TANYA'S

COMPREHENSIVE GUIDE TO

FELINE CHRONIC KIDNEY DISEASE

 

 

DIAGNOSIS: URINALYSIS (URINE TESTS)

 

ON THIS PAGE:


What is Urinalysis?


Obtaining the Urine Sample


The Various Tests:


Urine Specific Gravity (USG)


Osmolality


Blood in Urine (Haematuria)


Proteinuria


Urine Protein:Creatinine Ratio


Urine pH


Glucose


Urinary Tract Infections & Pyelonephritis (Kidney Infections)


Research Participation Opportunity: Urine Culture Study


 

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Home > Diagnosis > Urinalysis

 


Overview


  • There are a number of tests which can be run on a urine sample. Collectively these tests are known as urinalysis.

  • The USG test can help with the diagnosis of CKD, and may be useful for detecting early CKD before it begins to show in blood tests.

  • The UP:C (urine protein to creatinine ratio) test can give some idea of the severity of the CKD.

  • Urine tests are also very important for helping to diagnose kidney and urinary tract infections.


What is Urinalysis?                                                                                             Back to Page Index


 

Urinalysis is the term used to refer to a series of tests run on a urine sample. These tests can help to confirm the CKD diagnosis, or may give an early warning. They are also used to check for imbalances and infections.

 

Pet Education gives an overview of urinalysis.

Pet Place discusses urinalysis (no need to register, just click on Close at the bottom of the irritating pop-up).

Diagnostic caveats for difficult bacterial urinary tract infections (2005) Osborne CA DVM News Magazine discusses UTIs and includes a table (Table 7) which shows what the levels of bacteria found in a urine sample obtained by various methods probably indicate.

The Merck Veterinary Manual has information about urinalysis.

Cornell University College of Veterinary Medicine explains more about urinalysis.

Irving Crowley is a human site but has some very detailed information.

The University of Georgia College of Veterinary Medicine (2003) Sine CS, Krimer P, Bain PJ & Latimer KS has information on urinalysis dipstick interpretation.

Urinalysis and Urine Sediment (2004) is a presentation by Dr MM Christopher to the World Small Animal Veterinary Association World Congress.

Urinalysis: performing an accurate urine sediment analysis (2009) is an article by Dr JP Lulich about urinalysis.

 


Obtaining Urine Samples                                                                                 Back to Page Index


 

Urine samples may be obtained in a number of ways. Some methods (free catch and non-absorbent litter) can be used at home so you can then take the sample to your vet for testing. Samples obtained in this way are sufficient to run most of the tests below, but are not sterile, so are not suitable for running a culture and sensitivity test (see below). In this situation, ideally you need to take your cat to your vet for cystocentesis.

 

If you do obtain a sample at home, ideally you want to take it to the vet within four hours.

 

Feline Good has photos of urine collection via the Nosorb and cystocentesis methods.

 

Free Catch


Free catch means that you stick a container under your cat as s/he urinates and catch some urine in it. I can't imagine my cats tolerating this but some people's cats don't mind, in which case it is probably the quickest and easiest way.

 

Rocket GP Surgery Supplies sell a sterile urine catcher called a Uripot which costs £25.95 for 50.

 

My Vet Meds sell a similar product (the Uripet) for £1.67 each.

Some people use a ladle, which is a good idea because you don't need to get too close to your cat.

 

Non-absorbent Litter and Detecting Litter


Nosorb litter is made of non-absorbent granules. You put it in the litter tray in place of normal litter, and since it does not absorb urine, you can scoop up some urine to take to the vet. NoSorb can be washed and re-used.

 

Kit 4 Cat is another type of non-absorbent litter that is apparently very similar to real (sandlike) litter.

 

Katkor is a non-absorbent litter available in a variety of European countries.

 

My vet sells the Smart Cat Urine Test Kit for £2 a packet. My cats like a lot of litter, so I use two bags, but some people do only use one bag. This is a one use only kit.

 

The Pet Check Up is a test that checks for blood in urine, and which may also be used to check for other issues, such as diabetes.

 

Health Meter Cat Litter can detect blood in urine, and also checks urine pH. It is available from Petco, among others. Crystal Clear Pet Products sell it in the UK.

 

Zooplus in Europe sells a detectable litter called Perlinette. I don't know anybody who has used it yet.

 

Although these tests can give you some basic information, e.g. the presence of blood or bacteria, you should take the sample to your vet for proper analysis. The white blood cell reading in the urine test itself is often inaccurate.

