Suspected interstitial lung disease

ATS/ERS/JRS/ALAT 2022 IPF and PPF guideline

A pattern-recognition study, not a detection study. The diagnosis is made from the distribution of reticulation, the presence of honeycombing and the behaviour of the lung in expiration — which means the supine, prone and expiratory series together are the examination, and contrast has no part in it.

Progressive exertional breathlessness with a dry cough, bibasal crackles, clubbing or restrictive spirometry, or an incidental interstitial abnormality found on a scan done for something else.

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 Chest — High Resolution (Interstitial Protocol)

CT Chest

What we'd amend, and why

Each series answers a question no other series can. The supine inspiratory volumetric acquisition establishes the distribution and the presence of honeycombing. The prone series exists because dependent atelectasis in the posterobasal segments looks exactly like early subpleural reticulation, and moving the patient makes atelectasis vanish while fibrosis stays — that single manoeuvre is what separates a normal scan from an early UIP pattern. The expiratory series exists because air trapping is invisible at full inspiration; only when normal lung deflates and diseased lobules do not does mosaic attenuation become attributable to small airways disease, which is what points towards hypersensitivity pneumonitis rather than fibrosis. Contrast obscures nothing and reveals nothing here, and adds a cannula, a renal check and cost to a study that gains none of it.

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
rulerule-pregnancy-ionising — Pregnancy status before an ionising exposure; 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.

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.

Pathways

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

Adults

Matches your inputsDefault

Role	Study & protocol	Why this answers the question
First line	CT Chest CT Chest — High Resolution (Interstitial Protocol) usually appropriate	Each series answers a question no other series can. The supine inspiratory volumetric acquisition establishes the distribution and the presence of honeycombing. The prone series exists because dependent atelectasis in the posterobasal segments looks exactly like early subpleural reticulation, and moving the patient makes atelectasis vanish while fibrosis stays — that single manoeuvre is what separates a normal scan from an early UIP pattern. The expiratory series exists because air trapping is invisible at full inspiration; only when normal lung deflates and diseased lobules do not does mosaic attenuation become attributable to small airways disease, which is what points towards hypersensitivity pneumonitis rather than fibrosis. Contrast obscures nothing and reveals nothing here, and adds a cannula, a renal check and cost to a study that gains none of it.
Problem solving	CT Chest CT Chest — Unenhanced	Once the pattern has been established, serial assessment of extent and progression can be done with a single supine inspiratory volumetric acquisition, which halves the exposure in a disease that is followed for years. This is a follow-up compromise, not a diagnostic one — it cannot demonstrate air trapping and should not be used to make the first diagnosis.

Pitfalls

Letting the expiratory series be dropped for throughput. Without it, air trapping cannot be assessed and hypersensitivity pneumonitis cannot be distinguished from fibrotic ILD.
Omitting the prone series and reporting dependent atelectasis as early subpleural fibrosis, which converts a normal patient into one with a serious diagnosis.
Adding intravenous contrast because the request said "CT chest" — it obscures nothing but buys nothing, and it makes serial comparison harder.
A poor inspiratory breath-hold, which produces diffuse ground-glass opacity across the whole study and can look like an acute exacerbation.
Reporting a pattern without the clinical context. The same reticulation means different things in a patient with rheumatoid disease, an asbestos exposure history and a bird keeper.

Priors — what to pull first

Find any older chest CT, however it was acquired. Interstitial change that is unchanged over five years is a different disease from the same appearance acquired over eighteen months, and the rate of change is what drives treatment.
Match the inspiratory effort and reconstruction of the comparison study before calling progression — an underinflated study manufactures ground-glass and reticulation.

What makes a good request

A good request gives the occupational and drug history, any connective tissue disease, exposure to birds, mould or dust, and the spirometry and transfer factor — the radiological pattern is only diagnostic within that clinical frame.
The imaging classification that matters is a four-way one: usual interstitial pneumonia, probable UIP, indeterminate, or an alternative diagnosis. In the right clinical context a UIP pattern can establish the diagnosis without biopsy, which is exactly why the technique has to be right.
Interstitial lung disease is a multidisciplinary diagnosis. A report that names a pattern and the confidence attached to it is more useful than one that names a disease.

Scoring this once it is done

The classification and risk tools this question ends in.

Fleischner / ATS 2018 UIP CT Pattern

How these studies are acquired

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

CT Chest — High Resolution (Interstitial Protocol)CT Chest — Unenhanced

Confirm locally

CT Chest — High Resolution (Interstitial Protocol): 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.