Chest-x-rays in dogs are often recommended by vets for diagnostic purposes. Just as in people, chest x-rays in dogs are safe and painless and use a small amount of radiation for the purpose of taking a picture of the dog's chest. In many cases, chest x-rays can be done without sedation, but dogs who are excessively wiggly, fractious, or aggressive, may sometimes require it. During the examination, the dog is held still while an X-ray machine sends a beam of radiation through the dog's chest. The image obtained is then recorded on special film.
Chest X-rays in Dogs
Chest x-rays in dogs reveal several organs and structures within the dog's chest such as the heart, lungs, the aorta and pulmonary arteries and veins, diaphragm, trachea (windpipe), lymph nodes, the upper spine and ribs.
Chest x-rays are often requested when dogs are presented to the vet with respiratory symptoms such as wheezing, coughing, excessive panting and shortness of breath. They may also be requested in dogs with suspected heart problems or dogs suspected of having some sort of injury such as a punctured lung or a fractured rib.
When the chest x-ray is done, the image will appear in black and white. Dense body parts of the dog that are particularly dense and block the passage of the x-ray machine's beam tend to appear as white. The dog's bones and heart will therefore appear as white on the film.
On the other hand, air or hollow body parts such as the lungs tend to appear as black areas considering that the they allow the x-ray machine's beam to pass through them. Fluid, considering it's medium density, tends to show up on x-rays as grayish areas.
By visualizing these light and dark areas, veterinarians are able to detect abnormalities. Learning what's normal or abnormal on chest x-rays in dogs is not an easy task and takes years of practice and experience. Sometimes, even vets may have a hard time interpreting them and may have a specialist take a look.
Veterinarians who have made of interpreting x-rays and other imaging techniques their areas of specialty are ACVR Board-Certified Radiologists who have received advanced training in diagnostic imaging and have passed the American College of Veterinary Radiology Board Certification Examination.
Abnormal Findings on Dog Chest X-rays
Any changes and abnormalities in the dog's bones may show up in chest x-rays. Because the trachea (windpipe) can also be visualized on x-rays, the vet can find abnormalities such as a collapsed trachea. Rib or spine fractures may also show up quite easily.
X-rays also show the shape, size and outline of the heart. Changes in the heart's shape and size can indicate heart failure, fluid around the heart or heart valve problems. An enlarged heart can be indicative of cardiac disease.
Lung abnormalities may be revealed as well. Because healthy lungs are filled with air, they should have an overall dark appearance. The presence of any gray or, white areas can be suggestive of presence of fluids in the lungs or around them (as it happens with viral, fungal or bacterial infections due to build-up of pus) or presence of blood (as it happens with internal bleeding or heart disease) In heart disease, because blood is no longer pushed through the circulatory system how it's supposed to, it ends up leaking out of the blood vessels and into the lungs.
Other abnormalities that can be revealed on chest x-rays include presence of scar tissue and tumors. Chest x-rays won't typically show whether a dog has asthma.
Did you know? Microchips may show on a dog's x-ray considering that microchips are injected between the shoulder blades. Indeed, this is a good way to look for one! On a chest x-ray the microchip may look like it's within the chest, when in reality it's just under the skin near the shoulder blade, explains veterinarian Dr. Altman.
Cancer in Dog Chest X-rays
One main reason why vets may suggest chest x-rays is to rule out the presence of cancer. Many types of cancers quickly spread to a dog's lungs.
On x-rays, cancer will show up as a visible mass or nodule under the form of a white spot on the lungs. This white spot will stick out considering that the lung themselves will appear black. There may be one spot or several spots. For sake of an example, lung cancer on x-rays can show as several small or large round shaped cotton balls against a dark black background.
Cancer of the lungs can be a primary lung cancer or metastatic lung cancer (cancer originating from other location that has spread). Unfortunately, chest-x-rays are not good in diagnosing lung cancers at an early stage. By the time lung cancers in dogs are discovered on a chest x-ray, the cancer is therefore quite advanced.
In some cases, for dogs who live in areas predisposed (such as the desert southwest), a systemic yeast infection called coccidiomycosis can be misdiagnosed as advanced lung cancer as the lesions appear quite similar (large "white" areas all over the lung fields). Other fungal infections that may cause presence of spots on a dog's lung include histoplasmosis or blastomycosis.