Medical imaging, understanding it all: X-rays, ultrasound and more for your pet

X-rays, ultrasound, scanners, MRI… We hear these words more and more in the field of veterinary medicine. But what are they all really? And why would we consider these for your pets? Well, they are medical imaging systems that help to establish the diagnosis and treatment of your animal, just like in human medicine. Many veterinary practices now have X-ray and ultrasound machines because they are easy and quick to use, and they provide valuable information.


X-rays, traditional or digital, provide a 2D photo-like image. That is useful for examining much more than just bones. While it is used to highlight broken bones or liquid in joints, it also allows assessment of the internal structures, such as the size and shape of organs. X-rays are used to assess pathologies in the lungs like a mass, or to see the shape of the heart, the oesophagus, the trachea and much more. In the abdomen, it is useful to detect calculus in the bladder, in the kidneys, and even in the ureter. Your pet may have eaten something and now they are feeling under the weather? An X-ray will allow an assessment of the digestive tract and look for a foreign body.

Sometimes an X-ray is enough to make a diagnosis, but we have to keep in mind that it is a 2-dimensional image and organs are 3D structures. To prevent overlooking a condition, it is always better to take 2 X-rays, one perpendicular to the other, which allows us to visualize the third dimension. When we are looking for a thoracic tumour, for example, it is even better to take a third X-ray.

How do we get an image from taking an X-ray? The machine generates rays that cross the targeted area to reach a plate (which previously held a film like in photography) and transforms the data into images. Not all the rays reach the plate. Some structures with higher density don’t let the rays go through and appear white on the image (e.g., metal, bones, etc.), while low-density structures let the rays through easily (e.g., air, liquid, etc.) and will show as black on the image.


Ultrasounds use waves to create a dynamic and moving image. Via a probe touching the animal’s skin, we can see various internal organs. The ultrasound gel provides close contact between the scanning surface of the probe and the skin to provide a proper image. Therefore, it is often necessary to shave the area to be scanned. Ultrasounds provide us with structural information such as the size, shape, and density (e.g., solid, liquid, cystic, etc.), but they also give vascular information about the organ and the mass targeted. In an emergency, use of ultrasound may allow prompt assessment of your pet’s condition by showing abnormal liquid or gas in the abdomen (e.g., internal bleeding), or around the lungs or heart. As ultrasounds travel in tissues and organs, it is not possible to assess high density tissue like bones because they don’t generate images. Ultrasound can also be useful as a guide during procedures like cytology, biopsy, sterile sampling of urine, etc.

Depending on the situation, ultrasound is used alone or with an X-ray. Your veterinarian can then advise you on what’s best for your animal. Both ultrasound and X-ray are non-invasive and don’t usually require anesthesia. It is important to understand that the quality of the image and test result depends on the response and capacity to have the animal stand still. If the animal is stressed, or in pain, sedation and pain management medicine are highly recommended to ensure image clarity and prevent poor diagnosis imaging.

Veterinarians specialized in medical imaging

Finally, there are veterinarians who are specialized in medical imaging. They are radiologists like in human medicine. They read images from X-rays, ultrasounds, and MRI, and they do all kinds of procedures using ultrasounds. In cardiology, ultrasounds are required to assess various heart valves and cavities and are typically done by a veterinary cardiologist. Specialized veterinarians usually work from referral centres. In some cases, your veterinarian can refer you to such a centre for specific tests in order for your pet to benefit from specialized expertise.

Have more questions?

Please do not hesitate to contact the Passionimo veterinary clinic near you.