Intrathoracic extrapleural lesions: MDCT

Transcription

1 Intrathoracic extrapleural lesions: MDCT Poster No.: C-0994 Congress: ECR 2010 Type: Educational Exhibit Topic: Chest Authors: S. S. Kim, Y. T. Kim, S. S. Jou, J. K. Han; Cheonan/KR Keywords: Thoracic wall, Pleura, CT DOI: /ecr2010/C-0994 Any information contained in this pdf file is automatically generated from digital material submitted to EPOS by third parties in the form of scientific presentations. References to any names, marks, products, or services of third parties or hypertext links to thirdparty sites or information are provided solely as a convenience to you and do not in any way constitute or imply ECR's endorsement, sponsorship or recommendation of the third party, information, product or service. ECR is not responsible for the content of these pages and does not make any representations regarding the content or accuracy of material in this file. As per copyright regulations, any unauthorised use of the material or parts thereof as well as commercial reproduction or multiple distribution by any traditional or electronically based reproduction/publication method ist strictly prohibited. You agree to defend, indemnify, and hold ECR harmless from and against any and all claims, damages, costs, and expenses, including attorneys' fees, arising from or related to your use of these pages. Please note: Links to movies, ppt slideshows and any other multimedia files are not available in the pdf version of presentations. Page 1 of 24

2 Learning objectives To classify intrathoracic extrapleural lesions, and to illustrate their imaging finding. Background The extrapleural space lies between the parietal pleura and the thoracic cage. The structures within and adjacent to this region include connective tissues, nerves, vessels, intercostal muscles and ribs. It is divided into intra- and extra-thoracic space by the innermost intercostal muscle. According to their main constituent, intrathoracic extrapleural lesions are classified into air-containing lesions, fat-containing lesions and soft tissue-containing lesions (Table 1). We classify intrathoracic extrapleural lesions and illustrate their imaging findings. Images for this section: Page 2 of 24

3 Fig. 1: Table 1. Classification of intrathoracic extrapleural lesions Page 3 of 24

4 Imaging findings OR Procedure details Anatomy of the extrapleural space and its normal CT findings The extrapleural space is defined in the normal individual by an imaginary line of cleavage in the loose connective tissue comprised of the endothoracic fascia. The line lies between the parietal pleura and the thoracic cage. External to the parietal pleura are, in ascending order of proximity: extrapleural fat, endothoracic fascia, innermost intercostal muscle, internal intercostal muscle, and external intercostal muscle. The innermost intercostal muscle passes between the internal surface of the adjacent ribs, and it divides the extrapleural space into intra- and extra-thoracic space (Fig. 1). Although the innermost intercostal muscles are incomplete in the anterior and posterior thorax, other muscles, such as the transverse thoracic and subcostal muscles, can occupy the same plane. Normal intercostal stripe is consisted of the followings: pleura, extrapleural fat, endothoracic fascia and innermost intercostal muscle. In the paravertebral region, the innermost intercostal muscle is absent, the pleura and the endothoracic fascia combine to form a thinner line than is seen laterally. Anteriorly, the transverse thoracic muscle arises from the xiphoid process or the lower sternum and is nearly always visible at MDCT (Multi-Detector CT). On the other hand, subcostal muscle covering the inner surface of the ribs is occasionally visible on MDCT (1). Fig.: 1. Intrathoracic extrapleural space on CT. Extrapleural space is divided into intraand extra-thoracic space by innermost intercostal muscle. Page 4 of 24

5 Air containing extrapleural lesions Extrapleural air caused by trauma Pleural injury is common in patients with chest trauma. Simple pneumothorax occurs in about 15~40% of patients with blunt chest trauma and in about 20% of patients with penetrating chest injuries. Hemothorax is seen in about 20%~50% of patients with blunt trauma and 60%~80% with penetrating chest injuries. Rib fracture is noted in 56% of patients with blunt trauma, which may lead to injury in the adjacent chest wall, pulmonary contusion or laceration (2). Extrapleural air is visualized as air density between the hemothorax and the ribs on MDCT (Figs. 2, 3). Fig.: 2. Extrapleural air caused by direct chest trauma in a 75-year-old man. Axial CT scan shows extrapleural air (open arrow) external to pleural hematoma (*). Page 5 of 24

