On the PA chest-film it is important to examine all the areas where the lung borders the diaphragm, the heart and other mediastinal structures. Show
At these borders lung-soft tissue interfaces are seen resulting in a:
These lines and silhouettes are useful localizers of disease, because they can be displaced or obscured with loss of the normal silhouette. This is called the silhouette sign, which we will discuss later. The paraspinal line may be displaced by a paravertebral abscess, hemorrhage due to a fracture or extravertebral extension of a neoplasm. Widening of the paratracheal line (> 2-3mm) may be due to lymphadenopathy, pleural thickening, hemorrhage or fluid overload and heart failure. Displacement of the para-aortic line can be due to elongation of the aorta, aneurysm, dissection and rupture. The anterior and posterior junction lines are formed where the upper lobes join anteriorly and posteriorly. These are usely not well seen and we will not discuss them. An important mediastinal-lung interface to look for is the azygoesophageal line or recess (arrow). Azygo-esophageal recessThe azygo-esophageal recess is the region inferior to the level of the azygos vein arch in which the right lung forms an interface with the mediastinum between the heart anteriorly and vertebral column posteriorly. Deviation of the azygoesophageal line is caused by:
Notice the deviation of the azygoesophageal line on the PA-film. It is caused by a hiatal hernia. Vena azygos lobeA common normal variant is the azygos lobe. The azygos lobe is created when a laterally displaced azygos vein makes a deep fissure in the upper part of the lung. On a chest film it is seen as a fine line that crosses the apex of the right lung. Here another patient with an azygos lobe. In some patients an extra joint is seen in the anterior part of the first rib at the point where the bone meets the calcified cartilageneous part (arrow). This may simulate a lung mass. Pectus excavatumIn patients with a pectus excavatum the right heart border can be ill-defined, but this is normal. The lateral view is helpful in such cases. Pectus excavatum is a congenital deformity of the ribs and the sternum producing a concave appearance of the anterior chest wall. Lateral viewOn a normal lateral view the contours of the heart are visible and the IVC is seen entering the right atrium. The retrosternal space contains air and should be radiolucent down to the level where the right ventricle borders the sternum (small black arrow). As you go from superior to inferior over the vertebral bodies they should get darker, because usually there will be less soft tissue and more radiolucent lung tissue (white arrow). Diaphragm The contours of the left and right diaphragm should be visible. The right diaphragm should be visible all the way to the anterior chest wall (red arrow). The left diaphragm can only be seen to a point where it borders the heart (blue arrow). Pulmonary vessels The left main pulmonary artery (in purple) passes over the left main bronchus and is higher than the right pulmonary artery (in blue) which passes in front of the right main bronchus. Once you know how the normal hilar structures look like on a lateral view, it is easier to detect abnormalities. In this case on the PA-view there is hilar enlargement. This patient has sarcoidosis. On the lateral view spondylosis may mimick a lung mass. Any density in the area of the vertebral bodies should lead you to the PA-film to look for spondylosis, which is usually located on the right side (arrows). On the PA-view the superior mediastinum is widened. This was a Hodgkins lymphoma. A common incidental finding in adults is a Bochdalek hernia, which is due to a congenital defect in the posterior diaphragm (arrows). Large hernias are sometimes seen in neonates and can be complicated by pulmonary hypoplasia. A hernia of Morgagni is also a congenital diaphragmatic hernia, but is less common. Systematic ApproachWhenever you review a chest x-ray, always use a systematic approach. You have to know the normal anatomy and variants. Old filmsIt is extremely important to always compare with old films, as we will demonstrate in this case. First study the chest films. Continue with the old film... Scroll back and forth to the old film.
