First and second year — the floor first, then every step
Count the fractured ribs and find the flail segment, then look for the pneumothorax the radiograph missed, measure the haemothorax, and separate contusion from laceration.
Orient first
Pneumothorax in a supine patient collects ANTERIORLY and at the bases — a supine radiograph misses a large share of them, and the deep sulcus sign may be the only clue.
Contusion is bleeding into alveoli without architecture disruption; laceration tears the lung and forms a cavity (pneumatocele or haematocele). Contusion appears within hours and resolves in days; if an opacity appears later, think aspiration or pneumonia.
A flail chest is three or more consecutive ribs each broken in two or more places — a mechanical diagnosis you can count on CT.
Acquire the study
Thin-slice trauma CT read on lung, mediastinal and bone windows; sagittal and coronal reformats; a curved rib reformat for counting fractures.
The manoeuvre
Lung window, anterior and basal lung first: pneumothorax (and its depth in mm at the largest point), pneumomediastinum and subcutaneous emphysema.
Pleural fluid on the soft-tissue window: measure attenuation — blood about 30–70 HU — and the maximal depth in mm; a haemothorax with a high-attenuation focus that grows between phases is active bleeding.
Lung parenchyma: ground-glass or consolidation not respecting segments, often subpleural-sparing (contusion); a cavity with an air or blood level (laceration).
Ribs on bone window or the rib reformat: number every fracture by rib and site (anterior, lateral, posterior), displaced or not; mark consecutive ribs broken in two places (flail).
Sternum on sagittal, scapulae, clavicles and thoracic spine.
Central airways on lung window: tracheal or bronchial wall discontinuity, a "fallen lung" collapsed away from the hilum, persistent pneumothorax despite a drain — tracheobronchial injury.
Chest drain position: tip, side hole inside the pleura, and fissural or intraparenchymal placement.
What confirms it
Flail: three or more consecutive ribs each fractured in two or more places.
Haemothorax: pleural fluid of blood attenuation in a trauma patient.
What licenses you to exclude it
A supine radiograph cannot exclude pneumothorax; CT or ultrasound (lung sliding, lung point) is needed.
The classic misread
Missing an anterior pneumothorax by not using the lung window on the anterior slices.
Counting rib fractures without numbering the ribs from the first rib — errors propagate.
Calling a laceration a lung abscess on follow-up.
Reporting the injury
Classification to use
Describe by structure; flail segment by definition (≥ 3 consecutive ribs, each fractured in ≥ 2 places). AAST chest wall and lung injury scales exist but are rarely used in reports — name them only if your centre uses them.
Measurements — and how to take them
Pneumothorax: maximal depth in mm perpendicular to the chest wall (state where); some centres use a volume estimate — say which.
Haemothorax: maximal depth in mm on axial; attenuation in HU with the ROI placed in the fluid, not the clot.
Rib fracture displacement: offset in mm or in shaft widths.
What to report
Pneumothorax size and side (and tension signs: mediastinal shift, flattened hemidiaphragm), haemothorax depth and attenuation, active bleeding.
Rib fractures by rib number, site and displacement; flail segment; sternal, scapular, clavicular fractures.
Contusion and laceration by lobe; pneumomediastinum and airway injury; tube positions.
How to report it
CT: "Displaced fractures of the left 4th to 7th ribs, each at the anterolateral and posterior arcs, forming a flail segment. Left haemothorax, maximal depth 32 mm, attenuation 45 HU, without active extravasation. Contusion of the left lower lobe. Small anterior left pneumothorax, 8 mm depth."
What not to report
Do not report "multiple rib fractures" without numbers.
Do not call early contusion "consolidation / consider infection" on the admission CT.
Associated injuries to look for
First/second rib and scapular fractures → aortic and brachial plexus injury; lower rib fractures (9–12) → splenic, hepatic and renal injury; sternal fracture → cardiac contusion.
What changes management
Tension pneumothorax, a large or enlarging haemothorax, active bleeding, or a persistent air leak with a fallen lung (tracheobronchial injury).
Flail segment and the number of fractured ribs (ventilation, analgesia, surgical rib fixation).
Reference values
Each value carries the caveat that keeps it from being misused. Normal limits and diagnostic criteria are kept apart on purpose: a disease cut-off read as a normal range is the more dangerous mistake.
Diagnostic criteria
Ribs · Inferior rib notching
absent in the normal chest; bilateral inferior notching from the 3rd to the 8th ribs is the classic coarctation collateral sign
The 1st and 2nd ribs are NOT notched in coarctation (those intercostals arise above the obstruction). Superior notching is a different finding (rheumatoid, hyperparathyroidism).
X-ray · CT
Ribs (posterior) · Posterior-rib fracture in the infant
absent; posterior-rib fractures in a non-ambulant infant are a high-specificity inflicted-injury pattern — they are not the already-registered rib-notching entry
Obliques and a follow-up survey show what the first film misses. Healing callus is the clock.
X-ray · CT · paediatric
Pneumothorax · Size categorisation on an erect frontal film
the classical BTS criterion calls a pneumothorax large when the interpleural distance at the hilum is 2 cm or more; the ACCP convention measures 3 cm or more at the apex
⚠️ THE 2023 BTS GUIDELINE MOVED AWAY FROM SIZE-ALONE MANAGEMENT toward symptom- and risk-driven pathways — quote the measurement, but do not let a centimetre alone dictate management advice. A 2 cm rim at the hilum corresponds to roughly a 50% volume loss. Versioned criterion — verify against the current edition before clinical use.
X-ray
Pneumothorax (deep sulcus) · Deep-sulcus sign on a supine film
a named deep lucent costophrenic sulcus on a supine radiograph is the taught occult-pneumothorax clue — companion to chest2-pneumothorax-size, not a second size method
A deep sulcus can be a normal hyperinflated lung. Look for the visceral pleural line.
X-ray
Pleural fluid · Attenuation of pleural fluid
simple transudative fluid near water (roughly 0–20 HU); higher attenuation raises exudate, haemorrhage or proteinaceous fluid but overlaps widely
HU cannot reliably separate transudate from exudate. Acute haemothorax is denser (see the abdominal haematoma HU entry for the same physics) and may show a fluid–fluid level.
CT
Visceral pleural line · The line that makes a pneumothorax real
a thin visceral pleural line with no lung marking beyond it is the diagnosis; a skin fold has a thick edge and lung markings beyond
A skin fold is the classic false positive. Look for lung markings beyond the “line”.
X-ray
See it on real cases
Direct links to Radiopaedia — the reference article and worked cases with their images. Each opens on Radiopaedia.