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Pneumothorax Imaging

  • Author: Fahad M Al-Hameed, MD, AmBIM, FCCP, FRCPC; Chief Editor: Eugene C Lin, MD  more...
 
Updated: Oct 04, 2015
 

Overview

Pneumothorax, the presence of air within the pleural space, is considered to be one of the most common forms of thoracic disease. It is classified as spontaneous (not caused by trauma), traumatic, or iatrogenic (see the images below).[1, 2, 3, 4]

A large, right-sided pneumothorax has occurred fro A large, right-sided pneumothorax has occurred from a rupture of a subpleural bleb.
A true pneumothorax line. Note that the visceral p A true pneumothorax line. Note that the visceral pleural line is observed clearly, with the absence of vascular marking beyond the pleural line.

Spontaneous pneumothorax may be either primary (occurring in persons without clinically or radiologically apparent lung disease) or secondary (in which lung disease is present and apparent). Most individuals with primary spontaneous pneumothorax (PSP) have unrecognized lung disease; many observations suggest that spontaneous pneumothorax often results from rupture of a subpleural bleb.

Traumatic pneumothorax is caused by penetrating or blunt trauma to the chest, with air entering the pleural space directly through the chest wall, through visceral pleural penetration, or through alveolar rupture resulting from sudden compression of the chest.

Iatronic pneumothorax results from a complication of a diagnostic or therapeutic intervention. With the increasing use of invasive diagnostic procedures, iatrogenic pneumothorax likely will become more common, although most cases are of little clinical significance.

Complications of pneumothorax

In most reported series, the rate of recurrence of spontaneous pneumothorax on the same side is as much as 30%; on the contralateral side, the rate of recurrence is approximately 10%.

Other complications include the following:

  • Reexpansion pulmonary edema
  • Bronchopleural fistula - Occurs in 3-5% of patients
  • Pneumomediastinum and pneumopericardium

Tension pneumothorax may occur after spontaneous pneumothorax, although it is more common after traumatic pneumothorax or with mechanical ventilation.

Preferred examination

Chest radiography is the first investigation performed to assess pneumothorax, because it is simple, inexpensive, rapid, and noninvasive; however, it is much less sensitive than chest computed tomography (CT) scanning in detecting blebs or bullae or a small pneumothorax.[5, 6, 7, 8, 9, 10, 11, 4, 12, 13]

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Radiography

The diagnosis of pneumothorax is established by demonstrating the outer margin of the visceral pleura (and lung), known as the pleural line, separated from the parietal pleura (and chest wall) by a lucent gas space devoid of pulmonary vessels. The pleural line appears in the image below).

A true pneumothorax line. Note that the visceral p A true pneumothorax line. Note that the visceral pleural line is observed clearly, with the absence of vascular marking beyond the pleural line.

The pleural line may be difficult to detect with a small pneumothorax unless high-quality posteroanterior and lateral chest films are obtained and viewed under a bright light. A skin fold may mimic the pleural line; usually, the patient is asymptomatic (see the image below).

Note that although a skin fold can mimic a subtle Note that although a skin fold can mimic a subtle pneumothorax, lung markings are visible beyond the skin fold.

In erect patients, pleural gas collects over the apex, and the space between the lung and the chest wall is most notable at that point (see the image below).

A large, right-sided pneumothorax has occurred fro A large, right-sided pneumothorax has occurred from a rupture of a subpleural bleb.

In the supine position, the juxtacardiac area, the lateral chest wall, and the subpulmonic region are the best areas to search for evidence of pneumothorax (see the image below). The presence of a deep costophrenic angle on a supine film may be the only sign of pneumothorax; this has been termed the deep sulcus sign.

Deep sulcus sign in a supine patient in the ICU. T Deep sulcus sign in a supine patient in the ICU. The pneumothorax is subpulmonic.

When a suggested pneumothorax is not definitively observed on an inspiratory film, an expiratory film may be helpful. At end expiration, the constant volume of the pneumothorax gas is accentuated by the reduction of the hemithorax, and the pneumothorax is recognized more easily. Similar accentuation may be obtained with lateral decubitus studies of the appropriate side (for a possible left pneumothorax, a right lateral decubitus film of the chest should be obtained, with the beam centered over the left lung).

The most common radiographic manifestations of tension pneumothorax are mediastinal shift, diaphragmatic depression, and rib cage expansion (see the image below).

An older man admitted to ICU postoperatively. Note An older man admitted to ICU postoperatively. Note the right-sided pneumothorax induced by the incorrectly positioned small-bowel feeding tube in the right-sided bronchial tree. Marked depression of the right hemidiaphragm is noted, and mediastinal shift is to the left side, suggestive of tension pneumothorax. The endotracheal tube is in a good position.

Any significant degree of displacement of the mediastinum from the midline position on maximum inspiration, as well as any depression of the diaphragm, should be taken as evidence of tension (see the image below), although a definite diagnosis of tension pneumothorax is difficult to make on the basis of radiographic findings. The degree of lung collapse is an unreliable sign of tension, since underlying lung disease may prevent collapse even in the presence of tension.

