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Purpose and principlesIndications, selection and cautionsMethod and interpretationClinical next stepsRisks, monitoring and follow-upSpecial situationsCommon pitfallsQuestionsSources
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Educational draft · awaiting clinical reviewThe full textbook explains uncertainty but does not replace live national or local guidance, specialist advice, or current prescribing information.

Adnexal-mass ultrasound risk features

Obstetrics and gynaecology · UK scope · Sources checked 27 Aug 2026 · Clinical review pending

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Risk scoring follows emergency triage

Shock, peritonism, severe acute pain, vomiting, pregnancy-related symptoms or sepsis requires immediate assessment for torsion, rupture, haemorrhage, ectopic pregnancy or abscess rather than leisurely malignancy scoring.

Action: Stabilise physiology, obtain pregnancy status, involve acute gynaecology and arrange time-critical imaging or surgery; complete cancer-risk characterisation once the immediate threat has been addressed.

Purpose and principles

Describe adnexal masses with standard ultrasound morphology, apply validated benign and malignant features correctly, and direct indeterminate or suspicious findings to the appropriate specialist and cancer pathway.

Ultrasound is a structured probability assessment rather than a hunt for one decisive sign. Establish whether the lesion is ovarian, tubal, uterine, peritoneal or extra-gynaecological, then describe rather than prematurely name it. A report such as 'complex cyst' is insufficient because the clinician cannot reconstruct risk. Standard terms allow comparison over time, use of IOTA rules and rational selection of benign gynaecology, specialist imaging or oncology care.

Use transvaginal scanning when acceptable and suitable because proximity gives detailed assessment of the wall and internal architecture. Add a transabdominal scan for a lesion above the pelvic brim, very large multilocular masses, ascites and upper abdominal disease. Scan both ovaries and the uterus, look for hydrosalpinges and peritoneal abnormalities, and document whether the whole lesion was visible. Incomplete visualisation is uncertainty, not a benign feature.

A simple cyst is anechoic, unilocular, thin and smooth walled, lacks solid tissue and internal flow, and shows posterior enhancement. Internal echoes need classification: fine reticular strands and a retracting avascular clot suggest haemorrhage; homogeneous low-level echoes suggest endometrioma; bright lines, shadowing or fat suggest dermoid. Septa, papillae and nodules should be measured separately. True solid tissue usually shows vascularity, while a clot should not, although technical settings can limit Doppler sensitivity.

Indications, selection and cautions

Unequivocally simple

A completely seen unilocular anechoic cyst with a smooth thin wall and no solid tissue or internal flow supports very low morphological risk.

Papillary risk

A vascular wall projection protruding into the cyst is a papillary structure; four or more constitutes an IOTA malignant feature.

Irregular solid risk

Irregular vascular solid tissue is more concerning than an avascular retracting clot and should trigger specialist cancer-pathway assessment.

Benign shadowing

Acoustic shadowing and small solid components under 7 mm are IOTA benign features when no malignant rule is present.

Indeterminate rule set

Coexisting benign and malignant features, or absence of both, means the simple rules cannot classify the lesion and expert assessment is required.

Red flags requiring action

  • An irregular solid tumour, ascites, at least four papillary structures, an irregular multilocular-solid mass of 100 mm or more, or very strong blood flow is an IOTA malignant feature requiring oncology referral.
  • Preserved Doppler flow within an ovary does not exclude torsion, so a reassuring colour signal must not delay senior surgical assessment when the clinical presentation is convincing.
  • A positive pregnancy test with pain, bleeding, free fluid or an empty uterus requires an early-pregnancy pathway before an adnexal lesion is treated as incidental.

Method and interpretation

  1. 01
    Transvaginal ultrasoundFirst step
    Why
    Provide detailed morphology of both adnexa, uterus and pelvic peritoneal spaces.
    Interpretation and limitations
    Use standard descriptors and IOTA features; a lesion that is not fully visualised cannot be confidently assigned a low-risk category.
  2. 02
    Colour Doppler mapping
    Why
    Distinguish vascular tissue from likely clot and assign a qualitative colour score within the morphological assessment.
    Interpretation and limitations
    Very strong flow is an IOTA malignant feature, but flow indices do not diagnose cancer and preserved ovarian perfusion cannot rule out torsion.
  3. 03
    Transabdominal ultrasound
    Why
    Survey a large mass, upper extent, ascites and anatomy outside the transvaginal field.
    Interpretation and limitations
    Combine it with transvaginal detail where possible; a large lesion should not be called simple when its entire wall has not been examined.
  4. 04
    Serum CA125
    Why
    Contribute to epithelial ovarian-cancer triage and RMI calculation when clinical or imaging suspicion exists.
    Interpretation and limitations
    A raised value is nonspecific and a normal value does not exclude cancer; do not order it routinely for every simple premenopausal cyst.

