Liver assessment in a hypervascular primary

Hepatic arterial phase evidence base; LI-RADS technical requirements; NCCN sarcoma/melanoma staging

The question is the LIVER in a primary whose hepatic deposits are hypervascular — neuroendocrine above all, and renal cell. A portal-venous-only CT is the wrong study for that question and reports as a false negative, because the window in which the lesion is visible closes before the standard staging phase opens. The card exists to teach why the late arterial acquisition is not optional where it is needed, and equally why it is not a licence to add two abdominal passes to every staging CT.

Known or suspected hypervascular primary requiring liver assessment: baseline staging, restaging, or a rising tumour marker with a previously negative portal-venous CT.

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

CT Liver — Triphasic (Unenhanced, Late Arterial, Portal Venous)

CT Liver — Multiphase

What we'd amend, and why

The late arterial acquisition is the only phase in which a hypervascular deposit is brighter than the liver around it. Published CT series show additional metastases found only on the arterial phase in a meaningful minority of patients, and lesions visible on no other phase in a small but real subset. The portal venous acquisition is still acquired, because it stages the rest of the abdomen and pelvis and because some deposits show washout rather than persistent enhancement; the unenhanced series provides the baseline that separates true enhancement from intrinsic density such as calcification or haemorrhage. Three phases here are not defensive imaging — each answers a different question.

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

How was this decided?

pathwaystandard — Adults — hypervascular primary
rulerule-contrast-reaction-premed — Prior contrast reaction and elective premedication; checked by Nurse before the scan
rulerule-metformin — Metformin and iodinated contrast; checked by Radiographer at the scanner
rulerule-paeds-dose — Child-sized technique and contrast dose; checked by Radiographer at the scanner
rulerule-pregnancy-ionising — Pregnancy status before an ionising exposure; checked by Radiographer at the scanner
rulerule-renal-iodinated — Kidney function and intravenous iodinated contrast; 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(4)nothing for you to do

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

Metformin and iodinated contrast
Confirm whether the patient takes metformin or a metformin-containing combination, and if so whether ACR Category II applies (eGFR below 30, known or suspected AKI, or an arterial catheter study likely to cause renal embolisation). If Category I — that is, no AKI and eGFR at or above 30 — no action of any kind is needed.
Radiographer at the scannerAt the scanner
Flags back if: The patient takes metformin AND meets ACR Category II — eGFR below 30 mL/min/1.73 m2, known or suspected acute kidney injury, or an arterial catheter procedure with likely renal arterial embolisation. Metformin plus a normal or mildly reduced eGFR is explicitly NOT a flag-back: there is no need to stop metformin before or after intravenous iodinated contrast in Category I patients, and no need to re-check creatinine afterwards.
Child-sized technique and contrast dose
Confirm that a size- or weight-based protocol is selected — child-sized kV and mAs against size-based diagnostic reference ranges — and that contrast volume is calculated by weight rather than taken from an adult default. Weight-based iodinated contrast volumes of roughly 1.5–2.0 mL/kg are widely used in paediatric CT.
Radiographer at the scannerAt the scanner
Flags back if: No paediatric or size-based protocol exists on the scanner for the requested examination, or the requested coverage or number of phases exceeds what the clinical question needs — for example a multiphase study where a single phase answers it, or whole-body coverage for a focal question.
Pregnancy status before an ionising exposure
Make the pregnancy enquiry immediately before the exposure and record the answer. In the UK this is a statutory operator duty discharged at the time of exposure under the employer’s written procedures required by IR(ME)R 2017 — it is not something the vetting radiologist can perform or pre-empt, and a request is complete without it.
Radiographer at the scannerAt the scanner
Flags back if: The patient states that she is, or may be, pregnant AND the uterus is in or near the primary beam. The exposure is then paused for re-justification by the IR(ME)R practitioner before it proceeds.
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.

Which primary, and is it known to be hypervascular?
It is the entire basis for adding the arterial acquisition; a hypovascular primary should be staged on the standard single-phase protocol instead.