Right main stem intubation resulting in left-sided Right main stem intubation resulting in left-sided tension pneumothorax, right mediastinal shift, deep sulcus sign, and subpulmonic pneumothorax

Pleural effusions occur coincident with pneumothorax in 20–25% of patients, but they usually are quite small. Hemopneumothorax occurs in 2–3% of patients with spontaneous pneumothorax. Bleeding is believed to represent rupture or tearing of vascular adhesions between the visceral and parietal pleura as the lung collapses.

False positives/negatives

Differentiating the pleural line of a pneumothorax from that of a skin fold, clothing, tubing, or chest wall artifact is important. Careful inspection of the film may reveal that the artifact extends beyond the thorax or that lung markings are visible beyond the apparent pleural line. In the absence of underlying lung disease, the pleural line of a pneumothorax usually parallels the shape of the chest wall (see the images below).

A true pneumothorax line. Note that the visceral p A true pneumothorax line. Note that the visceral pleural line is observed clearly, with the absence of vascular marking beyond the pleural line.
Note that although a skin fold can mimic a subtle Note that although a skin fold can mimic a subtle pneumothorax, lung markings are visible beyond the skin fold.

Artifactual densities usually do not parallel the course of the chest wall over their entire length. Avascular bullae or thin-walled cysts may be mistaken for a pneumothorax. The pleural line caused by a pneumothorax usually is bowed at the center toward the lateral chest wall. Unlike in pneumothorax, the inner margins of bullae or cysts usually are concave rather than convex and do not conform exactly to the contours of the costophrenic sulcus. A pneumothorax with a pleural adhesion also may simulate bullae or lung cysts.

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Computed Tomography

CT scanning of the chest is being used with increasing frequency in patients with pneumothorax. CT may be necessary to diagnose pneumothorax in critically ill patients in whom upright or decubitus films are not possible.

As indicated in a study by Warner et al, CT scanning may prove helpful in predicting the rate of recurrence in patients with spontaneous pneumothorax. The authors found that patients with larger or more numerous blebs, as demonstrated on thoracic CT, are more likely to experience recurrences.[8]

CT demonstrates focal areas of emphysema in more than 80% of patients with spontaneous pneumothorax, even in lifelong nonsmokers. These areas are situated predominantly in the peripheral regions of the apex of the upper lobes. (In patients in whom emphysema is not apparent on CT, it often is evident at surgery or on pathologic examination.)

Degree of confidence

In a study by Mitlehner et al of 35 patients with PSP, localized emphysema with or without bulla formation was identified on CT in 31 patients (89%) and on radiographs in 15 patients (43%).[5] Abnormal findings were observed in the lung ipsilateral to the pneumothorax on 28 CT scans (80%) and on 11 chest radiographs (31%); abnormal findings were observed in the contralateral lung on 23 CT scans (66%) and on 4 chest radiographs (11%). In most patients, the abnormal findings consisted of a few localized areas of emphysema (n < 5) measuring less than 2 cm in diameter.

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Contributor Information and Disclosures
Author

Fahad M Al-Hameed, MD, AmBIM, FCCP, FRCPC Chairman, Intensive Care Department, Director, Ambulatory Care Center (Services), Professor Associate of Medicine/Critical Care, College of Medicine, King Saud Ben Abdulaziz University for Health Sciences; Consultant in Critical Care and Pulmonary Medicine, King Khalid National Guard Hospital, King Abdulaziz Medical City, Saudi Arabia

Fahad M Al-Hameed, MD, AmBIM, FCCP, FRCPC is a member of the following medical societies: American College of Chest Physicians, American Thoracic Society, Canadian Medical Association, Royal College of Physicians and Surgeons of Canada, Saudi Association for Venous Thrombo-Embolism

Disclosure: Nothing to disclose.

Coauthor(s)

Sat Sharma, MD, FRCPC Professor and Head, Division of Pulmonary Medicine, Department of Internal Medicine, University of Manitoba; Site Director, Respiratory Medicine, St Boniface General Hospital

Sat Sharma, MD, FRCPC is a member of the following medical societies: American Academy of Sleep Medicine, American College of Chest Physicians, American College of Physicians-American Society of Internal Medicine, American Thoracic Society, Canadian Medical Association, Royal College of Physicians and Surgeons of Canada, Royal Society of Medicine, Society of Critical Care Medicine, World Medical Association

Disclosure: Nothing to disclose.

Bruce Maycher, MD 

Bruce Maycher, MD is a member of the following medical societies: American Roentgen Ray Society, Canadian Medical Association, Radiological Society of North America, Society of Thoracic Radiology

Disclosure: Nothing to disclose.

Specialty Editor Board

Bernard D Coombs, MB, ChB, PhD Consulting Staff, Department of Specialist Rehabilitation Services, Hutt Valley District Health Board, New Zealand

Disclosure: Nothing to disclose.

