Category: veterinary procedures

Samples and tests – how they help your vet

Laboratory tests are used by vets to help them diagnose disease in animals that are ill. Increasingly, they are also used as part of a routine health check to detect hidden disease before the development of obvious symptoms. This allows your dog to be treated earlier and more effectively. A very important use is to test that your dog’s kidneys and liver are working properly before a surgical operation.

Many veterinary practices have their own small laboratory where a limited range of tests can be carried out. Results are obtained quickly which allows rapid decisions on treatment. Often a quick test is carried out in the practice and a sample is then sent to the commercial laboratory to check that the results tally.

If a broader range of tests is required, samples will be sent to a commercial laboratory which will usually send results of routine tests back to your vet by fax, telephone or e-mail within 24 hours (although some tests may take 10 days or longer to complete). Commercial laboratories are able to advise your vet on how to interpret difficult test results.

Occasionally, especially if samples are delayed in the post, they may deteriorate and your vet may need to repeat the test.

There are a whole battery of tests which can be done on different types of samples, although not all are used to investigate every disease. Some samples are more easy to obtain than others and the effects that testing has on your dog will vary.

These are the most commonly performed laboratory tests because suitable samples are usually easy to get. It is possible to tell a great deal about your dog’s health or disease from the concentration of different chemicals in the blood. The proportion of different types of blood cells and the presence of proteins called antibodies (which are produced as part of the body’s defence against disease), may tell your vet how well your pet is fighting the disease.

Samples are usually taken from a vein in the leg or neck using a hypodermic needle and syringe. A patch of fur over the vein is shaved and the skin disinfected with surgical alcohol to clean the skin and allow your vet to see the vein more easily. A few millilitres (about a teaspoon) of blood are put into special containers to prevent it clotting.

Blood sampling is not painful although some animals don’t like being held whilst the sample is taken. Some bruising may occur if your dog has delicate skin or struggles when the sample is being taken. The puncture hole will heal quickly unless your dog has a disorder that prevents the blood clotting.

Blood tests can show if your dog is anaemic or show whether its liver and kidneys are working properly.

These are carried out to check for diseases such as diabetes or cystitis. Urine can be checked to see if it contains proteins, sugar or signs of infection.

Urine samples can be collected by catching a few drops of urine in a thoroughly cleaned container under your dog as it empties its bladder. The sample should be kept in a sealed bottle inside a refrigerator and tested as soon as possible.

When it is not possible to wait for a naturally produced urine sample, your vet may collect one using a catheter (a special tube), passed directly into the bladder through the urethra, or using a needle inserted into the bladder through the skin over the belly. It might be possible to collect samples in this way without sedating your dog and these techniques are no more complicated or dangerous than taking a blood sample.

Small samples of faeces often help to identify diseases of the digestive system. The sample may be tested to see if any unusual bacteria are growing that indicate an infection in the intestines. Further tests may be carried out to see if your dog is unable to digest certain foods or if its faeces contain eggs from parasitic worms.

A dog’s eyes, ears and nose or skin can often become infected with disease-causing bacteria, viruses or fungi. Swabs are taken by gently rubbing the affected area with a small piece of cotton wool. The swab is then either transferred onto a glass slide for examination under a microscope or cultured and tested to see if bacteria can be grown. The results of a culture test may take a few weeks or longer, (in the case of some slow growing bugs).

Dogs with skin disease will be tested to see if they are infected with parasitic mites. The skin is scraped gently with the edge of a scalpel blade until bleeding occurs. This may cause minor discomfort to some dogs although others tolerate it fairly well. There are usually only small numbers of mites and a large number of scrapings may have to be taken from several areas before finding them. The skin sample is transferred onto a glass slide and examined under a microsope.

If a dog has a growth on its body it is normal to take a tissue biopsy. This involves removing a small part of the lump which is then examined under a microscope to see what sort of cells it contains. Cell samples may also be collected by putting a needle into the lump and sucking out some cells.

