The science behind Emenla.

Lesions outside the uterus

Endometriosis is a condition in which tissue similar to the lining of the uterus grows outside it. The World Health Organization describes it as chronic and often painful, and estimates that it affects about 10% of women and girls of reproductive age worldwide, around 190 million people.[1] The lesions most often sit on the ovaries and on the peritoneum, the lining of the pelvis, but they can involve the bowel, the bladder and, rarely, sites beyond the pelvis.[10][12] The disease is inflammatory and depends on oestrogen, which is why it tends to appear after the first period and quieten after the menopause.[10]

A systemic disease, not a pelvic one

For a long time endometriosis was described as a disease of the pelvis. A 2021 review in The Lancet argues that it is better understood as a systemic disease: it changes metabolism, immune signalling and the processing of pain far from the lesions themselves, and it is associated with fatigue, anxiety and low mood.[11] The New England Journal of Medicine review of 2020 makes a similar point from the clinic: the presentations vary widely, from severe period pain to bowel symptoms to infertility with little pain at all.[10]

Pain does not track the lesion

The amount of disease found at surgery does not correspond to how much it hurts. Small, superficial lesions can cause severe pain, and extensive disease is sometimes found in people who report none.[10][11] Part of the explanation is that persistent pain changes the nervous system itself, a process called central sensitisation, so that pain can outlast and spread beyond its original source.[11][12] This is why the story matters as much as the scan: what a person reports, when, and in what pattern carries information that imaging cannot.[12]

An old disease with a short modern history

Descriptions that match endometriosis appear in medical writing going back centuries, under other names and with other explanations.[19] The modern account begins in 1927, when John Sampson proposed that menstrual tissue flowing backwards through the fallopian tubes could implant in the pelvis.[20] Retrograde menstruation happens in most women, though, and only some develop the disease, so no single theory explains every lesion. Genetics, immunity and the hormonal environment all play a part, and the causes are still debated.[18]

Four to eleven years

Studies of the delay between first symptoms and a diagnosis keep returning the same order of magnitude. A 2024 scoping review of the published research put the range at roughly four to eleven years, depending on the country and the method.[5] In Austria and Germany, a multicentre study of 171 patients found a median of 10.4 years, and 74% had been given a different explanation first.[7] In the United Kingdom, a specialist centre reported a median of 8 years, with a quarter of patients waiting 14 years or more, and concluded that the delay had not improved in two decades.[8]

Normalised at both ends

Why so long? In a qualitative study of women in the UK, Ballard and colleagues found that the delay had two halves. First the person normalises the pain: periods are expected to hurt, and the people around her say so. Then the clinician does the same, so the symptoms are read as ordinary, or put down to something else, and the consultation ends without a plan.[6] Denny's interviews describe the same experience from the inside: being told repeatedly that nothing is wrong, and beginning to doubt the pain oneself.[15] The Austrian and German study found that normalisation of period pain, by patients and by their mothers, measurably lengthened the delay.[7]

The language of pain

Pain that is hard to describe is harder to act on. Bullo's analysis of how people with endometriosis talk about their pain found that they reach for metaphor because the plain vocabulary of the clinic does not fit: being stabbed, being set on fire, something pulling from the inside.[14] Those descriptions carry information about the kind of pain and its pattern, but they are easy to dismiss as exaggeration, and the gap between the two vocabularies costs credibility and time.[14][15]

What the wait costs

The burden is measurable. Across sixteen centres in ten countries, Nnoaham and colleagues found that each affected woman lost on average 10.8 hours of work a week, mostly through working less effectively while in pain, after a delay of 6.7 years between symptoms and a surgical diagnosis.[9] In referral centres across ten countries, Simoens and colleagues put the average annual cost at 9,579 euros per person, two thirds of it lost productivity, a burden they describe as similar to diabetes, Crohn's disease and rheumatoid arthritis.[17] The Endometriosis Health Profile, a questionnaire built in 2001 to measure quality of life in this condition specifically, exists because the general instruments missed what the disease does to daily life.[16]

A call to action, 2019

For decades the definitive diagnosis was surgical: laparoscopy, with the lesions seen and, ideally, confirmed under a microscope. In 2019 a group of specialists led by Agarwal argued, in a paper they called a call to action, that waiting for surgery was itself the delay, and that a clinical diagnosis made from the symptoms, an examination and imaging was enough to start treatment.[13]

ESHRE, 2022

The European guideline of 2022 adopted that position. Laparoscopy is no longer the required first step; a diagnosis can rest on the history, an examination and imaging, and treatment can begin without surgery. The guideline also recognises that much of the diagnosis is the pattern of symptoms over time, and it lists the ones to ask about: pain with periods, chronic pelvic pain, pain with sex, with the bowel and with the bladder, and infertility.[2]

NICE NG73

The UK guideline tells clinicians to suspect endometriosis in anyone presenting with one or more of the following: chronic pelvic pain, period pain that affects daily activities and quality of life, deep pain during or after sex, period-related or cyclical bowel symptoms, period-related or cyclical urinary symptoms, or infertility together with any of these.[3] Every one of those is something a person notices and can write down, with a date, long before anyone examines her.

ACOG, 2026

In March 2026 the American College of Obstetricians and Gynecologists published its own practice guideline, and it says the same in plainer words: a clinical diagnosis made from the symptoms, the history and a physical examination is enough to begin treatment, and surgery is not needed to confirm it first.[4]

Whose record it is

If the diagnosis begins with the history, then the history is evidence, and it belongs to the person who lived it. A dated record of what hurt, when, and how it lined up with periods is what all three guidelines ask a clinician to look for. It is also health data, which the General Data Protection Regulation places in a special category with stricter rules than almost any other kind of information.[21] That is the reason nothing written in Emenla leaves the phone.