Staging or completion CT in a known solid tumour

ACR AC oncological staging topics; RECIST 1.1

The staging request is rarely wrong about the STUDY and frequently wrong about the PHASE, and which phase is right is a property of the primary. A single portal-venous acquisition stages most solid tumours and adding an arterial phase to those is dose and cost for no yield. A late arterial acquisition is not optional for a hypervascular primary, and renal and pancreatic primaries each need their own timing. Saying that no arterial phase is required is as much of an answer as adding one.

Newly diagnosed or already known malignancy requiring assessment of nodal, visceral and distant disease — either as a complete baseline before treatment is decided, or as the completion of a staging assessment that has already been started elsewhere.

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

Known cancer

Back pain in a cancer patient is a different question, and staging phase changes which contrast phases are needed.

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 Abdomen and Pelvis — Portal Venous Phase

CT Abdomen and Pelvis

What we'd amend, and why

A single portal venous acquisition is the whole answer here, and saying so is the point of this pathway. At roughly 60-80 seconds the liver parenchyma reaches peak enhancement from portal inflow, and the ordinary hypovascular metastasis — colorectal, lung, breast, lymphoma, head and neck, most gynaecological — becomes conspicuous precisely because the BACKGROUND has brightened around it, not because the lesion itself enhances. The same acquisition gives enhancing bowel wall, opacified veins for tumour thrombus, and enough nodal-to-vessel discrimination to stage the retroperitoneum. For these primaries a late arterial phase is not a safety margin: it is a second exposure and a second contrast load that adds no staging information, and it adds a series on which transient hepatic perfusion abnormality is routinely over-called as metastatic disease.

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

How was this decided?

pathwaystandard — Adults — standard staging, portal venous alone
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 (2)

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

What is the primary tumour, and is the histology known?
It determines coverage, which phase is required, and whether PET-CT should displace or supplement CT. It is the single fact that decides whether an arterial acquisition is mandatory or is pure dose.
What imaging has already been performed for this episode, and with what protocol?
A completion request is a request to join a pathway partway through. Knowing the abdomen is already done moves the answer on to the thorax instead of repeating an acquisition that is sitting on the archive — and knowing what PHASE that abdominal study used decides whether it actually answered the abdominal question.

Pathways

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

Pancreatic ductal adenocarcinoma — pancreatic-phase staging

Role	Study & protocol	Why this answers the question
First line	CT Pancreas Protocol CT Pancreas — Dual Phase with Water Distension usually appropriate	A routine portal-venous abdomen is the wrong protocol for this primary, not merely a thinner version of the right one. Pancreatic ductal adenocarcinoma is defined on CT by its attenuation difference from the parenchyma around it, and that difference peaks in the pancreatic parenchymal phase at roughly 40-45 seconds; by 70 seconds a substantial minority of tumours are isoattenuating and simply not visible. The same early acquisition is what grades contact with the coeliac axis, superior mesenteric artery and hepatic artery, which is the whole of the resectability decision. The portal venous acquisition is still taken, because that is where hepatic metastases and venous involvement are seen — so this is a dual-phase study in which each phase answers a different question, not a defensive extra pass. Neutral water distension replaces positive oral contrast, which otherwise obscures the duodenal wall and streaks the pancreatic head.
First line	CT Chest CT Chest — Contrast-Enhanced (Venous Phase)	Thoracic staging is unaffected by the pancreatic timing question and is acquired in the venous phase as usual. The pancreatic phase is a liver-and-pancreas acquisition; extending it to the thorax buys nothing, because pulmonary metastases are found on lung windows and mediastinal nodes need venous opacification to be separated from vessels.

Detection and resectability of a pancreatic mass in detail belong to the suspected-pancreatic-mass card; this fork exists so that a request written as a generic staging CT in a patient with a known pancreatic primary still lands on the right protocol.
Coverage: the pancreatic-phase acquisition is upper abdomen only. The portal-venous acquisition must extend through the pelvis when this is the staging baseline.