Clinical next steps

01Structured scanDescribe before classifyingFirst stepA pelvic scan identifies a possible ovarian or adnexal lesion.+
  1. 1Establish organ of origin and document both ovaries, lesion dimensions, wall, locules, contents, solid tissue, papillae, shadows, vascularity and free fluid.
  2. 2Add transabdominal views when the mass or extra-ovarian anatomy lies beyond the transvaginal field and state any limitation explicitly.
  3. 3Apply a recognised pattern or validated rule set only after the necessary features have been captured accurately.
02IOTA resultUse rules without vote countingAll five benign and five malignant simple-rule features have been assessed.+
  1. 1Classify benign when at least one benign feature and no malignant feature is present, and malignant for the inverse combination.
  2. 2Call the mass indeterminate when both feature groups occur or neither group occurs;

Risks, monitoring and follow-up

  • Store representative images and measurements so change in morphology can be compared directly rather than inferred from report wording.
  • Ensure an indeterminate scan has a booked expert review or MRI plan and is not left as an unactioned recommendation.
  • For surveillance, compare locules, wall, papillary structures, solid tissue and ascites as well as maximum diameter.
  • Track every tumour marker to the intended pathway and document which RMI threshold or cancer-network rule is being applied.
  • Escalate new acute pain, systemic illness or cancer symptoms even when the preceding scan carried a benign label.

Special situations

Origin comes before ovarian risk

A convincing hydrosalpinx or pedunculated fibroid follows a different pathway, making anatomical localisation the first interpretive task.

Four papillae is a rule boundary

At least four papillary structures is the IOTA malignant feature; fewer projections still require careful expert interpretation.

RMI cutoffs differ deliberately

NICE uses 250 for suspected-cancer MDT referral while RCOG's postmenopausal cyst algorithm uses 200, so name the governing pathway.

Normal flow is not detorsion

Dual arterial supply and intermittent twisting allow Doppler flow to persist despite clinically important adnexal torsion.

No rule is not benign

If neither benign nor malignant IOTA features are present, the mass is inconclusive rather than automatically low risk.

Common pitfalls

  1. 01

    Reporting a complex cyst without standard features, leaving clinicians unable to reproduce the risk assessment.

  2. 02

    Calling a large lesion simple when part of its wall lies outside the ultrasound field.

  3. 03

    Using CA125 as a screening or exclusion test instead of integrating age, morphology and symptoms.

  4. 04

    Misapplying IOTA simple rules by counting more benign than malignant findings when any overlap is indeterminate.

  5. 05

    Combining the NICE RMI threshold of 250 and RCOG threshold of 200 without stating which referral pathway governs care.

  6. 06

    Allowing preserved Doppler flow to postpone diagnostic laparoscopy in a high-probability torsion presentation.

Practice

Two practice questions

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Obstetrics and gynaecologyOriginal SBA

Applying the IOTA simple rules

Ultrasound shows an 82 mm adnexal mass with acoustic shadows and a 5 mm solid component, but ascites is also present. How should the IOTA simple rules classify it?

Choose one answer, then submit
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Sources and review status4 sources · checked 27 Aug 2026 · clinical review pending+
Sources

Sources and review status

National guidance is shown before implementation-dependent detail. Apply principles in context and verify current guidance when a decision affects care. Source check completed 27 Aug 2026; clinical approval remains outstanding.

  • RCOG Green-top Guideline 62: Ovarian Masses in Premenopausal Women
  • RCOG Green-top Guideline 34: Ovarian Cysts in Postmenopausal Women
  • NICE CG122: Ovarian cancer recognition and initial management
  • NHSGGC: Ovarian masses in premenopausal adults

Editorial contact: Doctor’s Passport editorial team. Source-check date is separate from clinical approval. Report a content problem · Content changes

Authoring stateComplete draftClinical stateAwaiting reviewJurisdictionUnited Kingdom

The IOTA simple rules use five benign and five malignant features. Benign rules are unilocular morphology, a solid component under 7 mm, acoustic shadows, a smooth multilocular lesion under 100 mm and absent flow. Malignant rules are irregular solid tissue, ascites, four or more papillary projections, an irregular multilocular-solid lesion at least 100 mm and very strong flow. The rule set does not work by counting which side has more features: any feature from both sides makes the result inconclusive.

An indeterminate result should lead to expert gynaecological ultrasound rather than arbitrary averaging. Specialist subjective pattern recognition can outperform basic scoring when performed by experienced operators. MRI is a second-line problem-solving examination when ultrasound remains inconclusive, particularly for fat, blood products, very large lesions or deep endometriosis. CT is not the primary characterisation test; when cancer is suspected, it assesses extent and supports oncology planning after ultrasound and markers.