Silhouette signThe loss of the normal silhouette of a structure is called the silhouette sign. Here an illustration to explain the silhouette sign:
Silhouette sign (2) The PA-film shows a silhouette sign of the left heart border. Silhouette sign (3) Here a consolidation which is located in the left lower lobe (yellow arrow). The absence of a silhouette sign tells us that the pathology is located in the left lower lobe and not in the lingula. Silhouette sign (4) On this lateral film there is too much density over the lower part of the spine. Then click on the image to enlarge and scroll through the images. By only looking at the interfaces of the left and right diaphragm on the lateral film, it is possible to tell on which side the pathology is located. In this case we cannot follow the contour of the right diaphragm all the way to posterior, which indicates that there is something of water-density in the right lower lobe. Continue with the PA-film of the same patient... On the PA-film there is a normal silhouette of the right heart border, so the pathology is not in the anterior part of the chest, which we already had decided by studying the lateral view. Question: Answer: Hidden areasThere are some areas that need special attention, because pathology in these areas can easily be overlooked. These areas are also known as the hidden areas:
Notice that there is quite some lung volume below the dome of the diaphragm, which will need your attention (blue area). Hidden areas (2) Here an example of a large lesion in the right lower lobe, which is difficult to detect on the PA-film, unless when you give special attention to the hidden areas. Click on the image for an enlarged view. Hidden areas (3) Here a pneumonia which was hidden in the right lower lobe mainly below the level of the dome of the diaphragm (yellow arrow). Notice the increase in density on the lateral film in the lower vertebral region. You may have to enlarge the image to get a better view. Hidden areas (4) First study the CXR. Notice the subtle increased density in the area behind the heart that needs special attention (blue area). First study the CXR. We know that in some cases there is an extra joint in the anterior part of the first rib which may simulate a mass. In this case a small lung cancer is seen behind the left first rib. Continue with the PET-CT. The PET-CT demonstrates the tumor (arrow) which has already spread to the bone and liver. First study the CXRs. There is a subtle consolidation in the left lower lobe in the hidden area behind the heart. Heart and PericardiumOn a chest film only the outer contours of the heart are seen. Left Atrium
Right Atrium
Left Ventricle
Right Ventricle
Left Atrium
Left Ventricle
Right Ventricle
Left Atrium enlargement Extreme dilatation of the left atrium has resulted in bulging of the contours (blue and black arrows). Right ventricle enlargement On these chest films the heart is extremely dilated. There is a small aortic knob (blue arrow), while the pulmonary trunk and the right lower pulmonary artery are dilated. The location of the cardiac valves is best determined on the lateral radiograph. On this lateral view you can get a good impression of the enlargement of the left atrium. Cardiac incisuraClick image to enlarge. On the right side of the chest the lung will lie against the anterior chest wall. This causes a density on the anteroinferior side on the lateral view which can have many forms. The explanation for the cardiac incisura is seen on this CT-image. Pacemaker A third lead is seen, which is guided through the coronary sinus towards the left ventricle. More on cardiac pacemakers... Pericardial effusionWhenever we encounter a large heart figure, we should always be aware of the possibility of pericardial effusion simulating a large heart. On the chest x-ray it looks as if this patient has a dilated heart while on the CT it is clear, that it is the pericardial effusion that is responsible for the enlarged heart figure. Especially in patients who had recent cardiac surgery an enlargement of the heart figure can indicate pericardial bleeding. This patient had a change in the heart configuration and pericardial bleeding was suspected. There is a large pericardial effusion, which is located posteriorly to the left ventricle (blue arrow). Notice that on the anterior side there is only a minimal collection of pericardial fluid, which explains why the ultrasound examination underestimated the amount of pericardial fluid. Here another patient who had valve-replacement. Notice the large heart size. Continue with the CT. The CT-image shows a large pericardial effusion. Always compare these post-operative chest films with the pre-operative ones. CalcificationsDetection of calcifications within the heart is quite common. Here we see pericardial calcifications which can be associated with constrictive