Suspected pneumothorax

BTS pleural disease guideline 2023

A radiograph question in nearly every case. CT is for the situations a radiograph genuinely cannot resolve — surgical emphysema, complex bullous lung, a supine trauma patient, or planning for surgery — and not for confirming what an erect film already showed.

Sudden pleuritic pain and breathlessness, deterioration after a pleural or lung procedure, or a routine post-procedural check.

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

Haemodynamic state

The fact that lets a pathway waive its own requirements. A crashing patient does not wait for a score.

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

Pleural air rises, and on an erect film it collects at the apex where it is silhouetted against aerated lung as a fine visceral pleural line — the single easiest high-contrast finding in chest radiography. The projection is the whole point: supine, the air redistributes anteriorly and basally where it produces only a deep sulcus or an unusually sharp cardiac border, and a substantial proportion of pneumothoraces are simply invisible. Expiratory films add little and are no longer routinely advised.

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.

Haemodynamically unstable — treat as tension pneumothorax before imaging

Role	Study & protocol	Why this answers the question
First line	CT Chest CT Chest — Unenhanced usually not appropriate	A tension pneumothorax is diagnosed at the bedside and decompressed there, and the only thing a scan slot adds is the transfer during which the patient arrests. This is not a judgement that the request is unjustified — it is that the imaging is downstream of an intervention that has not happened yet. The correct response to a request describing haemodynamic compromise with suspected pneumothorax is a phone call: needle decompression or finger thoracostomy first, then the confirmatory film. Three cautions belong with that. Needle decompression fails often enough that it should never be assumed to have worked — a standard cannula is frequently too short to reach the pleural space at the second intercostal space in the mid-clavicular line in an adult, which is why the fourth or fifth intercostal space in the anterior axillary line, or an open finger thoracostomy, is now the preferred site, and why a definitive chest drain follows either way. Haemodynamic compromise in a patient with a pneumothorax is not always tension — tamponade, massive haemothorax, pulmonary embolus and pure hypovolaemia all present the same way, and if decompression does not restore the circulation the differential reopens immediately. And a patient who is genuinely stable enough to travel, in whom the request has overstated the compromise, belongs on the ordinary pathway below.
Second line	Thoracic / pleural ultrasound Thoracic ultrasound — pleural assessment and site marking	Where imaging is used at all before decompression it is the probe already at the trolley, because it costs seconds and no transfer: absent lung sliding with absent B-lines at the non-dependent chest wall, and a lung point where aerated lung meets the pneumothorax. It is more sensitive than the supine film this patient would otherwise get, and the same probe marks the site and depth for the drain that follows. It is an adjunct to resuscitation and must not become a reason to defer decompressing a patient who is losing their circulation; absent sliding alone is not specific, being lost in adhesion, main-bronchus intubation and consolidated non-ventilated lung.
Second line	Chest radiograph Chest radiograph — PA (± lateral)	The film comes after the decompression, and its questions are different ones: has the lung re-expanded, where has the drain gone, and is there a second pathology — a haemothorax, a widened mediastinum, an aspirated lung — that the initial picture hid. Read it knowing the projection: a supine or semi-erect portable film redistributes pleural air anteriorly and basally, so a residual pneumothorax can be substantial and nearly invisible.

Nothing here refuses a study. It sequences one intervention ahead of the imaging and says so out loud, which is what the card already advised in prose and could not previously act on.