Tumour markers are selected by age and suspected biology. In secondary care, NICE recommends CA125 for suspected ovarian cancer and adds AFP and beta-hCG for patients under 40; UK premenopausal guidance also includes LDH for complex masses. CA125 alone has poor specificity before menopause because endometriosis, fibroids, adenomyosis and pelvic infection can raise it. In postmenopausal cyst assessment it contributes to RMI, but a normal result cannot exclude malignancy.

RMI I is U × M × CA125. The ultrasound score gives one point each for multilocularity, solid areas, metastases, ascites and bilateral lesions; U is 0 for no feature, 1 for one feature and 3 for two to five. Menopausal score M is 1 before menopause and 3 after menopause. NICE CG122 refers at RMI I 250 or greater to the specialist MDT; RCOG Green-top 34 uses 200 as its postmenopausal cyst threshold. Networks must use a declared pathway rather than silently mixing cutoffs.

The report should end with an actionable assessment. State whether morphology is clearly simple, a recognised benign pattern, IOTA benign, IOTA malignant or indeterminate; record any acute feature and recommend the appropriate clinical route. The sonographer does not decide surgery in isolation. Symptoms, pregnancy, menopausal status, family history, serial change, tumour markers, operative fitness and patient priorities complete the decision.

Key points

  • Confirm that a reported adnexal mass is ovarian: paraovarian cyst, hydrosalpinx, pedunculated fibroid, pelvic kidney, bowel or an inflammatory collection can imitate ovarian disease.
  • Transvaginal ultrasound provides the highest-resolution initial morphological assessment; add transabdominal views for a large lesion or disease beyond its field of view.
  • Document maximum dimensions, laterality, unilocular or multilocular architecture, wall and septal regularity, internal echoes, acoustic shadows, papillary projections, solid tissue, colour score, ascites and peritoneal findings.
  • IOTA benign features are a unilocular cyst, solid components smaller than 7 mm, acoustic shadows, a smooth multilocular tumour smaller than 100 mm and no detectable blood flow.
  • IOTA malignant features are an irregular solid tumour, ascites, at least four papillary structures, an irregular multilocular-solid tumour at least 100 mm and very strong blood flow.
  • When one or more malignant features occur without a benign feature, classify as malignant; benign features without a malignant feature classify as benign; both sets or neither set is indeterminate and needs expert ultrasound.
  • CA125 is contextual, not diagnostic. It is nonspecific before menopause and can be normal in early epithelial cancer; do not use it to overrule morphology.
  • RMI I equals ultrasound score multiplied by menopausal score and CA125. NICE uses 250 for specialist MDT referral, whereas RCOG's postmenopausal cyst pathway uses 200; follow the applicable national or local cancer pathway deliberately.
  • Postmenopausal symptoms, complexity, bilaterality, ascites or rising size carry greater malignant significance than an isolated normal CA125.
  • A complex mass in a patient under 40 may be a germ-cell tumour and needs AFP, beta-hCG and LDH assessment rather than an epithelial-marker-only approach.
  • 05
    AFP, beta-hCG and LDH
    Why
    Assess possible malignant germ-cell tumour in a patient under 40 with a complex ovarian mass.
    Interpretation and limitations
    Marker elevation can guide specialist care, but normal concentrations do not neutralise suspicious morphology or remove the need for histology.
  • 06
    Pelvic MRI
    Why
    Characterise an ultrasound-indeterminate mass, blood or fat content, very large lesions and deep pelvic relationships.
    Interpretation and limitations
    MRI refines probability and operative mapping but is not routine after a confidently benign ultrasound and does not replace oncology referral for malignant features.
    • do not
    subtract one rule from another.
  • 3Refer malignant-pattern masses to gynaecological oncology and indeterminate masses for specialist ultrasound or equivalent expert review.
    • 03Marker integrationMatch assays to biology and ageClinical or ultrasound findings make neoplasia a credible possibility.+
    1. 1Measure CA125 for suspected epithelial ovarian cancer and add AFP, beta-hCG and LDH for a complex mass under age 40.
    2. 2Calculate RMI I when the pathway calls for it, recording ultrasound points, menopausal multiplier and actual CA125 rather than only the product.
    3. 3Use the declared referral threshold for that pathway and never downgrade suspicious imaging solely because markers are normal.
    04Acute overlaySeparate morphology from immediate dangerThe patient has severe pain, vomiting, instability, fever or a positive pregnancy test.+
    1. 1Activate the torsion, haemorrhage, sepsis or early-pregnancy pathway while performing focused ultrasound that answers the urgent question.
    2. 2Communicate that Doppler flow cannot exclude torsion and that free fluid must be interpreted with physiology and haemoglobin trend.
    3. 3Return to formal mass characterisation after stabilisation so the acute event does not erase longer-term cancer and follow-up decisions.