|ECR 2018 / C-3098|
|Chestlist: how to systematically read, interpret and report chest X-rays|
Findings and procedure details
The following checklist aims to guide the reading of chest X-rays in a systematized order, so the interpretation is done in an organized and efficient way, and can be used to succinctly guide chest X-rays reports. Each medical doctor should create its own reading sequence, easier to memorize and less prone to failure. Amusingly, we call this checklist to read chest X-rays - Chestlist Fig. 3.
1. Patient identification
Patient identification should always be the first item checked when reading any imaging study. Interpreting an exam of another patient may lead to a loss of time and energy until the perception of the error, or worst, to a complete exchange of images that can have serious consequences. Patient identification verification should include at least the full name, birthdate and institutional identification number.
2. Study date
Non-verification of the study date can lead to a huge loss of time and energy spent reading and interpreting a non-wanted exam. Like the patient identification verification, exchange of exams with a previous study can have serious consequences for the patients. Nevertheless, the previous exams are extremely important and should always be checked out, being indispensable for follow-up effects and to clarify doubts in the current study.
3. Image subtitles
There is some information related to the moment of the image acquisition that is essential for correct study interpretation. The radiographer should insert these aspects on the image, being accessible to all. It can be just letters (identifying the radiographic incidence or the right/left side of the patient) or a few words (describing patient positioning and/or unusual but important events). Side marker placement is imperative; patients can have congenital conditions that mimic a mirrored image Fig. 4. This kind of information should be taken into account when interpreting the imaging findings, and most of the time must be explicited on the report.
Use concise and medical vocabulary if possible:
Patient positioning – orthostatism, seated, decubitus (dorsal, ventral or lateral).
Incidence (discussed next) – AP, PA, lateral view and apical view, in inspiration or expiration.
Specifications – most commonly immobilized, not collaborating or cannot be undress Fig. 5.
There are a few incidences used in chest x-ray studies. The most frequent and more indicated one is the PA view in inspiration Fig. 6 . These conditions of acquisition allow greater exposure of the pulmonary parenchyma and less magnification of the mediastinal structures. The AP is the alternative to the PA view, with lesser quality, but sometimes it is the only imaging available Fig. 7. Most commonly used in the elderly, bedridden, immobilized patients and children. Its major disadvantage is the magnification of the mediastinal structures, and its major advantage is the possibility to perform outside the radiology department by a mobile X-ray unit. The abbreviations PA and AP are generally accepted and used in image captions and chest X-rays reports. Lateral view should always be acquired when possible in association with a frontal view (PA/AP) Fig. 6. It allows a more specific localization of imaging findings, clarification of some doubts raised in the frontal images and to evaluate blind areas in the frontal views, like retrosternal and retrocardiac spaces as the parenchyma superimposed by the diaphragm Fig. 8 . Apical or lordotic view allows deprojection of the clavicles and visualization of the pulmonary parenchyma of the apices, hidden in the frontal incidences.
All chest radiographs, with rare exceptions, should be acquired in maximum inspiration. This allows a greater expansion of the thoracic cavity, with an increase of the intercostal spaces and lowering and horizontalization of the diaphragm, consequently with greater exposure of the pulmonary parenchyma, consequently with greater diagnostic acuity. Chest X-rays in forced expiration have some indications, in particular, search for signs of pneumothorax and air trapping - due to obstructive airway diseases or inhaled foreign bodies.
5. Technical quality
The lack of technical quality may greatly affect the diagnostic acuity of a chest X-ray. This should be always evaluated, and if necessary repeat the examination. If it’s not possible, the insufficient conditions must be safeguarded in the exam report. Here are some essential technical points to check:
● Anatomical coverage – chest X-ray, regardless of the incidence, should comprise all thorax cavity, from the pulmonary apices to the deepest costophrenic angles visible Fig. 9.
● Superimposing structures – scapulae and chin should not overlap lung fields. If this happen, they create more blind areas and decrease diagnostic acuity Fig. 10.