Renal cell carcinoma — corticomedullary and nephrographic staging

Role	Study & protocol	Why this answers the question
First line	CT Urogram CT Urogram — Conventional Three Phase usually appropriate	Two separate arguments converge on a multiphase renal acquisition here. The primary needs an unenhanced baseline plus a corticomedullary acquisition — the phase in which the tumour is judged against brightly enhancing cortex, in which renal vein and caval tumour thrombus is delineated, and on which clear cell likelihood is assessed — followed by a nephrographic acquisition at roughly 90-100 seconds, because slowly enhancing papillary tumours are called non-enhancing when measured on early or portal-venous images alone. Separately, renal cell metastases are hypervascular, so a portal-venous-only study also under-detects hepatic and pancreatic deposits. A single 70-second abdomen answers neither question properly.
First line	CT Chest CT Chest — Contrast-Enhanced (Venous Phase)	The lung is the commonest site of distant spread in renal cell carcinoma and the thorax is staged in the venous phase as usual. The arterial argument in this disease is an abdominal one; it does not transfer to the chest.
Problem solving	CT Liver — Multiphase CT Liver — Triphasic (Unenhanced, Late Arterial, Portal Venous)	Where the liver is the determinant of management and the urographic study has not resolved it, the dedicated triphasic liver acquisition is the escalation, on exactly the reasoning set out in the hypervascular-primary-liver-staging card: renal cell deposits peak while the parenchyma is still dark. Adding it routinely on top of a three-phase urogram would be a large and rarely justified dose.

GAP, stated plainly: this vocabulary has no dedicated multiphase renal mass protocol — unenhanced, corticomedullary and nephrographic without urographic excretory imaging. The three-phase CT urogram is the closest existing node and is what this fork resolves to. Its excretory series is genuinely useful where urothelial disease is also in question and is otherwise a dose penalty that a local renal mass protocol would avoid.
Characterisation of the renal lesion itself, including the MRI-first argument, belongs to the indeterminate-renal-mass card.

Hepatocellular carcinoma — four-phase liver staging

Role	Study & protocol	Why this answers the question
First line	CT Liver — Multiphase CT Liver — Four Phase (LI-RADS Compliant) usually appropriate	Hepatocellular carcinoma is the one hypervascular primary for which the late arterial phase alone is still not enough. The diagnostic signature is arterial hyperenhancement FOLLOWED by washout and an enhancing capsule, and washout is a delayed-phase observation — so the four-phase set (unenhanced, late arterial, portal venous, delayed) is the protocol, and a triphasic study without the delayed acquisition cannot support a category. The unenhanced series separates true enhancement from intrinsic density in a treated or haemorrhagic lesion. Arterial timing must be LATE arterial: portal vein opacified, hepatic veins not yet, which is the commonest technical failure in this disease.
First line	CT Chest CT Chest — Contrast-Enhanced (Venous Phase)	Extrahepatic staging is a venous-phase question here as everywhere else. The lung and the bones are the extrahepatic sites that change management, and both are assessed on a standard venous chest acquisition.

Surveillance and diagnosis of hepatocellular carcinoma in the at-risk liver is the subject of the suspected-hcc-in-cirrhosis card. This fork covers the staging request written generically in a patient whose hepatocellular primary is already established.

Hypervascular primary — late arterial liver acquisition required

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: these metastases are supplied almost entirely by the hepatic artery and are already isodense by the time the portal inflow has brought the parenchyma up. A portal-venous-only staging CT in this group does not under-call the disease, it reports as a false negative. The venous acquisition is retained because it stages the rest of the abdomen and pelvis and because a minority of deposits — higher-grade neuroendocrine tumours particularly — are hypovascular; the unenhanced series separates arterial enhancement from calcification or haemorrhage.
First line	CT Chest CT Chest — Contrast-Enhanced (Venous Phase)	Thoracic staging is unchanged by the hypervascular question and stays in the venous phase. Only the liver acquisition needs arterial timing.

This fork deliberately does not restate the physiology: hypervascular-primary-liver-staging is the card that owns it, including the negative-CT-with-rising-marker case and the escalation to liver MRI. The fork exists so that a request written as a generic staging CT still reaches the right protocol.
Somatostatin receptor PET-CT, the functional counterpart for a neuroendocrine primary, has no study node in this vocabulary and must be requested outside this pathway.

