Cxt pneumothorax

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Pneumothorax on Chest X-Ray (CXR)

Definition

Air in the pleural space is a pneumothorax. When air and liquid are both present, a prefix is added: hydro-, haemo-, pyo-, or chylo- depending on the fluid type. - Grainger & Allison's Diagnostic Radiology, p. 67

Classic CXR Signs (Erect PA Film)

On an erect radiograph, pleural air rises to the lung apex. The hallmark findings are:

Visceral pleural line - a thin, sharp white line running parallel to the chest wall, representing the edge of the collapsed lung
Hyperlucent zone - avascular, dark region between the pleural line and the chest wall, with a complete absence of lung markings (vessels)
Partial lung collapse - ipsilateral lung appears denser/smaller than normal

The right-sided pneumothorax below demonstrates these features clearly - note the absence of lung markings and increased (air density) lucency lateral to the pleural line:

Right-sided pneumothorax - absence of lung markings lateral to the pleural line

FIGURE: Right-sided pneumothorax showing absence of lung markings and increased lucency lateral to the pleural line. - Tintinalli's Emergency Medicine, p. 1775

Expiratory CXR

Taking the film at deep expiration accentuates a pneumothorax because the lung volume decreases while the air in the pleural space remains constant, making the gap relatively larger. This is especially useful for small/subtle pneumothoraces.

Left primary spontaneous pneumothorax - expiratory view (B) better demonstrates the pneumothorax

Fig. 3.17B: Left PSP, deep expiration - pneumothorax is accentuated. - Grainger & Allison's Diagnostic Radiology, p. 67

Tension Pneumothorax on CXR

Tension pneumothorax is a clinical diagnosis - do NOT delay treatment to get a CXR. If a film is taken, features include:

Feature	Description
Contralateral mediastinal shift	Trachea/heart pushed away from affected side
Ipsilateral diaphragm depression	Pushed inferiorly - the more reliable sign
Expanded ipsilateral hemithorax	With complete collapse of the lung

"Mild degrees of contralateral mediastinal shift are not unusual with a nontension pneumothorax because of the negative pressure in the normal pleural space. However, moderate or gross mediastinal shift should be taken as indicating tension, particularly if the ipsilateral hemidiaphragm is depressed." - Grainger & Allison's Diagnostic Radiology, p. 69

The image below shows a large left-sided pneumothorax with contralateral mediastinal shift (tension pattern):

Large pneumothorax with mediastinal shift and lung collapse - portable CXR

Fig. 3.19: Supine pneumothorax - large left-sided air collection with mediastinal shift. - Grainger & Allison's Diagnostic Radiology

Supine / Atypical CXR Signs

When the patient is supine (e.g. ICU/trauma), air rises anteriorly and basally, not to the apex. The classic apical pleural line may be absent. Look for:

Sign	Appearance
Deep sulcus sign	Ipsilateral costophrenic angle appears abnormally deep and lucent
Generalised ipsilateral hyperlucency	Affected hemithorax appears darker overall
Double diaphragm sign	Anterior costophrenic recess seen as an oblique line, parallel to but distinct from the real diaphragm
Transradiant band	Parallel to diaphragm and/or mediastinum; undue clarity of mediastinal border
Visible cardiac fat pads	Appear as rounded opacities suggesting masses

Grainger & Allison's Diagnostic Radiology, p. 68

Pitfalls and Mimics

Skin folds are the most common mimic - especially in neonates and elderly patients positioned slumped in AP projection. Features that help distinguish skin fold from real pneumothorax:

Skin fold line extends beyond the chest wall margin
Laterally located blood vessels are still visible beyond the line
The fold line is much wider than the thin visceral pleural line
Orientation is inconsistent with the edge of a partially collapsed lung

Other mimics: bullae, pneumatoceles, pneumomediastinum, local emphysema. When doubt remains, CT is definitive.

Sizing the Pneumothorax

Method	Small	Large
BTS (British Thoracic Society)	Visible rim <2 cm at apex	Rim ≥2 cm at apex
ACCP (Light's criteria)	<15% hemithorax volume	>15% hemithorax volume

Clinically, size alone does not drive management - symptoms and haemodynamic status are equally important.

Diagnostic Sensitivity

Modality	Sensitivity
Erect PA CXR	~83%
Supine AP CXR	~20-50% (misses 17-80%)
POCUS	Higher than supine CXR; rapid bedside diagnosis
CT	Most sensitive; gold standard for small/occult pneumothoraces

"CXR will miss between 17% and 80% of pneumothoraces for upright and supine chest radiographs, respectively. POCUS is more sensitive than a supine radiograph." - Tintinalli's Emergency Medicine, p. 1775

Causes Summary

Category	Examples
Primary spontaneous (PSP)	Ruptured apical bleb; young tall males, 20-40 yrs, M:F = 5:1
Secondary spontaneous (SSP)	COPD, asthma, cystic fibrosis, TB, cavitating pneumonia, Marfan syndrome, LAM, histiocytosis X
Traumatic (non-iatrogenic)	Rib fracture, penetrating trauma, ruptured oesophagus/trachea
Iatrogenic	Central line insertion, thoracocentesis, percutaneous biopsy, tracheostomy
Catamenial	Endometriosis - occurs within 72 hours of menstruation

Grainger & Allison's Diagnostic Radiology, Table 3.2, p. 68

POCUS Findings (Ultrasound)

For completeness - when CXR is unavailable or inconclusive:

Absent pleural sliding (replaced by "barcode/stratosphere sign" on M-mode) - suggests pneumothorax
Lung point (transition between sliding and no-sliding) - highly specific for pneumothorax; represents the edge of the air collection
B-lines absent - their presence excludes pneumothorax at that location
Sea-shore sign absent on M-mode
Murray & Nadel's Textbook of Respiratory Medicine

Cxr findings in pneumothorax

I already covered this in detail in my previous response! Here's a focused summary of all CXR findings in pneumothorax:

CXR Findings in Pneumothorax

Erect PA Film (Classic/Standard)

Finding	Description
Visceral pleural line	Thin, sharp white line parallel to the chest wall - the collapsed lung edge
Hyperlucent zone	Dark, avascular area between the pleural line and chest wall - no lung markings visible
Absent lung markings	No vascular shadows peripheral to the pleural line
Partial lung collapse	Ipsilateral lung appears smaller and relatively denser

Right-sided pneumothorax - pleural line visible, no lung markings lateral to it. - Tintinalli's Emergency Medicine

Expiratory Film

Pneumothorax is accentuated on a deep expiratory film
Lung shrinks on expiration but pleural air stays constant - increases the relative gap
Useful for small/subtle pneumothoraces not seen on inspiration film

Fig. 3.17B: Left PSP, expiratory CXR accentuates the pneumothorax. - Grainger & Allison's Diagnostic Radiology

Tension Pneumothorax (on CXR)

Remember: tension PTx is a clinical diagnosis - never delay treatment for imaging.

Finding	Detail
Ipsilateral diaphragm depression	Most reliable sign; almost invariably present
Contralateral mediastinal shift	Trachea and heart pushed to opposite side
Complete ipsilateral lung collapse	Dense opaque collapsed lung near hilum
Expanded hemithorax	Ribs spread apart on affected side

Supine / AP Film (ICU, Trauma)

Air rises anteriorly and basally - not to the apex. The classic apical pleural line may be absent. Signs to look for:

Sign	Appearance
Deep sulcus sign	Ipsilateral costophrenic angle abnormally deep and lucent - most recognisable sign
Generalised ipsilateral hyperlucency	Affected side appears darker overall
Double diaphragm sign	Anterior costophrenic recess creates a second line parallel to the diaphragm
Transradiant band	Along diaphragm or mediastinal border; mediastinal border appears unusually sharp
Visible cardiac fat pads	Appear as rounded opacities
Diaphragm depression	Present in larger collections

Supine pneumothorax - deep sulcus sign left base, mediastinal shift

Fig. 3.19: Supine portable CXR - left-sided pneumothorax, deep sulcus sign, increased basal transradiancy. - Grainger & Allison's Diagnostic Radiology

Pitfalls / Mimics on CXR

Mimic	How to differentiate
Skin fold	Line extends beyond chest wall; vessels visible beyond line; line much wider than pleural line; orientation inconsistent with collapsed lung edge
Bulla/bleb	No pleural line; concave inner margin; CT differentiates
Pneumomediastinum	Air tracks along mediastinal structures; continuous diaphragm sign
Gastric bubble	Subdiaphragmatic; air-fluid level

When in doubt: CT is definitive (also detects occult pneumothoraces missed on CXR in 25-40% post-biopsy cases).

Sensitivity of CXR

Position	Sensitivity
Erect PA	~83%
Supine AP	Misses 17-80% of pneumothoraces

POCUS outperforms supine CXR and is now the preferred bedside tool in trauma/ICU settings.

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