Reading a Chest X-ray
Only the radiologist can official read or interpret a chest x-ray, and when they do this they take into consideration the patient's history and current complaints. The radiograph is another piece of important data that can support or rule out a diagnosis. This information then informs the patient's physician and guides the care plan for that patient.
The key to reviewing a film is to consistently follow the same systematic approach.
This may be from the outside to inside, or inside to outside, or some may use an alphabet approach.
The first step is to position the film appropriately.
The cardiac shadow should angle downward to your right. (Positioning of film will not be a problem with a digital image!).
Second assess the quality of the film:
Position of patient - is the chest centered on the image, is the image complete or cut off.
Rotation - Spine should be visible between the ends of the clavicles
Penetration - spinous processes should be barely distinguishable, if they are very distinct the film is overpenetrated (overexposed) which will make the lung fields look darker as well and could give a false normal image.
Key things to look for on the x-ray
Tissues: subcutaneous air in the tissues of the neck, on the sides of the chest and into the muscle wall of the chest will show up a black stripes in areas that should normally be consistently gray.
Ribs: looking for deformities, fractures, and uniform spacing between ribs.
Spine: curvatures can be noted (scoliosis, kyphoscoliosis)
Pleural space: particularly the angle where the diaphragm meets the chest wall, for meniscus-type shadow that would indicate collection of fluid. Since the diaphragm slopes downward to the back, by the time pleural fluid is evident as costo-phrenic angle blunting, there is a significant accumulation of fluid (one or more liters). Also look for area that is very black in apical regions on an upright film as that may be an indication of pneumothorax.
Assess depth of inspiration - hopefully 10 ribs are visible.
Expiratory films are also good for accentuating the presence of a pneumothorax as the lung density increases and the contrast with the air in the pleural space is more evident.
Bronchi - a tree branching type dark shadow extending into the lungs is abnormal and is indicative of consolidation.
Size of the heart can be assessed - normal is less than 1/2 the diameter of the chest.
Aortic arch or knob should be visible - calcium deposits in the arterial wall will show a white circle on x ray
Trachea: Identify position and follow down to where it branches into the Right and Left main stem bronchi, identify the carina
On the lateral chest exam there may be an increase in air between the sternum and the heart in patients with air-trapping an barrel-chest. This is called an increased retrosternal airspace.
Identify all foreign objects
Assess indwelling lines such as artificial airways, chest tubes, central lines, nasogastric/feeding tubes, sternal wires indicate history of open heart surgery, artificial heart valves, implanted pace-makers, and shrapnel from injuries and bullets.
External lines lying on the chest will also be seen and you will need to differentiate from indwelling lines. Ventilator tubing may be left on the chest and it will cast a shadow - it is best to reposition this tubing so as not to obscure important parts of the image. EKG monitoring lead wires, oxygen delivery device tubing, gown snaps, bra hooks and wires, and safety pins are frequently seen on images.
HINT: Being able to gather information from the chest x-ray is a skill. Read the radiologist interpretation of the image while viewing the film and try to see what the radiologist describes.