Completion staging — abdominal study already performed

Role	Study & protocol	Why this answers the question
First line	CT Abdomen and Pelvis CT Abdomen and Pelvis — Portal Venous Phase	Already performed for this episode, and shown here so the plan reads as a sequence rather than a single verdict. Repeating it is only justified if the completed study was unenhanced, mistimed, or cropped above the pelvis — which is worth checking, because a staging assessment completed on top of an inadequate abdominal study inherits that inadequacy.
First line	CT Chest CT Chest — Contrast-Enhanced (Venous Phase) usually appropriate	The completion chest is a venous-phase acquisition, and the reasoning is not the same as the abdominal reasoning. Two of the three questions the thorax is being asked — mediastinal and hilar nodes separated from vessels, and pleural or chest wall deposits seen by their enhancement — depend on venous opacification, and an arterial-timed acquisition under-shows both. The third question, pulmonary metastases, is answered on lung windows and is essentially phase-independent, which is why an unenhanced chest is an acceptable completion when contrast cannot be given and nodal and pleural disease are not in play. There is no established indication for arterial timing of the THORAX in a hypervascular primary: the arterial argument in that group is a hepatic one, the evidence for transferring it to the chest is weak to absent, and doing so trades a real loss in nodal and pleural assessment for a theoretical gain.
Second line	CT Chest CT Chest — Unenhanced	The honest fallback where iodinated contrast cannot be given and the remaining thoracic question is pulmonary metastases alone. It is a real answer rather than a degraded one for that narrow question, because nodules are called on lung windows. It is not a substitute where nodal, pleural or chest wall disease matters, and a negative unenhanced study must not be reported as excluding them.
Problem solving	FDG PET-CT FDG PET-CT — skull base to mid-thigh	Where the completed abdominal study has left a single indeterminate finding that decides between radical and palliative intent, metabolic imaging answers that question better than a second anatomical pass. It does not replace the venous chest acquisition: the CT component of a standard PET-CT is unenhanced and low-dose.

Entered from ctx.completedStudies. This is the fork that stops the tool telling a referrer to do the abdominal CT that is already on the archive — a false correction is how a vetting tool teaches people to route around it.
It is deliberately the LAST conditional fork. For a renal, pancreatic, hepatocellular or other hypervascular primary the tumour-specific forks match first, because a completed portal-venous abdomen has not answered the abdominal question in those diseases and calling the staging complete after adding a chest would be wrong.
Ask what phase the completed abdominal study used, not just that it happened. A completion built on an unenhanced or mistimed abdomen is a completion of nothing.
The chest and the abdomen are two study nodes here but one clinical acquisition where the scanner allows; a completion request is precisely the case where they are genuinely separate exposures, and the second one carries its own contrast load.

Adults — standard staging, portal venous alone

Matches your inputsDefault

Role	Study & protocol	Why this answers the question
First line	CT Abdomen and Pelvis CT Abdomen and Pelvis — Portal Venous Phase usually appropriate	A single portal venous acquisition is the whole answer here, and saying so is the point of this pathway. At roughly 60-80 seconds the liver parenchyma reaches peak enhancement from portal inflow, and the ordinary hypovascular metastasis — colorectal, lung, breast, lymphoma, head and neck, most gynaecological — becomes conspicuous precisely because the BACKGROUND has brightened around it, not because the lesion itself enhances. The same acquisition gives enhancing bowel wall, opacified veins for tumour thrombus, and enough nodal-to-vessel discrimination to stage the retroperitoneum. For these primaries a late arterial phase is not a safety margin: it is a second exposure and a second contrast load that adds no staging information, and it adds a series on which transient hepatic perfusion abnormality is routinely over-called as metastatic disease.
First line	CT Chest CT Chest — Contrast-Enhanced (Venous Phase)	The thorax is staged in the same venous acquisition, extended upwards. Mediastinal and hilar nodes are separable from vessels only once the vessels are opacified, and pleural deposits are seen by their enhancement. Running the chest and abdomen as one contiguous pass at a single venous timing is the standard economy here; a separate early thoracic acquisition mis-times the abdomen.
Problem solving	FDG PET-CT FDG PET-CT — skull base to mid-thigh	Reserved for the situation where a single indeterminate finding on CT decides between curative and palliative treatment, or where the primary is characteristically FDG-avid and occult nodal disease would change the plan. It is a problem-solving study on top of anatomical staging, not a replacement for it: the CT component of a standard PET-CT is unenhanced and low-dose, so it does not answer the questions that portal-venous CT answers.

Chest and abdomen/pelvis are one clinical request even though they are two study nodes here; vet them together and protocol them as a single acquisition where the scanner allows.

