Introduction

It is highly unlikely that you could have prevented your cat developing CRF; so please don't feel guilty. As discussed in What is CRF?, it is normally not possible to detect CRF until the cat has already lost 66-75% of his or her kidney function. However, the following are some areas of investigation into ways in which earlier detection may be possible. It is not currently possible to prevent CRF; but the earlier it is diagnosed, the better your chances of helping your cat.

Assessment of renal function: what can be done in practice (2002) is a very interesting paper about the various methods of detecting CRF presented to the World Small Animal Veterinary Association Congress 2002 by Dr Jonathan Elliott.

Annual Bloodwork

Although occasionally younger cats get CRF, it tends to be a disease of the older cat. I now make it a rule to have bloodwork run once a year for all my cats over the age of eight. Once cats reach the age of ten or twelve, you might want to consider checks every six months.

I would also recommend weighing your cat regularly in order to spot any weight loss early, which may indicate CRF or other health problems such as hyperactive thyroid.

The American Association of Feline Practitioners provides guidelines on how to be proactive in caring for a senior cat. It recommends (page 3) that blood tests, urinalysis and a blood pressure check should be performed every year in cats starting between the ages of 7 and 11 with no clinical signs of disease.

Cornell University College of Veterinary Medicine has information on what to expect as a cat ages.

Antech Diagnostics discusses the results of a study at a Los Angeles veterinary hospital into the benefits of bloodwork and other tests performed in cats over the age of 7 who were apparently healthy.

Urine Specific Gravity

Measuring the urine specific gravity may indicate loss of concentrating ability before anything shows in bloodwork. However, a cat may have dilute urine for other reasons, such as diabetes, so this is only a guide, not a definitive method of diagnosis.

Proteinuria

In New news for feline chronic renal failure (2004) Elliott J Waltham Feline Medical Symposium presented to the 2004 North American Veterinary Conference, Dr Jonathan Elliott discusses the importance of protein in the urine as a risk factor for the development of CRF. He states that the urine protein:creatinine ratio should be calculated: <0.5 is non-proteinuric; between 0.5 and 1.0 is borderline proteinuric; and over 1.0 is proteinuric. If you know your cat has proteinuria early on, you can take steps to control it (see What Do All Those Test Results Mean?).

Survival of cats with naturally occurring chronic renal failure is related to severity of proteinuria (2006) Syme HM, Markwell PJ, Pfeiffer D & Elliott J Journal of Veterinary Internal Medicine 20 pp528–535 confirms the results of the earlier study above.

Assessment and management of proteinuria in dogs and cats: 2004 ACVIM Forum Consensus Statement (Small Animal) (2004) Lees GE, Brown SA, Elliott J, Grauer GF & Vaden SL Journal of Veterinary Internal Medicine 19 pp377-385 gives suggestions for the diagnosis and treatment of proteinuria.

Proteinuria and renal disease: a round table discussion (2005) is an interesting discussion by a number of veterinary specialists about proteinuria, and CRF generally.

Idexx Laboratories is now offering a new test in a number of different countries which can calculate the protein:creatinine ratio.

The E.R.D.-Screen Urine Test below relies on the detection of protein in the cat's urine. However, it should be noted that protein in the urine may have causes other than CRF. There is more information about proteinuria on the What Do All Those Test Results Mean? page.

E.R.D.-Screen Urine Test

This is a relatively new test (introduced in the USA and Canada in August 2003, and also now available in Europe and other parts of the world) for detecting renal failure in its early stages. The test works by detecting low levels of protein (microalbuminuria) in the cat's urine, and its manufacturers claim that the test is able to detect cats at risk of renal failure at a much earlier stage than other tests, i.e. when there is as little as 25% damage, compared to the minimum 65% damage that occurs before anything shows up in bloodwork.

The test is only available through your vet, who has to run the test in-house. If your vet does not have any in stock and you are in Europe, s/he can contact Heska's European distributors, Woodley Equipment Company. to obtain the test. Heska also has a list on its website of its distributors in other parts of the world.

In the USA it should not cost more than US$20-30 if performed in addition to other tests (Antech charges much less, see below); it may cost slightly more if run in isolation. Unfortunately, it appears to be much more expensive in Europe, costing up to €200, though many vets will charge less.

The test is non-invasive, requiring only a urine sample, with results available in less than five minutes. False positives are possible if certain inflammatory diseases such as IBD or dental disease are also present, or if the cat has certain other conditions such as diabetes or hyperthyroidism. Personally, I plan to ask for this test to be run annually for any of my cats who are eight years of age or over.

The E.R.D.-Screen Urine Test provides detailed information on the new test and the trials by its manufacturers.

Antech Diagnostics in the USA offers the E.R.D.-Screen Urine Test for only an additional US$5.95 when a urinalysis is performed.

Glomerular Filtration Rate

Measuring the Glomerular Filtration Rate (see What is CRF?) can be a useful tool, and in fact, according to Dr Jonathan Elliott in New news for feline chronic renal failure (2004) Elliott J Waltham Feline Medical Symposium presented to the 2004 North American Veterinary Conference, the International Renal Insufficiency Society believes that eventually GFR will be the measure by which CRF can be categorised, although it will take some time to determine appropriate reference ranges.

Iohexol Clearance Test

This test uses iohexol, an iodinated radiographic contrast medium. Basically, the test measures how long it takes the kidneys to clear a measured amount of iohexol from the kidneys, and this is then used to calculate the GFR. This test, sometimes referred to as the Plasma Iohexol Clearance test (PIC) is highly specialised and only available at a limited number of places in USA such as the Animal Health Diagnostic Laboratory at Michigan State University; I am not aware that the test is commercially available in Europe. This test may be particularly helpful  before opting for one of the more permanent methods of treating a hyperactive thyroid (see Related Diseases).

Michigan State University Diagnostic Center for Population and Animal Health has more information on this test (Volume 14 (1997) Number 3).

Inulin Clearance Test

Like the iohexol clearance test, the inulin clearance test measures how long it takes the kidneys to clear a measured amount of a particular substance, in this case inulin. This test only requires a single IV injection of inulin, followed by the taking of a blood sample three hours later. The test is already commercially available in Germany. This test may be particularly helpful  before opting for one of the more permanent methods of treating a hyperactive thyroid (see Related Diseases).

Single-injection inulin clearance for routine measurement of glomerular filtration rate in cats (2003) Haller M, Rohner K, Muller W, Reutter F, Binder H, Estelberger W, Arnold P Journal of Feline Medicine & Surgery 5 (3) pp175-81 compared the inulin test to the iohexol clearance test and concluded that "the inulin clearance test is a valuable tool for the assessment of renal function in daily practice".

Antech Diagnostics briefly mention this test (end of page).

Alomed in Germany is offering this test.

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