Peripheral arterial disease — imaging before revascularisation

NICE CG147; NICE QS52

Imaging is for planning an intervention, not for making the diagnosis — which is clinical and ankle-pressure based. NICE CG147 makes duplex ultrasound the first imaging test; cross-sectional angiography comes after it, once duplex has established that revascularisation is realistic or has failed to answer the question. The characteristic failure of the cross-sectional study is technical: the table outruns the bolus and normal calf vessels are reported as occluded.

Lifestyle-limiting claudication, rest pain, tissue loss or an acutely ischaemic limb in a patient in whom revascularisation is being considered.

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

Time since onset

Decides thrombolysis and thrombectomy windows, testicular salvage, and whether an ischaemic limb is still salvageable.

Where is the patient?

Some pathways change in the emergency department — an acutely threatened limb is not an elective work-up.

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

Lower-limb arterial duplex — full runoff mapping

Arterial duplex ultrasound

What we'd amend, and why

Duplex answers the question peripheral arterial disease actually poses, which is haemodynamic rather than anatomical: a spectral waveform tells you whether a segment is obstructed, and the peak systolic velocity ratio across a lesion grades it, whereas a cross-sectional lumen diameter only infers it. It does this with no radiation and no contrast in a population defined by diabetes and chronic kidney disease, it can be repeated as often as the disease is reassessed, and it is dynamic — a popliteal entrapment or a graft stenosis is demonstrated by scanning through the manoeuvre or along the anastomosis. NICE CG147 therefore makes it the first-line imaging test for everyone being considered for revascularisation, and reserves contrast-enhanced angiography for those in whom duplex has shown that intervention is on the table or has failed to answer. Its declared limits are the legitimate trigger for the next study: an unseen aortoiliac segment in a gaseous abdomen, dense calcification that makes a stenosis ungradeable, or a distal runoff that has to be defined before a bypass target is chosen.

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

How was this decided?

pathwayadult — Adults — chronic peripheral arterial disease

Decision support only. Local protocol takes precedence.

Pathways

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

Acutely threatened limb — onset within hours, or an emergency presentation

Role	Study & protocol	Why this answers the question
First line	CT Angiogram — Lower Limb Runoff CT Angiogram — Aortoiliac and Lower Limb Runoff usually appropriate	The duplex-first sequence in CG147 is written for chronic disease being worked up for elective revascularisation. It does not apply to a limb that is threatened now: the tissue tolerance is measured in hours, a vascular laboratory study takes an operator and a slot that an emergency department cannot summon at three in the morning, and the operator needs the inflow, the level of occlusion and the distal target in one pass. CT angiography from the diaphragm to the pedal arch delivers all three in minutes and simultaneously shows an embolic source, an aneurysm and a dissection, which are the alternatives to in-situ thrombosis. Imaging must not delay heparinisation or the vascular opinion — it runs alongside them.
Problem solving	Arterial duplex ultrasound Lower-limb arterial duplex — full runoff mapping	Duplex still has a place in the acute limb, but a narrow one: confirming that flow is absent in an accessible segment where the diagnosis is in doubt, and mapping the arterial tree when iodinated contrast genuinely cannot be given and the alternative is no imaging at all. It is not the study that gets a threatened limb to theatre, because it cannot show the inflow and the runoff in the time available.

This fork is entered on the time since onset, or on the care setting where no onset is given. Both are starting assumptions rather than substitutes for reading the indication: a patient attending an emergency department with stable claudication belongs on the elective pathway, and a ward inpatient whose leg turned white five hours ago belongs on this one whatever the setting field says.
The clock is the point. Rutherford category is what actually decides between an angiogram, a theatre and an amputation, and it is a bedside assessment — sensory loss, motor loss and Doppler signals — that no imaging replaces. State it, and state the onset, because a category IIb limb is a theatre case in which imaging happens on the way rather than beforehand.

Adults — chronic peripheral arterial disease

Matches your inputsDefault

Role	Study & protocol	Why this answers the question
First line	Arterial duplex ultrasound Lower-limb arterial duplex — full runoff mapping usually appropriate	Duplex answers the question peripheral arterial disease actually poses, which is haemodynamic rather than anatomical: a spectral waveform tells you whether a segment is obstructed, and the peak systolic velocity ratio across a lesion grades it, whereas a cross-sectional lumen diameter only infers it. It does this with no radiation and no contrast in a population defined by diabetes and chronic kidney disease, it can be repeated as often as the disease is reassessed, and it is dynamic — a popliteal entrapment or a graft stenosis is demonstrated by scanning through the manoeuvre or along the anastomosis. NICE CG147 therefore makes it the first-line imaging test for everyone being considered for revascularisation, and reserves contrast-enhanced angiography for those in whom duplex has shown that intervention is on the table or has failed to answer. Its declared limits are the legitimate trigger for the next study: an unseen aortoiliac segment in a gaseous abdomen, dense calcification that makes a stenosis ungradeable, or a distal runoff that has to be defined before a bypass target is chosen.
Second line	MR Angiogram Peripheral (Lower Limb Runoff) Peripheral CE-MRA — three-station bolus-chase runoff usually appropriate	The cross-sectional study CG147 names first once duplex has established that revascularisation is being considered. A three-station bolus-chase acquisition maps the infrarenal aorta to the pedal arch without radiation and without iodine, which matters in a population that will be imaged repeatedly and whose kidneys are already the limiting factor, and it is not degraded by the dense tibial calcification that blooms across the lumen on CT. The costs are real and belong in the vetting decision: a long acquisition with the legs immobilised in a patient with rest pain, a susceptibility void at every metallic stent that reads as occlusion unless the stent history is known, and systematic overestimation of stenosis in the small distal vessels.
Second line	CT Angiogram — Lower Limb Runoff CT Angiogram — Aortoiliac and Lower Limb Runoff usually appropriate	The runoff map for patients who cannot have MR angiography — a non-conditional device, a body habitus or a claustrophobia that defeats a twenty-minute acquisition, or simply the speed a deteriorating foot needs. The acquisition has to travel a metre of anatomy while the contrast bolus travels the same distance through a circulation that is, by definition, obstructed. That is why the injection is biphasic — a short fast leading bolus to opacify the aorta, then a longer slower phase to keep the calf and pedal vessels filled once the leading edge has passed — and why table speed has to be matched to transit rather than fixed. Slow flow through a large aneurysm, poor cardiac output or a tight proximal stenosis all delay arrival distally, and if the table wins the race the pedal arteries appear absent. Immobilising the legs matters because the whole value of the study is in curved reformats along vessels only two or three millimetres across, and a small movement between the proximal and distal parts of the acquisition destroys them.
Problem solving	CT Angiogram — Aorta CT Aorta — Aneurysm Assessment and Planning	Where the clinical question is confined to inflow — buttock and thigh claudication, absent femoral pulses, or sizing before an aortoiliac endovascular procedure — an aortoiliac acquisition answers it with a shorter scan, a smaller contrast load and none of the bolus-timing difficulty that makes a full runoff fail. It is also the answer to the segment duplex is least able to see, since the distal aorta and iliac arteries are the vessels a gaseous abdomen hides. It is the right study when nobody is going to operate below the groin.

