Suspected pneumonia and non-resolving consolidation

ACR AC Acute Respiratory Illness in Immunocompetent Patients; BTS pleural disease 2023

Two different questions wear the same words. Acute suspected pneumonia is a radiograph question; consolidation that has not cleared after adequate treatment is a CT question, because the point is no longer the infection but what is obstructing or mimicking it.

Fever, cough and focal signs in an acute presentation, or a patient re-attending because an area of consolidation is still present on a follow-up radiograph weeks after treatment.

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

Immunosuppressed

Changes the differential rather than the modality.

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

Chest radiograph — PA (± lateral)

Chest radiograph

What we'd amend, and why

Consolidated lung is water-density tissue surrounded by air, which is the largest natural contrast difference in the body — so a radiograph, at a fraction of the dose of any cross-sectional study, resolves the question in the great majority of presentations. It also answers the two things that actually change management on the day: is there an effusion, and is there a pneumothorax or another gross abnormality. An erect PA at full inspiration matters because a supine film hides both.

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

How was this decided?

pathwayadult — Adults
rulerule-paeds-dose — Child-sized technique and contrast dose; checked by Radiographer at the scanner

Decision support only. Local protocol takes precedence.

Handled at the scanner(1)nothing for you to do

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

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.

Pathways

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

Immunosuppressed — early CT, and a normal radiograph excludes nothing

Role	Study & protocol	Why this answers the question
First line	CT Chest CT Chest — Unenhanced usually appropriate	Immunosuppression changes the differential rather than the anatomy, and that is precisely why it changes the study. Opportunistic infection is frequently radiographically occult — a neutropenic patient cannot mount the alveolar exudate that makes consolidation visible, so the film can be clean while the CT shows nodules with a ground-glass halo, tree-in-bud centrilobular nodules or diffuse ground glass — and a normal radiograph in this group therefore excludes nothing while costing days. The consequences of that delay are larger here than anywhere else on this card: invasive fungal disease is treated on imaging pattern plus galactomannan long before anything grows, and the CT is what triggers bronchoalveolar lavage. No contrast is needed, because the question is parenchymal and the discriminating findings are distribution and morphology in a lung kernel.
First line	Chest radiograph Chest radiograph — PA (± lateral) usually appropriate	The radiograph keeps its place alongside the CT rather than in front of it. It takes minutes at the bedside, it will occasionally show lobar consolidation, a large effusion or a pneumothorax and settle the immediate management, and it is a reasonable request in its own right — which is why it is co-first-line here and not a rung the referrer has to climb before the CT can be booked. What it cannot do in this population is exclude: a clear film in a febrile neutropenic patient is an unremarkable film, not a negative test, and treating it as reassurance is the specific error this fork exists to prevent.
Problem solving	CT Chest CT Chest — Contrast-Enhanced (Venous Phase)	Contrast is added for the same reason as on the default pathway and no other: a suspected complication or a mediastinal question — empyema, a necrotic cavity, an obstructing central lesion, nodal disease. Angioinvasive disease adds one indication of its own, since a vessel occluded within a nodule and a pseudoaneurysm in a cavitating lesion are both enhancement findings, and the second changes the risk of a lavage or a biopsy.

Nothing in this fork withholds the radiograph or makes the CT compulsory. It removes one specific behaviour: sending back a CT request in an immunosuppressed patient with an instruction to do the radiograph first.
Immunosuppression here is the fact as the request states it — transplantation, an active haematological malignancy or its treatment, high-dose steroids, a biologic agent, advanced HIV. The degree and duration decide how far the differential moves, and that belongs on the request rather than in this pathway.

