Assessment of renal function: what can be done in practice (2002) is a very interesting paper about the various methods of detecting CKD presented to the World Small Animal Veterinary Association Congress 2002 by Dr Jonathan Elliott.
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Although occasionally younger cats get CKD, it tends to be a disease of the older cat. I therefore make it a rule to take any of my cats who are over the age of eight to the vet each year for a check up. The check up includes a physical examination and blood tests (including testing for hyperthyroidism) and a blood pressure check. 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 CKD 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 Back to Page Index
Measuring 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 Back to Page Index
The International Renal Interest Society uses protein in the urine as a risk factor for the development of CKD, and as a factor to determine the severity of the CKD.
Evaluation of predictors of the development of azotaemia in cats (2009) Jepson RE, Brodbelt D, Vallance C, Syme HM, Elliott J. Journal of Veterinary Internal Medicine 23(4) pp806-13 reports on a group of older cats who were monitored to see if they developed CKD. The study concludes that "Proteinuria at presentation was significantly associated with development of azotemia although causal association cannot be inferred."
Protein in the urine may have causes other than CKD. There is more information about proteinuria on the Urinalysis page.
If you know your cat has proteinuria early on, you can take steps to control it, see Treatments.
The following tests may be helpful in assessing the presence of proteinuria:
Idexx Laboratories is now offering a new test in a number of different countries which can calculate the protein:creatinine ratio.
How to integrate UPC ratios into your practice and uncover early renal disease is a video presentation about the new Idexx test (this lasts an hour).
The E.R.D.-HealthScreen Urine Test is another test which may assist with detecting CKD in its early stages by detecting low levels of protein (microalbuminuria) in the cat's urine. The manufacturer claims that the test is able to detect cats at risk of CKD 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 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); 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-house in less than five minutes. If the test is positive, further investigations should be performed, e.g. for high blood pressure. The test may also be positive 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.
Drugs has some information about the test.
Glomerular Filtration Rate Back to Page Index
Measuring the Glomerular Filtration Rate (see What Happens in CKD) can be a useful tool, and in fact the International Renal Insufficiency Society states that GFR is the "most accurate measure available for assessment of renal function." IRIS believes that eventually GFR will be the measure by which CKD can be categorised, although it will take some time to determine appropriate reference ranges.
The main problem with measuring GFR is that it is quite cumbersome, which is why few vets are able to do it.
Managing chronic kidney disease: 10 common questions (2012) Brown SA Presentation to the 83rd FVMA Annual Conference discusses more about GFR and the various ways of measuring it.
The following tests may be helpful in assessing GFR:
This test uses iohexol, an iodinated radiographic contrast medium. Basically, the test measures how long it takes 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 hyperthyroidism.
Estimation of glomerular filtration rate via 2- and 4-sample plasma clearance of iohexol and creatinine in clinically normal cats (2009) Heiene R, Reynolds BS, Bexfield NH, Larsen S & Gerritsen RJ American Journal of Veterinary Research 70(2) pp176-85 is a study into determining appropriate reference ranges. It found that the weight of the cat is a factor.
Michigan State University Diagnostic Center for Population and Animal Health has more information on this test (Volume 14 (1997) Number 3).
Current concepts for the management of chronic renal failure in the dog and cat - early diagnosis and supportive care (2005) is a presentation by Dr S Sanderson to the World Small Animal Veterinary Association World Congress which mentions this 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 hyperthyroidism.
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".
Alomed in Germany is offering this test.
This page last updated: 24 June 2012
Links on this page last checked: 27 March 2012