Duplex and the cross-sectional studies are sequential, not competing. The duplex report should say which segments could not be insonated and why, because that sentence is what justifies the next study.

Pitfalls

Opening at CT runoff. Duplex is the first-line test under CG147, and starting with the cross-sectional study delivers radiation and iodine to a vulnerable kidney to answer a question the vascular laboratory answers first — often well enough that no angiography is needed at all.
Reporting non-opacified calf and pedal vessels as occluded when the table has outrun the bolus. In a slow-flow patient this is the commonest false positive in the study, and it can cost a limb that was salvageable.
Dense mural calcification blooming across small tibial vessels and making stenosis grading unreliable — an explicit statement of confidence belongs in the report. On duplex the same calcification shadows rather than blooms, and the ungradeable segment must be declared rather than implied.
Treating a duplex that shows no distal target as excluding revascularisation. Duplex under-reads tibial and pedal runoff, and that is precisely the situation in which a cross-sectional map earns its contrast.
Imaging a patient who is not a revascularisation candidate. If neither surgery nor angioplasty is on the table, the scan changes nothing and delivers contrast to a vulnerable kidney.
Stopping the coverage at the ankle. The pedal arch is what determines whether a distal bypass has a target.
Using a venous-phase or portal-venous protocol, in which the arteries are no longer opacified.
Reading a normal resting duplex as excluding disease in a patient with exertional symptoms. The functional test is exercise with post-exercise ankle pressures, not another anatomical study.
Imaging an irreversibly ischaemic limb. Fixed mottling that does not blanch, tense muscle compartments, complete sensory and motor loss and absent arterial AND venous Doppler signals describe a Rutherford III limb, in which revascularisation is not on offer and the decision is primary amputation or palliation. A runoff study there delivers a large contrast load to a stressed kidney to answer a question nobody can act on, and it delays the conversation that should be happening instead.
Letting the scan become the reason heparinisation or the vascular opinion is late in an acutely threatened limb. The anticoagulation and the phone call happen on the way to the scanner, not after the report.
Reading an ankle-brachial pressure index of one or above as normal in a diabetic or dialysis patient. Medial calcification makes the vessels incompressible and the index falsely high, and toe pressures or the waveform shape are what carry the information there — a normal-looking index in that population is not a reason to stand down.

Priors — what to pull first

Retrieve previous angiographic or operative records. A previously stented segment, a known occluded bypass or a documented anatomical variant changes what the operator is looking for.
Where a graft is in question, the previous study defines the anastomoses, without which the reformats are hard to interpret.

What makes a good request

A good request states the ankle-brachial pressure index and any Doppler waveform information, the symptom severity and duration, the renal function, previous bypass or stenting, and whether the referral is for angioplasty or for surgery — the surgical plan needs the pedal arch, the endovascular plan needs the lesion.
NICE CG147 sequences the tests explicitly: duplex ultrasound first for everyone with peripheral arterial disease being considered for revascularisation, then contrast-enhanced MR angiography for those who need it, with CT angiography where MR angiography is contraindicated or not tolerated. A request that opens at CT runoff has skipped a step rather than chosen a better one.
Where duplex has already been performed and has shown disease that needs mapping, the pathway resumes at the cross-sectional step — state the duplex findings on the request, because without them a runoff request reads as a first test rather than a second one.
Acute limb ischaemia is a different pathway and is handled separately below: the limb is threatened in hours, duplex adds delay, and CT angiography is the first study. It should not delay heparinisation or a vascular opinion either.

Scoring this once it is done

The classification and risk tools this question ends in.

Ankle-Brachial Index (ABI)Rutherford Classification TASC II Classification eGFR (CKD-EPI 2021 Creatinine)

How these studies are acquired

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

CT Angiogram — Aortoiliac and Lower Limb Runoff Lower-limb arterial duplex — full runoff mapping Peripheral CE-MRA — three-station bolus-chase runoff CT Aorta — Aneurysm Assessment and Planning

Confirm locally

Lower-limb arterial duplex — full runoff mapping: 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.