Pitfalls

Accepting a staging request that did not specify contrast. An unenhanced staging CT understages liver and nodal disease and is often the reason a patient is restaged weeks later.
Cropping the abdomen at the iliac crests on a request that said "abdomen": peritoneal, adnexal and nodal disease sits below that line.
Adding an arterial phase reflexively to every staging CT. For a hypovascular primary it is pure dose, and the arterial images are the ones on which a perfusion artefact is over-called.
Staging a patient whose histology is not yet established, then finding the imaging cannot be interpreted because the differential was never narrowed.
Treating PET-CT as a substitute for contrast-enhanced CT. The unenhanced low-dose CT component is for attenuation correction and localisation, not for characterising a liver lesion.

Priors — what to pull first

Find any imaging that predates the diagnosis. A nodule or node present and unchanged two years ago is not metastatic disease, and that comparison is frequently available and frequently not made.
Record slice thickness and reconstruction on this study — it becomes the technical baseline every subsequent response assessment must match.

What makes a good request

A good request names the primary, the histology if known, whether this is the baseline for planned systemic therapy, and what imaging has already been done. The last two change technique, not just reporting.
Portal venous alone is the correct and complete answer for most primaries — colorectal, lung, breast, lymphoma, head and neck, bladder, prostate and most gynaecological tumours. Their metastases are hypovascular and become conspicuous because the BACKGROUND liver peaks at 60-80 s, not because the lesion enhances. An arterial phase adds radiation, contrast load, scanner time and a series on which transient perfusion abnormality is over-called, and adds no staging information.
A late arterial acquisition is genuinely required where the metastases are hypervascular: hepatocellular carcinoma, neuroendocrine tumours, renal cell carcinoma, melanoma, thyroid carcinoma and sarcoma. These deposits are supplied by the hepatic artery, so they peak while the parenchyma is still dark and are isodense or invisible by the portal venous phase. The card that owns this question in full is hypervascular-primary-liver-staging; the fork here routes to the same multiphase study rather than restating it.
Renal cell carcinoma is a separate case from the rest of the hypervascular group. The primary needs a corticomedullary and nephrographic approach — corticomedullary to judge the lesion against enhancing cortex and to show renal vein and caval tumour thrombus, nephrographic because slowly enhancing papillary tumours are called non-enhancing if measured only on an early or portal-venous acquisition — and its metastases are hypervascular on top of that.
Pancreatic ductal adenocarcinoma needs a dedicated pancreatic-phase protocol, not a routine portal-venous abdomen. The tumour is defined by its attenuation difference from the enhancing parenchyma, which peaks at around 40-45 s, and resectability is decided by arterial contact that a single venous acquisition cannot grade. The detection and resectability question in detail belongs to the suspected-pancreatic-mass card.
Where the tumour is FDG-avid and the distinction between locoregional and metastatic disease decides between radical and palliative intent, PET-CT belongs in the plan from the start rather than after a CT has already been done.

Scoring this once it is done

The classification and risk tools this question ends in.

RECIST 1.1 Tumor Response eGFR (CKD-EPI 2021 Creatinine)Lung Cancer TNM Staging (9th Edition)Liver Volume (CT/MRI/US) + Expected Volume C-RADS v2023 (CT Colonography Reporting & Data System)Bosniak Classification v2019 (Cystic Renal Mass, CT/MRI)Clear Cell Likelihood Score (ccLS) v2.0 — Renal Mass mpMRI RENAL Nephrometry Score Lutathera Dose Modification for Adverse Reactions LI-RADS v2018 (CT/MRI)BCLC Staging & Treatment Strategy (2022 Update)Child-Pugh Score (Child-Turcotte-Pugh)MELD 3.0 Score ALBI (Albumin-Bilirubin) Grade Milan Criteria / UCSF (Expanded) Criteria mRECIST for Hepatocellular Carcinoma

How these studies are acquired

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

CT Pancreas — Dual Phase with Water Distension CT Chest — Contrast-Enhanced (Venous Phase)CT Urogram — Conventional Three Phase CT Liver — Triphasic (Unenhanced, Late Arterial, Portal Venous)CT Liver — Four Phase (LI-RADS Compliant)CT Abdomen and Pelvis — Portal Venous Phase CT Chest — Unenhanced FDG PET-CT — skull base to mid-thigh

Confirm locally

CT Abdomen and Pelvis — Portal Venous Phase: 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.