 

Cystocentesis


This is the best way to obtain a sterile sample, which is required in order to run a culture and sensitivity test to check for infections. Cystocentesis means the removal of urine from the bladder via a fine needle. It sounds far worse than it is, I've seen this done on my cats and they do not even flinch. It is safe as long as you have a competent vet, who should use ultrasound to guide the needle. It is only suitable for a cat who has urine in the bladder, and is usually not appropriate for a cat who struggles at the vet's.

 

Occasionally cystocentesis can cause blood in the urine. Lab Animal explains more about this.

 

The University of Minnesota College of Veterinary Medicine explains more about how cystocentesis is performed.

Urinary tract infection: how to diagnose and treat correctly (2003) is a presentation by Claudio Brovida to the World Small Animal Veterinary Association World Congress 2003, which explains why cystocentesis is the ideal method of urine collection, but not always possible.

Pet Place describes how cystocentesis is performed (no need to register to read the article, just click on Close at the bottom of the irritating pop-up).

 


The Various Urine Tests                                                                                                       Back to Page Index


 

The urine sample will be used to run a number of different tests, which will provide your vet with a variety of information about various aspects of your cat's health. The tests include:

Urine Specific Gravity (USG)                                                                


The urine specific gravity (USG) test checks whether the cat is concentrating urine appropriately. Because of their desert heritage, in normal circumstances healthy cats have concentrated urine, but CKD cats usually have dilute urine. This test should be run by refractometer - using the dipstick method is rather unreliable.

 

The normal range is 1.008 to 1.060, but a cat with a USG below 1.040 is generally considered to have a problem of some kind, and in a cat with normal bloodwork, it may be an early warning sign that CKD is developing. Most CKD cats have a much lower USG of between 1.008 and 1.012, which is known as isothenuria. Prolonging life and kidney function (2007) a paper presented to the 32nd World Small Animal Veterinary Association Congress by Dr D Chew, explains more about this.

 

Although these numbers have a decimal place after the 1, vets often say the numbers verbally in a different way, so for example, a USG of 1.012 would be referred to as "ten twelve" rather than "one point oh one two."

 

Cats with pyelonephritis (kidney infection) may have a low USG. Cats with diabetes or hyperthyroidism may also have dilute urine, as may cats with FORL (a type of dental problem). Other possible causes of dilute urine include liver disease or use of corticosteroids. A cat's USG level may also change quite a lot over the cause of the day. Before diagnosing CKD, therefore, the test should be run more than once and other causes ruled out.

 

Once a cat is receiving regular fluid therapy, this test can be rather unreliable. 

The International Renal Interest Society has information on the significance of USG in cats.

Cornell University College of Veterinary Medicine has more information about USG and osmolality. 

Azotaemia and urine specific gravity (2008) is a presentation by Dr JE Maddison to the World Small Animal Veterinary Association World Congress.

 

Osmolality                                                        


This is a measure of particles dissolved in solution, and measures the concentration of the urine. It is usually used in conjunction with USG. The approximate normal range for urine osmolality is 270-320.

 

Serum (blood) measurement of osmolality gives some indication of hydration levels - a dehydrated cat will often have high osmolality, while an over-hydrated cat will usually have low levels. High levels may also indicate azotaemia.

 

Cornell University College of Veterinary Medicine has more information about USG and osmolality. 

Rn Ceus is a human nursing site with some information on osmolality.

 

Proteinuria                                                                                     


Healthy cats only have tiny amounts of protein in their urine because their kidneys do not allow the protein to leak through. In CKD cats, this mechanism can be faulty and excess levels of protein in the urine, known as proteinuria (though sometimes referred to as microalbuminuria), may occur. The main proteins which leak through are albumin and globulin. The degree of proteinuria is usually indicated by the number of + signs on the test result, with more + indicating greater severity, so Protein +++ is more severe than Protein +.

 

The existence of proteinuria has recently been determined to be extremely important in the early detection of CKD (see protein:creatinine ratio below), and in fact forms the basis for a new test devised to diagnose kidney disease early in cats.

 

Other causes of proteinuria include diabetes and hypertension. In Management of chronic renal failure: beyond the can, a presentation to the Atlantic Coast Veterinary Conference 2001 (scroll to No. 3), Dr MS Wallace mentions that hypertension may promote proteinuria.

 

If your cat seems to have proteinuria, you should have the test run again in case it is inaccurate. Blood in the urine, for example, can give a false positive.

 

Proteinuria can make weight loss worse, and may also cause other symptoms, such as swelling in the legs, abdomen or face. See Symptoms for more information and Treatments for more information on how to handle it. 

 

Pet Place has a non-technical explanation of proteinuria (no need to register, just click on Close at the bottom of the irritating pop-up).

Assessment and management of proteinuria in dogs and cats: 2004 ACVIM Consensus Statement (Small Animal) (2005) 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.

