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DOI: 10.1148/rg.273065136
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Right arrow Chest Radiology

A Diagnostic Approach to Mediastinal Abnormalities1

Camilla R. Whitten, MRCS, FRCR, Sameer Khan, MRCP, FRCR, Graham J. Munneke, MRCP, FRCR, and Sisa Grubnic, MRCP, FRCR

1 From the Department of Radiology, St George’s Hospital, Blackshaw Rd, Tooting, London SW17 0QT, England. Presented as an education exhibit at the 2005 RSNA Annual Meeting. Received July 13, 2006; revision requested August 17 and received October 11; accepted October 18. All authors have no financial relationships to disclose.

Figure 1
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  		Figure 1.  Drawing illustrates the anterior mediastinum (outlined in black).

 

Figure 2A
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  		Figure 2a.  Anterior junction line. (a) Posteroanterior chest radiograph demonstrates the anterior junction line (arrow). (b) Computed tomographic (CT) scan shows the four layers of pleura that constitute the anterior junction line (arrow). The interface between aerated lung and pleura allows the line to be appreciated at conventional radiography (cf a).

 

Figure 2B
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  		Figure 2b.  Anterior junction line. (a) Posteroanterior chest radiograph demonstrates the anterior junction line (arrow). (b) Computed tomographic (CT) scan shows the four layers of pleura that constitute the anterior junction line (arrow). The interface between aerated lung and pleura allows the line to be appreciated at conventional radiography (cf a).

 

Figure 3A
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  		Figure 3a.  Hilum overlay sign in a patient with lymphoma. (a) Posteroanterior chest radiograph clearly depicts the hila (white arrow), which indicates that the mass is either anterior or posterior to the hila. In addition, the descending aorta is clearly seen (black arrow), indicating that the mass is not within the posterior mediastinum. (b) Chest CT scan demonstrates an anterior mediastinal mass. The anterior junction line is obliterated, whereas the lung interfaces with the hilar vessels (arrow) and aorta (arrowhead) are preserved.

 

Figure 3B
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  		Figure 3b.  Hilum overlay sign in a patient with lymphoma. (a) Posteroanterior chest radiograph clearly depicts the hila (white arrow), which indicates that the mass is either anterior or posterior to the hila. In addition, the descending aorta is clearly seen (black arrow), indicating that the mass is not within the posterior mediastinum. (b) Chest CT scan demonstrates an anterior mediastinal mass. The anterior junction line is obliterated, whereas the lung interfaces with the hilar vessels (arrow) and aorta (arrowhead) are preserved.

 

Figure 4A
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  		Figure 4a.  Epicardial fat pad. (a) Posteroanterior chest radiograph shows loss of the cardiac silhouette at the border of the right side of the heart and an epicardial fat pad with relatively low density (arrow). (b) CT scan shows the fat pad (arrow) as an area of homogeneous fat attenuation adjacent to the right border of the heart.

 

Figure 4B
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  		Figure 4b.  Epicardial fat pad. (a) Posteroanterior chest radiograph shows loss of the cardiac silhouette at the border of the right side of the heart and an epicardial fat pad with relatively low density (arrow). (b) CT scan shows the fat pad (arrow) as an area of homogeneous fat attenuation adjacent to the right border of the heart.

 

Figure 5A
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  		Figure 5a.  Right-sided retrosternal goiter. (a) Posteroanterior chest radiograph demonstrates a thyroid goiter (arrow) extending into the middle mediastinum, obliterating the right paratracheal stripe, and causing deviation of the trachea to the left (black arrowhead). Above the level of the clavicles, the margins of the mass are not sharp (white arrowhead), indicating that the mass has an anterior mediastinal component. (b) CT scan shows the mass (arrow) between the trachea and right lung, a location that explains the obliteration of the right paratracheal stripe seen in a. There is no contact between the anterior component of the mass and the lung (arrowhead) at the level of the clavicular heads, a relationship that continues above the level of the clavicles. This finding explains why the lateral border of the anterior mediastinal component above the level of the clavicles is not sharp in a.

