Characterisation of an incidental liver lesion (non-cirrhotic liver)

ACR Incidental Findings Committee liver white paper (2017); NICE DG5

Most of these lesions are benign and the job is to say so confidently and stop. The pre-test probability, and therefore the pathway, is set by whether the patient has a known malignancy or chronic liver disease — which is why this card is separate from the cirrhosis card even though the modalities overlap.

A focal liver lesion found on a study performed for another reason, in a patient with no cirrhosis and no known primary tumour.

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

eGFR

Only needed where the pathway itself changes with renal function — not as a routine gate.

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

MRI Liver — multiphase with extracellular gadolinium

MRI Liver

What we'd amend, and why

Characterisation is a tissue-property problem before it is an enhancement problem, and MRI measures the properties directly. Marked, near-fluid T2 prolongation with peripheral nodular discontinuous enhancement that fills in progressively identifies a haemangioma outright; microscopic fat shown by signal loss on opposed-phase imaging points to an adenoma or a fat-containing lesion; restricted diffusion raises concern for metastasis. No CT protocol can supply the intrinsic contrast that makes these distinctions, which is why MRI ends the pathway more often than any other test.

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

How was this decided?

pathwayadult — Adults without cirrhosis
rulerule-mr-device-screening — MR safety screening for implants and foreign bodies; checked by Radiographer at the scanner
rulerule-contrast-reaction-premed — Prior contrast reaction and elective premedication; checked by Nurse before the scan
rulerule-gadolinium-renal — Kidney function and gadolinium-based contrast; checked by Radiographer at the scanner
rulerule-pregnancy-gadolinium — Gadolinium in known or possible pregnancy; checked by Radiographer at the scanner
rulerule-iv-access — Intravenous access adequate for the planned injection; checked by Radiographer at the scanner

Decision support only. Local protocol takes precedence.

Handled at the scanner(2)nothing for you to do

Settled and owned downstream. Each returns to a radiologist only on the stated trigger.

MR safety screening for implants and foreign bodies
Complete the MR safety questionnaire, verify implant labelling and its stated conditions of use against this scanner and this protocol, and ensure no ferromagnetic object enters Zone IV.
Radiographer at the scannerBefore the scan
Flags back if: An implant or retained foreign body that is MR Unsafe, unlabelled, or cannot be identified; or an MR Conditional device whose stated conditions this scanner or the requested protocol cannot satisfy; or a credible unexcluded intraocular metallic foreign body history.
Intravenous access adequate for the planned injection
Site and test a cannula that supports the protocol flow rate, preferring an antecubital or large forearm vein, and observe the injection for extravasation. A 20-gauge or larger cannula is preferred for flow rates of 3 mL/s or more.
Radiographer at the scannerAt the scanner
Flags back if: No cannula can be sited that supports the protocol flow rate — for example only a 22-gauge hand or foot cannula for a CT angiogram needing 4–5 mL/s; or the only available access is a central line or port that is not labelled power-injectable; or an extravasation occurs.

Worth asking the referrer (1)

None of these hold the request up. They sharpen the protocol or the plan that follows.

Is there a known primary malignancy or chronic liver disease?
It moves the lesion between two entirely different probability worlds, and therefore between reassurance and staging.

Pathways

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

Adults with severe renal impairment or on dialysis

Role	Study & protocol	Why this answers the question
First line	Ultrasound abdomen Contrast-enhanced ultrasound (CEUS) — focal liver lesion characterisation usually appropriate	A microbubble agent stays in the blood pool, is cleared by exhalation and the reticuloendothelial system, and is not filtered by the kidney — so there is no nephrotoxicity, no eGFR requirement and nothing to defer before the injection. That removes the constraint entirely rather than working around it. What is gained on top is temporal: enhancement is watched continuously from about ten seconds rather than sampled at two or three discrete acquisitions, so peripheral nodular centripetal fill-in of a haemangioma is seen happening, and the timing and degree of late-phase wash-out that separates a malignant lesion from a benign hypervascular one is observed rather than inferred between timepoints. This is a targeted characterisation study for one lesion in one acoustic window and it does not survey the liver, so it fits precisely the common situation it is being used for: a single indeterminate lesion already found on ultrasound in a patient in whom a multiphase CT or MRI is unattractive.
Second line	MRI Liver MRI Liver — multiphase with extracellular gadolinium	Not excluded, and this must not be read as a prohibition: with a group II macrocyclic agent the risk of nephrogenic systemic fibrosis below an eGFR of 30 is vanishingly small, and much of the characterisation here — T2 signal, opposed-phase signal loss, diffusion — is unenhanced anyway. MRI remains the study when there are several lesions, when the lesion cannot be seen or held in an acoustic window, or when the question is one contrast-enhanced ultrasound cannot answer, such as hepatobiliary-phase uptake distinguishing focal nodular hyperplasia from adenoma. It is second here only because a single ultrasound-visible lesion is answered sooner, cheaper and with no renal exposure at all.

One bolus interrogates one lesion in one window. Where several lesions need characterising, or where the liver has to be surveyed, this is the wrong study and MRI is the right one.
A microbubble agent is not nephrotoxic, but it is still a contrast agent: rare serious hypersensitivity reactions are described, so the study is performed with intravenous access and resuscitation facilities available.