Fluid samples may be taken from the airways via a tube placed in the throat, or the digestive system via an endoscope passed into the stomach. In this way your vet can obtain more information without performing a full operation on your dog.

With many diseases it is not possible for your vet to come up with an instant diagnosis. Your animal may have to undergo a number of tests so that the vet can rule out possible causes of the illness. While some diseases can be confirmed using a single test, others will need a large number (profile) or a sequence of tests on one or more tissues or body fluids. There are occasions when repeat tests may be needed to be taken over a period of time, eg looking for changes in antibody levels in the blood over several weeks.

Your vet may need to perform diagnostic tests on your dog, or on samples from your dog, to help provide the best possible care for your pet. If you are unsure what a test involves or why your vet needs to do it, please ask for a more detailed explanation.

Scanning – the inside picture

The term ‘scan’ is often used to describe the method of obtaining an image of the inside of the body. This may be done with ultrasound (details of which can be found in a separate factsheet), which is often available in veterinary practices and may be performed at your vet’s surgery. Recently, more specialised scans (MRI and CAT scans) have become widely available for pets – however it is likely that your pet would need to travel to a specialist centre for one of these scans.

MRI stands for Magnetic Resonance Imaging and is a type of scan that uses a magnetic field to make a picture of the inside of the body. The area to be scanned is put inside a large magnet and radiowaves are passed through the body. This causes the atoms inside the body to vibrate and give out a signal in reply. These signals are detected by a radio antennae.

Body tissues contain different amounts of water and other components and so different tissue produce different signals. A computer puts this information together to make a picture of the separate organs in the body. MRI is particularly good for detecting changes in the brain and the soft tissues of the body (muscle, fat and internal organs) which cannot be seen well with any other form of imaging.

CT (Computed Tomography) or ‘CAT’ scanning is an advanced form of x-rays. In a normal x-ray the patient is placed under the x-ray machine and a beam of x-rays passes through the body onto a photographic plate from which a picture of the inside of the body is produced. In a CT scan the patient lies on a table and the x-ray machine moves around the body as the x-rays are produced.

The information from the x-ray beam is taken into a computer that creates an image of the inside of the body. The detail of the picture produced by a CT scan is much higher than that of ordinary radiographs and a cross sectional (like looking at thin slice of the body), or three-dimensional, image can be generated. CT images are particularly good for looking at changes in the bone and lungs.

It is quite expensive to have a pet scanned and your vet will not recommend the procedure unless they think it is likely to give important new information that may help in the treatment of your pet. Sometimes the information provided by clinical examination, x-rays, and blood tests will lead your vet to suspect a problem with a particular organ (such as the brain). There may be no way to get more information about this without performing a scan.

In other cases detailed information, for example about the extent of a cancer, may be needed in order to provide the best treatment. If you are worried about your pet having a scan then discuss your concerns with your vet and they will tell you if there is any other option.

It is essential that your pet does not move during the scan and so they will be given a short anaesthetic. As your pet will be having an anaesthetic your vet will ask you not to feed your pet the evening before the day of the scan.

The magnet in an MRI scanner is very powerful and will attract some metals from several feet away. This means that no metal objects are allowed in the scanning room – your pet’s collar will be removed before the scan and people (or pets) with heart pacemakers or some other metal implants are not allowed in the scanning room.

Every scan takes several minutes to complete, and it may be necessary to make many different scans for each examination. It is essential that your pet remains still throughout the whole scan (or the image will be blurred) so your pet will need some kind of anaesthetic. Modern anaesthetics are very safe and your pet will probably recover more rapidly from an anaesthetic than any form of sedation.

As these scans are usually performed at specialist centres it is likely that your pet’s anaesthetic will be monitored by a vet with a special interest in anaesthesia and the anaesthetic will be very safe. You will usually be able to take your pet home as soon as they have recovered from the anaesthetic unless they are receiving further treatment. In specialist centres the vets will often want to perform the scan and then go straight to the operating theatre (if surgery is needed) because this means your pet only has to have one anaesthetic.