W Richard Webb, MD Professor, Department of Radiology, University of California, San Francisco, School of Medicine

Disclosure: Nothing to disclose.

Chief Editor

Eugene C Lin, MD Attending Radiologist, Teaching Coordinator for Cardiac Imaging, Radiology Residency Program, Virginia Mason Medical Center; Clinical Assistant Professor of Radiology, University of Washington School of Medicine

Eugene C Lin, MD is a member of the following medical societies: American College of Nuclear Medicine, American College of Radiology, Radiological Society of North America, Society of Nuclear Medicine and Molecular Imaging

Disclosure: Nothing to disclose.

Additional Contributors

Satinder P Singh, MD, FCCP Professor of Radiology and Medicine, Chief of Cardiopulmonary Radiology, Director of Cardiac CT, Director of Combined Cardiopulmonary and Abdominal Radiology, Department of Radiology, University of Alabama at Birmingham School of Medicine

Disclosure: Nothing to disclose.

References
  1. Light RW. Pleural Diseases. 3rd ed. Baltimore: Williams & Wilkins. 1995.

  2. Sahn SA, Heffner JE. Spontaneous pneumothorax. N Engl J Med. 2000 Mar 23. 342(12):868-74. [Medline].

  3. Tschopp JM, Rami-Porta R, Noppen M, Astoul P. Management of spontaneous pneumothorax: state of the art. Eur Respir J. 2006 Sep. 28(3):637-50. [Medline].

  4. Soccorso G, Anbarasan R, Singh M, Lindley RM, Marven SS, Parikh DH. Management of large primary spontaneous pneumothorax in children: radiological guidance, surgical intervention and proposed guideline. Pediatr Surg Int. 2015 Aug 26. [Medline].

  5. Mitlehner W, Friedrich M, Dissmann W. Value of computer tomography in the detection of bullae and blebs in patients with primary spontaneous pneumothorax. Respiration. 1992. 59(4):221-7. [Medline].

  6. Lesur O, Delorme N, Fromaget JM, et al. Computed tomography in the etiologic assessment of idiopathic spontaneous pneumothorax. Chest. 1990 Aug. 98(2):341-7. [Medline].

  7. Slater A, Goodwin M, Anderson KE, Gleeson FV. COPD can mimic the appearance of pneumothorax on thoracic ultrasound. Chest. 2006 Mar. 129(3):545-50. [Medline].

  8. Warner BW, Bailey WW, Shipley RT. Value of computed tomography of the lung in the management of primary spontaneous pneumothorax. Am J Surg. 1991 Jul. 162(1):39-42. [Medline].

  9. Barnes TW, Morgenthaler TI, Olson EJ, Hesley GK, Decker PA, Ryu JH. Sonographically guided thoracentesis and rate of pneumothorax. J Clin Ultrasound. 2005 Dec. 33(9):442-6. [Medline].

  10. Chung MJ, Goo JM, Im JG, Cho JM, Cho SB, Kim SJ. Value of high-resolution ultrasound in detecting a pneumothorax. Eur Radiol. 2005 May. 15(5):930-5. [Medline].

  11. Reissig A, Kroegel C. Accuracy of transthoracic sonography in excluding post-interventional pneumothorax and hydropneumothorax. Comparison to chest radiography. Eur J Radiol. 2005 Mar. 53(3):463-70. [Medline].

  12. Quick JA, Uhlich RM, Ahmad S, Barnes SL, Coughenour JP. In-flight ultrasound identification of pneumothorax. Emerg Radiol. 2015 Sep 25. [Medline].

  13. Kumar S, Agarwal R, Aggarwal AN, Gupta D, Jindal SK. Role of ultrasonography in the diagnosis and management of pneumothorax following transbronchial lung biopsy. J Bronchology Interv Pulmonol. 2015 Jan. 22 (1):14-9. [Medline].

 
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A large, right-sided pneumothorax has occurred from a rupture of a subpleural bleb.
A true pneumothorax line. Note that the visceral pleural line is observed clearly, with the absence of vascular marking beyond the pleural line.
Note that although a skin fold can mimic a subtle pneumothorax, lung markings are visible beyond the skin fold.
Deep sulcus sign in a supine patient in the ICU. The pneumothorax is subpulmonic.
An older man admitted to ICU postoperatively. Note the right-sided pneumothorax induced by the incorrectly positioned small-bowel feeding tube in the right-sided bronchial tree. Marked depression of the right hemidiaphragm is noted, and mediastinal shift is to the left side, suggestive of tension pneumothorax. The endotracheal tube is in a good position.
Right main stem intubation resulting in left-sided tension pneumothorax, right mediastinal shift, deep sulcus sign, and subpulmonic pneumothorax
Pneumomediastinum from barotrauma may result in tension pneumothorax and obstructive shock.
A patient in ICU developed pneumopericardium as a manifestation of barotrauma.
 
 
 
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