Endometriosis - Symptoms and causes (Mayo Clinic)

Tier 1: Established: peer-reviewed research or government health authority
Publisher: Mayo Clinic · Published: August 24, 2026 · Accessed: August 24, 2026

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• Endometriosis is an often-painful condition in which tissue similar to the inner lining of the uterus grows outside the uterus; it often affects the ovaries, fallopian tubes, and the tissue lining the pelvis.
• Endometriosis tissue acts as the lining inside the uterus would - it thickens, breaks down, and bleeds with each menstrual cycle - but it grows in places where it doesn't belong and doesn't leave the body.
• The main symptom is pelvic pain, often linked with menstrual periods and far worse than usual cramping; pain may also become worse over time.
• Common symptoms include painful periods (pelvic pain and cramping that may start before a period and last for days into it, plus lower back and stomach pain), pain with sex, pain with bowel movements or urination (most likely before or during a period), excessive bleeding (heavy periods or bleeding between periods), and infertility; fatigue, diarrhea, constipation, bloating, or nausea are more common before or during periods.
• The seriousness of pain is not a sign of the number or extent of endometriosis growths - you could have a small amount of tissue with bad pain, or lots of tissue with little or no pain; some people with endometriosis have no symptoms.
• Endometriosis sometimes seems like other conditions that cause pelvic pain, including pelvic inflammatory disease, ovarian cysts, or irritable bowel syndrome.
• Diagnosis: a provider asks about symptoms and may do a pelvic exam, ultrasound, or MRI; to definitively diagnose endometriosis, surgery is required - most commonly laparoscopy, with suspicious tissue removed and examined under a microscope.
• Treatment: first steps are pain medications or hormone therapy (birth control pills control the rise and fall of estrogen and progesterone in the menstrual cycle); if those fail and symptoms affect quality of life, surgery to remove endometriosis tissue may be considered.