You’ve probably come across your vets discussing X-rays and scans, both of which are commonly offered in first-opinion veterinary practices. Whilst the imaging modalities are complementary to each other and may be suggested to be used together, you may be wondering what the difference is between the two. Your veterinary professional will advise which imaging technique they feel will provide the most relevant information to your pet’s health, and this will vary on a case-by-case basis. However, in this article we’ll take a look at the two options and look at the differences, strengths and weaknesses of each.

Table of contents

Please remember repeat imaging may be necessary, as things can change very quickly, and imaging will only show exactly what is present at that moment in time. Neither of these imaging techniques are invasive and both can usually be carried out within an hour.

What is an X-ray?

An X-ray, or radiograph, is an image produced by X-ray waves being transmitted through your pet’s body. Different amounts of radiation are absorbed and reflected by different tissues in different amounts, creating different shades of grey allowing identification of tissues and abnormalities.

Pros of X-ray

  • Radiographs are very good at showing the outlines of organs, allowing interpretation of size.
  • Radiographs give good bone definition, making fractures and bone pathology much easier to see.
  • A large image is produced, allowing you to view an extensive area of the body with one image.
  • Images can be saved, allowing your veterinary team to keep them for interpretation at a later date. This allows you to seek referral advice without having to transport the patient.
  • Obtaining the radiograph is quick. 

Cons of X-ray

  • The radiation used to produce an X-ray is potentially dangerous and exposure needs to be controlled and performed in the safest possible way. The patient and staff involved must be exposed to the lowest amount of radiation that is reasonably possible.
  • Your pet will need to remain very still, so they may require chemical restraint (the use of drugs). Your veterinary team will try to use sandbags and ties, but medical sedation is commonly required.
  • Radiographs may have artefacts (extra shadows or spots in the image) which could be misinterpreted.
  • A radiograph only shows a fixed image, at one snapshot in time.
  • X-rays can’t distinguish between fluid and soft tissue – so organs like the heart or liver often appear as solid masses, without any way to study their internal components.

What is an ultrasound?

An ultrasound machine uses echo reflection to penetrate and outline organs to create an image directly onto a screen – just like a bat’s, a whale’s, or a submarine’s sonar. Your veterinary professional uses a probe to image your pet’s body. Your pet will need to be clipped and lots of gel will be applied to the skin of your pet to allow the sound waves to penetrate the skin better. The veterinary professional moves the probe around your pet’s body, altering the focus point and depth of the penetration to allow observation of different organs to be viewed. This is just like pregnancy ultrasounds in us humans.

Pros of ultrasound

  • Ultrasound waves are very safe for the patient. 
  • Ultrasound imaging allows vets to look at one organ in more detail, giving more information about the definitive location of masses and their size, for example. 
  • The image is dynamic (a moving live image), allowing the vet to monitor the movement of blood and digesta. This can be useful when analysing cardiac health and gastrointestinal health amongst other things.
  • The ultrasound can tell us the difference between soft tissue and fluid, giving us excellent imaging inside of the heart, the liver and other solid organs.
  • Ultrasonography is commonly performed on a fully conscious patient.

Cons of ultrasound

  • The image interpretation is more dependent on the user, compared to radiography.  
  • There is a much smaller field of view, so the vet can normally only see one organ at once.
  • Ultrasonography can take much longer to perform than radiography.
  • Ultrasound cannot penetrate air or bone, meaning it is very limited in imaging bone or lung issues.
  • If your pet is not tolerating ultrasonography, they may need to be sedated using drugs.
  • Your pet will return home with a clipped patch of fur on their body where the probe has been placed.

The pricing of each imaging modality will vary from practice to practice and will differ on a case-by-case basis, depending on how many views are needed and which drugs are required. You should always ask for an estimate before giving consent.

Find a local vet

To conclude, there are many different pros and cons to each imaging modality. You should follow your veterinary professionals’ advice regarding which option would benefit your pet the most.

Further reading: