Does Endometriosis Show Up on Ultrasound? A Guide to Ultrasound, MRI and Laparoscopy
Key Takeaways
Ultrasound can detect ovarian endometriomas and many deep endometriosis lesions when performed by an experienced examiner. It may miss superficial disease, so a normal scan does not rule out endometriosis. Further assessment may include specialist imaging or laparoscopy, depending on symptoms, previous treatment and whether you are trying to conceive.
Key evidence: ESHRE guideline: endometriosis (2022) NICE NG73 — endometriosis diagnosis (updated 2024) IDEA protocol — Guerriero et al., 2016
Does endometriosis show up on ultrasound?
Yes — certain forms of endometriosis can be detected on ultrasound. This is particularly true for ovarian endometriomas and many deep infiltrating lesions, when an experienced operator follows a structured protocol.
In contrast, superficial peritoneal endometriosis often remains invisible. A normal ultrasound therefore does not rule out the diagnosis.
Waiting for surgical confirmation before acknowledging a diagnosis has historically prolonged delays for women who already have symptoms suggestive of endometriosis.
The normalization of painful periods, hesitation or delays in referral to specialists, and limited access to expert imaging also contribute. Diagnostic delay remains widespread, varying significantly across countries and healthcare systems.
The ESHRE 2022 guidelines recommend imaging in the diagnostic work-up. Laparoscopy is considered when it could change the diagnosis or treatment, rather than as an automatic first step.
The goal is practical: shorten delays, prevent unhelpful surgeries, and initiate symptom-directed care sooner. A patient whose immediate priority is pregnancy does not follow the same path as one whose primary need is pain relief.
This guide reviews the diagnostic tools available today. For a broader overview: complete endometriosis guide, endometriosis and infertility, and endometriosis symptoms.
Diagnosis starts before the scan: symptoms and examination
Imaging never replaces attentive listening or a careful clinical examination.
Key clinical indicators that raise suspicion include:
- Periods that become progressively more painful and disabling (dysmenorrhea)
- Deep pain during or following sexual intercourse (dyspareunia)
- Cyclical bowel symptoms, painful defecation during menstruation (dyschezia), or rectal bleeding
- Cyclical urinary discomfort, pain when emptying the bladder, or blood in the urine (dysuria/hematuria)
- Chronic pelvic pain that persists outside of menstruation
- Difficulty conceiving, particularly alongside other symptoms of endometriosis
- A first-degree family history of endometriosis (mother or sister)
- Marked, unexplained chronic fatigue
- Direct disruption of professional work, studies, intimate relationships, or daily life
Prior surgeries and the patient’s degree of response to painkillers or hormonal therapies also provide valuable diagnostic clues.
During the examination, the clinician checks whether the uterus moves freely. Tender areas or small nodules at the back of the vagina, pain along the ligaments supporting the uterus, or a lump near an ovary can also raise suspicion.
A normal pelvic examination does not rule out endometriosis, particularly in early stages or superficial disease. NICE recommendations advise offering pelvic ultrasound whenever endometriosis is suspected, even when examination findings are normal.
When to seek prompt assessment
Seek emergency care now for sudden severe pelvic pain, fainting, heavy bleeding with marked dizziness or weakness, or severe abdominal pain with vomiting and inability to pass stool or gas. Do not wait for an endometriosis appointment. If pregnancy is possible, severe pain or bleeding with faintness can be a sign of an ectopic pregnancy; NICE recommends direct emergency assessment when pain, bleeding or circulatory instability is concerning.
Contact a clinician urgently, usually the same day, for pelvic pain or bleeding with a positive pregnancy test, fever with pelvic pain, or visible blood in the urine. Severe symptoms require emergency care.
Other findings need prompt specialist assessment rather than being assumed to be endometriosis:
- An atypical or rapidly enlarging ovarian mass
- New pelvic pain or a new mass after menopause
- Suspicion that a ureter is obstructed and the kidney is swelling (hydronephrosis)
The urgency depends on symptoms and examination findings. A new or atypical mass should be assessed even if you have previously been diagnosed with endometriosis.
Transvaginal ultrasound following the IDEA protocol
The IDEA (International Deep Endometriosis Analysis) protocol, published by Guerriero et al. in 2016, transforms an unstructured scan into a systematic four-step assessment.