Adults

Matches your inputsDefault

Role	Study & protocol	Why this answers the question
First line	Chest radiograph Chest radiograph — PA (± lateral) usually appropriate	Pleural air rises, and on an erect film it collects at the apex where it is silhouetted against aerated lung as a fine visceral pleural line — the single easiest high-contrast finding in chest radiography. The projection is the whole point: supine, the air redistributes anteriorly and basally where it produces only a deep sulcus or an unusually sharp cardiac border, and a substantial proportion of pneumothoraces are simply invisible. Expiratory films add little and are no longer routinely advised.
Problem solving	CT Chest CT Chest — Unenhanced	Reserved for the situations where a radiograph is genuinely uninterpretable or insufficient: distinguishing a large bulla from a pneumothorax before a drain is placed into the wrong one, extensive surgical emphysema, a supine ventilated or trauma patient, suspected underlying parenchymal disease driving a secondary pneumothorax, and surgical planning after recurrence. No contrast is needed — air against lung requires no help.
Problem solving	Thoracic / pleural ultrasound Thoracic ultrasound — pleural assessment and site marking	The bedside answer for the patient who cannot be sat up — the ventilated, the trauma patient, the one whose supine film is the least reliable projection there is. Absent lung sliding and absent B-lines at the non-dependent chest wall, with a lung point where aerated lung meets the pneumothorax, localise pleural air more sensitively than a supine radiograph and take a minute at the trolley. It is also the study to use when a drain is going in: the same probe that looks for sliding marks the space and records the depth, which is the image guidance BTS asks for before any pleural procedure. It does not replace the erect film in a patient who can stand, and it cannot map the bullous lung that surgical planning needs.

Pitfalls

Requesting CT to confirm a pneumothorax already visible on the radiograph. It delays drainage and adds dose without changing anything.
Reading a supine film as if it excluded a pneumothorax.
Mistaking a large thin-walled bulla for a pneumothorax and draining it. The bulla has a concave inner margin that does not follow the chest wall contour, and getting this wrong creates a persistent air leak.
Skin folds, tubing, scapular edges and hair braids produce lines that mimic a visceral pleural edge; lung markings running beyond the line settle it.
Ordering imaging first in a patient described as haemodynamically compromised — tension pneumothorax is decompressed on clinical grounds.
Reading absent lung sliding on ultrasound as diagnostic of pneumothorax. It is lost in pleural adhesion, in a main-bronchus intubation and in consolidated non-ventilated lung; the lung point is the specific sign.
Treating a small pneumothorax in a ventilated patient as one to watch. Positive pressure feeds a pneumothorax and any size can tension within minutes, so the threshold for drainage is far lower here than in a spontaneously breathing patient — and the projection that would show it is the supine film, which is the one that hides it.
Reading a pneumothorax in a patient with underlying lung disease as if it were a primary one. A secondary spontaneous pneumothorax in emphysema or fibrosis is worse tolerated at every size, is drained more readily, and needs the underlying parenchyma described because it changes both the management and the recurrence risk.
Forgetting that a pneumothorax found after a procedure has a clock on it. Post-biopsy and post-line pneumothoraces can enlarge over hours, so a small one on the immediate film is a reason to repeat rather than to discharge, and the request should say which procedure and when.
Assuming a decompression worked because it was performed. A needle that did not reach the pleura, or a cannula that has kinked, leaves a tension pneumothorax untreated behind a reassuring entry in the notes — the confirmatory film is looking for re-expansion, not merely for the drain.

Priors — what to pull first

Compare with the most recent film before calling recurrence — a chronic stable apical bulla or a persistent post-surgical space is not a new pneumothorax.
In a patient with repeated presentations, look for the underlying lung disease on any prior CT: secondary pneumothorax behaves differently and is managed more aggressively.

What makes a good request

A tension pneumothorax is a clinical diagnosis treated before imaging. A request that describes haemodynamic compromise should prompt a phone call, not a scan slot.
Management has moved towards a symptom-based approach, with conservative and ambulatory strategies for many patients — so the size measured on the film is only one input, and precision beyond what changes the decision is not worth extra imaging.
A good request states the projection available, whether the patient can sit up, whether there is underlying lung disease, and what procedure preceded the presentation.

Scoring this once it is done

The classification and risk tools this question ends in.

Pneumothorax Size (Rhea / Collins / BTS / ACCP)AAST Lung Injury Scale

How these studies are acquired

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

CT Chest — Unenhanced Thoracic ultrasound — pleural assessment and site marking Chest radiograph — PA (± lateral)

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.