Pneumothorax refers to the presence of gas (air) in the pleural space. When this collection of gas is constantly enlarging with resulting compression of mediastinal structures it can be life-threatening and is known as a tension pneumothorax. For those pneumothoraces occurring in neonates see the article on neonatal pneumothorax.

There are many causes of pneumothorax which makes it impossible to generalise the epidemiology. However, primary spontaneous pneumothoraces occur in younger patients (typically less than 35 years of age) whereas secondary spontaneous pneumothoraces occur in older patients (typically over 45 years of age) 4

Presentation is variable and may range from no symptoms to severe dyspnea with tachycardia and hypotension. In patients who have a tension pneumothorax, presentation may be with distended neck veins and tracheal deviation, cardiac arrest and in the most severe cases, death.

It is interesting to note that some generalisations can be made in regards to the clinical presentation in primary versus secondary spontaneous pneumothoraces:

  • primary spontaneous: pleuritic chest pain usually present, dyspnoea mild or moderate
  • secondary spontaneous: pleuritic chest pain often absent, dyspnoea usually severe

It is useful to divide pneumothoraces into three categories 4:

  • primary spontaneous: no underlying lung disease
  • secondary spontaneous: underlying lung disease is present
  • iatrogenic/traumatic
Primary spontaneous

A primary spontaneous pneumothorax is one which occurs in a patient with no known underlying lung disease. Tall and thin people are more likely to develop a primary spontaneous pneumothorax. There may be a familial component, and there are well associations 10:

Secondary spontaneous

When the underlying lung is abnormal, a pneumothorax is referred to as secondary spontaneous. There are many pulmonary diseases which predispose to pneumothorax including:


Iatrogenic/traumatic causes include 1-4:

  • iatrogenic:
    • percutaneous biopsy
    • barotrama, ventilator
    • radiofrequency (RF) ablation of lung mass
  • trauma:
Chest radiograph

A pneumothorax is when looked for, usually relatively easily appreciated. Typically they demonstrate:

  • visible visceral pleural edge seen as a very thin, sharp white line
  • no lung markings are seen peripheral to this line
  • the peripheral space is radiolucent compared to adjacent lung

In cases where these features are not clearly present a number of techniques can be employed:

  • lateral decubitus radiograph:
    • should be done with the suspected side up
    • the lung will then 'fall' away from the chest wall
  • expiratory chest radiograph:
    • lung becomes smaller and denser
    • pneumothorax remains the same size and is thus more conspicuous : although some authors suggest that there is no difference in detection rate 6
  • CT scan

When imaged supine detection can be difficult: see pneumothorax in a supine patient, and pneumothorax is one cause of a transradiant hemithorax.


M-mode can be used to determine movement of lung within the rib-interspace. Small pneumothoraces are best appreciated anteriorly in the supine position (gas rises) whereas large pneumothoraces are appreciated laterally in the mid-axillary line.

See: ultrasound for pneumothorax


Provided lung windows are examined, a pneumothorax is very easily identified on CT, and should pose essentially no diagnostic difficulty. When a bullous disease is present, a loculated pneumothorax may appear similar.

Treatment depends on a number of factors:

  • size of the pneumothorax
  • symptoms
  • background lung disease/respiratory reserve

These can be used together to determine the best course of action.  The following guidelines are based on the British Thoracic Society guidelines for the treatment of pneumothorax; local protocol may differ:

  • asymptomatic small rim pneumothorax (<2 cm): no treatment with follow up radiology to confirm resolution
  • pneumothorax with mild symptoms (no underlying lung condition): needle aspiration in the first instance
  • pneumothorax in a patient with background chronic lung disease or significant symptoms: intercostal drain insertion (small drain using the Seldinger technique)

In patients with recurrent pneumothoraces or who are at very high risk of having recurrent events and have a poor respiratory reserve, a pleurodesis can be performed. This can either be medical (e.g. talc poudrage) or surgical (e.g. VATS pleurectomy, pleural abrasion, sclerosing agent) 4.

Usually, the diagnosis is straightforward, but occasionally other entities should be considered:

  • artefacts: air caught between structures outside the chest
    • skin fold: the apparent pleural edge is denser and may be seen extending beyond the chest cavity or seen to fade out
    • clothing
    • blankets
  • monitoring leads (although these should be obvious)
  • overlapping breast margin
  • pulmonary bullae
  • giant bullous emphysema: differentiated from tension PTX by clinical stability, interstitial vascular markings projected with the bullae and lack of hemithorax re-expansion following the insertion of an intercostal catheter
  • calcified pleural plaques
  • other gas in abnormal locations
    • pneumomediastinum
    • pneumopericardium
  • other causes of a hyperlucent hemithorax
  • On CT
    • gas in a brachiocephalic vein from cannulisation
    • beam hardening artefact from concentrated IC contrast in a brachiocephalic vein or the SVC
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Article information

rID: 4578
Systems: Chest, Trauma
Sections: Pathology, Gamuts
Synonyms or Alternate Spellings:
  • Pneumothoraces
  • Pneumothorax - general

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Cases and figures

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    Case 3: role of expiratory radiograph
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    Case 23: right PTX post malposition of nasogastric tube
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