Findings can also be classified using mapping systems such as #Enzian, which provide a common language across surgical and imaging teams regarding disease extent.
If transvaginal ultrasound is not appropriate or acceptable—including in adolescents or anyone who declines vaginal examination—a transabdominal pelvic ultrasound can be offered as a first step.
Dedicated pelvic MRI, or in selected clinical contexts transrectal sonography, may follow depending on symptoms, suspected disease sites, and patient preference.
Step 1 — Uterus and ovaries
The examiner evaluates:
- How freely the uterus moves, including whether it is tilted backwards and fixed in position
- Signs of adenomyosis, where tissue similar to the uterine lining is found within the muscle wall; the scan looks for changes such as uneven thickening or tiny cysts in that wall
- Ovarian cysts—their size, appearance and blood flow—with particular attention to an endometrioma, a blood-filled cyst sometimes called a “chocolate cyst”
- When fertility is part of the assessment, the antral follicle count (AFC): the number of small follicles visible in the ovaries. This helps assess ovarian reserve but does not diagnose endometriosis.
Discovering an endometrioma does not mean it must automatically be removed.
Before deciding on surgery, your clinician considers your age, symptoms, previous ovarian operations, whether one or both ovaries are affected, and your pregnancy plans. Anti-Müllerian hormone (AMH), a blood test used to assess ovarian reserve, and the follicle count also help inform this discussion.
Step 2 — Indirect signs (“soft markers”)
Two indirect markers are evaluated:
- Site-specific tenderness: pain at a particular site when the ultrasound probe applies gentle pressure. It can help locate a problem but does not, by itself, establish endometriosis.
- Ovarian mobility: whether the ovary slides freely against the pelvic sidewall and uterus, or appears fixed by adhesions.
Step 3 — The sliding sign
Gentle pressure with the ultrasound probe and, when needed, a hand on the abdomen helps assess whether the bowel and uterus slide freely against each other. The space behind the uterus is called the pouch of Douglas.
- Positive sliding sign: free movement makes it less likely that adhesions have closed this space. It does not exclude adhesions elsewhere in the pelvis.
- Negative sliding sign: restricted or absent movement suggests that tissues may be stuck together. This can occur with deep endometriosis behind the uterus.
Step 4 — Anterior and posterior compartments
A systematic search for deep infiltrating nodules:
- In front of the uterus: the bladder wall and the space between the bladder and uterus.
- Behind the uterus: its supporting ligaments, the tissue between the vagina and rectum, the lower bowel wall, and the vagina.
Deep nodules may look darker than surrounding tissue on ultrasound and have irregular or indistinct borders. The examiner interprets their appearance together with their location and the other findings.
Accurate mapping clarifies disease extent, directs the patient to the right specialist team, and guides surgical planning if an operation is required.
Surgery involving the bowel, bladder, or ureters requires an experienced multidisciplinary team.
Diagnostic performance
In experienced hands, transvaginal ultrasound is highly accurate for ovarian endometriomas. Expert scanning is similarly reliable for rectosigmoid deep infiltrating endometriosis.
For other deep endometriosis sites, diagnostic accuracy varies according to lesion location and operator expertise.
Superficial peritoneal endometriosis remains the main blind spot: lesions are usually too thin or discrete to detect reliably on ultrasound or MRI. A normal scan does not rule them out.
An IDEA scan performed without dedicated training in the protocol can underestimate disease burden. Operator experience is essential.
Pelvic MRI: when and why
Specialist pelvic MRI can help clarify findings and map deep disease. The ESUR 2025 consensus recommends MRI when ultrasound is inconclusive or normal despite ongoing symptoms, and for planning surgery or investigating symptoms that persist after surgery. The specialist decides how it would help in your case.
- Ultrasound is inconclusive or normal while symptoms remain suggestive of endometriosis
- Deep infiltrating endometriosis requires fine anatomical mapping of the rectum, sigmoid, ureters, bladder, or other pelvic compartments
- Clinical examination findings and ultrasound results disagree
- Transvaginal ultrasound is unsuitable or declined: abdominal ultrasound and specialist assessment can help determine whether MRI is useful
An endometriosis MRI uses a dedicated imaging protocol to look for blood-containing lesions and define their relationship to nearby organs. The radiology team will explain any preparation required for your examination.
