X-rays (radiographs) are a common non-invasive diagnostic procedure in veterinary medicine to see inside the body which uses a type of radiation called electromagnetic waves.
A controlled beam of radiation passes through the body and falls on a piece of film or plate (for digital x-rays) where it casts a type of shadow. Dense parts of the body, such as bone absorb more radiation and show as white on the film, soft tissues, such as muscles and organs appear in shades of grey, and the air-filled lungs appear almost black.
X-rays were discovered in 1895 by Wilhelm Röntgen, and they are the oldest and most common type of medical imaging.
Film and digital x-rays
Traditional x-rays involve a film; however, modern x-rays are digital, and the image is captured onto a plate, which goes directly to a computer. Benefits are that the process is faster, and veterinarians can email digital images to veterinary specialists or clients.
What can x-rays diagnose?
X-rays can evaluate any area of the body including the chest, thorax, limbs, skull and mouth. They can help to identify the size and shape of internal organs and look for changes, abnormalities and foreign objects.
- Gastrointestinal tract: Ingested foreign object, gastrointestinal obstruction, esophagitis, intussusception, plication, constipation, megacolon.
- Head and skull: Broken bones (skull, jaw, teeth), tumours.
- Thorax (chest): Pneumonia, pneumothorax, pulmonary edema, lung cancer (primary or secondary), lung abscess, heart disease, asthma, pleural effusion, pulmonary thromboembolism
- Abdomen (belly): Liver shunt, kidneys (stones, infection, inflammation, cysts, tumours, anatomy), pancreatitis, unexplained vomiting or diarrhea, tumours, saddle thrombosis.
- Bone and joint disorders: Broken bones, bone infection, bone cancer, arthritis, ligament damage, patellar luxation, hip dysplasia, spondylosis.
- Reproductive organs: Check size and number of kittens in late pregnancy (43 days onwards), pyometra, cancer.
- Urinary tract: Urethral blockages and crystals, kidney stones, bladder stones.
Inform the veterinarian if there is any chance the cat is pregnant as an x-ray is not safe to use in the early stages of pregnancy.
If a general anesthetic is necessary, the veterinarian will instruct you to fast the cat overnight to prevent aspiration pneumonia.
The cat may have sedation or short-acting general anesthesia for the procedure to ensure no movement during the x-ray. In some cases, it may be possible for veterinary staff to hold the cat still. They must wear appropriate lead aprons, gloves and thyroid guards during the x-ray procedure.
The veterinary staff measure area; this avoids unnecessary exposure to parts of the body. Depending on the area the cat may be positioned on the side (right or left lateral), back (dorsal) or belly (ventral). The x-ray itself only takes seconds, but in most cases, the veterinarian will take two views (positions) to reach an accurate diagnosis.
After the x-ray
Veterinary staff will monitor the cat until the effects of sedation of general anesthetic have worn off.
Processing and evaluating the x-rays take time, and in some cases, the veterinarian will ask a radiologist (a veterinarian with advanced training in the interpretation of diagnostic images) to check the images to confirm the diagnosis.
In a lot of cases, an x-ray can provide a diagnosis and are the first line in the diagnostic workup. Sometimes it will be necessary to run additional diagnostics if x-rays are inconclusive.
Barium studies: A type of x-ray where the cat ingests barium sulfate followed by an x-ray. The barium coats the inside walls of the gastrointestinal which appear white on x-rays. This enables the veterinarian to see the structures of the gastrointestinal tract and monitor transit time, which is the speed at which food passes through the digestive system.
Ultrasound: Ultrasounds use high-frequency sound waves to create images of the inside of the body and capture images of soft tissues that don’t show up well on x-rays.
Computed tomography (CT) scan: Also known as a CAT scan, a CT scan is an advanced non-invasive medical imaging technique. The procedure uses a combination of x-ray imaging and a digital computer to produce detailed 3-dimensional images of the bones and tissues inside the body.
Magnetic resonance imaging (MRI) scan: An imaging test that can give very images of the inside of the body. Instead of using x-rays, the MRI uses strong magnets, low-energy radio waves and a computer to produce images.
Frequently asked questions
Are x-rays painful?
No, x-rays are painless.
Are x-rays dangerous?
Radiation is everywhere, in the air we breathe as well as water, rocks, soil and plants at low levels. The dose is measured in Sieverts (Sv); humans absorb around 2 milliSieverts (mSv) from the environment every year.
Because x-rays emit radiation, they are classified as carcinogenic (cancer-causing). In human terms, the amount of radiation from one adult chest x-ray (0.1 mSv) is about the same as 10 days of natural background radiation that we are all exposed to as part of our daily living.
The benefits of an x-ray (for accurate diagnosis) outweigh the risks, and the exposure is minimal. Veterinarians won’t recommend an x-ray unless they have a valid reason to do so.
How much do x-rays cost?
The cost of x-rays will depend on the location, the number of x-rays, and if sedation or anesthesia is necessary. Dental or limb x-rays can start from $100 to $150; more complex x-rays can run into several hundred dollars.