6 Fig.: 3. Extrapleural air caused by direct chest trauma in a 55-year-old man. A. Chest radiograph shows extraplueral air and hematoma (open arrows). B. Axial CT scan with lung setting shows extrapleural hematoma and air (open arrows). Extrapleural extension of pneumomediastinum The commonest cause of pneumomediastinum is alveolar rupture. Any condition which produces a pressure gradient between the alveoli and the interstices can result in alveolar rupture. Alveolar rupture results in pulmonary interstitial emphysema. Small air bubbles coalesce into per vascular fascial sheaths toward the hilus, on arrival, they begin to move into the mediastinum. Air in the mediastinum can migrate into the neck, the retroperitoneum, and the extrapleural space. Therefore, pneumomediastinum is sometimes associated with unusual air collection, causing subcutaneous emphysema, epidural air in the spine and air in the extraperitoneal subpleural space (3). It is imperative to differentiate extrapleural air collection from pneumothorax. There are radiological features that distinguish extrapleural air collection from pneumothorax: (a) apical air spaces continuous with the pneumomediastinum, (b) streaky lines or networks in the air collections, probably representing dissected fibrous structures in the extrapleural space, (c) no change is seen after the patient move from the upright to supine position (4) (Fig. 4). Page 6 of 24

7 Fig.: 4. Extrapleural extension from pneumomediastinum in a 29-year-old man. Axial CT scan with lung setting shows multiple air collections (arrowheads) in extrapleural space of left hemithorax and mediastinal air. Extrapleural air has internal linear opacity, so it can be differentiated from pneumothorax. Fat containing extrapleural lesions Extrapleural fat in normal individuals All thoracic fat is extrapleural - outside the parietal pleura in the mediastinum or in the chest wall - where it is a component of the endothoracic fascia loose connective tissue. Because thoracic fat is mobile and flaccid, it can assume a variety of shapes and distributions (5). In the thorax, extrapleural fat is most abundantly located along the posterolateral aspects of the fourth to the eighth rib (6) (Figs. 5, 6). Page 7 of 24

8 Fig.: 5. Unilateral extrapleural fat in a 63-year-old woman. Axial CT scan shows prominent extrapleural fat (*) in posterior aspect of left lower lobe. Page 8 of 24

9 Fig.: 6. Focal extrapleural fat in a 74-year-old man. A. Chest radiograph shows a focal increased opacity (arrow) with extrapleural sign in the right upper lobe. B, C. Axial (B) and coronal reformatted (C) images show focal fat deposition (arrow) in the anterolateral periphery of right upper lobe. Extrapleural fat in disorders associated with volume loss Costal fat can become thickened in association with adjacent lung scarring. The thickened fat is usually band-like and external to the lung. However, if pleural tethering is extreme, costal fat can be drawn into the lung on a pedicle (5). Extrapleural fat is prominent in certain pulmonary disorders associated with volume loss, such as chronic tuberculosis, lung collapse, interstitial lung disease, chronic empyema and post-operative changes (Fig. 7). Page 9 of 24

10 Fig.: 7. Left lower lobe collapse with decreased lung volume in a 55-year-old man. Axial CT scan shows collapsed left lower lobe with traction bronchiectasis and prominent extrapleural fat (*) in the posterior aspect of left lower lobe. Soft tissue containing extrapleural lesions Soft tissue containing extrapleural lesions include hematoma, infection and tumors. Medially displaced extrapleural fat is useful in revealing extrapleural lesion and distinguishing it from pleural lesion. Extrapleural hematoma Extrapleural hematoma is a rare but life-threatening complication caused by blood collected between the parietal pleura and the endothoracic fascia. It is known to occur as a result of blunt trauma to the chest wall, ruptured aneurysm, parietal pleurectomy, sympathectomy, and central venous catheter insertion (Figs. 8, 9). Hemothorax is Page 10 of 24