● Is the patient adequately centered or has some degree of rotation? - In frontal chest X-rays, patient should be adequately centered relatively to the receptor and perpendicularly to the X-ray beam. Rotation can simulate common pathology processes, like changes in the lung density due to asymmetry of overlying soft tissue may be incorrectly interpreted as lung disease, or if the patient is rotated to the left, the heart may appear enlarged and if rotated to the right its size may be underestimated.
To evaluate patient degree of rotation we have to look into cervical/thoracic spinous processes, generally centered to the vertebral bodies, forming a vertical line equidistant from the inner edge of both clavicles when there is no rotation. If the patient is rotated, the spinous processes will approximate closer to the inner edge of one of the clavicles Fig. 11.
● Adequate inspiration – With a full inspiration, lungs are filled with air and expand together with the rib cage, increasing the intercostal spaces and lowering the diaphragm, obtaining better exposure of the pulmonary parenchyma without interposition of other structures and better contrast between the pulmonary tissue. This way, except for rare exceptions (discussed above), every chest x-ray should be acquired in full inspiration. Appropriate chest X-ray inspiration is evaluated by counting the ribs that overlap the lung fields, it should be possible to count to the 6th anterior rib arch or to the 10th posterior rib arch (the anterior rib arches follow a more oblique orientation and the posterior one are predominantly horizontal) Fig. 12.
● X-ray penetration - An adequate degree of penetration is crucial for diagnostic accuracy, and is present if through the cardiac silhouette we can see the contour of the vertebral bodies. If there is too much radiation, consequently X-ray penetration, the overall image will appear darker, with some erasure of the pulmonary parenchyma, decreasing diagnostic acuity. When penetration is insufficient, the radiography will be whiter than usual, it will be not possible to guess the vertebral bodies through the cardiac silhouette, with less definition of the structures including the pulmonary parenchyma, also decreasing diagnostic acuity Fig. 13.
6. Pulmonary fields
The evaluation of lung fields require a systematic and careful read. Each lung field must be studied individually, followed by a combined evaluation of both fields Fig. 14. This process ensures evaluation of all the parenchyma covered by the study and a good comparison of the lung fields transparency.
On a chest X-ray, lung abnormalities will either present as areas of increased or decreased density.
Lung abnormalities with an increased density (whiter) are also called opacities, hypotransparent or hyperdense abnormalities. A practical approach is to divide these into four patterns:
● Consolidation - pathologic process that fills the alveoli with fluid, pus, blood, cells or other substances resulting in lobar, diffuse or multifocal ill-defined opacities.
● Interstitial - involvement of the supporting tissue of the lung parenchyma resulting in fine or coarse reticular opacities or small nodules.
● Nodules or masses - any space occupying lesion either solitary or multiple. Size does matters for nomenclature: micronodule < 0,7 cm; nodule 0,7-3 cm and mass > 3 cm.
● Atelectasis - decrease amount of air in the alveoli of part or total lung, resulting in volume loss and increased density.
Lung abnormalities with a decreased density (darker) are called lucencies, hypertransparent or hypodense lesions, like in pneumothorax and air trapping abnormalities (obstructive airway diseases or inhaled foreign bodies). They can occur as focal findings within the lung:
● Cavity - lucency with a thick wall or mass.
● Cyst - lucency with a thin wall.
● Emphysema - lucency without a visible wall.
Describing these changes, we need to specify the location: whether they are focal/diffuse, bilateral or on the right/left lung, and if possible the lobe (using the lateral incidence and the silhouette sign).
7. Pulmonary fissures
As we know the pulmonary pleura consists of two leaflets that line the thoracic cavity in its thoracic, mediastinal and diaphragmatic facet. This one has reflections that interpose between the pulmonary lobes Fig. 15:
● On the right - the oblique/greater fissure has an anterior-inferior orientation and separates the upper and middle lobe from the lower lobe. The horizontal/small fissure separates the upper lobe from the middle lobe, and so the middle lobe lies between the two fissures.