Adults

Matches your inputsDefault

Role	Study & protocol	Why this answers the question
First line	Chest radiograph Chest radiograph — PA (± lateral) usually appropriate	Consolidated lung is water-density tissue surrounded by air, which is the largest natural contrast difference in the body — so a radiograph, at a fraction of the dose of any cross-sectional study, resolves the question in the great majority of presentations. It also answers the two things that actually change management on the day: is there an effusion, and is there a pneumothorax or another gross abnormality. An erect PA at full inspiration matters because a supine film hides both.
Second line	CT Chest CT Chest — Unenhanced	When the radiograph is negative or equivocal but the clinical picture still says pneumonia, CT resolves it without contrast: the question is parenchymal, and air-versus-tissue needs no help from iodine. CT also detects the small-volume and retrocardiac disease that a radiograph systematically loses.
Problem solving	CT Chest CT Chest — Contrast-Enhanced (Venous Phase)	For consolidation that has not cleared, and for suspected complication, contrast becomes necessary because the question has changed. It is now whether there is an obstructing central lesion, a necrotic cavity, an empyema or a nodal mass — all of which are soft-tissue discriminations that need venous-phase enhancement. Persistent consolidation in a smoker is an obstructing tumour until proven otherwise, and that is a mediastinal question, not a parenchymal one.
Problem solving	Thoracic / pleural ultrasound Thoracic ultrasound — pleural assessment and site marking	The radiograph answers "is there an effusion" and stops there. Where there is one, the next questions are whether it is simple or septated and whether it should be sampled, and those are ultrasound questions: a parapneumonic effusion that is anechoic and free-flowing is watched, one with fibrinous septation is drained, and the discrimination is far better on a high-frequency probe than on CT. It also separates fluid from consolidation and collapse where the film shows only a dense hemithorax, which changes the diagnosis rather than refining it. If anyone is going to put a needle in, BTS guidance makes the ultrasound a requirement rather than a convenience — the site is marked in the position the patient will sit in, with the depth recorded.

The pathway is deliberately sequential rather than parallel. A CT ordered simultaneously with the radiograph in an uncomplicated presentation is dose and cost with no added decision.
Where the radiograph shows an effusion alongside the consolidation, thoracic ultrasound is the branch that runs in parallel: it grades the effusion and enables sampling, while the CT question stays the parenchyma and the mediastinum.

Pitfalls

Scanning an uncomplicated community-acquired pneumonia in the first week because the patient still feels unwell — clinical improvement precedes radiographic clearing by weeks.
Requesting an unenhanced CT for non-resolving consolidation, which cannot exclude the obstructing central lesion that is the actual question.
Reading a supine or AP film as if it were an erect PA. Effusions layer posteriorly and become a diffuse veil rather than a meniscus, and are routinely missed.
Treating a normal radiograph as excluding pneumonia in an immunosuppressed or very early presentation.
Accepting "?pneumonia" as the whole indication when the patient has had six weeks of antibiotics — the vetting decision hinges entirely on which of the two questions is being asked.
Discharging a smoker over 50 after a treated pneumonia without the six-week radiograph. Consolidation distal to an obstructing tumour resolves partially with antibiotics and the patient feels better, which is exactly why the follow-up film exists — and it is the step most often missed on the way to a late-stage diagnosis.
Reading a cavitating or non-resolving consolidation as infection without asking who the patient is. Tuberculosis, invasive fungal disease, granulomatosis with polyangiitis, organising pneumonia and a necrotic tumour all look like a pneumonia that failed to clear, and the discriminator is usually the history and the microbiology rather than another scan.

Priors — what to pull first

Retrieve the radiograph that showed the original consolidation before scanning — "non-resolving" is a comparison, and without the comparator it is an assumption.
Check for a prior CT: consolidation that has been in the same segment repeatedly points at a fixed structural cause such as bronchiectasis, sequestration or an aspirated foreign body.

What makes a good request

A good request separates the two situations explicitly: state the duration of symptoms, the antibiotic course given, and the date and findings of the previous radiograph.
Consolidation is expected to take weeks to clear radiographically, and clears more slowly in older patients and in those with pre-existing lung disease. Repeating a radiograph too early manufactures a diagnosis of failure.
Where the patient is immunosuppressed, the calculus changes: an early CT is justified with a normal radiograph, because opportunistic infection is frequently radiographically occult and the consequences of delay are larger.
There is a follow-up step that is easy to drop, and dropping it is how lung cancer presents as pneumonia twice. A patient treated for pneumonia who has persistent symptoms or signs, or who carries a higher risk of underlying malignancy — broadly, a smoker or an ex-smoker over 50 — should have a repeat chest radiograph at about six weeks, and it is that film, not the acute one, that decides whether the CT on this card is needed. Nothing here asks for a radiograph in a well patient whose symptoms have fully resolved and who has no risk factors.

Scoring this once it is done

The classification and risk tools this question ends in.

CO-RADS eGFR (CKD-EPI 2021 Creatinine)

How these studies are acquired

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

CT Chest — Unenhanced Chest radiograph — PA (± lateral)CT Chest — Contrast-Enhanced (Venous Phase)Thoracic ultrasound — pleural assessment and site marking

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.