 

Figure 5B
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  		Figure 5b.  Right-sided retrosternal goiter. (a) Posteroanterior chest radiograph demonstrates a thyroid goiter (arrow) extending into the middle mediastinum, obliterating the right paratracheal stripe, and causing deviation of the trachea to the left (black arrowhead). Above the level of the clavicles, the margins of the mass are not sharp (white arrowhead), indicating that the mass has an anterior mediastinal component. (b) CT scan shows the mass (arrow) between the trachea and right lung, a location that explains the obliteration of the right paratracheal stripe seen in a. There is no contact between the anterior component of the mass and the lung (arrowhead) at the level of the clavicular heads, a relationship that continues above the level of the clavicles. This finding explains why the lateral border of the anterior mediastinal component above the level of the clavicles is not sharp in a.

 

Figure 6
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  		Figure 6.  Drawing illustrates the middle mediastinum (outlined in black).

 

Figure 7A
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  		Figure 7a.  Right paratracheal stripe. (a) Posteroanterior chest radiograph shows the right paratracheal stripe (arrow). The azygos vein is seen at the inferior margin of the stripe at the tracheobronchial angle (arrowhead). (b) CT scan shows the right wall of the trachea with medial and lateral air–soft tissue interfaces caused by air within the tracheal lumen and right lung (arrow). These interfaces create the right paratracheal stripe (cf a). Note the position of the SVC (arrowhead), which explains why the paratracheal stripe is seen projecting through the SVC at radiography. (c) CT scan obtained at the level of the azygos arch shows that the azygos vein (arrow) disrupts the lung–tracheal wall interface at the tracheobronchial angle.

 

Figure 7B
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  		Figure 7b.  Right paratracheal stripe. (a) Posteroanterior chest radiograph shows the right paratracheal stripe (arrow). The azygos vein is seen at the inferior margin of the stripe at the tracheobronchial angle (arrowhead). (b) CT scan shows the right wall of the trachea with medial and lateral air–soft tissue interfaces caused by air within the tracheal lumen and right lung (arrow). These interfaces create the right paratracheal stripe (cf a). Note the position of the SVC (arrowhead), which explains why the paratracheal stripe is seen projecting through the SVC at radiography. (c) CT scan obtained at the level of the azygos arch shows that the azygos vein (arrow) disrupts the lung–tracheal wall interface at the tracheobronchial angle.

 

Figure 7C
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  		Figure 7c.  Right paratracheal stripe. (a) Posteroanterior chest radiograph shows the right paratracheal stripe (arrow). The azygos vein is seen at the inferior margin of the stripe at the tracheobronchial angle (arrowhead). (b) CT scan shows the right wall of the trachea with medial and lateral air–soft tissue interfaces caused by air within the tracheal lumen and right lung (arrow). These interfaces create the right paratracheal stripe (cf a). Note the position of the SVC (arrowhead), which explains why the paratracheal stripe is seen projecting through the SVC at radiography. (c) CT scan obtained at the level of the azygos arch shows that the azygos vein (arrow) disrupts the lung–tracheal wall interface at the tracheobronchial angle.

 

Figure 8A
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  		Figure 8a.  Lymphadenopathy. (a) On a collimated posteroanterior chest radiograph, the right paratracheal stripe is not seen, having been obliterated by a right paratracheal mass (arrowheads). (b) CT scan demonstrates right paratracheal lymphadenopathy (arrow), which obliterates the air–soft tissue interface between the right lung and the tracheal wall. This finding explains the obliteration of the right paratracheal stripe in a.

 

Figure 8B
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  		Figure 8b.  Lymphadenopathy. (a) On a collimated posteroanterior chest radiograph, the right paratracheal stripe is not seen, having been obliterated by a right paratracheal mass (arrowheads). (b) CT scan demonstrates right paratracheal lymphadenopathy (arrow), which obliterates the air–soft tissue interface between the right lung and the tracheal wall. This finding explains the obliteration of the right paratracheal stripe in a.