11 commonly accompanied by extrapleural hematoma. It is distinguished from extrapleural hematoma by the displaced extrapleural fat (7) (Figs. 8 ~ 10). Fig.: 8. Extrapleural and pleural hematoma caused by aortic rupture in a 91-year-old man. Precontrast axial CT scan shows high attenuation hematoma (*) in left pleural cavity, separating from extrapleural hematoma by linear extrapleural fat (open arrow). Page 11 of 24

12 Fig.: 9. Extrapleural hematoma associated with rib fracture in a 32-year-old man. Precontrast axial CT scan shows extrapleural hematoma external to extrapleural fat (open arrows). Also note fracture of adjacent rib. Page 12 of 24

13 Fig.: 10. Extrapleural hematoma from chest trauma in a 57-year-old man. Precontrast CT scan shows extrapleural hematoma (*) external to extrapleural fat (arrowheads), and pleural hematoma (#) internal to extrapleural fat. Infection Although primary infection of the chest wall is rare, it can occur spontaneously or in association with diabetes mellitus, immunosuppression and trauma. Most chest wall or pleural inflammation expands into the extrapleural space (8). Chest wall abscesses may extend into the extrapleural space (Figs. 11~13). Tuberculosis (TB) of the chest wall constitutes between 1% and 5 % of all cases of musculoskeletal TB and commonly occurs with pulmonary TB. Destruction of bone adjacent to TB abscess is a common finding and result in pressure necrosis caused by granulation tissue and the direct action of the invading organisms. Chest wall TB abscess is accompanied by bony erosion and intrathoracic adenopathy (9). Page 13 of 24

14 Fig.: 11. Extrapleural extension from empyema in a 80-year-old man. Axial scan shows dirty increased attenuation (arrow) in extrapleural fat, posterior to the chronic empyema in right lower hemithorax. Also note prominent extrapleural fat (open arrows), pleural thickening, and calcification in left lower hemithorax. Page 14 of 24

15 Fig.: 12. Extrapleural extension from empyema in a 32-year-old man. Axial scan shows extrapleural fluid collection external to extrapleural fat (open arrowhead), and loculated pleural effusion (*) along right major fissure. Page 15 of 24

16 Fig.: 13. Extrapleural extension from empyema in a 61-year-old man. A, B. Axial (A) and coronal refermatted (B) images show fluid collection (*) in extrapleural space external to the enhanced pleura (open arrow) and extrapleural fat. Tumors Direct extension of a pulmonary or pleural lesion into the extrapleural space is most frequently encountered in patients with malignant tumor. The majority of chest wall tumors are rib tumors, including metastasic disease, multiple myeloma of the ribs and primary chest wall tumors such as malignant mesothelioma. Direct invasion into the extrapleural space by malignancies of the lung parenchyma can also occur (10) (Figs. 14~21). Fig.: 14. Extrapleural metastasis from colon cancer in a 37-year-old man. A. Axial image shows left paraspinal soft tissue thickening (arrow) at the lower hemithorax. B. Axial CT scan 1 year later shows slightly enlarged mass (arrow) in left paraspinal area. Page 16 of 24

17 Fig.: 15. Extrapleural metastasis from thymic carcinoma in a 35-year-old woman. A, B. Axial (a) and coronal reformatted (B) images show heterogeneous mass (arrow) in left paraspinal area. Page 17 of 24

18 Fig.: 16. Extrapleural lymph node involvement of lymphoma in a 60-year-old man. Axial CT scan shows homogeneously enhanced lymph node (arrow) in left paraspinal area. Page 18 of 24

19 Fig.: 17. Extrapleural extension from multiple myeloma in a 65-year-old man. Axial CT scan shows extrapleural mass (open arrow) from spine tumor in paraspinal area, adjacent trachea. Page 19 of 24

20 Fig.: 18. Extrapleural metastasis from lung cancer in a 68-year-old woman. A, B. Axial and coronal reformatted images show enhancing nodules (open arrows) in the extrapleural space containing extrapleural fat. Also note right pleural effusion and enhancing mass in right chest wall. Fig.: 19. Extrapleural extension from adenocarcinoma of lung in a 67-year-old man. A, B. Axial and sagittal reformatted images show dense consolidative lesion in right lower lobe. Irregular shaped enhancing mass (open arrow) in the posterior portion of consolidative lesion extends to intrathoracic extrapleural space. Page 20 of 24