Antech Diagnostics discusses how to run and interpret tests for proteinuria.

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

Cornell University College of Veterinary Medicine provides some interesting, albeit technical, information on proteinuria in cats.

The importance of proteinuria and microalbuminuria (2006) Scott SA Presentation to the World Small Animal Veterinary Association World Congress, discusses diagnostic methods for proteinuria.

The National Kidney and Urologic Diseases Information Clearing House is a human site with information about proteinuria.

 

Protein:Creatinine Ratio (UPC Ratio)                                                  


The International Renal Interest Society uses protein in the urine as a risk factor for the development of CKD, and as a factor in determining the severity of the CKD:

 

Urine Protein: Creatinine Ratio

Proteinuria Status

Below 0.2

Non Proteinuric (NP)

Between 0.2 and 0.4

Borderline Proteinuric (BP)

Over 0.4

Proteinuric (P)

 

The UPC ratio is often higher if the cat has glomerulonephritis. The reading will not be reliable if there is infection or inflammation in the urine.

 

The International Renal Interest Society has an article about proteinuria by Dr GF Grauer.

Relation of survival time and urinary protein excretion on cats with renal failure and/or hypertension (2004) Syme HM, found that cats with a urine protein:creatinine ratio below 0.5 survived almost three times as long as cats with a urine protein:creatinine ratio of over 0.5. If you know your cat has proteinuria early on, you can take steps to control it. 

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.

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).

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

Assessment and management of proteinuria in dogs and cats: 2004 ACVIM Consensus Statement (Small Animal) (2005) 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 in cats with chronic kidney disease (2008) is a video presentation by Dr CL Langston of the Animal Medical Center in NYC.

When does protein in a urine sample necessitate further patient evaluation and treatment (2007) Polzin D Veterinary Medicine discusses the significance of proteinuria.

 

Blood in Urine (Haematuria)                           


This is usually a sign of a urinary tract infection, or bladder or kidney stones. However, if your vet obtains a urine sample from your cat via cystocentesis (a needle into the bladder), this may sometimes cause blood in the urine.

 

Other possible causes include high blood pressure. or, occasionally, cancer. Ollie had this symptom towards the end, and I think it might have been because of cancer (he had been treated for cancer a couple of years previously).

 

Persistent haematuria and proteinuria due to glomerular disease in related Abyssinian cats (2008) White JD, Norris JM, Bosward KL, Fleay R, Lauer C & Malik R Journal of Feline Medicine & Surgery 10(3) pp219-29 discusses how in Abyssinian cats with haematuria, the cause may be glomerular disease.

 

Sometimes it is not possible to ascertain the cause. There is a condition called "benign renal haematuria" which means there is bleeding from the kidneys but the cause cannot be found. However, this is rare in cats.

 

Severe or ongoing haematuria may cause or worsen anaemia, so you should always take your cat to the vet if you see this symptom.

 

Pet Place has some information about haematuria in cats.

Pet MD explains more about blood in urine.

 

Urine pH                                                                                  


This is a measure of the acidity/alkalinity of urine. A normal level is in the range of 6.0 - 6.5. A cat with a urine pH higher than this (i.e. more alkaline urine) can be at risk of developing struvite crystals, and a cat with urine pH lower than this (i.e. more acidic urine) can be at risk of developing calcium oxalate stones.

 

A more alkaline urine may be a possible sign of infection.

 

Pet Education mentions that normal pH for cats is 6 - 6.5.

 

Glucose                                                                             


Your vet may wish to test for glucose (sugar) in the urine, particularly if your cat has high blood glucose levels, in order to rule out diabetes.

 


Infections: Urinary Tract and Kidney Infections (Pyelonephritis)           Back to Page Index


 

Urinary Tract Infections


Urinary tract infections are relatively common in CKD cats, so your vet may run tests to check for their presence. As mentioned above, cystocentesis is the best way to obtain a urine sample if you want to check for infection. Bacteria may be present, as may blood.

 

A test strip can show if there are bacteria present in your cat's urine, which are indicative of an infection in a clean sample. Your vet may then wish to run a culture and sensitivity test. This means that the laboratory tries to grow the bacteria obtained from the urine sample over a few days (3-4). If they are successful, they then treat each batch with a different antibiotic to ascertain to which antibiotic the bacteria are most sensitive (i.e. which antibiotic is most likely to kill the bacteria). Urine cultures (2002) is a paper from Antech Diagnostics which explains more about urine cultures.

 

Your vet may also wish to run blood tests because infections sometimes show in the white blood cell readings.