Pathways

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

Adults — hypervascular primary

Matches your inputsDefault

Role	Study & protocol	Why this answers the question
First line	CT Liver — Multiphase CT Liver — Triphasic (Unenhanced, Late Arterial, Portal Venous) usually appropriate	The late arterial acquisition is the only phase in which a hypervascular deposit is brighter than the liver around it. Published CT series show additional metastases found only on the arterial phase in a meaningful minority of patients, and lesions visible on no other phase in a small but real subset. The portal venous acquisition is still acquired, because it stages the rest of the abdomen and pelvis and because some deposits show washout rather than persistent enhancement; the unenhanced series provides the baseline that separates true enhancement from intrinsic density such as calcification or haemorrhage. Three phases here are not defensive imaging — each answers a different question.
Problem solving	MRI Liver MRI Liver — multiphase with extracellular gadolinium	More sensitive than CT for small hypervascular deposits because diffusion-weighted imaging and the T2 signature add detection independent of the enhancement window, which is unforgiving on CT. The right escalation when the CT is negative and the biochemistry is not, and the right first study when the liver is the sole determinant of resectability.
First line	CT Chest CT Chest — Contrast-Enhanced (Venous Phase)	Thoracic staging is unchanged by the hypervascular question and is acquired in the venous phase as usual. Only the liver acquisition needs the arterial timing.

Pitfalls

Accepting a plain portal-venous CT abdomen for a neuroendocrine, renal or melanoma primary. This is the classic false negative of oncological CT and the single commonest reason a hypervascular liver burden is discovered late.
Scanning the arterial phase too early. An early arterial acquisition opacifies arteries but leaves the parenchyma and the lesion both unenhanced; the phase needed is late arterial, when the portal vein is opacified but the hepatic veins are not.
Reading transient perfusion abnormality on the arterial phase as metastatic disease. Anything seen on the arterial phase alone, with no correlate on the unenhanced or venous series and no mass effect, deserves scepticism.
Assuming every neuroendocrine deposit is hypervascular. A minority, particularly higher-grade tumours, are hypovascular and are seen best on the venous series — which is why the venous phase stays in the protocol.
Dropping the unenhanced series to save dose, then being unable to tell a calcified treated deposit from an arterially enhancing live one.
Applying this card as a rule about primaries rather than about a question. The arterial acquisition earns its dose when the liver is the determinant of management; bolting it onto a routine staging CT for a sarcoma, a melanoma or a thyroid primary is two extra abdominal exposures with no yield, and in the thyroid case an iodine load that delays radioiodine therapy.

Priors — what to pull first

Check the phase used on every prior CT before calling disease new. A deposit that "appeared" between two scans has often simply had an arterial phase acquired for the first time.
Where a previous study was single-phase, say so explicitly in the report so that the comparison is not read as progression.

What makes a good request

Hypervascular metastases are supplied almost entirely by the hepatic artery, so they peak while the liver parenchyma — supplied mostly by the portal vein — is still barely enhanced. By the portal venous phase the parenchyma has caught up and the lesion becomes isodense. The window in which the lesion is visible closes before the standard staging phase opens.
A previous "normal" portal-venous staging CT in a patient with a neuroendocrine primary and rising chromogranin is not reassurance; it is an inadequate protocol, and repeating it will produce the same answer.
Somatostatin receptor PET-CT is the functional counterpart for neuroendocrine primaries and detects disease that is occult on CT. It is not represented in this vocabulary and must be requested outside this pathway.
The list of primaries whose hepatic deposits CAN be hypervascular is not the same as the list whose ROUTINE STAGING requires a multiphase liver, and conflating the two is how this card gets misused. Neuroendocrine tumours and renal cell carcinoma are the two where the arterial acquisition is load-bearing at baseline. Soft tissue sarcoma stages to the chest, because lung is the metastatic site, and routing it to a triphasic liver adds two abdominal passes with no yield. Melanoma is staged with FDG PET-CT or single-phase CT. Differentiated thyroid carcinoma is staged with neck ultrasound and radioiodine imaging, and an iodine load there delays radioiodine therapy for weeks — so the multiphase CT is not merely unnecessary in that group, it is harmful. This card is for the patient in whom the liver is the determinant of management.

Scoring this once it is done

The classification and risk tools this question ends in.

RECIST 1.1 Tumor Response Liver Volume (CT/MRI/US) + Expected Volume eGFR (CKD-EPI 2021 Creatinine)Lutathera Dose Modification for Adverse Reactions Bosniak Classification v2019 (Cystic Renal Mass, CT/MRI)Clear Cell Likelihood Score (ccLS) v2.0 — Renal Mass mpMRI RENAL Nephrometry Score

How these studies are acquired

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

CT Liver — Triphasic (Unenhanced, Late Arterial, Portal Venous)MRI Liver — multiphase with extracellular gadolinium CT Chest — Contrast-Enhanced (Venous Phase)

Confirm locally

CT Liver — Triphasic (Unenhanced, Late Arterial, Portal Venous): 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.