A pneumothorax refers to the presence of gas in the pleural space. When this collection is constantly enlarging with resulting compression of mediastinal structures it is known as a tension pneumothorax, a life threatening emergency. It is discussed separately.
Clearly with so many causes of a pneumothorax it is impossible to generalise the epidemiology, however in general 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. If tension, presentation may be with cardiac arrest, distended neck veins and tracheal deviation.
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, dyspnea 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
A primary spontaneous pneumothorax is one which occurs in a patient with no known underlying lung disease.
When the underlying lung is abnormal, a pneumothorax is referred to as secondary spontaneous. There are many pulmonary diseases which predispose to pneumothorax including:
- cystic lung disease
- parenchymal necrosis
Iatrogenic / traumatic
Iatrogenic / traumatic causes include 1-4:
- percutaneous biopsy
- barotrama, ventilator
- radiofrequency (RF) ablation of lung mass
- pulmonary laceration
- tracheobroncial rupture
- acupuncture (some would argue that this is iatrogenic I suppose. It depends on your view of acupuncture)
A pneumothorax is, when looked for, usually relatively easily appreciated. Typically they demonstrate:
- visible visceral pleural edge see 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
- the lung may completely collapse
- the mediastinum should not shift away form the pneumothorax unless a tension pneumothorax is present (discussed separately).
- subcutaneous emphysema and pneumomediastinum may also be present
In cases where these features are not clearly present a number of techniques can be employed:
- lateral decubitus x-ray:
- should be done with the suspected side up
- the lung will then 'fall' away from the chest wall
- expiratory chest x-ray
- lung becomes smaller and denser
- pneumothorax remains the same size and is thus more conspicuous : although some authors suggest that there no difference in detection rate 6.
- CT scan
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.
Provided lung windows are examined, a pneumothroax is very easily identified on CT, and should pose essentially no diagnostic difficulty. When bullous disease is present, a loculated pneumothorax may appear similar.
Treatment and prognosis
Treatment depends on a number of factors :
- size of the pneumothorax
- background lung disease / respiratory reserve
These can be use 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 (< 2cm) : 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 poor respiratory reserve, a pleurodesis can be performed. This can either be medical (e.g. talk poudrage) or surgical (e.g. VATS pleurectomy, pleural abrasion, sclerosing agent)4.
Usually the diagnosis is straight forward, but occasionally other entities should be considered:
- skin-fold: the apparent pleural edge is denser and may be seen extending beyond the chest cavity or seen to fade out
- pulmonary bullae
- other causes of a hyperlucent hemithorax
- 1. Lee CC, Lee SH, Chang IJ et-al. Spontaneous pneumothorax associated with ankylosing spondylitis. Rheumatology (Oxford). 2005;44 (12): 1538-41. doi:10.1093/rheumatology/kei077 - Pubmed citation
- 2. Downey DB, Towers MJ, Poon PY et-al. Pneumoperitoneum with catamenial pneumothorax. AJR Am J Roentgenol. 1990;155 (1): 29-30. AJR Am J Roentgenol (citation) - Pubmed citation
- 3. Hiraki T, Mimura H, Gobara H et-al. Incidence of and risk factors for pneumothorax and chest tube placement after CT fluoroscopy-guided percutaneous lung biopsy: retrospective analysis of the procedures conducted over a 9-year period. AJR Am J Roentgenol. 2010;194 (3): 809-14. doi:10.2214/AJR.09.3224 - Pubmed citation
- 4. Shields TW. General Thoracic Surgery. Lippincott Williams & Wilkins. (2009) ISBN:0781779820. Read it at Google Books - Find it at Amazon
- 5. Kazerooni EA, Gross BH. Cardiopulmonary imaging. Lippincott Williams & Wilkins. (2004) ISBN:0781736552. Read it at Google Books - Find it at Amazon
- 6. Seow A, Kazerooni EA, Pernicano PG et-al. Comparison of upright inspiratory and expiratory chest radiographs for detecting pneumothoraces. AJR Am J Roentgenol. 1996;166 (2): 313-6. AJR Am J Roentgenol (abstract) - Pubmed citation
- 7. Beres RA, Goodman LR. Pneumothorax: detection with upright versus decubitus radiography. Radiology. 1993;186 (1): 19-22. Radiology (abstract) - Pubmed citation
- 8. Rowan KR, Kirkpatrick AW, Liu D et-al. Traumatic pneumothorax detection with thoracic US: correlation with chest radiography and CT--initial experience. Radiology. 2002;225 (1): 210-4. Radiology (citation) - Pubmed citation
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