● On the left - the oblique/greater fissure has an anterior-inferior orientation (more vertical than the right oblique fissure) and separates the upper from the lower lobe.
8. Pulmonary hilum
Each pulmonary hilum is composed of the main bronchus, trunk of the pulmonary artery, pulmonary veins and their major branches. They are discretely radiopaque mainly due to the density of the vessels. Both should be similar, morphological and dimensional, with the right one usually assuming a topography inferior to the left (difference < 2,5 cm) Fig. 16.
As we know, the mediastinum contains all the thoracic viscera except the lungs. On chest X-ray, it should be evaluated in frontal and lateral view, and checked its morphology/silhouette, dimensions (including cardiac-thoracic index <0.5 Fig. 17) and density. Make sure to evaluate properly its contour, as many changes are only understood by contour deviation or by making a silhouette signal with it Fig. 18, Fig. 19. The evaluation should be done, similarly to the lung fields, in a systematic and efficient way.
Its division into compartments frequently helps to describe the location of the abnormality founded and to narrow the list of differential diagnoses:
●Superior mediastinum: above the upper level of the pericardium and plane of Ludwig (horizontal line that runs from the manubriosternal joint to the inferior endplate of T4).
● Inferior mediastinum: below the plane of Ludwig.
● Anterior mediastinum: anterior to the pericardium.
● Middle mediastinum: within the pericardium.
● Posterior mediastinum: posterior to the pericardium.
10. Diaphragm and cardio and costophrenic angles
The diaphragm is a continuous organ, however due to its shape and heart impression on its central portion, it is interpreted as consisting of two domes. On the chest X-ray, normally we can delineate a smooth contour from the rib cage to the heart. The right diaphragmatic dome usually takes a superior position in comparison to the left (<3 cm) Fig. 20.
Both diaphragmatic domes form with the thoracic cage the costophrenic angles and with the heart the cardiophrenic angles. These spaces are normally occupied by lung, so they are normally hypertransparent as a continuation of the pulmonary parenchyma. If erased, that is, radiopaque, something replaced that lung space, more often by pleural effusions. The posterior costophrenic angles, visible in lateral incidences, are the deepest and the first ones to be filled in case of pleural effusion Fig. 21.
11. Trachea and bronchi
These are structures filled with air, so in chest X-ray they will appear hypertransparent. Generally, in normal X-rays we can follow down the trachea, which assumes a central position, usually discreetly lateralized to the right at the level of the aortic arch. After that, bifurcates at the carina, and we can usually see the main bronchi arising Fig. 22.
As we said earlier, chest X-ray regardless of the incidence should comprise all thorax cavity, from the pulmonary apices/larynx to the costophrenic angles. In this way, a quality study includes cervical and dorsal vertebrae, rib cage and sternum, clavicles, scapulae, and sometimes also extensive lumbar vertebrae and proximal segments of the humerus.
Bone X-ray evaluation comprises: bone morphology, contour, density and articulation. On chest evaluation, we should search focal lesions (lytic/blastic, single/multiple), diffuse density abnormalities (osteopenia), and fractures lines and loss of normal alignment.
13. Soft tissue and foreign bodies
Check the thoracic and abdominal wall, the proximal segment of both arms and neck covered in the examination. Soft tissue is denser than the air but much less dense than the bone, so at X-ray should appear as a smooth grey, whiter than the air and darker than the bone. Look for asymmetries, increased dimensions, density abnormalities Fig. 23 (increase/decrease – for example, in cellulitis and subcutaneous emphysema, respectively), and for foreign bodies (frequently clothes and medical devices).
The abdomen covered should not be neglected on chest X-ray studies. One of the major reasons why, is the higher sensitivity for pneumoperitoneum than the abdominal X-ray studies Fig. 24. This finding usually indicates bowel perforation, unless when the patient had recent abdominal surgery and there is still some gas left in the abdomen, which can stay there for several days. Look also for gas distribution in the digestive tract, searching for the gastric bubble and for bowel loops distension.
Thematically related posters
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