 

Figure 9
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  		Figure 9.  AP window reflection. On a posteroanterior chest radiograph, the AP window reflection (arrowhead) extends from the aortic knob to the left pulmonary artery and has a normal concave appearance. The aortic-pulmonary reflection (arrow) is a more anterior line and extends from the aortic arch to the level of the left main bronchus.

 

Figure 10A
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  		Figure 10a.  AP window lymphadenopathy. (a) Chest radiograph shows the AP window with an abnormal convex border (arrow). (b) CT scan demonstrates lymphadenopathy (arrow), which accounts for the distortion of the AP window in a.

 

Figure 10B
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  		Figure 10b.  AP window lymphadenopathy. (a) Chest radiograph shows the AP window with an abnormal convex border (arrow). (b) CT scan demonstrates lymphadenopathy (arrow), which accounts for the distortion of the AP window in a.

 

Figure 11A
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  		Figure 11a.  Aneurysm of the aortic arch. (a) Posteroanterior chest radiograph demonstrates the AP window with a convex border (arrow). (b) CT scan reveals an aneurysm (arrow) arising laterally from the aortic arch, a finding that accounts for the abnormality seen in a.

 

Figure 11B
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  		Figure 11b.  Aneurysm of the aortic arch. (a) Posteroanterior chest radiograph demonstrates the AP window with a convex border (arrow). (b) CT scan reveals an aneurysm (arrow) arising laterally from the aortic arch, a finding that accounts for the abnormality seen in a.

 

Figure 12A
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  		Figure 12a.  Right-sided aortic arch. (a) Posteroanterior chest radiograph demonstrates an abnormality in the right paratracheal region (arrow) with loss of the paratracheal stripe. Note, however, the absence of the aortic knuckle on the left. (b) CT scan shows a right-sided aortic arch (arrow), which explains the findings in a.

 

Figure 12B
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  		Figure 12b.  Right-sided aortic arch. (a) Posteroanterior chest radiograph demonstrates an abnormality in the right paratracheal region (arrow) with loss of the paratracheal stripe. Note, however, the absence of the aortic knuckle on the left. (b) CT scan shows a right-sided aortic arch (arrow), which explains the findings in a.

 

Figure 13A
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  		Figure 13a.  Left-sided SVC. (a) Collimated posteroanterior chest radiograph shows an additional line (arrow) lateral to the aortic arch. (b) Venogram demonstrates a left-sided SVC, which explains the finding in a. (c, d) CT scans obtained at the levels of the aortic arch (c) and pulmonary trunk (d) show the left-sided SVC (arrow), which drains into the coronary sinus.

 

Figure 13B
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  		Figure 13b.  Left-sided SVC. (a) Collimated posteroanterior chest radiograph shows an additional line (arrow) lateral to the aortic arch. (b) Venogram demonstrates a left-sided SVC, which explains the finding in a. (c, d) CT scans obtained at the levels of the aortic arch (c) and pulmonary trunk (d) show the left-sided SVC (arrow), which drains into the coronary sinus.

 

Figure 13C
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  		Figure 13c.  Left-sided SVC. (a) Collimated posteroanterior chest radiograph shows an additional line (arrow) lateral to the aortic arch. (b) Venogram demonstrates a left-sided SVC, which explains the finding in a. (c, d) CT scans obtained at the levels of the aortic arch (c) and pulmonary trunk (d) show the left-sided SVC (arrow), which drains into the coronary sinus.

 

Figure 13D
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  		Figure 13d.  Left-sided SVC. (a) Collimated posteroanterior chest radiograph shows an additional line (arrow) lateral to the aortic arch. (b) Venogram demonstrates a left-sided SVC, which explains the finding in a. (c, d) CT scans obtained at the levels of the aortic arch (c) and pulmonary trunk (d) show the left-sided SVC (arrow), which drains into the coronary sinus.