Specialized MRI and expert ultrasound are complementary rather than competing modalities. Both share similar limitations when detecting superficial peritoneal disease.
CA-125: not for screening or routine monitoring
CA-125 is a blood biomarker that can rise in endometriosis. However, it can also rise in many common or unrelated conditions: menstruation, functional ovarian cysts, pelvic infections, uterine fibroids, ovarian cancer, pregnancy, ascites, or peritonitis.
Its diagnostic sensitivity is especially poor in early or mild disease.
The ESHRE 2022 guidelines recommend against using biomarkers such as CA-125 to screen asymptomatic women, or to confirm or exclude endometriosis in symptomatic patients.
It has no role in routine monitoring of disease activity or response to treatment.
It may occasionally form part of an oncology work-up when an ovarian mass appears atypical and malignancy must be ruled out. It should never be interpreted in isolation and cannot distinguish endometriosis from an ovarian malignancy on its own.
The modern role of laparoscopy
Laparoscopy is no longer an automatic first step in diagnosing endometriosis.
The ESHRE guidelines no longer treat surgical visualization as the mandatory diagnostic gold standard before initiating care. Surgery is primarily considered when imaging is negative but clinical suspicion remains high, or when empirical medical treatment has failed, is unsuitable, or is not desired.
The NICE guidelines updated in 2024 follow this direction, noting that laparoscopy may still be considered when ultrasound or MRI is normal but clinical symptoms persist.
The central question is always: would surgery alter management—given the patient’s symptoms, personal priorities, and reproductive goals?
When laparoscopy remains indicated
- Negative imaging in a symptomatic patient whose pain is uncontrolled, or for whom empirical hormonal therapy is inappropriate
- A clear therapeutic objective: excising painful lesions, releasing dense adhesions, or treating deep endometriosis involving the bowel or urinary tract
- Carefully selected infertility scenarios—see below
- Suspicion of coexisting pelvic pathology that imaging cannot resolve
What laparoscopy should no longer be
- A compulsory hurdle before accessing medical symptom relief
- A screening tool in an asymptomatic woman with vague suspicion
- A reflex response to pelvic pain before exploring goals and conservative options
During laparoscopy, the surgeon may take a biopsy of suspicious tissue. A negative result does not fully exclude endometriosis: the sample may not contain the affected tissue. NICE distinguishes a negative biopsy from a normal, systematic examination of the pelvis at laparoscopy.
If that systematic examination is normal and the findings are documented, including images, NICE advises explaining that endometriosis is unlikely and discussing other ways to investigate and treat the symptoms. A normal result does not make your pain any less real.
Treating pain while the assessment continues
Treatment for suspected endometriosis can begin without surgical confirmation. NICE recommends arranging ultrasound and any referral alongside initial medical treatment; these steps need not happen one after another. Treatment choices depend on your symptoms, medical history and pregnancy plans.
Pain relief can be discussed whether or not you are trying to conceive, with medicines chosen accordingly. If you are not currently trying to conceive, a combined hormonal contraceptive or a progestin may also be an option for pain. This is called empirical treatment: treating a suspected condition before surgical confirmation. Improvement does not by itself prove endometriosis, and persistent symptoms still need review.
If you are trying to conceive, hormonal suppression is not a treatment for infertility. The ESHRE guideline advises against ovarian suppression to improve fertility. Pain relief should still be discussed, with treatment chosen to fit your pregnancy plans.
Age, ovarian reserve, tubal patency, semen analysis, the duration of infertility, and the potential place of surgery or IVF should be evaluated without delay.
Agree with your clinician when to review whether treatment is helping and whether you have side effects.
Persistent or worsening pain, poor tolerance, an emerging desire for pregnancy, or suspicion of bowel, bladder, or ureteral involvement warrant earlier specialized imaging or surgical referral.
If hormonal therapy is unsuitable because pregnancy is desired, management should promptly shift toward a fertility work-up rather than prolonged suppression.
Does suspected endometriosis change the infertility work-up?