pericarditis. In this case there are calcifications that look like pericardial calcifications, but these are myocardial calcifications in an infarcted area of the left ventricle. Notice that they follow the contour of the left ventricle. Pericardial fatpadPericardial fat depositions are common. Necrosis of the fat pad has pathologic features similar to fat necrosis in . Pericardial cystPericardial cysts are connected to the pericardium and usually contain clear fluid. On the chest x-ray it seems as if there is a elevated left hemidiaphragm. On CT however there is a cyst connected to the pericardium. HiliThe normal hilar shadow is for 99% composed of vessels - pulmonary arteries and to a lesser extent veins (1). The left pulmonary artery runs over the left main bronchus, while the right pulmonary artery runs in front of the right main bronchus, which is usually lower in position than the left main bronchus. Hence the left hilum is higher than the right. In this illustration the lower lobe arteries are coloured blue because they contain oxygen-poor blood. They have a more vertical orientation, while the pulmonary veins run more horizontally towards the left atrium, which is located below the level of the main pulmonary arteries. Both pulmonary arteries and veins can be identified on a lateral view and should not be mistaken for lymphadenopathy. Sometimes the pulmonary veins can be very prominent. The left main pulmonary artery passes over the left main bronchus and is higher than the right pulmonary artery which passes in front of the right main bronchus. These images are thick slab sagittal reconstructions of a chest-ct to get a better view of the hilar structures. The lower lobe pulmonary arteries extend inferiorly from the hilum. On the right side the little finger will be visible in 94% of normal CXRs and on the left side in 62% of normals (1). Study the CXR of a 70-year old male who fell from the stairs and has severe pain on the right flank.. Notice on the PA-film the absence of the little finger on the right and on the lateral view the increased density over the lower vertebral column. What is your diagnosis? There is a right lower lobe atelectasis. Notice the abnormal right border of the heart. On a follow-up chest film the atelectasis has resolved. Notice the reappearance of the right little finger (red arrow) and the normal right heart border (blue arrow). Hilar enlargementThe table summarizes the causes of hilar enlargement. Normal hili are:
Enlargement of the hili is usually due to lymphadenopathy or enlarged vessels. In this case there is an enlarged hilar shadow on both sides. This is known as the 1-2-3 sign in sarcoidosis, i.e. enlargement of left hilum, right hilum and paratracheal. Here some more examples of sarcoidosis.
MediastinumMediastinal masses are discussed in more detail in Mediastinal masses. Here is just a brief overview. The mediastinum can be divided into an anterior, middle and posterior compartment, each with it's own pathology. Mediastinal linesMediastinal lines or stripes are interfaces between the soft tissue of mediastinal structures and the lung. Azygoesophageal recessThe most important mediastinal line to look for is the azygoesophageal line, which borders the azygoesophageal recess. This line is visible on most frontal CXRs. The causes of displacement of this line are summarized in the table. A hiatal hernia is the most common cause of displacement of the azygoesophageal line. Notice the air within the hernia on the lateral view. Another common cause of displacement of the azygoesophageal line is subcarinal lymphadenopathy. Notice the displacement of the upper part of the azygoesophageal line on the chest x-ray in the area below the carina. There are also nodes on the right of the trachea displacing the right paratracheal line. On the PET we can appreciate the massive lymphadenopathy far better than on the CXR. There are also lymphomas in the neck. Continue with images of CT and ultrasound. Here we see a CT-image. The final diagnosis of small cel lungcancer was made through a biopsy of a lymphnode in the neck. First study the chest x-ray. Notice the following:
Here we have a prior CXR of this patient. The AP-film shows a right paratracheal mass. Notice the massive dilatation of the esophagus on the CT. Aortopulmonary windowThe aortopulmonary window is the interface below the aorta and above the pulmonary trunk and is concave or straight laterally. Here the AP-window is convex laterally due to a mass that fills the retrosternal space on the lateral view. On the CT-images a mass in the anterior mediastinum is seen. Final diagnosis: Hodgkins lymphoma. Here another case. The PET better demonstrates the extent of the lymphnode metastases in this patient. Final diagnosis: small cell lungcarcinoma. LungsLung abnormalities mostly present as areas of increased density, which can be divided into the following patterns:
