Ultrasound or Radiographs (x-rays) – What’s The Difference?

Feb 21, 2013 by Dr Diana Lafer    No Comments    Posted under: Personal Opinion, Tips & Advice

Unlike radiographs, ultrasound uses sound waves to generate a picture of the internal organs. Ultrasound is completely safe and painless and does not require anesthesia or sedation in most cases.

Ultrasound may be recommended after a physical examination, blood test or x-ray indicates an underlying problem. Ultrasound is commonly used in both veterinary and human medicine for a wide variety of problems, including diseases of the liver, kidneys, bladder, stomach, intestines, pancreas, heart, and other organs. As with people, it can be used safely during pregnancy.

Ultrasound can “see” many things that can’t be seen on x-rays. For example, if there is fluid build-up in the chest or abdomen, the organs can’t be seen clearly on x-ray because fluid and tissue have the same density. However, they appear quite clearly on ultrasound, because we can see through the fluid. In addition, while x-rays are helpful to see the shapes and sizes of the internal organs, ultrasound can get a picture of the internal structure.

If an x-ray shows an enlarged heart, we can’t tell from the x-ray if the walls of the heart are thick with narrowed heart chambers (where the blood flows) or if the walls are thin and weak with big chambers or if there is fluid build-up between the heart and the sac that surrounds it. Ultrasound can readily give us this information, which is critical, as these scenarios represent different types of heart disease, with different prognoses and treatments.

Ultrasound is not effective at seeing through air or bone, so it does not replace x-rays but rather is complementary. In some cases both x-rays and ultrasound are needed in order to get a complete picture of what is going on with a patient.

Ultrasound equipment is specialized and quite expensive, so not all veterinary hospitals have an ultrasound machine. Many hospitals have specialists that come to perform the examinations. Other hospitals refer their patients to a hospital that can provide this level of care. In some cases of complex heart disease, evaluation by a veterinary cardiologist may be needed.

Due to the specialized nature of ultrasonic exam and evaluation, it is critical to have a veterinarian who is experienced in obtaining and reading ultrasound images to perform the examination, and make this information apply to each patient in a meaningful way in terms of prognosis and treatment recommendations.

What happens during an ultrasound?

The hair over the area to be evaluated will be shaved, as hair will interfere with the images. A gel (water soluble and safe) will be applied to the skin to help the sound waves generate a good picture. A transducer (similar in size and shape to a TV remote control) is placed on the patient’s skin and slowly moved around over the area to be examined. The ultrasound is computerized, so it can be used to accurately measure the tissues as needed. In addition, images can be stored electronically.

In order to perform a thorough exam, the patient needs to stay relatively still, though some wiggling is fine. Although some cats may be slightly anxious initially, most relax and remain calm once they realize that nothing painful is happening. For cats that are very anxious, your veterinarian may recommend a sedative.

What should I do to prepare for the ultrasound procedure?

Please do not feed your cat for 8-12 hours prior to the examination. Water is permitted. In the case of an abdominal ultrasound, an empty stomach allows for proper imaging of the area near the stomach. There are some diseases/situations where food should NOT be withheld; contact your veterinarian for specific instructions. If your cat is having an abdominal ultrasound, please try not to let your pet urinate for the 3 hours prior to your appointment. This will help get a better picture of the bladder.

What will the ultrasound tell us?

An ultrasound examination will provide a lot of information about your cat’s health. Together with the internist, we look at information from lab tests, x-rays, examinations and medical history to make medical recommendations.

• A specific diagnosis: often ultrasound can provide us with a diagnosis (or a reason for your cat’s illness).
• A Partial diagnosis: While ultrasound shows us the shapes and consistencies of the internal organs, it cannot see microscopic changes. This means that while an ultrasound examination can identify abnormal tissue, including growths, it cannot always determine if the tissue is cancerous or what type of cancer it is. For some patients, this information will affect how they are treated and a biopsy may be recommended. In some cases, this biopsy may be performed as an ultrasound guided needle sample under light anesthesia. In other cases, a surgical biopsy is needed.
• No Diagnosis/ Disease Exclusion: For some patients, the organ changes are not visible enough to pinpoint the problem. We are able to exclude (or rule out) certain diseases, but are left with a list of possible diseases that are causing your cat’s illness. This can be both relieving and frustrating. We will discuss options for therapies based on the available information and will recommend the best path for additional testing to obtain a diagnosis if indicated and desired.

If you have additional questions about whether ultrasound or x-rays are appropriate for your cat, please contact your veterinarian.

Dr Diana Lafer

Dr. Diana Lafer founded Cats Limited in 1995. She earned her bachelor’s degree in biology from Wesleyan University and her veterinary degree from Cornell University. Dr. Lafer has a cat (Sparky), and a dog (Lucy). She enjoys spending time with her daughters, horseback riding, skiing, hiking, participating in triathlons, and volunteering for the Lakeville Pony Club.

Cats Limited Hospital
1260 New Britain Avenue
West Hartford, CT 06110

Phone: (860) 561-9885
Email: cats@catslimited.com

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