Everything seems to be getting more expensive lately and veterinary care is unfortunately no exception. We have spoken before about why vet bills can be so high and why this is necessary to allow us to be able to save animals every day, but we thought today it would be good to discuss some specific costs of veterinary care. The use of diagnostic imaging, such as X-rays, is incredibly common in veterinary practice. Unfortunately they can also be expensive. Why do vets always want to spend money on diagnostic imaging? Why is it important? What is it used for?

Diagnostic Imaging

Let’s first discuss the different kinds of diagnostic imaging you may be offered by a vet.


Starting with the most well-known – X-rays were first discovered in the late 1800s by German scientist Wilhelm Röntgen, while radiography (the use of X-rays) was developed for medical use by others, including famously by Polish scientist Marie Curie. X-rays allowed us to view the bones and soft tissues inside a person for the first time. In brief, X-ray machines work by producing radiation that is beamed into the body. 

Different tissues have different densities which means different amounts of radiation is absorbed by different parts of the body. Dense objects absorb a lot while less dense objects absorb less. Underneath the body is a reader that detects the amount of radiation passing through the body. Modern X-ray machines use the different amounts of detected radiation to produce an image on a computer screen – dense objects show up as white (bones and metal) while non-dense objects show up as black (air), with organs and fluid falling somewhere in-between. 

X-rays are quick and easy to take, easy to interpret, and provide a lot of detail on the skeleton and some soft tissue. However, animals usually need to be sedated or under anaesthetic to take an X-ray properly, they are not useful when looking at fine organ detail or moving objects, some objects do not show up well on X-rays, and the radiation produced can be harmful to patients and people involved. 


Ultrasonography is a relatively new addition to the veterinary world but already is one of the most useful. Ultrasound machines beam harmless ultrasound waves into the body. Similar to X-rays it works via density, with the waves slowing down as they pass through objects of different densities. Some of these waves are reflected back at different speeds based on the density changes, which are read by the machine to produce an image.

The advantage of ultrasound is that it is very quick, harmless to the patient, can be performed on an awake animal, provides excellent detail inside organs, and can view the body in real time. The downsides are that it is quite technically difficult to perform and interpret, and can’t easily view objects surrounded by bone or air (such as the skull, spine or much of the chest).

CT and MRI:

As high-tech diagnostic imaging techniques, CT and MRI aren’t currently very common in most veterinary practices. You will often you have to visit or be referred to a specialist veterinary hospitals to get them taken.

CT is basically a 3D X-ray. SO instead of X-rays being shot in one direction, they are shot 360° around a patient, allowing computers to create a 3D model of an animal’s skeleton and tissues. MRI does something similar, but is better used to look at soft tissue and fluid – it works with a very complicated method of manipulating tiny particles using strong magnets, which we will not dwell on here. Both techniques give almost perfect 3D detail on the inner workings of an animal. However, both are currently very expensive, require a general anaesthetic and take time to perform, so aren’t suitable for emergencies like ultrasound and X-rays are.


Finally, there is endoscopy – endoscopy is the simplest diagnostic imaging technique of all. It is basically a long flexible tube with a camera and light on the end. It can be used to look inside an animal’s mouth, stomach and GI tract. Some endoscopes even have little jaws to take samples. Endoscopy is perfect for looking at the internal detail of the GI tract but also requires a general anaesthetic to perform properly. It is more common than MRI and CT, but probably less so than ultrasound and X-rays. 

Other imaging techniques exist and we will likely develop more as medical science advances. These five are the ones you will most likely encounter as an owner.

How do Vets use Diagnostic Imaging?

So all of that is very interesting, but how does that relate to your sick pet? Imaging is used for a variety of reasons, some of which we alluded to above. The common uses are for diagnosing disease or directing the next step in diagnosis, directing treatment, monitoring response to treatment and monitoring disease progression. Instead of providing a big long list of occasions you might be offered one, we thought it was a nice idea to present some real-life scenarios, so you can better understand why vets use these techniques. 

Sick Pet Scenarios

Here are just a few of the scenarios we commonly see and why some form of x-ray or diagnostic imaging is needed. This is by no means exhaustive, but are more common than you might think;

Vomiting Puppy

This one will probably bring back memories to anyone who has ever owned a puppy. Your brand new puppy won’t stop being sick so of course, you take him to the vets. The vet says he is quite unwell at the moment and is concerned that your puppy has eaten something that is stuck. They recommend an X-ray.

X-raying animals with suspected foreign bodies can help us locate and identify the object. It is also important to rule out blockages, as certain treatments can be dangerous if there is a blockage. In the past, vets would often perform surgery just to look for stuck objects, which costs more and can be risky. Luckily for this puppy, the X-ray identifies three stones stuck in his stomach! Some softer objects, such as fabric, do not show up on X-ray. In these cases, the X-ray may show gas building up after the object, which still gives us a clue that something is stuck. X-rays have successfully diagnosed the disease.

Endoscopy may sometimes come in handy if there are stuck objects – an endoscope might be used to grab the objects and pull them out of the stomach! Endoscopy also has the benefit that we can look at your puppy’s stomach and see if there is any internal damage. Endoscopy has been used to treat and manage the disease. However, in this case surgery is performed to remove the stones instead and within a few days your puppy is home again and definitely being kept away from the rockery outdoors! 

A Cat Struggling to Breathe

This one is a very common emergency. Your 9 year old cat is struggling to breathe and looks quite unwell. You head down to the vets and they too are quite concerned. They recommend an ultrasound scan to identify the cause.

