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Kidney disease in cats
Diagnosis Of And Screening For Kidney Failure In Cats

Up to 75% of a cat's kidney function can be lost before it shows any outward signs of ill health. Inside the body, though, it's a different story. Earlier stages of kidney failure produce a change in the composition of your pet's blood and urine, which can be picked up with simple screening tests by your veterinary surgeon. That's important, because it's vital to catch the problem quickly if your cat is to stand the best chance of a longer, healthier life.
 

The question is, which screening and diagnostic tests should be carried out, and when?

Regular physical exam
Recommended for all cats over 7 years of age

A basic annual physical examination of your cat by a vet is simple, quick, non-invasive and can be carried out at low cost. What's more, it'll give your vet the best chance of diagnosing many other conditions early - not just kidney failure. Cats of any age will benefit from an annual healthcheck, but they become increasingly important in middle to old age, and are recommended for all cats over seven years of age.
 

A physical examination to check for early signs of kidney failure should ideally include:
 

  • A weight check, as weight loss can be an early indicator of many diseases - including kidney failure.
  • A general physical examination, which provides information on whether or not the cat is dehydrated, anaemic, whether the kidneys feel abnormal (e.g. enlarged due to polycystic kidney disease), or whether there are problems caused by other diseases.
  • Blood pressure measurement, as high blood pressure is a common consequence of kidney failure in cats.
  • An examination of the eyes to check for any damage caused by high blood pressure.
  • A urine test. Cats normally produce concentrated urine (they evolved as desert-living creatures); dilute urine can be an early sign of kidney disease. Urine can be collected from your cat at home using non-absorbant litter provided by your vet. Alternatively urine can be collected via a procedure called cystocentesis (where urine is sampled using a needle inserted into the bladder).

It is also worth pointing out that even if urine and blood pressure checks reveal nothing untoward, they are still a useful exercise. They help to establish normal readings for your cat, against which your vet can compare the results of future tests.

Blood tests
Recommended when a physical exam indicates the possibility of kidney failure

Once two thirds to three quarters of renal function is lost, the kidney becomes less effective at excreting waste products produced by the body as it breaks down protein. Consequently, these waste products build up in the bloodstream, a condition known as azotaemia. In combination with the results of a urine test, vets can confirm a diagnosis of kidney failure by analysing blood for increased levels of two waste products: urea and creatinine.
 

Again, worth noting that azotaemia can be seen for reasons other than kidney failure. Common examples would include dehydration or analysis of a blood sample collected within a few hours of eating a meal. These need to be considered and eliminated as possible causes before a diagnosis of kidney failure is made.
 

Although blood tests are usually slightly more expensive than the tests carried out during a basic exam (such as urinalysis), they are nevertheless a routine and straightforward procedure. A small amount of blood is taken from the cat, and the sample usually sent to a laboratory for analysis.

Advanced Diagnostics

In some cases, further tests may need to be carried out in order to pinpoint the cause of kidney failure. They include:

  • Renal Ultrasound
    Ultrasound equipment is sometimes used to scan the kidney for the presence of diseases such as polycystic kidney disease. This is a relatively straightforward and non-invasive procedure. However, ultrasound equipment is not available in all practices, so the procedure may require referral to a specialist vet.
  • Renal Biopsy
    Biopsy of the kidney is not required in the majority of renal disease patients. Kidney biopsy is a specialist procedure and is usually performed in patients where cancer (e.g. lymphoma) or other rare causes of renal disease (e.g. glomerulonephritis, amyloidosis) are suspected. The procedure involves taking a sample of suspect tissue from the kidney whilst the animal is under a general anaesthetic, and sending it for laboratory analysis.
Other Novartis UK Petcare Websites

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www.heartydog.co.uk
Treating heart disease in dogs.

www.wormfree.co.uk
Treating worms in cats and dogs.

www.fleafree.co.uk
Controlling fleas.

Blood Pressure
Measure blood pressure

High blood pressure is a common consequence of kidney failure in cats - it's easy for your vet to check.

Urine Test
A urine test will help detect signs of kidney failure

A simple urine test can help detect the signs of kidney failure early. Urine can be collected at home using non-absorbant litter provided by your vet.

Cystocentesis
A urine test will help detect signs of kidney failure

Your vet can also take a urine sample from your cat using a technique called cystocentesis, a procedure in which urine is withdrawn directly from the bladder using a needle and syringe.

Feline Advisory Bureau
Feline Advisory Bureau

The Feline Advisory Bureau is a charity "dedicated to promoting the health and welfare of cats through improved feline knowledge, to help us all care better for cats". It has an excellent and comprehensive website for cat owners.

Visit the FAB website
Normal ultrasound scan
Cats with kidney failure should always have free access to a fresh supply of water

An ultrasound kidney scan is sometimes taken to detect diseases such as polycystic kidney disease.