Less frequently areas of decreased density are seen as in emphysema or lungcysts. These lungpatterns will discussed in more detail in an article that will be published soon: Chest X-Ray - Lung disease. Consolidation Tap on image to enlarge Atelectasis Nodule - MassesTap on image to enlarge. Solitary pulmonary node - SPN is discussed here. Interstitial patternTap on image to enlarge. Interstitial lung diseases are discussed here. PleuraPleural fluidIt takes about 200-300 ml of fluid before it comes visible on an CXR (figure). Total opacification of the right hemithorax in a patient with pleuritis carcinomatosa on both sides. On the right there is only some air visible in the major bronchi creating an air bronchogram within the compressed lung. Pleural fluid may become encysted. Here we see fluid entrapped within the fissure. PneumothoraxThe table lists the most common causes of a pneumothorax. The other cystic lungdisease which causes pneumothorax is Langerhans cell histiocytosis (LCH) which is seen in smokers. Study the CXR. There are two important findings. The retracted visceral pleura is seen (blue arrow) which indicates that there is a pneumothorax. There is a horizontal line visible (yellow arrow). When a pneumothorax is small, this air-fluid level can be the only key to the diagnosis of a pneumothorax. Study the CXR. There are 3 important findings. Notice that the mediastinum is slightly displaced to the left. Do you have an idea about the cause of the pneumothorax? There is a hydropneumothorax. The upper lobe is still attached to the chest wall by adhesions. There is a lung cyst in the upper lobe (red arrow). Since this patient is a woman, lymphangioleiomyomatosis (LAM) is a possible diagnosis. LAM is a rare lung disease that results in a proliferation of smooth muscle throughout the lungs resulting in the obstruction of small airways leading to pulmonary cyst formation and pneumothorax. Study the CXR. What is your diagnosis? This is not a pneumothorax but a skin fold. The radiography was performed supine with a CR cassette inserted underneath the patient, which resulted in a skinfold. Notice that there are lung markings beyond the apparent pneumothorax. Here two CXRs of another patient with obvious skinfolds. Recognition of a pneumothorax depends on the volume of air in the pleural space and the position of the body. A sign to look for is the 'deep sulcus sign'. The image is of a patient in the ICU who is on mechanical ventilation. There was an acute exacerbation of the dyspnoe. Notice that the left hemidiaphragm is depressed. The image on the right is after insertion of an intercostal drain. Notice that the diaphragm has regained its normal appearance. Pleural opacitiesThe table lists the most common causes of pleural opacities. Pleural plaques Some of these opacities are clearly bordering the chest wall (red arrows). All these findings indicate that we are dealing asbestos related pleural plaques. Asbestos related pleural plaques are usually:
Unilateral pleural calcifications are usually due to:
Pleural hematoma It was believed to be a hematoma and resolved spontaneously. Chest wallRibfractures The CXR shows many rib deformities due to old fracturees. When a rib fracture heals, the callus formation may create a mass-like appearance (blue arrow). Sometimes a CT is necessary to differentiate a healing fracture from a lung mass. Notice the large lung volume and the enlarged pulmonary vessels. The second most common chest wall abnormalities that we see on a CXR are metastases in vertebral bodies and ribs. Notice the expansile mass in the posterior rib on the right. AbdomenThe most obvious finding on this CXR is free air under the diaphragm. This finding indicates a bowel perforation, unless when the patient had recent abdominal surgery and there is still some air left in the abdomen, which can stay there for several days. There is another subtle finding in the left upper lobe. Here another patient with free abdominal air. Notice the very thin regular line which is the diaphragm (arrow). At first impression one might think that this is just some plate-like atelectasis due to poor inspiration. What is a lateral chest radiograph?The lateral chest view examines the lungs, bony thoracic cavity, mediastinum, and great vessels.
What are the landmarks for the lateral chest?Lateral landmarks include the axillary fossa (armpit). The axilla is bounded superiorly by the outer border of the first rib, the middle third of the clavicle, and the superior border of the scapula. Inferiorly, its extent is defined by the lower border of the axillary fossa.
What is a lateral radiographic view quizlet?What is a lateral radiographic view? Correcta. The x-rays are directed from one side of the body to the other side.
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