How is endometriosis definitively diagnosed?
The gold standard for diagnosing endometriosis is surgery. A surgeon takes tissue samples and examines them under a microscope to confirm the diagnosis.
Laparoscopy remains the most definitive diagnostic method because it allows the surgeon to see the disease directly and determine its type, location, and extent. However, it requires general anesthesia, carries surgical risks, and needs recovery time. Relying on surgery as the main path to diagnosis is a key reason it takes 5 to 12 years on average from first symptoms to diagnosis.
Importantly, surgery is not required before starting treatment. A clinical diagnosis, based on symptoms, physical examination, imaging, and other non-invasive tests, is enough to begin therapy.
Non-invasive diagnosis of endometriosis
Clinical evaluation
Diagnosis starts with a thorough clinical evaluation. Your doctor will ask about symptoms — painful periods, chronic pelvic pain, pain with intercourse, bowel or bladder symptoms, and infertility. This clinical assessment alone is enough to begin treatment.
Transvaginal ultrasound
Transvaginal ultrasound is the recommended first-line imaging test: widely available, low-cost, and radiation-free. Ultrasound is excellent at detecting ovarian endometriomas (endometriosis cysts) and, in experienced hands, detecting deep endometriosis. But it has limited ability to detect superficial peritoneal endometriosis, the most common type, present in about 80% of cases. Results depend heavily on the sonographer’s expertise, and detection rates drop if they are not an endometriosis specialist.
MRI
Your doctor may recommend MRI when deep endometriosis needs more detailed mapping, particularly for surgical planning. It can visualize disease involving the bowel, bladder, ureters, and vaginal wall. It has good sensitivity and specificity to detect deep endometriosis, but like ultrasound, it has limited ability to detect superficial peritoneal endometriosis.
A normal ultrasound or MRI does not rule out endometriosis. Many patients with significant symptoms have normal scans, especially those with superficial disease.
The diagnostic gap: superficial peritoneal endometriosis
The biggest limitation of current non-invasive methods is that superficial peritoneal endometriosis, the most common form, cannot be reliably detected without surgery. As a result, many patients with real disease are told their scans are “normal,” which can lead to frustration and delayed treatment. Closing this gap is one of the most important goals in endometriosis research.
Emerging non-invasive tests
Several promising new approaches aim to detect endometriosis, including superficial disease, without surgery. None is yet part of routine clinical practice guidelines, but progress is encouraging.
Saliva test (Endotest)
A test that analyzes tiny molecules called microRNAs in saliva has shown strong results, with high sensitivity and specificity. It is undergoing regulatory review and not yet widely available.
Blood-based test (HerResolve)
A blood test combining measurements of microRNAs, proteins, and a hormone, analyzed by a machine-learning algorithm. It achieved good diagnostic results but is undergoing regulatory review and not yet widely available.
Our center is actively conducting a clinical trial to validate the HerResolve test. Ask us if you would like to take part.
BCL6 endometrial biopsy (ReceptivaDx)
The most well-known endometrial biopsy test is the ReceptivaDx test, which measures overexpression of BCL6 (B-cell lymphoma 6) protein in endometrial tissue obtained via an office-based biopsy. It showed high diagnostic accuracy in some studies but not all. This test is available in the USA.
Nuclear imaging (DETECT study)
A specialized scan called SPECT-CT, combined with a radioactive tracer (⁹⁹mTc-maraciclatide) that targets areas of active inflammation and new blood vessel growth, was reported in The Lancet in 2026. The scan correctly identified the presence or absence of endometriosis in 84% of cases and detected superficial peritoneal endometriosis in 75% of patients who had it — a type that standard imaging typically misses. It also identified endometriosis in the chest. The scan was well tolerated, and larger trials are planned.
Other blood biomarkers
Many other blood-based approaches are being studied, including panels of proteins and inflammatory markers. However, no single blood biomarker has yet been validated for routine clinical use.
Importantly, the American College of Obstetrics & Gynecology 2026 guideline on diagnosis of endometriosis “recommends against the use of blood, urine, endometrial, or other biomarkers to diagnose endometriosis,” citing the low quality of supporting evidence.
What should patients know right now?
- Surgery is the gold standard for diagnosis, but is not required before starting treatment.
- Ultrasound is the recommended first imaging test and excels at detecting cysts and deep endometriosis, but can miss superficial disease.
- Normal imaging does not mean endometriosis is absent.
- New tests using saliva, blood, and specialized scans show real promise but are not yet part of routine care.
- If you have symptoms, do not wait for a “perfect” test. Seek care, advocate for an evaluation, and discuss treatment options with a healthcare provider.