AMH and the antral follicle count do not diagnose endometriosis. They help assess ovarian reserve when planning fertility treatment or discussing ovarian surgery; neither predicts exactly how much reserve an individual might lose after an operation.
Tubal patency assessment should not be skipped when relevant, and semen analysis must be arranged without unnecessary delay. Hormonal suppression is not a fertility treatment.
Diagnostic laparoscopy is not a routine test for every woman with normal pelvic ultrasound and open fallopian tubes.
The decision rests on female age, ovarian reserve, pain severity, prior surgeries, duration of infertility, semen parameters, tubal findings, and other reproductive factors. It also depends on whether timed intercourse or IVF represents the realistic next step.
For broader surgical context: laparoscopy vs open surgery. The ESHRE guidelines frame surgical decisions similarly—around these individualized prognostic factors and patient preference, rather than an automatic diagnostic label.
The decision is not simply whether surgery could confirm endometriosis. It is whether its likely benefits outweigh its risks and any delay to fertility treatment.
Even with a normal ultrasound, severe pain, deep pain during intercourse, bowel or urinary symptoms, nodules or restricted organ mobility on examination, or MRI findings suggesting deep disease can justify discussing laparoscopy. The question is whether surgery would meaningfully change diagnosis or treatment; none of these findings makes an operation automatic.
If symptoms are mild or absent, particularly with older reproductive age, limited ovarian reserve, longstanding infertility, or a sperm or tubal factor, completing the basic fertility assessment and proceeding to treatment may be more useful than diagnostic laparoscopy. Depending on that assessment, treatment may involve intrauterine insemination (IUI) or IVF; the two are not interchangeable for every patient.
When age, low ovarian reserve or another infertility factor makes time important, an operation may delay fertility treatment. The reserve concern relates particularly to surgery on an ovary, such as removing an endometrioma, rather than diagnostic inspection alone. ESHRE does not recommend routine endometrioma surgery before IVF solely to improve live-birth outcomes, because benefit has not been shown and ovarian reserve may be reduced.
The decision must serve the pregnancy plan, not merely confirm a diagnostic label.
What can mimic endometriosis?
A normal scan should never end the clinical inquiry, but persistent pelvic pain should not be automatically attributed to endometriosis either.
Key differential diagnoses and coexisting conditions include:
- Adenomyosis
- Uterine fibroids
- Pelvic inflammatory disease (PID)
- Benign ovarian cysts
- Irritable bowel syndrome (IBS)
- Bladder pain syndrome (interstitial cystitis)
- Pelvic floor muscle dysfunction
- Neuropathic pelvic pain
- Other gastrointestinal or urological disorders
A methodical evaluation helps distinguish between these possibilities rather than attributing every pelvic symptom to a single condition.
Pitfalls and limits to keep in mind
- Imaging cannot see everything. Superficial peritoneal lesions are frequently invisible. A negative scan in a symptomatic patient is never equivalent to “no endometriosis.”
- A normal clinical exam does not rule out disease. Physical findings may be entirely normal, especially in early or superficial disease.
- Diagnostic delays persist. In De Corte et al., BJOG 2025, study averages or medians ranged from 0.3 to 12 years, but the studies measured different intervals. The time from first symptoms to diagnosis ranged from 5 to 12 years; the interval from first consultation to diagnosis ranged from 0.3 to 8.6 years. These figures are not a prediction of your own waiting time.
- Operator expertise matters. The diagnostic yield of IDEA ultrasound and MRI depends directly on specialized training and experience.
- Adenomyosis frequently coexists with endometriosis and must be deliberately sought on imaging, as it can directly influence fertility and symptom management.
In practice
- Bring a symptom history to your appointment. Your clinician can discuss an examination and transvaginal ultrasound, ideally with an examiner trained in endometriosis assessment, or an alternative if this examination is unsuitable or you decline it.
- Specialist pelvic MRI may help when ultrasound is inconclusive or normal but symptoms persist, or when deep disease needs more detailed mapping.
- CA-125 cannot reliably confirm or exclude endometriosis and is not a routine test for monitoring it.
- Discuss empirical hormonal therapy only when pain relief is the primary goal and pregnancy is not currently being attempted.
