Suspected ovarian cancer or indeterminate adnexal mass

ACR AC Ovarian Cancer (2025); O-RADS MRI; ESUR ovarian guidelines

Ultrasound characterises the mass, MRI resolves what ultrasound leaves indeterminate, and CT stages disease that is already presumed malignant. Sending an adnexal mass straight to CT inverts that order and produces a study that cannot characterise what it finds.

Adnexal mass found clinically or on imaging, with or without a raised tumour marker, requiring characterisation or — where malignancy is already established — staging before surgery.

Referenced decision support — confirm against your local protocol.

Decision support, not a directive. Protocols and timings shown are typical published ones — your local protocol takes precedence, and the vetting radiologist decides.

The request in front of you

Everything is optional. Leave a field alone and the answer assumes nothing — the verdict updates as you go.

Study requested

What the referrer actually asked for. It is evidence of intent, not a constraint on the right answer.

Contrast as written

What the request form says, not what it should say.

Age

Pick a band, or type an exact age if it matters.

years

Pregnancy status

Renal risk factors

The question a vetter can actually answer from the request. An explicit “none known” is a real answer, and it removes checks rather than deferring them.

Previous contrast reaction

The pathway — tap anything already done

Marking a study complete moves the answer on. A patient arrives partway through a pathway far more often than at the start of one.

Accept as requested

Pelvic ultrasound — transabdominal and transvaginal

Ultrasound pelvis (transabdominal ± transvaginal)

What we'd amend, and why

The features that stratify risk — unilocular versus multilocular, solid components, papillary projections, acoustic shadowing, colour flow — are resolvable only at the spatial resolution a transvaginal probe achieves a few centimetres from the ovary. Most adnexal masses are benign and are confidently called so on this study alone, which is what stops the pathway before any cross-sectional imaging. Transabdominal imaging is added for a mass too large to fit the transvaginal field of view.

Nothing needs resolving before this goes ahead. Routine checks below are owned downstream.

How was this decided?

pathwaystandard — Adults — adnexal mass

Decision support only. Local protocol takes precedence.

Pathways

Big forks are separate pathways; the first whose conditions match is the one used.

Adults — adnexal mass

Matches your inputsDefault

Role	Study & protocol	Why this answers the question
First line	Ultrasound pelvis (transabdominal ± transvaginal) Pelvic ultrasound — transabdominal and transvaginal usually appropriate	The features that stratify risk — unilocular versus multilocular, solid components, papillary projections, acoustic shadowing, colour flow — are resolvable only at the spatial resolution a transvaginal probe achieves a few centimetres from the ovary. Most adnexal masses are benign and are confidently called so on this study alone, which is what stops the pathway before any cross-sectional imaging. Transabdominal imaging is added for a mass too large to fit the transvaginal field of view.
Second line	MRI Pelvis (Gynaecological) MRI Pelvis — general gynaecological	The specificity test. T1 imaging with and without fat suppression identifies the fat of a dermoid and the blood products of an endometrioma, which is the pair of diagnoses that most often looks worrying on ultrasound and is entirely benign. Diffusion and dynamic enhancement then characterise any solid component. Its documented effect is to reduce false-positive calls for malignancy and so avoid unnecessary or over-extensive surgery.
Second line	CT Abdomen and Pelvis CT Abdomen and Pelvis — Portal Venous Phase	The staging study once malignancy is presumed rather than the characterising one. Its value is mapping peritoneal disease — omental caking, subdiaphragmatic and small bowel mesenteric deposits, porta hepatis nodes — which is what determines whether complete cytoreduction is feasible or whether neoadjuvant chemotherapy is the better route.
Second line	CT Chest CT Chest — Contrast-Enhanced (Venous Phase)	Included in staging to identify pleural effusion with malignant cells and supradiaphragmatic nodal disease, both of which alter stage and the surgical plan.

Pitfalls

Sending an indeterminate adnexal mass straight to CT. It cannot resolve internal architecture and will report the lesion as indeterminate at the cost of a radiation dose.
Transabdominal ultrasound alone, which under-resolves the adnexa in most patients.
Omitting fat-saturated T1 on MRI, without which a dermoid cannot be separated from a haemorrhagic lesion.
Interpreting a raised CA125 in a premenopausal woman as evidence of malignancy.
Failing to look above the diaphragm and in the porta hepatis on the staging CT — the sites whose involvement most often changes the surgical decision.

Priors — what to pull first

A simple cyst documented as stable on previous scans needs no further work-up; retrieving that comparison is often the whole answer.
Menstrual timing matters for functional lesions — a repeat scan in the early proliferative phase resolves many apparently complex cysts.

What makes a good request

Transvaginal ultrasound is the characterising test: it resolves the internal architecture, papillary projections and vascularity that structured risk systems score, and transabdominal imaging alone is usually insufficient for the adnexa.
MRI is a problem-solving second test with higher specificity than ultrasound, which is precisely how it prevents unnecessary or over-extensive surgery in benign and borderline lesions.
Once malignancy is presumed, contrast-enhanced CT of the chest, abdomen and pelvis is the staging study, primarily to map peritoneal disease and to judge whether primary cytoreduction is achievable.
A raised CA125 in a premenopausal woman is unspecific — endometriosis, fibroids, pelvic inflammatory disease and even menstruation raise it — and does not by itself justify skipping characterisation.

Scoring this once it is done

The classification and risk tools this question ends in.

O-RADS Ultrasound (Adnexal Lesion Risk Stratification)O-RADS MRI Risk Stratification (Adnexal Lesion)IOTA Simple Rules (Adnexal Mass)ADNEX Model (IOTA)RMI (Risk of Malignancy Index)RECIST 1.1 Tumor Response

How these studies are acquired

Contrast, phases and timing for every study on the pathways above.

Pelvic ultrasound — transabdominal and transvaginal MRI Pelvis — general gynaecological CT Abdomen and Pelvis — Portal Venous Phase CT Chest — Contrast-Enhanced (Venous Phase)

Confirm locally

Timings, contrast volumes and rates above are typical published values. Your department's protocol, scanner and patient population decide the actual numbers.
Safety thresholds and premedication policy follow local policy where it differs from the cited guidance.

References

Implemented from the cited published sources. Educational and workflow support only; confirm against current guidelines and local policy before clinical use.