Ultrasound is perfect for emergency cases such as these. This cat is too sick to sedate for an X-ray but will happily sit for a quick ultrasound. A fast ultrasound scan reveals that there is fluid on the lungs – the vets drain this and your cat starts to feel much better. A repeated ultrasound scan shows your cat has an enlarged heart that has been contributing to fluid build-up! Luckily this can be treated, so your cat is sent home with medication. Ultrasound quickly found the problem and directed emergency treatment.

Your vet has asked that you come back in a month’s time to monitor the heart. Ultrasound again is perfect for this – with your cat sitting quietly, the heart and lungs are scanned again to see if there is any more fluid or if the heart has changed shape. Luckily the drugs appear to be working, but they’d like to scan again next month. Ultrasound was used to monitor disease progression and the response to treatment.

A Cat that’s Slowing Down

It’s a few years later and your cat has been well managed on heart medication and regular ultrasound scans to see how the disease is progressing. However, in the last few months your cat has started to slow down and is very quiet. Worried, you bring him into the vets. Naturally, they check the heart and lungs via ultrasound again – the heart is fine and there is no fluid but they notice the lungs are looking a little strange. Ultrasound has been used to rule out fluid build-up again and direct the next step.

An X-ray is the next step, performed under a careful sedation. Unfortunately, the X-rays show the lungs are full of little nodules that the vets think is most likely cancer. Another X-ray shows a primary mass in your cat’s liver. X-rays have successfully diagnosed the disease. These kinds of situations are horrible, but today they decide to regularly check your cat to decide when it is time to say goodbye. This involves regular X-rays to see how the cancer is growing. X-rays are used to monitor disease progression.

A dog behaving strangely

You’ve noticed your young dog is behaving strangely: falling over, dragging his back legs, having trouble with toileting and being a little snappy. At the vets, they determine your dog has some neurological difficulties and back pain. He had an accident and fell off the chair last night, so your vets are concerned there may be some damage to the spine. Investigating issues with the brain and spine is complex and often requires advanced imaging like CT and MRI. These are expensive, however. We will split this scenario into two here.

If money is an issue, your vet can offer an X-ray first to rule out what we are most worried about – a fracture of the spine. As you know, X-rays are perfect for looking at bones, and this X-ray shows no damage to the spine. Although the vets do not yet know the exact cause, we have ruled out a serious one. X-ray has been used to rule out disease. Your vet starts a trial treatment of rest and pain relief which seems to do the trick. You never found out the cause but your dog is doing much better regardless. It is important to remember that vets don’t always get the answer but that doesn’t mean we can’t help your pet.

If instead you have insurance for your dog, your vet recommends referral to a specialist hospital. Neurological issues are usually investigated with CT and MRI. CT is used to look at the detail of bones within the skull and spine while MRI can look at the spinal cord itself. The CT shows that your dog has a prolapsed disc in his back and MRI associated damage to the spinal cord. Using the CT and MRI images, the hospital elects for surgery to remove the prolapsed disc. This means that the problem won’t flare up again in the future. CT and MRI diagnosed the disease and directed treatment. 

Paralysed Dog

This is another common emergency. Your dog got off his lead and ran into the road just as a car was passing. Sadly, they got hit by the car. You speed off to the vets and they take him out the back to check him over. This sort of case involves multiple forms of imaging.

After car accidents, the most important first step is to identify any internal bleeding, organ rupture or lung damage. Ultrasound is key here – it is quickly used to scan the lungs, heart and abdomen, and shows no internal damage. Ultrasound has ruled out critical emergency symptoms. Thanks to ultrasound, your vets know your dog is not critically injured. They do notice your dog has a damaged leg and are concerned it is broken. They sedate and X-ray your dog to confirm their suspicions – there is a broken leg. X-rays have diagnosed a problem.

After reassuring you that your dog won’t die today, they recommend surgery to repair the broken leg. This requires specialist orthopaedic surgery. Their surgeon will need multiple views of the broken leg so they know exactly how to operate. X-ray has been used to direct treatment. Afterwards the surgery, they X-ray the leg again to check the surgeon did a good job. We ask to perform one more X-ray exam a week later to check the orthopaedic implants are healing nicely. X-ray is used to monitor the response to treatment.

In Conclusion

We hope that the above five scenarios were useful. These sorts of cases are seen almost every day at veterinary practices and are hopefully a good indicator of what diagnostic imaging is used for. To recap, we can use imaging to rule in or out diseases, identify a specific disease, direct treatment or even be used for treatment, monitor the response to treatment and monitor disease progression. 

We hope that you also noticed the logical approach our fictional vets took – they did not jump to conclusions but used imaging to direct their next step. One technique ruled out some diseases which directed them to the next imaging technique. As an owner, it may therefore seem like we spend money on X-rays and other diagnostic imaging techniques for no reason but it is always for a purpose. Remember that finding nothing is not a bad outcome – finding nothing rules out many other diseases and helps us narrow our search. And even if we can never find a definitive answer for why your pet is sick, by using imaging to rule out other causes, we can treat the most likely cause.

Diagnostic imaging is one of the most powerful tools in a vet’s arsenal, and without it many diseases would become impossible to manage. If you are ever unsure why your vet is asking to spend your money to perform diagnostic imaging, simply ask – we are sure they will be able to explain why it’s necessary to get your pet back on their feet.

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