- When pregnancy is the objective, prioritize the fertility evaluation—age, ovarian reserve, tubal status, semen analysis, and duration of infertility—rather than hormonal suppression.
- Reserve laparoscopy for situations where surgical findings would change management: clear therapeutic necessity, unresolved pain after appropriate evaluation, or carefully selected infertility scenarios.
FAQ
Does endometriosis show up on ultrasound?
Often yes — especially ovarian endometriomas and many deep lesions — when a trained operator uses the IDEA protocol. Ultrasound may miss superficial peritoneal lesions. A normal scan does not close the case if symptoms persist.
Does a normal ultrasound rule out endometriosis?
No. Ultrasound may miss superficial disease. If symptoms persist, discuss further assessment and pain relief with your clinician. Pregnancy plans help determine whether hormonal treatment, a fertility assessment or other investigations are appropriate.
Should ultrasound be performed during menstruation?
No. An IDEA-protocol ultrasound can generally be performed at any stage of the menstrual cycle. There is no strict cycle window required for a reliable examination, although timing may be adjusted for comfort, bleeding or local practice.
Why is my doctor not ordering CA-125?
Because it does not usefully screen, confirm, exclude or routinely monitor endometriosis. It is often normal early on, and it rises in many unrelated situations. ESHRE 2022 advises against biomarkers such as CA-125 in this diagnostic context.
Is MRI always needed after ultrasound?
No. MRI is not needed after every ultrasound. A specialist may recommend it if ultrasound is inconclusive or normal despite persistent symptoms, or if more detail is needed to plan treatment for deep disease.
Will I need a laparoscopy to confirm the diagnosis?
Not routinely. Guidelines avoid automatic diagnostic laparoscopy. It may still be considered if imaging is negative despite strong ongoing suspicion, if empirical treatment has failed or is unsuitable, or if surgery is independently needed for pain, deep disease or a selected infertility scenario.
How long does diagnosis take?
There is no reliable fixed timeframe. It depends on your symptoms, access to specialist imaging and whether further assessment is needed. A normal scan should not end the assessment if symptoms persist. Ask what the next step is and when your symptoms and treatment will be reviewed.
Sources
- Becker CM, Bokor A, Heikinheimo O, et al. ESHRE guideline: endometriosis. Human Reproduction Open 2022;2022(2):hoac009.
- National Institute for Health and Care Excellence. Endometriosis: diagnosis and management (NG73). Updated 2024.
- National Institute for Health and Care Excellence. Ectopic pregnancy and miscarriage: diagnosis and initial management (NG126), recommendations 1.3.1–1.3.9.
- Guerriero S, Condous G, van den Bosch T, et al. Systematic approach to sonographic evaluation of the pelvis in women with suspected endometriosis, including terms, definitions and measurements: a consensus opinion from the International Deep Endometriosis Analysis (IDEA) group. Ultrasound Obstet Gynecol 2016;48:318–332.
- Kanti FS, Gorak Savard R, Bergeron F, et al. Transvaginal ultrasound and magnetic resonance imaging in the diagnosis of endometrioma: a systematic review and meta-analysis of diagnostic test accuracy studies. J Obstet Gynaecol 2024;44(1):2311664.
- Xu Z, Li Y, Wang Y, Wan Y, Chen J. Transvaginal ultrasound and magnetic resonance imaging in detecting rectosigmoid deep infiltrating endometriosis: a comparative meta-analysis. Frontiers in Medicine 2025;12:1552185.
- 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, Klinghardt M, von Stockum S, Heinemann K. Time to Diagnose Endometriosis: Current Status, Challenges and Regional Characteristics — A Systematic Literature Review. BJOG 2025;132:118–130. doi:10.1111/1471-0528.17973.
- Thomassin-Naggara I, et al. ESUR consensus MRI for endometriosis: indications, reporting, and classifications. European Radiology 2025;35(11):7260–7268. doi:10.1007/s00330-025-11579-0.
- Thomassin-Naggara I, Dolciami M, Chamie LP, et al. ESUR consensus MRI for endometriosis: protocol, lexicon, and compartment-based analysis. European Radiology 2025;35(11):7272–7286. doi:10.1007/s00330-025-11611-3.
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