How Is Endometriosis Diagnosed? History, Exam, Ultrasound, MRI and Laparoscopy

Step 1: the symptom history is the most important test

No scan or blood test carries as much diagnostic weight as a careful history. Clinicians who specialize in endometriosis ask about pain in each organ system and how it moves with the menstrual cycle: period pain that begins before bleeding and limits daily life, pelvic pain between periods, deep pain with sex, painful bowel movements or cyclical bowel changes, urinary urgency or burning with negative urine cultures, back, hip or leg pain, fatigue, and difficulty conceiving. A family history of endometriosis roughly doubles the likelihood.

This is why tracking symptoms for two or three cycles before an appointment makes such a difference. The clinician is looking for a pattern, and a written record shows one.

Step 2: the pelvic examination

A bimanual and speculum examination can reveal tenderness, nodules behind the uterus or along the uterosacral ligaments, a uterus that is fixed or tilted backward by adhesions, or visible lesions on the vaginal wall. A normal exam does not rule out endometriosis, especially superficial disease, but an abnormal exam is a strong pointer toward deep disease and guides which imaging to order.

Step 3: transvaginal ultrasound

Transvaginal ultrasound is the first-line imaging test. In experienced hands it reliably detects ovarian endometriomas ("chocolate cysts") and, with a dedicated protocol, deep endometriosis of the bowel wall, bladder and the space between the vagina and rectum. It also assesses whether the ovaries and uterus slide freely, a sign of adhesions.

Its weakness is superficial peritoneal endometriosis: small lesions on the lining of the pelvis that ultrasound cannot see. This is the most common form, particularly in adolescents, so a normal ultrasound should be reported as "no endometrioma or deep disease seen," not "no endometriosis."

Step 4: MRI, when ultrasound is not enough

Pelvic MRI maps deep endometriosis across the whole pelvis in one study and is especially useful for planning surgery when bowel, bladder or ureteral involvement is suspected, or when ultrasound is inconclusive. Like ultrasound, MRI misses most superficial lesions. Guidelines position it as a second-line test, not a screening tool.

What about blood tests?

There is no blood test for endometriosis. CA-125 can be elevated in endometriosis but also in many other conditions, and is normal in many women with the disease. The ESHRE 2022 guideline recommends against using biomarkers in blood, urine or endometrial tissue to diagnose endometriosis. Research into non-invasive markers is active, but nothing is validated for clinical use.

Step 5: clinical diagnosis and starting treatment

If the history and examination fit, guidelines from NICE (NG73) and ESHRE (2022) support making a clinical diagnosis of endometriosis and starting treatment, typically with anti-inflammatory painkillers and hormonal therapy, without waiting for surgery. Improvement on treatment supports the diagnosis. Lack of improvement is a reason to refer to a specialist and consider laparoscopy, not a reason to conclude the pain is something else.

Step 6: laparoscopy, to confirm and to treat

Laparoscopy is keyhole surgery under general anesthesia in which a camera is passed through the navel to inspect the pelvis. Visible lesions are removed (excision) or destroyed (ablation), and tissue is sent to pathology, which confirms the diagnosis. Laparoscopy remains the only way to definitively confirm superficial disease.

Its role has shifted: it is now primarily a treatment rather than a diagnostic hurdle. Guidelines caution against "diagnostic laparoscopy" that only looks; if surgery is performed, the disease should be treated at the same time by a surgeon trained to recognize and excise all of it, including lesions near the bowel, ureters and pelvic nerves. Most women go home the same day or the next; our guide to recovering from laparoscopy covers the weeks that follow.

Staging: what the numbers mean

After surgery, disease is often staged with the revised American Society for Reproductive Medicine (rASRM) system, stages I to IV, based on the extent of lesions and adhesions. Stage correlates poorly with pain: a woman with stage I disease can have severe pain and a woman with stage IV can have little. The Enzian classification describes deep disease in more detail, and the World Endometriosis Society recommends reporting both. Stage is useful for surgical planning and fertility counseling, not for judging how much a patient hurts.

Questions to ask your clinician

• Do you diagnose endometriosis clinically, or only after laparoscopy?
• Is the sonographer trained in deep endometriosis ultrasound, and will they assess the bowel and bladder?
• If my scan is normal, how will we rule out superficial endometriosis?
• If hormonal treatment does not help, what is the next step and when?
• If I need surgery, will all visible disease be excised in the same operation?