The scan will provide your vet with detailed information about the area they are concerned about. Remember that scans only look at a small area (they do not include the whole body), so it is important your vet already knows where to look for the problem.

As your vet is unlikely to be doing these more specialist tests every day the pictures will probably be checked by another vet who specialises in reading films from scans. They will produce a report stating what the pictures show and your vet can use this information to plan further tests or treatment. Sometimes the scans will show no abnormalities in the area examined – this may be very useful information as it can help your vet rule out some serious conditions. In a pet that is having fits (seizures) your vet might want to perform a scan to rule out diseases such as cancer in the brain.

There are no known risks associated with MRI scans (aside from the risks associated with the anaesthetic). CT scans use x-rays and repeated exposure to x-rays can be dangerous – however the risks from routine medical scans are minimal.

You will probably be asked to take your pet to the scanning centre in advance of the time of your examination. The vets at the centre will want to examine your pet and prepare them for the anaesthetic. Your pet will be asleep during the scan and will not know whether you are with them or not. As soon as the scan is complete your pet will start to come round from the anaesthetic – they will be watched closely by trained staff until fully recovered. Once your pet is fully recovered from the anaesthetic you will be able to see them again, and they should be able to return home shortly after.

X-rays and ultrasound

Veterinary medicine has made many advances in the last 10 years and many local veterinary practices are now able to perform x-ray and ultrasound examinations.

Your vet can get a lot of information about what might be wrong with your dog from talking to you and examining your pet. Sometimes your vet may need to take a blood sample to test for diseases. X-ray and ultrasound allow your vet to look at the organs and bones inside your pet’s body without having to perform an operation.

X-rays are like light except they can travel through the body. For an x-ray your dog will lie under the x-ray machine which sends a beam of x-rays through your dog’s body onto a photographic plate (like a piece of film). When the plate is developed your vet will have a picture of the inside of your pet. This is called a radiograph.

Veterinary ultrasound machines are just like the ones used by human doctors to scan babies in the womb. As its name suggests, ultrasound is a form of sound. Just as sound waves can pass through solid objects (like doors and walls when your neighbour has a party!), ultrasound can pass through the skin into your dog’s body.

The sound waves are directed through the area your vet wants to look at and some of them are reflected back like an echo. These echoes are detected by a special computer that uses them to produce a map of the inside of your pet that your vet can read.

No, it is not possible to feel x-rays or ultrasound. For ultrasound examinations, fur will need to be shaved over the area where your vet is taking the picture. The ultrasound machine must be in contact with skin to let the sound waves get into the body. The hair should grow back quickly after the examination.

Taking an x-ray is a bit like taking a photograph of the inside of your dog. For x-ray examinations it is important that your dog lies still as the exposure is made or the final picture will be blurred. Nurses and vets take many x-rays every day and so they cannot hold all the patients or they would also be exposed to the x-rays which can be dangerous over a long period of time.

Ultrasound examinations can take up to an hour to perform. Although your pet can be held by a nurse while the vet performs the examination, many dogs do not like to be held still for this length of time. Giving them a sedative makes them relax so that they are not worried by the examination.

X-rays, when used to produce pictures of your pet, will not cause side effects. Exposure to high doses, or over long periods of time, can be dangerous and this is why your vet cannot hold your dog for the examination.

There is no evidence that ultrasound examinations carry any risk at all.

The risk associated with the tests is that of upsetting a sick dog or one with breathing difficulties by struggling with it, or the risk of the anaesthetic or sedation in an ill animal. Your vet will explain the risks to you and if you are in any doubt about the risks please ask your vet to explain why they need to do the tests. In almost all cases the risk of not finding out what is wrong with your pet (and therefore not being able to treat it) is far worse than the risk of the anaesthetic.

