Endometriosis is a chronic, systemic inflammatory condition in which tissue resembling the endometrium — the lining of the uterus — grows outside the uterine cavity. It affects an estimated 190–200 million individuals worldwide, representing approximately 1 in 10 women and people who menstruate. Despite this prevalence, it remains one of the most underdiagnosed and poorly understood conditions in women's medicine.

March is Endometriosis Awareness Month — a global initiative coordinated by organisations including Endometriosis UK, the Endometriosis Foundation of America, and the Worldwide EndoMarch. The 2026 programme includes EndoFound's medical conference centred on the theme "Endometriosis 2026: A Nerve-Centric Disease" — reflecting the growing clinical focus on the neurological mechanisms that drive the condition's characteristic pain.

The Condition — A Clinical Definition

In endometriosis, tissue that behaves similarly to the endometrium establishes itself outside the uterus — most commonly on the ovaries, fallopian tubes, pelvic peritoneum, and bowel, though it can occur in more distant sites including the diaphragm and, rarely, the lungs (thoracic endometriosis).

This ectopic tissue responds to the same hormonal cycle as normal endometrium — thickening, breaking down, and bleeding with each cycle. Unlike normal endometrial tissue, however, it has no pathway to exit the body. The result is localised inflammation, the formation of adhesions (scar tissue that can bind organs together), and in the case of ovarian involvement, the development of endometriomas — blood-filled cysts sometimes called "chocolate cysts."

The precise aetiology of endometriosis remains incompletely understood. Leading theories include retrograde menstruation (in which menstrual tissue flows backwards through the fallopian tubes into the pelvic cavity), immune system dysfunction that fails to clear this ectopic tissue, genetic predisposition, and hormonal and environmental influences. It is increasingly understood as a systemic inflammatory disease rather than a purely gynaecological one.

Signs and Symptoms: What to Recognise

Symptom presentation varies widely. Some individuals experience severe, debilitating symptoms; others have minimal or no symptoms despite significant disease burden. Pain is the hallmark presentation — typically cyclical, worsening over time, and correlating with hormonal fluctuation.

Managing Endometriosis: Current Clinical Approaches

There is currently no cure for endometriosis. Treatment is individualised, typically multidisciplinary, and focused on symptom management, disease progression, fertility preservation where relevant, and quality of life. No single treatment is universally effective, and many patients require a combination of approaches over time.

If any of the above apply, seek assessment from a gynaecologist with experience in endometriosis. A clinical diagnosis can now be supported by transvaginal ultrasound as a first-line investigation, per updated 2026 ACOG guidelines — though laparoscopy remains the definitive diagnostic standard for many presentations.

This article is for informational and educational purposes only and does not constitute medical advice. If you are experiencing symptoms consistent with endometriosis, please consult a qualified healthcare professional.