Diagnosing endometriosis: IDEA ultrasound, MRI and the new role of laparoscopy
Key Takeaways
Since ESHRE 2022, endometriosis is diagnosed first by imaging. Transvaginal ultrasound using the four-step IDEA protocol reaches a diagnostic accuracy comparable to surgery for endometrioma and deep disease in experienced hands. MRI complements the workup when ultrasound is inconclusive or when deep disease needs surgical mapping. CA-125 is no longer used for screening. Diagnostic laparoscopy is no longer routine: it is reserved for cases unresolved by imaging or cases that already require a surgical procedure.
Why the diagnostic pathway changed in 2022
For decades, laparoscopy was presented as the “gold standard” for diagnosing endometriosis. That doctrine contributed to a long diagnostic delay — often 7 to 10 years between first symptoms and confirmation. The ESHRE 2022 guideline (Becker et al., Human Reproduction Open) inverted that logic: imaging moves to first line, and laparoscopy is reserved for specific situations.
The aim is threefold: shorten the diagnostic delay, avoid surgery without clinical benefit, and allow early empirical treatment when the clinical picture is sufficiently suggestive.
This article details the modern diagnostic toolkit. For the overview (symptoms, treatment, infertility, surgery), see the complete endometriosis guide.
Transvaginal ultrasound following the IDEA protocol
The IDEA (International Deep Endometriosis Analysis) protocol, published by Guerriero et al., 2016, in Ultrasound in Obstetrics & Gynecology, standardises the ultrasound examination of a woman with suspected endometriosis in four sequential steps. It turns a “free” scan into a reproducible, systematic assessment.
Step 1 — uterus and adnexa
The operator evaluates:
- mobility of the uterus and any fixed retroversion;
- adenomyosis (asymmetric myometrial thickening, myometrial cysts, subendometrial lines or buds);
- ovarian cysts — size, echogenicity, vascularity — with particular care for identifying an endometrioma (cyst with finely echogenic homogeneous “ground-glass” content);
- morphological ovarian reserve (antral follicle count).
Step 2 — soft markers
Two indirect signs are sought:
- Ovarian tenderness on probe pressure — often reflects underlying pelvic inflammation.
- Ovarian fixation — the ovary does not glide freely against the pelvic wall or uterus, suggesting adhesions.
Step 3 — sliding sign
The operator applies gentle abdominal pressure and observes whether the uterus glides freely over the rectum in the Pouch of Douglas.
- Positive sliding sign — no adhesion in the posterior cul-de-sac.
- Negative sliding sign — “frozen” cul-de-sac, a strong indicator of deep disease.
Step 4 — anterior and posterior compartments
Systematic search for deep endometriosis nodules:
- Anterior compartment: bladder wall, vesico-uterine pouch.
- Posterior compartment: utero-sacral ligaments, recto-vaginal septum, rectal and sigmoid wall, vagina.
Deep nodules appear as hypoechoic, irregular, poorly defined lesions, sometimes containing small cystic areas. Mapping them lets the surgeon plan ahead.
Diagnostic performance
In experienced hands, IDEA ultrasound reaches a sensitivity and specificity comparable to surgical diagnosis for ovarian endometrioma and deep endometriosis, especially recto-sigmoid and utero-sacral lesions. Its main limit is the detection of superficial peritoneal lesions, which are not visible on imaging by any modality.
Examination quality depends heavily on the operator. An IDEA scan performed by a sonographer untrained in this protocol may underestimate disease.
Pelvic MRI: when and why
MRI is requested in several situations:
- Inconclusive ultrasound in a symptomatic patient.
- Suspected deep endometriosis requiring detailed pre-operative mapping (rectum, sigmoid, ureters, bladder, diaphragm).
- Discordance between clinical findings and ultrasound.
- Patients who cannot tolerate transvaginal scanning.
The protocol includes multiplanar T2 sequences, T1 sequences with and without fat saturation to identify old blood typical of endometriosis, and sometimes rectal or vaginal gel to better distinguish structures.
MRI accuracy rivals expert ultrasound for recto-sigmoid, utero-sacral and recto-vaginal involvement. It remains limited for superficial peritoneal lesions.
CA-125: not for screening
CA-125 is a serum tumour marker sometimes elevated in endometriosis, but its sensitivity is poor (around 20–50 % in stages I–II) and it can be raised in many unrelated situations (normal menstruation, functional ovarian cyst, pelvic inflammatory disease, fibroids, ovarian cancer, pregnancy, ascites, peritonitis).
ESHRE 2022 explicitly recommends against it for:
- screening of an asymptomatic woman;
- ruling out the diagnosis in a symptomatic woman.
Its role is narrow: it may be used in the follow-up of known endometriosis when other tools fall short, or in cases of an ovarian mass with atypical ultrasound features where the differential diagnosis with ovarian cancer is raised.