Although your vet will be able to get the pictures from these examinations on the same day, they may want to send them to a specialist for a second opinion before giving you a final diagnosis. Some vets specialise only in reading x-rays and ultrasounds and may be less likely to miss some information on the pictures. Some veterinary practices now have a specialist in the practice or one who visits the practice regularly to perform these examinations.

Your vet will be happy to explain to you why they need to do tests on your pet. If you do not understand the reasons please ask someone to explain the tests to you. If you are interested, your vet will probably be able to show you the pictures of your pet after the examination and explain what they can see.

Endoscopy – the inside story

Sometimes it can be really helpful to look inside an animal to see what is going on. There are many ways of examining the insides of an animal: blood tests, imaging techniques (like X-ray and ultrasound) and sometimes it is necessary to operate to find out what is going on. Endoscopy is an alternative to some forms of surgery. Endoscopy is increasingly being performed in general practice and your vet may suggest it for your pet if it has a breathing problem or bowel trouble.

Endoscopy is the term used to describe the method of obtaining an image of the inside of the body by placing a special tube (endoscope) inside the body. There are 2 kinds of endoscope:

  • rigid endoscope is a small tube like a telescope. These are used by vets for looking inside joints, the bladder, nose and body cavities (and can even be used to perform keyhole surgery).
  • flexible endoscope is often used for looking into the stomach but can also be put into the airways and down into the lungs. The advantage of a flexible endoscope is that it can be steered around corners. Flexible endoscopes are extremely useful for viewing the inside of the stomach and bowel where the endoscope has to pass a long distance into the body.

Using either type of scope a magnified image can be projected onto a screen. A long pair of forceps can be passed along the scope so that samples can be collected from areas deep within the body.

Endoscopy is most commonly used in animals with bowel problems, especially chronic diarrhoea, in dogs that are coughing and with asthma. It is quite expensive to have endoscopy and your pet will have to have an anaesthetic so your vet will not recommend the procedure unless they think it is likely to give important new information that may help in the treatment of your pet.

Sometimes the information provided by clinical examination, X-rays, and blood tests will lead your vet to suspect a problem in a particular area (such as the bowel). There may be no way to get more information about this without performing an operation or endoscopy.

In other cases, your vet may need to take samples for further tests and endoscopy may allow these samples to be collected without your pet having an operation. If you are worried about your pet having endoscopy then discuss your concerns with your vet and they will tell you if there is any other option.

It is essential that your pet does not move during endoscopy and so they will be given a short anaesthetic. In preparation for all anaesthetics your vet will ask you not to feed your pet after the evening before the day of the investigation. If your pet is having an examination of its large bowel (colon) your vet may need to give it an enema, to clean out the bowel, before the examination.

It is essential that your pet remains still throughout the whole investigation as they may damage themselves or the expensive equipment if they struggle during the procedure. Modern anaesthetics are very safe and your pet will probably recover more rapidly from an anaesthetic than from any type of sedation.

Endoscopy will provide your vet with more detailed information about the area of concern. Using an endoscope your vet may be able to collect samples from deep within the lungs or the bowel and these samples can be sent to a laboratory to get more information about your pets condition or the best treatment.

There are few risks associated with endoscopy (aside from the risks associated with anaesthesia). Sometimes the disease your pet has will increase the risk of an anaesthetic, but the only alternative to endoscopy may be an operation which also requires an anaesthetic (and usually has other risks too). If you are concerned ask your vet to explain all the potential risks of the procedure and to discuss any alternatives with you.

You will usually be able to take your pet home as soon as they have recovered from the anaesthetic, unless they are receiving further treatment. They should not require any special treatment after endoscopy. After the anaesthetic has worn off they should be back to how they were before the procedure.

Sometimes pets will cough more than usual for a day or so after (if they have had a tube placed in their throat). If your pet seems uncomfortable or is off their food after the procedure be sure to let your vet know.

In most cases endoscopy offers a safe form of investigation that may give your vet vital information to help treat your pet more effectively. The risks and complications of the procedure are minimal and this modern investigation allows your vet to offer better options for managing your pet.