Adults without cirrhosis

Matches your inputsDefault

Role	Study & protocol	Why this answers the question
First line	MRI Liver MRI Liver — multiphase with extracellular gadolinium usually appropriate	Characterisation is a tissue-property problem before it is an enhancement problem, and MRI measures the properties directly. Marked, near-fluid T2 prolongation with peripheral nodular discontinuous enhancement that fills in progressively identifies a haemangioma outright; microscopic fat shown by signal loss on opposed-phase imaging points to an adenoma or a fat-containing lesion; restricted diffusion raises concern for metastasis. No CT protocol can supply the intrinsic contrast that makes these distinctions, which is why MRI ends the pathway more often than any other test.
Problem solving	MRI Liver MRI Liver — hepatobiliary contrast agent	The specific question a hepatobiliary agent answers is focal nodular hyperplasia versus adenoma. Focal nodular hyperplasia contains functioning hepatocytes but disordered bile ductules, so it takes the agent up and retains it in the hepatobiliary phase, whereas most adenomas do not — a distinction that matters because adenomas carry bleeding and malignant transformation risk and may be resected. The same agent improves detection of small metastases before hepatic resection.
Reasonable alternative	Ultrasound abdomen Ultrasound abdomen — full survey	For a lesion that is probably a simple cyst, ultrasound settles it in minutes: anechoic contents, an imperceptible wall and posterior acoustic enhancement are diagnostic, and no further imaging is warranted. It is the cheapest possible way to end a pathway that would otherwise consume an MRI slot.
Problem solving	Ultrasound abdomen Contrast-enhanced ultrasound (CEUS) — focal liver lesion characterisation	Where the greyscale study found something it could not call, the microbubble study is the natural continuation and often needs no second appointment: the lesion is already located and the operator is already at the machine. It earns its place on two specific questions. The first is the haemangioma — peripheral nodular discontinuous enhancement filling in centripetally, watched in real time rather than sampled between acquisitions, which is a more convincing observation than two static timepoints. The second is a lesion that stayed indeterminate on CT or MRI, where continuous observation of wash-in and the timing of late wash-out adds information that discrete phases cannot. Its limits are honest ones: one bolus, one lesion, one acoustic window, and a deep lesion in a steatotic, cirrhotic or large abdomen may simply not be reachable — the same limitations that made the greyscale study difficult apply unchanged. Wash-out kinetics are also not transposable: microbubbles remain intravascular, so CT and MRI wash-out thresholds must not be read across.
Reasonable alternative	CT Liver — Multiphase CT Liver — Triphasic (Unenhanced, Late Arterial, Portal Venous)	Where MRI is contraindicated or unavailable, an unenhanced, late arterial and portal venous CT still separates hypervascular from hypovascular lesions and shows the peripheral nodular enhancement pattern. It is used deliberately when washout assessment is not the question, since the delayed acquisition has been dropped.

Pitfalls

Escalating a lesion that has been unchanged for years because it has just been noticed on a new modality.
Applying hepatocellular carcinoma criteria to a non-cirrhotic liver, which generates false positives from benign hypervascular lesions.
Ordering a portal-venous CT for characterisation. In that single phase a haemangioma, a metastasis and focal nodular hyperplasia can look alike.
Missing that the patient does have a known primary, which converts a reassurance question into a staging question.
Reporting a lesion as too small to characterise without saying what the recommended action is; that phrase generates the follow-up scan without directing it.
Working up a sub-centimetre lesion in a patient with no cirrhosis, no known primary and no risk factors. The white paper answer for that lesion is usually no further imaging at all, and an MRI ordered anyway converts a benign non-finding into a surveillance schedule the patient will never be released from.
Treating renal impairment as the end of characterisation. Contrast-enhanced ultrasound has no renal exposure and needs no eGFR, and unenhanced MRI still characterises a great deal — cancelling the pathway is the wrong response to a flagged creatinine.
Booking contrast-enhanced ultrasound to survey a liver. It interrogates one lesion per bolus in one acoustic window and cannot look for others during the arterial phase; a multifocal question is an MRI question.
Applying CT or MRI wash-out thresholds to microbubble kinetics. The agent stays intravascular, so late-phase wash-out is a different observation and reading it across generates false calls in both directions.

Priors — what to pull first

Look for the lesion on any older imaging, including studies done for unrelated reasons. Stability over years is the strongest single argument for benignity and can end the pathway without any new scan.
Check whether a previous ultrasound already characterised it as a cyst.

What makes a good request

A lesion under about a centimetre in a patient at no particular risk is very unlikely to be significant, and chasing it with repeated imaging causes more harm than it prevents.
The single most useful thing a referrer can state is whether there is a known or suspected malignancy, because it changes the entire interpretation.
Where the lesion was found on ultrasound and there is one of it, contrast-enhanced ultrasound can characterise it in the same appointment on the same machine, using a microbubble agent that is a pure blood-pool tracer — not filtered by the kidney, not nephrotoxic, and requiring no eGFR before it is given. That is a genuine option rather than a consolation prize, and it is the option that matters most when iodinated contrast or gadolinium is being avoided.

Scoring this once it is done

The classification and risk tools this question ends in.

FIB-4 (Fibrosis-4) Index Hepatic Steatosis (CT & MRI)LI-RADS v2018 (CT/MRI)RECIST 1.1 Tumor Response Liver Volume (CT/MRI/US) + Expected Volume

How these studies are acquired

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

Contrast-enhanced ultrasound (CEUS) — focal liver lesion characterisation MRI Liver — multiphase with extracellular gadolinium MRI Liver — hepatobiliary contrast agent Ultrasound abdomen — full survey CT Liver — Triphasic (Unenhanced, Late Arterial, Portal Venous)

Confirm locally

MRI Liver — multiphase with extracellular gadolinium: timings are typical — confirm against local protocol.
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.