Note 4th year Chest.docx

Normal features of a good chest x-ray and review of some chest pathologies Lecturer: Dr. Okechukwu Prisca Onyinye Material source: The chest Radiography by Barry Kelly The Normal Chest Radiograph Technical Aspects The three criteria routinely reviewed to confirm the satisfactory quality of any...

Normal features of a good chest x-ray and review of some chest pathologies Lecturer: Dr. Okechukwu Prisca Onyinye Material source: The chest Radiography by Barry Kelly The Normal Chest Radiograph Technical Aspects The three criteria routinely reviewed to confirm the satisfactory quality of any chest radiograph are: - Rotation - Inspiration - Penetration. Rotation A satisfactory chest radiograph should have no rotation. This is confirmed by ensuring that the medial borders of the clavicle are equidistant from the spinous processes of the vertebral bodies. Inspiration It is also important to ensure that the patient has made a good inspiratory effort. This is confirmed by ascertaining that there are ten ribs visible posteriorly in the mid clavicular line on the frontal chest radiograph. Penetration In an X-ray with good penetration, the vertebrae behind the heart are barely visible, and the diaphragm can be traced up until reaching the edge of the spine.  A System for Reviewing the Chest Radiograph 1.AP or PA Orientation? 2.The Heart Size The maximum transverse diameter of the heart should not exceed 50% of the maximum transverse diameter of the chest on a standard posteroanterior (PA) radiograph. This measurement is known as the *Cardiothoracic Ratio.*  3.Pulmonary Vascularity a. Pulmonary venous vessels should not be discretely visible in the outer third of the lung fields. b. Approximately 90% of the pulmonary vascular structures are appreciated at the mid and lower zones. This is an effect of gravity. 4.The Lung Fields An American Radiologist named Benjamin Felson described *The Silhouette Sign.* He posited out that only three densities are visible on any radiograph. These are bone, air and soft tissue. The reason that we can appreciate one density, for example the heart shadow, is because it abuts a different density, and consequently, we see a silhouette. If that normal silhouette disappears, it implies that the adjoining area has now transmuted into the *same density* as its neighboring structure, usually indicating lobar consolidation caused by infection. The Silhouette Sign. The diaphragm and heart borders are adjacent to lung lobes. Review Areas There are several review areas that a reviewer should consider in every chest radiograph 1\. Sub diaphragmatic region  On the erect chest radiograph there should be no free gas present under the diaphragm. On the left side, a gastric air bubble is frequently seen. On the right, interposed small or large bowel may occasionally be seen. Even very small quantities of free gas can be confidently seen under the right  Right-sided pneumoperitoneum 2\. The Lung Apices  Evaluating the lung apices can be difficult. This is particularly the case in the older patient where there is asymmetrical calcification of the costochondral junctions. This age-related calcification can mimic a neoplasm. If there is diagnostic uncertainty, or an asymmetry in the apical appearances, the simplest solution is to request a supplementary apical view. This allows visualization of the lung apices without the complication of overlapping bony structures Subtle left apical mass on chest radiograph (arrows).  Apical view reveals a distinct neoplasm at the left apex (arrows). 3\. Trachea  The trachea is often deviated by pathology within the neck or chest and ascertainment that it is midline is essential. The commonest neck mass to displace the trachea is a thyroid mass, which will displace it to the contralateral side. Within the chest, a tension pneumothorax will displace the trachea to the contralateral side, while collapse or atelectasis of a lobe will draw the trachea towards the side of the abnormality. 4\. The Hilum  The *hilar point* on either side of the heart represents the intersection of the pulmonary arteries and veins. The left hilar point normally lies higher than the right. Aside from this, the hila should always be equal in size and density. 5\. The Aorto-pulmonary Window  As the reviewer follows the left edge of the mediastinum from its superior aspect, the first convexity seen is that of the aortic knuckle. If one traces the edge of the aortic knuckle inferiorly, the next convexity is that of the pulmonary artery. Between the two there is a concavity. There should be nothing within this aorto-pulmonary bay or window. It is very important that review of this window is performed in every chest radiograph. It is well recognized that malignant lymphadenopathy associated with a neoplasm can manifest itself within this window. 6\. Bones  Bone review effectively is performed for two reasons: - a\) Trauma: to exclude fractures or dislocations, particularly at shoulder level. - b\) Neoplasia: to exclude infiltration and destruction particularly in metastatic disease and myeloma. **Common Pathologies** Cardiac Failure The following features are seen in cardiac failure 1. Increased cardiothoracic ratio 2. Increased (venous) pulmonary vascularity 3. KerleyB lines 4. Pleural Effusions 5. Bat or Angel Wings Cardiac Failure. Lobar Consolidation The confident and accurate diagnosis of lobar consolidation rests on an understanding of the silhouette principle as described by Felson. In the annotated chest radiograph, all one must do is confirm which silhouette is missing. The appropriate pulmonary lobe can then be identified. These are:  Lobar consolidation involving the right middle lobe, right lower lobe and left lower lobe. Left lower lobe: Left hemidiaphragm Right lower lobe: Right hemidiaphragm Right heart border: Right middle lobe Left heart border: Lingula. Consolidation in the upper lobes follows the same principle but is slightly different. On the right-hand side, the lung is demarcated by the transverse or minor fissure. Consolidation above, and terminating at, the minor fissure indicates right upper lobe consolidation. Consolidation below, and terminating at, the transverse fissure, delineates the right middle lobe. Consolidation of the left upper lobe tends to produce a fuzzy 'veiling' effect with consequent reduced conspicuity of the aortic knuckle\'s silhouette. Pneumothorax Pneumothorax is divided into the *simple* and *tension* pneumothorax. The tension pneumothorax is diagnosed radiologically when the mediastinum is displaced to the contralateral side and there is inferior displacement of the ipsilateral hemidiaphragm. Accompanying clinical distress is of course also present. Right-sided tension pneumothorax In an otherwise fit and conscious patient, a pneumothorax is seen as the separation of lung edge from the chest wall. This is maximal on expiration because of the relatively increased interpleural pressure, and therefore if there is a clinical suspicion of pneumothorax it is worth requesting an expiratory view. Pleural Effusions The typical appearances of pleural effusion on an erect radiograph are those of an area of increased density with a meniscus rising up the lateral chest wall. This meniscus reflects the negative intrapleural pressure of fluid within the pleural space. A horizontal fluid level within the chest, however, suggests a hydropneumothorax with air in the pleural space. Remember also that if the mediastinum is not displaced in the presence of a pleural effusion, this indicates underlying collapse of the ipsilateral lung segment or lobe.  Pleural effusion, right side. Other images Primary TB  Bronchiectasis