Endometriosis is usually called something else first

In a study of twenty-one Indian women with endometriosis confirmed by surgery, every one of them had been told it was something else first. Most often pelvic inflammatory disease, adenomyosis, fibroids or PCOS.

What it gets called instead

Pelvic inflammatory disease, adenomyosis, fibroids and PCOS all produce pelvic pain or heavy bleeding or both, and all four are more familiar than endometriosis. The NHS names the same overlap as the reason endometriosis is slow to diagnose.

The twenty-one women were interviewed in Assam and Delhi, in Assamese, Hindi and English. All had endometriosis confirmed by laparoscopy. All of them described knowing little about the condition before they were diagnosed.

Their symptoms began at an average age of 22.9. The diagnosis came at 29.2.

So what is endometriosis?

Endometriosis takes its name from the endometrium, the lining of the uterus. It is tissue like that lining, growing outside the uterus. WHO puts it as "endometrium-like tissue (usually found only in the lining of the uterus) grows outside the uterus", most often in the pelvis, sometimes in the abdomen or chest.

How common it is, nobody knows. Estimates put it at roughly 6 to 13 per cent of women worldwide, and the figure depends heavily on who is counted.

Those are measurements of different things. The first counts women nobody was looking at. The last counts women who were already in hospital.

The causes are unknown. An association with the immune system has been proposed and studied, and a meta-analysis of twenty-six population studies found it holds for some conditions and not others.

What separates it from the others

In a different study, one hundred and three women had a diagnostic laparoscopy in Kerala. Twenty-three turned out to have endometriosis and the other eighty did not. Every one of these was more common in the twenty-three.

The share of women in each group:

Each of these was recorded as present or absent. Severity was not measured, so nothing here says how bad any of it was.

For what counts as the first two, the NHS describes period pain that stops you doing your normal activities, and periods heavy enough to need a pad or tampon changed every one to two hours.

All 103 were being investigated for infertility at one hospital, so the comparison holds within that group.

Just over half the women with endometriosis reported spotting before a period. None of the eighty without it did. Anything in that table that looks familiar is worth writing down before an appointment, rather than trying to recall it in the room.

Why it takes six years

Imaging finds some endometriosis, and confirming it can still mean surgery. WHO notes that treatment does not have to wait for that confirmation. Every woman in both Indian studies had a laparoscopy.

Of those twenty-one women, all but one travelled for specialist care, between 250 and 1,380 km. Costs ran from ₹3,000 for a hormonal injection to ₹1,20,000 for surgery.

So the test that settles it is expensive and far away, and the names that do not require it are close to hand.

The average gap between the first symptom and the diagnosis, in those twenty-one women, was 6.3 years. The range ran from no delay at all to twenty-one years. WHO puts the average worldwide at between four and twelve years, so the Indian figure sits inside it.

Funding is moving faster since 2017

In the United States, research the National Institutes of Health categorised as endometriosis came to $6 million in 2017. Multiple sclerosis had $111 million that year, and cystic fibrosis $91 million.

The same table has a column for how many women in the United States have endometriosis. It is empty. The American government does not have a national figure either.

The categories below endometriosis in that table are uterine fibroids and PCOS. Menopause, vulvodynia and pelvic inflammatory disease sit near it.

By 2025 endometriosis had reached $37 million, a larger rise over those eight years than any of the conditions above it. Multiple sclerosis, over the same period, moved by one million.

Researchers at ICMR-NIRRCH, writing with colleagues in Colombo, name non-invasive diagnostics as a research priority for the region, alongside the political will and funding to pursue it.

What to take to an appointment

Spotting before a period was the one thing none of the eighty women without endometriosis reported. It is easy to leave out of an account built around heavy periods and pain.

We have turned this into a fuller set of questions you can keep open on your phone, sorted by where you are.