 

Even if your cat does not  appear to have an infection, this may be a false result. Urinary tract infections in cats with chronic kidney disease (2013) White JD, Stevenson M, Malik R, Snow D & Norris JM Journal of Feline Medicine & Surgery 15(6) pp459-65 found that 72% of the cats in the study had occult (hidden) UTIs, i.e. a positive urine culture but no clinical signs of infection. One human study, Establishment of a persistent Escherichia coli reservoir during the acute phase of a bladder infection (2001) Mulvey MA, Schilling JD & Hultgren SJ Infection and Immunity 69(7) pp 4572-9, found that in some cases the bacteria that cause urinary tract infections can burrow so deep into the bladder lining that they cannot be detected in the usual tests. In a later (2004) study reported by Science Daily, researchers found that the bacteria commonly involved in UTIs pass through four distinct developmental stages, including a dormant stage in some cases which may help explain why UTIs often recur.

 

Antibiotic sensitivity profiles do not reliably distinguish relapsing or persisting infections in cats wih chronic renal failure and multiple diagnoses of Escherichia coli urinary tract infection (2006) Freitag T, Squires RA, Schmid J, Elliott J & Rycroft AN Journal of Veterinary Internal Medicine 20(2) pp245-9 confirms that UTIs are common in CKD cats, but states that it can be hard to tell if a cat has a new infection or a recurring one.

 

Either way, treatment is essential. Antibiotics should be given for around two weeks. In order to be sure that the bacteria are completely eradicated and the infection completely cured, some vets give CKD cats a prolonged course of antibiotics, for four or five weeks or longer. Cats with a kidney infection should always be given a lengthy course of antibiotics, see below.

 

Infections may sometimes lead to anaemia, which should also improve once the infection has gone.

 

Diagnostic caveats for difficult bacterial urinary tract infections (2005) Osborne CA DVM News Magazine discusses UTIs and includes a table (Table 7) which shows what the levels of bacteria found in a urine sample obtained by various methods probably indicate.

Veterinary Partner has some information about urinary tract infections.

Urinary tract infection (UTI): how to diagnose correctly and treat (2003) is a presentation by Dr C Brovida to the 28th World Congress of the World Small Animal Veterinary Association.

 

Pyelonephritis


Pyelonephritis means a kidney infection. Pyelonephritis usually occurs because a urinary tract infection has risen into the kidneys. In Chronic renal failure (2001) Dr D Polzin states that "infection at one location potentially places the entire urinary tract at risk for infection."

 

Pyelonephritis may be acute or chronic. Cats with acute pyelonephritis will often be obviously ill, e.g. not eating, sensitive to the touch, with a fever. Unfortunately, cats with chronic pyelonephritis may not be obviously ill. One of our cats, Harpsie, was prone to pyelonephritis and he would simply be a little subdued. Fortunately, he also became incontinent every time, so we were able to recognise the problem and get treatment started promptly.

 

It is quite common for nothing to grow in a culture if the cat has pyelonephritis rather than a lower urinary tract infection, particularly if the infection is chronic rather than acute. Some types of bacteria do not grow in a culture. The Merck Veterinary Manual states "A single urine culture can be negative if bacterial numbers are low." Ultrasound may be helpful in diagnosing the existence of pyelonephritis, though this can be of limited value in cats with PKD, whose kidneys already look abnormal. Ultrasound may also help with detecting urinary tract infections, but only if the bladder is full. In both cases you need an experienced operator.

 

Urinary tract infection (UTI): how to diagnose correctly and treat (2003), a presentation by Dr C Brovida to the 28th World Congress of the World Small Animal Veterinary Association mentions that antibiotic treatment should continue for 4-8 weeks in the case of kidney infections. The longer period is necessary because blood flow to the site of most kidney infections is poor, so it can take a while for the antibiotics to reach and kill the bacteria. You should check the urine again 7-14 days after stopping the antibiotic to make sure the infection has completely gone.

 

If your cat has pyelonephritis, the bloodwork may improve once the infection is under control. Infections may sometimes lead to anaemia, which should also improve once the infection has gone.

 

Pet Place explains more about fever in cats.

 

Urine Culture Techniques Study


The Veterinary Teaching Hospital at Colorado State University is seeking volunteers for a study into the diagnosis of pyelonephritis. The study will compare a new urine test to standard tests to see if the new test might more accurately diagnose the infection.

Cats with pyelonephritis or a urinary tract infection are eligible to participate, as are cats with suspected pyelonephritis, but cats who have previously been given antibiotics are not eligible. The laboratory tests required for the study and a kidney ultrasound will be provided free of charge.

If you wish to participate, please call 970-297-5000 and say that you would like to schedule an appointment for Dr Quimby's urine culture techniques study.

 

 

 

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This page last updated: 25 June 2012

Links on this page last checked: 04 April 2012