21 Fig.: 20. Extrapleural metastasis from malignant pleural effusion in a 77-year-old man. A, B. Axial scans show multiple enhancing masses (open arrows) in extrapleural space containing extrapleural fat. Fig.: 21. Extrapleural and chest wall extension from malignant mesothelioma in a 64year-old man. Axial CT scan shows enhancing nodule (open arrow) in extrapleural space containing extrapleural fat. Page 21 of 24

22 Conclusion The extrapleural space lies between the parietal pleura and the thoracic cage. It is divided into intra- and extra-thoracic space by the innermost intercostal muscle. Intrathoracic extrapleural lesions are classified into air-containing lesions, fat-containing lesions and soft tissue-containing lesions according to their main constituent. It is essential for the radiologists to recognize the findings of various intrathoracic extrapleural lesions. Personal Information Page 22 of 24

23 Seung Soo Kim, M.D., Young Tong Kim, M.D., Jou Sung Sick, M.D., Han Jong Kyu M.D. Department of Radiology, Soonchunhyang University Cheonan Hospital Cheonan hospital, Soonchunhyang University Bongmyung-dong, Cheonan , Korea Tel: Fax: References 1. Im JG, Webb WR, Rosen A, Gamsu G. Costal pleura: Appearances at High-Resolution CT. Radiology 1989;171: Groskin SA. Selected topics in chest trauma. Radiology 1992;183: Lillard RL, Allen RP. The Extrapleural Air Sign in Penumomediastinum. Radiology 1965;85: Kurihara Y, Nakajima Y, Niimi H, Arakawa H, Ishikawa T. Extrapleural air collections mimicking pneumothorax: helical CT finding. J Comput Assist Tomogr 1997;21: Fisher ER, Godwin JD. Extrapleural fat collections: pseudotumors and other confusing manifestations. AJR Am J Roentgenol 1993;161: Proto AV. Conventional chest radiographs: anatomic understanding of newer observations. Radiology 1992;183: Aquino SL, Chiles C, Oaks T. Displaced extrapleural fat as revealed by CT scanning: evidence of extrapleural hematoma. AJR Am J Roentgenol 1997;169: Waite RJ, Carbonneau RJ, Balikian JP, Umali CB, Pezzella AT, Nash G. Parietal pleural changes in empyema: appearances at CT. Radiology 1990;175: Page 23 of 24

24 9. Morris BS, Maheshwari M, Chalwa A. Chest wall tuberculosis: a review of CT appearances. Br J Radiol 2004;77: Felson B. The extrapleural space. Semin Roentgenol 1977 ;12: Im JG, Webb WR, Rosen A, Gamsu G. Costal pleura: Appearances at High-Resolution CT. Radiology 1989;171: Groskin SA. Selected topics in chest trauma. Radiology 1992;183: Lillard RL, Allen RP. The Extrapleural Air Sign in Penumomediastinum. Radiology 1965;85: Kurihara Y, Nakajima Y, Niimi H, Arakawa H, Ishikawa T. Extrapleural air collections mimicking pneumothorax: helical CT finding. J Comput Assist Tomogr 1997;21: Fisher ER, Godwin JD. Extrapleural fat collections: pseudotumors and other confusing manifestations. AJR Am J Roentgenol 1993;161: Proto AV. Conventional chest radiographs: anatomic understanding of newer observations. Radiology 1992;183: Aquino SL, Chiles C, Oaks T. Displaced extrapleural fat as revealed by CT scanning: evidence of extrapleural hematoma. AJR Am J Roentgenol 1997;169: Waite RJ, Carbonneau RJ, Balikian JP, Umali CB, Pezzella AT, Nash G. Parietal pleural changes in empyema: appearances at CT. Radiology 1990;175: Morris BS, Maheshwari M, Chalwa A. Chest wall tuberculosis: a review of CT appearances. Br J Radiol 2004;77: Felson B. The extrapleural space. Semin Roentgenol 1977 ;12: Page 24 of 24