 

Figure 14A
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  		Figure 14a.  Azygos continuation of the IVC. (a) Collimated posteroanterior chest radiograph shows enlargement of the azygos vein at the inferior margin of the right paratracheal stripe (arrowheads), a finding that mimics lymphadenopathy. (b) CT scan also shows enlargement of the azygos vein (arrow). This finding is the result of azygos continuation of the IVC.

 

Figure 14B
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  		Figure 14b.  Azygos continuation of the IVC. (a) Collimated posteroanterior chest radiograph shows enlargement of the azygos vein at the inferior margin of the right paratracheal stripe (arrowheads), a finding that mimics lymphadenopathy. (b) CT scan also shows enlargement of the azygos vein (arrow). This finding is the result of azygos continuation of the IVC.

 

Figure 15
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  		Figure 15.  Drawing illustrates the posterior mediastinum (outlined in black).

 

Figure 16A
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  		Figure 16a.  Azygoesophageal recess reflection. (a) Posteroanterior chest radiograph shows the azygoesophageal line (arrowheads). (b) CT scan shows the azygoesophageal recess (white arrow) formed by the esophagus anteriorly (black arrow) and the azygos vein posteriorly (arrowhead). The azygoesophageal line in a represents the interface between this recess and the lung.

 

Figure 16B
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  		Figure 16b.  Azygoesophageal recess reflection. (a) Posteroanterior chest radiograph shows the azygoesophageal line (arrowheads). (b) CT scan shows the azygoesophageal recess (white arrow) formed by the esophagus anteriorly (black arrow) and the azygos vein posteriorly (arrowhead). The azygoesophageal line in a represents the interface between this recess and the lung.

 

Figure 17A
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  		Figure 17a.  Bronchogenic cyst. (a) Posteroanterior chest radiograph demonstrates a subcarinal abnormality with increased opacity (*), splaying of the carina, and abnormal convexity of the upper and middle thirds of the azygoesophageal line (arrowheads). (b) Corresponding CT scan helps confirm a subcarinal mass (arrow), which proved to be a bronchogenic cyst.

 

Figure 17B
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  		Figure 17b.  Bronchogenic cyst. (a) Posteroanterior chest radiograph demonstrates a subcarinal abnormality with increased opacity (*), splaying of the carina, and abnormal convexity of the upper and middle thirds of the azygoesophageal line (arrowheads). (b) Corresponding CT scan helps confirm a subcarinal mass (arrow), which proved to be a bronchogenic cyst.

 

Figure 18A
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  		Figure 18a.  (a) Collimated posteroanterior chest radiograph shows the posterior junction line (arrow) projecting through the tracheal air column. (b) CT scan shows the posterior junction line (arrow), which is formed by the interface between the lungs posterior to the mediastinum and consists of four pleural layers.

 

Figure 18B
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  		Figure 18b.  (a) Collimated posteroanterior chest radiograph shows the posterior junction line (arrow) projecting through the tracheal air column. (b) CT scan shows the posterior junction line (arrow), which is formed by the interface between the lungs posterior to the mediastinum and consists of four pleural layers.

 

Figure 19A
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  		Figure 19a.  Bronchogenic cyst. (a) Posteroanterior chest radiograph shows a mass (arrow) obliterating the posterior junction line. Note that the mass extends above the level of the clavicle and has a well-demarcated outline due to the interface with adjacent lung (arrowhead). (b) CT scan helps confirm the posterior location of the mass (arrow), which proved to be a bronchogenic cyst.

 

Figure 19B
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  		Figure 19b.  Bronchogenic cyst. (a) Posteroanterior chest radiograph shows a mass (arrow) obliterating the posterior junction line. Note that the mass extends above the level of the clavicle and has a well-demarcated outline due to the interface with adjacent lung (arrowhead). (b) CT scan helps confirm the posterior location of the mass (arrow), which proved to be a bronchogenic cyst.