The new place of laparoscopy
ESHRE 2022: “Laparoscopy is no longer the diagnostic standard and is recommended only in patients with negative imaging and/or where empirical treatment was ineffective or inappropriate.”
When laparoscopy is still indicated
- Negative imaging in a symptomatic woman whose pain is not controlled by an empirical first-line treatment.
- Therapeutic indication: excision of painful lesions, adhesiolysis, treatment of deep endometriosis with bowel or urinary tract involvement.
- Infertility workup in selected situations (for example, suspected superficial endometriosis not visible on imaging in a young patient with preserved chance of spontaneous pregnancy).
- Suspected associated pathology not clarified by imaging.
What laparoscopy should no longer be
- A mandatory step before any medical treatment.
- A screening tool in an asymptomatic woman with “clinical doubt.”
- A reflex response to pelvic pain before a properly conducted medical trial.
Empirical treatment: a validated option
Faced with a suggestive clinical picture and reassuring initial imaging (no endometrioma, no deep disease, no suspicious mass), an empirical treatment with NSAIDs and a combined hormonal contraceptive in a continuous regimen may be offered. Lack of response after 3 to 6 months prompts re-imaging, an MRI if not done already, and a discussion of laparoscopy.
Pitfalls and limits to keep in mind
- Imaging does not see everything: superficial peritoneal lesions can be entirely invisible. A negative scan in a very symptomatic patient should not be interpreted as “no endometriosis.”
- The diagnostic delay remains a problem: per De Corte et al., BJOG 2025, it ranges from a few months to more than 12 years across countries, and remains long even in well-organised healthcare systems.
- Operator-dependent examinations: IDEA ultrasound and MRI quality depend heavily on operator experience. A centre with imaging expertise in endometriosis is a major asset.
- Associated adenomyosis: frequent in women with endometriosis and should be systematically sought, because it changes management.
In practice
- For suggestive symptoms (progressive dysmenorrhoea, deep dyspareunia, cyclic digestive or urinary pain, infertility), request a first-line transvaginal ultrasound using the IDEA protocol with an experienced sonographer.
- Add pelvic MRI when ultrasound is negative and the clinical picture remains suggestive, or when deep endometriosis is suspected.
- Do not request CA-125 for screening or for ruling out the diagnosis.
- Discuss an empirical treatment with NSAIDs and a continuous combined contraceptive before contemplating a purely diagnostic laparoscopy.
- Reserve laparoscopy for therapeutic indications or cases unresolved by imaging after a well-conducted empirical trial.
FAQ
Does a normal ultrasound rule out endometriosis?
No. Ultrasound cannot see superficial peritoneal lesions and may miss early disease. If your symptoms remain suggestive despite a normal scan, MRI or an empirical treatment is discussed before any negative conclusion.
Should ultrasound be performed during menstruation?
No, it is not required. IDEA ultrasound can be performed at any cycle phase. Some deep nodules may be slightly more conspicuous in the second half of the cycle, but the overall quality of the examination does not depend on a strict window.
Why is my doctor not ordering CA-125?
Because it is neither useful for screening, nor for confirmation, nor for exclusion of endometriosis. Its sensitivity is low in early stages and it can be raised in many unrelated situations. ESHRE 2022 explicitly advises against it in this context.
Is MRI systematic after ultrasound?
No. If IDEA ultrasound is conclusive (well-described endometrioma, clearly characterised deep signs, or a clearly reassuring scan against a coherent clinical picture), MRI is not mandatory. It becomes useful when ultrasound is inconclusive, when deep endometriosis is suspected, or to plan surgery.
Will I need a laparoscopy to confirm the diagnosis?
Not systematically. Current guidelines avoid purely diagnostic laparoscopy. It is offered if imaging is negative despite persistent symptoms, or if surgery is independently indicated to treat pain, deep disease or infertility.
How long does diagnosis take?
When the pathway is well coordinated (a clinician trained in endometriosis, an experienced sonographer, MRI availability), a working diagnosis can be reached within a few weeks. The diagnostic delay remains a global problem: you may need to insist on a systematic evaluation when symptoms persist.
Sources
- Becker CM, Bokor A, Heikinheimo O, et al. ESHRE guideline: endometriosis. Human Reproduction Open 2022;2022(2):hoac009.
- Guerriero S, Condous G, van den Bosch T, et al. Systematic approach to sonographic evaluation of the pelvis in women with suspected endometriosis (IDEA consensus). Ultrasound Obstet Gynecol 2016;48:318–332.
- Keckstein J, Saridogan E, Ulrich UA, et al. The #Enzian classification: A comprehensive non-invasive and surgical description system for endometriosis. Acta Obstet Gynecol Scand 2021;100:1165–1175.
- De Corte P, Klepsch S, Christ B, et al. Diagnostic delay in endometriosis: a contemporary systematic review. BJOG 2025.
- WHO. Endometriosis Fact Sheet, March 2023.
The content has been created by Dr. Senai Aksoy and medically approved.