, or complementary approaches such as acupuncture. Often, a combination of treatments is more effective than relying on a single therapy alone.

Hormonal treatment

Hormonal treatments aim to reduce the hormonal stimulation of endometriosis lesions. Depending on the individual, options may include the oral contraceptive pill, progestins, hormonal intrauterine devices (IUDs), or other medications that suppress ovarian hormone production.

These treatments can be very effective for some people, although not everyone experiences the same degree of symptom relief, and side effects mean they aren't suitable for everyone.

Surgery

Surgery may be recommended when symptoms are severe, when fertility is affected, when imaging suggests more advanced disease, or when other treatments haven't been successful. The goal of surgery is usually to remove or destroy visible endometriosis lesions while preserving healthy tissue.

Although surgery can significantly improve symptoms, it doesn't guarantee that endometriosis won't return. Some people experience long-term relief, while others develop recurrent symptoms over time.

A multidisciplinary approach

Endometriosis affects much more than the reproductive system, which is why management often extends beyond medications or surgery alone. Depending on an individual's needs, care may involve a combination of gynaecologists, general practitioners, pelvic health physiotherapists, psychologists, dietitians, pain specialists and other health professionals working together to support different aspects of the condition.

For some people, acupuncture and Chinese medicine may also form part of this broader management plan. We'll explore the current evidence for these approaches in a separate article.