 

Figure 20A
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  		Figure 20a.  (a) On a collimated posteroanterior chest radiograph, the left paraspinal line (arrow) is seen separate and distinct from the vertebral body (black arrowhead) and the descending thoracic aorta (white arrowhead). (b) CT scan shows the left paraspinal line. The descending aorta holds the pleural reflection (arrow) away from the vertebral body, which allows the lung–soft tissue interface to be more tangential to the x-ray beam and therefore visualized as a line. (c) Collimated posteroanterior radiograph shows the right paraspinal line (arrow).

 

Figure 20B
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  		Figure 20b.  (a) On a collimated posteroanterior chest radiograph, the left paraspinal line (arrow) is seen separate and distinct from the vertebral body (black arrowhead) and the descending thoracic aorta (white arrowhead). (b) CT scan shows the left paraspinal line. The descending aorta holds the pleural reflection (arrow) away from the vertebral body, which allows the lung–soft tissue interface to be more tangential to the x-ray beam and therefore visualized as a line. (c) Collimated posteroanterior radiograph shows the right paraspinal line (arrow).

 

Figure 20C
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  		Figure 20c.  (a) On a collimated posteroanterior chest radiograph, the left paraspinal line (arrow) is seen separate and distinct from the vertebral body (black arrowhead) and the descending thoracic aorta (white arrowhead). (b) CT scan shows the left paraspinal line. The descending aorta holds the pleural reflection (arrow) away from the vertebral body, which allows the lung–soft tissue interface to be more tangential to the x-ray beam and therefore visualized as a line. (c) Collimated posteroanterior radiograph shows the right paraspinal line (arrow).

 

Figure 21A
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  		Figure 21a.  Paraspinal abscess. (a) Posteroanterior chest radiograph shows a mass (arrow) effacing the left paraspinal line. The lateral wall of the descending aorta is seen as a separate entity (arrowhead). (b) CT scan shows a paraspinal abscess (arrow) effacing the paraspinal lines. The air–soft tissue interface between the lung and aorta remains intact (arrowhead), thereby preserving the normal radiographic appearance of the lateral aortic wall (cf a).

 

Figure 21B
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  		Figure 21b.  Paraspinal abscess. (a) Posteroanterior chest radiograph shows a mass (arrow) effacing the left paraspinal line. The lateral wall of the descending aorta is seen as a separate entity (arrowhead). (b) CT scan shows a paraspinal abscess (arrow) effacing the paraspinal lines. The air–soft tissue interface between the lung and aorta remains intact (arrowhead), thereby preserving the normal radiographic appearance of the lateral aortic wall (cf a).

 

Figure 22A
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  		Figure 22a.  Descending aortic aneurysm. (a) Posteroanterior chest radiograph shows lateral displacement of the lateral margin of the descending thoracic aorta due to an aortic aneurysm (arrowheads). (b) CT scan also demonstrates the aneurysm (arrow).

 

Figure 22B
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  		Figure 22b.  Descending aortic aneurysm. (a) Posteroanterior chest radiograph shows lateral displacement of the lateral margin of the descending thoracic aorta due to an aortic aneurysm (arrowheads). (b) CT scan also demonstrates the aneurysm (arrow).

 

Figure 23A
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  		Figure 23a.  Neurogenic tumor. (a) Posteroanterior chest radiograph shows a small mass (arrow) disrupting the left paraspinal line inferiorly. (b) Coronal T2-weighted magnetic resonance (MR) image helps confirm a left paraspinal mass (arrow).

 

Figure 23B
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  		Figure 23b.  Neurogenic tumor. (a) Posteroanterior chest radiograph shows a small mass (arrow) disrupting the left paraspinal line inferiorly. (b) Coronal T2-weighted magnetic resonance (MR) image helps confirm a left paraspinal mass (arrow).

 




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